I just finished gathering the big heavy stuff for a 5881 single-ended. It's going in a home-built radio project. I could also build one with a 6AK6. The rest of the radio is solid state for too many reasons. But the audio section is 3 stages of tube amplification, with a 6SN7 mixer that plays the radio on one side and a musical instrument and effects on the other. The radio itself is being built using an old stereo speaker, decorations, and lighting, to simulate a jukebox (tombstone!) radio from way back when. Keeping in with the era it's from, before television, before transistors, before Internet (yes, there was such a time period)... so it will cover as many bands as I can think of.
The 6BQ5 were part of the output of the Grundig tube type reel-to-reel tape players. I also have a stereo tube amp, maybe 2 in storage that uses those as well. The one is just the raw amp with a pre-amp and connectors, the other has the normal volume, bass, treble, and balance controls, it might have come out of a old phono or radio floor console.
I've never met a 22mF cathode bypass cap that I liked. It just seems to muddy things up, while providing no real bottom end. I tend to like between .68 and 2mF, or something around 100mF, depending on the amp and the desired musical application/focus. But maybe that's just me. Still, I'd like to see more experimentation in this area, 22mF is just kind of taken for granted as the go-to value. Really nice looking piece though, no doubt about that. And thanks for hipping us to this tube.
Nice building , clean job and good sound ! Another nice sounding 6V6 tube is the old 6V6G ...........also wonderfull sounding and one of my favorites .
In the old days when I repaired tube TVs I have seen the 6AQ5 used as a vertical output. I have a stack of 6W6's around here I'm thinking of doing something with. Since the filament current is around 3 times👍 that of an L6 I'll have to find a power transformer with a heavy filament winding or use a separate filament transformer. Good design on your amp. 👍
@@skullheadwater9839, interestingly, Voice of Music portable phonographs and reel-to-reels (a favorite of mine for scavenging parts from) typically used single-ended octal output tubes (usually 6V6, occasionally 7591) and not miniature tubes like 6AQ5 or EL84.
The early 70s version of the Fender musicmaster bass amp uses a pair of 6aq5 power tubes...the later version uses 6v6s...you can tell them apart because the early ones don't have a separate on/off switch
6AQ5's are cool tubes, I thought you were going to say something like a tube that was used as a horizontal deflection amp or something which I probably have some of too. I have built around 5 or 6, 6AQ5 amps. They have their own sound and have a really smooth overdrive sound. Nice tube, easy to find and cheap for NOS. Another cool thing is to build with 12V6's using a separate 12v filament XFMR.
Very nice description! The IC caps are a fantastic choice too. I know those grid coupling caps from the phase inverter to the output stage are hiding in a page fold somewhere ;^)
Hah! I knew someone would catch my error in haste, couldn't imagine it would be Mr. Carlson himself. Thank you for yet another lesson in the need for attention to detail 🤣
After the war there was a rush to introduce more compact tubes, and it certainly conserved space in television chassis where the tube count was high. I think it didn't catch on in the guitar amp world because it is was no different than the 6V6 and space was really not important. Certainly the 6V6 was popular in push-pull phonograph amplifiers and perhaps was something that amplifier designers were comfortable with. Perhaps that is a good thing because there are still manufacturers making 6V6, 6L6, EL34 many of these other tube may begin to fall into short supply... not that this tube is uncommon, but more in reference to the tubes that were made in the mid to late 1960s that were a desperate effort for tubes to remain relevant in a solid state world.
I built a little JCM800 with those. They're close on the datasheets but in practice 6V6s are used often with over 400 volts on the plate. It would be interesting to know what a 6AQ5 could really deal with.
I can see that in the sense of the fact it handles more voltage but as an amp builder you are the one who controls that so you can design the power supply to put the ideal voltage for this tube as well. They have a different tone, the sound very smooth compared to a 6V6, I actually prefer them to 6V6's and have built a handful of amps with 6AQ5's. I actually built an amp using all 12volt tubes using 12AQ5's which I want to say I got a sleeve of 5 NOS for $25. It is one of my favorite sounding amps.
6AQ5s were a common tube. While true that they weren’t used in guitar amps, they were everwhere in early tube stereos, radios and audio circuits of tube televisions. The low prices on eBay reflect their ubiquitous nature as they have been hiding out in dusty tube caddies that were, long ago, raided for 12AX7s….
I used the 6aq5 in my last pp build - wonderful sounding tube. I see you used the Hammond 270DAX - that means you have about 367VDC on the plates. That's quite a bit over the data sheet max of 275V. How has tube life been?
367V would be about right if it was solid state rectification, but don't forget the 6CA4 drops about 60V. Plate voltage is right around 305V. That's still in excess of the 250V or 275V shown on 6AQ5 datasheets, but the handful of guitar amps out there run the plates at ~300V no issue.
The 6AQ5 can't dissipate as much heat as a 6V6, it's in a smaller bottle & has a smaller anode. I'd like to see a soak test comparison or testing after 1000 hours of use at high power OP. Still in a practice amp or home use it's absolutely fine.
Hi, try making a Fender Deluxe Reverb, or Princeton Reverb with 420V average plate voltage with 6AQ5 (arc in 10 minutes), I don´t know why you didnt use a current production rectifier ass well. To me 6AQ5 are more like 6BQ5 with an, unusual , for 21th Century , 7 pin base only found in old radios a TV. You could have put 6bq5 in that amp (with 9 ping sockets) and sound almost the same with a little more gain (a BOX like sound). no feedback, only difference is rectifier tube and individual cathode resistor witch changes gain structure and harmonic dist. and different tone stack and PI, a long tail would allow to put the master post PI (also biased cooler than a BOX AC15 witch is nice,). A nice experiment but impractical if you want to build one and need tube stock and reliability as you said there are no current production 6AQ5, for me, the big difference between a 6v6 is max plate voltage. 250V max plate is too low for a guitar amp. I know you can abuse them but not much, 300v top. And they won´t last. Again a nice experiment. You used good iron, that helps. Cheers.
I guess if you are using off the shelf transformers made for a deluxe but, a builder can make whatever he wants. I have built amps out of control transformers that put out 240v, with a bridge you get about 325v before load, you just use a separate 6.3v filament transformer. The cool thing is you can usually get both for less than you pay for one of those "fender" replacement transformers. It just depends on what you want to build vs how much you have to spend. If you are building clones, I suppose it may be the safe option to buy a kit or individual parts made for your clone but every amp I build is a unique entity. I generally do use modified existing concepts for successive stages. For instance, the last amp I built was sort of using the idea of a 5E3 preamp but instead of using a 12ax7 I used two separate tubes a 6SJ7 pentode and a 6SF5 which is an octal triode with 100mu, using the same basic interactive V,V,T, scheme of a 5E3 but then I used a 6SL7 set up as a paraphase inverter into a pair of cathode biased 6V6's. This thing sounds phenomenal, like nothing else. I used the chassis/PT out of a 1954 Revere R2R with a OT from a 59' Conn Organ. It is mounted in an upright 59' Magnavox record player console with a 57' 12" magnavox alnico speaker out of a different console.
@@skullheadwater9839 HI, I put " Fender Deluxe Reverb" not as a brand or specific model, It cuold be any clon with similar circuit, It´s not an unusual one , didn´t mean to put "Fender" in the context of cost or status as vitage or valuable device.
Gray, you do of course realize that if you could formulate a version of the classic Champ with this tube and somehow find inexpensive transformers (maybe possible because of the lower plate voltage or a doubler? that you would be the amp geeks version of Mr Beast with millions of subscribers? Well maybe not millions but I do think you would be a real hero!
The series diodes are protecting the power supply from a shorted rectifier tube. Without those diodes, the filter caps could potentially see very high AC voltage and fail spectacularly! See Robrob's info on "backup" diodes: robrobinette.com/Generic_Tube_Amp_Mods.htm#Protection_Mods
Not only do the diodes add protection for the power transformer and rectifier tube, as described here, but you still get the sag and compression of a rectifier tube when you play hard (a fully solid state power supply would be much stiffer feeling) and it also still gves a gentle time delay of the B+ feed to the tubes and caps at turn-on.
Winfield Thomas build a 5 watt amp out of spare parts. He put both power tubes in the amp a 6v6 and a 6AQ5. He sent it to me. You can only use one tube at a time you would have to pull the other tube out. There wasn't much of a difference at all
How so? It has a DC coupled cathode follower into a tone stack, a master volume into a Cathodyne PI into Push Pull power tubes. A champ is literally two preamp stages into a power tube. This is sort of a mixture of a Brown face Fender deluxe front end with a master vol added into a 5E3 tweed power section with some component values changed.
Hard to get quiet, non -microphonic EF86 these days, and vintage EF86 are expensive; I'd be tempted to use 5879 low-noise pentodes instead (often used as a mic preamp in vintage PA equipment); not super common these days, but available as NOS, and not terribly expensive. Or perhaps even 6AU6 which are common and cheap as chips; you could buy a dozen of them for about 3 bucks each and select the quietest ones. BTW, I have a big Webster PA/paging amp with 4 !!! 5879 inputs, 4 6L6's, and two 5U4's, which is just begging me to build a guitar amp out of it....
The 807 was often used in Williamson amp designs. They're still fairly common and affordable today whereas the 6146A is rare and pricey and perhaps should be saved for use in original early Ampeg SVT bass amps.
@@goodun2974 The 807 is just a 6L6G with a plate cap, (not the GC version.) The 6146A and B versions are a nice powerful compact tube for RF and modulator service, along with the S2001, 6883 and 8298.
@@MrCarlsonsLab , If I remember correctly, the 807 could handle significantly higher plate voltage than a 6L6G, which is why it was favored for use in small RF transmitters (6L6G was rated for only 300 volts). The 6146A and B are very different animals, of course.
@@goodun2974 Yes, the reason the 807 could handle more plate voltage is the plate connection is on the top of the bulb, not in the octal base like the 6L6G. The internal structure between the two is identical.
@@MrCarlsonsLab , Of course, 807 were usually used in class B as transmitters and therefore coul handle even more voltage than you might expect, compared to what they can handle as class AB audio amplifiers.....
I would generally reject the idea that output tubes have an inherent sound. Even if it was true, being able to separate it from difference in circuit design, actual component values vs. marked values, and subjective listening would be impossible. I don't think I do.
@@graybenchelec, In general I would tend to agree with you, but I also had an experience with a Kalamazoo Model One that I had recapped which sounded kind of tame with 3 or 4 other strong-testing American and Japanese 6BQ5's but when I installed a good used European Amperex Bugle Boy EL84 into it, the amp turned into a tiger and sounded very much like a miniature Vox AC30. The difference was staggering! In hindsight I am guessing that the Amperex EL84 was a true pentode with internal suppressor grid, and the American and Japanese tubes I tried were beam power tetrodes, not true pentodes.
Curious, why cite the EL34 and not a 6CA7 but then referred to the EL84 as the 6BQ5? I never hear anyone refer to EL84s by the American 6BQ5 nominclature. My Fender Bassbreaker came with EL84s and its Fender marketing lists that as the tube type, not 6BQ5. It just strikes me as an odd choice and could be somewhat confusing for the uninitiated.
Fair point! I think I was trying to leave a little context clue for anyone who might have been confusing 6AQ5 and 6BQ5, but yeah EL84 is probably the more common part# overall.
@@graybenchelec Thanks for the quick reply. I take your point about 6AQ and 6BQ tubes and it's a valid one. BTW, love the channel, keep up the great work!
American-made new-old-stock 6BQ5 and 6CA7 are likely to be beam-power tetrodes and not true pentodes like European EL34 and EL84 tubes. Phillips held the original patent on Pentode tube design and most American manufacturers didn't want to pay Philips to manufacture their own pentodes, so they developed beam powered tetrodes which have beam forming plates to direct the electron stream. 6BQ5 and 6CA7 are pin-out plug-in compatible with EL84 and EL34 respectively, but the performance might be a little different in some cases. Towards the end of the tube erar, of course, many American manufacturers such as RCA were importing tubes from Europe and rebranding them, and so you might see true pentodes bearing American brand names ----- And it's possible that the Phillips patent may have run out and allowed American companies to produce their own pentodes, but would manufacturers bother to retool for this in the 1960s when it was clear that the era of vacuum tubes was ending soon?
Replacing this cap os gonna suck, don’t put it there……. 😮 im confused…… i thought you built the amp? How many watts is it putting out?? Seems to sound pretty good……
Actually, a proper EL84, at least if New Old Stock and made in Europe, would almost certainly be a true pentode, but an American 6BQ5 might be a beam-power tetrode instead. American manufacturers developed beam-power tetrode versions of European pentodes so they wouldn't have to pay the Phillips pentode patent. Similarly, the American 6CA7 is analogous to the European EL34 and pin-out compatible, but the 6CA7 might not be exactly the same internally or performance-wise because it doesn't have a suppressor grid like a true pentode does.
IIRC, there were 3 or 4 versions of the Skylark: single EL84, dual EL84 push-pull, dual 6AQ5 push-pull, and perhaps another version with single or a pair of 6BM8/ECL82....
So whats your point except to up the price of 6aq5 tubes? Thanks bro, UA-cam is replete with uping the price of everything from cheap amps to cheap guitars and now cheap tubes, i should think you are cool as cool,ok, whatever.
fair point, I get annoyed sometimes when a content creator comes out and say," Did you know that you can get blah blah which is better than blah if you just blah" Sometimes I am like damn dude stop telling our secrets so dudes on ebay jack up the prices even stupider than they are. Not long ago I could go into a second hand/thrift store and buy a tube radio or R2R for $10 now people think they are worth $150 if you get to charge $50 to ship them. I keep having to remind local dealers " just because someone on ebay is asking $100 doesn't mean it is worth $100"
6V6 and 6L6 are the most popular period especially in America. The Frequency of a 6aq5 is inferior plate voltage wise compared to 6v6 . 6BQ5 is a better choice vs 6aq5 ! What advantages? This is pointless None ! 6v6 is superior 6v6 has better low and mids the input capacitance is lower which equates to better headroom ! Enjoy your odd ball over priced just to be different amp 🤔 💭
🤔Do you build amps? I do, you are mistaken on several things IMHO. The only thing that I agree with is 6V6's and 6L6's are the most popular in America. They are also still made today in Russia, Czech Republic and China so there is that, but when you can buy a pair of these 6AQ5's vintage RCA NOS for about the same as 1 brand new Russian 6V6 or but a 60's tube reel to reel recorder with a pair of them, a 6CA4 rectifier and a couple RCA 12AX7's for like $40, I am not sure how this is overpriced. I literally buy vintage tube gear cheap, gut them and build stuff equal in tone to a legit 50's or 60's vintage amps for less than $100 all in regularly. Just sayin' don't be a hater bra.
@@skullheadwater9839 RCA tube manual says that the 6AQ5 has a max plate voltage of 275 volts and the same for the screen grid. The 6V6 is rated at a max plate voltage of 350 volts and a max screen voltage of 315 volts. Apparently that it the operational difference between the tubes. Obviously, we know that a 6V6 will operate above that voltage because Fender has been putting 400 volts plus on them since the late 1960s... I know that Gibson used the 6AQ5 in some of their little amplifiers with pretty good results.
@@skullheadwater9839 The 6V6 / 6AQ5 schematic is only basically similar (The 6V6 /6AQ5 in U.L. mode requires an 8k impedance for the OT the larger tube of the 6v6 takes heat better as well as higher voltage. I been in the electronics field industry since the 70s yes I built and repaired many Tube amplifiers even a few Dumbles . As a matter of fact I recall some manufacturers used the 6aq5 in vertical deflection circuits in TVs . The 6AQ5 is a power beam type tube, like a 6L6. The 6BQ5 is a power pentode, like a EL34. Like I said before 6v6 has a lower input impedance which has more headroom which equates to nicer cleans also 6V6 is a larger tube which equates to better heat handling and higher plate voltage so that's why I prefer it plus I have stock piles of vintage RCAs just sitting around NOS since the 70s . No Hate here and no I am not into bras ? 🤔
Sorry .. Absolute rubbish as it is an EL84 and this is widely used as a pair for 15 Watts or as a Quartet for 30 Watts. Morgan AC20 ? Vox AC15, Vox AC30..Orange AD30 ....Fender Pro Jr ....
@@cliverkay , yup, 7 pins. Pretty much the same specs as a 6V6 except for lower plate voltage handling and lower power dissipation. A pair of them in push-pull can still put out 10 watts or so, perhaps more. I have about 50 of the uprated, ruggedized, military 6005WA version, which I bought at a ham fest for about $2 each a while back; I really need to build some amplifiers with them!
In your mention of the 4 most popular output tubes, how did you not mention the EL84? You're right. The 6AQ5 is realistically non-existent in the guitar world. Going with the late-stage, cathode follower tone stack harkens back to the earlier 'bassman' (and soon after, Marshall) concept. Not my favorite. 🙂 But it works for lots of people. Being almost strictly an SE guy, I'd be interested in seeing how one of those would sound like that. I use EL84's and 6V6G* depending on how I feel that day. 🙂 But I'm also interested in trying new stuff too. Thanks for the heads-up.
@@graybenchelec Yes, that's true. Sorry I didn't catch it when you said it. Considering that it's the tube used in amp designs just as historically and musically important as the EL34 and 6L6 (vox, matchless, victory, marshall, hiwatt, fender, etc.), I guess I just was missing equal love shown for the type I use for 5 out of 6 amp builds I do. 🙂 Thanks, again, for the info on the 6AQ5. I'm always looking for something new to play with. Have fun!
Words can not express how much I did nt expect you to play Hocus Pocus then. A man of culture, I see!
Just need the red subaru now...
Terry from D-Lab has had good things to say about the 6aq5. He has used them in push pull and single ended amps.
I just finished gathering the big heavy stuff for a 5881 single-ended. It's going in a home-built radio project. I could also build one with a 6AK6. The rest of the radio is solid state for too many reasons. But the audio section is 3 stages of tube amplification, with a 6SN7 mixer that plays the radio on one side and a musical instrument and effects on the other. The radio itself is being built using an old stereo speaker, decorations, and lighting, to simulate a jukebox (tombstone!) radio from way back when. Keeping in with the era it's from, before television, before transistors, before Internet (yes, there was such a time period)... so it will cover as many bands as I can think of.
In Europe you find these tubes also under the name EL90
Of course I have heard of the 6AQ5 tube, it is literally my favorite tube amp ever !
The 6BQ5 were part of the output of the Grundig tube type reel-to-reel tape players.
I also have a stereo tube amp, maybe 2 in storage that uses those as well. The one is just the raw amp with a pre-amp and connectors, the other has the normal volume, bass, treble, and balance controls, it might have come out of a old phono or radio floor console.
I've never met a 22mF cathode bypass cap that I liked. It just seems to muddy things up, while providing no real bottom end. I tend to like between .68 and 2mF, or something around 100mF, depending on the amp and the desired musical application/focus. But maybe that's just me. Still, I'd like to see more experimentation in this area, 22mF is just kind of taken for granted as the go-to value. Really nice looking piece though, no doubt about that. And thanks for hipping us to this tube.
Hocus Pocus! Nice sounding amp and great example of using less-common output tubes. Thanks for posting.
Nice building , clean job and good sound !
Another nice sounding 6V6 tube is the old 6V6G ...........also wonderfull sounding and one of my favorites .
Just don't put a 6V6G into an amplifier like a Deluxe Reverb that was designed for a 6V6GB and runs the tube at 70 volts over its rating!
@@goodun2974 That's right ( same with 6L6 etc ).............I know the ratings ........the issue of my comment was the sound quality .
kind regards
In the old days when I repaired tube TVs I have seen the 6AQ5 used as a vertical output.
I have a stack of 6W6's around here I'm thinking of doing something with. Since the filament current is around 3 times👍 that of an L6 I'll have to find a power transformer with a heavy filament winding or use a separate filament transformer.
Good design on your amp. 👍
6AQ5s are the basis of a lot of my DIY projects, I'm trying to keep them a secret so they stay cheap haha
6aq5 and el84 are interchangeable.
Wow I got a bunch from a auction some are nos some used. They test from 73% to 94% . Now I think that I'll use them.
Great for a super compact single ended project too. They don’t kick off a whole lot of heat when you run them inside design limits.
Hi I would use 6BQ5/EL84 instead , nice tube in SE configuration both for hi fi and guitar. For Hi Fi you need global negative feedback.
Quite a few old tube console stereos used 6AQ5 tubes.
My grandpa’s did.
and R2R tape recorders....
@@skullheadwater9839, interestingly, Voice of Music portable phonographs and reel-to-reels (a favorite of mine for scavenging parts from) typically used single-ended octal output tubes (usually 6V6, occasionally 7591) and not miniature tubes like 6AQ5 or EL84.
The early 70s version of the Fender musicmaster bass amp uses a pair of 6aq5 power tubes...the later version uses 6v6s...you can tell them apart because the early ones don't have a separate on/off switch
6AQ5's are cool tubes, I thought you were going to say something like a tube that was used as a horizontal deflection amp or something which I probably have some of too. I have built around 5 or 6, 6AQ5 amps. They have their own sound and have a really smooth overdrive sound. Nice tube, easy to find and cheap for NOS. Another cool thing is to build with 12V6's using a separate 12v filament XFMR.
Very nice description! The IC caps are a fantastic choice too. I know those grid coupling caps from the phase inverter to the output stage are hiding in a page fold somewhere ;^)
Hah! I knew someone would catch my error in haste, couldn't imagine it would be Mr. Carlson himself. Thank you for yet another lesson in the need for attention to detail 🤣
The Fender Princeton used the 6V6 and sounded wonderful
Well yeah, but there's just something about how the GE 6AQ5 breaks up. They are also very cheap and very well made.
After the war there was a rush to introduce more compact tubes, and it certainly conserved space in television chassis where the tube count was high. I think it didn't catch on in the guitar amp world because it is was no different than the 6V6 and space was really not important. Certainly the 6V6 was popular in push-pull phonograph amplifiers and perhaps was something that amplifier designers were comfortable with. Perhaps that is a good thing because there are still manufacturers making 6V6, 6L6, EL34 many of these other tube may begin to fall into short supply... not that this tube is uncommon, but more in reference to the tubes that were made in the mid to late 1960s that were a desperate effort for tubes to remain relevant in a solid state world.
That's funny, I just heard about these the other day. Magnatone is making a Billy Gibbons signature amp using these for the output.
Check out the EL86/6CW5. Doesn't do well when tube rolling 6V6 amps but if you design around it it's great. Cheap. Used to be ridiculously cheap.
Nice neat build and sounds great.
I think Terry of D-Lab may build amps with 6aq5 tubes.
Nice work!
Awesome. Wonder if there are octal-to-seven-pin adapters like yellow-jackets. I have 6N7S to 9-pin preamp ones...
Great sounding amp!
I built a little JCM800 with those. They're close on the datasheets but in practice 6V6s are used often with over 400 volts on the plate. It would be interesting to know what a 6AQ5 could really deal with.
Agreed! I know Gibson had no problem running 6AQ5 at 300V, 400V might be pushing it in the smaller tube package.
Due to the smaller size they physically can't dissipate the heat of and octal tube with all other things the same.
Sounds good
The JJ 6V6S is a superior choice, with a max plate dissipation of 14W, plate voltage of 500V.
I can see that in the sense of the fact it handles more voltage but as an amp builder you are the one who controls that so you can design the power supply to put the ideal voltage for this tube as well. They have a different tone, the sound very smooth compared to a 6V6, I actually prefer them to 6V6's and have built a handful of amps with 6AQ5's. I actually built an amp using all 12volt tubes using 12AQ5's which I want to say I got a sleeve of 5 NOS for $25. It is one of my favorite sounding amps.
6AQ5s were a common tube. While true that they weren’t used in guitar amps, they were everwhere in early tube stereos, radios and audio circuits of tube televisions. The low prices on eBay reflect their ubiquitous nature as they have been hiding out in dusty tube caddies that were, long ago, raided for 12AX7s….
Nice blue pilot light.
I like it too
Naughty little amp! What speaker/s you driving? Closed/open back?
I used the 6aq5 in my last pp build - wonderful sounding tube. I see you used the Hammond 270DAX - that means you have about 367VDC on the plates. That's quite a bit over the data sheet max of 275V. How has tube life been?
367V would be about right if it was solid state rectification, but don't forget the 6CA4 drops about 60V. Plate voltage is right around 305V. That's still in excess of the 250V or 275V shown on 6AQ5 datasheets, but the handful of guitar amps out there run the plates at ~300V no issue.
I had a 6aq5 pa amp converted for guitar years ago, it was decent.
The 6AQ5 can't dissipate as much heat as a 6V6, it's in a smaller bottle & has a smaller anode. I'd like to see a soak test comparison or testing after 1000 hours of use at high power OP. Still in a practice amp or home use it's absolutely fine.
e-Bay is *far* from the only source of tubes. When one knows where to look, one finds that the 6AQ5A/6005 is common and inexpensive.
So true, good news is they tend to be ~$10 for high quality tubes... for now 😉
6V6 tubes are wonderful. Anytime you can use a 5881 in place of a 6L6, DO IT!
Sounds great on my $30 Genius PC speakers
Can't ask for more than that!
Hi, try making a Fender Deluxe Reverb, or Princeton Reverb with 420V average plate voltage with 6AQ5 (arc in 10 minutes), I don´t know why you didnt use a current production rectifier ass well. To me 6AQ5 are more like 6BQ5 with an, unusual , for 21th Century , 7 pin base only found in old radios a TV. You could have put 6bq5 in that amp (with 9 ping sockets) and sound almost the same with a little more gain (a BOX like sound). no feedback, only difference is rectifier tube and individual cathode resistor witch changes gain structure and harmonic dist. and different tone stack and PI, a long tail would allow to put the master post PI (also biased cooler than a BOX AC15 witch is nice,). A nice experiment but impractical if you want to build one and need tube stock and reliability as you said there are no current production 6AQ5, for me, the big difference between a 6v6 is max plate voltage. 250V max plate is too low for a guitar amp. I know you can abuse them but not much, 300v top. And they won´t last. Again a nice experiment. You used good iron, that helps. Cheers.
My exact 💭 thoughts
I guess if you are using off the shelf transformers made for a deluxe but, a builder can make whatever he wants. I have built amps out of control transformers that put out 240v, with a bridge you get about 325v before load, you just use a separate 6.3v filament transformer. The cool thing is you can usually get both for less than you pay for one of those "fender" replacement transformers. It just depends on what you want to build vs how much you have to spend. If you are building clones, I suppose it may be the safe option to buy a kit or individual parts made for your clone but every amp I build is a unique entity. I generally do use modified existing concepts for successive stages. For instance, the last amp I built was sort of using the idea of a 5E3 preamp but instead of using a 12ax7 I used two separate tubes a 6SJ7 pentode and a 6SF5 which is an octal triode with 100mu, using the same basic interactive V,V,T, scheme of a 5E3 but then I used a 6SL7 set up as a paraphase inverter into a pair of cathode biased 6V6's. This thing sounds phenomenal, like nothing else. I used the chassis/PT out of a 1954 Revere R2R with a OT from a 59' Conn Organ. It is mounted in an upright 59' Magnavox record player console with a 57' 12" magnavox alnico speaker out of a different console.
@@skullheadwater9839 HI, I put " Fender Deluxe Reverb" not as a brand or specific model, It cuold be any clon with similar circuit, It´s not an unusual one , didn´t mean to put "Fender" in the context of cost or status as vitage or valuable device.
Gray, you do of course realize that if you could formulate a version of the classic Champ with this tube and somehow find inexpensive transformers (maybe possible because of the lower plate voltage or a doubler? that you would be the amp geeks version of Mr Beast with millions of subscribers? Well maybe not millions but I do think you would be a real hero!
Hah not so sure about that. You could use 6AQ5 in a 5E3 kit, just have to do something about the plate voltage. There's solutions out there!
It is a cool tube but many of us amp builders know about them and have already been using them for years. No disrespect intended to Mr. Gray.
Nice!
A pair of silicon diodes in series with the rectifier's plates are a bit like belts and braces, no?
The series diodes are protecting the power supply from a shorted rectifier tube. Without those diodes, the filter caps could potentially see very high AC voltage and fail spectacularly! See Robrob's info on "backup" diodes: robrobinette.com/Generic_Tube_Amp_Mods.htm#Protection_Mods
Not only do the diodes add protection for the power transformer and rectifier tube, as described here, but you still get the sag and compression of a rectifier tube when you play hard (a fully solid state power supply would be much stiffer feeling) and it also still gves a gentle time delay of the B+ feed to the tubes and caps at turn-on.
Winfield Thomas build a 5 watt amp out of spare parts. He put both power tubes in the amp a 6v6 and a 6AQ5. He sent it to me. You can only use one tube at a time you would have to pull the other tube out. There wasn't much of a difference at all
Khan Audio uses the 6AQ5/6005 in their PAK amps - check them out...
Never heard of them, originally saw the video & thought it was an el84
The schematic for the amp bears a resemblance to a Garnet Herzog or a Fender Champ.
How so? It has a DC coupled cathode follower into a tone stack, a master volume into a Cathodyne PI into Push Pull power tubes. A champ is literally two preamp stages into a power tube. This is sort of a mixture of a Brown face Fender deluxe front end with a master vol added into a 5E3 tweed power section with some component values changed.
EL90 in Mullard Phillips terminology.
6BQ5 or the higher plate dissipation 6CW5? For the 6L6 the 8417 6550 etc real American, penta labs.
I think you forgot the coupling caps between the phase inverter and the grids of the two power tubes.
Also known as a split load phase splitter.
Wonder how that would sound with EF86 front end?
Hard to get quiet, non -microphonic EF86 these days, and vintage EF86 are expensive; I'd be tempted to use 5879 low-noise pentodes instead (often used as a mic preamp in vintage PA equipment); not super common these days, but available as NOS, and not terribly expensive. Or perhaps even 6AU6 which are common and cheap as chips; you could buy a dozen of them for about 3 bucks each and select the quietest ones. BTW, I have a big Webster PA/paging amp with 4 !!! 5879 inputs, 4 6L6's, and two 5U4's, which is just begging me to build a guitar amp out of it....
6146A in a Williamson circuit…..beefy!
The 807 was often used in Williamson amp designs. They're still fairly common and affordable today whereas the 6146A is rare and pricey and perhaps should be saved for use in original early Ampeg SVT bass amps.
@@goodun2974 The 807 is just a 6L6G with a plate cap, (not the GC version.) The 6146A and B versions are a nice powerful compact tube for RF and modulator service, along with the S2001, 6883 and 8298.
@@MrCarlsonsLab , If I remember correctly, the 807 could handle significantly higher plate voltage than a 6L6G, which is why it was favored for use in small RF transmitters (6L6G was rated for only 300 volts). The 6146A and B are very different animals, of course.
@@goodun2974 Yes, the reason the 807 could handle more plate voltage is the plate connection is on the top of the bulb, not in the octal base like the 6L6G. The internal structure between the two is identical.
@@MrCarlsonsLab , Of course, 807 were usually used in class B as transmitters and therefore coul handle even more voltage than you might expect, compared to what they can handle as class AB audio amplifiers.....
Mm... nagging question. What do the output tubes sound when pushed compared to 6L6?
Do you have a speaker emulator?
I would generally reject the idea that output tubes have an inherent sound. Even if it was true, being able to separate it from difference in circuit design, actual component values vs. marked values, and subjective listening would be impossible.
I don't think I do.
@@graybenchelec, In general I would tend to agree with you, but I also had an experience with a Kalamazoo Model One that I had recapped which sounded kind of tame with 3 or 4 other strong-testing American and Japanese 6BQ5's but when I installed a good used European Amperex Bugle Boy EL84 into it, the amp turned into a tiger and sounded very much like a miniature Vox AC30. The difference was staggering! In hindsight I am guessing that the Amperex EL84 was a true pentode with internal suppressor grid, and the American and Japanese tubes I tried were beam power tetrodes, not true pentodes.
You must be watching D-Lab.
My first interaction with 6AQ5 was a Gibson Scout I bought a while back. GA-17RVT I believe. But I do enjoy his videos as well, yes.
Curious, why cite the EL34 and not a 6CA7 but then referred to the EL84 as the 6BQ5? I never hear anyone refer to EL84s by the American 6BQ5 nominclature. My Fender Bassbreaker came with EL84s and its Fender marketing lists that as the tube type, not 6BQ5. It just strikes me as an odd choice and could be somewhat confusing for the uninitiated.
Fair point! I think I was trying to leave a little context clue for anyone who might have been confusing 6AQ5 and 6BQ5, but yeah EL84 is probably the more common part# overall.
@@graybenchelec Thanks for the quick reply. I take your point about 6AQ and 6BQ tubes and it's a valid one.
BTW, love the channel, keep up the great work!
Yes EL84 tubes tubes have it hands down. Lol.
American-made new-old-stock 6BQ5 and 6CA7 are likely to be beam-power tetrodes and not true pentodes like European EL34 and EL84 tubes. Phillips held the original patent on Pentode tube design and most American manufacturers didn't want to pay Philips to manufacture their own pentodes, so they developed beam powered tetrodes which have beam forming plates to direct the electron stream. 6BQ5 and 6CA7 are pin-out plug-in compatible with EL84 and EL34 respectively, but the performance might be a little different in some cases. Towards the end of the tube erar, of course, many American manufacturers such as RCA were importing tubes from Europe and rebranding them, and so you might see true pentodes bearing American brand names ----- And it's possible that the Phillips patent may have run out and allowed American companies to produce their own pentodes, but would manufacturers bother to retool for this in the 1960s when it was clear that the era of vacuum tubes was ending soon?
@@goodun2974 probably not but you misspelled era, so...can I trust you? Lol.
Replacing this cap os gonna suck, don’t put it there……. 😮 im confused…… i thought you built the amp? How many watts is it putting out?? Seems to sound pretty good……
Just a bit of self-deprecating humor 😉I haven't measured the output wattage, probably about 10W.
6Bq5...popular tube, pentode, 6V6GT popular beam powered tetrode
Actually, a proper EL84, at least if New Old Stock and made in Europe, would almost certainly be a true pentode, but an American 6BQ5 might be a beam-power tetrode instead. American manufacturers developed beam-power tetrode versions of European pentodes so they wouldn't have to pay the Phillips pentode patent. Similarly, the American 6CA7 is analogous to the European EL34 and pin-out compatible, but the 6CA7 might not be exactly the same internally or performance-wise because it doesn't have a suppressor grid like a true pentode does.
Skylark had 6BQ5s
IIRC, there were 3 or 4 versions of the Skylark: single EL84, dual EL84 push-pull, dual 6AQ5 push-pull, and perhaps another version with single or a pair of 6BM8/ECL82....
A 6V6 GT? 6VQ5? You mean a 6BQ5?
The first tube was a 6V6GT, the second tube, and subject of the video, is 6AQ5.
Sounds kinda whimpy compared to el84 new stock tubes, just saying.
How do you know?
Yeah, you exceed the maximum plate voltage on your outputs,
and you pay for it by having to replace the damm things every few months.
So whats your point except to up the price of 6aq5 tubes? Thanks bro, UA-cam is replete with uping the price of everything from cheap amps to cheap guitars and now cheap tubes, i should think you are cool as cool,ok, whatever.
fair point, I get annoyed sometimes when a content creator comes out and say," Did you know that you can get blah blah which is better than blah if you just blah" Sometimes I am like damn dude stop telling our secrets so dudes on ebay jack up the prices even stupider than they are. Not long ago I could go into a second hand/thrift store and buy a tube radio or R2R for $10 now people think they are worth $150 if you get to charge $50 to ship them. I keep having to remind local dealers " just because someone on ebay is asking $100 doesn't mean it is worth $100"
6V6 and 6L6 are the most popular period especially in America. The Frequency of a 6aq5 is inferior plate voltage wise compared to 6v6 . 6BQ5 is a better choice vs 6aq5 ! What advantages? This is pointless None ! 6v6 is superior 6v6 has better low and mids the input capacitance is lower which equates to better headroom ! Enjoy your odd ball over priced just to be different amp 🤔 💭
🤔Do you build amps? I do, you are mistaken on several things IMHO. The only thing that I agree with is 6V6's and 6L6's are the most popular in America. They are also still made today in Russia, Czech Republic and China so there is that, but when you can buy a pair of these 6AQ5's vintage RCA NOS for about the same as 1 brand new Russian 6V6 or but a 60's tube reel to reel recorder with a pair of them, a 6CA4 rectifier and a couple RCA 12AX7's for like $40, I am not sure how this is overpriced. I literally buy vintage tube gear cheap, gut them and build stuff equal in tone to a legit 50's or 60's vintage amps for less than $100 all in regularly. Just sayin' don't be a hater bra.
@@skullheadwater9839 RCA tube manual says that the 6AQ5 has a max plate voltage of 275 volts and the same for the screen grid.
The 6V6 is rated at a max plate voltage of 350 volts and a max screen voltage of 315 volts.
Apparently that it the operational difference between the tubes.
Obviously, we know that a 6V6 will operate above that voltage because Fender has been putting 400 volts plus on them since the late 1960s...
I know that Gibson used the 6AQ5 in some of their little amplifiers with pretty good results.
@@skullheadwater9839 The 6V6 / 6AQ5 schematic is only basically similar
(The 6V6 /6AQ5 in U.L. mode requires an 8k impedance for the OT the larger tube of the 6v6 takes heat better as well as higher voltage. I been in the electronics field industry since the 70s yes I built and repaired many Tube amplifiers even a few Dumbles . As a matter of fact I recall some manufacturers used the 6aq5 in vertical deflection circuits in TVs . The 6AQ5 is a power beam type tube, like a 6L6. The 6BQ5 is a power pentode, like a EL34. Like I said before 6v6 has a lower input impedance which has more headroom which equates to nicer cleans also 6V6 is a larger tube which equates to better heat handling and higher plate voltage so that's why I prefer it plus I have stock piles of vintage RCAs just sitting around NOS since the 70s . No Hate here and no I am not into bras ? 🤔
@@skullheadwater9839 Some of the JJ teslas 6V6 Power Beam tetrode that performs flawlessly at up to 475 volts! No 6aq5 will touch that !
Sorry .. Absolute rubbish as it is an EL84 and this is widely used as a pair for 15 Watts or as a Quartet for 30 Watts. Morgan AC20 ? Vox AC15, Vox AC30..Orange AD30 ....Fender Pro Jr ....
The EL84 equivalent is a 6BQ5. The EL90 is the equivalent to the 6AQ5 tube shown in this video.
I stand corrected! And only 7 pins ..?
@@cliverkay , yup, 7 pins. Pretty much the same specs as a 6V6 except for lower plate voltage handling and lower power dissipation. A pair of them in push-pull can still put out 10 watts or so, perhaps more. I have about 50 of the uprated, ruggedized, military 6005WA version, which I bought at a ham fest for about $2 each a while back; I really need to build some amplifiers with them!
In your mention of the 4 most popular output tubes, how did you not mention the EL84?
You're right. The 6AQ5 is realistically non-existent in the guitar world.
Going with the late-stage, cathode follower tone stack harkens back to the earlier 'bassman' (and soon after, Marshall) concept. Not my favorite. 🙂
But it works for lots of people.
Being almost strictly an SE guy, I'd be interested in seeing how one of those would sound like that. I use EL84's and 6V6G* depending on how I feel that day. 🙂 But I'm also interested in trying new stuff too.
Thanks for the heads-up.
I sorta did, EL84 and 6BQ5 are interchangeable.
@@graybenchelec
Yes, that's true.
Sorry I didn't catch it when you said it.
Considering that it's the tube used in amp designs just as historically and musically important as the EL34 and 6L6 (vox, matchless, victory, marshall, hiwatt, fender, etc.), I guess I just was missing equal love shown for the type I use for 5 out of 6 amp builds I do. 🙂
Thanks, again, for the info on the 6AQ5. I'm always looking for something new to play with.
Have fun!