One thing I've always liked about Dr. Z amps is the robust construction of the boards with a lot of distance between components, limits crosstalk and potential trace to trace short and leakage problems. The builders are good people to work with, too. Simplicity is a good thing.
I am about to build a DIY version of this amp. A lot of my research including comments from Z himself noted that soft filtering led to slight ghost notes some liked them some didn’t so he increased the filtering in later models. He also suggested that the 5U is softer than the recommended GZ …. This vid is going be very helpful.
I'm playing my 15th anniversary Route 66 as I watch this. I was recently tempted to sell it, but after subbing out the 12AX7 with a 12AT7 for more clean headroom this baby is staying with me. Nothing sounds quite the same and the amp has a glorious midrange.
I really appreciate the review and watching what you’re doing here. I’ve been looking at this amplifier one that’s used for $1400 in great condition I mean actually the boxes in excellent condition of course but without buying it I can’t have the inside looked at it’s a guitar center Unit and they have had it for sometime. This would be a great amplifier for me to use gigging. I like the simplicity and the build quality and at that price it seems a reasonable just curious about your opinions and is it also do you think worth buying the extended warranty they offer for a few hundred dollars and then they have to replace it no matter what I really wondered about that warranty although I have not bought, any from guitar center I have bought extended warranties on my Marshall amplifiers and Friedmans, my higher and stuff from them but I wonder is this a better option than just getting the Friedman dirty Shirley are one of the little sisters thanks for any feedback needing that KT 66 or blues breaker sound most of what I’ll be playing in this particular situation Are those tones of Clapton with this new band? Thanks. 5:39
One thing I don't get is why amp designers still put the reservoir caps after the standby switch. From what I understand, Leo and his engineers realized the impact this had on rectifier tubes and changed their design accordingly. Is there something I'm missing? Thanks for the video, Lyle!
@@YeatzeeGuitar , Not having worked on a Vox myself I could appreciate your struggles and you trying to figure out the circuit and how to maneuver around it when changing parts. I've worked on some point-to-point Magnotones as well as Silvertone/Danelectro amps, But that Vox has a much higher Component density and I really don't like those terminal strip boards they use, not to mention all the red paint.
I’ve had those 10W resistors fail when they are free floating like that. They are heavy enough that they move about when transporting the amp, causing fatigue of the wire which breaks off at the junction with the body of the resistor. They need to be fixed to something. Another great video thanks.
It’ll be interesting to see which MV you go with. I built one of these from a Rauland PA with 6v6’s and a non ultra linear otx which is essentially a Z/28 Mk I. The #3 ppimv seemed to work best and was also the least complicated. The CTS pot I used (from the original PA) had a weird taper but it gets the desired effect done. Tried a dual gang but it changed the tone too much. Had a more gradual controlled taper tho.
Looking forward to hearing one or two. Maybe some kind of side by side with commentary of any circuit changes and their differences. And how you got them to sound alike per the owner.
For what it’s worth, I believe Dr Z added the extra filtering on later models to help with excess note ghosting that many people experienced with these amps.
Great vid as always. Is there any chance of explaining the tone stack of the RT 66? I've owned one since 2005 and every time I look at the tone stack, I have trouble wrapping my head around it. Also, now I'll have to look into adding a MV to mine instead of using the z-brake.
Hi Lyle. Big fan of the channel. I have 20+ tube amps and I always gain knowledge from your videos. I have two Dr Z’s, a RT66 built by Dr Z, or so it’s labeled and a 6545 head. Both sound great once you back off the treble a bit. I’m sure my RT66 has the same stand by rectifier issue. Would it be best to not use the standby switch until I get the change you suggest made? I have vintage glass in the recto btw.
I have one and would love to have a master volume added. I actually sent Z a question about it a few years ago and they said that they couldn't add a master for some unspecified reason ( I no longer have the note). Obviously you can do it. Any idea why Dr. Z might have balked at doing it?
Hey Bud good Morning from Boston so I watch your Channel. And I wish we had a tech like you around here I simply cannot find a good guy so the question I have is have you ever reached out to like doctors Z or other manufacturers to find out why they designed things the way that they did?? I guess what I'm asking is do they just copy somebody's Elsa's work or do they literally come up with these electronic schematics themselves or just put things like transistors and stuff where they think they should go
Lyle, on the subject of tube rectifiers, I've noticed that Brad likes to add diodes to their sockets as a backup in case the rectifier fails. Any thoughts on this practice? I'd think it has to change the sag characteristics of the amp, which is important to some. Mind you, Brad is a sharp guy, I don't question his skills at all...I'm just looking to learn something!
Those diodes aren’t backups in case of a failed tube - they’re in series with the tube and help the tube have fewer voltage spikes and current surges. I add them quite often.
Gotcha, thanks! In series wouldn't change the characteristics of the tube rectifier, I somehow assumed they were parallel. I'm thinking 1N4007 would be fine, I've got a pile of those. I don't trust that JJ rectifier in my AB763!
@@PsionicAudio , do you use just one 1N4007 (or 5408 perhaps) per secondary leg or do you use two or three diodes in series on each side before the rectifier tube?
I learn from each of your videos. Thank you. BTW, I don't know if you have tried JIS screw drives. If you haven't, give them a try, you may never use a Philips again...
JIS screwdrivers, such as those made by Vessel, are only truly fully compatible with JIS screwheads (which usually have a little dot or divot pressed into the heads). JIS screws were frequently used in Japanese hifi and Japanese motorcycles, but I've never seen them in a guitar amp. With screwdrivers and other fasteners, the name of the game is similar to the name of the game when fly fishing: "match the hatch"!
@@goodun2974 Due to a lifelong obsession with motorcycles, I have used JIS screwdrivers on JIS screws for decades. I have also noticed that when I use the JIS standard on Philips screws there was less of a tendency to strip or damage the screw. I tend to go with what works, not what is supposed to work...
@@luizdejesus6240 , JIS screwdrivers are uncommon in the US , and not sold in most hardware stores, only online. Most people aren't even aware rhat there is a difference! I discovered that impact-driver rated Milwaukee Philips bits are an excellent fit for JIS screws. Some other brands are a particularly poor fit.
@@luizdejesus6240 , I actually yelled at my boss, the owner of an audio repair shop, for using a regular Philips screwdriver to remove Pozidrive screws, which tends to chew the shit out of them.
When will these guys follow the tube makers books on rectifiers . It not like the knowledge has been hidden for the last 80 years. Tone is one thing power supplies is a whole different thing. Reliability come from staying inside the envelope of the device. IMHO the first cap should be about 20 then a resistor and second cap so as to not shock the diode . This reduces the ripple also . First cap the 20 a resistor then the 50 would work with the standby switch after . Just my thoughts.
There you go using your big brain again. And yes, I agree. A smaller additional filter stage before the big reservoir would do wonders. But I’ve not been asked to do a heroic redesign on these.
I just pondered if I could do that here and the answer is yes but not easily. No place to reliably mount a big 10W first resistor and still keep the added first cap negative away from preamp ground.
" Reliability comes from staying within the safe operating area of the device". Truer words were only rarely spoken, John. Perhaps modern tube amp manufacturers are listening too much Rush: "drive like the wind, straining the limits of machine and man".
It's because old tubes let designers exceed maximums back then. They didn't anticipate most tubes in the future would be built much less robust. Also didn't anticipate 110v, 115v, 117v would get standardized around 122v.
Anybody know a good way to clean silver fender grill cloth without removing anything from the cab? It's obviously brown and I'm tired of looking at it. I used some "Tough Stuff" cleaner stain remover with a brush and then used paper towels to soak it up. And that works pretty well. But I thought I'd ask in case there's a better way 🤷
I don’t know, but be very careful. Many solvents will affect the black paint on the baffle and then the black will bleed into the grillcloth. Even too much water can do this.
I have used Oxyclean crystals dissolved in warm water with a dab of dish soap added. It won't bleach the cloth but it will virtually melt away cigarette smoke and nicotine tar; you wouldn't think it'd work on smoky grille cloth, but it does. Of course you want to use the minimum amount possible and dry it off is quickly as possible. For what it's worth, I have also used the same oxyclean mixture and a scrub brush on a pole to clean mold and algae off the delicate cedar siding on my house (it won't kill grass or shrubs). I also have some old Excelite screwdrivers and nut drivers with clear, funky smelling butyl acetate handles that develop a crusty, waxy sort of mildew-looking residue on them over time, and the Oxyclean mixture will remove that as well. Similarly it's also good for cleaning the knobs of old radios and Scott or Fisher hifi (Marshall-like knobs that turn crusty white with age). The stuff is amazing! So far I have not found anything that it will damage, but of course you should proceed slowly and try it on an inconspicuous spot first.
I'm not sure I've ever seen a company so militant about "marking its territory" with red paint to spot after-factory modifications. Does Doctor Z have some lengthy extended warranty they're trying to protect by ensuring they don't do warranty work to correct someone else's mistakes? The layout seems pretty tidy, a good sign for long-term repairability -- other than the solid wire conductors you mentioned that make things hard to move around more than once.
What is the problem with putting extra filter capacitance after the rectifier? I can understand the concern about in rush current, but would not have 72 micro-farads instead of 40 micro-farads result in an even smoother DC supply? (I'm showing my ignorance here, I last studied circuit design back in 1976/77)
Tube rectifiers have a maximum uF rating. Too much filtering looks like a dead short and will burn out the rectifier Tube. I'm pretty sure valve wizard has something about this on their site. As an aside I've always wondered how they get away with it on the Dual/Triple Rectifiers which have 2 220uFs in series at the first B+ node.
@@PsionicAudio Go figure, that's Mesa Boogie for you.🙄 Knowing that crowd of MB fanatics I can already hear them making generalized statements about how they're 'built like tanks' or their's have never broken down, ect. Not all MBs are created equally. Some of them are pretty reliable but alot of them have serious basic design flaws that's sort of flabbergasting considering the complexity of the overall design. It almost gives me the impression they skipped electronics 101 and went straight to AP electronics😅
Because he was looking at a tube-rectified Vox circuit but wanted to add Standby (not needed). So he stuck one in where it seemed easy. Lots of builders do the same thing. Fender and Marshall did not. Even Mesa (copying Fender) got that bit right.
This Rt 66 is a Vox EF86 followed by a unique tone stack probably found in some older amp or hi fi system into a Vox PI with fixed bias KT66s. A well built good sounding Frankenamp, but a Frankenamp.
One thing I've always liked about Dr. Z amps is the robust construction of the boards with a lot of distance between components, limits crosstalk and potential trace to trace short and leakage problems. The builders are good people to work with, too. Simplicity is a good thing.
Thanks Lyle. It's always good to learn about amp manufactures' products from you and your colleagues, so I don't end up purchasing something scary.
Great video! I met Dr Z himself a few years back in Cleveland. He gave me a tour of the factory and answered several of my geeky questions....
This is a great counterpoint to your work (and torturous truth) on the Marshall DSL amps. Dr. Z good vibes!
I am about to build a DIY version of this amp. A lot of my research including comments from Z himself noted that soft filtering led to slight ghost notes some liked them some didn’t so he increased the filtering in later models. He also suggested that the 5U is softer than the recommended GZ …. This vid is going be very helpful.
Great video. I've always wanted a Dr Z to play around with
caught the 'trading places' reference. nice.
👍
Wow, good info on the standby placement, thanks!
I'm playing my 15th anniversary Route 66 as I watch this. I was recently tempted to sell it, but after subbing out the 12AX7 with a 12AT7 for more clean headroom this baby is staying with me. Nothing sounds quite the same and the amp has a glorious midrange.
I really appreciate the review and watching what you’re doing here. I’ve been looking at this amplifier one that’s used for $1400 in great condition I mean actually the boxes in excellent condition of course but without buying it I can’t have the inside looked at it’s a guitar center Unit and they have had it for sometime. This would be a great amplifier for me to use gigging. I like the simplicity and the build quality and at that price it seems a reasonable just curious about your opinions and is it also do you think worth buying the extended warranty they offer for a few hundred dollars and then they have to replace it no matter what I really wondered about that warranty although I have not bought, any from guitar center I have bought extended warranties on my Marshall amplifiers and Friedmans, my higher and stuff from them but I wonder is this a better option than just getting the Friedman dirty Shirley are one of the little sisters thanks for any feedback needing that KT 66 or blues breaker sound most of what I’ll be playing in this particular situation Are those tones of Clapton with this new band? Thanks. 5:39
I had a z28 mki which is based off this amp and it was glorious.
So well done thank you for your professionalism. 🌟🌟🌟🌟🌟
New and improved. I like it.
Good looking layout😎👍
😎✌👍❤🖖
“Trading Places” is always a good reference…!!!
One thing I don't get is why amp designers still put the reservoir caps after the standby switch. From what I understand, Leo and his engineers realized the impact this had on rectifier tubes and changed their design accordingly. Is there something I'm missing? Thanks for the video, Lyle!
Great video Lyle!
Thanks!
PS, Yeatzee, I enjoyed your recent AC30 refurb videos.
@@goodun2974 thanks!
@@YeatzeeGuitar , Not having worked on a Vox myself I could appreciate your struggles and you trying to figure out the circuit and how to maneuver around it when changing parts. I've worked on some point-to-point Magnotones as well as Silvertone/Danelectro amps, But that Vox has a much higher Component density and I really don't like those terminal strip boards they use, not to mention all the red paint.
@@goodun2974 I've got a 61 Magnatone 440 just staring at me, I've been to afraid to start on it it's a jumbled mess inside 😂
I’ve had those 10W resistors fail when they are free floating like that. They are heavy enough that they move about when transporting the amp, causing fatigue of the wire which breaks off at the junction with the body of the resistor. They need to be fixed to something. Another great video thanks.
It’ll be interesting to see which MV you go with. I built one of these from a Rauland PA with 6v6’s and a non ultra linear otx which is essentially a Z/28 Mk I. The #3 ppimv seemed to work best and was also the least complicated. The CTS pot I used (from the original PA) had a weird taper but it gets the desired effect done. Tried a dual gang but it changed the tone too much. Had a more gradual controlled taper tho.
Good practice is repetitious because it’s good practice.
:)
Very interesting
Looking forward to hearing one or two. Maybe some kind of side by side with commentary of any circuit changes and their differences. And how you got them to sound alike per the owner.
For what it’s worth, I believe Dr Z added the extra filtering on later models to help with excess note ghosting that many people experienced with these amps.
Should have been added to the screen node not the reservoir. Or John’s suggestion below with an additional small first filter stage added.
feeling good Withrop (@3;20)
Haven't had good luck with Dr Z's
Great vid as always. Is there any chance of explaining the tone stack of the RT 66? I've owned one since 2005 and every time I look at the tone stack, I have trouble wrapping my head around it. Also, now I'll have to look into adding a MV to mine instead of using the z-brake.
I’ll try to show that in the next one.
Hi Lyle. Big fan of the channel. I have 20+ tube amps and I always gain knowledge from your videos.
I have two Dr Z’s, a RT66 built by Dr Z, or so it’s labeled and a 6545 head. Both sound great once you back off the treble a bit.
I’m sure my RT66 has the same stand by rectifier issue. Would it be best to not use the standby switch until I get the change you suggest made? I have vintage glass in the recto btw.
Thanks! Just don’t use the standby switch - leave it in Play. Totally unnecessary in this amp - just an overcomplicated mute.
I have one and would love to have a master volume added. I actually sent Z a question about it a few years ago and they said that they couldn't add a master for some unspecified reason ( I no longer have the note). Obviously you can do it. Any idea why Dr. Z might have balked at doing it?
I wish my work looked that good.
Hey Bud good Morning from Boston so I watch your Channel. And I wish we had a tech like you around here I simply cannot find a good guy so the question I have is have you ever reached out to like doctors Z or other manufacturers to find out why they designed things the way that they did?? I guess what I'm asking is do they just copy somebody's Elsa's work or do they literally come up with these electronic schematics themselves or just put things like transistors and stuff where they think they should go
The "red paint" is just red sharpie, so it's presence doesn't guarantee the connection hasn't been modified.
Lyle, on the subject of tube rectifiers, I've noticed that Brad likes to add diodes to their sockets as a backup in case the rectifier fails. Any thoughts on this practice? I'd think it has to change the sag characteristics of the amp, which is important to some. Mind you, Brad is a sharp guy, I don't question his skills at all...I'm just looking to learn something!
Those diodes aren’t backups in case of a failed tube - they’re in series with the tube and help the tube have fewer voltage spikes and current surges. I add them quite often.
Gotcha, thanks! In series wouldn't change the characteristics of the tube rectifier, I somehow assumed they were parallel. I'm thinking 1N4007 would be fine, I've got a pile of those. I don't trust that JJ rectifier in my AB763!
@@PsionicAudio , do you use just one 1N4007 (or 5408 perhaps) per secondary leg or do you use two or three diodes in series on each side before the rectifier tube?
I learn from each of your videos. Thank you. BTW, I don't know if you have tried JIS screw drives. If you haven't, give them a try, you may never use a Philips again...
JIS screwdrivers, such as those made by Vessel, are only truly fully compatible with JIS screwheads (which usually have a little dot or divot pressed into the heads). JIS screws were frequently used in Japanese hifi and Japanese motorcycles, but I've never seen them in a guitar amp. With screwdrivers and other fasteners, the name of the game is similar to the name of the game when fly fishing: "match the hatch"!
@@goodun2974 Due to a lifelong obsession with motorcycles, I have used JIS screwdrivers on JIS screws for decades. I have also noticed that when I use the JIS standard on Philips screws there was less of a tendency to strip or damage the screw. I tend to go with what works, not what is supposed to work...
@@luizdejesus6240 , JIS screwdrivers are uncommon in the US , and not sold in most hardware stores, only online. Most people aren't even aware rhat there is a difference! I discovered that impact-driver rated Milwaukee Philips bits are an excellent fit for JIS screws. Some other brands are a particularly poor fit.
@@luizdejesus6240 , I actually yelled at my boss, the owner of an audio repair shop, for using a regular Philips screwdriver to remove Pozidrive screws, which tends to chew the shit out of them.
@@goodun2974 I've seen them in early JC's, but that's about it.
WHat type of this red ink used in eletronic. Thanks
Any thoughts on the Revv d20 and the new D25 amps?
When will these guys follow the tube makers books on rectifiers . It not like the knowledge has been hidden for the last 80 years. Tone is one thing power supplies is a whole different thing. Reliability come from staying inside the envelope of the device. IMHO the first cap should be about 20 then a resistor and second cap so as to not shock the diode . This reduces the ripple also . First cap the 20 a resistor then the 50 would work with the standby switch after . Just my thoughts.
There you go using your big brain again.
And yes, I agree. A smaller additional filter stage before the big reservoir would do wonders. But I’ve not been asked to do a heroic redesign on these.
I just pondered if I could do that here and the answer is yes but not easily. No place to reliably mount a big 10W first resistor and still keep the added first cap negative away from preamp ground.
" Reliability comes from staying within the safe operating area of the device". Truer words were only rarely spoken, John. Perhaps modern tube amp manufacturers are listening too much Rush: "drive like the wind, straining the limits of machine and man".
@@PsionicAudio Well you do what the customer is paying for . Here we talk theory there you do work that is paid for.
It's because old tubes let designers exceed maximums back then. They didn't anticipate most tubes in the future would be built much less robust. Also didn't anticipate 110v, 115v, 117v would get standardized around 122v.
Aren't those 1Ω 10W resitors a bit overkill? Each could probably handle 10 times the current that the PT can provide...
Yeah, total overkill and unnecessary stress on the tube socket pins.
Lyle, correct me if I'm wrong, but the Vox AC30CC2 has the a similar rectifier issue.
It’s worse on the CC because their standby lifts the HT CT causing big spikes.
Solid core wire….. belongs in houses…. Houses don’t normally get repeatedly dropped nor have to worry about noise.
Anybody know a good way to clean silver fender grill cloth without removing anything from the cab? It's obviously brown and I'm tired of looking at it. I used some "Tough Stuff" cleaner stain remover with a brush and then used paper towels to soak it up. And that works pretty well. But I thought I'd ask in case there's a better way 🤷
I don’t know, but be very careful. Many solvents will affect the black paint on the baffle and then the black will bleed into the grillcloth. Even too much water can do this.
I have used Oxyclean crystals dissolved in warm water with a dab of dish soap added. It won't bleach the cloth but it will virtually melt away cigarette smoke and nicotine tar; you wouldn't think it'd work on smoky grille cloth, but it does. Of course you want to use the minimum amount possible and dry it off is quickly as possible. For what it's worth, I have also used the same oxyclean mixture and a scrub brush on a pole to clean mold and algae off the delicate cedar siding on my house (it won't kill grass or shrubs). I also have some old Excelite screwdrivers and nut drivers with clear, funky smelling butyl acetate handles that develop a crusty, waxy sort of mildew-looking residue on them over time, and the Oxyclean mixture will remove that as well. Similarly it's also good for cleaning the knobs of old radios and Scott or Fisher hifi (Marshall-like knobs that turn crusty white with age). The stuff is amazing! So far I have not found anything that it will damage, but of course you should proceed slowly and try it on an inconspicuous spot first.
I'm not sure I've ever seen a company so militant about "marking its territory" with red paint to spot after-factory modifications. Does Doctor Z have some lengthy extended warranty they're trying to protect by ensuring they don't do warranty work to correct someone else's mistakes? The layout seems pretty tidy, a good sign for long-term repairability -- other than the solid wire conductors you mentioned that make things hard to move around more than once.
Marshall did it back in the day.
Vox did it as well.
I do it to my nails every now and again when I need to feel pretty.
What is the problem with putting extra filter capacitance after the rectifier? I can understand the concern about in rush current, but would not have 72 micro-farads instead of 40 micro-farads result in an even smoother DC supply? (I'm showing my ignorance here, I last studied circuit design back in 1976/77)
Read the 5U4GB datasheet. Notice the maximum capacitance.
Tube rectifiers have a maximum uF rating. Too much filtering looks like a dead short and will burn out the rectifier Tube. I'm pretty sure valve wizard has something about this on their site. As an aside I've always wondered how they get away with it on the Dual/Triple Rectifiers which have 2 220uFs in series at the first B+ node.
They often don’t. Dead 5U4s are common in those.
Cue someone saying they’ve never had a problem with *their* Mesa so I must not know what I’m talking about…
@@PsionicAudio Go figure, that's Mesa Boogie for you.🙄
Knowing that crowd of MB fanatics I can already hear them making generalized statements about how they're 'built like tanks' or their's have never broken down, ect. Not all MBs are created equally. Some of them are pretty reliable but alot of them have serious basic design flaws that's sort of flabbergasting considering the complexity of the overall design. It almost gives me the impression they skipped electronics 101 and went straight to AP electronics😅
I wonder why he wired it up the way he did?
What I want to know is why did Dr Z, who is a successful builder and designer… put that cap there after the standby? He should have known better, yes?
Because he was looking at a tube-rectified Vox circuit but wanted to add Standby (not needed). So he stuck one in where it seemed easy. Lots of builders do the same thing.
Fender and Marshall did not. Even Mesa (copying Fender) got that bit right.
This Rt 66 is a Vox EF86 followed by a unique tone stack probably found in some older amp or hi fi system into a Vox PI with fixed bias KT66s. A well built good sounding Frankenamp, but a Frankenamp.
Screwdrivers with fluted handles are uncomfortable. Be kind to your hands and get some with square or triangular handles. You deserve it.
zzzzzzzzzz zzzz