You are spot on about the synergy - some stuff just dont jive with each other, no matter the price. Other times, you get those magic pixies to mash together so incredibly well that you cannot believe its coming from 200-300 dollar set up.
There must be a better way than those bigger, extra bases on those ST70s! I'm glad you are exploring PP design. This is where my switch to tubes started a few years ago with my Luxkit A3600. The great thing about buying a high quality kit-built amplifier put together by a dude in Japan in the '70s is that it motivates you to learn all you can about tube amplifiers to 1. make sure it is operating safely and 2. learn the circuit design and where the compromises were made. Luckily, it wasn't on the OPTs like the R8! Thanks to your channel and many others, I've enjoyed spending many hours learning as much as I can and yet I remain a noob, which means I've got plenty more learning to enjoy! I've learned what I needed to optimise the operation of my amp to a point where I have finally reached a level of audio nirvana I've not experienced before in my 25 years of solid state listening. So, thanks, Stephe, as you have helped me get where I am at now. I no longer have the urge to upgrade my amplifier or any other component now. I just want to be the guy that learns all I can about my lovely amplifier (and other gear) I have - there is plenty of learning still to do and I'm sure there are still more tweaks to do to squeeze out just a little more!
To me the fun is the learning. I've had a lot of different hobbies but the ones that stuck were the ones that were complex and basically were and endless learning curve :)
@@SkunkieDesignsElectronics - Absolutely agree! There is a pace of learning that can be addictive. When I started down this track, I was learning a lot quite quickly but now I'm getting to the parts of the circuit that are very complex (eg multiple NFB circuits) which need a level of understanding beyond me and most sources on the internet. It makes me appreciate the talents and intellect of amp designers in the '70s who designed my amp. But when my learning slows on one component I find myself shifting to another... so I have a busted Luxman preamp (transistor) and ES-level tape deck...
Huhu, really exited for that 300B. I was planning to build the current "budget 300B"..... Are you doing also a dokumentation on the "high ende 300B" like with the budget version for DIYers? Thanks so much
Basically, yes. But this takes it out of the "budget" build, as these transformers are gonna cost as much as the rest of the BOM. There may be some other minor changes as well, but yeah, it sounds so good I don't want to mess with it too much!
Make sure you see the update video on using the hammond power transformer. I also think I'm going to use a 7Vac for the 300B heaters to give the regulator a little headroom.
Thanks for your great work! I built my first 300B amp (AudioNote KitOne) some 25+ years ago and am building my third own project soon, a direct coupled 300B. The Kit One only was giving a glimpse of what a 300B can do.. So far, I had much better results with the 45 dc coupled. But you're right.. it can't be cheap, and it's not an easy project for a beginner (like me..)
Hi Stephe, thanks for the great monologue, there is a lot of information and food for thought condensed in there. As for the ST70 with integrated kitchen counter, lets hope that is not required for the magic of the sound. In other words, my vote goes to getting rid of that ridiculous base, or bottom... contraption :)
I think a wood base that is not quite so large might be cool looking though. I agree that the kitchen counter has to go though. Wood - think wood dashboard of high end luxury car verses the cheapo plastic dash on most.
It's easy to think... This is the BEST sound I've ever heard, but there are usually levels beyond (requiring more $$$ invested). Really hard to beat DHT amps with top quality output transformers. I agree, all SS I've heard can't touch single ended. Just a little hard to live with the low power. Trying a PP circuit with DHT tubes would be very interesting. Would some of the SET magic in the DHT remain or would I be wasting my time... Tubes4Hifi ST70 was one of my first DIY builds, but I went on to find single ended and never looked back.
The custom base for the ST-70 is a bit large-ish. Those kit chassis are too thin if you're going to start replacing electrolytic caps for film caps. To gain room for film caps, I've used spacers in between the chassis and bottom plate giving the interior depth an extra 1/4" - 3/8". It also provides for fresh air to enter the chassis around the perimeter at the bottom. Just make sure the gap around the perimeter won't allow curious finger tips to get in. Edit: Oops! I forgot the Dynaco chassis employ a not-so straight forward base plate to chassis mating. It might still work though.
I find that a major focus of high end manufacturers is to pay great amounts of attention to reducing vibration. That is why expensive components are extremely heavy.
Good for the original bottom cover. That ST-70 looks and sounds like a hack job. Which is why diy sometimes gets a bad reputation. This will be good. Looking forward to see it.
I'd chuck that base and install a slightly bigger inverted pyramid. When set down and stays standing .....a perfectly balanced amp! Plus you draw extra "pyramid power" as a bonus .....
Well, since you asked, I’d tell the person that sent the “ST-70” to come and take it back. You can buy a new chassis and all parts needed for a ST-70 at Triode USA.
Yeah. The last couple ST-70 builds I've done I just buy new chassis & parts. Forget all that overpriced 50-60 year old parts/chassis. New is cheaper vs many of these used prices.
@@SkunkieDesignsElectronics it usually is fun, but the one you’re showing looks like a complete overhaul and too much for me. Good luck, I’ve seen you take on AND fix stuff I couldn’t do. Love your channel.
Always enjoy all of your videos and projects. I have to agree with your assessment on 300B amps. While I wish there was a cheap way out those I have heard and liked were not inexpensive. I’m all in on the build of the ISO Tango transformers, some top end tubes (EML?), and a really sweet preamp circuit. BTW, were you on the build sheet for the Decware 945 speakers? How much longer as I am anxious to hear your thoughts, especially with the EML tubes.
The amp on your very cool splash screen appears to be the tubes4hifi ST120 which is a 60wpc amp built on a Dynaco ST70 chassis using KT88s, larger replacement power and output transformers and the VTA/tubes4hifi driver board. As to chassis ideas for the ST70, I'll send you a photo of what I did with my ST70 restoration. It might be fun to first do a completely stock restoration of the Dynaco 70 to get a taste of the original sound and then do your driver board and other upgrades.
If you have a freezer going down to nearly 0K in your basement it might work, but not frozen food temp, you are not even coming close to the temps needed to have any effect on the material, sry
@@volkerhauff6565 Its the swing in temperature that makes the difference rather than how far down. Possibly helps with the electron cloud formation thereafter.
Not to plow ahead, tweaks beyond VTA “stock” to consider, lower nfb resistor, 3-5k and, do a temperature compensation mod on that lm334 for the phase splitter… These are great amps. Get a bottom cover, or just do a new plate. They are ugly to start with, adding the cutting board makes it worse. Also, having “over”built your 300b with lundhal iron I can attest to the cost. I found the driver tube investment to also impact sound. Gotta get some of those new tubes…. Fun stuff
Are you considering building a 300B amplifier around a particular 300B tube? If so, check out the Takatsuki TA-300B. I just discovered this interesting tube yesterday while researching other 300B options. After reading several comparisons with other 300Bs, I noticed that you had compared a few as well. I took your advice and purchased the Horizon tubes, and so far, they’re performing well-I think they just need a bit more time to break in!
My DIY ANK L3 phono stage clone with the middle grade couplling capacittors (Miflec KPCU01 and AN copper foil), AMRG resistors and all Telefunken tubes with a pair of Cinemag 1254 SUT brown away my Rega US$6700 MSRP current top of the line phono stage. Now, I'm thinking of upgrade my DIY ANK L3 phono to a dual rail power supply having two seperate Bendex 6x5 tube rectifers and Telefunken ECL82 using to voltage regulators and two seperate Mundolf EVO oil filter caps similar to ANK L5 phono and put in the top notch Duelund CAST630 Cu/Sn film coupling caps.
When you do your 300b, try a Hammertone finish on the metal, it will look very cool with black transformers. What rectifier tube are you thinking of using?
For the bottom cover, you could buy one from Hammond for their steel chassis. Get one over sized and have a sheet metal shop cut it down to size for you. It would take them two minutes.
I know what you mean about the feeling you get when you finally stumble across "that magic". I have been playing around with Chinese clones of high-end solid state amps (they only clone amps that the original copyright/patents have lapsed). Last week I got a 'D9 Clone Dartzeel NHB-108' for around $800usd. The genuine item sold for $18,000usd back in 2005. This D9 clone sounds incredible - detailed but not sterile, nice tight bass and a genuine 130w per channel.
Steph, you do your hifi journey. But I am speaking from experience here having built a ST70 using all new production parts and can tell you that what you have there is a waste of time and money to make right. The only part worth saving/reusing is the output transformers. The new chassis are better than the old cs nickel plated ones. You will end up replacing everything anyway to make it right. So I would not do the trade. Your ISO opts are worth 3 times the value in that proposed trade. Just go buy a new production kit from tubes4hifi and build it right from the start.
I thought your camera analogy was excellent, and I’d be pleased if you do produce a higher end 300B design…without a doubt it’ll be better than much else on the market.
As a PSA, Stephe did not reach out prior to making a purchase on our site. The forthcoming mods to the ST70 were not sponsored but I do look forward to seeing the project and thoughts after it's completed. Obviously hoping for good feedback but will take constructive feedback as well! Keep up the great work as always.
100%, this was an out of pocket purchase, I wasn't looking for freebies and wanted to support another small business! I got this pair for what the output transformers would sell for on ebay, this kits was fairly cheap and if I get a working amp for under $500 outlay, including nice upgrade parts, that seems like a good deal to me!
My ST70 is completely rewired, recapped,etc., the Bob Latino version. The transformers are the only original big elements left. They are also the only part I worry about, because of those cloth wires that go into the transformers & are not really in good shape, discolored & brittle because of the repeated heating cycle. I fear that is where the amplifier will fail in future. If I had known you wanted to hear this amplifier I would have lent mine to you. Much easier than what it seems you are going to take on.
The ST-70...first tube amplifier i ever put a soldering iron to. I've done some tubes4Hifi projects & others. I like the $50 PCB Van Alstine Ultimate mod. Sticks pretty close to the original circuit too..but much better & dead quiet. Im actually almost finished building another Van Alstine ST70 right now..just trying to decide on a power cord & im done. I'm also trying out some Pacific Audio Magnetic output transformers. They were direct drop ins on the ST-70 chassis..fit like a glove. They told me they are exact clones thru & thru. But they were cheap...$270 for the pair b4 tax & shipping from California. Im very curious about them. I have original Dynaco A470's to compare them to. The VTA/Tubes4Hifi output transformer is an upgrade over the original & not too pricey at all. I also have a Dynaco PA-60 power transformer replicated by Heyboer i need to try out. I've used the "yellow sheet mod" with the rectifier & original power transformers in the past. I've never had an issue with overheating or had to replace a NOS mullard rectifier with the original power transformer & "yellow sheet mod". If you ask me, the ST-70 & all the mods out there are a great amp to work on/with. Look forward to your upcoming videos
Old Audio Amateur issue had the Dyna PSA 2 mod where the HV was regulated by some zener diodes. The sound was improved by regulation. Though it did not regulate the filament voltage. I stuck in two diodes instead of the rectifier tube. Regulation could be the secret to getting top end sound. Don't think the transformer was that great. Maybe modes to Dynaco tube equipment ultimately would be to regulate both the high and low voltages and/or improve the power transformers with a Torroid. Wonder if that is done by any of the newer after market PC boards and specialist companies.. Steve G was not impressed by the sound of an original Dynaco 70. Maybe regulation along with the Tango iron is the way to high end sound from your DIY amps. In the 70's, the best sound in the PAS 2 I had was the Telefunken 12AX7 followed by the Mullard 10M 12AX7 (their top gold pinned version). Wish I would have bought huge stocks, as they still seem to be one of the top tubes with a high price 40 years later.
I am going to send you my schematic to check out in your email. But I built a spare no expense 300B amp from scratch and it is amazing. I am using D3a for driver tubes, and LinLai Western Electric replica tubes cost like $400 and I A B'd them against a real pair of WE tubes and could not tell them apart. Very nice tubes well worth checking out. I ran AC heat on the D3as but I put Tent Labs filament supply boards for the 300B heaters. I have 106db speakers and you can not tell my amp is turned on its that quiet. No feedback. I am using Lundahl output transformers and Deulund cast copper coupling caps. (4.7uf for extended bass response). Another big improvement was I am using autoformer volume controls from Intact audio which was like lifting 2 bed sheets off my speakers. My power supply has a Lundahl transformer and Lundahl 10H chokes. 8uf and 100uf and .22uf film caps on each channel. Yes they are like soup cans. Resistors in the power supply are Caddock. Cathode bias with caddock resistors and film cap bypass. It cost me about $4k total including the chassis. I started out with electrolytics in the PS and resistive volume controls and lesser quality tubes and tweaked it as I could afford it. I am in love with this amp. Anyone interested in a schematic just let me know. I put alot of effort into making this as good as I could. I want to try some tango outputs on it but the rest I doubt there is much left I can do. I would highly recommend those LinLai Western Electric replica tubes to anyone with a 300B amp. They are fantastic. They say all materials were purchased from the exact same vendor that WE uses.
I'd have rid of that big footprint stand the amps sat upon and screw in some feet, allow some air under the chassis? But I'm no builder, i just like small footprint stuff...its outperforms it's size?
About the ST-70 I vote for "return to the classic form!" How modified can a classic be and remain a "classic"? The're just the chassis and transfos that's left from the origin.. And the little Dyna is a great little amp that deserves well treated. That base is ugly. Get rid of that, ;-) please.
Dump the old power transformer. The original does not have enough power. Plus and probably more importantly there's insufficient 6 volt heater voltage for a three tube board I was using the Triode Electronics board and it ran why too hot. In stock form, the ST-70 runs real hot anyway.
I really don't understand why you keep taking on extensive & costly projects, especially after you stated more than once you were done with these sorts of things? I do overall enjoy learning from you & the vast majority of your videos. I personally think these projects, especially this one, that I think borders on a weird mod. I have a standard updated ST70 & think that is the way to go & some of the other popular mods out there. I am more interested in your builds from scratch & still looking forward to more reel to reel videos. It is not my intention to be critical but, I think you should spend your time & talents in other directions.
Oh I'm not planning on trying to fix what is here. I have had a lot of folks asking about a ST70 and tossing a tubes4hifi board in isn't a hard deal and is under $300.
Great , looking forward to the 300b amp build 👍
You are spot on about the synergy - some stuff just dont jive with each other, no matter the price. Other times, you get those magic pixies to mash together so incredibly well that you cannot believe its coming from 200-300 dollar set up.
Keep up the great work, Steph.
Thank you!!
There must be a better way than those bigger, extra bases on those ST70s! I'm glad you are exploring PP design. This is where my switch to tubes started a few years ago with my Luxkit A3600. The great thing about buying a high quality kit-built amplifier put together by a dude in Japan in the '70s is that it motivates you to learn all you can about tube amplifiers to 1. make sure it is operating safely and 2. learn the circuit design and where the compromises were made. Luckily, it wasn't on the OPTs like the R8!
Thanks to your channel and many others, I've enjoyed spending many hours learning as much as I can and yet I remain a noob, which means I've got plenty more learning to enjoy! I've learned what I needed to optimise the operation of my amp to a point where I have finally reached a level of audio nirvana I've not experienced before in my 25 years of solid state listening. So, thanks, Stephe, as you have helped me get where I am at now. I no longer have the urge to upgrade my amplifier or any other component now. I just want to be the guy that learns all I can about my lovely amplifier (and other gear) I have - there is plenty of learning still to do and I'm sure there are still more tweaks to do to squeeze out just a little more!
To me the fun is the learning. I've had a lot of different hobbies but the ones that stuck were the ones that were complex and basically were and endless learning curve :)
@@SkunkieDesignsElectronics - Absolutely agree! There is a pace of learning that can be addictive. When I started down this track, I was learning a lot quite quickly but now I'm getting to the parts of the circuit that are very complex (eg multiple NFB circuits) which need a level of understanding beyond me and most sources on the internet. It makes me appreciate the talents and intellect of amp designers in the '70s who designed my amp. But when my learning slows on one component I find myself shifting to another... so I have a busted Luxman preamp (transistor) and ES-level tape deck...
Thanks
Yep. Same issue…lol but I learned some tricks.
Huhu, really exited for that 300B. I was planning to build the current "budget 300B".....
Are you doing also a dokumentation on the "high ende 300B" like with the budget version for DIYers?
Thanks so much
I already did for myself, basically by using high performance ISO tango iron in place of the original Edcor units.
@@SkunkieDesignsElectronics ah ok so its basically the same circut but with better output transformers? I mean the 300B you plan on building now
Basically, yes. But this takes it out of the "budget" build, as these transformers are gonna cost as much as the rest of the BOM. There may be some other minor changes as well, but yeah, it sounds so good I don't want to mess with it too much!
@@SkunkieDesignsElectronics thanks so much for the info :) your videos are great
Make sure you see the update video on using the hammond power transformer. I also think I'm going to use a 7Vac for the 300B heaters to give the regulator a little headroom.
Thanks for your great work! I built my first 300B amp (AudioNote KitOne) some 25+ years ago and am building my third own project soon, a direct coupled 300B. The Kit One only was giving a glimpse of what a 300B can do.. So far, I had much better results with the 45 dc coupled. But you're right.. it can't be cheap, and it's not an easy project for a beginner (like me..)
Hi Stephe, thanks for the great monologue, there is a lot of information and food for thought condensed in there. As for the ST70 with integrated kitchen counter, lets hope that is not required for the magic of the sound. In other words, my vote goes to getting rid of that ridiculous base, or bottom... contraption :)
"Integrated kitchen counter" LMAO!!! Love it.
I think a wood base that is not quite so large might be cool looking though. I agree that the kitchen counter has to go though. Wood - think wood dashboard of high end luxury car verses the cheapo plastic dash on most.
I was thinking maybe just add some wood sides (solid wood, maybe 1/2 inch thick) that extend slightly past the bottom and just leave the bottom open.
It's easy to think... This is the BEST sound I've ever heard, but there are usually levels beyond (requiring more $$$ invested). Really hard to beat DHT amps with top quality output transformers. I agree, all SS I've heard can't touch single ended. Just a little hard to live with the low power. Trying a PP circuit with DHT tubes would be very interesting. Would some of the SET magic in the DHT remain or would I be wasting my time... Tubes4Hifi ST70 was one of my first DIY builds, but I went on to find single ended and never looked back.
I always look forward to Monday's. Any plans for a DIY headphone amp, maybe OTL?
probably not a OLT but yeah I have plans :)
The custom base for the ST-70 is a bit large-ish. Those kit chassis are too thin if you're going to start replacing electrolytic caps for film caps. To gain room for film caps, I've used spacers in between the chassis and bottom plate giving the interior depth an extra 1/4" - 3/8". It also provides for fresh air to enter the chassis around the perimeter at the bottom. Just make sure the gap around the perimeter won't allow curious finger tips to get in. Edit: Oops! I forgot the Dynaco chassis employ a not-so straight forward base plate to chassis mating. It might still work though.
Yeah, I'm ditching all these huge film caps and doing a more traditional build that will be reliable!
I find that a major focus of high end manufacturers is to pay great amounts of attention to reducing vibration. That is why expensive components are extremely heavy.
Good for the original bottom cover. That ST-70 looks and sounds like a hack job. Which is why diy sometimes gets a bad reputation. This will be good. Looking forward to see it.
Yeah I could just throw this in the trash and start from new, but I like saving old stuff from the landfill if possible!
I'd chuck that base and install a slightly bigger inverted pyramid. When set down and stays standing .....a perfectly balanced amp! Plus you draw extra "pyramid power" as a bonus .....
oooh "Pyramid power"!!!!!
Well, since you asked, I’d tell the person that sent the “ST-70” to come and take it back. You can buy a new chassis and all parts needed for a ST-70 at Triode USA.
Yeah. The last couple ST-70 builds I've done I just buy new chassis & parts. Forget all that overpriced 50-60 year old parts/chassis. New is cheaper vs many of these used prices.
Something about fixing up an OG one seems fun to me :)
@@SkunkieDesignsElectronics it usually is fun, but the one you’re showing looks like a complete overhaul and too much for me. Good luck, I’ve seen you take on AND fix stuff I couldn’t do. Love your channel.
This isn't turning out to be that hard!
Always enjoy all of your videos and projects. I have to agree with your assessment on 300B amps. While I wish there was a cheap way out those I have heard and liked were not inexpensive. I’m all in on the build of the ISO Tango transformers, some top end tubes (EML?), and a really sweet preamp circuit.
BTW, were you on the build sheet for the Decware 945 speakers? How much longer as I am anxious to hear your thoughts, especially with the EML tubes.
Should be before the end of the year I hope!
@ Thanks for the reply, I will keep my fingers crossed for you 🤞.
So the Emission Labs 300b’s are a step up from the black treasure 300Z’s?
I have the Emission Labs 300b's but I like the Sofia's Royal Princess 300B's. The Royal Princess sounds much sweeter and well balanced.
yeah I think so by a good bit.
I have three different types of 45 triodes from EML and they are all amazing. EML tubes are crazy good.
The amp on your very cool splash screen appears to be the tubes4hifi ST120 which is a 60wpc amp built on a Dynaco ST70 chassis using KT88s, larger replacement power and output transformers and the VTA/tubes4hifi driver board.
As to chassis ideas for the ST70, I'll send you a photo of what I did with my ST70 restoration. It might be fun to first do a completely stock restoration of the Dynaco 70 to get a taste of the original sound and then do your driver board and other upgrades.
If you cryo treat the tubes by putting them in the freezer it makes the sound sharper.
If you have a freezer going down to nearly 0K in your basement it might work, but not frozen food temp, you are not even coming close to the temps needed to have any effect on the material, sry
@@volkerhauff6565 Its the swing in temperature that makes the difference rather than how far down. Possibly helps with the electron cloud formation thereafter.
Can your budget 300B amp with upgraded output transformers and 300B tubes get the magic sound you were talking about?
Absolutely!
Not to plow ahead, tweaks beyond VTA “stock” to consider, lower nfb resistor, 3-5k and, do a temperature compensation mod on that lm334 for the phase splitter… These are great amps. Get a bottom cover, or just do a new plate. They are ugly to start with, adding the cutting board makes it worse. Also, having “over”built your 300b with lundhal iron I can attest to the cost. I found the driver tube investment to also impact sound. Gotta get some of those new tubes…. Fun stuff
Are you considering building a 300B amplifier around a particular 300B tube? If so, check out the Takatsuki TA-300B. I just discovered this interesting tube yesterday while researching other 300B options. After reading several comparisons with other 300Bs, I noticed that you had compared a few as well. I took your advice and purchased the Horizon tubes, and so far, they’re performing well-I think they just need a bit more time to break in!
Check out the LinLai western electric replicas. I couldn't tell them apart from a real pair of We tubes. And they only cost like $3-400 pair
Would you consider adding VU meters to the 300B amp?
No I wouldn't.
My DIY ANK L3 phono stage clone with the middle grade couplling capacittors (Miflec KPCU01 and AN copper foil), AMRG resistors and all Telefunken tubes with a pair of Cinemag 1254 SUT brown away my Rega US$6700 MSRP current top of the line phono stage. Now, I'm thinking of upgrade my DIY ANK L3 phono to a dual rail power supply having two seperate Bendex 6x5 tube rectifers and Telefunken ECL82 using to voltage regulators and two seperate Mundolf EVO oil filter caps similar to ANK L5 phono and put in the top notch Duelund CAST630 Cu/Sn film coupling caps.
Go for it :)
@SkunkieDesignsElectronics Yes, I will.
When you do your 300b, try a Hammertone finish on the metal, it will look very cool with black transformers. What rectifier tube are you thinking of using?
5AR4
@@SkunkieDesignsElectronics Good choice.
For the bottom cover, you could buy one from Hammond for their steel chassis. Get one over sized and have a sheet metal shop cut it down to size for you. It would take them two minutes.
I know what you mean about the feeling you get when you finally stumble across "that magic". I have been playing around with Chinese clones of high-end solid state amps (they only clone amps that the original copyright/patents have lapsed). Last week I got a 'D9 Clone Dartzeel NHB-108' for around $800usd. The genuine item sold for $18,000usd back in 2005. This D9 clone sounds incredible - detailed but not sterile, nice tight bass and a genuine 130w per channel.
Steph, you do your hifi journey. But I am speaking from experience here having built a ST70 using all new production parts and can tell you that what you have there is a waste of time and money to make right. The only part worth saving/reusing is the output transformers. The new chassis are better than the old cs nickel plated ones. You will end up replacing everything anyway to make it right. So I would not do the trade. Your ISO opts are worth 3 times the value in that proposed trade. Just go buy a new production kit from tubes4hifi and build it right from the start.
It's not a straight trade, I just gave him some trade in value, basically what the output transformers sell for on ebay.
I thought your camera analogy was excellent, and I’d be pleased if you do produce a higher end 300B design…without a doubt it’ll be better than much else on the market.
As a PSA, Stephe did not reach out prior to making a purchase on our site. The forthcoming mods to the ST70 were not sponsored but I do look forward to seeing the project and thoughts after it's completed. Obviously hoping for good feedback but will take constructive feedback as well! Keep up the great work as always.
100%, this was an out of pocket purchase, I wasn't looking for freebies and wanted to support another small business! I got this pair for what the output transformers would sell for on ebay, this kits was fairly cheap and if I get a working amp for under $500 outlay, including nice upgrade parts, that seems like a good deal to me!
My ST70 is completely rewired, recapped,etc., the Bob Latino version. The transformers are the only original big elements left. They are also the only part I worry about, because of those cloth wires that go into the transformers & are not really in good shape, discolored & brittle because of the repeated heating cycle. I fear that is where the amplifier will fail in future. If I had known you wanted to hear this amplifier I would have lent mine to you. Much easier than what it seems you are going to take on.
Meh, I think this will be a fairly simply project
For that bottom cover .. duck tape fixes all 😜 it will look as good as those bricks they have now... Go classic for sure
The ST-70...first tube amplifier i ever put a soldering iron to. I've done some tubes4Hifi projects & others. I like the $50 PCB Van Alstine Ultimate mod. Sticks pretty close to the original circuit too..but much better & dead quiet.
Im actually almost finished building another Van Alstine ST70 right now..just trying to decide on a power cord & im done. I'm also trying out some Pacific Audio Magnetic output transformers. They were direct drop ins on the ST-70 chassis..fit like a glove. They told me they are exact clones thru & thru. But they were cheap...$270 for the pair b4 tax & shipping from California. Im very curious about them. I have original Dynaco A470's to compare them to.
The VTA/Tubes4Hifi output transformer is an upgrade over the original & not too pricey at all. I also have a Dynaco PA-60 power transformer replicated by Heyboer i need to try out.
I've used the "yellow sheet mod" with the rectifier & original power transformers in the past. I've never had an issue with overheating or had to replace a NOS mullard rectifier with the original power transformer & "yellow sheet mod".
If you ask me, the ST-70 & all the mods out there are a great amp to work on/with. Look forward to your upcoming videos
Old Audio Amateur issue had the Dyna PSA 2 mod where the HV was regulated by some zener diodes.
The sound was improved by regulation. Though it did not regulate the filament voltage. I stuck
in two diodes instead of the rectifier tube. Regulation could be the secret to getting top end sound.
Don't think the transformer was that great. Maybe modes to Dynaco tube equipment ultimately would
be to regulate both the high and low voltages and/or improve the power transformers with a Torroid.
Wonder if that is done by any of the newer after market PC boards and specialist companies.. Steve G was not impressed by the sound of an original Dynaco 70. Maybe regulation along with the Tango iron is the way to high end sound from your DIY amps. In the 70's, the best sound in the PAS 2 I had was the Telefunken 12AX7 followed by the Mullard 10M 12AX7 (their top gold pinned version). Wish I would have bought huge stocks, as they still seem to be one of the top tubes with a high price 40 years later.
I am going to send you my schematic to check out in your email. But I built a spare no expense 300B amp from scratch and it is amazing. I am using D3a for driver tubes, and LinLai Western Electric replica tubes cost like $400 and I A B'd them against a real pair of WE tubes and could not tell them apart. Very nice tubes well worth checking out. I ran AC heat on the D3as but I put Tent Labs filament supply boards for the 300B heaters. I have 106db speakers and you can not tell my amp is turned on its that quiet. No feedback. I am using Lundahl output transformers and Deulund cast copper coupling caps. (4.7uf for extended bass response). Another big improvement was I am using autoformer volume controls from Intact audio which was like lifting 2 bed sheets off my speakers. My power supply has a Lundahl transformer and Lundahl 10H chokes. 8uf and 100uf and .22uf film caps on each channel. Yes they are like soup cans. Resistors in the power supply are Caddock. Cathode bias with caddock resistors and film cap bypass. It cost me about $4k total including the chassis. I started out with electrolytics in the PS and resistive volume controls and lesser quality tubes and tweaked it as I could afford it. I am in love with this amp. Anyone interested in a schematic just let me know. I put alot of effort into making this as good as I could. I want to try some tango outputs on it but the rest I doubt there is much left I can do. I would highly recommend those LinLai Western Electric replica tubes to anyone with a 300B amp. They are fantastic. They say all materials were purchased from the exact same vendor that WE uses.
I'd have rid of that big footprint stand the amps sat upon and screw in some feet, allow some air under the chassis? But I'm no builder, i just like small footprint stuff...its outperforms it's size?
Your 300b will be point to point?
100% point to point
@@SkunkieDesignsElectronics Great, I would be interested to see the finished product.
Tubes 4 hi-fi have a st 70 cover you could use
He said they are out of stock right now sadly. Looks like another vendor might have one for sale!
Being a hobbyist is a great advantage you can be more objective
That is one messed up looking Dyco amp. I am building the 120 watt one that uses the KT88 tubes.
Wait till you see the inside lol
Go with the classic look, ‘cos those bases sure are ugly!
The box bases need to go. Find a bottom cover.
They are making a great work stand for them :)
About the ST-70 I vote for "return to the classic form!" How modified can a classic be and remain a "classic"? The're just the chassis and transfos that's left from the origin.. And the little Dyna is a great little amp that deserves well treated. That base is ugly. Get rid of that, ;-) please.
Base is going in the trash :)
Dump the old power transformer. The original does not have enough power. Plus and probably more importantly there's insufficient 6 volt heater voltage for a three tube board I was using the Triode Electronics board and it ran why too hot. In stock form, the ST-70 runs real hot anyway.
Hmm maybe to start with I can off load the heaters onto another transformer. I have heard the OG power transformers are problematic.
Dump the base.
A very interesting MM , 300b really gets the juices flowing eh , skunkie have you ever heard parallel se 300b or PP ?
No I haven't, this zero feedback SET is enough for me :)
I really don't understand why you keep taking on extensive & costly projects, especially after you stated more than once you were done with these sorts of things? I do overall enjoy learning from you & the vast majority of your videos. I personally think these projects, especially this one, that I think borders on a weird mod. I have a standard updated ST70 & think that is the way to go & some of the other popular mods out there. I am more interested in your builds from scratch & still looking forward to more reel to reel videos. It is not my intention to be critical but, I think you should spend your time & talents in other directions.
Oh I'm not planning on trying to fix what is here. I have had a lot of folks asking about a ST70 and tossing a tubes4hifi board in isn't a hard deal and is under $300.
lose the stand 😏