Now I know that the Dynaco ST-70 is not the end all be all in tube amplifiers and I'm sure its possible to build/buy a lot of products that do a lot of things better than the ST-70, but for what it is/does is the this guy about as good as it gets?
I've been reading here (and other places) for quite some time and am trying to nail down a nice sounding, 30ish WPC tube amp to try out on some 87-90 dB full range speakers I want to build. I'm not married to any one design/tube/topology, I'd just like something that can handle some lower efficiency speakers.
I just finished the Tubelab Simple SE which was a lot of fun and I'm really liking it, and it is going really well with my higher efficiency speakers but I've been bitten by the DIY bug and now that I'm finished with that project I want to try my hand at something else. I'm far from an expert so I'd need something that's not too terribly difficult. I've read lots of people really love the ST-70, especially with one of the many upgraded driver boards out there and I just want to know if I'm missing another option.
Now, I've never heard the Dynaco, but I do know that I'm not in love with the look so if I go that route it would be a clone built into another chassis but other than that, I'm open to anything.
Thanks in advance!
I've been reading here (and other places) for quite some time and am trying to nail down a nice sounding, 30ish WPC tube amp to try out on some 87-90 dB full range speakers I want to build. I'm not married to any one design/tube/topology, I'd just like something that can handle some lower efficiency speakers.
I just finished the Tubelab Simple SE which was a lot of fun and I'm really liking it, and it is going really well with my higher efficiency speakers but I've been bitten by the DIY bug and now that I'm finished with that project I want to try my hand at something else. I'm far from an expert so I'd need something that's not too terribly difficult. I've read lots of people really love the ST-70, especially with one of the many upgraded driver boards out there and I just want to know if I'm missing another option.
Now, I've never heard the Dynaco, but I do know that I'm not in love with the look so if I go that route it would be a clone built into another chassis but other than that, I'm open to anything.
Thanks in advance!
Hey bigjppop,
I asked a similar question last week, as my interests seem quite similar to yours. A couple project names kept surfacing (besides the myriad ST-70 options) for your consideration.
SY's Red Light District
TubeLab's soon to be offered Simple PP
Gingertube's Baby Huey
All look well respected and well documented from my limited reading.
I agree the ST-70 isn't much to look at, and I was thinking of piecing together my own from all the vendors on the internet, using a chassis of my own creation. If you go this route, I think it would be wise to select a driver board first, so you could optimize your parts purchases ( especially tubes) for that particular board, based on advice by the creator and that given here.
That's my take. I'm looking forward to reading others' advice here.
..Todd
I asked a similar question last week, as my interests seem quite similar to yours. A couple project names kept surfacing (besides the myriad ST-70 options) for your consideration.
SY's Red Light District
TubeLab's soon to be offered Simple PP
Gingertube's Baby Huey
All look well respected and well documented from my limited reading.
I agree the ST-70 isn't much to look at, and I was thinking of piecing together my own from all the vendors on the internet, using a chassis of my own creation. If you go this route, I think it would be wise to select a driver board first, so you could optimize your parts purchases ( especially tubes) for that particular board, based on advice by the creator and that given here.
That's my take. I'm looking forward to reading others' advice here.
..Todd
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My latest project is using a stock Dynaco ST-70 as the basis for a modern version. You can follow the build here: Wardsweb ST-70 Project
The above amps are a fair bit less than 25-30W.........
For 30W or so, I would consider PP Ultralinear EL34 or PP triode KT88.
My first project was Gingertube's Baby Huey. I built the original version (cap coupled, no mosfets) and it sounds great. It's in my office where I build amps, and I listen to it frequently with 86db speakers. Fine for the office, but it won't get very loud with 86db sens. I am planning on re-building it with the later mosfet/fixed bias mod, just have not got around to it yet. It sounds very nice in my main system with 90db sens speakers. When dialing in this amp, I put a pot and a fixed R in series to vary the feedback a little bit; a great quick experiment to listen to the effect feedback makes.
IIRC, the Baby Huey is UL (around 10-11 watts) and the Red Light District is Pentode (around 15W?), so RLD will put out a few more watts.
I've also breadboarded and built a couple of iterations of Poindexter's EL34/6GK5 music machine, and it also sounds very nice, although I have not had one put together long enough to really compare it to anything else. It's a fixed bias triode EL34 with a CCS for the 6GK5 and puts out around 12-14 watts. I really like this design because it is a simple, two stage triode with fixed bias and a CCS and no feedback.
I am contemplating using trioded 6550's/KT88's in Poindexter's EL34 MM as a next step, as I am a semi-newbie as well and it should be good for some additional hands-on training. I imagine that this would yield around 25-30 watts of PP triode, without feedback in a 2 stage design.
There is also Triode Dick's Bill and Mono Bill that should have the watts in a triode KT88 design, although I have not seen much discussion about this amp.
If anyone has a good schematic for any other KT88 PP triode please point me to it.....
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Thanks for all the responses so far. As far as budget, 500-700 is roughly where I'd like to be. I'm not hard and fast here, but I can't afford a 2000 project but I don't need to go dumpster diving either.
The EL84 based amps all look very interesting and I've explored them pretty thoroughly before but they are somewhat limited in the power department. I've seen Tubelab talking about making his Simple PP into monoblocks which should give me the power I want but then I'd need to build two.
The SET 845/211 sounds great in theory but I have yet to see a design that is newbie friendly and I'm also fairly confident that that type of project would get expensive in a hurry. Please advise if I am mistaken on either of these points.
As Boywonder mentioned, I think either a UL PP EL34 design or a PP 6550/KT88 in triode mode would probably be the most bang for the buck and the easiest thing to handle at my skill level.
So, that brings my back home again... UL PP EL34 sounds strangely like the ST70 and again, like Boywonder, I haven't seen much discussion on a 6550 based triode project (but I'd love to!).
The EL84 based amps all look very interesting and I've explored them pretty thoroughly before but they are somewhat limited in the power department. I've seen Tubelab talking about making his Simple PP into monoblocks which should give me the power I want but then I'd need to build two.
The SET 845/211 sounds great in theory but I have yet to see a design that is newbie friendly and I'm also fairly confident that that type of project would get expensive in a hurry. Please advise if I am mistaken on either of these points.
As Boywonder mentioned, I think either a UL PP EL34 design or a PP 6550/KT88 in triode mode would probably be the most bang for the buck and the easiest thing to handle at my skill level.
So, that brings my back home again... UL PP EL34 sounds strangely like the ST70 and again, like Boywonder, I haven't seen much discussion on a 6550 based triode project (but I'd love to!).
Well, you would get like 10watt more, but probably at the cost of quality, AND it still cost more money
I remember someone stated that ST35 sounded better than ST70
Its a subjective statement, and amps are different, but it wouldnt surprice me
Not sure, but was there talk about making Simple PP into 4-tube monos
I remember someone stated that ST35 sounded better than ST70
Its a subjective statement, and amps are different, but it wouldnt surprice me
Not sure, but was there talk about making Simple PP into 4-tube monos
I think I missed what you're referencing here in the first sentence.
I had also heard about the mono Simple PP which could be very interesting as well.
I referred to EL34 PP or KT88 PP vs EL84 PP
At first I too was a bit surpriced that Simple SE wasnt turned into Simple PP monos
But now Im quite happy that George decided in favour of EL84 PP
That looks very interesting but maybe a little much for a newbie to handle. With 8 tubes per channel it sure would be fun to look at!
Since your the designer of this bad boy, what do you think; suitable for a beginner?
Not sure if this is too complicated for your requirements, but I have been investigating a 30 watt PP amp too, using 6L6 or similar with mosfet source followers. An enormous amount of support was offered in this thread http://www.diyaudio.com/forums/tubes-valves/133034-6l6gc-ab2-amp.html , especially by Tubelab. The final design uses the topology Tubelab is going to have in his (yet to be produced) driver board.
I am hoping to begin construction of this amp very soon. Have all the bits, but workshop space and available time are constraints.
Here is the latest schematic if interested...
I am hoping to begin construction of this amp very soon. Have all the bits, but workshop space and available time are constraints.
Here is the latest schematic if interested...
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This looks to be a very interesting project and so far, I've been nothing but thrilled with Tubelab products and the fantastic knowledge/support offered on this forum. This might be the way to go, especially if Tubelab is going to produce a board.
Obviously no one has heard/built but I know a lot of people love the 6l6 family of tubes and they're pretty dang cheap to boot!
Just looking over the schematic, are those pretty, glowing, tubed voltage regulators I see?
This looks to be a very interesting project and so far, I've been nothing but thrilled with Tubelab products and the fantastic knowledge/support offered on this forum. This might be the way to go, especially if Tubelab is going to produce a board.
Obviously no one has heard/built but I know a lot of people love the 6l6 family of tubes and they're pretty dang cheap to boot!
Just looking over the schematic, are those pretty, glowing, tubed voltage regulators I see?
Yes, they are voltage regulator tubes. They are not required for the project, but I just felt like using some for fun and eye candy ;-)
Remember, though, that's just a limitation in the deep bass. In the midrange and treble, you can probably do better. And even within the 30W, triode will give lower source impedance and lower transformer distortion. The MOSFETs obviate any significant Miller rolloff.
back to basics
I've owned a ST70 since 1970. It was built by a minister in 1961. He sold it to become a missionary. It still works. It has gone wimpy at times and needed new tubes or filter caps, but it has never exploded, quit, or been damaged. I've hauled it to church twice weekly to do cantata backup with, I've moved 3 times. No problem, no shorts. I have been through 3 sets of speakers that eventually lost their tweeters, the ST70 soldiers on. I've worn out 5 or 6 phono diamond tips, two turntables, multiple CD players with bad controls, 5 or 6 tape decks, many tuners have lost their controls. The ST70 still sounds fine. Power is down a little bit due to the 1974 filter caps, but all the stuff is still available and I won't have to make a 4 gang filter cap out of Atom-lytics and tie wraps and heat shrink like last time, they are making exact replacements again. Due to the internet there is all kinds of support. Somebody is selling the chassis, transformers, and full kits again, both original and modified. Getting the last 1/2% of distortion out of an amp strikes me as being a little silly, when speakers have distortions in the teens and twenties of percent. I still want a pair of AltecLansing Voice of the Theaters, or maybe a pair of Klipshhorns, but that train has left the station and I'll have to make do with a pair of Peavey speakers. They don't even have speaker demonstration rooms anymore, the last time I was in one (circuit city, RIP) the room had 5 sides, no sound baffling, and a car amp buzzing the boomers in the corner.
I've owned a ST70 since 1970. It was built by a minister in 1961. He sold it to become a missionary. It still works. It has gone wimpy at times and needed new tubes or filter caps, but it has never exploded, quit, or been damaged. I've hauled it to church twice weekly to do cantata backup with, I've moved 3 times. No problem, no shorts. I have been through 3 sets of speakers that eventually lost their tweeters, the ST70 soldiers on. I've worn out 5 or 6 phono diamond tips, two turntables, multiple CD players with bad controls, 5 or 6 tape decks, many tuners have lost their controls. The ST70 still sounds fine. Power is down a little bit due to the 1974 filter caps, but all the stuff is still available and I won't have to make a 4 gang filter cap out of Atom-lytics and tie wraps and heat shrink like last time, they are making exact replacements again. Due to the internet there is all kinds of support. Somebody is selling the chassis, transformers, and full kits again, both original and modified. Getting the last 1/2% of distortion out of an amp strikes me as being a little silly, when speakers have distortions in the teens and twenties of percent. I still want a pair of AltecLansing Voice of the Theaters, or maybe a pair of Klipshhorns, but that train has left the station and I'll have to make do with a pair of Peavey speakers. They don't even have speaker demonstration rooms anymore, the last time I was in one (circuit city, RIP) the room had 5 sides, no sound baffling, and a car amp buzzing the boomers in the corner.
So far, all the posters have forgotten the 7591. "Idiots", like Fisher and Scott, took advantage of the type's ease of drive and there's nothing preventing today's builders from following in their footsteps. Small signal circuitry that works with EL84s and 6V6s works with 7591s too. Use whatever style tickles your fancy.
Check the 7591 data sheet out. Notice the "fixed" bias UL conditions set. A very nice 32 W. from a PP pair that needs only a little loop NFB to bring full power distortion down to an inaudible 0.3%
May I immodestly suggest an "El Cheapo Grande"? The 12AT7 based splitter/driver sounds good and it's well up to the task at hand. I leave PSU details to you, but the Edcor model CXPP60-MS-6.6K seems a quite suitable O/P trafo and it's $70.30 price is favorable.
Use whatever style tickles your fancy.Check the 7591 data sheet out. Notice the "fixed" bias UL conditions set. A very nice 32 W. from a PP pair that needs only a little loop NFB to bring full power distortion down to an inaudible 0.3%
May I immodestly suggest an "El Cheapo Grande"? The 12AT7 based splitter/driver sounds good and it's well up to the task at hand. I leave PSU details to you, but the Edcor model CXPP60-MS-6.6K seems a quite suitable O/P trafo and it's $70.30 price is favorable.
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