Are there any good alternatives to the over-priced ST-70 ?
What other amps besides the Dynaco ST-70 had decent OPTs ? (and sell for half that price?! those st-70s are going for like $300+ easy, $400 on a good..er..bad day)
There were many in that era - Eico, Philco, Knight, RCA, etc... there's got to something else out there...monoblocks, integrated,..anything.. that could make a good worthwhile project.
What other amps besides the Dynaco ST-70 had decent OPTs ? (and sell for half that price?! those st-70s are going for like $300+ easy, $400 on a good..er..bad day)
There were many in that era - Eico, Philco, Knight, RCA, etc... there's got to something else out there...monoblocks, integrated,..anything.. that could make a good worthwhile project.
Pilot, Heath and Eico come to mind ... and don't forget that there are much better xfmrs available today and a plethora of great designs...wanna buy my ST-70?
When I first rebuilt an ST-70 you could buy one for $35 at Audio Exchange in lower Manhattan -- at these prices they are a better sale than purchase. I also found one in a dumpster in NYC.
When I first rebuilt an ST-70 you could buy one for $35 at Audio Exchange in lower Manhattan -- at these prices they are a better sale than purchase. I also found one in a dumpster in NYC.
I can't agree with the previous posters. IMHO the Dynacos have very good iron and are still a bargain even if going as high as $300. Where else can you get a decent tube amp for $300.00? If you then add another $150.00 to $200.00 to update the driver board and hardware you then have a great little amp for $500.00 or less. I think you would still be hard pressed to find a contemporary amp of like quality at this price. Not to mention the added benefit of owning a legendary classic that will continue to hold its value or appreciate. My modded Stereo 70 has cost me a total of about $350, sounds great and won't be losing any value any time soon.
There are a lot of good organ amplifiers out there that can be bought cheap. Wurlitzer made a 6SN7/6L6GT PP amp mono block that will blow away the Stereo 70.
I had a Dynaco stereo 70 and modded the heck out of it. I consider the transformers to be ok but nothing to write home about. Actually I consider a good set of Hammond transformers to be better than the stereo 70 transformers. I also don't consider the bass to be anything special. Its there but then again nothing special.
An ST-70 transformer bundle from Dynaclone, including power, output, and choke, is under $300. For that, you get transformers that are new, have cores which haven't deteriorated, wires with known good insulation (the cotton of the original Dynas is often brittle and uncertain) and have better performance and run cooler than original. For the restoration of an original, you need to replace driver, sockets, switches, and terminals anyway- the only cost adder for new is a chassis, and the old steel one is not particularly great and will generally need refinishing.
I'll put my money where my mouth is- I still have an old ST-70 here which I will trade to anyone in exchange for a new set of transformers.
The price of all vintage tube equipment has risen considerably... I saw a pair of 3W SE 6BQ5 amps made by 'Voice of Music' go for over $225 on Ebay.
back in 'the day' - a ST70 would go for $80-$120 depending on condition and tubes. I sold a rebuilt/modified '70 a few weeks ago for over $300.
The best bet it to buy singles of mono amps... it takes some patience but a few years ago I got a pair of Heath UA-1 amplifiers that way. Or consider just building from scratch on a bud-box. You could knock together an amplifier pretty cheap with some careful parts selection.
back in 'the day' - a ST70 would go for $80-$120 depending on condition and tubes. I sold a rebuilt/modified '70 a few weeks ago for over $300.
The best bet it to buy singles of mono amps... it takes some patience but a few years ago I got a pair of Heath UA-1 amplifiers that way. Or consider just building from scratch on a bud-box. You could knock together an amplifier pretty cheap with some careful parts selection.
SY said:
I'm pretty much with SY on this one, modern transformers and a Hammond chassis are probably the way to go. I sold a lot of upgrade kits for the ST-70 in the past, and thought at the time that the ST-70 offered a heck of a lot of value, but times have changed and it's not such a great deal any longer. Having grown up in the 1960/70's I find the revered status of the ST-70 a little puzzling, at the time the ST-70 was just about the least expensive option for a 70W stereo basic amplifier on the market, and all the rabid marketing claims by Dynaco aside there were (and are) far better sounding amplifiers out there. (Heathkit, Eico, and Scott Kit all offered amplifier kits that outclassed anything Dyna had to offer, and these even at significantly higher prices today might represent better value in the long term as they're not as quickly outgrown.) In automotive terms the ST-70 would be a ford falcon or chevy nova - very nice basic cars that got the job done, but didn't offer the performance or excitement of a Mustang, GTO or Charger.. (FWIW I like my Acura better than any of the classics mentioned..
)On a more serious note lots of people around here have designed great sounding PP amplifiers (search) and there are reasonable priced opts from Edcor, Hammond, and Electra-Print in addition to those mentioned that could form the heart of a new amplifier with great performance.
Other amps that I have found to be very reasonable and of really good performance are the ones made by Roberts/Akai that come in the the reel to reel decks. They are a nice set of mono blocks, usually around 5-8 watts with a wonderful SET sound to them. I have purchased 2 pairs off of ebay....they usually end up costing me around 40 bucks a pair including shipping.
They require just a little tweaking to get going....but (usually) sound great.
I think they are the "M" series....(ebay examplle)
http://cgi.ebay.com/ROBERTS-770X-4-...8QQihZ013QQcategoryZ15000QQrdZ1QQcmdZViewItem
They amps are easily removed...and are sometimes sold as mono block amps.
Wayne
They require just a little tweaking to get going....but (usually) sound great.
I think they are the "M" series....(ebay examplle)
http://cgi.ebay.com/ROBERTS-770X-4-...8QQihZ013QQcategoryZ15000QQrdZ1QQcmdZViewItem
They amps are easily removed...and are sometimes sold as mono block amps.
Wayne
kevinkr said:
no kidding, to name a few:
Sy's own "Red Light District"
Eli Duttman / Jim McShane "El Cheapo" (in name only!)
Poinz' "Music Machine"
the list goes on
If you don't have a well stocked "junk-box" it wouldn't be hard to spend more than $300 on all new parts for a P/P amp, but neither would it be particularly difficult to exceed the sonic performance and reliability of the original ST70.
thanks everyone for your thoughts on the subject.
I agree that instead of buying one for say $300+ and then throwing another $100-150 easily for component, board(driver) and psu upgrades,
it would just make sense to buy "new" reputable iron and build around it using a well thought of design that was drawn keeping audio quality in mind instead of a market happy price point.
chrisb, thanks for those designs you listed. that should be a good start.
I agree that instead of buying one for say $300+ and then throwing another $100-150 easily for component, board(driver) and psu upgrades,
it would just make sense to buy "new" reputable iron and build around it using a well thought of design that was drawn keeping audio quality in mind instead of a market happy price point.
chrisb, thanks for those designs you listed. that should be a good start.
percy said:
Percy:
I've personally built a couple of amps based on the El Cheapo topology (with allowances for the differences in the organ donor
chassis) It seriously embarrasses my Jolida 302 (EL34), for which I paid over $900 seven years ago.
http://www.decware.com/cgi-bin/yabb2/YaBB.pl?num=1126228937/630#630
This design is more of a topological template than a carved in granite design, and there's lots of latitude for output device selection and quality of OP iron. I think it's fair to say that Eli is a big fan of the DynaClone output transformers.
If you can find a pair of NOS or even gently used Mullard 12AT7s for the LTP/splitter, your ears will continue to thank you long after your wallet has stopped complaining.
The Dyna designs are price/performance champions and the Z565 may be the best of the bunch. You can spend less and get a noticeable performance fall off. Until you spend a LOT more, significant performance gains are not easy to come by. That observation is anything but original to me.
A nice thing about "El Cheapo" is that it works well with the inexpensive guitar amp O/P trafo, but fully exploits the capability of better "iron".
I am just curious...all the popular designs I found over here are mostly based on EL84/6BQ5 or 6v6/6l6. Not quite the case for EL34/6CA7. Is there a reason ? I mean it is supposedly more linear and powerful than EL84, yet there arn't very many well-known diy projects for it ? Whatever I found were triode strapped. Is it because of difficult implementation (power supply, output transformer and drive requirements) ? or is it that the EL84 is preffered over the EL34 in terms of sound ?
I see. As for linearity - I just simply looked at these specs for AB1 P/P mode around 300 Va for both tubes and saw that the EL34 produced twice the power with half the distortion. Also the Zout was quite a bit lower for the EL34.
Or is there more to it ?
http://tdsl.duncanamps.com/show.php?des=EL34
http://tdsl.duncanamps.com/show.php?des=EL84
Or is there more to it ?
http://tdsl.duncanamps.com/show.php?des=EL34
http://tdsl.duncanamps.com/show.php?des=EL84
Much more to it. Read the EL84 and EL34 Mullard datasheets- they are very complete, show all sorts of operating points and characteristics, pure gold.
edit: I think there are some typos on the EL84 datasheet you linked to. That may be the source of confusion.
edit edit: To paraphrase a famous Spanish swordsman, I do not think Zout means what you think it means. I think they mean the plate to plate load, not the tubes' output impedance. It's not a figure of merit.
edit: I think there are some typos on the EL84 datasheet you linked to. That may be the source of confusion.
edit edit: To paraphrase a famous Spanish swordsman, I do not think Zout means what you think it means. I think they mean the plate to plate load, not the tubes' output impedance. It's not a figure of merit.
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