sam_adams
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I'm guessing that the MC75 had a great deal of hand-wiring in it and the knockoff designs employ PCBs which are faster and cheaper to assemble.
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VTA ST-70 Review (Stereo Tube Amplifier)
- Thread starter amirm
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A real MC275 is $4500 for a current production model. $2500 is an awful lot to “wager” on something that might not work for long. If you are going to spend $2500, you might as well spend $4500. Both are serious outlays of cash. However, in this case you get what you pay for with one, and with the other you are taking a big risk.
DonR
Major Contributor
Ah! but what power cord did you use? 
NVM, I see that it uses a fixed cord. Clearly they are not serious about audio fidelity.
NVM, I see that it uses a fixed cord. Clearly they are not serious about audio fidelity.
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I was thinking that this was performing like a stereo guitar amp.
DanielT
Major Contributor
Thanks Amir, it was interesting!
Amir:
Again, the distortion is up by about 10 dB in relation to the genuine vintage Dynaco ST-70 amplifier.
Apart from the unique look of the unit, I'm the wrong guy to ask about the attractiveness of these tube amplifiers
For many nice/clean watts there are today good affordable class D amplifiers but tube amplifiers because it is fun and sound/HiFi history and then as a hobby. You can have more than one rig, HiFi system (class D amp in the main system, tube in the extra room, in the bedroom, the garage and so on). For tube DIY guys: Buy an original Dynaco ST-70 and freshen it up and if necessary replace the electronics in it (without changing the construction, if you are not a designer of amplifiers).
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Because it is cheaper to have a vintage tube amp to tinker with and listen to sometimes than to have a vintage car to tinker with and ride with sometimes.
Speaking of DIY.I'm not an EE or knowledgeable DIY tube guy, but for anyone interested:
Amir:
Again, the distortion is up by about 10 dB in relation to the genuine vintage Dynaco ST-70 amplifier.
Apart from the unique look of the unit, I'm the wrong guy to ask about the attractiveness of these tube amplifiers
For many nice/clean watts there are today good affordable class D amplifiers but tube amplifiers because it is fun and sound/HiFi history and then as a hobby. You can have more than one rig, HiFi system (class D amp in the main system, tube in the extra room, in the bedroom, the garage and so on). For tube DIY guys: Buy an original Dynaco ST-70 and freshen it up and if necessary replace the electronics in it (without changing the construction, if you are not a designer of amplifiers).
Edit:
Because it is cheaper to have a vintage tube amp to tinker with and listen to sometimes than to have a vintage car to tinker with and ride with sometimes.
Speaking of DIY.I'm not an EE or knowledgeable DIY tube guy, but for anyone interested:
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I am not put off too much by the measurements considering tube amps are like that. I guess if someone has tube amps as a hobby, I'm not "against it." I'm a guitarist, and even though I play with a Kemper digital amp, many amplifier "profiles" that the Kemper has are created directly from tube amps. Of course, tube guitar amps are built "for a sound," and not for fidelity. I can see the hobby appeal here. As as long as someone doesn't say, "tubes are better than transistors for high fidelity amps," I have no problem.
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Addicted to music
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DanielT
Major Contributor
Also, if you now have as a hobby to fix with old amplifiers why not recap and fix with one that has the potential to be really good.
Overall, I am happy to recommend the NAD 2200. I almost gave it the highest honors but given the upgraded nature of the test unit, and the fact that used amps may have issues, I avoided that. But you could have easily pushed me to give it the golfing panther.
audiosciencereview.com
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Although fixing with vintage tube amp has a different type of charm and why not, if you have interest and knowledge, do a technical cultural-historical work and:
Let the old pearl live on.
Overall, I am happy to recommend the NAD 2200. I almost gave it the highest honors but given the upgraded nature of the test unit, and the fact that used amps may have issues, I avoided that. But you could have easily pushed me to give it the golfing panther.
NAD 2200 Vintage Amplifier Review
This is a review and detailed measurements of a refurbished and upgraded NAD 2200 stereo amplifier. It was bought by a member, sent to QuirkAudio to be fully updated and then loaned to me. The work that Peter has done is exemplary. The inside looks brand new! I have repaired hundreds of...
audiosciencereview.com
Edit:
Although fixing with vintage tube amp has a different type of charm and why not, if you have interest and knowledge, do a technical cultural-historical work and:
Let the old pearl live on.
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DSJR
Major Contributor
Please may I suggest resurrecting the simulated speaker crossover loading for response tests (with 8kHz up held to 4-6 ohms or so rather than rising as I believe the original did?). Amps like this usually have a very high output impedance and into a typical modern 4 ohm rollercoaster speaker load, is going to act as a fixed 'graphic equaliser' as it tracks the impedance curve. Just so's anyone buying one of these things is aware of what these antique designs actually do...
Burning Sounds
Addicted to Fun and Learning
Nice to see another ST-70 tested. I built the Joe Curcio version, originally 30 years ago and more recently I rebuilt it into a new chassis as my original PCBs (poor quality - I'd never made PCBs before) were suffering from heat stress from the ECC88s. It wasn't built from Curcio's kit, but from the article in a 1989 edition of Glass Audio
The ST-70 is a wonderful little amp with excellent output transformers - at least the original US made and later Japanese made transformers were. I don't know about the quality of later clones. However, the power transformer was barely adequate even for the original 7199 configuration.
My Curcio ST-70 has been one of the most reliable amps of any type that I've owned. In its first rebuild it went for 20 years with only output tubes being replaced. The newer rebuild with a much larger Sowter power transformer has now been going for 10 years. That's way better than one of the Hypex modules in my multi-channel amp which only lasted 3 years before it failed (transistors).
Curcio's design is interesting as the bias, plate and screen grid are all regulated which to the best of my knowledge is quite unusual.
Here's a link to some measurements from a Curcio ST-70 that I posted on ASR a few years ago.
My original.
And my later rebuild.
The ST-70 is a wonderful little amp with excellent output transformers - at least the original US made and later Japanese made transformers were. I don't know about the quality of later clones. However, the power transformer was barely adequate even for the original 7199 configuration.
My Curcio ST-70 has been one of the most reliable amps of any type that I've owned. In its first rebuild it went for 20 years with only output tubes being replaced. The newer rebuild with a much larger Sowter power transformer has now been going for 10 years. That's way better than one of the Hypex modules in my multi-channel amp which only lasted 3 years before it failed (transistors).
Curcio's design is interesting as the bias, plate and screen grid are all regulated which to the best of my knowledge is quite unusual.
Here's a link to some measurements from a Curcio ST-70 that I posted on ASR a few years ago.
My original.
And my later rebuild.
These were used or to be used to connect to/power the Dynaco PAM-1 Preamplifier
Iin this picture, you'll notice the cable with the male end ...
Mono. You needed two for stereo...
Interestingly, it had an input for TV! ... Back then, circa 1955, when it was introduced.
A trip down memory lanes. My father assembled a ST-70 in the early 70's and later (early 80's) gifted it to me ... Much Later (88?) in my audiophile (phool) life, I purchased an ST-70 and for an all-tube system, using a Audible Illusion Modulus preamplifier with Magnepan Tympani in a small .. square room, 4 x 4 meters... I did enjoy it but knew I was missing a lot....r
Peace.
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Vict0r
Addicted to Fun and Learning
It looks great and I'm sure it'll sound enjoyable with a pair of semi-efficient vintage speakers. For those moments where you tan in the tube glow and focus on your whisky and cozy candle light, instead of on the minute details of reproduction and performance of your state-of-the-art Genelecs.
I voted "not terrible".
I voted "not terrible".
maty
Major Contributor
Review and Measurements of Dynaco ST 70
This is a review and detailed measurements of the vintage Dynakit Dynaco Stereo 70. It is on kind loan from a member who bought it used online and repaired it. Previous owner hand upgraded it but could not get it working. Given that it is 60 years old, one can forgive the rust and dust...
www.audiosciencereview.com
bloodshoteyed
Major Contributor
wow..love that thing, from the facedial to the cabinet design and the woodgrain itself
DanielT
Major Contributor
It was a gem. Mr. Carlson has an exciting Youtube channel.
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This would be really interesting if Amir tested:
Williamson amplifier - Wikipedia
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Normally when someone go and modify an existing classic design, he want's to do it for a reason, to improve something about it. Do we know what was Mr Latino goal or claim on this?
The frequency response curve (very good) do we know for which load it is?
The frequency response curve (very good) do we know for which load it is?
AndreaT
Addicted to Fun and Learning
It would power the dyna preamp, the PAM-1 if I am not mistaken. It is a connector derivative of an octal tube socket. My father had one for years back in the early ‘60s powering a home made mono amp with Westrex transformers.
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I had a Stereo 70, along with the Dynaco PAS-3X and FM-3. Replaced the Stereo 70 and PAS-3X with a SCA-80Q (Q = built in Dynaquad) and the FM-3 with an FM-5. All Dynakits.
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