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VTA ST-70 Review (Stereo Tube Amplifier)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 125 63.8%
  • 2. Not terrible (postman panther)

    Votes: 46 23.5%
  • 3. Fine (happy panther)

    Votes: 16 8.2%
  • 4. Great (golfing panther)

    Votes: 9 4.6%

  • Total voters
    196

GXAlan

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Interestingly, Tim deParavicini showed me a cascode ECC88 circuit that got astoundingly high gain, using starved current operation (0.5mA). I didn't believe his performance claims so breadboarded it. And damn, he was right. Gain of 300, at 6V RMS out, H2 = -58dB, no detectable higher order.

Is that something you can put together in a format that will survive shipping to Amir? In the other Carver thread, I mentioned that I have a stash of JAN Sylvania 6DJ8’s that I can contribute. It would interesting to see how a high performance tube product with presumably pretty good tubes will measure.
 

SIY

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Is that something you can put together in a format that will survive shipping to Amir? In the other Carver thread, I mentioned that I have a stash of JAN Sylvania 6DJ8’s that I can contribute. It would interesting to see how a high performance tube product with presumably pretty good tubes will measure.
Why would I ship it to Amir, putting aside the issue of building a non-breadboard version?

My 6DJ8-oid phono preamp has terrific performance. Best tubes for distortion were CCa. Best for low microphonics were a rare 12V version made for Tektronix.
 

GXAlan

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Why would I ship it to Amir, putting aside the issue of building a non-breadboard version?

My 6DJ8-oid phono preamp has terrific performance. Best tubes for distortion were CCa. Best for low microphonics were a rare 12V version made for Tektronix.

Oh -- just to showcase the measurements more publicly? I vaguely remember seeing a blog post where your APx555 was a loaner and not something you have? I suppose with tubes any modern AP instrument will be sufficient to showcase the performance?
 

SIY

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Oh -- just to showcase the measurements more publicly? I vaguely remember seeing a blog post where your APx555 was a loaner and not something you have? I suppose with tubes any modern AP instrument will be sufficient to showcase the performance?
I have a 525 with every bell and whistle. More than good enough for any tube device, even the high performance stuff I’ve designed.

If I need better than 0.0004%, I am set up with some specialized gear, but honestly, the 525 is so ridiculously better than needed for audio that I rarely break it out.
 

GXAlan

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I have a 525 with every bell and whistle. More than good enough for any tube device, even the high performance stuff I’ve designed.

If I need better than 0.0004%, I am set up with some specialized gear, but honestly, the 525 is so ridiculously better than needed for audio that I rarely break it out.
That's awesome! Do you have any measurements from "your best" tube-powered gear to share?

If you have the interest, I'm happy to gift you a few JAN Sylvannia 6DJ8 tubes to see how they perform in a well designed circuit ;)
 

SIY

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That's awesome! Do you have any measurements from "your best" tube-powered gear to share?

If you have the interest, I'm happy to gift you a few JAN Sylvannia 6DJ8 tubes to see how they perform in a well designed circuit ;)
Better yet, I'll throw them on a jig I use for testing noise and linearity.

Here's a couple examples from my MM phono stage using the 12V version of ECC88/6DJ8. I'd have to do some serious digging to find my MC stage's measurements.
1660948026991.jpeg
1660948092771.jpeg


And a high voltage adaption using 12AT7 was discussed here. At 65VRMS out, 3rd was the only significant harmonic at -62dB. This will be the input stage for my next tube power amp.
 

JP

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JP

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Never saw those.
 

JP

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Yep assumed as much (x2). Lost to the labyrinth of ‘I’ll remember what I named that, and where I put it’? Went through that just yesterday. Again.
 
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I have recently built a VTA sound valves st70 kit and I was happy with the results. I had a gsi st70 back in the early 80s and I wanted to remember that sound. I have multiple amps and I can’t say it is the best amp but it is no where near the worst sound either. I have to say that it gives me pleasure to listen and I think it is a winner for this reason.
 
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