I got few nice tube buffers lying around, so i was thinking it would be nice to use tvc in between the buffers for gain and volume control.
Any good not too expensive tvc to test? Not finished assembled boxes, those are typically costly.
Any good not too expensive tvc to test? Not finished assembled boxes, those are typically costly.
Ok. Several monts ago I designed a buffer around a 8BU11 or 6BH11 compactron tubes with lots of gain (>300) but with strong negative feedback for a Baxandall tone stack. It has 4 loops: two of positive feedback and 2 of negative. If you are interested, I draw it and offer it tested.
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These things are expensive!
https://www.ebay.com/itm/285067315724
https://www.ebay.com/itm/255886567410
https://www.ebay.com/itm/285067315724
https://www.ebay.com/itm/255886567410
Still more than i am willing to invest for this experiment. I think i will go other way, just use line level balancing transformer like Mr. Nelson used in M2.
So it will be normal volume pot on input, buffer, gain with autoformer, buffer.
So it will be normal volume pot on input, buffer, gain with autoformer, buffer.
I'm lucky to have one of the older four-knob ones. It is thoroughly excellent. However, it shouldn't need to be buffered if the audio sources have reasonably low output impedance. The output impedance is quite low.
https://intactaudio.com/atten_FAQ.html
Try to search used S&B (Stevens and Billington) TX-102 TVC.
It was -originally- in Bent Audio TVC, in Music First, in Django etc.
I used it for more than a decade -in my CCS loaded #26 preamp- with satisfaction.
I also use Silk TVC. Almost as good as S&B.
I have Promitheus (very large nano core) AVC, but I haven't tried it yet.
The primary condition to use TVC/AVC the -relatively very small- source impedance.
If you can't guarantee low impedance source, the very large inductivity will be sound disappointingly.
It was -originally- in Bent Audio TVC, in Music First, in Django etc.
I used it for more than a decade -in my CCS loaded #26 preamp- with satisfaction.
I also use Silk TVC. Almost as good as S&B.
I have Promitheus (very large nano core) AVC, but I haven't tried it yet.
The primary condition to use TVC/AVC the -relatively very small- source impedance.
If you can't guarantee low impedance source, the very large inductivity will be sound disappointingly.
Thanks euro21, lots of good info, i will look into those.
Yes, i understand the importance of low signal impedance, thats why i plan on putting buffer before tvc/avc.
Relatively inexpensive edcor is in m2 used as step up. I think i will try that first.
Yes, i understand the importance of low signal impedance, thats why i plan on putting buffer before tvc/avc.
Relatively inexpensive edcor is in m2 used as step up. I think i will try that first.
I have been having great fun with edcor transformers, the ones used in m2 or vfet by Mr. Nelson. Wired as autoformer. It sounds great followed by the tube buffer. I have not done exact measurements, but it seems like it amplifies signal 5x on pin 7. It is less on pin 6, likely 3x. Yes, only two amplification steps.
Yes, it does not offer 24 steps...so one still needs volume control in some other place.
Important thing, its cheap, its available, does not require any complicated wireing, no multiple switches, and even more importantly, it sounds great.
If its good enough for m2 and vfet, you can be sure it sounds great followed by clean tube buffer.
I will do some measuring and report back.
Yes, it does not offer 24 steps...so one still needs volume control in some other place.
Important thing, its cheap, its available, does not require any complicated wireing, no multiple switches, and even more importantly, it sounds great.
If its good enough for m2 and vfet, you can be sure it sounds great followed by clean tube buffer.
I will do some measuring and report back.
Ok, more precise data. I applied 1kHz sine wave from tuner (sony 555 calibration tone), buffered through signal selector. Signal was exactly 1.0 V pkpk (382 mV rms) on the input of edcor, pins 1 and 3.
Output on pin 6 was 3.3 V pkpk (1.23 V rms).
Output on pin 7 was 6.1 V pkpk (2.26 V rms).
Not bad, free amplification.
I may measure distortion next.
Output on pin 6 was 3.3 V pkpk (1.23 V rms).
Output on pin 7 was 6.1 V pkpk (2.26 V rms).
Not bad, free amplification.
I may measure distortion next.