Hi, maybe this question has been asked but I searched and couldn't find any information. Instead of a gainclone with a passive pre using a 10k Alps pot or ladder-type attenuator, would a variable resistance transformer work? I found this as an example called a vernistat:
http://www.paelectronics.com/vernistats.htm
Also variac.com sells variable output voltage transformers. Could they be adapted to variable resistance?
I just don't see why that silver rock(?) variable transformer has to cost $6,000 and why it couldn't be done DIY for cheap.
http://www.paelectronics.com/vernistats.htm
Also variac.com sells variable output voltage transformers. Could they be adapted to variable resistance?
I just don't see why that silver rock(?) variable transformer has to cost $6,000 and why it couldn't be done DIY for cheap.
Hi, only on computer for a minute so don't have time to find the link. I think it has to do with constant impedance, no coloration like resistors (carbon vs. tantalum etc), no popping like you can get from ladder type.
http://www.goldpt.com/compare.html
http://www.goldpt.com/compare.html
Okay here we go:
http://db.audioasylum.com/scripts/t.pl?f=amp&m=73673
Resistors=more transparent while scaraficing some bass, warmth, and dynamics
TVC=better dynamics, bass and warmth but gives up some transparency.
and:
http://db.audioasylum.com/cgi/search.mpl?forum=amp&searchtext=transformer+volume
Supposedly transformer pre-amps are better at low volumes and add some body as compared to resistors. I've decided the LM3875 chip amp is better than any "T" amp and will post Stereophile's specs on both in my other thread on this subject. But the LM3875 amp is said to need a tube pre-amp to "warm up" which I don't want to use. So the TVC would give a similar sound quality to a tube pre-amp. Installing in the same enclosure so don't think active pre is necessary.
http://db.audioasylum.com/scripts/t.pl?f=amp&m=73673
Resistors=more transparent while scaraficing some bass, warmth, and dynamics
TVC=better dynamics, bass and warmth but gives up some transparency.
and:
http://db.audioasylum.com/cgi/search.mpl?forum=amp&searchtext=transformer+volume
Supposedly transformer pre-amps are better at low volumes and add some body as compared to resistors. I've decided the LM3875 chip amp is better than any "T" amp and will post Stereophile's specs on both in my other thread on this subject. But the LM3875 amp is said to need a tube pre-amp to "warm up" which I don't want to use. So the TVC would give a similar sound quality to a tube pre-amp. Installing in the same enclosure so don't think active pre is necessary.
TVC or variac?
When you talk about transformer based volume control I understand a Tx with one (or two) primaries and multiple secondaries with different attenuation to achieve stepped voltage attenuation, like the famous Stevens & Billington's TX102 (info page not available for the moment). They are very good but expensive
and benefit from high Vout sources to blow your hat.
See, for instance:
http://www.bentaudio.com/index2.html
http://www.6moons.com/audioreviews/audiozone4/pretone.html
When you talk about variac I understand infinitelly variable Vout, but that must be noisy to achieve, I imagine.
Wich one are we talking about?
I have not tried resistor based passives, sorry.
Regards
Mauricio
When you talk about transformer based volume control I understand a Tx with one (or two) primaries and multiple secondaries with different attenuation to achieve stepped voltage attenuation, like the famous Stevens & Billington's TX102 (info page not available for the moment). They are very good but expensive
and benefit from high Vout sources to blow your hat. See, for instance:
http://www.bentaudio.com/index2.html
http://www.6moons.com/audioreviews/audiozone4/pretone.html
When you talk about variac I understand infinitelly variable Vout, but that must be noisy to achieve, I imagine.
Wich one are we talking about?
I have not tried resistor based passives, sorry.
Regards
Mauricio
Vernistat
The vernistat uses a resistive element to provide the voltages between the tap points on the transformer. Think about it- a transformer provides x volts per turn. Lets say x=2V. If you tap it at the fourth tun, you get 8V. If you tap it at the 5th turn you get 10V. How do you get 9.5V? That's where the resistive element comes in.
The vernistat is a means of making a transformer look like it can be tapped anywhere, even in between secondary turns.
It still has a resistive element, so if you believe such things are audible, then it won't be very good. It also has a bunch of wipers that you'll probably be able to hear also.
Maybe the price tag will make the resistive element and the wipers harder to hear. That seems to work with all sorts of audio parts.
I_F
The vernistat uses a resistive element to provide the voltages between the tap points on the transformer. Think about it- a transformer provides x volts per turn. Lets say x=2V. If you tap it at the fourth tun, you get 8V. If you tap it at the 5th turn you get 10V. How do you get 9.5V? That's where the resistive element comes in.
The vernistat is a means of making a transformer look like it can be tapped anywhere, even in between secondary turns.
It still has a resistive element, so if you believe such things are audible, then it won't be very good. It also has a bunch of wipers that you'll probably be able to hear also.
Maybe the price tag will make the resistive element and the wipers harder to hear. That seems to work with all sorts of audio parts.
I_F
Dear Chukky
http://www.bentaudio.com/index2.html (goto "DIY parts")
http://www.diyhifisupply.com/diyhs_sb_transformers.htm
http://www.diyhifisupply.com/diyhs_django.htm
http://www.mfaudio.co.uk/
See also Peter Daniel's thread about his gorgeous TVC (I couldn't find it)
Good luck
Mauricio
http://www.bentaudio.com/index2.html (goto "DIY parts")
http://www.diyhifisupply.com/diyhs_sb_transformers.htm
http://www.diyhifisupply.com/diyhs_django.htm
http://www.mfaudio.co.uk/
See also Peter Daniel's thread about his gorgeous TVC (I couldn't find it)
Good luck
Mauricio
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