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Re: Need some clarification...

Posted by Janos (A) on October 21, 2006 at 21:07:59

In Reply to: Need some clarification... posted by darkmoebius on October 21, 2006 at 12:07:38:

Hello,

Trannis don't have any "gas" like active components, there's nothing for them to "run out of" since they are only passing what the source feeds into them(minus core losses).

That was an euphemism from me.... you have the same feeling as you turn up the volume on an AVC or TVC, that you have when you accelerate and the car starts running out of gas...
The effect is more pronounced with the AVC. The sound gets thinner, the details fade, texture bleaches, soundstage shrinks, microdynamics disappears, macrodynamics compresses, and the rendering of complex music material gets confused, bass extension disappears at an alarming rate. From the ultimate, black background relaxed state at low volume level you get to the overstressed high volume setting.

However, this is all relative: these effects are less prominent in their case, than with an average preamp.

>Unless you are talking about core saturation or some overloading effect like within the TVC/AVC?

That was what I thought initially, but probably that is not the case. Now I run the AVC after the pre, and this means that the AVC is getting humongous signal levels (pre has a gain of 6), and I am attenuating from that with the AVC. Yet, the AVC has no problems with high signals, and turning the volume up does not produce the congestation and nasal, thin production.

One explanation for that could be that the much higher level (x6 amplified) signal generates much stronger magnetic fields, and the losses are not so critical, as in the case of 1-2V max signals. I'm racking my brains what could be occoring, but have no obvious explanation. However, it is not me who came up with this idea, of using the AVC after the pre. A tranformer winder (Denes Peter, DPA) with a lifetime of experience suggested it to me. He was the one, who wound the AVC for me.

>>The CD players could in theory drive an AVC/TVC, but I experienced they can't do it right. The problem could be that the inductance of the AVC/TVC varies with the frequency, messing up the DAC, and/or their HF junk reacts with the interwinding capacitances in the iron, messing up the sound beyond belief.

>This is a very interesting concept that I have never heard before. Have you, or anyone you know of, measured this effect? It might go a long way to explaining a few things. The only specs I've seen measured or published for TVC's is the relationship between impedence and frequency response.

That's just me trying to expain what I hear. I think someone should definitively go for it, and measure. The trouble is, that we should measure the CD - AVC/TVC interaction, and not a signal generator feeding a sinewave to the AVC/TVC. The signal generator is designed to send pure waves, and the real life CD players send all sorts of HF noise, that are in some kind of correlation with the signal. When the stepdown ratio is high, the added junk has less chance of messing up the sound. Can it be, that with the huge stepdown the phase of the HF noise is such, that it does not get transmitted?
I have not yet put together a comprehensive hypothesis about what is going on. Probably I will not do so, as I lack sophisticated gear to measure. (And my scope needs some serious calibration...;( )

>I'm actually in the process of building a fully-balanced version of John Broskie's Aikido amp (w/ a twist) into my TVC chassis. The twist is that I would like to use JRB's 6GM8 version so that the entire thing can be battery powered.(below). It will be switchable between active and passive.

Thank you for including the picture and schematics! I have heard good things about the Aikido, and I beleive one of my friends is working on building one. It has very low output impedance, should drive a TVC easily.

I'd suggest to try out, in addition to switching between active / passive, to put the TVC before the Aikido and after the Aikido. Listen to all configurations, I am curious of the outcome.
I do not know, if placing the AVC after the pre works better only in my system, or is it something universal.

Good luck!

Janos

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