TVC Sound

Thast what I thought he was trying to say but the harmonics thing was a bit misleading.

I doubt CD or vinyl can put out a 4 khz square wave so I am not unduly worried. It stil sounds better than the vibe after all!

 

But it seems to be some way short of accuracy, which I thought was your thing. Seems in fact that you like a bit of distortion.

-- Ian

 

Its accurate within the source bandwidth. The measured distortion accross the audio band is very low.

 

Yes but that isn't possible in reality. Take your own amp which uses a combination of SM technology and a tube OTL output stage. I bet you could pick plenty of holes in the spec (OTLs measure abominably) but I bet it sounds excellent

Vinly replay can have distortion of 3,4, 5% plus but we enjoy it.
Speakers distort horribly. Measure the distortion of a typical 8" bass`driver playing bass guitar at anything like a reasonalbe volume and you'd be horrified.

 

At least the TVC has no TIMD!

I presume ;-)

 

If you like the 'sound' of these transformers then by all means carry on using them. However, I'm far from convinced that they are the best way to deal with line level signals.

Please don't try to insist that they are somehow more accurate or correct than any other type of pre-amp though. I just don't think its the case.

I'll be interested to see what results Thorsten produces.


I must admit that I'm quite surprised these characteristics haven't been picked up by more 'professional' reviewers. (Actually given the competence and abilities of most reviewers, perhaps not) I know a few people here have expressed reservations about them, and kudos to them for trusting their ears & systems.

 

Low compared to what? Since you haven't done any comparative measurements for all you know your TVC may measure well below average in this regard.

You like how it sounds, which is fine, but if these measurements are correct, it's very far from state of the art.

-- Ian

 

Come on now, they may not look too pretty in producing a true (or as close as possible) square wave but I would think from my listening to them that they must measure very much better than other active pre's in other respects.

I suppose the fact remains, though, that I do use a purely digital system so unless I played a DVD-A or SACD (which I don't) I would not be hearing much of that ringing.

It makes me think of these Manger drivers I am looking at. They measure far, far superior to conventional drivers in some aspects like step response (speed, if you will) and phase but do have higher THD than most. Which factors make less of a compromise is up to you to decide.

Those measurements were done on 24dB attenuation.

I tried to do the AM cores but couldn't figure out how to wire them up with no explanation of what labels on the wires mean!

I’ll write to my friend at Ypsilon electronics and see if he would take a similar measurement of the tansformers in their £20K+ passive (switchable active gain) pre-amp.

 

Ok Here's a 4khz square wave by a waveform genny



Here's a 10khz waveform the same way




Here a 4khz generated by a £2.2K active pre amp




And here's the 10khz wave sorry about some of the pics, I'll do more tomorrow.

 

Come off it dude, there's no way you can tell how well something measures just by listening to it. It may just be that you prefer a certain kind of distortion, so you prefer the TVC. Comparative measurement is essential to prove good engineering.

-- Ian

 

Your ears are the final test period, to mine the tvc doesn't cut it, but then I'm odd (as I keep being told :lol: )
PS the attenuation on the test was 68db, even at max vol 120db on the read out, there was no Visable difference to the wave form

 

Folks,

I checked myself. As it so happens, I found out that getting decent closeups of my Velleman Digital 'scope LCD screen with that cheap digicam we have since the wife broke the good one is hopeless.

What I did was as follows:

1) Unloaded Transformer (so, basically just 1M//100pF from the 'scope) which is worst case.

2) Generator with 600R Source, 4200Hz squarewave, perfectly square.

3) Step down from 0db all the way so where the 'scope stopped locking.

I observe first that when fed from the generator interactions between generator and TVC caused a notable overswing on the leading edge of the squarewave on the in put signal to the TVC. Sorry, it is a very cheap generator and seems to dislike capacitive loading.

Second I noted that there is a fundamental resonance mode which is at around 50-55KHz and is around 20 -26db down at volume settings below -20db, its notably further down higher up.

I also noticed that a further single cycle of a higher mode was added far down in level, around where Murray measured.

HOWEVER (and this boils my noodle big time) this overswing is only present on the negative going cycle and not every cycle, but around every eigths cycle ONLY (the other seven squares looked okay).

That cannot really be a resonance mode in the transformer I would say. I have never before seen something like that, it may be an artifact from the sampling in the digital 'scope, cannot really say.

BTW, I have done some work previously on the MKI to use external snubbers to kill the resonance (and it did so beautifully) but somehow it sounded worse snubbered than without.

The resonances are no worse than those on some valve amplifiers.

Make of it what you will, but remeber, 4KHz squarewaves do not exist in recordings.

Ciao T

 

I couldn't have put it better myself Murray.

I do hope this makes the TVC brigade back off with their ridiculous claims of neutrality and accuracy - it's "inventor" being the worst offender on this forum and others.

Thank you so much for providing the evidence to back up what a number of us have been saying for some time.

 

Hi,

Your perogative.

They are, where harmonic & intermodulation distortion are concerned.

And let's not forget, ANY DIGITAL SOURCE that uses oversampling rings as much or worse, as Simons measurements of these show.

So, by the same definition state of the art audio cannot come from digital sources using digital filtering.

Ciao T

 

Out of interest, how much high frequency extension do you get from a good record player? I know a lot of the carts go up to about 40-60KHz but what bout in practice from a good condition record?

 

A bold claim. Has anyone put this to the test?

 

Hi,

It is worth revieweing the beginning of the thread....

There are many areas where a TVC is measurably superior to pretty much anything else out there. There is one are where it is worse. Choose your poison. What Murray has is notably worse than what I have in my system for measurements, yet:

"I have heard better, more natural sounding, active linestages although not perhaps at this price level."

That is in the end the rub. I am sure with sufficient extra expense the measurements can be made even better.

In the end I think the final arbiter are everyones ears. Mine still tell me that I cannot tell the Music First Preamp realiably apart from a bypass, sonically speaking.

Ciao T

 

Hi Thorsten,

a few interesting points there

Interactions between the generator and the TVC. Might not a cd player also have the same problem?

-20 dB attenuation? I couldn't stay in the room with it that loud. I was using it at -37 or -34 and it was ringing alot worse down there.

I'd agree with your comments about 'some' valve amplifiers but none of the ones I'd choose to listen to would ring like this.

4KHz square waves aren't music but convincingly reproducing the timbre of acoustic instruments and female vocals means (in my experience) that the far more complex harmonics at widely varying amplitudes that do exist in music need to be handled with a great deal of care and I can't really see how overlaying them with these types of resonance can help with that. Maybe I'm too fussy?

One of the odd things about this is that people are used to components getting worse as they try to play louder. It's almost counter intuitive for them to get worse the quieter they play. Might as well use the digital volume control on your cd player!

 

They dont appear to have a sound thats the point. I suspect many more people are happy with them than have expressed reservations, and for good reason - they sound great! It puts the vibe to shame on both counts!

I beleive IM distortion is the most important kind anyway - or other less quantifiable time distortion issues.

SSB - I have seen measurements in the mags and they measured very well.

A true 4khz square requires infinate bandwidth and slew rate - music doesnt. Its not the same thing.

 

That's tosh. Simon's measurements showed that bandwidth limiting a square wave gets you regular ripples. Which isn't surprising as a square wave, by definition, requires infinite bandwidth.

The measurements show that transformers can resonate with out-of-bandwidth input. This is also completely unsurprising. It only matters if you have RF on the input and the resonance is audible. The former may be supplied with a NOS style DAC (for example) the latter remains unaddressed.

Conversely Tony's photos upstream seem to imply that a 35MHz bandwidth is necessary for audio. Which is also misleading. IMO an audio amp that doesn't introduce ripples on a 4kHz wide bandwidth square wave is poorly engineered.

Paul