TVC Sound

Hi,

One problem is that if you use the TVC (any) with a piece of electronic that combines low output impedance with a limited value output coupling capacitor a very high Q tank circuit is formed with a resonance, depending on the capaitance, in the audio band.

If then the drive is from a current starved device (eg ECC82/83 cathode follower) without some feedback to damp this the interactions can be very non-pretty (all the way to periodic shutoff of the follower!), as they would be with any transformer as load.

Most Valve based Phonostages work fine into TVC's precisely because their fairly high output impedance sensibly damps the resonant circuit.

Ciao T

 

I think we should revisit at some point now the tx102 is slotted into the django. In addition I burnt in the tx103 stepups while I was on my "expedition" so those are ready to go as well! I am just waiting for the cables to come back from PMC (now 1m instead of 6!) and for the xbd stands to arrive and we are ready to rock. The bel canto dac is also in place. The only thing I plan to do is remove the tweeter diffraction grill. We might need to sound out the room again after all that!

Cant wait to hear your impulses!

I will be interested to see Mr T's measurements of his tx102. In my system the TVC seems to work very well - if anything it is better at lower settings and with the boost switched in. Surely it is simplicity itself compared to an active line stage?

I have heard the DA kondo setup and frankly it was very "nice" and I dont mean that as a compliment!

 

I wasn't talking about the whole Kondo System with LV's I was talking about the M77 with my power amps and my speakers. Different thing altogether.

 

Bring it over and convert me

 

Murray, I've heard the M77 with both BP and ART amps, both times it simply transcended the term hifi - it's a masterpiece. The M7 isn't so bad, getting a similar live feel for about 40% of the price.

 

Hi Brizon,

I don't feel the need to 'convert' anyone. You have to know the sound you want and then choose whatever it takes to get you there.

SM. I heard the M77 again last week with a much more modest power amp even than those. Same effect though!

 

Indeed - I was joking. Personally I am looking for accuracy.

 

Hmmm...

 

Lets see what thorstens measurements reveal

 

agreed, I can't tell which versions this unit has in it. I'm sure the ones he has will be just fine.

 

Can you detail how you got those measurements? I might be able to do some as well to give a wider sample. If I can blow the dust of the oscilloscope!

 

It does look very severe in your plots though - what are the time and amplitude scales?

 

The amplitude scale is 50mV per division. It's a 4KHz square wave. Almost one wavelength is being shown.

I just used a Sig Gen with 600 ohm o/p impedance, with 75cm of phono cable to the TVC. I've either had another phono lead going into the scope or into a socket with a 220K resistor across it and then the scope probes across that. Either way, it doesn't really affect the outcome.

Just have a go. You'll find the signal level chosen doesn't make much of a difference although getting the sig gen o/p level similar to that from a CD player might be the most realistic simulation.

Look forward to hearing what you find.

 

Im not very suprised by this.

The TVC has a case of being ''the emperors new clothes''.

It seems to me every year or so we get a brand new 'wonder-fi'.

All hail the new product.

Lo and behold its not perfect just like everything else out there.


I think its unique enough to warrant investigation by people after a new pre-amp, and I'm sure its a great solution for many.

 

Thorsten,

As you seem to be the man in the know....

Are the silver transformers supplied to Bent for their TAP pre-amp the same units as those used in the MFA? I was presuming they were less good as the Bent silver (Remote Controlled!) unit is considerably less expensive than the MFA one ie a little more than half the price.

http://www.bentaudio.com/index2.html

 

Folks,

Based on some private discussion with Murray, there is a good chance what he is measuring is indeed a pair of MKI Transformers. It seems that the Unit Murray has is in fact a "pre-release prototype" one off silver version made on request by the customer, prior to the Silver version being made available generally. And the coils in there may very well have been a few remaindered MKI silver ones.

We should know for sure later this week when I get around to do my own measurements.

What I would like to add however is that first round of DIY'er who used the TX-102 where commenting on the MKI TX-102 and it seemed that DESPITE the ringing (the very one Murray measures, the second 40-60Khz set of oscillation is a giveaway for a MKI) they subjectively sounded fine to practically all who tried them (there was one dissenter, but only one out of maybe 50 pairs sold early on).

I actually devised at the time a small external tweak that cleaned up the ringing no end, however in my own (102 MKI Copper) preamp it made the sound marginally worse, not better.

The bottom line was that because it LOOKED so bad (despite sounding good - anyway, ever seen the squarewave output from a CD Player?) the whole development progran that led to the MKIII was started, with the explicit aim to get the same good sound asbefore but with nice squarewaves at lower settings. And both MKII and MKIII Transformers do that quite well.

Ciao T

 

Hi,

For one, the units for Bent Audio are not shielded, which takes off around 25% of the cost. They also use a different winding style.

I am sure they are however made to similar standards.

Bent audio sells direct.

In effect Music First sells to dealers at prices similar to those Bent audio charges to the public. Those are the differences between distribution models.

BTW, while never officially announced, I think you can get the Music First PMP's with a remote control on special order for a fairly notional surcharge.

That of course with stepper motor actuated rotary switches, using relais for switching means in most cases a notable step down in sonics (mercury wetted reed relais actually sound better than most switches, but at around £10 each at last count before they got nixed by ROHS they where always out of competetition).

Ciao T

 

I haven't heard any ringing or strange timbres with my Cu TX-102 MKIII's - they're the most natural sounding attenuators that I've used to date. Here's an interesting post from John Chapman of Bent Audio regarding the "ringing" phenomenon with early TX-102s:
http://www.audiocircle.com/circles/viewtopic.php?t=9900&highlight=ringing

 

If these issues have been resolved and the unit I've borrowed isn't current spec (quite possible) then I'll be more interested to hear a new one. I do wonder how many users (or dealers!) actually knew there had been 3 iterations of this device.

 

I suspect they are system dependent - but given the price and performance a bit of a bargain.