Reduction into TVC issue

[Doc B.]

Yeow, I just wrote a big long conjectural reply and then saw that you corrected your post! That'll teach me to skip steps...

OK the issue is the same with all sources. I looked at the schematic of the active speaker. The input is differential (push-pull) - which is often mistakenly called balanced.  Obviously it is happy with all of your sources plugged into it directly so the issue seems to be the TVC not liking something ahead of it. The common "thread" is that SE to BAL cable.

So you probably need to adjust the wiring of the TVC. Once again, note that this is not my product and I am being asked to fix a circuit I haven't even seen. If you can't get an answer from the manufacturer the only alternative is to open the sucker up and figure out how it is wired. If it's point to point you might be able to take a really sharp close up photo and we might be able to figure out the input to primary connections. I'll also throw out that a replacing the TVC with a Quickie or even a Submissive could be a viable solution to the issue.

Possibly, getting inside the cable and disconnecting the shield from the RCA outer shell could solve the issue, but it might add noise. One possibility regarding the one cabel that seemed to work is that you might have had in intermittent shield connection that, when open, allowed the TVC to function as designed.

[undertowogt]

ok, this seems like it is worth a shot, if re wiring the TVC doesn't work I can easily put it back the way it was.

I am basically going to re wire the TVC INPUT and OUTPUTS to UNBALANCED JACKS correct?

I am not totally convinced that this will work but it is worth a try. I am thinking that it is an impedance issue, My TVC is not matched with my amp................ I might just have to buy a foreplay and some of your monoblocks     . but then I would need passive speakers.
attached is a pic of the inside of the tvc. 1 INPUT 2 OUTPUT:

Do I need to ground PIN 1 as well as jump it to PIN 3........................... or just jump PIN 1 to PIN 3?

thanks again for your VIP service, this is amazing

[undertowogt]

Just looking into the IMPEDANCE of my gear.

These numbers are quoted straight from the bottle head site the Yorkville site and the Promitheus site.

Bottle head - "The Reduction is designed to operate into line stages with 50K or higher input impedance "

Yorkville Sound - "Input Impedance 10k ohms , Input Sensitivity 1 Vrms"

Promitheus - "A TVC output impedance is always calculate from the equipment source, and is always lower than the source output impedance."

I am no where near an Impedance expert (obviously), but with my current reading seems to me this is why my sound is thin, and lacking bass.

The original cable that sounded great, full and loud still boggles my mind. If I could duplicate that result I would and be happy.  So with this information, do you still think it is a BALACED/UNBALANCEED issue?

[Doc B.]

I had hoped that maybe the transformers had labels that indicated the lead connections. You have mentioned two distinct issues. One is the lack of bass. This could be due to some impedance matching issue that seems to be related to having the TVC between your amp and any source you connect. The other issue you mentioned is low signal level from some combination of cables and gear that I am afraid I have lost track of. Low signal level could be due to the single ended to balanced cable grounding out half of the signal in certain conditions. The mystery cable that seems to work correctly has not been described in enough detail to tell us what is different about it. I have offered about all the advice that i can based upon knowledge of our phono preamp and the schematic of your amp, which seem to work properly with each other. We would need to see what the actual design and connections are on the transformer, the cables, etc. to be able to make any truly informed suggestions about why the transformer is changing the sound.

Asking the manufacturer of the TVC for guidance in using the TVC with single ended sources seems to be the most direct course of action at this point.

[Paul Joppa]

Doc B was posting at the same time, so some of the following is repeating his words in a slightly different way. Nevertheless, here are my comments:

There are two completely separate issues here:

1) As Doc B has said, but perhaps to clarify, a balanced cable has three wires (+. -. and Shield, sometimes called ground). A single ended cable has two (+ and ground). This leave a number of possible ways to interconnect with a cable. Balanced cables are wires with the Shield grounded at one end, or the other end, or both. The Shield may or may not be connected to the ground or the chassis or both, at one end or the other or both, in a SE-to-balanced connection. The Shield may be (at the balanced end) connected to the chassis shield, or the centertap (which may or may not exist). Each of these has different issues, so it is critical to determine how the cable is wired. Furthermore, a balanced input to the TVC might have the Shield connected to the chassis or the centertap of the transformer or to nothing at all. Again it is critical to determine how it is wired. I will further add that since two "identical" cables behave differently, they are not in fact identical.

2) The Reduction is optimal with a 50K load, but it can drive a load as low as 15K. 15K at 20Hz is 120 henries inductance. I can't find an inductance rating for the Promitheus TVC, so I can't usefully interpret the "10K impedance" specification - but if loss of deep bass is the source of "thinness" then a larger output capacitor will help. I would not go above 1.0uF because the distortion will increase and the gain will decrease, but that should take you below 10kOhms without other trouble.

[undertowogt]

Ok, thanks for all this help, I appreciate it very much. You guys went above and beyond on this thread.

[undertowogt]

Well issue is solved!! I was thinking about it (constantly). The TVC and REDUCTION worked perfectly with that one DIY Cable, yet the other DIY cable and other professional made cables DID NOT worK, they were thin and lacking bass. So I started to try to mimic that working cable.

form my understanding an UNBALANCED XLR to RCA had to be

RCA END

PIN 1 = Sleeve
Pin 2 = Tip

and on the xlr end

Jump PIN 1 to PIN 3

To solve the issue I wired the cable as above BUT DID NOT JUMP PIN 1 to PIN 3.

now it works perfectly, looks great, nice bass , nice amount of volume.......over all sounds great.

So I guess the "good' cable was miss wired some how, therefore producing the sound correctly

Was I originally wiring the XLR to RCA wrong by jumping PIN 1 to PIN 3? This is how I was instructed to do it.

thanks again for helping me trouble shoot this, impressive costumer service.

[Paul Joppa]

The standard RCA to XLR would have :

RCA end - tip to "hot", sleeve to both "cold" and "shield"

XLR end - "hot" to pin 2, "cold" to pin 3, and "shield" to pin 1

So the jumper pin 1 to pin 3 happens only at the RCA end.

Incidentally, this only works from RCA to balanced, not from balanced to RCA.