At last: DIM TVC!

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maxlorenz

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At last: DIM TVC!
« on: 23 Nov 2004, 11:17 pm »
Dear John:
Months ago I built a DIM (do it myself) TVC with TX102 MKIII (remember we have some little problem? :lol: ) ; one RCA in/one RCA out. Unfortunately one of my Monarchy Audio's SE100delux Class A mono amps Kaput! I had to wait all this time for the parts to arrive. Finally, I managed to repair it five days ago and obviously I connected them to my pre.

Firts impressions were similar to everything that has been said about them: VERY TRANSPARENT AND DETAILED, with acoustic instruments sounding very real and uncoulored; fast responses; very extended HF although my amps have "only" 33Kohm/1.7V at input; voices, both male and female, are breathtaking (class A amps). The bad news is that it sounded a bit thin and light, without bottom end. Cold, I might say.     :(

I let them playing constantly, by day, and the sound is improving: music is rounder, softer, more laid back, but retains its detailed presentation (very hard to explain). LF armonics are a bit better and LF extension is decent now and very controled. I changed a DIY IC based on DH Labs Pro-audio cable (silver/copper) for a $1 copper IC and what is lost in resolution is gained in warmth (IC from DAC to pre is PSAudio Statement wich is a "fat" sounding cable). My view is that silver is not good for this pre (at least in my system).
I think that maybe the TX weren't "burned-in" as I had to wait for a shipment from England due to lack of stock.    :?:

If I ever get great bass (burning-in; changing cables or amps) this pre will be unbeatable!  :mrgreen:    The immediacy it brings to the records is outstanding       :beer: . This explain why it is so hard to comme back to active pre. Who would accept all this extra noise from an active stage?

A question arrises: what to do with the unused "+6db" primaries?

Also, I have "floating" ground at input and at output. I checked once with output grounded and I didn't hear any change. I will try again.
I also tried reversing input polarity but only got noise.

I'm trying to build a 4 channel classD amp with UcD180 modules from Hypex.nl. I hope everything goes OK to power speaker in active way.  8)

Thanks, John.

Mauricio

John Chapman

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At last: DIM TVC!
« Reply #1 on: 24 Nov 2004, 12:10 am »
Hello!

Glad it is alive! As for the questions:

1- You can just tape off the +6db lead.  BTW though - Do you have ++,--,+,- primaries (4 primary wires?)

2- If you are floating both the inputs and outputs then you are the menber of a very small club! I have never used a system that was happy floating the outputs - I always get hum if they are not conntected to the chassis ground point. The input ground can be floated much of the time it too sometimes needs to be connected to the central ground point.

In any case just connect grounds to minimize hum with the level turned up quite loud and no music playing.

Please keep me posted and let me know if any other questions come up.

Many Thansk!

John

maxlorenz

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At last: DIM TVC!
« Reply #2 on: 24 Nov 2004, 12:22 am »
Hi John!

Yes, I have 4 primary wires. I wonder if I made a mistake    :oops: : I left "+" and "--" (I think) wrapped in plastic tape; not connected to each other.

Maybe with other amps I will need to ground the output, who knows   :wink:    

Thanks
MAuricio

John Chapman

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At last: DIM TVC!
« Reply #3 on: 24 Nov 2004, 01:00 am »
Hello!

Run don't walk and connect those wires! Should have them connected as follows:

++ to the input 'hot'
-- and + connected together and taped off.
- to the input ground side.


Won't hurt anything the way you have it not but should get much better connected for sure!


Thansk!

John

maxlorenz

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EUREKA!!
« Reply #4 on: 24 Nov 2004, 02:14 pm »
Dear John:
Even before I read your last post I surelly was worried by your question about the primaries. I think the problem was that I build MKIII version based on MKII diagram      :oops:   :oops:    :oops:
I found a previous thread about primaries and, yes, I ran and connected the "+" and "--" and ... SLAMMM! I got the whole picture wright! Beautyful extended, warm, very controled bass! In fact I never had this kind of bass performance in my living room (even with my NAD receiver in 5.1).

I put a Bossa Nova CD, Caetano Veloso, mainly "live" performances, and all I could think was "this is impossible, this CD cannot sound this good". :!:

I was using half the power of the TX (maybe as autoformer?). I thought that both primaries were completely separated windings  :o

I will post my findings as burning-in progress.
(I also grounded outputs; just in case)

 :beer:
Best regards
Mauricio, happy TVC owner.

John Chapman

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At last: DIM TVC!
« Reply #5 on: 24 Nov 2004, 02:57 pm »
Hello!

That's better! Actually the way it was wired it did not have the primaries connected in series or parallel - they were separate with one end of each connected. I am kinda surprised it worked as good as it did!

Keep me posted.

Many Thansk!

John

maxlorenz

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At last: DIM TVC!
« Reply #6 on: 4 Jan 2005, 08:20 pm »
Dear John:
I find impossible to imagine a better preamp that my TVC. Both, soundwise and from a theoretical point of view, it is superb. It's amazing how fast and dynamic it is. I have no complaint about bass: wonderfuly controled and powerful. Sometimes I look for the power cord and it has none! Sometimes I forget that I have a pre.

I finished my second DIY project   8)  : a power amp based on Hypex's UcD 180 class D modules. You should check these out: greatest HiEnd bargain!  (I'm not complaining about TX 102's price  :mrgreen: ).  Well, as I was saying I'm totally pleased with my DIY combination. This pair can be sweet and detailed or exhibit untiring, effortless, punchy  sound when needed.

I have hum/buzz problems with some gear combinations. I will try a solution that I learnt at DIYaudio.com: "softgrounding" inputs through a  500 Ohm to 1 K resistance and leave the outputs "floating". What do you think?

Thanks again for everything.
Mauricio

John Chapman

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At last: DIM TVC!
« Reply #7 on: 4 Jan 2005, 09:44 pm »
Hello!

Glad the tx102 has worked out well. You could do a soft ground to experiment - I used to have a selection for that but it caused so much confusion I dropped it! Always seemed systems liked a hard or float ground anyway.  Hard ground is exactly the grounding you'd have with a traditional pre-amp and float breaks the grounds to break a potential ground loop.

Refresh my memory if you can - are you switching both hot and ground on each input? Have you a toggle for ground selection? Does the hum happen with just certain sources and if so have you tried both ground options with each source to see if hard or float gets rid of any hum?

We'll start here and should be able to get it quiet pretty quick.

BTW - I like what I have seen of the Hypex modules - I think that is what Kevin from diycable.com is using in his new amps.  


Many Thanks!

John

maxlorenz

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At last: DIM TVC!
« Reply #8 on: 7 Jan 2005, 11:34 pm »
Hi. Sorry for the delay. Too much work  :wink:

My TVC is one in/one out without toggle switch or anything that could be detrimental to sound. When I want to experiment I re-solder grounds  :oops: or use small clamps.

Remember that I can let grounds "all floating"? I wonder why I still hear hum/buzz with certain source/amp combination when floating.

I use two sources and two amp with different results:
NAD C542->TVC->Hypex UCD amp= no hum (although I perceive small chassis voltage by hand  :oops: )
NAD C542->TVC->Monarchy SE100= hummmm

NAD as transport->DIP upsampler->M-Audio superDAC->TVC->Hypex UCD amp= hummmm . (I discover that when DIP is on it induces hum even if not used. One ground loop is using DIP's PCord)

same chain->Monarchy amp= no hum.

I will experiment and tell you.

About Hypex UCD amp: the modules sound great. I'm amazed (and quite proud: first projects) that with less than US$1000 one can DIY this TVC-class D amp combination and get (at least I think so) HiEnd sound. I'm considering selling my class A amps and make two UCD400 (400W/4 Ohm) monoblocks (and save money to better sources or TX102s ).
Adire Audio imports them but it's cheaper to buy direct from Hypex.nl. Euros are getting more expensive, I'm affraid   :(

Other thing: the amp's input receiver is differential and I remember that the inventor said somewhere that + and - signal don't need to be symetrical nor opposite to work. I plan to try using the unused -42 lead of the TX and see if I can fed it to the - (pin 3) input. Perhaps I can benefit of a better CMMR or whatever the term.

I hope 2005 will be full of joy and success for you, your family and your staff.  :D

Mauricio

John Chapman

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At last: DIM TVC!
« Reply #9 on: 8 Jan 2005, 12:12 am »
Hello!

I'll comment best I can in-line below....

Thanjks!

John





>My TVC is one in/one out without toggle switch or anything that could be
>detrimental to sound. When I want to experiment I re-solder grounds  or
>use small clamps.

Clip leads are handy for experimenting with grounding.

>Remember that I can let grounds "all floating"? I wonder why I still hear
>hum/buzz with certain source/amp combination when floating.

Much more common to need a hard ground - not floating. Floating grounds depends on the source and amp both having a good ground through a 3 prong cord.  If there is a loop float can help out but if I had to pick one way to ground it'd be hard ground since lots of systems 'want' the sources grounded via interconnects.

>I use two sources and two amp with different results:
>NAD C542->TVC->Hypex UCD amp= no hum (although I perceive small
>chassis voltage by hand )

Yikes......

>NAD C542->TVC->Monarchy SE100= hummmm

Do the NAD and the Monarchy both have 3 prong plugs?  If not clip a lead in and do a hard ground.

>NAD as transport->DIP upsampler->M-Audio superDAC->TVC->Hypex
>UCD amp= hummmm .

Again if floating then the dac and amp both need a good ground themselves.  

>(I discover that when DIP is on it induces hum even if not used. One >ground loop is using DIP's PCord)

Not good.... I used to have a DIP around and don't recall that with it.

>I will experiment and tell you.

Please do - try each source hard/ float and see if a pattern develops. Soft grounding (via a resitor) should not be needed once the grounds in the system are correct.


>Other thing: the amp's input receiver is differential and I remember that
>the inventor said somewhere that + and - signal don't need to be
>symetrical nor opposite to work. I plan to try using the unused -42 lead
>of the TX and see if I can fed it to the - (pin 3) input. Perhaps I can
>benefit of a better CMMR or whatever the term.

Not sure I follow exactly. If you want to feed the amp a bal signal then pin 3 will be the bottom of the secondary (unmarked wire) and then pin 2 from the switch (as it is now I expect) then ground pin1 to central chassis hum.

Speaking of chassis grounds - do you have the output jacks grounded to a central point on the chassis now - along with the screen wires from the tvc, etc.? If not then please do this as the pre-amp definitely needs a good ground scheme to get stable.

>I hope 2005 will be full of joy and success for you, your family and your
>staff.

You too!

Thanks!

John

maxlorenz

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Dear John:
« Reply #10 on: 28 Mar 2005, 11:59 pm »
At last I found the time to change outputs to XLR/bal: shallco's output (+) to pin 2; screen to pin 1 then to ground; unmarked OCC coppper wire ("base"; (-)) to pin 3. Now I realize that it naturally makes a balanced output (at least I think so). Appart a little anoying buzz that I plan to exorcize soon I GOT A BIG IMPROUVEMENT IN SOUND. It's amazing because my Monarchy amp accepts balanced signal but are not  true balanced amps.

Most notable is change in volume output: I used to let the volume at -20dB; now at -40dB my ears clip!
Music is rounder, fuller, sweeter, with more detail, ambience, authority, naturalness , etc... Bass and midbass are excellent! And I expect to get better when solder and wires burn-in (I think every volume step need to burn-in).

How can you explain such an improuvement in volume output?

Certainly a source with high voltage output   is mandatory to achieve optimal results with the TXs.

Thanks again and again.

Mauricio

John Chapman

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At last: DIM TVC!
« Reply #11 on: 29 Mar 2005, 01:43 am »
Hello!

Glad it has been fun to add bal out and that is is working well.

Higher volume output is likely because the amp's input is more sensitive on the bal input than the single ended. The overall voltage out of the pre-amp is the same as it would have been before.

Keep us posted on further testing and results!

maxlorenz

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At last: DIM TVC!
« Reply #12 on: 29 Mar 2005, 02:10 am »
mmmh.. :scratch:  I don't know if it's more sensitive: I did heard more sens while fed through DAC's XLR outputs, but these have "pro level" output (+4dBv typical; +20dBv max, if I recall well) so it better sound louder.

First attempt to get rid of HF buzz failed, with "clips" or "clamps" on different ground paterns. Tomorrow I will try "soft grounding" the inputs.

Could the unused (-) path ("false" balanced amp) be catching RF or something? I will try my true balanced (at least balanced  receiver) amp.

Some people recommend RC network to get rid of RF, but I don't know how to implement it. Anyone could post a simple diagram, please?

Thanks