TVC's - Transformer Volume Controls and drive.

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DaveX

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TVC's - Transformer Volume Controls and drive.
« on: 16 Jun 2006, 11:58 pm »
Can a TVC passive pre drive a pair of low capacitance 12 foot cables without rolloff problems, my power amps have 26db's of gain. Thanks.

John Chapman

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TVC's - Transformer Volume Controls and drive.
« Reply #1 on: 17 Jun 2006, 01:00 pm »
Hello!

With typical sources and speakers this should be just fine. If you let me know what your other components are and also what you use for a pre now and where you typically run the level knob for loudish listenning I can say for sure that it'd be fine.


Many Thansk!

John

DaveX

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TVC's - Transformer Volume Controls and drive.
« Reply #2 on: 17 Jun 2006, 02:55 pm »
Hi, I'm using a Cary 94L preamp, Spendor S5e's, Whest phono stage. The volume knob is at about 28 clicks 2 o'clock. Thanks.

John Chapman

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TVC's - Transformer Volume Controls and drive.
« Reply #3 on: 17 Jun 2006, 03:35 pm »
Hello!

Sounds like a fun system. I started digging up the specs for the stuff. To be really complete with the checking I should find out what your cartridge and amp is as well.


Thansk!

John

DaveX

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TVC's - Transformer Volume Controls and drive.
« Reply #4 on: 17 Jun 2006, 09:45 pm »
Sorry, power amps are CI D200's (26db's gain), cartridge is an Ortofon MC5000 (.14mV output)

samplesj

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TVC's - Transformer Volume Controls and drive.
« Reply #5 on: 18 Jun 2006, 01:02 am »
I can't help out with your direct question, but I can say that if it is at all possible do it.  UCD and TVC are a wonderful match.  Music just appears out of pitch blackness.

I've not heard Dusty's D200's (modified UCD modules with his custom power supply), but my UCD modules mesh very well with John's version of the S&B transformers.  I know there are several people on the DIYAudio forums that use that combo too.

John Chapman

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TVC's - Transformer Volume Controls and drive.
« Reply #6 on: 19 Jun 2006, 09:04 pm »
Hello!

Sorry for the delayed reply. I got consumed this past few days. Finally recieved a bunch-o-parts from S&B and am busy unpacking, testing, and building.......

I ran though the numbers for all your gear and I see two answers - well more like one answer to your question and then another question for you to look at.

The Phono Stage has a really low output impedance and so coupled via a TVC level control it should do a fine job of driving 12' cables - particularly if the level is turned down a couple steps from the loudest setting or lower. This however got me looking at another factor - the overall gain in your system.

With the Whest having 62db of gain (on the lowish side for an MC stage) AND with the cart's 0.14mV output level being lower than most carts AND the speakers not being particularly sensitive at 87 db I am wondering if your system will play loud enough with a passive control of any kind. Most of the time these factors work out just fine but in this case I can see the stars are kinda all aligned to bias levels down lower.  


The pre-amp you have now has a decent amount of gain at 16db.  You can easily test if a passive is an option by connecting the Whest directly to the amps and putting on a record that starts off really quietly - If you feel it is too loud then you'll be fine for gain and the cable drive issue would not be a problem at all. If you play the entire track and it is only normal listening levels or lower then for the system today you need the gain of the Cary so a passive (even a TVC that can offer +6db gain) will likely not do the trick.


Please keep me posted on your tests and thoughts - it is interesting to go through these system numbers.

Many Thansk!

John

DaveX

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TVC's - Transformer Volume Controls and drive.
« Reply #7 on: 19 Jun 2006, 09:18 pm »
Thanks John, The Whest was ordered with 67db's of gain. To be sure I'm going to see if I can borrow a passive pre, that way I'll know for sure. John what is the input impedance of the TAP. Thanks for all your help.

John Chapman

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TVC's - Transformer Volume Controls and drive.
« Reply #8 on: 19 Jun 2006, 10:14 pm »
Hello!

Great if you can borrow a passive to test. 67db is quite a bit more than 62 really so that will help for sure. The input impedance of any TVC depends on the connected loads. Withh the 100K input imp of the CI amps you have it'll be plenty fine and really easy to drive. - much easier to drive than a typical 10K passive control.

Thansk!

John

oliverlim

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Re: TVC's - Transformer Volume Controls and drive.
« Reply #9 on: 11 Aug 2006, 02:24 pm »
What about in my system?  I have been considering using a PassivePre but a few potential problems I see.

Pioneer DV79 Universal Player (Heavily modded)
Rotel RSP1068 PreProcessor which doubles as the preamp currently
Odyssey HT3 AMP driving a pair of Thiels 2.4 (87db)

I currently listen to my music at about 50-55 on the rotel dial of which 99 is the max.  Another potential problem is that the cables to from the pre to the amp is about 25 feet.  I intend to get BlueJeans new LC-1 cable which I understand has a very very low capacitance.

Thanks
Oliver

John Chapman

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Re: TVC's - Transformer Volume Controls and drive.
« Reply #10 on: 11 Aug 2006, 04:02 pm »
Hello!

I'll dig up the specs for the gear but to really give it a careful look I should find out just what was done to the Pioneer Player - in particular what output stage is used - this will to a large part dictate the ability to drive long cables.

I just can't help myself though - Is there not a way to get the cables shorter than 25'? Regaurdless of what pre is used I know I'd try and minimize all cable lengths  - both to minimize the affects and also to minimize the costs! The fact it is a low capacitance cable will help a lot but it must be rather expensive for a cable that long. 

Thanks!

John

oliverlim

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Re: TVC's - Transformer Volume Controls and drive.
« Reply #11 on: 12 Aug 2006, 08:56 am »
I thought long and hard about the length but I decided i did not want anything upfront to spoil the soundstage.  I also did not really have any intention of trying any passive till I heard about TVC preamps and I really love the look of your new TAP!  :p

I went down the HT route in the last few years and more or less have settled on what I wanted to achieve. My wife likes HT and its something we can share. Shes not really into music so it was not my top priority. Now just trying to improve on my stereo setup so that I can enjoy some music once in a while. So I really cant do much about the lenght.  I can use the 25 feet for the CD to the Pre and a short 1 feet for the pre to the amp if that is a better option though.  My intention was to use a simple cable like those from bluejeans or maybe Bettercables.  I heard alot of cables including expensive ones and cant say I really feel they are good value for money.  Between XLO, DH Labs, PS Audio and my own Canare L5C with their 75ohm soldierless RCA, I have to say I prefer the Canare.  So the long cable will not add too much for me.

The Opamps on the Pio was changed to a AD8066.  The main changes were the caps and and Linear power supply which were changed one each for the Digital and one for the Analog.  Hopefully this is enough info.

Oliver

John Chapman

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Re: TVC's - Transformer Volume Controls and drive.
« Reply #12 on: 13 Aug 2006, 03:48 pm »
Hello!

Glad to hear you did not break the bank on the 25' interconnects. I use various Canare stuff here and like too - particularly the digital coax and 75 ohm connectors they offer.  The modded player still has a solid state output stage so it's output impedance will not be too high. Normally not such a concern but with 25' of cables to drive I'd want to be looking to be sure the source has some ability to drive downstream gear. The fact you run at about 1/2 level on the rotel means that unless it has obscene amounts of gain (not likely) that the passive should to fine with your system from a level point of view.  There are a few ways to go - maybe give a phone call and we can discuss options, etc.... I'll be in my shop here pretty steady this comming week.

Thansk!

John