[andyr]

For all of you out there who haven't yet implemented the DSK "Bob Crump Volume Control Upgrade" (aka a TKD stepped attenuator, with mods), you may be interested in a new style of volume control which a mate of mine has just emailed me about.    It sounds very interesting. 

It uses a specially designed transformer - with many secondaries - to effect 2dB volume changes at each detente.  For your edification, I have pasted in his description of the difference it made (BTW, he listens to digital media most of the time):

--------------------------
TVC = Transformer Volume Control
I have just upgraded my preamp from a shunt style 24 step attenuator with Holco resistors to a pair of Sowter transformers; this is called a TVC transformer volume control - the primary of the transformer is (basically) the input from the selector switch and there are 24 secondaries which are the outputs, each gives 2dB attenuation.

Well the sound is to die for ... it is like a major component upgrade.  Best part is that a lot of the grit, hardness, harshness and edge you hear on digital is coming from your (standard) volume control, because with the TVC IT IS GONE!  In its place is smoothness, openness and a naturalness that is uncanny - you'd swear you were at the performance.

See www.sowter.co.uk; click on attenuators; also google 'transformer volume control tvc'.
--------------------------
 
Regards,

Andy

[AKSA]

Andy,

These first started appearing about twenty years ago.  One Swiss manufacture sells one for the dignified price of $US3K.

It is a transformer, however, with all the strengths and weaknesses.  Even the cheapest of them are twice the price of the resistive attenuators, and if you build them yourself, watch out for the inevitable confusion of the wiring!!

My own preference these days is for the very good PGM2310 attenuator chips offered by AD, and they cost a few dollars.

Cheers,

Hugh

[JLM]

TVC, primary advantage: impedance buffering (if needed), colorations (for solid state guys that have a fear/distaste for tubes)

TVC, primary disadvantages: colorations, air borne interferences, lots of little wires/solder joints to fail

Bent Audio, Promitheus Audio, and DIY Paradise are popular sources.  Check out Bent and Promitheus here at AC.

[kyrill]

besides price and complex soldering are there soundwise Hugh, disadvantages for such a transformer attenuator? does  a transfo need some minimum volts?

JLM you mention colorations?

[bluesky]

Hi Hugh

Firstly best wishes to you and all in the Aksa community for the year ahead!

Now to the attenuator volume control you just mentioned, my ears pricked up when the words "just a few dollars" appeared before me! 

Where can I find some more information on these critters? I am trying to think what the AD acronym stands for, without any luck.  Sigh........perhaps it is too late in the evening for me, way past my normal bedtime. 

I've been assembling a GK-1 and a pair of Aksa 55's for a good friend of mine.  It is all good experience for me and helps him out as he and his partner have just had their first child.  A very exciting time for them but between his job and the new baby it is certainly understandable not having any spare time for audio stuff.

Cheers

Ian     

[kyrill]

AD is a brand name ( Analogue Devices)

[JLM]

kyrill,

Yep, I mentioned it twice, just to provide a balanced perspective.  (IMO audiophiles, by definition, aught not to want them, but to each own.)

[Steve Eddy]

My own preference these days is for the very good PGM2310 attenuator chips offered by AD, and they cost a few dollars.

Happy New Year, Hugh!

I assume you mean the PGA2310?

Those are nice for remote control volume control, but unless one buys a pre-designed kit, implementing the 2310 would be something of a daunting task for the average DIYer. You need a microcontroller along with the software and hardware for programming it not to mention knowing how to write the code to program it. You also need to know how to interface the microcontroller with a display driver and an optical encoder (and/or an IR receiver if you want remote control).

Bottom line, whether you buy a kit or try and do it yourself, you're going to end up spending more than just a few dollars (and investing quite a lot of time if you DIY) before you end up with a volume control. Just the 2310 itself sells for $16.58 at Mouser.

Personally I've felt that the real advantage of the TVC is just the "T." It's been my experience with transformers that they do their best when their secondries are loaded with their ideal impedance. With a TVC, you have what amounts to many different transformers, yet all of them end up being loaded by the same impedance.

Also, building a transformer with that many taps requires inevitable compromises in terms of winding precision, winding efficiency and parasitics compared to a transformer with no taps.

What I've done for many years has been to use a high quality 1:1 input transformer with a resistive attenuator on its secondary of the transformer's ideal impedance and preferably built into the preamp or amp depending on implementation.

And even if one wants to go with something like the 2310, its 10k ohm input impedance makes it an ideal match for a top quality 1:1 input transformer such as the CineMag CMLI-15/15B directly driving its input. You get ground isolation, outstanding CMRR, the ability to feed it from balanced or unbalanced sources, etc.

So there you have it. My first transformer rant of 2008.

se

[Steve Eddy]

For all of you out there who haven't yet implemented the DSK "Bob Crump Volume Control Upgrade" (aka a TKD stepped attenuator, with mods), you may be interested in a new style of volume control which a mate of mine has just emailed me about.    It sounds very interesting. 

Happy New Year, Andy!

Er, NEW style of volume control? TVCs have been around for at least five years or so.

You are the Andy R****** I've known for some years now, yes? If not, my apologies. If so, dude, how could you have been on the forums all these years and manage to miss the whole TVC thing until now?

se

[poseidonsvoice]

What I've done for many years has been to use a high quality 1:1 input transformer with a resistive attenuator on its secondary of the transformer's ideal impedance and preferably built into the preamp or amp depending on implementation.

Besides Steve Eddy's designs, there are a few others that also implemented what he mentions above, including the Ingot by Peerless (http://peerless-transformers.com/). There was a thread awhile back on this at the Magnequest forum. I do exactly this in my preamp (below), where I use a Lundahl 1676 input transformer coupled to a 10K DACT volume control.

Just different ways to get to nirvana...

Anand.

[kyrill]

hi JLM

what kind of colorations have  you heard or experienced?

freq colorations? Ringing or something else?

Almost all tubes have output trannies do they exhibit those same kind of colorations?

[Steve Eddy]

Besides Steve Eddy's designs, there are a few others that also implemented what he mentions above, including the Ingot by Peerless

The Ingot is also my design, built around Mike's trannies.

Just different ways to get to nirvana...

Yup! That's the beauty part. No one's forced to go down anyone else's path and we can all ultimately end up at the same destination.

se

[andyr]

Happy New Year, Andy!

Er, NEW style of volume control? TVCs have been around for at least five years or so.

You are the Andy R****** I've known for some years now, yes? If not, my apologies. If so, dude, how could you have been on the forums all these years and manage to miss the whole TVC thing until now?

se

Hi Steve,

Yes that's moye!   

How come I've never heard of a TVC ... well, I'm just a down-under country hick. 

All the best for 2008, Steve.

Regards,

Andy

[bhobba]

Hi Guys

Interesting thread.

One advantage I see with transformers is getting rid of all the 'crud' associated with DAC's.  You have these arguments about discreet vs valve vs op amp outputs (although with that new LM4562 you really have a op amp to love - my what specs - it apparently lifts a number of veils to many that have heard it - so much so some call it 'cold'). A transformer can do galvanic isolation, I/V conversion if required (those new voltage output dacs are supposed to be pretty good so that may not be an issue any more), its inductance interacting with the capacitance of you interconnects form a low pass filter - tons of advantages.

At a practical level I am looking at digital sources.  The new Cambridge Audio 740C with its anagram technology really appeals.  It uses twin Wofson DACS summed by a restive network into a series of op amps doing filtering and buffering.  Would it be possible to rip all those op amps out after the summing restors. take it to a transformer with a DACT connected across it then to a Soraya?  Reference Audio Mods do a similar mod on the 840C but charge $1000.00 for it.  Any takes on being able to do a mod like that on a 740C?

Thanks
Bill

[bhobba]

How come I've never heard of a TVC ... well, I'm just a down-under country hick. 

Yea - us Aussies have a 'unique' perspective - that's for sure. 

Andy, in one of your other posts you mentioned you do modding.  Would it be possible to do a mod like I suggested on the 740C?.  I would also like the clock (I rather like the Burson clock from right here in Aus) and power supply upgraded with better diodes decoupling capactors etc?  Saves me sending to one of those modding outfits overseas and attracting the attention of customs.  The main mod would be the output and clock mod - the power supply upgrade is well under the magical $1000.00 mark that attract customs fees etc.

Thanks
Bill

[bhobba]

Would it be possible to rip all those op amps out after the summing restors. take it to a transformer with a DACT connected across it then to a Soraya?  

I knew I had read of Simone else who did it.
http://www.audiodesignguide.com/DAC_final/DacFinal.html

Those Wolfsom DACS sure look good.

Thanks
Bill

[bhobba]

I knew I had read of Simone else who did it.

Whoops.  Didn't check the post. That should of course be someone. 

Thanks
Bill

[Steve Eddy]

Yes that's moye!   

Ah! Didn't think there were any other any other Andy Redwoods from Melbourne frequenting the audio forums.

How come I've never heard of a TVC ... well, I'm just a down-under country hick. 

Yeah, but down-under country hicks access the same Internet as us up-over city slickers.

I just couldn't believe you could have been on the Asylum and diyAudio as long as you have without stumbling across one of the many threads that talked about TVCs. But I guess I'm gonna have to now.

All the best for 2008, Steve.

Thanks, Andy! Same to you and yours!

se

[andyr]

I just couldn't believe you could have been on the Asylum and diyAudio as long as you have without stumbling across one of the many threads that talked about TVCs. But I guess I'm gonna have to now.

se

Steve,

I don't frequent DIY Audio ... it's waaay over my head! 

Regards,

Andy

[JohnR]

Besides Steve Eddy's designs, there are a few others that also implemented what he mentions above, including the Ingot by Peerless

The Ingot is also my design, built around Mike's trannies.

Your signature gives no indication of this. Would you please update it for the sake of proper disclosure.