DIY Sowter/Shallco TVC vs commercial offerings

cporada · « **on:** 24 Mar 2009, 11:29 pm »

I'm wondering if anyone can offer their opinion on whether I'd be better off buying something like the Promitheus TVC or building a DIY version using Sowter 9335 tranformers and a 26-step twin gang Shallco switch. The cost isn't too much more to build my own with high end transformers and switch than to buy the basic Promitheus TVC (in which people have complained about the switches), so I'm curious which people think would sound better. If I build it, I'd be doing away with the selector switch and just using it for a single source, since I figure that's the "purist" way to do things

Next, if the DIY way is a better way to go for overall bang for the buck, I have a further question. Brain Sowter recommended Shallco #214-FB-26. Shallco told me the following: “Part number 214-FB-26 is a 26 position, non-shorting switch. Since this switch is non-shorting, the breaking contacts will need to be soldered to the active contacts to prevent “popping” as the positions are changed. The sound quality for shorting and non-shorting versions will be the same (same contact and wiper type).”
So the questions I have are:
1) Is there any advantage to using the non-shorting switch like Brain advises, or could I use the shorting version, since the soldering would be much easier (soldering is not my forte)?
2) This switch will allow me to solder the leads from both transformers into it to control the volume of both channels, i.e., it's a stereo switch, right?
3) How tough is it to solder all those leads to the contacts on the Shallco?
4) Lastly, how much better (hopefully) should a TVC like this sound compared to an active line stage with respect to noise floor, presence, tonality, and imaging? Will I notice a loss in dynamics or "life" of the music?
Thanks very much in advance for any thoughts.
Chris

*Scotty* · « **Reply #1 on:** 25 Mar 2009, 12:09 am »

You might want to read this review of the Sonic Euphoria TVC in Stereophile. http://stereophile.com/solidpreamps/106sonic/index4.html There is an excellent photo of the interior which illustrates the complexity of the internal wiring.
Also pay particular attentention to figure one in the Measurements section. This graphic shows the ultrasonic peaking that takes place in the output. The effect of this peaking is to adversely affect the stability of many amplifiers causing them to oscillate and self destruct. There is also no way of knowing before hand if your amplifier will be one of the ones that is incompatible or not. I can specifically recommend against pairing a TVC with a Gainclone amp. These amps already have a small stability margin and a TVC puts them right over the edge.
It would be nice if you could borrow a TVC to try in your system before you put a lot of labor into building one. If you are not comfortable soldering this is a rather solder intensive project to tackle.
Scotty

Paul Hynes · « **Reply #2 on:** 25 Mar 2009, 11:40 am »

Hi Chris,

The "Lightspeed" LDR volume control is the best volume control I have ever used. It is very transparent and musical. George Stantscheff sells them from Australia. Mail him at georgehifi@optus.com.au and he will be pleased to send you some information.

Regards
Paul

JoshK · « **Reply #3 on:** 25 Mar 2009, 01:35 pm »

I like my TVC (DIY). Its true that they can cause ultrasonic ringing, but that depends on a lot of variables. Still, if your amp doesn't have gobs of feedback then it probably won't matter. It all depends.

I used Seiden switches and Silk TVCs from diyhifisupply. I like it a lot. Lots of soldering though. Tedious to say the least. You also have to make a chassis.

You might just get a TVC kit from diyhifisupply. They sell the whole shibang, TVC, switch, connectors, case all in a package.

kit on DHS

JoshK · « **Reply #4 on:** 25 Mar 2009, 01:40 pm »

Another

guest48077 · « **Reply #5 on:** 25 Mar 2009, 01:51 pm »

Quote from: cporada on 24 Mar 2009, 11:29 pm

The cost isn't too much more to build my own with high end transformers and switch than to buy the basic Promitheus TVC (in which people have complained about the switches), so I'm curious which people think would sound better. If I build it, I'd be doing away with the selector switch and just using it for a single source, since I figure that's the "purist" way to do things

I went for a different approach, instead of having the selector switch and extra inputs on my TVC (which is more money). I built my own 8 input 1 output switch. My DIY switch cost about 75 bucks - The case was $35, DIY oak face plate, switches and coper wire etc.

Since I now didn't need a TVC with a lot of inputs I got a better TVC with only 1 XLR input and 2 XLR outputs in doul mono boxes . The switch was also easy to build and very enjoyable. It was my first electronic project. Pics are in My gallery below. I can also scan and upload the simple wiring diagram if you would like.

cporada · « **Reply #6 on:** 25 Mar 2009, 03:05 pm »

Hi everyone
Thanks for all the helpful replies. I was thinking of something even simpler, more like this:
http://mapage.noos.fr/dom.mafrand/preamp.htm
Would this be any better sonically since it has no selector, etc., just the transformers and a switch. The soldering sure looks easier than the Sonic Euphoria!
Does the LDR work with all power amps? What does that cost (roughly) if bought assembled?
Thanks again
Chris

Paul Hynes · « **Reply #7 on:** 25 Mar 2009, 03:13 pm »

Hi Chris,

You Would need to e-mail George to get some price info for the LDR volume control.

Regards
Paul

poseidonsvoice · « **Reply #8 on:** 26 Mar 2009, 12:14 am »

Paul,

I e-mailed George, and he doesn't offer the Lightspeed attenuator for diy purposes. Fully built only. Moreover he cannot build a balanced version in a repeatable fashion as matching of the LDR's would be too difficult. Even at the price he is offering for a fully built version (single ended version) its only $398 which is reasonable as far as I am concerned. I'm just bummed that he won't sell just the unit without a case/connectors for the same price. Even the 5VDC regulated power supply can be done using your regulator boards.

My only option would be to purchase the fully built unit and then gut it. I would have no use for the enclosure, wall wart, and connectors. But he doesn't offer a balanced version so I can't go this route unfortunately.

Anand.

Paul Hynes · « **Reply #9 on:** 26 Mar 2009, 09:46 am »

Hi Anand,

How are you keeping?

Check out the thread "Lightspeed Attenuator" in the Lab Circle. It has links to a DIY Audio forum thread that covers a diy version. It is adaptable for balanced operation. It is a long thread but well worth persevering with as it is an excellent volume control sonically.

Regards
Paul

TomS · « **Reply #10 on:** 26 Mar 2009, 01:09 pm »

Quote from: poseidonsvoice on 26 Mar 2009, 12:14 am

Paul,

I e-mailed George, and he doesn't offer the Lightspeed attenuator for diy purposes. Fully built only. Moreover he cannot build a balanced version in a repeatable fashion as matching of the LDR's would be too difficult. Even at the price he is offering for a fully built version (single ended version) its only $398 which is reasonable as far as I am concerned. I'm just bummed that he won't sell just the unit without a case/connectors for the same price. Even the 5VDC regulated power supply can be done using your regulator boards.

My only option would be to purchase the fully built unit and then gut it. I would have no use for the enclosure, wall wart, and connectors. But he doesn't offer a balanced version so I can't go this route unfortunately.

Anand.

Anand,

The ZenMod PoorSerbianMan Lightspeed (PSMLS) version on diyaudio includes 8 LDR's (matching needed) and 4 balanced JFET 74/170 buffers. He is offering boards with power supplies but he has had some health issues limiting his usual frantic pace of producing kit sets. I would like to try this with my Pumpkin/Shunty preamp at some point myself though having remote capability as Paul offered with the VCCS would be really nice to add as well.

Tom

poseidonsvoice · « **Reply #11 on:** 26 Mar 2009, 01:12 pm »

Quote from: TomS on 26 Mar 2009, 01:09 pm

Quote from: poseidonsvoice on 26 Mar 2009, 12:14 am
Paul,

I e-mailed George, and he doesn't offer the Lightspeed attenuator for diy purposes. Fully built only. Moreover he cannot build a balanced version in a repeatable fashion as matching of the LDR's would be too difficult. Even at the price he is offering for a fully built version (single ended version) its only $398 which is reasonable as far as I am concerned. I'm just bummed that he won't sell just the unit without a case/connectors for the same price. Even the 5VDC regulated power supply can be done using your regulator boards.

My only option would be to purchase the fully built unit and then gut it. I would have no use for the enclosure, wall wart, and connectors. But he doesn't offer a balanced version so I can't go this route unfortunately.

Anand.
Anand,

The ZenMod PoorSerbianMan Lightspeed (PSMLS) version on diyaudio includes 8 LDR's (matching needed) and 4 balanced JFET 74/170 buffers. He is offering boards with power supplies but he has had some health issues limiting his usual frantic pace of producing kit sets. I would like to try this with my Pumpkin/Shunty preamp at some point myself though having remote capability as Paul offered with the VCCS would be really nice to add as well.

Tom

First of all, thanks for all the help fellas. And I don't mean to hijack this thread, just looking for opportunities to use a great volume control/attenuator in a balanced format. Paul, are you still offering your kit with remote capability? Or did I miss that bid

Tom, I will look into the PSMLS version.

Best,
Anand.

Paul Hynes · « **Reply #12 on:** 26 Mar 2009, 01:31 pm »

Hi Anand,

Have you read that thread already?

The group buy is only just happenning. You can buy boards or built and tested modules (without the LDRs as Uriah Daily on the Lightspeed forum thread is supplying matched sets of these). Application notes are included with these.

I have received the VCCS control boards and will be building one to verify layout etc at the weekend. I am told by the board manufacturer that the IR transmitter and receiver boards should be here by the end of next week, so I will build and verify an IR set the following weekend. The VCCS and IR circuits have already been verified on the bench and in my system.

There is a queue building up so if you want to go with this project reasonably quickly you had better stake your claim.

Regards
Paul

JoshK · « **Reply #13 on:** 26 Mar 2009, 01:40 pm »

I have Greg Ball's LDR volume control that I was planning to try out soon. I plan to use a Cinemag input transformer into the LDR in balanced shunt attenuator configuration. This way you can use a SE LDR but in a balanced or SE stage.

The pot really controls the voltage into the LDR, so I was planning to sub a remote controlled pot I have. That kit is done and works. You can get them from Altronics in Oz.

One of these days I'll have some time to compare the LDR, a standard pot, my TVC, and a ladder stepped attenuator. I have them all, all wired up in different projects except the LDR.

JoshK · « **Reply #14 on:** 26 Mar 2009, 01:49 pm »

There is always Tribute's inductive volume control. I'd really like to try it out.

Too many options, too little time.

http://www.tribute-audio.nl/

cporada · « **Reply #15 on:** 26 Mar 2009, 03:30 pm »

Wow, this is getting quite interesting. So if I understand correctly, I'd be better off with George's lightspeed than with anything I could build with the Sowter's, especially seeing as how just the two Sowters would set me back almost the entire cost of the Lightspeed assembled, tested and shipped! Is this correct, or would a TVC-type volume control still be better? Can anyone compare and contrast the two approaches? What exactly does the Lightspeed do? I got all the info from George, but it's beyond me what it's actually doing.
Thanks!
Chris

cporada · « **Reply #16 on:** 26 Mar 2009, 03:42 pm »

A couple other quick questions:
What does the Tribute cost? Their website has no pricing. How does that differ from a TVC or LDR?
Does the Lightspeed restrict dynamics at all like a resistor-based attenuator?
What does "LDR" stand for?
Will something like the LDR preserve the "drive" I'm used to with an active line stage? I know when I tried Endler's attenuators, my sound became kind of lifeless, although very detailed and unbelievably clear.
Thanks for all the helpful info!
Chris

Paul Hynes · « **Reply #17 on:** 26 Mar 2009, 03:46 pm »

Hi Chris,

The “Lightspeed” is an L pad attenuator consisting of one LDR (light dependant resistor) in series with the signal and one LDR between signal and ground. Light is used to vary the resistance of each LDR to provide the variation in signal level required for volume control. There are no switch contacts, wipers or long lengths of wire to degrade the signal. The “lightspeed” is very transparent to the music and adds little colouration of it’s own.

Regards
Paul

Paul Hynes · « **Reply #18 on:** 26 Mar 2009, 03:53 pm »

Hi again Chris,

The Lightspeed does not restrict dynamics. In fact it has the most natural dynamic rendition I have heard and in my system it is anything but lifeless.

You may need to consider impedance matching depending on the source/ destination impedances of the other equipment you are using. If you have this impedance information I could give you better advice.

Regards
Paul

JoshK · « **Reply #19 on:** 26 Mar 2009, 04:51 pm »

Quote from: cporada on 26 Mar 2009, 03:42 pm

A couple other quick questions:
What does the Tribute cost? Their website has no pricing.

You have to contact them to find out. I imagine it is in the Sowter ballpark.

Quote from: cporada on 26 Mar 2009, 03:42 pm

How does that differ from a TVC or LDR?

Its an AVC, i.e. Autoformer volume control, which is a bit different from a transformer volume control, but same principal.

DIY Sowter/Shallco TVC vs commercial offerings

guest48077