luvdunhill Posted August 28, 2008 Report Share Posted August 28, 2008 I'm sorta intrigued by this unit: anyone know much about it? Also, anyone heard the AVC TVC units from Diy HiFi (i.e. Django, etc.) 50/50% Permalloy Core Autoformer 28 step (Pair) | Diy HiFi Supply Of course there is the S&B, Sowter, and Jensen (and probably Lundahl) .. any others to consider? This would be used in conjunction with an active preamp. What is the general consensus of TVC used in this type of situation? Quote Link to comment Share on other sites More sharing options...
n_maher Posted August 28, 2008 Report Share Posted August 28, 2008 For me it would still come back to not being satisfied with or willing to risk 28 steps, especially at that cost ($270). Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 28, 2008 Author Report Share Posted August 28, 2008 for me, it depends on how the steps are spaced, not necessarily the number of steps... ~2dB may not be enough resolution, granted. check out the back of the pic posted. Quote Link to comment Share on other sites More sharing options...
n_maher Posted August 28, 2008 Report Share Posted August 28, 2008 for me, it depends on how the steps are spaced, not necessarily the number of steps... ~2dB may not be enough resolution, granted. check out the back of the pic posted.They would appear to be 3db steps for the pictured unit and also only have 24 steps (using the typical elma switch). And my experience with 3db steps leads me to believe I'd be rather unhappy with the level of choice provided regardless of how good it sounded. Quote Link to comment Share on other sites More sharing options...
spritzer Posted August 28, 2008 Report Share Posted August 28, 2008 RK50 FTW!!! Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 28, 2008 Author Report Share Posted August 28, 2008 They would appear to be 3db steps for the pictured unit and also only have 24 steps (using the typical elma switch). And my experience with 3db steps leads me to believe I'd be rather unhappy with the level of choice provided regardless of how good it sounded. My hottest source is 2v. I'd assume that the (mostly) 2dB steps on this baby with a 2v source is different "feeling" than having a 5v source... I'm surprised there aren't more TVC/AVC proponents around here Quote Link to comment Share on other sites More sharing options...
deepak Posted August 28, 2008 Report Share Posted August 28, 2008 My hottest source is 2v. I'd assume that the (mostly) 2dB steps on this baby with a 2v source is different "feeling" than having a 5v source... I'm surprised there aren't more TVC/AVC proponents around here I think a couple of people here tried or owned the Promitheus TVC. I wouldn't mind hearing a good one in a speaker system. Quote Link to comment Share on other sites More sharing options...
n_maher Posted August 28, 2008 Report Share Posted August 28, 2008 My hottest source is 2v. I'd assume that the (mostly) 2dB steps on this baby with a 2v source is different "feeling" than having a 5v source... It all depends on the application really, my problem with steppers has always been that they've been on headphone amps designed to drive vastly different loads. That's a bad application in my opinion. In a speaker amp I suppose it would be possible to tailor the gain (assuming it's adjustable in the design) such that you'd have plenty of adjustment. But again with some tube speaker amps (highish gain) I'd be hesitant to invest in one prior to testing the amp with a traditional pot to see where the listening sweet spot was. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 28, 2008 Author Report Share Posted August 28, 2008 I think a couple of people here tried or owned the Promitheus TVC. I wouldn't mind hearing a good one in a speaker system. Do you know what transformer he uses? Assuming it's the same guy at DiyA, he's a nice guy ..perhaps he'd tell me Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 28, 2008 Author Report Share Posted August 28, 2008 It all depends on the application really, my problem with steppers has always been that they've been on headphone amps designed to drive vastly different loads. That's a bad application in my opinion. In a speaker amp I suppose it would be possible to tailor the gain (assuming it's adjustable in the design) such that you'd have plenty of adjustment. But again with some tube speaker amps (highish gain) I'd be hesitant to invest in one prior to testing the amp with a traditional pot to see where the listening sweet spot was. I think 2dB inductive attenuation is much finer than resistive attenuation, but I have nothing to back that claim up other than voodoo magic. Quote Link to comment Share on other sites More sharing options...
deepak Posted August 28, 2008 Report Share Posted August 28, 2008 Do you know what transformer he uses? Assuming it's the same guy at DiyA, he's a nice guy ..perhaps he'd tell me I don't know. aerius might, I think he was one of the first people to mention them around here. It might be the Bent Audio one and not the Prometheus. Quote Link to comment Share on other sites More sharing options...
aerius Posted August 28, 2008 Report Share Posted August 28, 2008 I haven't heard the Prometheus or DIY Hifi transformers yet, and I don't know anyone around here who has one. I've heard the S&B TX102, a Dave Slagle AVC, and a couple Tribute AVC's. Tribute & Slagle will both do custom jobs, if you need different spacing between steps, inductance values or whatnot, they can do it. My personal favourite is the Tribute followed by the Slagle, the Tribute sounds like it has a wider bandwidth, more details, more speed, more goodness. Kinda like hearing DHT's for the first time but not quite that dramatic, but it's the same idea. The Slagle is no slouch itself, the difference between it and the S&B is the same as going from the Tribute to the Slagle. I don't know how much of a difference you'd notice on a typical headphone system, most of the listening was done on a custom open baffle speaker rig using Lowther and Beyma drivers with a Heil tweeter. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 28, 2008 Author Report Share Posted August 28, 2008 I haven't heard the Prometheus or DIY Hifi transformers yet, and I don't know anyone around here who has one. I've heard the S&B TX102, a Dave Slagle AVC, and a couple Tribute AVC's. Tribute & Slagle will both do custom jobs, if you need different spacing between steps, inductance values or whatnot, they can do it. My personal favourite is the Tribute followed by the Slagle, the Tribute sounds like it has a wider bandwidth, more details, more speed, more goodness. Kinda like hearing DHT's for the first time but not quite that dramatic, but it's the same idea. The Slagle is no slouch itself, the difference between it and the S&B is the same as going from the Tribute to the Slagle. I don't know how much of a difference you'd notice on a typical headphone system, most of the listening was done on a custom open baffle speaker rig using Lowther and Beyma drivers with a Heil tweeter. Thanks! were the AVCs wired for gain, or were they used passively, or in front of a preamplifier? I cannot seem to find pricing on the Tributes, so I've e-mailed them... Quote Link to comment Share on other sites More sharing options...
aerius Posted August 28, 2008 Report Share Posted August 28, 2008 They were used passively in front of the power amps. It was source(s) ---> AVC box ---> power amps ---> speakers. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 29, 2008 Author Report Share Posted August 29, 2008 They were used passively in front of the power amps. It was source(s) ---> AVC box ---> power amps ---> speakers. Any reason a TVC couldn't be used between a preamp and the amplifier itself? Kinda backwards thinking I suppose ... but it solves the SE -> Balanced problem that AVCs have to deal with... Quote Link to comment Share on other sites More sharing options...
Fing Posted August 29, 2008 Report Share Posted August 29, 2008 I have a Promitheus TVC (Reference C-Core) but haven't really done much listening on it since its in my speaker system. First blush impression is that its not a good match with my existing system - a bit subdued and boring. I need a better source and speakers but headphones suck all my cash. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 29, 2008 Author Report Share Posted August 29, 2008 I have a Promitheus TVC (Reference C-Core) but haven't really done much listening on it since its in my speaker system. First blush impression is that its not a good match with my existing system - a bit subdued and boring. I need a better source and speakers but headphones suck all my cash. Fing: Are you looking to sell your TVC? I might be interested Although, I contacted Nickolas and he's willing to sell me the balanced TVCs naked for DIY use Quote Link to comment Share on other sites More sharing options...
aerius Posted August 29, 2008 Report Share Posted August 29, 2008 Any reason a TVC couldn't be used between a preamp and the amplifier itself? Kinda backwards thinking I suppose ... but it solves the SE -> Balanced problem that AVCs have to deal with... Possible signal overload depending on the output of the preamp. The Tribute is spec'd for 6V RMS and I don't know what the specs are for other inductive volume controls, so it's possible the output from a preamp can overload them. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted August 29, 2008 Author Report Share Posted August 29, 2008 Possible signal overload depending on the output of the preamp. The Tribute is spec'd for 6V RMS and I don't know what the specs are for other inductive volume controls, so it's possible the output from a preamp can overload them. I thought about that, I think that's a limitation to the AVC approach but not the the TVC approach. However, I found a 50/50% Permalloy and Z11 core that would not have the same saturation issues as a 100% Permalloy unit. I have an e-mail off to the manufacturer, so we'll see what he says. Since my power amp has no voltage gain, I think I may very well run into this issue. Quote Link to comment Share on other sites More sharing options...
aerius Posted August 29, 2008 Report Share Posted August 29, 2008 Both AVC and TVCs will run into saturation issues, as I understand it it's a function of the core material and not the single vs. dual windings. That's why 100% permalloy is found only in small signal applications and not in output transformers. Quote Link to comment Share on other sites More sharing options...
Fing Posted September 1, 2008 Report Share Posted September 1, 2008 Fing: Are you looking to sell your TVC? I might be interested Although, I contacted Nickolas and he's willing to sell me the balanced TVCs naked for DIY use Sorry - like many audio addicts, I'm always hoping for something bigger and better down the road. Good luck with the balanced TVC's from Nick. The poor man sounds constantly inundated. Like another audio retailer we all know and love. Quote Link to comment Share on other sites More sharing options...
humanflyz Posted September 2, 2008 Report Share Posted September 2, 2008 I had a S&B unit (mark 2 i think), but I eventually sold it because it wasn't loud enough for me. But then again, I identify more closely with the postjack school of volume, and I had no complaint about the resolution/detail/tone of the TVC when I had it. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted September 2, 2008 Author Report Share Posted September 2, 2008 hm.. so, I'm not getting an overwhelming response "go try this, no one has done it". It would definitely be the road less traveled. I have ruled out the Sowter attenuator transformers, as they cannot handle the signal without saturation. In fact, as aerius mentioned, any 100% mu-metal / permalloy solution will not work unless it's air gapped to support DC. So, as far as the "coupling capacitor" hating crowd, which is worse: 1.) an attenuating resistor + coupling capacitor on output 2.) a transformer Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted September 3, 2008 Author Report Share Posted September 3, 2008 Just wanted to add this informative link to the thread: ecp.cc Quote Link to comment Share on other sites More sharing options...
n_maher Posted September 3, 2008 Report Share Posted September 3, 2008 Doug does some pretty cool stuff, yup! Quote Link to comment Share on other sites More sharing options...
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