Pre-amp for newly acquired ATC SCM40A's

[hifinutt]

i use a passive /valve pre which costs about 760 new with a remote . its american made . it is incredibly transparent but the sense of live recordings is pretty marvellous . for the money its a cracker BUT i am not sure if it would match the atc . one would have to try it . must say since i changed to tungsol valves i have really been enjoying it with the big horns . very very real sound . i think a MFA might have more bass and slam though than this pre which is totally linear in presentation . In my loft room i can`t have too much bass so it suits well . it has xlr in and out 

 

[TheFlash]

TVC-based solid-state passive pre-amp

Could there be such a thing? 

You may be being a smartarse, in which case I would wager you think "solid-state" is redundant; or you may not, in which case I don't understand your point!

 

[greybeard]

You may be being a smartarse, in which case I would wager you think "solid-state" is redundant; or you may not, in which case I don't understand your point!

Solid-state and passive, do not seem to go together, surely it can be one, or the other. And thanks for the compliment, I haven't been called smart in along time 

 

[TheFlash]

Solid-state and passive, do not seem to go together, surely it can be one, or the other. And thanks for the compliment, I haven't been called smart in along time 

Yes, I guess you're right as a passive re typically has no power supply... I say typically because the icON does but this is to power the display not anything in the playback chain.

So there are four broad classes of pre-ampifier: passive TVC (eg. MFA), passive attenuator (eg my vintage Rotel RHC.10 and a bunch of cheap generic passives on eBay), solid-state active (eg. ATC SCA2) and tube active (eg. Audio Research LS15). Passive TVC is the closest to "straight wire".

 

[TheFlash]

Yes, I guess you're right as a passive re typically has no power supply... I say typically because the icON does but this is to power the display not anything in the playback chain.

So there are four broad classes of pre-ampifier: passive TVC (eg. MFA), passive attenuator (eg my vintage Rotel RHC.10 and a bunch of cheap generic passives on eBay), solid-state active (eg. ATC SCA2) and tube active (eg. Audio Research LS15). Passive TVC is the closest to "straight wire".

Oh, and the only passives which will work with my SCM40A's are TVC as I need something which will drive 5m cable runs. Read the Tortuga website's arguments for passive vs active pre's and they're quite persuasive but then they suggest keeping cable lengths to under 6ft (2m).

 

[greybeard]

I use a passive, which is just an Alps pot with silver wire to the 5 inputs and 1 output, which I knocked up a few years ago now, it produces a very smooth, detailed sound, which I really enjoy listening to, I also have a damaged(a long story) Prometheus TVC, which if memory serves me well, was also to my liking. I must get round to fixing it, and see how it compares to my cheap DIY effort. 

 

[TheFlash]

I use a passive, which is just an Alps pot with silver wire to the 5 inputs and 1 output, which I knocked up a few years ago now, it produces a very smooth, detailed sound, which I really enjoy listening to, I also have a damaged(a long story) Prometheus TVC, which if memory serves me well, was also to my liking. I must get round to fixing it, and see how it compares to my cheap DIY effort. 

Indeed! Might I presume modest cable lengths of 1-2m might be involved too? That does broaden the field.

 

[greybeard]

Might I presume modest cable lengths of 1-2m might be involved too?

Yes, no more than a metre.

 

[TheFlash]

Yes, no more than a metre.

Fine for the ALPS device then. The Promitheus TVC would handle my 5m lengths too.

 

[George 47]

I had a dabble with passives a few years ago and the results were interesting (to me anyway). The classic passive was the Hattor which used Takman resistors in a stepped array. They were truly balanced having 4 sets of stepped resistors. It also had remote volume control and input selection. To me they were incredibly neutral and transparent but could sound a little less exciting than the Pass Labs XP12. The dynamics sounded slightly subdued and the bass had less impact. Oddly enough they worked better in balanced mode. I liked what they did.

I used a Promethieus TVC and although a little crude in construction they overcame the bass and dynamics issues so I sold it and listened to a 'better' constructed TVCs. The MFA copper was a much better constructed passive but it did not work too well with my ARC valve Ref 110 power amp, so I sold it. The balanced inputs sounded much the same as the RCAs. I then tried a Townsend Allegri which for me provided the best of all worlds but it is totally single ended. It had the clarity of the other passive with bass and dynamics. but its inputs used a cheap set of RCA sockets on a strip which precludes the use of decent wide cables. I used long cables on the Allegri and it did not seem to cause any problems.

Following that lot I tried to rationalise what I heard and 'think' that the problems with the resistor passive were from matching impedances .

The MFA is not a true balanced passive as there is only one transformer per channel, which may account for there being no differences between RCAs and balanced. There are TVCs out there that use 4 transformers and are true balanced passives. My fave is the Allegri as that gave the best of both worlds but it does not have balanced inputs/outputs. A few of my 'trusted' reviewers use the Allegri and consider it the bees knees. Martin Colloms loves it and was on his second when I last spoke to him. Max has just released a bells and whistles version with balanced inputs/outputs and RCAs and a headphone amplifier. I suspect it won't be cheap.

Despite that I like the sound quality, convenience of the XP12 and its balance control.

Have fun listening comparing measurements.

 

[Nopiano]

I’ve been struggling since yesterday to know what TVC stands for. I thought maybe Thermionic Valve Controller at first, but is it Transformer Volume Control?  

 

[George 47]

I’ve been struggling since yesterday to know what TVC stands for. I thought maybe Thermionic Valve Controller at first, but is it Transformer Volume Control?  

That's the blighter. Although Max Townsends version is actually an autoformer not a transformer. Another damn term...

 

[gryphon]

Maybe a Vincent SA-7 would be a pre of interest!, tubes and measuring very well.

 

[Fourlegs]

One of my favourite active preamps is the Icon Audio LA5 TX. As an aside this uses output transformers which is unusual for a preamp but helps it to drive long cables runs. It also uses the 6SN7 valves which are possibly my favourite signal valve for sweetness and bass. And for the ATC speakers it had XLR balanced outputs.