TVC preamps - your experiences

[petrat]

Transformer volume control preamps have been around for more than a decade, in the UK being popularised by Music First Audio products. As an attenuation solution, they would seem to have some real benefits. What are your experiences?

[Mika K]

Haven't used one myself but one friend was using one in his system and says this is far more transparent solution than the passive Alps potentiometer in his other preamp. Later he has updated to pretty expensive tube preamp and TVC is acting as spare as it has good sound quality compared to the pricing, if thinking these cheap ones..

Personally I think that the system synergy is the key here as I have understood that the TVC preamp is far more sensible to electrical parameters of the other components and interconnects etc. than the other solutions.

[jandl100]

I've had several, including ...

http://i262.photobucket.com/albums/ii114/jandl100/DSCF7884.jpg (http://s262.photobucket.com/user/jandl100/media/DSCF7884.jpg.html)

http://i262.photobucket.com/albums/ii114/jandl100/Django%20pre1_zps2nrjz481.jpg (http://s262.photobucket.com/user/jandl100/media/Django%20pre1_zps2nrjz481.jpg.html)

http://i262.photobucket.com/albums/ii114/jandl100/TVC%20pre%20front_zpstk3w3df7.jpg (http://s262.photobucket.com/user/jandl100/media/TVC%20pre%20front_zpstk3w3df7.jpg.html)

Nicely transparent and detailed in a somewhat smooth way. Seem to have more heft than standard passives. But, tbh, they seem a bit boring and 'slow' to me now. Give me a good active pre any day. :)

[Haselsh1]

For the amount of money Croft are asking for their Micro 25 Basic is there any point...? This even includes a genuine valve phono stage as well.

[Reffc]

I've had several, including ...

http://i262.photobucket.com/albums/ii114/jandl100/DSCF7884.jpg (http://s262.photobucket.com/user/jandl100/media/DSCF7884.jpg.html)

http://i262.photobucket.com/albums/ii114/jandl100/Django%20pre1_zps2nrjz481.jpg (http://s262.photobucket.com/user/jandl100/media/Django%20pre1_zps2nrjz481.jpg.html)

http://i262.photobucket.com/albums/ii114/jandl100/TVC%20pre%20front_zpstk3w3df7.jpg (http://s262.photobucket.com/user/jandl100/media/TVC%20pre%20front_zpstk3w3df7.jpg.html)

Nicely transparent and detailed in a somewhat smooth way. Seem to have more heft than standard passives. But, tbh, they seem a bit boring and 'slow' to me now. Give me a good active pre any day. :)

+1

[CornishPasty]

Jandl, I also have a Django TVC which I quite like but only in the 6db lift mode. In 0db I find it limp and lifeless like most passives. I also have a preference for a good active preamp but I feel if I could get more gain from my Django the tables might turn. If I had the money I'd commission someone to make me a pair of transformers with primary windings capable of a 12db lift, if that was possible.

[walpurgis]

My MingDa MC-9 TVC unit sounds amazing (looks great too).

I agree about most passives being a bit disappointing, but this runs circles around every pre-amp I've owned so far and I've had some decent actives too.

[jandl100]

Ralph, I find myself a bit baffled as to how extra gain changes anything. :scratch: - surely it's just the same as turning the volume knob round a bit further? - unless there is insufficient overall system gain to achieve the sound levels you wish?

Or does the +6dB option include some sort of 'turbo charge' with your unit? -- sorry if that sounds sarcastic, not intended!

I must admit I recall no added sound quality from the +6dB switch on the TVC amps I used with that facility.

[Marco]

It’s not about gain; it’s about impedance matching. Quite simply, some power amps just don’t ‘like’ passive preamps, resulting in a partial, or total electrical and sonic mismatch.

To do it right, you need to factor in the use of a passive preamp/volume pot at the design stage of the partnering power amp. This something, for example, that NVA designs get right.

Marco.

[jandl100]

Ah, so does the impedance matching change with the +6dB switch, which is what I think Ralph was referring to?

[Marco]

Nope, but the sound will be louder, at a given volume level, which if the impedance match is bad with the partnering power amp, can give the impression of more drive and ‘life’. That may be why Ralph finds the results more preferable, when using the switch :)

Marco.

[CornishPasty]

That's more or less it Marco. The input impedance of the Django TVC changes according to which way the primary windings are connected. In 0db mode I find the Django lacking, no flesh on the bone is the best way I can describe it. In 6db mode it pretty much approaches my Grounded Grid valve preamp for good solid sound but is still a bit lacking in gain. In 6bd mode though it will drive 8 metre interconnects to the solid state amps situated either side of my speakers.

[petrat]

I've had both results. When I first tried a TVC, about a decade ago, I came to the same conclusion as Jerry and others ... nicely detailed, but gutless. BTW, the amps I was using at the time were all solid state, with input impedances of less than 20KOhms.

More recently, hearing one with my present power amp in Montesquieu's system gave a result which was much more convincing, which we attributed, perhaps, to TdP having designed the EAR circuit to match with a 'passive' pre (as per the 834 integrated). Further experiments showed a brilliant match when sourced by my CD player, which has a well designed (valve) output stage feeding both RCA single-ended and transformer-coupled XLR balanced outputs. Unfortunately, it was not so good with a couple of solid state phono-stages, although the use of the +6dB windings did improve things considerably, but there was still a sense that the phono-stages weren't really up to 'driving' the system properly.

Reading around other forums, there seems to be a consensus that the +6dB switch should be employed, with a few suggesting it is best to use the balanced inputs/output in preference to the RCAs, in conjunction with sources designed to drive balanced cables. I've been trying to work out what is going on, technically, but it isn't anywhere near as simple as the calcs for a passive pot :scratch: I intend to persevere with finding a capable phono-stage, as the potential performance gains would seem to be well worth the effort if the results with the CD player are anything to go by.

Any further experiences / thoughts, anyone?

[CornishPasty]

The Django balanced input/outputs are not true balanced. You would need four transformers to achieve that. I was looking at a true balanced TVC earlier in the week. I can't remember who made it but it was certainly out of my league at 9K or thereabouts. Anyway mine was diy built as were most of them and it was a bit of a mess tbh. The rca to xlr switching was an absolute crows nest so I ripped it all out and it's just unbalanced rca phonos in and out now. I'm sure it sounds better as a result.

[petrat]

The Django balanced input/outputs are not true balanced. You would need four transformers to achieve that. I was looking at a true balanced TVC earlier in the week. I can't remember who made it but it was certainly out of my league at 9K or thereabouts.

Not sure about that :scratch: I thought transformers are inherently 'balanced' if the windings are not grounded on one terminal (i.e they are 'floating'). That's why the MFA TVCs have a 'ground' selector switch for selecting RCA or XLR.

[CornishPasty]

Sorry Petrat, I got a bit in front of myself there. Yes you can do balanced on one transformer if it has a centre tap and when I said four transformers I should have said two per channel. I was referring in particular to the Audio Music RS balanced transformer preamp. Most TVCs don't have centre tapped transformers, one end being referenced to ground hence my suggestion for four transformers (two per channel)

[hifinutt]

absolute BIG fan of tvc`s
you can see more here

http://www.hifiwigwam.com/showthread.php?106175-music-first-audio

had the classic mark 1 silver which blew away my bel canto pre 3
then the mark 2 silver
later had the baby reference which I had concurrently with a arc ref 5se and it was well up to the ref
then later and now have a mfa copper mark 2 [mark 3 transformer]
it really gels well with my class a power amp . it is stonking good value

it has slightly different presentation to a valve amp but I love the detail and zing and sheer musicality
I have also had a Silverstone tvc for a few weeks and a sonic euphoria but none of them I have found is as good as the mfa

[petrat]

Interesting, Phil. Any views on compatability with source components, such as phono-stages?

[lurcher]

Sorry Petrat, I got a bit in front of myself there. Yes you can do balanced on one transformer if it has a centre tap and when I said four transformers I should have said two per channel. I was referring in particular to the Audio Music RS balanced transformer preamp. Most TVCs don't have centre tapped transformers, one end being referenced to ground hence my suggestion for four transformers (two per channel)

You don't need a centre tap to be balanced, purely isolated floating outputs are perfectly balanced (as long as the capacitance to ground from both outputs are the same). the centre tap is created at the input side if needed. The only time you would need a centre tap on the output is if the input it is going into is not a proper balanced one. In that case the fault is in the input not the output.

[The Black Adder]

I too like TVC's. The only thing is that I found them to not be able to drive the music as well as a well sorted active pre. But this isn't a bad thing, just a different flavor. Top quality passive and active pre's are different and not better or worse. They have a way that suits both listeners and musical styles.

The only thing that irks me is when Music First says that their pre's are 'the best in the world' - talk about a blanket statement. But never the less, Music First pre's are lovely.

If I was to go away from my Croft I'd have a Music First TVC.

I'm also a fan of balanced connections (although with only a limited experience of such) - I had balanced when I had my Chord set up... compared to unbalanced the sound was definitely much more engaging. Explanations on a postcard. :)

[hifinutt]

Interesting, Phil. Any views on compatability with source components, such as phono-stages?

I don`t have any problems at all . the tv is a bit soft sometimes but I just turn it up

[hifinutt]

I too like TVC's. The only thing is that I found them to not be able to drive the music as well as a well sorted active pre. But this isn't a bad thing, just a different flavor. Top quality passive and active pre's are different and not better or worse. They have a way that suits both listeners and musical styles.

The only thing that irks me is when Music First says that their pre's are 'the best in the world' - talk about a blanket statement. But never the less, Music First pre's are lovely.

If I was to go away from my Croft I'd have a Music First TVC.

I'm also a fan of balanced connections (although with only a limited experience of such) - I had balanced when I had my Chord set up... compared to unbalanced the sound was definitely much more engaging. Explanations on a postcard. :)

as I say I have compared them with lots of actives and find they drive very powerfully . huge dynamics

[Marco]

I don`t have any problems at all . the tv is a bit soft sometimes but I just turn it up...

You see, Phil, that would bother me, as something sounding ‘soft’ fundamentally isn’t right. What happens if you want to listen at low levels, but don’t want any ‘softness’? If the only way to solve the softness is to turn up the volume, then that isn’t a cure, merely a distraction.

I know exactly what you mean about the softness, and it’s precisely what I don’t like about passives. Good active preamps never sound soft (unless there’s an electrical mismatch with the partnering power amp), no matter the listening level! :nono:

Marco.

[walpurgis]

No lack of 'wellie' nor any softness with mine. Quite the contrary, dynamics are superb and bass is deep and extremely tight. The transparency is in a different league to any active pre-amp I've used.

[hifinutt]

well the tv output has to travel 10 metres via an optical connection so it has probably not got a lot of welly. its fine when you play a dvd . for some reason that is the same volume as everything else . perhaps I just need to adjust the tv

however all other sources are just fine and extremely good

[Marco]

That’s cool, Geoff. I think we’ve all had different experiences with active and passive preamps, notwithstanding the necessity for either to match properly (in terms of sensitivity/impedance) with the partnering power amp.

I was simply responding to Phil’s mention of softness, as I’ve heard that effect before with passives, and I simply couldn’t live with it.

My experience, to date, differs from yours in that I’ve yet to hear a passive preamp with the ‘balls’ and sheer ‘clout' of my Croft, which also has every bit as much transparency as any passive device I’ve heard :)

Marco.

[AndrewL]

No lack of 'wellie' nor any softness with mine. Quite the contrary, dynamics are superb and bass is deep and extremely tight. The transparency is in a different league to any active pre-amp I've used.

TVC need to be driven properly, call it synergy, if you will, get it wrong and they will sound anything from slow to truly pants, believe me I know, get it right, assuming the TVC designer knew their onions, and you'll be rewarded a very transparent and incredibly neutral experience that lacks nothing.

[hifinutt]

if I play you james blake `limit to your love` through my passive from a sonos your chest will be shaking from the huge depth of sound and dynamics and that's with the speakers turned down [they are adjustable for bass]
it matchs any active and I have had 15 pre amps at least in recent years

when I had someone round to hear my ref 5 vs the mfa baby they almost preferred the baby !