Fully ballanced valve preamps

can't wait to hear

 

There's not much to tell really.

We tried Glasshouse, DACT, MF and Rob's WAD active pre. My order of preferrence was (starting with the best) MF, Rob's WAD, DACT and Glasshouse.

For detailed analysis, over to Tenson & Rob.

 

Hi,

All I can say is that the Glasshouse one sounded really odd. I suspect the resistors used, despite being "Dale/Vishay" are of questionable quality. Only two of them are in circuit per step yet they managed to make the music really thin, lean and threadbare with a substantial loss of resolution. I suspect a £ 1 Alps carbon Pot would have made a more realistic sound. It reminded me of Kondo's condemnation of stepped attenuators he gave once, he called it "hilarious dummy sound".

The DACT didn't do any of that, suggesting that the results from the Glasshouse passive where not due to a system mismatch. The DACT sounded to my ears "typhically resistive passive", clean, open but laking some drive, get up and go and dynamics.

Rob's Pre sounded rather nice in context but gave up some resolution and dynamics to the best, but in a perfectly agreeable way. Interresting that a simple Pot plus Valve Stage and output transformer managed so notably better than DACT's "high tech passive".

That said, this kind of circuit has always been my preference if an active preamp is really needed (see my Article on the Euridice in the London Live DIY HiFi Circle newsletter and also the DIYHiFiSupply Tram). I still might build me one like that, but based around around the most recent version of the Euridice (battery bias, S&B TVC as Volume control, S&B superpermalloy parallel feed output transformer and S&B 50% SuperpermalloyAnode Choke)

Past that I felt the MFA PMP did what it was supposed to do, get out of the way of the music.

Ciao T

 

Thats definately not the case thorsten. I use the same stepped attenuator in my valve pre, and it sounds significantly better than the alps blue pot that proceeded it.

I suspect that its a matching question, either system matching or perhaps not the best rating on the attenuator for his power amplifier.

 

So a £1,500 preamp bettered a number of £400 preamps in most areas?

Is that really surprising?

 

Shocking I'd say

 

yes... in this case.

 

Chris, as I told you before, don't take this personally. It's all good fun.

 

personally? mee? never!

its all bollox hifi nonsense anyway...!

 

Hi,

In Dev's system almost exactly that was the case. The WAD Preamp has a normal Pot (Alps Blue) and on top of that a Triode stage and an output transformer.

It is hard to say, I can only comment on what we heard. Maybe Simon or Rob would comment?

Ciao T

 

Hi,

Actually, a Preamp selling for £ 1,500 assembled through dealers vs. a £ 400 Kit, unassembled, sold direct.

If it was sold in a normal HiFi Shop you might find that both items would probably end up at approximatly parity, possibly with the WAD Pre II ending up costing more. Just for fun, the single box, transformer less EAR 834L sells for £ 1,100, the WAD Preamp contains a lot more actual parts in terms of cost.

Ciao T

 

then how can you explain my Consonance Basie sounding so much better when replacing the stock Alps blue pot with the Glasshouse stepped attenuator?

 

Because it is buffered by the tube output stages?

I think what T is saying is that a Alps pot in front of an active output stage is better than the stepped attenuator on its own.

 

I'm in general agreement with the order of preference - MF/WAD/TACT/Glass - except in one crucial area (for me) - timing.

I thought the WAD was a tad tighter and more propulsive on rhythms but it gave up some detail and spaciousness to the MF for sure. The differences wouldn't make me want to change at this stage though. Thorsten suggested a small mod to the WAD to improve performance so I'll give that a try.

As ever with these things, so much depends on impedance matching, particularly with the simple 'pot in a box' type units which can sound excellent in one system and dire in another.

 

Hi,

No idea. I did very little work on the "Basie", it was basically a design by Opera which after trying one realhi-fi never imported while distributing Opera (after listening to it).

I guess the answer is synergy.

Ciao T

 

The whys and wherefors are unimportant, the fact is the user ends up paying four times as much for the TVC. Comparison with an active tube stage c. $2950 new would be a better way of establishing the MFA's ranking - and my experience suggests you may well find a very different result.

I see a number of these MF units appearing on the used market already. Might be a bargain but I always wonder why they are being sold.

 

maybe it's the same person, the asking price is 950 pounds by rule:MILD:

 

Hi,

The user ends paying nothing for a kit of parts directly from the factory as he does not buy them. In fact the WAD Preamp Kit is gone and not available at all.

But clarly you are someone who would expect to go to a Porsche Dealer and pay the same for a brandnew Porsche there as you would for a parts kit fror a factory direct selling Kit Car. Dream on.

Well, a substantial number of noted reviewers (and customers) seem to disagree with you. But sound is a subjective thing. I can even imagine someone prefering a 20 years old used NAD Preamp, except that person is unlikely to be me.

Ciao T

 

Je suis ravi de mon S&B Django!

One advantage of TVCs, which is often overlooked, is their ability to preserve dynamics and detail at low volumes due to I/V conversion (as voltage drops, current increases). In my case, because I have the restraints of living in a flat, this is a huge advantage over other types of volume control. I've tried alot of active/passive preamps in my system; none were as transparent as the TVC. I won't be selling my TVC anytime soon.

 

T, do you maybe know if transformers in bent NOH are the original S&B, or they are made by john chapman according to S&B specs?

and does it really matter? i noticed that many TVC followers actually rave about the principle and not only about a particular model - would it make sense (for us trying to reach hi-end on a shoe string) to go for something cheaper s/h - such as NOH - instead of MFA that is out of range... are the differences really significant?