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  1. #1
    All Ears Eckythump's Avatar
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    Promitheus TVC Passive Preamplifier

    http://www.promitheusaudio.com/tvc.htm



    Evening all

    As a follow up to my recent thread seeking some inspiration regarding preamps and DACS I thought Iíd follow up with a little review.

    I acquired some Quad ESL-57 speakers about 6 months ago and have them in my 3.5m x 2.5m listening room, sat pretty near field, about a 2m triangle, 12Ē off the floor. This suits me fine as I listen alone so always get the sweet spot. I also come to hifi fresh from a journey through headphone land and found my preference there was the AKG K701, a fast, dynamic can with accurate but not prominent bass. I find myself leaning in that direction with speakers too.
    The Quad 303 I got has been recapped and serviced and the CD player is a joy to use. Both are going nowhere. Once I find something that is right, I like to fit and forget.

    I was using a Dacmagic and a Quad 33 (serviced) in the mix. I didnít feel the DAC added anything compared to the CD player and was only making the streamed music sound better so I decided to move it on. I had read various things about the Quad 33 being way outclassed by modern preamps, (upgrades etc were another £100+), and although I thought it sounded good, I was keen to try something else. I couldnít afford to keep the preamp and buy another to do a comparison so I took a gamble and sold it.

    After a brief spell of panic at having no hifi to listen to I got hold of a Promitheus TVC passive preamp through this very same Wam. It is the latest model, still has wooden knobs and sides with the metal plate top and bottom. Looks a bit strange in the rack with a champagne Sony and a Quad but passed the wife test as she thought it matched the sides on the speakers. Using 1 metre Hitachi interconnects. QED 79 strand speaker wire.
    I wonít begin to get all technical and explain how it works. My understanding is that if you imagine the music is a car, a normal passive has full throttle all the time and applies the brakes, a TVC changes down a gear. If you are like me and donít care that much how it looks or works, just how it sounds, then read on.
    Turning the volume up on the Quad 33 with no music playing, there was a definite background hiss. With the TVC I now understand when people talk about music coming out of a black background, there is not a sound either with no music playing or in between passages. Normal listening volume is between one third and half way on the wooden dial.

    There is a distinct change to the imaging / soundstage. With the Quad 33 it was more centralised, e.g. with good recordings you still got good separation of instruments across the room but they all seemed to lean towards the centre and the very far right and left was only reserved for the odd effect. The TVC has widened things even further and Iím now hearing placement of individual drums in a kit, rather than just the position of the drum kit. There is certainly more detail than before and Iím hearing a different character to the sound which I presume is the CD and amp together with no interruption, rather than having the Quad 33 in the path.

    I can only take it on faith that the TVC adds nothing to the sound. It certainly seems to work fine with my amp and so I can see no reason to change it. What I can do now is hear what my amp and CD player can do alone and then properly judge a new DAC when the funds allow.
    Hope this makes some degree of sense. Iím not up on all the technical jargon; just tell it how I find it.
    "Nothing is something worth doing"

  2. #2
    Super Dooper Wammer hifinutt's Avatar
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    good to see a perspective on a good priced passive . looks the business
    You might slip, you might slide, You might stumble and fall by the roadside, But don't ever let nobody drag your spirit down, Remember you're walking up to heaven
    Don't let nobody turn you 'round, eric bibb

  3. #3
    Super Wammer JANDL100's Avatar
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    The Quad 33 was never one of the brightest stars in the world of pre-amps.
    I think you'll find you are hearing more and more music with the TVC passive as you settle in with it and re-explore your music collection.
    You'll be starting to hear what those fab Quad 57's of yours can really do!

    Quote Originally Posted by Eckythump View Post
    I can only take it on faith that the TVC adds nothing to the sound.
    Well, everything adds (or subtracts) something from the sound. But those TVC pre-amps are excellent, ime, pretty much regardless of price, and don't suffer the softening of dynamics and slack 'jump factor' that can plague some passive pre-amps. Very very transparent and detailed, too.
    You have to spend a lot of £££ on an active pre to match them, imho.
    Last edited by JANDL100; 09-12-2011 at 07:37 AM.
    Life's too short for boring hifi!

  4. #4
    Super Wammer JANDL100's Avatar
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    BTW - a lot of folks, myself included, find that raising the Quad 57's off the floor makes them sound even better.

    Pretty much any sort of support will do - I've used plastic 'step-up stools' about 8 inches high to excellent effect! £2 each from the local household shop - the Quad stats really aren't at all fussy about having a fancy 'audiophile' stand.
    You have to experiment a bit to get the vertical angle right, and tbh they are not very stable if you have young kids or big dogs around. But as long as that's not a problem short stands like those in the photo are well worth trying.

    Last edited by JANDL100; 09-12-2011 at 07:41 AM.
    Life's too short for boring hifi!

  5. #5
    Super Dooper Wammer Cable Monkey's Avatar
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    I think people need to try a TVC pre at some point in their hifi journey. It is not a given that you will like what you hear, but it can give you a perspective on music that can cost thousands to acheive with an active. As above I would agree that the 33 is hardly a fair comparison given its age but it helps that the 303 (and other Quads) work well with passives which is even more important than usual with regards to matching.
    Let me get this straight. You take a perfectly good CD and put it in a DVD player??!!

  6. #6
    Moderator gjm's Avatar
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    Quote Originally Posted by Cable Monkey View Post
    I think people need to try a TVC pre at some point in their hifi journey. It is not a given that you will like what you hear, but it can give you a perspective on music that can cost thousands to acheive with an active. As above I would agree that the 33 is hardly a fair comparison given its age but it helps that the 303 (and other Quads) work well with passives which is even more important than usual with regards to matching.
    TVCs and passives are very interesting pieces of kit and definitely something most people should try. As with so much else, the suitability depends on what else you use - bear in mind that an active pre-amp will probably add gain, while a passive will not.
    The best hifi show in the UK today - http://www.thehifishow.com/

  7. #7
    Super Wammer SMEagol's Avatar
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    The prometheus is great value, even with its flintstones aesthetic! I have a Lumley passive and its one of the best bits of kit I ever bought!.
    "Before you play two notes learn how to play one note - and don't play one note unless you've got a reason to play it."
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  8. #8
    All Ears Eckythump's Avatar
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    [QUOTE=JANDL100;1139292]BTW - a lot of folks, myself included, find that raising the Quad 57's off the floor makes them sound even better.]

    Mine are currently sat on two black Ikea Lack side tables with their legs cut down in size so the ESL centre is level with my ear. The speakers just sit nicely on the diagonal and I got the angle right by shoving a CD case under the back of each.

    A bit rough and ready but even Peter Walker said to just use beer crates!
    "Nothing is something worth doing"

  9. #9
    Super Wammer
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    I initially (mid/late 80s?) used a simple pot to replace a Quad 33 feeding a Quad 303. Many years later it was a ladder attenuator feeding a Moon W5, when I discovered that the, cheaper, Promitheus, did a better job. It was in turn replaced by the original MF TVC. Given the difference in cost between it and the Promitheus I did not want it to sound better, but it did and I had to get it. However with subsequent changes in amps (and source and speakers) I found direct feed from the CDP was even better. But even this was beaten by recently by an audition of a rather fancy valve active. Admittedly said valve active would cost me more than 20X, what I paid for my 2nd-hand Promitheus and infinitely more than direct feed, so the law of diminishing returns kicks in very hard!


    BTW many TVCs, including the MF, do offer some gain if required. I don't know whether this negates their advantages as I didn't try it since I didn't need the gain

    Quote Originally Posted by gjm View Post
    TVCs and passives are very interesting pieces of kit and definitely something most people should try. As with so much else, the suitability depends on what else you use - bear in mind that an active pre-amp will probably add gain, while a passive will not.

  10. #10
    Super Wammer HectorHughMunro's Avatar
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    I found that there was a touch of colouration to the Promitheus; it imparted some (not unwelcome) warmth to the system that I was using at the time. In terms of quality, it thrashed the Quad 99 pre, Tag AV32r and Tag PA10. It was only supplanted by the Musical Fidelity Nu-Vista 300 pre with full in-house Musical Fidelity mods.

    For the money, the Promitheus is massively recommendable if your system is compatible.

    One caveat is that you should have a look at the forum; http://www.audiocircle.com/index.php?board=130.0 . I should say that my personal experience was very good and I had no problems at all.

  11. #11
    Super Dooper Wammer hifinutt's Avatar
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    Quote Originally Posted by Cable Monkey View Post
    I think people need to try a TVC pre at some point in their hifi journey. It is not a given that you will like what you hear, but it can give you a perspective on music that can cost thousands to acheive with an active. As above I would agree that the 33 is hardly a fair comparison given its age but it helps that the 303 (and other Quads) work well with passives which is even more important than usual with regards to matching.
    yes agreed , tvc passives are a delight and certainly the sonic euphoria i am using currently with my focal diablo is a delight, no hardness, no clinical sound just big soundstage and very nice. its not as detailed as the mfa but its good
    You might slip, you might slide, You might stumble and fall by the roadside, But don't ever let nobody drag your spirit down, Remember you're walking up to heaven
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  12. #12
    Super Dooper Wammer Cable Monkey's Avatar
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    A hint for the Sonic Euphoria. Use shorting plugs on the unused inputs and things get better.
    Let me get this straight. You take a perfectly good CD and put it in a DVD player??!!

  13. #13
    Wammer john dolan's Avatar
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    I have the Glasshouse TVC and the Glasshouse passive with noble pot and ive just ordered some shorting plugs for a try.

    Would you use them on inputs only and not the spare pre out and tape out sockects or do you think i should get more and use them on those sockets also ?

    Ive ordered 3 pairs of these

    http://www.hificollective.co.uk/cata...ir-p-4271.html
    john dolan

  14. #14
    Wammer john dolan's Avatar
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    The shorting plugs arrived and they have made a big improvement and i mean BIG.
    john dolan

  15. #15
    Super Dooper Wammer Cable Monkey's Avatar
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    Didn't see your previous message until now. The plugs you have purchased should be fine for active outputs as they are not a dead short but have a 5K resistor as explained on your link. However as our devices are passive, nothing is going to blow up so the expense of nice gun metal plugs isn't really necessary to me. I got the cheapest phono plugs Maplin do and soldered a dead short on them to be used on the inputs only. These inputs had a lot of noise when switched through the pre-amp. I surmised that this noise probably induces noise in the channels actually used although at a much lower level. Shorting these unused inputs silenced that noise and made a difference that was audible to me when I played music, particularly via a phono stage on the input. I imagine however that it will not make any difference on a pot based passive or for that matter a switched resistor passive (though I am happy to be proven wrong). I am trying to figure out if shorting an unused output is worthwhile on a TVC. I have a feeling that shorting a secondary is not a good idea but terminated with a 5k resistor might be another matter. As it stands I was quite happy with the improvement simply by shorting unused inputs.
    Let me get this straight. You take a perfectly good CD and put it in a DVD player??!!

  16. #16
    Wammer john dolan's Avatar
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    Im using the shorting plugs on my glasshouse passive that has the Noble pot ive not tried them on my TVC yet so yes they do improve a pot based passive.
    john dolan

  17. #17
    Wammer
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    used to have one back in the days. it didnt score too well against both MFA copper TVC and EAR 864 tube WOT active. both stomped it either on clarity (TVC) or drive (EAR). could be that the version with bigger TXs sounds better. its good for what it does: to show that plenty of active preamps on the market are crap as well as to expose rather extraordinary potential of inductive volume control as such. but for top performance and built quality, you have to seek elsewhere.
    Horn OK Please!

  18. #18
    Super Dooper Wammer Cable Monkey's Avatar
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    Quote Originally Posted by anubisgrau View Post
    used to have one back in the days. it didnt score too well against both MFA copper TVC and EAR 864 tube WOT active. both stomped it either on clarity (TVC) or drive (EAR). could be that the version with bigger TXs sounds better. its good for what it does: to show that plenty of active preamps on the market are crap as well as to expose rather extraordinary potential of inductive volume control as such. but for top performance and built quality, you have to seek elsewhere.
    So we are comparing a $420 rrp product with £2000 plus for the basic MFA? How much for the EAR? And how much would you pay for something with both better clarity and drive because the way you describe it, neither of your alternatives were universally better.

    John,
    that is interesting news because it does suggest there is scope to improve most passives by paying a little attention to detail. I imagine the likes of MFA may have already paid that attention (hence the price).
    Let me get this straight. You take a perfectly good CD and put it in a DVD player??!!

  19. #19
    Wammer john dolan's Avatar
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    My brother built a Wad valve pre and that uses a relay to switch off unused inputs so even active preamps benefit.

    Heres a pic of my passive

    john dolan

  20. #20
    Wammer john dolan's Avatar
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    Today i thought id try the shorting plugs out on my Glasshouse TVC passive and got the same result of improved sound that i got with the Noble based passive.

    The sound of the TVC is now more relaxed focused and refined.

    In comparison with the Noble passive i think the TVC is better in hifi terms but it always seemed to have a slight edge to the sound that the Noble passive didnt but fitting the shorting plugs this slight edge is now gone and they both sound very close now but where the TVC pulls ahead is with my opera recordings which have greater dynamics and a little more attack when the music hits climaxes.

    Im not sure but the transformers inside my Glasshouse TVC look like the ones inside the Promitheus.

    Heres a pic of my TVC that brother Dik built for my 50th

    Last edited by john dolan; 17-12-2011 at 09:00 AM.
    john dolan

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