Prometheus TVC Preamp - Removal of metal lid on sound quality

Having read some messages regarding the Promtheus preamp on the American Forums and the improvement in sound quality if the metal lid is removed I decided to have a go.
I don't know if it is all in the mind or not but the removal of the metal lid (which appears in my case to be possibly stainless steel? which I though would not have any adverse effect on the transformers) did seem to show a slight improvement in the sound quality. Has anyone else in the UK forums tried this and what were the observations?

 

the evening i had promitheus on test it clearly sounded better with a lid off. mine will be arriving tomorrow so i will be able to post more, but overall i think it's a clear mistake in design to play with an exotic wood for the case and than to put one of the acoustically the worst materials on the top of it. that's why the mentioned forums are full of recommendations to put wieghts cones cubes and all other sorts of vibration control attempts on top of promitheus - to prevent a lid from littering the sound.

 

It wouldn't be hard to replace the lid with wood or plastic, cut to fit

 

Since the transformers are (AFAIK) unshielded, it seems most likely the lid is having an effect on the magnetic field, rather than vibration. Is it a magnetic metal? An Aluminium lid may be a better idea, or even plastic as suggested. How about something covered with leather?

 

Careful there

 

well i think you can leave the stock lid and just remove it during listening, unless you have crazy pets/kids/whatever around... i wouldn't bother with making another lid but if you want to, i would go for brass.

 

"just remove it during listening" Hmm. Sounds more crazy than pets and kids

Personally I'd leave it in situ or replace it.

A summary of suggested mods from "that forum" would save having to go through 140+ pages..

 

there are no suggested mods for the lid. nick has offered some members a brass lid but not sure what happenned. i think most of the people from that forum prefer to play games with weights and stuff. it annoys me a bit because mine sits on 3 cones that are on the nick's supporting board (made of the similar wood to the TVC), sitting on another 3 cones. if i start putting weights and stuff on it, soon it will look rather like the eiffel tower!

i see no problem lifting the lid whenever using it. you just don't have to screw it so it is 1 sec operation whenever you put your music on.

 

I tried without the lid and the it sounded better ... more open (no pun intended

Infact I noticed if I tightened too much the screws for the top plate then I got better detail in all regions apart from the midrange. It wasn't a massive difference to be honest but I did notice it. I didn't like it this way and loosened the screws a bit to get the midrange better.

I've left the lid on actually. My place easily gets dusty. I think I'n done with that tweak. I gather the best tweak is remove the knobs (volume and selector) and tighten still slightly (about a 1/4 turn) the nuts. Then put the knobs back. I haven't got the correct alum key so I can't try this tweak.

- jaspal.

 

I didn't mean lid mods, I meant the various mods suggested in that thread e.g. earth cable from the transformer etc.

 

Have gone topless with my Prometheus for the last couple of days. It is now certainly less grating at the top end. Its virtues elswhere in the frequency spectrum seem unaffected. Has allowed blissful listening to 80's hairmetal! To prevent it collecting dust, simply turned it upsidedown.

 

brilliant! i wish i came with this!

although i don't get how you are using cones now?

 

Put two of the cones in the corners and one halfway along a long edge. Not totally ellegant but passable...

 

Mind you if you take the top off and use it turned over surely it has a top but no bottom - so to speak!!

 

i am experiencing a very strange thing with my promitheus - mine sounds horrible through XLR inputs: there is no bass at all and the sound is hollow, flat and compressed.

at the same time, although it has only some 50 hours on it, it's really good: very clean, rounded and transparent. it certainly lacks a bit more air and better separation to beat the best actives but for example EAR 864 has problems holding its own against it (to be polite at least).

any ideas what it is with my XLRs - just don't tell me i need to run them in too. could it be that some polarity is reversed, it reminds a bit when you mess with + and - at your speakers, except there is no fake surround effect you usually hear (IME at least).

cheers

 

Hi Gordan - wonder if there's some phasing problem? Mine was fine with XLR's, my only slight disapponitment was when using phono source - and a friend of mine with one had similar experience too. I'm currently using a tvc preamp that is fantastic beyond any tvc I've heard - shall post more in due course.

 

hi laurence,

i think too it's wrongly wired but i am checking this with nicholas at the moment. there's no way such an enormous sound difference is possible between RCA and XLR inputs without some mistake.

i am very interested in hearing more about your new TVC experience - if you read some of my recent postings, i too have spent some time listening to an amazing DIY TVC prototype unit that is well but really dramatically well beyond the S&B performance, especially in terms of dynamics, bass and PRaT.

basically both S&B and promitheus suffer from the inferior core geometry that restricts their performance. the only difference is that i beleive that given the bigger size of promitheus transformers and no shield it can be tuned and tweaked to deliver more while most likely MFA is the best S&B trannies can do, more or less.

cheers