Too much gain

[Slawts]

This has been something that has been bugging me slightly for a while but became more apparent when my pre came back from repair. In its absence I have been using an Audiolab Q Dac as a pre with my XTC Pow1 power amp and it is absolutely quiet when on.

Putting back my VTL 2.5 pre there is audible hiss when no music is playing and it is not on mute.

I only use the volume control between 7 and 9 o'clock as that is at 9 it is extremely loud so am thinking the pre is too high gain.

I am looking for a cheap solution and have thought about trying some attentuators (Rothwell?) but am concerned it degrades the sound.

Would changing valves in the line section help? They are ecc82's feeding in to 6350's and I was thinking about trying a lower gain version of an ecc82 equivalent.

Steve

[Stryder5]

This has been something that has been bugging me slightly for a while but became more apparent when my pre came back from repair. In its absence I have been using an Audiolab Q Dac as a pre with my XTC Pow1 power amp and it is absolutely quiet when on.

Putting back my VTL 2.5 pre there is audible hiss when no music is playing and it is not on mute.

I only use the volume control between 7 and 9 o'clock as that is at 9 it is extremely loud so am thinking the pre is too high gain.

I am looking for a cheap solution and have thought about trying some attentuators (Rothwell?) but am concerned it degrades the sound.

Would changing valves in the line section help? They are ecc82's feeding in to 6350's and I was thinking about trying a lower gain version of an ecc82 equivalent.

Steve

I tried attenuators both home made and from various branded suppliers, and found degradation of sound. I only speak from my opinion on my system.

Did your VTL exhibit this hiss before repair, assuming it was working at that time.

What was the issue before repair, and what was done?

Gary

[Slawts]

I tried attenuators both home made and from various branded suppliers, and found degradation of sound. I only speak from my opinion on my system.

Did your VTL exhibit this hiss before repair, assuming it was working at that time.

What was the issue before repair, and what was done?

Gary

Yes always hiss with the XTC. I used a VTL ST85 power before and no issue but it couldn't drive my speakers the way the XTC does.

The repair was replace the selector switch and clean the balance and volume. Well worth it as it sounds better except for the hiss.

I have heard similar about the attentuators that's why I'm not so keen.

[Stryder5]

Yes always hiss with the XTC. I used a VTL ST85 power before and no issue but it couldn't drive my speakers the way the XTC does.

The repair was replace the selector switch and clean the balance and volume. Well worth it as it sounds boetter except for the hiss.

I have heard similar about the attentuators that's why I'm not so keen.

Just maybe one of those mismatches that appear occasionally.

Perhaps someone else will comment on their opinions?

I have some named attenuators that I can send to you to try, if they work we can come to some arrangement, if not send them back

Gary

[Firebottle]

20dB gain is rather high for a line preamp IMO.
It is unlikely to affect the gain with a valve substitute as the gain level is set via a feedback network.

Personally I would modify the circuit values to lower the gain.

[Slawts]

Just maybe one of those mismatches that appear occasionally.

Perhaps someone else will comment on their opinions?

I have some named attenuators that I can send to you to try, if they work we can come to some arrangement, if not send them back

Gary

Very kind. I will hold off at the moment. I tried swapping valves but the set I have in sound the best. The hiss isn't too bad so I'll live with it a while.

Alan are you sure it is as much as 20db gain? The new ones are adjustable but have 8/14db. You are right 20 does seem high.

[Mike Reed]

Don't know your kit, but f.w.i.w., I suffered far too much gain from my Lector CDP (circa 3.4V). When I had the Naim 552 it didn't bother too much, though compressed CDs sounded awful and vol. range was low (akin to yours). When I moved to E.A.R. valved pre with meters, it REALLY bugged me to see those needles hitting the stops on peaks.

I put a thread on another forum and got lots of advice re. the value of attenuators I required; all, as it transpired, wrong, but diagnosis from afar can be fraught. Science/ mathematics helps, but not, it seems, in this case. A friend lent me a -15 dB and -10 dB. The former showed too much attenuation and I thought it restricted s.q. a bit. The -10dB was better, but still a bit o.t.t.

I then took a punt and bought a Goldenjacks -6dB. Perfect ! No discernible deterioration in s.q. and they kept the needles and vol. control within tolerable range.

Attenuation is attenuation, so I hope the foregoing may have a bearing. Whereas there've been lots of negative comment about s.q. suffering from attenuation, my opinion is now that the less attenuation you have, the less s.q. interference. Logical, I s'pose, with hindsight. Below -10 dB, I think you'd be hard pressed to suffer, but try a low number first; say, -6 or -8dB.

[Slawts]

Hi Mike,

Goldenjacks seems to be no longer operating but I think I will look in to it.

There seems to be quite a debate about whether attentuators spoil the sound or not but I guess the only way to know is try it.

[Slawts]

Just maybe one of those mismatches that appear occasionally.

Perhaps someone else will comment on their opinions?

I have some named attenuators that I can send to you to try, if they work we can come to some arrangement, if not send them back

Gary

Gary is that offer still open and what db level are they?

[Edward]

I have a pair of RCA Goldenjacks and a pair of XLR Rothwells somewhere you can try and return. Each I think at 10db attenuation.

I'd need to find them if you are interested.