Valves/tubes

[GlynMo]

Hi, anyone on here know about valves/tubes? I understand that many valves used in hi-fi can be substituted with better equivalents to produce improved sound quality, and as both my amp and cd player need new valves, it seems like the best time to investigate. (ok, the best time would have been before I needed replacements, but...).

The amp is a Pathos Logos and the cd player a Shanling SCD -T200. Anyone?

[P700DEE]

Plenty of suppliers and several different manufacturers around the world. Better ?? Sometimes subjective, different suppliers valves sound different but are they actually better ? In general terms UK/USA made considered best (especially original period made ones), then Russian then Chinese. Can be huge differences in prices too ! Then some valves do the same job but are different, e.g. 6922 and I think ECC83, they can sound different and which sounds best can depend on the kit you fit it in. Either do your research on the hi-fi forums for the best valves for your kit or find out the make of the ones you have fitted already and get the cheapest supplier of the same ones. The good news is that new valves usually sound better than old valves

[OldSkoolRS]

Also you should take into account that when replacing valves (especially if changing the type/model) that the bias may need adjusting to suit. If this is something you can do for yourself, then fair enough, but otherwise you may cause the amp to run hotter or perhaps be more prone to clipping if incorrectly adjusted.

FWIW 15 years ago I built a 'rip off' copy of a Marshall guitar pre amp(master volume model) and I had a number of valves to try. However tweaking the circuits themselves made far more difference to the sound than changing the valves(though to be fair part of the Marshall sound is the 'overdrive' so it was intentional distortion I was focusing on).

[telecat]

As you probably have gathered there are plenty of views on this. Firstly if you want to replace the valves make sure you take note of which valves fit where. Putting a E88cc in the position of a ECC83 can cause an expensive fault! Secondly Some "old" valves made in the USA, Europe and the UK are very good and if you can get them as "New Old Stock" or "Never used", they will last a while. There are also some makers who are now producing "new" valves to very high standards. You will have to check very carefully to make sure you are getting the right ones however. The Makers from China and Russia that produced some very "dodgy" valves are those that gave "New" valves a bad name are also amongst those that produce some good ones so make sure you know which you are buying.

Most Modern Valve amps are either self biasing or have a Bias meter included to allow you to get the valves "just right". As said some valves also have several names for example the British EL34 for example has the American designation 6CA7. The EL34L is also slightly different but can substitute for the EL34 in most amplifiers. Their is also a 6CA7 "Fat Boy" which has a more bulbous glass housing. Just take care to get the Tubes you need and fit them carefully. I have a Audio Innovations S500 which uses two ECC88's three ECC83's and 4 EL34's all of which are Mullard's and all of which now cost a small fortune! Still that's not as bad as original GEC KT88's. Nobody will quote prices on the net anymore they are that expensive.

[Peter Empson]

There's no bias adjustments on the items you have (this is only necessary on some valve power amp stages, and not a hybrid like the OPs). So just try a variety of identical numbered (or known equivalents) valves and see what you think - I'd expect you should find there's quite a big difference in the sound between different makes/ages etc.

[GT2CS]

Peter Empson said:

There's no bias adjustments on the items you have (this is only necessary on some valve power amp stages, and not a hybrid like the OPs). So just try a variety of identical numbered (or known equivalents) valves and see what you think - I'd expect you should find there's quite a big difference in the sound between different makes/ages etc.

you will need a matched pair of 6922 valve equivalents. to get a matched pair you will need to adjust the biasing.

http://www.vinylengine.com/turntable_forum/viewtop...

[Peter Empson]

GT2CS said:

you will need a matched pair of 6922 valve equivalents. to get a matched pair you will need to adjust the biasing.

http://www.vinylengine.com/turntable_forum/viewtop...

Whilst a matched set is never a bad thing I can see no reason why you'd 'need' them for this application. Unless I'm reading the wrong bit in the link, it is about a Graaf OTL with DC coupling - a very different design to the one discussed here (which will not be DC coupled, and there will be no adjustment for biasing except in the solid state output stage, which we're not impacting).

Btw, forgot to mention in the original post that whilst I've not used that model of the Shanling, IIRC two of the valves are just for the headphone output (they were on the older 100), so the OP doesn't need to replace all 4 if he wants to change just the main audio output.

[GlynMo]

Thanks for all of the suggestions. I don't want to invest in a number of different valve makes/types purely for comparison purposes so I'll haunt some of the hifi forums to see if there is an acknowledged 'better' version of the valves I need. I realise that 'better' is very subjective, and if there doesn't appear to be a valve that stands out, I'll just buy identical replacements. Any suggestions for a good online source?

ETA: yes, 2 of the tubes on the Shanling are for the headphone output. I might not replace the audio output valves either as I find that, on most music, valve output into the Pathos valve preamp is a bit too soft so I tend to use the ss output.

Edited by GlynMo on Tuesday 5th March 09:58

[Peter Empson]

I can recommend www.watfordvalves.com and www.tube-shop.com who often have some suitable NOS valves at good prices in the UK. I would recommend trying some different valves in the Shanling, it might solve the issue you have with that output.

[GlynMo]

Thanks Peter, I'll give them a try.

[telecat]

I tend to use www.edicron.com. No prices are listed but they are competitive.