[AudioPhewl]

Have tried asking in the Stax thread, but haven't had any responses to date.

I'm a tube newbie. I picked up my Stax rig just over a week ago, and would like to experiment with different tubes. It uses the 6CG7/6FQ7 type of tubes.

My queries(I'll try and keep this brief!):-

1. I'm in the UK. Does anyone know anywhere good to buy the tubes from?
2. What tubes should I be looking for to replace the stock Electro-Harmonics? Is there a general consensus as to what works "best"?
3. Does such a resource exist - is there anywhere detailing the different tubes available, along with their audio characteristics?

Cheers in advance

.

~Phewl.

 

[dsavitsk]

Quote:

Originally Posted by AudioPhewl /img/forum/go_quote.gif 2. What tubes should I be looking for to replace the stock Electro-Harmonics? Is there a general consensus as to what works "best"?

Look for 6CG7/6FQ7's. This is basically a 6sn7 with different pins. The 12au7 is also about the same, though it's a higher distortion tube, but its heater is different -- don't try it. There are a few others that might work, but without seeing the schematic and/or construction, it is hard to know. If pin 9 is unconnected, the 6au7 or 7au7 will probably be fine.

Quote:

Originally Posted by AudioPhewl /img/forum/go_quote.gif 3. Does such a resource exist - is there anywhere detailing the different tubes available, along with their audio characteristics?

No. Generally the circuit and other associated parts make more of a difference than the particular brand of tubes. You will tend to see tube rolling as a bigger pastime among people who are unable to design circuits.

 

[AudioPhewl]

Cheers, dsavitsk. So there isn't a particular brand or model of tube that is better than the others, so long as it's a 6CG7/6FQ7?

Does that mean I may as well stick with the standard ones?

~Phewl.

 

[dsavitsk]

Quote:

Originally Posted by AudioPhewl /img/forum/go_quote.gif Cheers, dsavitsk. So there isn't a particular brand or model of tube that is better than the others, so long as it's a 6CG7/6FQ7? Does that mean I may as well stick with the standard ones?

I am sure you can find some hyperbole on the net about how the current production tubes are unacceptable, and such and such NOS variety will result in angels dancing in your ears. My guess, and it is only a guess as I have not used this particular tube, is that the current production versions are decent, and that if you can find some NOS varieties that they may offer a marginal improvement. Looking around, it looks like these run from $10 to $25 each from most reputable tube dealers, with plenty of US made versions available for south of $15.

Antique Electronic Supply
Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!
Radio Daze

So, worth experimenting with, but I wouldn't get sucked in to somebody selling them as expensive magic tubes. ($40 isn't terrible, but you can surely make a bigger improvement for less money by swapping out a few caps.)

 

[AudioPhewl]

Thanks, I guess I'll stick with what Stax provided me with unless someone else chirps in with something logical

.

Thanks again,

~Phewl.

 

[AudioPhewl]

Anyone else have anything to add on the subject?

~Phewl.

 

[mwofsi]

Quote:

1. I'm in the UK. Does anyone know anywhere good to buy the tubes from?

I've only bought 9 or so tubes, for my SOHA, for tube rolling....
ebay worked well, both from home and abroad and was quite painless.
In the SOHA at least, there are small but noticeable differences with different tubes, and I did prefer the nos over the new production. The GE5963's that others preferred are also my favourite. (12au7 alike so probably no good to you)
The SOHA tho' is said to be most affected by the tube installed above all else.

You know you want to, at least try a different tube or two! If the cheap tube you get is worse than those you've got already, at least you'll know that it made a difference!

 

[AudioPhewl]

^That's the thing. They sell units modified with different valves(commonly referred to by dealers as the Kimik modification), so I'd imagine there'd be an audible difference between tubes. But the first chap to respond said their wouldn't be, and I don't really want to just buy them for the sake of it if there isn't going to be any difference...

~Phewl.

 

[mwofsi]

I don't know dsavitsk personally, but from many posts I have read here and on HeadWize he is clearly very knowledgeable, especially about tubes.

If you read his posts carefully he doesn't say there'd be no difference, only that
it might be small or subtle. My very brief experience agrees with that. He also points out that you'll probably get better value for money using better capacitors.
He's well regarded in this field too, doing extensive comparisons of substitutes.

All I'm saying is that the differences in tubes (generally, not in this setup which I haven't heard), though small, are and can be pleasing. It's part of the tube experience to tube roll. If you wish to upgrade caps it tends to involve a bit more diy. There are plenty here who can help and guide with advice.

Of course if your happy with the sound at the moment, well enjoy the music!

Mike

Edit: If you don't know already nos is not a brand but means New Old Stock, tubes that were made some time ago but haven't been used in anger..

Edit: Quote:

Originally Posted by Cambridge Audio - Stax SRS4040 II Kimik Kimik modiication fits selected NOS 6FQ7 tubes, which are cyrogenically frozen, fited with EAT dampers and have pins 24 Carat gold plated

price £200.

 

[mwofsi]

With nothing better to do I've looked up the Kikmik mod which led to this:
http://www.audio.grobel.com.pl/files...07_SRM-007.pdf
and this:
http://www.head-fi.org/forums/f5/sta...review-267767/
This may not be the same energizer but anyway:
Quote:

For the Kimik modifications, the Philips valves are specially selected, low-tolerance tubes from old (unused) stocks. Their pins are gold plated and the valves are cryogenically treated, a process that takes up to four weeks. They are then fitted with EAT tube dampers, which consist of machined aluminium heatsinks damped by rubber gaskets. The main change, however, is to the set-up of the amplifier, which is minutely adjusted to minimise distortion. This is said to make a big difference and takes several days to complete.

Quote:

Because the changes were specified and engineered by Kimik, a company owned by one Mick North, the resident engineer for Stax in the UK, it has become known as the Kimik modified version.

I wonder what it is that they adjust?

 

[AudioPhewl]

I'm curious what else they do for that much money... wish someone had done a DIY guide

.

~Phewl.

 

[spritzer]

Quote:

Originally Posted by mwofsi /img/forum/go_quote.gif I wonder what it is that they adjust?

The bias of the tubes is the only thing to be adjusted and anybody with a voltmeter can do that. The Phillips tubes aren't even very good so stick with the made in Japan stuff, vintage Toshiba's if you can find them.

 

[AudioPhewl]

Would you have a pinout so I can measure the stock bias?

http://www.head-fi.org/forums/f5/bia...srm-t1-324155/

That thread details it all nicely, but the images are missing

.

~Phewl.

 

[spritzer]

Here you go:

 

[AudioPhewl]

Thanks a lot!

Is that looking into the socket from the front, or is that the plug itselt?

~Phewl.