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TUBE NOOB: ADVICE NEEDED ON REPLACEMENT TUBE

Recently my old man has given me his phono section. It is a Soundtech Preamp one, and no I am not expecting that anyone will know what this is. It is a tubed, pure class A, dual mono phono section with what looks like 2 independent power supplies, internal (strange). The unit is awesome, I think the retail cost was about $1800 in the 80s/early 90s, which does make it a little pricey for the time, but putting all price/performance issues aside I will say it is an amazing phono section. Now my concern is that I know very little about tube equipment and I am seeking some advice on finding a replacement tube for this piece. The tubes are quite old and I think I can achieve improvement sonically by replacing the old tubes.

The guide indicates that the amp uses 2 6CL8A tubes, a very unusual tube that I know nothing about despite my best research efforts.

Now, I don't know what to do. I have found some old tubes on ebay, but how do I know they will not be junk ? Maybe the unit can be modified to take a common tube? Is there maybe a way for me to find a tube equivalent, hopefuly with something that is still manufactured and intended for hifi audio use?

I am at a bit of a loss, so please give me some suggestions. I will post the schematics and guide manuals when I receive the electronic copy via email from the company. Also if anyone has used this amp, I am interested in chatting with you. Thanks guys.
dfelkai
9 responses Add your response
samhar
1,048 posts
 
www.audioasylum.com/audio/tubes/bbs.html

Ask your questions there!
Good luck.
lewm
13,010 posts
 
Check with Antique Electronic Supply in Arizona. They are very reliable nice people who will not sell bad tubes, and they have a huge inventory.
roxy54's avatar
roxy54
7,974 posts
 
I would also recommend Vintage Tube Services.
swampwalker's avatar
swampwalker
5,138 posts
 
Also try A'gon member/tube seller Jsautter.
samhar
1,048 posts
 
HI my advice to ask your questions on Tube Asylum was because there are tubeophiles there with all kinds of obscure information. You might also contact Jim McShane (tube dealer) he's very knowledgeable.
racamuti's avatar
racamuti
362 posts
 
Hi, Tube World has NOS 6CL8A for $4.50 each. They are a half wave rectifier tube. Good Luck
dfelkai OP
89 posts
 
Does anyone think it is possible to tweak the gear to handle something more common like a 12ax7? Would those tubes offer better performance then these obscure 6cl8a tubes?
w8aaz
43 posts
 
No I don't see any advantage to switching to 12AX7 tubes if the design was well thought out at the time and designed around those particular tubes. They must have had some purpose to go with a less well known tube that might be worth research. But in any case, I don't know why you assume your tubes need replacement. Power output tubes need replacement much more often than low level preamp tubes. Some tubes have a lifespan of 100,000 hours or more claimed by the manufacturers. I would test them and see if there is any problem like reduction in emission or something. Maybe get a spare set and try the spares to see if there is any audible improvement in performance. If not set them aside and keep them for someday. I would think a very old tube preamp might benefit from component upgrades as much as new tubes, but from the vintage you mention, I can't see that maybe being an issue. If you have the techical data, perhaps a shop could test the thing to see if all the voltages etc. are still correct or if anything has deteriorated. A failing tube might reveal itself in lower gain in one channel, or hum or distortion but I would not rush to "improve" something that is fine as is. Check the specs on the thing. Some tube preamps like to work into much higher impedances than solid state gear provides and a mismatch might make for dull sound.
dfelkai OP
89 posts
 
UPDATE: Got a wack of NOS tubes and I am happier then ever, after little consideration I agree that changing the design in this case would have been a lost cause and probably would have not yielded better results. The design includes a very unique tube and circuit and sounds AMAZING why tinker with something that has surprised only to the upside!
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