JJ KT77's have a pretty bad on-line reputation for premature failures etc. Buy them tested from a reputable dealer, and cross your fingers. The other option are the Genelex reissues, which seem to be well liked.
jeff
Ok thanks for the warning Vinylkid, been noted. I am presently running old Svetlana EL34s, but at Tube Store they say the KT77s will sound much better:
www.thetubestore.com - JJ KT77 Audio Tubes
www.thetubestore.com - JJ KT77 Audio Tubes
Ah ok yes, but the Genelex are double the price of the JJs, twice as good ?
Watford Valves product search :: kt77
Okay, looking to continue to make improvements to my MC-10L. Aside from tube rolling I plan on doing the 12ax7/12at7 mod. I am wondering if installing an ALPS 20K volume potentiometer would be an improvement, has anyone used the ALPS Blue Velvet in this amp? 10K, Blue Velvet - STEREO
I have already replaced the coupling caps with K42Y-2 PIOs (wow, no room for those things at all!). At this point I can't tell a very discernible difference with the new caps. I think I hear some differences now and then but it may be a placebo effect. I guest they have to settle in as well? Up to 200 hours I've read? After that long I'm not sure if I'll remember what the amp used to sound like anyway.
I have already replaced the coupling caps with K42Y-2 PIOs (wow, no room for those things at all!). At this point I can't tell a very discernible difference with the new caps. I think I hear some differences now and then but it may be a placebo effect. I guest they have to settle in as well? Up to 200 hours I've read? After that long I'm not sure if I'll remember what the amp used to sound like anyway.
The Alps is old hat, just fitted the new Tocos which is superb:
http://www.hificollective.co.uk/pdf/cosmos_review_neville.pdf
What is 12ax7 ??
I replaced the caps with ClarityCaps ESA, tremendous difference. If you are not hearing any change even when first firing up then either your caps were duff or too cheap to make any difference
http://www.hificollective.co.uk/pdf/cosmos_review_neville.pdf
What is 12ax7 ??
I replaced the caps with ClarityCaps ESA, tremendous difference. If you are not hearing any change even when first firing up then either your caps were duff or too cheap to make any difference
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Les told me about a fairly simple mod that allows the use of 12ax7s. I'll let Les post it if he wants.
Can you describe the difference your coupling caps made? Are you saying that the more I spend on caps the better the amp will sound? I was under the impression that the Russian K42Y-2s were regarded highly for their sonics.
Can you describe the difference your coupling caps made? Are you saying that the more I spend on caps the better the amp will sound? I was under the impression that the Russian K42Y-2s were regarded highly for their sonics.
Would that be "tremendous difference" in the audiophile sense of the word i.e. "barely perceptible, and then only when I was aware that the caps had been changed"? Significantly audible coupling caps mean that either the caps or the amp design is faulty. One recurring problem is that 'audiophile' caps are often large and therefore have much more stray capacitance, encouraging noise pickup and HF instability. This change in sound can be misinterpreted as an improvement, if the caps were sufficiently expensive.Barbieboy said:
This is my experience as well (as far as coupling caps are concerned). I feel like the sound with the K42s is a bit more harsh/gritty/rough which is why I'm going to try something else. Again, I can't pinpoint a significant difference but perception is reality.
I'm most excited about trying out some 12ax7s!
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12AX7 can only be used with advantage in a circuit specifically designed for them. Elsewhere they will not work too well. That may be why they have a bad reputation among those who don't realise this. Low mu valves are much more forgiving and can be slapped into almost any circuit however badly designed.
If only perception really were reality!
If only perception really were reality!
Interesting, thanks for the insight. Perhaps I'll leave the circuit alone and just try some KT77s or 6ca7s in the amp. Or maybe I should just sit back and enjoy some damn music and spend that money on more music. The thing sounds pretty darn good as it sits...
Getting used to the sound is the most plausible explanation of cap 'burn-in'. Some dielectrics may have minor changes in characteristics but minor changes will not be noticeable in a coupling cap with the correct value. The major change when changing a cap is a small change in value, as most caps are only 10% tolerance, which leads to an even tinier change in frequency response. Our ears can be quite sensitive to small changes in frequency response. Our brains interpret any small change as an improvement, especially if we have paid a lot of money for it or it was recommended by someone we trust.
Good modern caps will propel your amp into another league, resolution will go through the roof. I don't know the caps you have ordered, but I'm getting an etched in the air detailing, lost some of the warmth I must say, but think I can live with that and make amends elsewhere with different cables (scroll back to page 20 onwards for when I fitted the caps)
Only if you apply a gross overvoltage or hook up electrolytics backward. I'm still fixing a hole in my ceiling for the latter (careless soldering moment).
