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Post by doubledog on Dec 16, 2023 15:44:36 GMT -6
anyone else mod their KT-2A or 2A-KT (mine is the latter).
I initially swapped the original opto for a Kenetek. I think it sounds/compresses smoother but honestly not night and day difference.
Then I replaced the output cap (the big yellow 10uF film cap) with a JB JFX (10uF 250V - you can find them at Newark and it fits nicely). I was expecting maybe stronger low end but on my test sources so far I'm again not hearing a lot of difference. My test sources are a bass guitar, kick, snare, sax, and a couple different vocal tracks.
next up is tube swapping. So far I swapped V2 (which is the first 12ax7 - I believe V3 is in the detector circuit since when I pulled it I still got audio--and no compression) . I installed a new/re-issue Mullard 12AX7 and it sounds good, but maybe a little darker than the stock Bugera tube. I feel like it lost a bit of top end sparkle, and I already felt the KT is a bit darker than the Lin2A that I also have. So I might try a JJ ECC83 in there to see.
anyone else swap tubes? what did you use?
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Post by audiospecific on Dec 16, 2023 18:01:12 GMT -6
anyone else mod their KT-2A or 2A-KT (mine is the latter). I initially swapped the original opto for a Kenetek. I think it sounds/compresses smoother but honestly not night and day difference. Then I replaced the output cap (the big yellow 10uF film cap) with a JB JFX (10uF 250V - you can find them at Newark and it fits nicely). I was expecting maybe stronger low end but on my test sources so far I'm again not hearing a lot of difference. My test sources are a bass guitar, kick, snare, sax, and a couple different vocal tracks. next up is tube swapping. So far I swapped V2 (which is the first 12ax7 - I believe V3 is in the detector circuit since when I pulled it I still got audio--and no compression) . I installed a new/re-issue Mullard 12AX7 and it sounds good, but maybe a little darker than the stock Bugera tube. I fell like it lost a bit of top end sparkle, and I already felt the KT is a bit darker than the Lin2A that I also have. So I might try a JJ ECC83 in there to see. anyone else swap tubes? what did you use?
I was helping someone I knew in Japan modding his, but he passed away in the middle of it during our dark times these few years.
Its was a lot of cap and resistor changes.
I don't mind if we start a thread over it. I can't justify buying one and it would be an insult to my long passed away engineering friend.
That does remind me that I should use those per-production optos.
I think I have everything I need to build one up except a nice case to put it in.
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Post by doubledog on Dec 16, 2023 21:30:39 GMT -6
I've got a 12BH7A on the way, but honestly I'm not really sure what I'm looking for there - so I bought a vintage/used tube just to see what it sounded like and if it made any difference.
btw, the opto is labeled as V1, then V2 is in the audio path and V3 is in the compression detector/sidechain circuit. I think V4 is the 12BH7A (also a stock Bugera - aka Behringer- branded tube but they obviously don't make the tube - guessing it is a low cost Chinese tube). V5 is an EL84 (not in direct the audio path). The 12BH7A I have on the way is a GE (gray plate, halo getter). if it sounds crappy then I'll be looking for something else - maybe an EH? Or maybe I keep it as is...
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Post by audiospecific on Dec 16, 2023 22:04:32 GMT -6
I've got a 12BH7A on the way, but honestly I'm not really sure what I'm looking for there - so I bought a vintage/used tube just to see what it sounded like and if it made any difference. btw, the opto is labeled as V1, then V2 is in the audio path and V3 is in the compression detector/sidechain circuit. I think V4 is the 12BH7A (also a stock Bugera - aka Behringer- branded tube but they obviously don't make the tube - guessing it is a low cost Chinese tube). V5 is an EL84 (not in direct the audio path). The 12BH7A I have on the way is a GE (gray plate, halo getter). if it sounds crappy then I'll be looking for something else - maybe an EH? Or maybe I keep it as is... You'll be fine with GE12BH7. But the tube roll isn't going to fix. The Bulgera tubes are rebranded tubes from JJ Tesla.
Cap and resistor changes are the real changes. Because they used basically the cheapest parts that would work in circuit, and it shows. Here is a pic of an incomplete mod, even though the guy use some parts I wouldn't use in that unit because I would use ones that would fit in better, and he didn't ask me directly on the forum. Just what parts I would use to build one.
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