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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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Post by lovebuzzz on Aug 17, 2024 3:45:03 GMT -6
Would it be possible to see this picture in higher resolution maybe? I want to tear my 2a-KT and modify it, so I'd like to see what could be done, by more experienced people than me.. |
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Post by doubledog on Aug 17, 2024 13:14:33 GMT -6
Would it be possible to see this picture in higher resolution maybe? I want to tear my 2a-KT and modify it, so I'd like to see what could be done, by more experienced people than me.. any mods you do are not going to make it an LA-2A. You could change all the caps and resistors, transformers, tubes, and spend a lot of money but is it worth it? I changed the opto module to a Kenetek ($100) and swapped a couple tubes (~$50), and changed the output cap ($5... I did not have to disassemble it to do any of this - just took off the lid) and I'm pretty happy with it (for what it is). It is an improvement from the stock sound and sounds different than my other 2A clone (Lindell LiN2A) and maybe someday I'll move up to an Audioscape or Stam (but probably never a real LA-2A - certainly not at their current silly prices)... |
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ericn
Temp
Balance Engineer
Posts: 16,083 
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Post by ericn on Aug 17, 2024 17:41:45 GMT -6
In a LA-2 the most obvious starting points opto, tubes and transformers.
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Post by ironinthepath on Aug 19, 2024 19:04:43 GMT -6
I think obtaining or reverse engineering a schematic would present the clearest set of options and give some hint about whether any particular mod might be useful or not. I agree that tubes, transformers, and opto the most likely to impact your perception of the unit. If I recall correctly, kenetek offers a drop in custom T4b cell for Klark Technic - that would be the easiest route to try, in my opinion, before doing too much else
Update: nevermind, see doubledog’s post above, I think he’s saying the same thing.
Also, the Buzz Audio Essence is a super nice opto that you might find preferable, good prices used
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Post by doubledog on Aug 20, 2024 7:01:43 GMT -6
Yes, the Kenetek opto was an easy change (like swapping a tube in a socket) and also made the biggest difference in sound. The tube swapping and cap change were much more subtle differences. Swapping transformers and all other caps and resistors would be a much more time consuming effort (and in my opinion, not worth the time/effort for the outcome). At that point, just buy a better compressor.
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