Klark Teknik KT-2A

[living sounds]

So, buy a unit, swap the TB4 cell, get some nice tubes and ditch the big output cap and I will have a nice La2a ?

Could never DIY one at that pricepoint, case, transformers, knobs, meter, no way.. So these cheap clones may be a blessing after all ?

I've got no real LA2A or high quality clone to compare to, but the modified KT is right up there with the best vari-mu, opto, VCA, FET and diode compressors I own. Even with the upgrades it is as inexpensive as DIY and all the mods can be done in half an hour (that includes cleaning the PCB around the signal path tubes from solder flux).

 

[PermO]

It is good to know it has that potential, and these mods are really easy to perform.

I'm not in the need for a new compressor (too many projects) I see them new for 321,- euro, if I ever happen to run into a cheap 2nd hand I'll defenitely grab it.

 

[vintagelove]

So, in addition to the signal path tube upgrade I replaced the Behringer T4B with a Kenetec classic variant and replaced the yellow poly cap with a Solen Fast.

I've got two compressors, so I was able to compare directly, matching closely via cancellation with inverted signals. Huge difference!

The compression behaviour of the original is very nervous and obvious in a negative way compared to the Kenetec T4B.

The bass is full and authoritative with nicely controlled punchy attacks in the fully modded compressor. And it has the signature smoothly balanced "LA-sound" the LA2A is famous for.

The other one sounds lacks some of the low end punch and distorts very obviously at higher amplitudes and sounds strained in the mids and brittle in the highs.

I had not hoped for this much of an improvement, but this really made all the difference. The fully modded compressor is up there with the best tube compressors now.

And again, do not touch the transformers, they sound great!

Measurements show a little more low end distortion in the unit with the original cap and T4B, but this might not have anything to do with the changes. I'll have a look again after modding the second unit.

Out of curiosity, how many db of gain reduction were you doing to get this kind of difference?

I ask because I bought a pair, and completely stock I found them to be clean, dead quiet, and sound very neutral. They sounded great up until +5 db reduction, even then they sound good, but you can hear them working.

Thanks

 

[living sounds]

Out of curiosity, how many db of gain reduction were you doing to get this kind of difference?

I ask because I bought a pair, and completely stock I found them to be clean, dead quiet, and sound very neutral. They sounded great up until +5 db reduction, even then they sound good, but you can hear them working.

Thanks

Maybe yours has different tubes stock than mine had. I found the stock tubes to be the worst impediment to the sound, regardless of GR, very grainy sounding.

There is at least one video online (linked somewhere in this thread, too, I think) where someone changed just the T4B for a Kenetec. This was the difference I was getting, an obvious overall change in the compression characteristic. Far less obvious and just better behaved, less pumping, more even. On basses and kickdrums with plenty of GR you get more of a solid sub bass attack instead of the sharper midrangy sound. On vocals you get a more focused, effortlessly balanced sound.

Obviously, the less GR you apply the less difference the T4B will make. But the great thing about the original is the fact that you can put plenty of GR on things like vocals and bass and get away with it.

 

[Blue Jinn]

So I just picked one of these up "pre-modded" from a guy on eBay. Kenetek T4B, and new production "Telefunken" tubes, I think just the 12AX7s though. I paid slightly too much for it, but they're currently out of stock everywhere, and, impatience costs money.

Couple of quick questions:

1. I fashioned some cables to use unbalanced, and curious if anyone knows if this is pin 2 or 3 hot? I'm assuming 2 and wired it that way with 2 to tip, 3 to sleeve (RCA) using this scheme: SOS balanced to unbalanced and if that is an OK way to go. (I actually used the XLR not the TRS plug/jack) and

2. whether or not using this in an "amatuer" -10dB world will cause me trouble. I don't see why not, but? The meter has a selection for +10db (?) and +4db.

Also, curious, I always assumed one of the big cost on these was the transformers and the power supply and high voltage components. Are the tubes actually getting a proper, as in high B+? With four tubes, this doesn't seem like the tubes are just a starved plate gimmick to add distortion. But there's also not the prominent warnings about high voltage inside.

 

[living sounds]

So I just picked one of these up "pre-modded" from a guy on eBay. Kenetek T4B, and new production "Telefunken" tubes, I think just the 12AX7s though. I paid slightly too much for it, but they're currently out of stock everywhere, and, impatience costs money.

Couple of quick questions:

1. I fashioned some cables to use unbalanced, and curious if anyone knows if this is pin 2 or 3 hot? I'm assuming 2 and wired it that way with 2 to tip, 3 to sleeve (RCA) using this scheme: SOS balanced to unbalanced and if that is an OK way to go. (I actually used the XLR not the TRS plug/jack) and

2. whether or not using this in an "amatuer" -10dB world will cause me trouble. I don't see why not, but? The meter has a selection for +10db (?) and +4db.

Also, curious, I always assumed one of the big cost on these was the transformers and the power supply and high voltage components. Are the tubes actually getting a proper, as in high B+? With four tubes, this doesn't seem like the tubes are just a starved plate gimmick to add distortion. But there's also not the prominent warnings about high voltage inside.

One of the 12AX7s is in the sidechain, I would not change that one. But the 12BH7 is in the signal path and an upgrade is of benefit, IMO.

Convention is that pin 2 is hot. Your wiring seems fine to me. You could try to also connect pin 1 to sleeve on in / out or both if there is hum or RF interference.

-10dB should be fine, you just need to adjust the gain accordingly.

I should have measure when I had mine open, but all the caps are high voltage parts and there is no point in using those and the elaborate PSU if you are going for starved plate. It certainly does sound like a proper high voltage circuit.

They try to prevent people from opening it by using different torx screws for which the typical consumer probably has no bits lying around. And I think with today's consumers it is assumed that they do not open equipment and start working on it. There is dangerous high voltage in many non-tube devices, too.

 

[MusoGreg70]

One of the 12AX7s is in the sidechain, I would not change that one. But the 12BH7 is in the signal path and an upgrade is of benefit, IMO.

Convention is that pin 2 is hot. Your wiring seems fine to me. You could try to also connect pin 1 to sleeve on in / out or both if there is hum or RF interference.

-10dB should be fine, you just need to adjust the gain accordingly.

I should have measure when I had mine open, but all the caps are high voltage parts and there is no point in using those and the elaborate PSU if you are going for starved plate. It certainly does sound like a proper high voltage circuit.

They try to prevent people from opening it by using different torx screws for which the typical consumer probably has no bits lying around. And I think with today's consumers it is assumed that they do not open equipment and start working on it. There is dangerous high voltage in many non-tube devices, too.

 

[living sounds]

?

 

[fishjaco]

Hey there. Longtime lurker, first time poster here. Just wanted to chime in and express some gratitude to you all for the super helpful information. Thank you! I added a Solen cap and Kenetek opto. I also swapped the Bugera 12ax7 for a newer Mullard which will do until I can hunt down some vintage RCA's. Will probably go grey plate for both the 12ax7 and the 12bh7. So far the unit sounds great. I'm very pleased and grateful to all the contributors in this thread. Happy New Year!

 

[Iamkimosabi]

So does anyone know which potentiometer adjust the "gain reduction" on the pcb?

 

[Rowboat]

I've had one sitting unused in my outboard rack for over a year - abrupt downsizing put me back itb. It's been fascinating to read the many conflicting opinions - almost as interesting as reading of sundry mods/upgrades performed by other members, some of which at least doubled the purchase price of a stock KT-2A!

I do have an opportunity to purchase a pair of Sowter trannies designed for the LA2A.. I'm sorely tempted.

 

[AUDIO FREQ]

So after swapping the opto cell for the kenetek and the tubes for NOS RCA, I noticed differences in the sound but nothing that truly blew me away. I could take it or leave it. But today I swapped the electrolytics for good Nichicon PM and the yellow films for wima.

WOW.

First I sat and listened to old studio takes through it. Then I just started listening to old mono jazz recordings through it. Everything is better.

At first I was amazed that it seemed to now sound exactly the same coming in as it did coming out. Then suddenly I released how fat and hefty the bass was on it post. Then I started getting ASMR. I am not kidding. I've never worked with an LA2A, but if it sounds even better than this then I am speechless.

Get rid of Jamicon's in the signal path! Those yellow polys are probably not great either.

Ryan

I swapped my opto for the Black Lion Audio one. Gonna try some GE 5751. I can't seem to find Nichicon PM series on Mouser/Digikey...maybe they are obsolete now? Idk.

Any other electrolytic suggestions?

Also, instead of WIMA, I think I am going to go with Vishay MKT1822 on the films, and one of these PHC (says its rated for high-end audio) for the FILM output https://www.mouser.com/ProductDetail/647-PHC1405100KN

...since it was available on mouser...couldn't find the Solen on mouser or digikey.

 

[FarisElek]

I swapped my opto for the Black Lion Audio one. Gonna try some GE 5751. I can't seem to find Nichicon PM series on Mouser/Digikey...maybe they are obsolete now? Idk.

Any other electrolytic suggestions?

Also, instead of WIMA, I think I am going to go with Vishay MKT1822 on the films, and one of these PHC (says its rated for high-end audio) for the FILM output https://www.mouser.com/ProductDetail/647-PHC1405100KN

...since it was available on mouser...couldn't find the Solen on mouser or digikey.

Yeah, I may have had a little confirmation bias going on back then. I think a good optocell and MAYBE a really nice 10uf solen output cap will get you where you want to be. Enjoy!

 

[AUDIO FREQ]

Yeah, I may have had a little confirmation bias going on back then. I think a good optocell and MAYBE a really nice 10uf solen output cap will get you where you want to be. Enjoy!

I guess im covered then! Thank you. What about a tube swap? Are these "bulgera" tubes generic? I never heard of these things. But it says "specially selected" on each tube.

 

[FarisElek]

I guess im covered then! Thank you. What about a tube swap? Are these "bulgera" tubes generic? I never heard of these things. But it says "specially selected" on each tube.

Thr 12ax7 at V1 might have some effect on the sound, but likely the circuits negative feedback will make most tubes sound the same. No hurt in playing around though. The EH 12ax7 are a good new production tube. For the most part I'm done paying insane prices for a negligible change. Just go make some music.

 

[Whoops]

I can see that some of you guys are changing the T4 cell in the KT-2A.

Kenetek T4 was mentioned, what are the best choices for T4 cells at the moment?
Which ones do you guys prefer?

 

[FarisElek]

I can see that some of you guys are changing the T4 cell in the KT-2A.

Kenetek T4 was mentioned, what are the best choices for T4 cells at the moment?
Which ones do you guys prefer?

The Kenetek made a big impact on my unit. The original compressed just fine but something about the Kenetek made the sound feel closer to what I'm used to hearing from the original LA2As. He offers a lot of information on his website about the technical aspects that I don't quite understand, but he charges the same price as his competitors and seems very knowledgeable on the subject. Good enough for me.

 

[living sounds]

I modded a few of these. My take on the do's and dont's:

A better opto cell makes a huge difference. I tried the Kenetek classic one, which sounds as advertised. Highly recommended. I also have an IGS opto cell in one of my units, which sounds very nice, too, I think it does flatten the signal a bit more, so I tend to use this unit for vocals rather than bass.

Better tubes get rid of the grizzly high end of the original ones. No need to replace the ones not in the signal path though.

And better signal path caps (there are 3, I used Solen Fast and / or Wima MKP) made a surprisingly big difference. These are all film caps (no electrolytics in the signal path). The big yellow 10uf on the output was the worst, but the smaller ones also took away some of the snappyness/clarity/energy.


There is no need to change the transformers, these sound really good. And there are no electrolytics in the signal path, so I wouldn't bother.

 

[Iamkimosabi]

I modded a few of these. My take on the do's and dont's:

A better opto cell makes a huge difference. I tried the Kenetek classic one, which sounds as advertised. Highly recommended. I also have an IGS opto cell in one of my units, which sounds very nice, too, I think it does flatten the signal a bit more, so I tend to use this unit for vocals rather than bass.

Better tubes get rid of the grizzly high end of the original ones. No need to replace the ones not in the signal path though.

And better signal path caps (there are 3, I used Solen Fast and / or Wima MKP) made a surprisingly big difference. These are all film caps (no electrolytics in the signal path). The big yellow 10uf on the output was the worst, but the smaller ones also took away some of the snappyness/clarity/energy.


There is no need to change the transformers, these sound really good. And there are no electrolytics in the signal path, so I wouldn't bother.

Do you mean these yellow ones?

 

[living sounds]

Do you mean these yellow ones?

The red one at the bottom (22nf) and the two yellow ones above it (100 nf) are directly in the signal path. The two yellow ones next to your thumb are in the sidechain, no point in changing these IMO.