Klark Teknik KT-2A

[JohnX]

As for capacitor value, is the one in question sitting in the audio path? If so, it's likely to be about frequency response.

The consistent description that I keep finding in this thread is to replace “the big yellow capacitor” (thread #28, 55, 59, 117) - on my PCB, the biggest yellow capacitor is C8 and is the one that I have circled in the previous screenshot.
I am trying to confirm whether that is actually the correct capacitor to replace and if the value specified (10uf/250v also from this thread #95) in my previous comment is the correct value to replace it with. Or should I find an exact replacement for how it is actually labeled on the PCB(104J400)?

 

[kags]

The consistent description that I keep finding in this thread is to replace “the big yellow capacitor” (thread #28, 55, 59, 117) - on my PCB, the biggest yellow capacitor is C8 and is the one that I have circled in the previous screenshot.
I am trying to confirm whether that is actually the correct capacitor to replace and if the value specified (10uf/250v also from this thread #95) in my previous comment is the correct value to replace it with. Or should I find an exact replacement for how it is actually labeled on the PCB(104J400)?

Check out post #30….

 

[JohnX]

Check out post #30….

DOH!!!
I have read that paragraph so many times and I don’t think I ever noticed the words “It's mounted on the vertical PCB” until today.
This explains why the big yellow one I had selected didn’t seem particularly big. I believe that I have located it correctly now in the attached photo.
thanks

 

[thelivingroom]

I’m preparing to do some of the suggested mods to my 2A-KT.
1 - Replace Opto attenuator - Kenetec T4B on the way. Arrives Saturday.
2 - Replace 1 12AX7 at V2 (farthest left): I have a JJ E83CC to try for now.
3 - Replace EL84: also have a JJEL84
4 - Replace 12BH7: have a NOS Sylvania we bought for a guitar amp but never used.

I may swap out these tubes for some older NOS at some point, but I think these should still be an upgrade.

Those all seem fairly simple, but I’ve got a few questions about this:
5 - Replace what is traditionally described in this thread as the “big yellow capacitor” C8? (thread #28, 55, 59, 117) I have circled what I am assuming to be the correct one in one of the photos. It is labeled on top 104J400 - the only reason I’m not sure whether the one I have circled is correct is because the value that I read in this thread to replace it with appears to be slightly different: 10uf/250v (thread #95)
Have I circled the correct capacitor to replace?
Should I replace with higher quality 10uf/250v OR did I miss the correct value in this thread?


Before I can remove and replace that capacitor, I will have to remove the PCB. I have noticed that there is a yellowish adhesive on a few of the connectors that are attached to the PCB. I have attached some screenshots. Is there any special handling that I should be utilizing when “breaking that seal”?

​

Solen 10uF 250v fits perfectly as a replacement for “big yellow”. I did the mods for a friend of mine last year (except for the EL84 - that didn’t seem necessary), and I also changed the red capacitor below that Midas trans to a Sprague 716P .022uF 600v “orange drop” and the two yellow “104J250” to the right of it to Solen .1uF 630v. I thought the unit sounded like harsh trash when I listened to it before starting the mods, compared to the real deal and my DIY versions, but was very useable after the changes. You should be much happier with it after.

 

[JohnX]

I finally got around to trying out some mods on a brand new 2A-KT.
Everything I tried came from this thread:

1 - replaced opto attenuator with Kenetec T4B
2 - replaced V2 (the first Bugera12AX7A) with new JJ E83CC (not ECC83)
3 - replaced Bugera EL84 with new JJ EL84
4 - replaced Bugera 12BH7A with NOS Sylvania 12BH7A
5 - replaced big yellow cap with Solen 10uF 250V - (the legs of the Solen were too wide for the PCB so I had to make some small jumpers)

I swapped the tubes one at a time & noticed that the E83CC & 12BH7A seemed to have the most noticeable differences before & after. At some point, I may try some NOS tubes for the 12AX7 & EL84, but the new JJ's will have to do for now.

We have a stock UA LA2A from 2011 here at the studio I work at. Even though I don't expect to duplicate that device, I thought it would make for a solid baseline for comparison.
I am attaching a link to 3 WAV files. I tried uploading them to this post, but nothing worked. One is the stock LA2A, one is the stock 2A-KT & one is the modded 2A-KT. I suspect that you will pick out the LA2A easily.
I tried to match the gain as closely as possible.
Before I identify the files, I thought it might be fun to do some blind comparisons - curious to hear your thoughts.

Link to files: https://www.dropbox.com/scl/fo/t73h...nMlwDMGM?rlkey=zvnheo12dlel8kmz3dhoco8nh&dl=0

 

[scott2000]

Before I identify the files, I thought it might be fun to do some blind comparisons - curious to hear your thoughts.

Files aren't downloading here ....
gives some strange xml file dialog...

 

[JohnX]

Files aren't downloading here ....
gives some strange xml file dialog...

I tried uploading a few more times & in other formats. Same XML issue every time.
Ended up replacing the uploads with a Dropbox link.
https://www.dropbox.com/scl/fo/t73h...nMlwDMGM?rlkey=zvnheo12dlel8kmz3dhoco8nh&dl=0

 

[scott2000]

impressive....
I like C
B has more weight but similar to A..idk...
Where's the plug in version?lol
Never heard a real or clone LA2A

 

[living sounds]

A has the best definition, B sounds really mushy. My guess would be A is the UA original, B unmodified, C modified.

 

[rock soderstrom]

I am attaching a link to 3 WAV files. I tried uploading them to this post, but nothing worked. One is the stock LA2A, one is the stock 2A-KT & one is the modded 2A-KT. I suspect that you will pick out the LA2A easily.
I tried to match the gain as closely as possible.
Before I identify the files, I thought it might be fun to do some blind comparisons - curious to hear your thoughts.

There are differences, but they are smaller than I expected. In this example, it's really difficult for me to name a clear favorite. Maybe C, because it's the most balanced? B is not bad either, a bit fuller. But I have to say that I listen to it on mobile headphones, not on monitors.

My guess would be:

A. 2A-KT original
B. UA LA2A
C: 2A-KT modified

PS: I recently bought a 2A-KT for little money, I'm already very happy with it stock, I'll do some of the mods next week too, let's see what that changes.

Last week a 2A-KT was sold here for 180€! Unfortunately I was too slow, I could really use a second one of these...

 

[JohnX]

so happy that a few of you chimed in about this. after spending a couple of hours on it, I felt like I was beginning to lose perspective.
I have to admit that the differences were more subtle than I had been expecting. I think the most significant positive change definitely came from adding the T4B B Oto attenuator & replacing the big yellow capacitor. I was not liking the attack or release speed of the stock opto attenuator at all. I noticed the least change from swapping out the EL 84. Maybe I would have better results with some NOS tubes, but I’m probably going to leave it here for now.
I actually like the way the device is sounding, but I may proceed with a few more capacitor replacements as had been described in earlier parts of this thread.

Here are the identifiers:
BASS A = fully modded
BASS B = LA2A (Universal Audio 2011 stock)
BASS C = STOCK 2A-KT

 

[timtom]

There are differences, but they are smaller than I expected. In this example, it's really difficult for me to name a clear favorite. Maybe C, because it's the most balanced? B is not bad either, a bit fuller. But I have to say that I listen to it on mobile headphones, not on monitors.

My guess would be:

A. 2A-KT original
B. UA LA2A
C: 2A-KT modified

PS: I recently bought a 2A-KT for little money, I'm already very happy with it stock, I'll do some of the mods next week too, let's see what that changes.

Last week a 2A-KT was sold here for 180€! Unfortunately I was too slow, I could really use a second one of these...

I got this one for 180€, trip to the lake and came back with the 2a-kt....
will also do the capacitor mods and I already have a IGS opto cell to switch.

Thanks for the files!

 

[JohnX]

I got this one for 180€, trip to the lake and came back with the 2a-kt....
will also do the capacitor mods.

Thanks for the files!

That’s a great price. Mine was decent at $300 US but you slayed it.

 

[living sounds]

so happy that a few of you chimed in about this. after spending a couple of hours on it, I felt like I was beginning to lose perspective.
I have to admit that the differences were more subtle than I had been expecting. I think the most significant positive change definitely came from adding the T4B B Oto attenuator & replacing the big yellow capacitor. I was not liking the attack or release speed of the stock opto attenuator at all. I noticed the least change from swapping out the EL 84. Maybe I would have better results with some NOS tubes, but I’m probably going to leave it here for now.
I actually like the way the device is sounding, but I may proceed with a few more capacitor replacements as had been described in earlier parts of this thread.

Here are the identifiers:
BASS A = fully modded
BASS B = LA2A (Universal Audio 2011 stock)
BASS C = STOCK 2A-KT

Interesting, thanks! Listening to this some more, also on different systems, I now do think that the Universal Audio original sounds actually clearer dynamically, with better bass... Audio is funny...

The Elephant in the room is the power supply, which injects HF garbage into the signal path. I plan to adress this with a mod.

Also, the trafos and gain staging might not be so great after all. There's a rundown of the Behringer KT Pultec "clone" at realgearonline.com that shows them cutting corners (changing the gain structure in order to use weaker/cheaper trafos). Something similar might be the case wrt to their LA-2A clone as well.

 

[JohnX]

gain staging might not be so great after all. There's a rundown of the Behringer KT Pultec "clone" at realgearonline.com that shows them cutting corners (changing the gain structure in order to use weaker/cheaper trafos). Something similar might be the case wrt to their LA-2A clone as well.

I certainly noticed that the gain structure was quite different than our stock LA2A.
I had to crank the gain knob much higher as well as the peak reduction knob to match; so they did not spend much focus in creating similar gain structure.

That being said, I’m still pretty happy with my $500 compressor.

I’ve done some blind tests here in the studio with clients and honestly, nobody was able to discern a justifiable difference (between price points) and if they could hear a difference, they guessed it wrong every time.

 

[rock soderstrom]

so happy that a few of you chimed in about this. after spending a couple of hours on it, I felt like I was beginning to lose perspective.

Thanks for doing this comparison!

I have to admit that the differences were more subtle than I had been expecting.

+1

I think the most significant positive change definitely came from adding the T4B B Oto attenuator & replacing the big yellow capacitor. I was not liking the attack or release speed of the stock opto attenuator at all.

That was one of the reasons why I bought the 2A-KT, I want to experiment with DIY T4b cells. I've had the needed components lying around for years, I'm curious to see what the differences are.

I noticed the least change from swapping out the EL 84.

That doesn't surprise me, because in the end the EL84 (or the original 6AQ5/EL90) only drives the fluorescent panel and therefore has no direct influence on the signal chain. The fluorescent panel will cancel out any differences in the tube before it, I think.

I got this one for 180€, trip to the lake and came back with the 2a-kt....
will also do the capacitor mods and I already have a IGS opto cell to switch.

Lucky you, congratulations! 180 was the best price at kleinanzeigen for a long time. I paid 220€.

I already have a IGS opto cell to switch.

I can't wait to see what you think of this change!

The Elephant in the room is the power supply, which injects HF garbage into the signal path. I plan to adress this with a mod.

Is it proven or an assumption? I've just finished a project with a switching power supply and it's relatively easy to combat the artifacts. I'll take a closer look when I'm back home.

Also, the trafos and gain staging might not be so great after all. There's a rundown of the Behringer KT Pultec "clone" at realgearonline.com that shows them cutting corners (changing the gain structure in order to use weaker/cheaper trafos). Something similar might be the case wrt to their LA-2A clone as well.

I'm not sure whether all the findings about the Pultec Clone can be transferred to the 2A-KT. For me, this is the weakest device in the Klark Teknik Clone series. The Opto Compressor has a nice sound signature to my ears even without compression (the transformers can't be that bad), but I can't say anything about gain staging yet.

I certainly noticed that the gain structure was quite different than our stock LA2A.
I had to crank the gain knob much higher as well as the peak reduction knob to match; so they did not spend much focus in creating similar gain structure.

Ok, I see. I've also heard some people say that the original would have "too much gain" if they integrated it into a digital setup. But I have no experience with that...

That being said, I’m still pretty happy with my $500 compressor.

In the 90s, we would have sold our mothers for a device like this.

I’ve done some blind tests here in the studio with clients and honestly, nobody was able to discern a justifiable difference (between price points) and if they could hear a difference, they guessed it wrong every time.

 

[living sounds]

Is it proven or an assumption? I've just finished a project with a switching power supply and it's relatively easy to combat the artifacts. I'll take a closer look when I'm back home.

Yes, I've looked at it with a scope. Fortunately, there's sufficient space in there to put in a simple unregulated linear supply as in the original.

Lucky you, congratulations! 180 was the best price at kleinanzeigen for a long time. I paid 220€.

I got my third one used (but good as new) for 80 EUR, the seller thought it was defective but it was actually OK.

Three of these are overkill, especially since I've come to prefer other compressors on vocals and bass in recent months. But maybe this would change again with another upgrade.

I'm not sure whether all the findings about the Pultec Clone can be transferred to the 2A-KT. For me, this is the weakest device in the Klark Teknik Clone series. The Opto Compressor has a nice sound signature to my ears even without compression (the transformers can't be that bad), but I can't say anything about gain staging yet.

I'm not either, just saying we shouldn't simply assume this to be an actual "clone".

 

[rock soderstrom]

Yes, I've looked at it with a scope. Fortunately, there's sufficient space in there to put in a simple unregulated linear supply as in the original.

Yes, that is an option. You can also optimize the existing power supply unit if necessary. Perhaps we should install some additional filtering and shielding measures?

I got my third one used (but good as new) for 80 EUR, the seller thought it was defective but it was actually OK.

Okay, you've won the game! 80€ is unbeatable! I think I will also get a second 2A-KT, it's on my watch list.

 

[living sounds]

Yes, that is an option. You can also optimize the existing power supply unit if necessary. Perhaps we should install some additional filtering and shielding measures?

The PSU is on the same board as some of the audio circuitry, I think it's much easier to cut it and wire in a different supply.

 

[JohnX]

I added this photo so that you could see where I had to set the 2A-KT to match the behavior and gain of the LA2A.

It’s a significant difference.