Klark Teknik KT-2A

[Iamkimosabi]

Gotcha. Any idea which of these VR pots adjust the gain reduction characteristics?

 

[AUDIO FREQ]

How would one go about adding attack/release/ratio to this compressor?

 

[abbey road d enfer]

How would one go about adding attack/release/ratio to this compressor?

Attack/release are determined by the optocoupler; it's almost impossible to modify it, even with a completerly different side-chain.
Fuggedaboudit.
Ratio can be tweaked, acting on the resistors that feed the LDR. That is basically what the comp/limit switch already does.
You may find that adding intermediate positions is not really worth it.

 

[AUDIO FREQ]

Ah ok, welp, there goes that idea.

 

[AUDIO FREQ]

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!

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Dude...how in the WORLD did you get that 10uf 400v Solen cap to fit there...mine won't fit on neither the front or rear...I had to hot glue the capacitor on top fo the transformer and feed the leads to the holes with wires.

 

[gyraf]

Attack/release are determined by the optocoupler; it's almost impossible to modify it

When I was a kid, I gave this a lot of thought also: The characteristics of the LDRs are somewhat temperature dependent - I was thinking about adding a peltier cooling system, and thereby messing with timing. Never got around to it though, too much resistance from regular studio users at the time...

/Jakob E.

 

[AUDIO FREQ]

When I was a kid, I gave this a lot of thought also: The characteristics of the LDRs are somewhat temperature dependent - I was thinking about adding a peltier cooling system, and thereby messing with timing. Never got around to it though, too much resistance from regular studio users at the time...

/Jakob E.

Makes me wander how in the world Tubetech did it with the CL1B. J Petersen must be a genius.

 

[gyraf]

Naa, that was simple enough: running a much faster opto on rectified and timed DC - this is a very different concept. The hard part is to do timing on/within the T4B which is notoriously all-slow already

 

[AUDIO FREQ]

Naa, that was simple enough: running a much faster opto on rectified and timed DC - this is a very different concept. The hard part is to do timing on/within the T4B which is notoriously all-slow already

I think Kenetek sells a "fast" t4b. Still too slow?

 

[gyraf]

The T4b is meant to be activated with simple AC - and the time constants are in the EL-panel and the photoresistor. It's a different beast than later designs - look at e.g. LA4 for a more modern take on the optocompressor

 

[AUDIO FREQ]

The T4b is meant to be activated with simple AC - and the time constants are in the EL-panel and the photoresistor. It's a different beast than later designs - look at e.g. LA4 for a more modern take on the optocompressor

Ah ok, will do!

 

[living sounds]

Dude...how in the WORLD did you get that 10uf 400v Solen cap to fit there...mine won't fit on neither the front or rear...I had to hot glue the capacitor on top fo the transformer and feed the leads to the holes with wires.

I simply fit it on the front of the PCB, there is enough space (did it successfully in 3 units).

 

[AUDIO FREQ]

I simply fit it on the front of the PCB, there is enough space (did it successfully in 3 units).

Ok ill give it another go.

 

[Forcemusicgroup]

Is there a BOM for the KT-2a Mod? or if anyone can list the parts needed that would be great.

 

[abbey road d enfer]

Dude...how in the WORLD did you get that 10uf 400v Solen cap to fit there...mine won't fit on neither the front or rear...I had to hot glue the capacitor on top fo the transformer and feed the leads to the holes with wires.

Not the best idea. Transformer gets hot, capacitor lifespan decreases 10 years for each 10°C increase.

 

[Rowboat]

Here is a vocal track i found dry and compressed with true LA-2A. So i matched GR as best as i could, and got some pretty amazing results. I found that original LA-2A saturates a bit more at high end, and even sounds a bit pointy at sibilant letters. Could be that output was driven a bit more.

Other than that, i would call these two almost identical. For about 300 bucks, KT-2A is a no brainer.

True LA-2A
https://app.box.com/s/yy41uru6jijn06m28ley0abnd780k313
Klark Teknik KT-2A
https://app.box.com/s/58m0aiqtap6jcjyhzklp2qoptr6yzgqf

Pretty much indistinguishable.

 

[AUDIO FREQ]

Not the best idea. Transformer gets hot, capacitor lifespan decreases 10 years for each 10°C increase.

Yeah I don't know how else to mount it. I tried again, even removed the pcb entirely and tried to fit behind like the other guy did, but it's just too thick.

 

[mattenylander]

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.

I’m planning to mod my KT-2A cause I find it compressing the highs a bit to much even when the pot is set to flat.

To my understanding the C14 and C4 are responsible for the frequency response of the LA-2A and the side chain circuit.

Do you happen to know which capacitors would correspond to C14 and C4 on the KT-2A unit?

 

[abbey road d enfer]

I’m planning to mod my KT-2A cause I find it compressing the highs a bit to much even when the pot is set to flat.

What pot?

To my understanding the C14 and C4 are responsible for the frequency response of the LA-2A and the side chain circuit.

I don't see a C14, unless it's the 50-380pF trimmer near the Peak reduction control pot.
Both C14 and C4 are trimmers, that are adjusted under test.
Since trimmers are expensive and induce extra labour, I would think that KT have replaced them with fixed values.

 

[mattenylander]

What pot?

I don't see a C14, unless it's the 50-380pF trimmer near the Peak reduction control pot.
Both C14 and C4 are trimmers, that are adjusted under test.
Since trimmers are expensive and induce extra labour, I would think that KT have replaced them with fixed values.

Oh I mean the pot on the chassi, Pre-Emphasis.

I found a C14 but it’s a 1μF electrolytic so I don’t think the KT-2As components are labeled the same as on the LA-2A schematic but I’m not sure…

Yeah you’re probably right!
I found 3 ceramics which has,47pf and 2x 471pf.

Which is the closest caps I can find to match the LA-2As variable capacitor range.