Klark Teknik KT-2A

[living sounds]

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.

That's a lot of output gain. I have found the KT2A to be prone to produce clipping-like distortion earlier than most of my gear. Thinking about this some more, I do think they might actually have pulled gain-staging-shenanigans as in their EQ...

 

[JohnX]

That's a lot of output gain. I have found the KT2A to be prone to produce clipping-like distortion earlier than most of my gear.

I never turned it up higher than that so it never achieved any clipping - at least nothing audible or visible. I’m sure that once I start to use this on a regular basis, I will get to know it far more intimately.

 

[timtom]

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.

Any news on the DIY T4b cells? I compared the stock one and the IGS. IGS sounds smoother and for my ears nicer on slower stuff. The Stock sounds good on percussive stuff. Probably slightly different attack release times.

 

[JohnX]

Any news on the DIY T4b cells?

I used the Kenetec & noticed a significant difference - I do prefer the sloer attack & release of the new opto that I put in. It was one of the most significant changes.

 

[Tubetec]

The Klark EQP has 2x10k in series followed by 1k load before the input transformer ,
the unit is specced to accept levels upto +21dbu ,

 

[rock soderstrom]

Any news on the DIY T4b cells?

Not yet, I am on vacation.

 

[rock soderstrom]

You'll find more info about T4b cells here
https://groupdiy.com/threads/t4b-docs.55562/

 

[rock soderstrom]

I would also like to build a variant with vactrols. Let's see how that sounds...

 

[scott2000]

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...

Was listening to some other files and came across these again. Put them on a meter just out of curiosity...

 

[JohnX]

Was listening to some other files and came across these again. Put them on a meter just out of curiosity...
View attachment 133948

I see that I could’ve matched my gains a bit more closely.

 

[scott2000]

I see that I could’ve matched my gains a bit more closely.

still way better than what I compared of mine before coming across these...lol

 

[Script]

Don't have this unit, nor the original it is based on. So easy to ignore me.

Apart from gain, the attack and release times (crest factors?) look slightly different on all three.

So somewhat difficult to compare, I'd think. Cos what works on bass on one might not work on vocals. And while the other is good on one vocalist, it might be less good on another or even on drums. Whereas the third is good on drums, but only when played fast. Otherwise the first might be better ? Don't think there's a fixed timing setting that works on everything. I'd be interested in program material, but then again, the original it's based on isn't cherished for that, AFAIK.

Anyway, either the stock unit is a magic one-trick pony, and it does that trick fantastically, or it works well on many differently enough materials to be satisfying -- no matter it's cheap as a unit. Trying Kenetec cells sounds legitimate to get closer to the original. I do believe a lot of testing and experience went into those replacement cells.

For now, however, personally, I'd be more interested in S/N, sweep, THD and IMD measurements.

Sorry,
The Party Pooper

 

[living sounds]

Was listening to some other files and came across these again. Put them on a meter just out of curiosity...
View attachment 133948

Good call, volume matching is what I usually do and didn't do here...

 

[lovebuzzz]

No two tubes are the same no matter the type, so i re bias them always. For example Universal Audio strongly suggests re-biasing tubes after replacing tubes in their units, you can check UA LA-610 manual for example.

In my experience almost every time someone talks about particular sonic imprint of certain unit there is a fault, or low end bump, high end cut, distinct THD character. This can be achieved with an EQ, or by tweaking of the circuit. None of which cost more than few bucks. But yes, it can be done by spending a lot more money not knowing what you've done at the end.

Is it known how to re-bias tubes in 2a-kt after putting new ones? I know it's a very important thing to do, but I can't seem to find any info on how to actually do it for 2a-kt....

 

[j.colt]

I’m doing a full mod right out of the box… I hope it will pass sound!

 

[j.colt]

There were a few bad things going on with the picture I posted including a filter cap and the A-24 wired the wrong way. But after a bit of tinkering it works great! Here are a few pictures for those who want to replace the transformers as I don't think anyone posted this mod so far. You only need to drill one single extra hole if you are using UTC A-series and transformer ground connection is taken care by the 4-40 screw (no metric screws!!) at the back so you don't need to wire the ground pin to the chassis as it is already connected to the transformer casing screw. For the A-24, it's best to reuse the orange-brown-red-yellow wire harness so cut it at the base of the MIDAS transformer to have enough length. The A-10 is wired using the four outmost terminal on the PCB--it will take a bit of time to remove the PCB MIDAS transformer. I did not adjust any trimmers so far and the GR needle is at 0. The electronic soft start is quite a good idea on this unit. Tube wise I used NOS RCA and GE long grey plate. I did not have any EL84 so I left the one that came with it. I have a no-expense-spared LA-2A build to compare it too so that could be interesting...

 

[ZHOUJUN]

I installed UREI's T4B directly into the KT-2A and was pleasantly surprised. I think the T4B is the biggest variable in the LA-2A, much more so than the audio transformer, so you only need to replace one UREI T4B and you will get a big improvement in the KT-2A.

 

[ZHOUJUN]

Any news on the DIY T4b cells? I compared the stock one and the IGS. IGS sounds smoother and for my ears nicer on slower stuff. The Stock sounds good on percussive stuff. Probably slightly different attack release times.

Another significant difference I found between the original and many copies (including UA) is that the fixed gain of the Urei LA-2A is significantly greater. The difference made by the T4B is the amount of compression and the speed. I like it slower, but some drums may need to be faster. It depends on what you like.