WA-1B Tube-Optical Compressor (Tube Tech CL1B)

[Ó Draighnáin]

Have they all (the units in post #20) been in continuous production by the original manufacturer? Take the Helios mic pres as an example (not on the list, I know). There are pres currently being sold under the Helios brand name but that is a different company to the company that was previously selling under the (if not "the" then "a"?) Helios brand. There are also pres being sold that use the word Helios in describing the units (e.g. "The legendary Helios Returns"), are stylised the same but do not use the Helios logo or brand name.

I believe Arny used to claim to have rights to the use of the name from Swettenham himself. The below link indicates otherwise:

https://www.helios-electronics.com/legal/helios-companies

I have no idea of the truth. And then there is this company:

https://h2audio.com/#products

It does make me wonder what of the current production of LA2As, 1073s and the like, is a rebirth from someone acquiring rights to the brand? Tantamount to someone producing their own clones but also having rights to the original logo/brand company name?

There is a difference between someone handy with a soldering iron building a clone for personal use and a clone company piggy backing. No doubt there are grey areas. What Warm is doing is unashamed. At least the JTM45 dress was completely different to the Bassman (not the same shade of blue).

I will never buy a WARM product, but you can be certain they don't care about that, I am not their target market.

 

[Tubetec]

What miracle mods did you perform on the KT LA2A to make it better Living Sounds ?

From my recent experience with the EQP-KT its pretty clear anyone who says you can just bang an SMPS in box next to a tube circuit is wrong ,
ok if you limit the bandwidth of your measurements to 20hz-20khz , it might look ok , but take a look at the 70-100khz region , its got more bristles than a porcupines ball sack ,

With a transformer your dealing with mainly 50/100 or 60/120 hz noise , the byproducts when this intermodulates with your audio arent nearly as objectionable as what happens with an SMPS , When your nice tube stage clips if theres garbage from an SMPS in the wires that gets superimposed on your audio waveform on the peaks and it starts to sound like shit .

The designers of the original Pultec had to go to great expense with sheilded mains, signal transformers and chokes everywhere to get the amazing noise figures , EQP-KT comes out some 20db worse ,
Im making a very simple remote PSU with only passive smoothing for the EQP-KT , it should get the noise down lower than the original Pultec design without any fancy parts , mainly stuff you can get off the shelf in any electrical wholesale outlet and other bits that are easily found from the recycle pile .

Theres no doubt some of the WA products torndown here were shocking , I think it was the 87 clone , even the Chinese are designing better tube mics that that now .

 

[living sounds]

What miracle mods did you perform on the KT LA2A to make it better Living Sounds ?

Signal path tubes, signal coupling caps and T4B. I haven't looked into the power supply lines, but maybe adding an LC filter might be a good idea? Should HF noise show up on the power lines, is there any reason not to do it? I found problems of power sag with an aftermarket switch PSU in my Oberheim synth and changed that for a SMPS -> LC filter -> linear regulator design. But if the LA2A clone runs in class A I would expect sag to be less of a problem...?

The KT LA2A is not excessively noisy at least.

 

[Tubetec]

Sag isnt the issue , its RF leakage from the SMPS getting into the cored components ,

When I'm looking at noise of course its not anything like a real world situation ,
Im applying 60db gain after the EQP , the noise radiated from the SMPS is getting through the sheilding on the input transformer and into the high frequency inductor and I cant see anyway of stopping that from happening without removing the PSU from the enclosure .

I dont think an LC filter will work as its radiated noise from the SMPS transformer thats the issue , an inductor might even worsen the situation and allow another path for radiated noise to get in .

I didnt get a chance to bench test the EQP with external supplies yet ,but I will soon .

 

[living sounds]

Sag isnt the issue , its RF leakage from the SMPS getting into the cored components ,

When I'm looking at noise of course its not anything like a real world situation ,
Im applying 60db gain after the EQP , the noise radiated from the SMPS is getting through the sheilding on the input transformer and into the high frequency inductor and I cant see anyway of stopping that from happening without removing the PSU from the enclosure .

I dont think an LC filter will work as its radiated noise from the SMPS transformer thats the issue , an inductor might even worsen the situation and allow another path for radiated noise to get in .

I didnt get a chance to bench test the EQP with external supplies yet ,but I will soon .

Sag was the issue with the switch PSU + LC filter that was installed as an aftermarket in my synth, that's what i was referring to. I'll have a look at the KT's with the scope soon.

 

[living sounds]

I looked at the KT-2A PSU with a scope. There is indeed not insignificant HF noise residual. Some of it is still present in the output.

The original schematic asks for 275V, the KT-2A runs on 235V B+. 100V is present in the signal path where it should be though.

Lacking a schematic and with the design as it is I indentified an RC filter at the output of the PSU board and added a series inductor I had l (1 mH) as a test. Didn't to anything. Beefing up the filtering cap with another one in parallel didn't help much either. The transformer is clearly radiating HF noise (getting the scope probe near it makes it obvious), but it is physically far away from the transformers.


Apart from some low level residual HF noise - can the HF noise on the PSU lines noticeably impact sound quality?

 

[Tubetec]

I believe it does have an impact , especially on the peaks where intermodulation occurs ,
filtering the output of the device with 20-20khz improves the noise picture , but that doesnt mean its not there causing artifacts .

If you look closely with the scope at a tube circuit clipping any noise on the PSU rail gets superimposed onto the peaks and you end up with more higher order distortion products .
Out of sight maybe be out of mind , but its not beyond detection with the ear .

Unforunately typical test signals are of limited use in telling us how a device sounds when driven ,

A pure sine wave at 440hz is a good enough quick test , as you increase the volume you'll hear the overtones creep in , you can be sure if theres RF in the mix its gonna turn nasty .

From what I see in the EQP the input transformer and SMPS cores look like there in the same plane which means maximum interaction , there may be some benefit from re-orienting the input transformer or even replacing it with a nice Haufe with decent mumetal sheilding ,

Its seems like were giving a free lunch to WA by continuing this thread ......