Drip Dual-STA 5167 Limiter

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morls

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-All voltages within 5% (Increased R23 from 150-220 ohm to get -12V @ cathodes 6v6)
Sounds interesting. I'm still trying to work out how to balance these 6V6s. I've seen posts detailing a method of inserting a 300Hz signal (with no input to compressor) to the grids of both 6V6s, which is pin 5 I think, and then adjusting the trimmer following R23 for lowest noise. I haven't found a way to do this yet, maybe at the front of R21 and R22?

I've also changed R24 to a 2W. I don't know if I missed something in the Drip BOM or documentation, but it was 0.5W while the original schematic has 2W There was some heat damage on the 0.5W I replaced.
-Now running matched 6BA6 on a t-bar mod. (works very fine, even more compression then some of the JJ 6386)
I changed R8 and R9 to 56R here, to adjust for the T-Bar/6BA6.

I also checked all voltages at 15dB compression (pink noise), and they're really close to the schematic. I went through and reflowed all the solder joints. I don't know if it was this, the change to R24, or both, but both channels now sound fantastic, I can push the compression at time setting 1 to 25-30dB without any thumping. Levels are much better matched between channels as well.
 

schrobbelbop

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ve also changed R24 to a 2W. I don't know if I missed something in the Drip BOM or documentation, but it was 0.5W while the original schematic has 2W There was some heat damage on the 0.5W I replaced.
Just before i sent this message i've noticed R24 needs to bee 2W indeed. I'm currently having the 0.5W which is overheated so maybe that will help replacing. might be the problem right there... wrong on the bom/pcb

I changed R8 and R9 to 56R here, to adjust for the T-Bar/6BA6.
Why do the need to be adjusted?

For balance 6v6 i adjusted the trimmer so voltages are equal on both kathodes.
Same for the 6ba6 balance.
You can also crack the output to max and listen for any hum, the 6v6 balance will (almost) cancel the hum
when correctly balanced.
 

FarisElek

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Oct 26, 2019
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I also have the drip Dual boards and they keep a little "thump" / motorboating when compression kicks in.
especially in the beginning of the range 0-10db's. When it's compressing deeper 10-30 db it all sounds very fine.
with a constant sine wave at a constant level of gain reduction (0-5ddb) it keeps thumping/motorboating so not only
on transients.

plate, voltages fluctuate when thumping
Control voltage fluctuates when thumping

What i did and check:
-All voltages within 5% (Increased R23 from 150-220 ohm to get -12V @ cathodes 6v6)
-Running the HV as stated in drips manual, Diode rectifier, Choke, Voltage regulators per main pcb.
-B+ is super steady at 300v
-Changed JJ 6386 ( i had 10 of them)
-Changed all tubes for different brands
-Now running matched 6BA6 on a t-bar mod. (works very fine, even more compression then some of the JJ 6386)
-All sowter transformers

both sides behave the same
This happened to me when I had wires carrying voltage touching wires that carry audio touching eachother near near control panel. I zip tied wires together to keep them away from others.
 

morls

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Jul 15, 2013
Messages
193
Location
Australia
i've noticed R24 needs to bee 2W indeed. I'm currently having the 0.5W which is overheated so maybe that will help replacing. might be the problem right there... wrong on the bom/pcb
Let me know if this makes a difference, I think it did for mine, especially in headroom, but I did reflow the joints as well…
 

schrobbelbop

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Mar 7, 2010
Messages
141
Location
Eindhoven, Netherlands
changing R24 to 2 Watt and reflowing didnt solve the thumping.
it only happens when going from 0 compression to a little bit.
Deep compression sounds fine.

When I pull out 1 6v6, the thumping dissapears so i guess
it must be an imbalance somewhere...

Changed all resistors to 1% metal films.

Currently running JJ 6V6 / EH 12AT7 / JJ 6368 or ALGRA EF93 / Telefunken 6AL5 / Philips OB2

Ordered Diffrent brands for 6V6 (Genalex/Mullard) and Philips NOS 12AT7 balanced. let's try that...
 

JMan

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Oct 26, 2019
Messages
332
Location
Chicago
Hey everyone, sorry for the little aside here. Though it pains me to do, I just put my unused boards for the Dual-STA project up for sale in the black market, as I don’t know if/when I’ll ever have the chance to build it due to that old friend Changing Life Circumstances. 🙃 If you’re a lurker on this thread and want to get the boards at a significant markdown from retail, I hope you’ll consider my listing. I also have the Ultra British project for sale.

BM Thread
 

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