Gates Sta-Level possible transformers (mod)

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Val_r

Well-known member
Joined
Jun 5, 2004
Messages
306
Location
Naples, Italy.
Hi,

The original transformers in the Vari-Mu Gates Sta-Level appear to be:
Input: 600R:10K, 1:4
Output: 8K p-p:600R, 3.65:1

Maybe the input could be a 1:1, 10K:10K
a better choice with today DAW signals, did anyone try?
Comments and suggestions are welcome.

Respect,
Val.
 
I just posted this the other day. In fact, you already asked this:

http://www.groupdiy.com/index.php?topic=26163&highlight=stalevel

No good reason 10K:10K wouldn't work on input with apropriate considerations for the input attenuator. Losing the 50K input and going 1:1 means you don't need the built-in 20db input pad.
 
[quote author="emrr"]I just posted this the other day. In fact, you already asked this:

http://www.groupdiy.com/index.php?topic=26163&highlight=stalevel[/quote]

Oh yes, I couldn't find it anymore.... thanks.

No good reason 10K:10K wouldn't work on input with apropriate considerations for the input attenuator. Losing the 50K input and going 1:1 means you don't need the built-in 20db input pad.

Sure, I don't need the input pad, I was thinking of putting an input attenuator (like the one on the output, with proper resistances values) to control the input, and going with the 1:1 for the input transformer.
Maybe a Sowter 3575.

:roll:
 
Are you going to use 6386 tube or replacement? Retro Instruments is using 6BJ6s and people seem to like it this way. I never tried it.
Read the review from this site:
http://vintageking.com/Retro-Instruments-Sta-Level-Tube-Compression-Amplifier
Looks like they are using Cinemag transformers.

Miha
 
Interesting stuff i have DIYed Ba6A with way too much leve,l I got large pad on the output takes level right down seems wrong to me... ..maybe I could change to a 1:1 input ? I think id have to keep OPtran the same ?
dont quote me but Sowters LA2A transformer were 1:4 ins instead of 1:10s and now theyv introduced one same as originals 1:10

Got a related question if no one minds, I also DIYed a AM864 few years ago, I used Sowter input & OP tran from BA6A I also tried a Sowter 9045 mic input I made a input atten but soldered all wrong resistors in it..Doh!.....I think I ended up with 500 Ohm instead og 500K...I still didnt realize & it worked .....it sounded great when not limiting !when limiting it was just to harsh too sensitive but certainly crushed the sound.
I realized my mistake and corrected it...but then I got lots of that dreaded thumpy poppy noise the DC control voltage, this was all long time ago ..there thread here somewhere I think still ..anyway at the time I tried allsorts but gave up...im thinking of having another go now.

Anyway after all that my question was is the input tran crittical ??
Is there a certain relationship between Input tran & value of attenuator

I love these old Vari Mu thing im currently makinag a tiny chiswick vk1.

Thanks
 
[quote author="Val_r"]Sure, I don't need the input pad, I was thinking of putting an input attenuator (like the one on the output, with proper resistances values) to control the input, and going with the 1:1 for the input transformer.
:roll:[/quote]

you can use a T, H, or Ladder in front of the unit, or use the dual pot after the input transformer. All will work. All require slightly different impedance loading attention / re-arrangement.
 
[quote author="emrr"]I just posted this the other day. In fact, you already asked this:

http://www.groupdiy.com/index.php?topic=26163&highlight=stalevel

No good reason 10K:10K wouldn't work on input with apropriate considerations for the input attenuator. Losing the 50K input and going 1:1 means you don't need the built-in 20db input pad.[/quote]

In my experiences building sta level (4 now) The input pad is completely unnecessary anyway, even with the regular input transformer ! I think you need the bit of extra gain off the original input transformer to be able to drive enough level into it to for it to compress. You don't need an input attenuator, it's unnecessary, just use the dual pot.

The place where you need an attenuator is on the output or you will will not be able to turn the input up enough for it to compress at all without blowing up the inputs to a solid state desk or DAW. This compressor has a VERY lively output after all it is essentially what would be a 12Watt amp (2 x 6v6) in the hifi/guitar amp world.
 
[quote author="rotation"]Are you going to use 6386 tube or replacement? Retro Instruments is using 6BJ6s and people seem to like it this way. I never tried it.
Read the review from this site:
http://vintageking.com/Retro-Instruments-Sta-Level-Tube-Compression-Amplifier
Looks like they are using Cinemag transformers.

Miha[/quote]

I am going to try the 6BA6 wired in triode mode.
I am posting the characteristic curves I am currently getting out of a Sylvania 5749 W tied this way. Curves look very similar to 6386.
Hope this can be useful for you all guys!

5749.jpg
 
As soon as I get my hands on a 6BJ6 I will post the curves, in the meantime...
Has anyone tried personally to compare the sound of the 6386, 6BA6, 6BJ6 ?
 
I just feed a microphone directly into my STA Level, without the pad, off-coarse... It´s perfect this way. Whenever I need phantom, I use an external box.
 
[quote author="Val_r"]As soon as I get my hands on a 6BJ6 I will post the curves, in the meantime...
Has anyone tried personally to compare the sound of the 6386, 6BA6, 6BJ6 ?[/quote]

Look for the old vari-mu threads with discussion between Larrchild and PRR. I think Larr posted curved for the 6BA6. Also, I'm pretty sure dale116dot7 built a comp with 6BA6s.

http://recforums.prosoundweb.com/index.php/m/76243/998/?srch=vari+mu#msg_76243

http://www.groupdiy.com/index.php?topic=909&highlight=6ba6+compressor

http://www.groupdiy.com/index.php?topic=7114&highlight=6ba6+compressor

http://www.groupdiy.com/index.php?topic=2711&highlight=6ba6+compressor

http://www.groupdiy.com/index.php?topic=23067&highlight=6ba6+compressor
 
This is the input pad I am using.
The problem is:
When the output of the soundcard (a Digi 001) is high, say at max (0 VU, +17.8 dBu, 6.02Vrms), the wave at the input of compressor is already clipped.

I think it happens because the card is not happy when it sees a too low load impedance.

As you can see, I have used a Lundahl LL1540 as input transformer, wired for 10K:10K.

Any suggestion?

input_pad_varimu.jpg


Thank you,

Val.
 
I no this old post Val but was wondering how you got on with th Ba6 tubes in your Gates Sta lev....cheers
 
gary o said:
I no this old post Val but was wondering how you got on with th Ba6 tubes in your Gates Sta lev....cheers
Yes, so old I forgot the existance.
I feel 6BA6 has better stability than 6BJ6.
It is wired triode mode with Anode and G2 to B+, G3 to Cathode.
I want to try with G3 tied to B+ too.

I don't have a 6386 to test.

Tried the LL1540 and 3575 as input: I like the Sowter much much more!
All for now.

Respect,
Val
 
Cool so the lundle was higher ratio then ? glad yr liking Sowter better tho...You still have enough level to drive into limiting then ?
Ive often thought about the amount of wasted gain in my recording channel as it were Im not saying it is but sometimes it seems like Im wasting so much getting the level low enough because the next tran is going to step it right up again.....I do seem to like the sound of iron but makes me wonder how things would sound if I made a recording channel with the minimum amount of transformer and attenuattor use if you no what I mean.

For a couple of days I was messing with two vari mu circuits to make a hybrid monster I practically had a Gates circuit on my bench at one stage ....It was fun and sounded great at certain stages it has been shelved for now but will dive back into it soon.....

http://www.groupdiy.com/index.php?topic=31418.0
 
Lundahl/Sowter:
No , they were wired 1:1, for 10K:10K
Max dB GR is around 10-12dB, but I still like it.
It is a stereo unit, with the stereo link, and it comes useful all the time (in the mix)
Tracking is fun enough.

6386:
Sure, it would be better, it is a REAL triode, after all.
I would need a nice matched pair for stereo operation.

But I agree with you, sometimes you find those tubes.

Respect,
Val
 
They're custom wound (M6 lams):
I wanted to try different loading and the 43% tap to try the 6v6 in ultra-linear mode too.
Sowter, Lundahl, and Hammond too stock suitable transformers for this task. (I tried Hammond and sounds really smooth).
 
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