fripholm

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #620 on: March 12, 2021, 12:36:53 AM »
Does that sound like it could be the self oscillating output?

It is possible.

Have you tried a series resistor from the output to your output transformer? Does it change when you touch/move the wires of the output knob?


Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #621 on: March 16, 2021, 12:43:57 PM »
I haven't tried the resistor yet, but I did seem to eliminate the static by redoing the wiring using shielded cable. I think this also helped cut down on the hum some more. I definitely get a hi-pitched oscillation when I unplug the byp2 connection, but since that won't be the case when I'm using the unit, I don't think it's anything to worry about.

Now I'm getting an issue where the second channel is really quiet, but I'm assuming I messed something up doing the rewiring, so I get to check my work again. I think this thing is cursed!

octavez

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #622 on: March 24, 2021, 05:28:00 PM »
I'm also having what I supposed are diode noise issue, but before ordering a bunch more here is an audio test so you guys can confirm it (the drums loop stops at 23s and the noise will rise up):

https://www.dropbox.com/s/seqjvnnj87pr4gc/zener-limiter-noise-1.aif?dl=0

The diodes I'm using are from Mouser: On Semi 1N5231C

Thank you!

fripholm

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #623 on: March 25, 2021, 05:24:35 AM »
This definitely sounds like a lot of compression on the drums before the noise kicks in. Was this recorded with the level controls fully clockwise?

If I crank the input and output controls all the way up on my units, the noise is almost that high BUT it's pure white noise whereas yours is more pink-ish with lots of low frequency movement and a rustling paper-like quality to it. I haven't heard that before. The compression sounds great, though.

As I was lucky enough to have not run into noisy Zeners myself, I can't really tell whether the diodes are at fault here but it is possible. Maybe the noise sounds familiar to someone else who had to deal with this problem...

BTW: these are the ones from my units. HTH

octavez

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #624 on: March 25, 2021, 02:59:02 PM »
Thank you for the update! So with no signal that crackly pink noise is constant at around -40db wherever the setting is on the input attenuator (output attenuator all the way up), that sounds a bit too much right?


fripholm

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #625 on: March 25, 2021, 04:43:36 PM »
at around -40db...

I don't know what those 40dB are referenced to (0 dBu, dbV, dBFS etc.) but generally speaking, if there's just 40dB of headroom then the noise level is too high, yes.

octavez

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #626 on: March 25, 2021, 04:47:00 PM »
I don't know what those 40dB are referenced to (0 dBu, dbV, dBFS etc.) but generally speaking, if there's just 40dB of headroom then the noise level is too high, yes.

I meant -40dBFS.

octavez

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #627 on: March 29, 2021, 08:24:14 PM »
I managed to find some nos Fairchild 1N751A. The unit is dead silent now!! So yeah those 4 diodes are a pretty big deal.

I was wondering if there is a proper way of measuring the amount compression, to make sure the meter is properly calibrated?

fripholm

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #628 on: March 30, 2021, 05:41:33 AM »
The build guide for my OP76 FET compressor boards explains a very similar procedure where you're using your DAWs level meters to calibrate the gain reduction meter. Both compressors share the same workflow/mindset with their fixed threshold so it should be easy to adapt.

You can find it in the first post of the OP76 build thread here. It's on page 7 under "Gain reduction meter tracking".

You're basically looking for a fixed difference between input and processed (reduced) output level and adjust the GR meter to that value. Don't expect high precision.

Sorry for the shameless advertising  8)

octavez

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #629 on: March 30, 2021, 12:18:24 PM »
Haha awesome will check it out! Thanks a lot for being so responsive!


JMan

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #630 on: April 10, 2021, 02:59:08 PM »
After putting it off for awhile, I'm returning to finish up this project.  I've created a complete wiring diagram for myself, but I'm wondering about this connection.  I've never done a stepped attenuator before.  I'm following the build manual for resistor values on a 24-position switch -- I splurged on Elmas -- but I want to double check that my wiring connections are correct.  Can someone confirm if I've done this right or if I've got it backwards?  (I'm attaching an image of the input connection, but my output looks the same -- square pad to pos 24/full CW, middle pad to pole, third pad to pos 1/full CCW)

fripholm

Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
« Reply #631 on: April 11, 2021, 01:53:43 PM »
Had to open my stereo unit to confirm: your diagram is correct.

Might help others as well, so thanks for that! :)



 

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