Another diode bridge compressor

[richiyobs]

Fig 10

 

[Heikki]

Project is moving along.

 

[Script]

That's a suggestion I made a couple of posts ago, however I don't think it's that useful in practice. Note that it's what the Siemens U273 does, albeit with a different bridge arrangement.

[Just an aside]Thanks for the pointer. Found several U273 with different suffixes and configs. In the attached config it halves the number of diodes needed and thus mismatches, but I'd assume diodes have come a long way since back then.[/aside]

 

[richiyobs]

[Just an aside]Thanks for the pointer. Found several U273 with different suffixes and configs. In the attached config it halves the number of diodes needed and thus mismatches, but I'd assume diodes have come a long way since back then.[/aside]

Hi Script there s a post on u273 with a link with a lot of siemens and tabfunken schematics... I saw 3 version about u273

 

[abbey road d enfer]

Fig 10

Yes. This one is not really a bridge; it's a single string with two diodes in each direction.
THD is not very good.

 

[richiyobs]

Ok good to know
Thanks

 

[Heikki]

Almost ready now. All I’m missing now is the front panel. I ordered one from Schaeffer and it should arrive next week.

 

[richiyobs]

Almost ready now. All I’m missing now is the front panel. I ordered one from Schaeffer and it should arrive next week.

super! geat job
i like the SC boards very much
best

 

[Heikki]

Did some measurements today. At max position ratio gets to about 15:1 and at min position it is about 4:1. Distortion is mostly 3rd harmonic. Measurement made at 1kHz with threshold at min position.

 

[richiyobs]

Which software are you using?
I checked my proto with CMT and read 17.7:1 at max ratio... But it s a vst tool....
I can use Rew for thd but not for other useful measurements..

 

[dogears]

Did some measurements today. At max position ratio gets to about 15:1 and at min position it is about 4:1. Distortion is mostly 3rd harmonic. Measurement made at 1kHz with threshold at min position.

Is this with the 4 diode bridge?

 

[Heikki]

Which software are you using?

I used REW for measuring and put the data to a spreadsheet.

Is this with the 4 diode bridge?

Yes it’s a 4 diode bridge.

I also made some noise measurements to compare this with my vari mu compressor. The diode bridge compressor is approximately 17 dB noisier than my vari mu. Even though the diode bridge noise is less than spectacular I doubt I will ever get into a situation where I would hear the noise. The noise spec is still a couple dB better than the AMS Neve diode bridge compressor has.

 

[richiyobs]

Which spreadsheet? You did on your own or is possible to find online?
Thanks
Cheers

 

[richiyobs]

i tried to import my Rew data in libreoffice....measured thd and exported:
min Thr , min Ratio, slow att and fast Rel
but what came out in the chart is something similar to a slew rate response ....
any suggestions please?

 

[Bo Deadly]

Just create a chart in Excel (or libreoffice). It's just a line chart. Run signal through the device and monitor the input level vs the output level. Increase signal level incrementally and record the input level in one column and the output level in an adjacent column. Do 10 measurements or so. Then just select that data and insert a line chart. Choose a line format that adds a little smoothing. You can speed up the process a little by creating a wav file in wavepad that plays bursts of noise or tones for at increasing levels for 10 seconds each. Then just play the wav and sit there typing in the levels.

I did the same thing for my "OptoGyro" compressor.

 

[richiyobs]

Just create a chart in Excel (or libreoffice). It's just a line chart. Run signal through the device and monitor the input level vs the output level. Increase signal level incrementally and record the input level in one column and the output level in an adjacent column. Do 10 measurements or so. Then just select that data and insert a line chart. Choose a line format that adds a little smoothing. You can speed up the process a little by creating a wav file in wavepad that plays bursts of noise or tones for at increasing levels for 10 seconds each. Then just play the wav and sit there typing in the levels.

I did the same thing for my "OptoGyro" compressor.

Perfect I ll try...
Thank you so much

 

[Heikki]

Which spreadsheet? You did on your own or is possible to find online?

Here’s the libreoffice spreadsheet I made.
http://ghr.fi/proaudio/diodecomp/diodi.ods

 

[richiyobs]

thank you so much... i ll try to follow all info i got
best
richi

 

[Heikki]

Got the front panel yesterday. Also attached is a picture of noise measurement with gain at 11 dB and 20 kHz bandwith.

 

[richiyobs]

Great build!
Are you using the same meter driver for diode comp?