great, I just needed a little push into 1176 land... Cool
Welcome!
I make my UN76 commercially, stereo in 2RU, same gain reduction circuit,
but with Neve class A output stage, my output trunny's (HI-B C-core),
and some other tweaks, about 5 years. First version of UN76 was done for my friend,
http://tantanstudios.com/gear /just for impression
few initial questions:
-which revision is this based on, and what changes (if any) to the original sound/functionality, except the very welcome addition of SC HPF?
About revisions,
http://www.uaudio.com/webzine/2003/august/index4.htmlFor now, I made DOA adapters PCB's for input and output amplifiers as in 1176 REV. F.
Most of discrete op-amps as well as adapter board for NE5534/etc will work here.
51X-F76 done to work in both 51 and 500 cases, it is matter of amplification stages used.
A chance to try 1176 with Forssell FET or JLM op-amps!!!
Maybe, I will do single ended output amp PCB like in rev. A-E.
The problem is there's no A-E rev. (5002) output transformer substitute which fits into 500 format.
I added current source at the output stage of input amplifier (lower output impedance,
possibility to use 10k log pot for output control),
and changed some resistors values to let it work right at 24V.
For those who cares about sound signature of amplifiers,
it is same at analyzer and sound-wise; I run input amplifier at +24V
in my UN76 for years with this mode.
Most of sound comes from transformers and distorted FET; it depends how "distortion" trimmer
(R16 according to orig.1176 rev F) is (mis)adjusted.
Another tweak-up/down's..... Ratio 1:2 is useful with vocals, guitars, soft
coloring compression, etc.
I want to try 2520 at output stage with API output trafo.
SLAM mode: when ratio switch is at 4 or 20 position, it is exactly same way
as it happens when all 4 RATIO buttons IN.
Another "mod", for 51x-F76, circuit before diode rectifier with 4 transistors and
pervert values resistors thrown from there and replaced with 2 op-amps. It does not affects
neither sound nor compression, but saves some space on PCB and makes build easY-er.
I prefer stepped attack and release controls, release control /11-pos switch/ done as 5meg log pot.
Attack control is 11-pos switch, acts like 100k extended log pot.
Other values can be used for attack/release.
I can use potentiometers instead of switches, BUT 5meg log pot is impossible to find in size
which fits in 500 format. Recall-ability is matter as well.
(I am delighted to see that the analog meter disappeared, rather than the transformers Grin )
I prefer line level 10k:2k4 input transformer and 2k5 log pot on its secondary for input,
but it is impossible to fit big trunny in 500 format.
Input options are: OEP 2:1 or Altran 0-12 copy with 600 Ohm attenuator;
balanced line receiver like THAT1246/OPA137/SSM2143 with 10k log pot.
/edit: ssm2143, all these line receivers are -6db gain
To run it as cheap drum compressor, I can fit balanced line driver and balanced line receivers instead of trafos and make 8 of 51X-F76....instead of distr/essor's; bad taste but money-saving
Seriously, this can be version to learn how things work.
Yes, all we like analog meters, but no space here.
I will do my test version with Altran O-12 and API output clones from Hairball Audio.
-any plans for stereo link via the 500 series stereo link connection?
Already there. FET matching is pain, but IMHO it works better than summing the signal
into mono before detectors.
June 30, 2010, 11:18:28 AM