All-discrete GSSL signal path upgrade

[Potato Cakes]

Hello,

So after spending a fair amount of time away from this guy and working on other projects, I've circled back and am trying to finish this guy up. I've sorted the buzz and everything sounds like it's working, but I'm trying to incorporate a send 'n' blend circuit with the cavendish. I've picked the spots that seemed to make sense for extracting dry and wet signals, but I what I'm running into is the dry signal's polarity is reversed from the wet. I can get the blend circuit to work without the Cavendish just fine and vice versa, but since with the discrete mod replaces the dual IC op amp with a single op amp, I haven't been able to find a spot return the signal back to the Cavendish without cancellation of the wet/dry signal. What I think is going to end up happening is that I use the DOA for the input, use the NE5532 on the output, take a signal off of the OUT 2 pin and return it to the OUT connection of the second DOA on the Cavendish (minus the op amp, of course) so that it hits the transformers before being set free. I could also incorporate another transformer wired out of polarity (which I'll experiment with just to see), but then we start getting into silly town. If I have overlooked something on the schematic where I can get in and out more sensibly without cancellation of the two signals, I'd love to know

I know some here would just say leave one of those boards out, and I generally would, but this was one of my first projects and after much pain and agony that goes with being new at DIY audio and wanting to do all the cool tricks and mods at that same time, I'm just wanting to wrap this up as I am trying to finish all the other builds I have sitting around before I attempt to do any more projects. I'll do a fun post on GSSL help thread when this is all done.

Thanks!

Paul

 

[JCT Audio Designs]

When you make the jumpers for the 5532, don't forget to transpose the two op-amp halves:

For the 5532 *ONLY* (the 5534 is just pin-to-pin)
Pin 1 transposes with pin 7
Pin 2 transposes with pin 6
Pin 3 transposes with pin 5

Hey Keef,

I was just about to put in the new Cavendish board when I thought I had better double check a couple of things. It looks like the pins on the 5532 are still wrong and still need to be transposed. Is this correct?

 

[JCT Audio Designs]

When you make the jumpers for the 5532, don't forget to transpose the two op-amp halves:

For the 5532 *ONLY* (the 5534 is just pin-to-pin)
Pin 1 transposes with pin 7
Pin 2 transposes with pin 6
Pin 3 transposes with pin 5

Hey Keef,

I was just about to put in the new Cavendish board when I thought I had better double check a couple of things. It looks like the pins on the 5532 are still wrong and still need to be transposed. Is this correct?

Ok for those of you who buy the new board, the pin swap is still necessary, once you do it,  it works great!!

 

[Blahpstick]

Hi there!  I've attempted to incorporate the Cavendish into a Serpent Audio SB4000 build.  It sounds fantastic!  However, it ends up circumventing the relays that shuttle the unaffected signal to the output XLR's when in bypass mode.

Here's a link to the schematic:
http://dl.dropbox.com/u/4740474/SB4000_Production/SB4000_REV4_FORUM.pdf

I tried taking leads directly from the relays' (K1 and K3) pins 3 + 10 and soldering them to the bottom of the Cavendish output header so that signal will reach the output XLR's when the unit is in bypass or turned off.  When it's turned off the signal is at unity, but with the unit powered on and the compressor in bypass mode the signal drops by 10 dB.

What am I missing?  I certainly hope it's something simple.  Thanks in advance for looking

 

[DrywOwens]

Here's the pic I promised! (I'd have more, but I can't attache them on the text field...)

Cinemag CMOQ-2S trannies, Sound Skulptor SK25 op amps and Elna Silmic II caps in the signal path. Brilliant!

I finally got my "regular" GSSL back, and I've done some A/B testing with the Cavendish one... The differences are subtle, but still  perceptible. It's always a pain to describe sonic things in words, but I'll give it a go. Please bare in mind: this is all very subjective!   

Cavendish feels more even across the spectrum. It seems to create a wider and more open feel, it "breathes" a tad more. Low end is a bit "bloomier", and sounds a bit more natural to my ears. It does feel bigger and deeper, as SSLtech said.

But I like especially the high end: the top end sound much more interesting, Cavendish makes the high end really sparkling. The regular GSSL feels a bit more "plastic" as far as it's low- and high-end is concerned, but "plastic" in a good sense... Like Bubble-Gum-Pop-Music sense! 

Nevertheless, the most prominent difference is in the middle frequencies: the regular GSSL is more forward-sounding, it has a notable "mid-bite". Cavendish is more even, and as I said, it "breathes" more, giving a bit more open feel. But I do like the regular GSSL's "attitude" also!

How much do they differ? I guess that the importance of those subtle differences is highly subjective... But at least to me they're significant enough that I want to keep them both!

How did you transpose the Cinemag lead colors to the colors specified on the Cavendish board? The colors on the board are specific to the 2503, and we have both chosen the Cinemag route. Thanks in advance!

 

[andow]

Do you have any tips on how to connect the IC sockets of the Cavendish PCB and the main PCB? What are these red connectors you used in post #1, Keith?
Thanks!

 

[SSLtech]

I used Aeries Electronics 08-600-10...

Digi-Key, or Mouser or Allied should have them, I think.

Keith

 

[andow]

I used Aeries Electronics 08-600-10...

Digi-Key, or Mouser or Allied should have them, I think.

Keith

Thanks!!

 

[innercityman]

I used Aeries Electronics 08-600-10...

Digi-Key, or Mouser or Allied should have them, I think.

Keith

I also  thank you for this information because I asked it on the GSSL's add on thread and got no answer.

 

[DrywOwens]

Alright... I have finished putting the cavendish board in and it does not seem to work... There is no output on the left, and the right puts out a am very quiet and static-y sounding version of my mix. I was very careful to make sure my connections were all solid. Any ideas on where to begin troubleshooting? By the way, I am using Cinemag CMOQ-2L trafos and inward connections vf600 op amps. Thanks so much in advance for any help!

 

[DrywOwens]

I should also mention that the meter seems to register gain reduction normally, which tells me that there may only be a problem with the output... I made sure to transpose the pins so that pins 1, 2, and 3 from the 5332 IC headers on the Cavendish board went to pins 7,6, and 5 on the GSSL (actually a Stam) board. Did I perform the transposition correctly?

 

[Potato Cakes]

I should also mention that the meter seems to register gain reduction normally, which tells me that there may only be a problem with the output... I made sure to transpose the pins so that pins 1, 2, and 3 from the 5332 IC headers on the Cavendish board went to pins 7,6, and 5 on the GSSL (actually a Stam) board. Did I perform the transposition correctly?

Does the Cinemag transformer color code match the EA2503 which the print on the circuit board matches? Did you meter voltages on the DOA sockets without the op amps installed? The static noise makes me think voltage isn't getting to where it needs to be.

Thanks!

Paul

 

[DrywOwens]

Does the Cinemag transformer color code match the EA2503 which the print on the circuit board matches? Did you meter voltages on the DOA sockets without the op amps installed? The static noise makes me think voltage isn't getting to where it needs to be.

Thanks!

Paul

Paul, thank you SO much for replying.
My research (https://groupdiy.com/index.php?topic=16767.0) tells me that the Cinemag CMOQ-2L lead coloring should match the standard 2503 lead colors... However, I have not checked the DOA voltages. Should I do this using the test points on the Cavendish board?
Thanks!
-Dryw

 

[DrywOwens]

OK - a quick discovery to mention here.  I did check the test points on the Cavendish board and found that every  one read around +/- 15v DC, except for TP3, which was a little over 6v... It seems I have some checking to do on the the sockets coming to that op amp location...

 

[DrywOwens]

Ok - I found that I had broken a trace when lifting one of the 5334 input stages from the main board. I was able to repair this trace and I now get audio from both left and right channels. However, I am still experiencing the very quiet, static-y sound from both channels rather than a full-volume signal.
I have checked the V+/- values from each DOA, and found these to be reading ~+/- 15V as expected.... Also, the unit is registering gain reduction on the meter, which tells me that this must be an output issue? Any more ideas as to what could be wrong??
Thanks so much in advance... I am really eager to get this working!
-Dryw

 

[Potato Cakes]

Have you tried different DOAs?

 

[DrywOwens]

Have you tried different DOAs?

Good point... I just placed the DOAs for the Cavendish board into a couple 312 style preamps I have and the DOAs seem to be working great.

I'm wondering if I somehow messed up the output lead transposition. I made sure to transpose the pins so that pins 1, 2, and 3 from the 5332 IC headers on the Cavendish board went to pins 7,6, and 5 on the GSSL (actually a Stam) board. Does that sound right to you? I did not run leads from pins 5-6 (Cavendish board) to pins 1-2 (main board) per SSLTech's method.

 

[DrywOwens]

To any poor soul who is going through the same thing with their compressor, I did figure out the problem.  It turns out on my "GSSL" (Stam SA4000),  The lead transposition is not necessary.  It works great now. I do have one question though - it seems inserting the compressor in bypass yields a significant level drop. Has anyone else experienced this?

 

[giro1991]

I used Aeries Electronics 08-600-10...

Digi-Key, or Mouser or Allied should have them, I think.

Keith

Hi Keith I'd like to send you a PM but your inbox is full!

 

[andow]

Me too, same with Rochey!
Maybe somebody else can answer this:

I'm building a GSSL with Cavendish mod and was wondering about the assignment of the EA2503 leads.

On the PCB I can see that the grey/violet windings (which are outputs in the data sheet) are used as input and brown/yellow with red and orange shorted as output (which according to the data sheet is a combination of input and output).
What is the reason for the use of this unusual assignment?

Thanks!