DIY Gates 5215

[rock soderstrom]

Your smiley frequency response could be the result of two reasons:

The boost in the bass range could be a resonance of the coupling capacitor and the OPT. Reduce C3 and see what effect this has.

The boost in the treble range could be a ringing of the IPT. Try to damp this with a Zobel element.

 

[solkatten]

If you are lucky a resistor across the OPT primary could damp the hi freq ringing.... try 10K-20K range maybe...

 

[RSRecords]

I'll muck around with that coupling capacitor. There's also the cap in the feedback too. Should C4 match C3?
Interesting the input transformer is an OG from a gates 5215 the schematic makes no mention any zobel but I’ll check that out too.

For the output, I’m also wondering if I did something wrong with the attenuator. It’s a 500 T across the output wired;

Xfmr out hi to Input
Out Low to common
Xlr Pin 2 to attenuator Out
Pin3 to Common

(shields tied together.)

 

[emrr]

Have 680R on the output of the T?

 

[beatnik]

It would be easier if you built the circuit without mods first

 

[heatwalk]

One of the shops I'm working in has a console with a handful of these pres inside that we recently pulled off the shelf to bring back to life, though with tube shortage might be sent back up to where it was previously sitting... Plans to rebuild the pres after we get the PSU it came with up and running, but thats been giving some trouble thus far. It is a Gates PSU but not the same one referenced in the manual we have

 

[RSRecords]

Only mods are the Variable feedback which is set to close to the schematic 60k (instead of 56k) and the output attenuator which disconnected doesn't change anything.

A 600R didn't change the response much at all but did knock the level down. Not sure if I noted this but the OPT is wired for 600. 250 again didn't change much other than level.

Through trial and error I found a zobel combination that helped with the high end. I can't remember at the moment what the resistor value is (1k maybe??) and a .039uF cap knocked the 20K response to +2.3dB and 18k to ~1dB. Which seems kinda great for ribbons...
Though at this point I might try a different output transformer.

Waiting on some caps to try and even out that low freq bump.

 

[Perm0]

Yes, EasyEDA has a similar feature set. I also had a quick look at EAGLE and KICAD, I think EAGLE is a class or two above EasyEDA but to be honest it doesn't matter to me as I don't even use EasyEDA to its full potential. Most of the stuff I do is pretty simple.

EasyEDA is much more modern and easier to handle. Not as old-fashioned as KICAD. This familiar, modern handling was one of the reasons why I went with EasyEDA. It is really easy to learn.

I have to admit, I don't use the schematic editor that much, I draw my layouts directly by hand in the PCB designer in EasyEDA, which actually works and is another plus for me and my way of working. Quick and dirty, you can get results very quickly.

That's why I don't use autorouting, but I think this function is also available in EasyEDA.

https://docs.easyeda.com/en/PCB/Route/index.html
Edit:

EasyEDA can import Kicad, Altium and EAGLE files. I do not know in detail how good the import function is. I had good results with DXF Files...

https://docs.easyeda.com/en/Import/Import-Eagle/index.html

Sorry for the off-topic but using the search function for design software came up with this post and I downloaded it.

Never done this before, and I am actually drawing a schematic with the right IC's in the right packages within a minute or so.

It seems to live up to it's name, I think I'll stick with this one.

 

[C12VR]

How close is the Gates 5215 to the Langevin 5116? It looks like the same idea, two 5879s and a negative feedback circuit. The key difference I can gloss is the implementation of this negative feedback; the Gates does it the conventional way, while the Langevin uses a tertiary winding on the OPT. Is the Gates significantly higher or lower in distortion?

 

[rackmonkey]

I can’t speak to distortion differences being attributable to the global feedback or lack thereof, mainly because it’s not a practical concern. The more impactful difference is in the different iron used in these units, which have definite sonic differences, signficant enough to swamp circuit related factors.

The 5116(A, not 5116B) is the same basic circuit as the Collins 356A and the GE 4BA-1-F. In my experience they all live in the same overall sonic category that EMRR has described as “60s clean”. But they do sound different, and i attribute the differences I hear to the iron - not whether there’s global feedback used or not. I don’t own any 5116A units, but i have multiples of the 5215, 356A and BA-1-F. Even amongst units of the same manufacturer/model, having UTC iron vs ADC or Thordarson sounds different and even measures differently (the manufacturers sourced equivalent parts from different suppliers at various times during the manufacturing life of each product. This doesn’t apply to Langevin though, who made their own transformers). The little ADC or Triad “ouncer” style transformers in the 5215 have their own sound as well, and in my experience differ between ADC and Triad sourced parts.

In addition, the little ouncer-sized transformers in the 5215 have between half and 2/3 the headroom of the larger transformers found in the others. In use, depending on pad and mic used, you could end up with some distortion with a 5215 that you don’t get on a 5116A, regardless of what you measure with a test setup. Between that and the sonic differences i described above, any small distortion difference you might be able to isolate to the feedback design on the bench just doesn’t matter once the iron differences between and within models comes into the equation.

 

[thomasdf]

For some reason I had missed this thread. Some super interesting read ! I have 6 5215 preamp, 4 are originals and 2 are built from the ground up with orig transformers. I used them to track a jazz album and was very pleased with the result, but I have quite some hum from the mains / PSU transformer in the same rack enclosure. My next step will be to build an external PSU and some info here might be super handy when the time comes for that.
Thanks !

 

[thomasdf]

Is it a good idea to add a switch to cut the negative feedback in order to get more gain, or will it sound like a fuzz box ? I am asking before I start cutting traces on a 60 years old beautiful PCB haha
Edit : I could also unsolder C4 .. heh