FREQ500 KIT Build Thread

[Joe Malone]

Build Thread is still under construction. Please ask any questions you have on this thread so we can add the detail needed.

Use FREQ500 audio path build map link below to place and tick off all parts.

FREQ500 AUDIO PATH KIT build map
http://www.jlmaudio.com/builds/maps/freq500audiomap.html

Photos of finished FREQ500 Audio path pcb.



FREQ500 Audio path pcb can be tested by itself by fitting a jumper shunt to pin 5 & 6 in the centre of the 10 pin header.
Then fitting a second jumper to TP1 will switch the pcb from bypass to audio path which should give the same level audio output.




Notes and Errata
5 of the 150k have been changed to 330k to balance the green led brightness better to the red led brightness.
Map shows which 5 of 150k resistors are now 330k.
Lo filter pcb need one white wire soldered under neath the pcb to link ground plane on the pcb.

Use FREQ500 filter path build map link below to place and tick off all parts that can be fitted before following the photos below.

FREQ500 FILTER build map
http://www.jlmaudio.com/builds/maps/freq500eqmap.html

[Blackdawg]

Hey Joe,

Noticed there is foot prints for 2520 DOA for this as well. How does that all work?

Thanks!

[Joe Malone]

Hey Joe,

Noticed there is foot prints for 2520 DOA for this as well. How does that all work?

Thanks!

Yes the main audio path for the EQ is made of 4 x opamps which can be dual DIP8 running in parallel or 4 x discrete opamps with 990 or 2520 pinouts like our JLM99v.

[Blackdawg]

Hey Joe,

Noticed there is foot prints for 2520 DOA for this as well. How does that all work?

Thanks!

Yes the main audio path for the EQ is made of 4 x opamps which can be dual DIP8 running in parallel or 4 x discrete opamps with 990 or 2520 pinouts like our JLM99v.

Awesome!

I'm assuming this means you just don't install all the parts that are there now and just put in pins and DOA's of your choice?

[Joe Malone]

Hey Joe,

Noticed there is foot prints for 2520 DOA for this as well. How does that all work?

Thanks!

Yes the main audio path for the EQ is made of 4 x opamps which can be dual DIP8 running in parallel or 4 x discrete opamps with 990 or 2520 pinouts like our JLM99v.

Awesome!

I'm assuming this means you just don't install all the parts that are there now and just put in pins and DOA's of your choice?

The PCB is built with the same parts but instead of the DIP8 sockets the 6 x 1mm socket pins per opamp are installed. Or both DIP8 & 1mm sockets can be mounted so DIP8 opamp and discrete opamps can be swapped in and out.

[Claudio]

Hey Joe,

This seems like a basic question, but do we have to cut away the +/- 24V pins from the connector when we don’t have a 51x rack? Or can the modules be inserted in a VPR rack just as well?

Regarding the op amps, would any 2520 DOA work, e.g. the Sound Skulptor SK99, the Red Dot, or the GAR2520? Could we also mix DIP8 op amps and 2520 DOAs on the same PCB? Or do they have to be all the same for any reason?

Why are there four op amps anyway? Does each frequency band have its own op amp? If so, would it make sense to have the cleaner IC op amps for the higher frequencies and maybe some GAR2520 for the lows and low mids for additional harmonic distortion?

Thanks a lot,
Claudio

[Joe Malone]

Hey Joe,

This seems like a basic question, but do we have to cut away the +/- 24V pins from the connector when we don’t have a 51x rack? Or can the modules be inserted in a VPR rack just as well?

The connector is designed with short 51X pins so it should be able to plug into any 500 rack without removing them. If the 500 backplane connectors are held in by screws then they will need to be cut off as the short pins will hit the screw head. If you are going to run on 51X rack @ +/-24v then the 4 opamps on rear audio path pcb need to be +/-24v opamps and 2 regs need to be fitted to drop the voltage to +/-18v for the filter pcbs.

Regarding the op amps, would any 2520 DOA work, e.g. the Sound Skulptor SK99, the Red Dot, or the GAR2520? Could we also mix DIP8 op amps and 2520 DOAs on the same PCB? Or do they have to be all the same for any reason?

Most DOA should work on the back audio path pcb as they are all running at unity gain.

Why are there four op amps anyway? Does each frequency band have its own op amp? If so, would it make sense to have the cleaner IC op amps for the higher frequencies and maybe some GAR2520 for the lows and low mids for additional harmonic distortion?

The 1st opamp is unity balanced to unbalanced input and 2nd and 3rd opamps are unity invert stages for +/-summing of the EQ side filters back into the audio path. 3rd opamp is also +output driver and 4th opamp is -output driver. No EQ filters are inline with the audio. They all run sidechain like a compressor. Only the 4 opamps on the back edge pcb are the audio path.

[Claudio]

Thanks for your reply, Joe! I have a Trident Deca-Dent rack, so yes, the screws of the connectors would get in the way of the 51x pins. I will cut them off then.

[Iamnotacowboy]

Hopefully this is the right place to post this. I have two FREQ500 kits that I built that have some issues. I’m not a pro, but I wouldn’t say I’m inexperienced. Between mics, compressors, EQs, mic pres, amps, pedals, and various studio tools, I’ve built well over 100 projects. Alright. Enough preamble. Sooo...

Unit One
Blue light stays on whether the EQ is engaged or not. (This could be normal operation, but I don’t believe it is)
Lo Mid is not functional.
Hi Mid passes signal, but the frequencies aren’t correct. There are also spots within the pot range that make signal intermittent and distorted.
High band only passes audio with frequency knob pulled.

Unit Two
Blue light stays on whether the EQ is engaged or not.
No audio signal passes.
If you pull the boost/cut knobs, there’s an audible pop on every band.

UPDATE!!
Unit Two
Got signal passing and all bands are active. Now the only issue is that the EQ is always ON. The blue light is still always on, despite EQ switch being in or out.

Alrighty. That about sums it up. The plans and layout of these devices are great, and I can’t wait to get them all working. The bands that do work sound great. So any tips or help is greatly appreciated. I looked over all of the soldering and patched up some spots here and there. That is the extent of my knowledge. Thank you!

[Joe Malone]

Hopefully this is the right place to post this. I have two FREQ500 kits that I built that have some issues. I’m not a pro, but I wouldn’t say I’m inexperienced. Between mics, compressors, EQs, mic pres, amps, pedals, and various studio tools, I’ve built well over 100 projects. Alright. Enough preamble. Sooo...

Unit One
Blue light stays on whether the EQ is engaged or not. (This could be normal operation, but I don’t believe it is)
Lo Mid is not functional.
Hi Mid passes signal, but the frequencies aren’t correct. There are also spots within the pot range that make signal intermittent and distorted.
High band only passes audio with frequency knob pulled.

Unit Two
Blue light stays on whether the EQ is engaged or not.
No audio signal passes.
If you pull the boost/cut knobs, there’s an audible pop on every band.

UPDATE!!
Unit Two
Got signal passing and all bands are active. Now the only issue is that the EQ is always ON. The blue light is still always on, despite EQ switch being in or out.

Alrighty. That about sums it up. The plans and layout of these devices are great, and I can’t wait to get them all working. The bands that do work sound great. So any tips or help is greatly appreciated. I looked over all of the soldering and patched up some spots here and there. That is the extent of my knowledge. Thank you!

The Blue light should turn off but will stay on it you haven't removed the TP1 test jumper shunt on the main audio pcb as this overrides the switch for testing. Is the jumper removed?

First most common problem we see are related to soldering usually being too much solder and blobs shorting to other solder pads or ground plane on the pcb.

Second most common is soldering that hasn't flowed onto the pcb so solder blub is not actually soldered to the pcb.

Third most common is ribbon cables with IDC connectors not fully pressed on onto the cable. Use a normal bench vice to press IDC connectors on to cable.

Let me know if you have any more questions

If anyone gets stuck and cannot fix kit you can use the repair form on the JLM audio website at the link below to send it to us for repair.

https://www.jlmaudio.com/shop/repair-form.html