FREQ500 KIT Build Thread

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FREQ500 KIT Build Thread

Post by Joe Malone »

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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.
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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.
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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

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Joe :-)
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Blackdawg
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Re: FREQ500 KIT Build Thread

Post by Blackdawg »

Hey Joe,

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

Thanks!

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Blackdawg wrote: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.
Joe :-)
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Blackdawg
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Re: FREQ500 KIT Build Thread

Post by Blackdawg »

Joe Malone wrote:
Blackdawg wrote: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?

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Blackdawg wrote:
Joe Malone wrote:
Blackdawg wrote: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.
Joe :-)
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Claudio
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Re: FREQ500 KIT Build Thread

Post by 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

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Claudio wrote: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.
Joe :-)
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Claudio
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Re: FREQ500 KIT Build Thread

Post by 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
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Re: FREQ500 KIT Build Thread

Post by 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!

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Iamnotacowboy wrote:
Sat Oct 17, 2020 11:53 am
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
Joe :-)
JLM Audio
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Aesacus
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Re: FREQ500 KIT Build Thread

Post by Aesacus »

I've just built two of these and it was a fun, straight forward build. From what I've heard so far, they sound great too!
But, I've run into a few issues and could use some advice...

At first, the first unit passed audio and was fully functioning except I had an led that was disoriented so I pulled it from the rack and reoriented it correctly.

The second unit's mid and low filters were both not working, and the low filter's boost/cut led didn't change from green to red, and it's orange led wasn't functioning. I inspected all of the components to be sure they were in their correct locations and double checked polarity on everything: All good. I went ahead reheated some solder points too just in case.

On second try, same issues with the bad second unit. No low, no mid, and the led problems were still there. This time I noticed that the audio stuttered a bit as I played with the hpf switch as well.
After I pulled it out from the rack the second time, I noticed that both 4.7Ω resistors were discolored. Hmmm...

Then, as I tried the first unit for its second try, its lower 4.7Ω resistors immediately blew in a brief, smelly blaze so I promptly powered down and removed it.

Any input on where to continue diagnosing these issues?
I suppose I'll also need to source some new resistors.

Anyway, not a problem, just a project. I can't wait to get these up and running. All thoughts and advice welcome.
Cheers!

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Aesacus wrote:
Wed Oct 13, 2021 1:21 pm
I've just built two of these and it was a fun, straight forward build. From what I've heard so far, they sound great too!
But, I've run into a few issues and could use some advice...

At first, the first unit passed audio and was fully functioning except I had an led that was disoriented so I pulled it from the rack and reoriented it correctly.

The second unit's mid and low filters were both not working, and the low filter's boost/cut led didn't change from green to red, and it's orange led wasn't functioning. I inspected all of the components to be sure they were in their correct locations and double checked polarity on everything: All good. I went ahead reheated some solder points too just in case.

On second try, same issues with the bad second unit. No low, no mid, and the led problems were still there. This time I noticed that the audio stuttered a bit as I played with the hpf switch as well.
After I pulled it out from the rack the second time, I noticed that both 4.7Ω resistors were discolored. Hmmm...

Then, as I tried the first unit for its second try, its lower 4.7Ω resistors immediately blew in a brief, smelly blaze so I promptly powered down and removed it.

Any input on where to continue diagnosing these issues?
I suppose I'll also need to source some new resistors.

Anyway, not a problem, just a project. I can't wait to get these up and running. All thoughts and advice welcome.
Cheers!
HI
Sorry notifications haven't been coming to my email so been missing some new posts.
The main problem would be leds around the HPF and EQ in out. Make sure they do not touch the switch metalwork or they will be short to 0v.
If you cannot find it send me some photos of the build for me to check over for you,
Joe :-)
JLM Audio
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Kvasir992
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Re: FREQ500 KIT Build Thread

Post by Kvasir992 »

Finished building my pair of FREQ500 a few days ago, and everything works as it should.
Thank you Joe for packing this amazing circuit in such a small space! I don't think I have seen this much equalizing power and functionality in one 500 unit elsewhere. Tried them on some solo grand piano and acoustic trio material, and the eq's can go from very subtle to extreme very effortlessly, without sounding pushed. I can see myself using this as my main eq for anything requiring maximum precision.

It has a sound colour of its own though, which I would like to work on a bit with my arsenal of discrete opamps. There was no socket pins for the audio path 2520 DOA footprints in the package I received, so I'm wondering if they were left out by accident..?
Also I would like to ask for advice on which ones of the 4 opamps has most audible effect? Should I focus my efforts on nr. 4 (the output stage?)...?

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Re: FREQ500 KIT Build Thread

Post by Joe Malone »

Kvasir992 wrote:
Mon Jul 18, 2022 9:19 pm
Finished building my pair of FREQ500 a few days ago, and everything works as it should.
Thank you Joe for packing this amazing circuit in such a small space! I don't think I have seen this much equalizing power and functionality in one 500 unit elsewhere. Tried them on some solo grand piano and acoustic trio material, and the eq's can go from very subtle to extreme very effortlessly, without sounding pushed. I can see myself using this as my main eq for anything requiring maximum precision.

It has a sound colour of its own though, which I would like to work on a bit with my arsenal of discrete opamps. There was no socket pins for the audio path 2520 DOA footprints in the package I received, so I'm wondering if they were left out by accident..?
Also I would like to ask for advice on which ones of the 4 opamps has most audible effect? Should I focus my efforts on nr. 4 (the output stage?)...?
The FREQ500 audio pcb has the option for 4 x DOA and sockets but it is not part of the standard kit. We always recommend building the FREQ500 standard and then if you want to you can change to DOA audio path as we have the sockets and opamps available on the webshop.

The thing to remember is a lot of DOA cannot swing anywhere near full rail to rail so will actually drop the headroom of the EQ compared to a DIP8 opamp which will get to within a volt or 2 of the power rails. The FREQ500 can output +28dBu so losing a bit of headroom is probably not a big problem.

If you want faster harder then our 990A+ opamp or HybridSMD or Twenty 5 Twenty. If you want more colour in a warm and silky way then our JLM99v will work or more overall THD then FLICKSMD.
Joe :-)
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Everett
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Re: FREQ500 KIT Build Thread

Post by Everett »

Hello Joe, I just completed my first of two Audio Path PCBs. Per the build guide, I went to test it, inserted the two jumpers, connected it to an extender...and when I powered on my rack, the two 4R7 resistors instantly fried. Any troubleshooting tips?

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