[BUILD] FET/500 Official Support Thread

[EmoRiot]

Well... all was going well until...

I put together the Elements Copper pre last week and it was so fun that I ordered the FET/500 Rev A to do this week.

I started that a yesterday and today I got to the input transformer. The instructions said a plastic spacer would be in the box for the input transformer. When I didn't see it, I feared I might've lost it while taking initial stock of the parts. I set about fashioning my own spacer by cutting up some plastic from the T-pad's clear plastic shipping container. I mounted the transformer and then the next step is to mount the output transformer. And inside the baggie for the mounting hardware I find... oops... the plastic spacer!

Now at this point I probably should've just shrugged and though "oh well a spacer is a spacer." But instead I contemplated if my plastic macguyver version was inferior and went about desoldering the transformer.

That wasn't as easy as I hoped... 8 pins... lots of back and forth heating of the contacts, using a wick to soak up solder, and wiggling to slowly free the transformer from it's multi-soldered connections on the PCB.

I got it out with my PCB looking a bit worse for wear from flux, I think. I put the correct spacer on, reinserted, and resoldered.

Now... here's the concern. The transformer can be wiggled on the PCB. The pins on the underneath side don't seem to wiggle when I feel them, but the metal can on the top side definitely wiggles. That's got to be a problem, right? Something is up. Cold solder joints that have broken or has the transformer can itself come apart?

 

[EmoRiot]

The transformer can be wiggled on the PCB. The pins on the underneath side don't seem to wiggle when I feel them, but the metal can on the top side definitely wiggles. That's got to be a problem, right? Something is up. Cold solder joints that have broken or has the transformer can itself come apart?

Looking at a pic of the underneath side, I'm wondering if the wiggle I feel is just that gap visible between the hole of the outer housing and the inner iron. From this pic, it looks like the can would wiggle about as much as I'm feeling with it in place.

Maybe I'm okay?

 

[EmoRiot]

Maybe I'm okay?

I'll just update my two messages above for anyone else that comes through their build and feels the same wiggle. Everything turned out fine. I continued with the build, calibrated, fired it up, and it works beautifully. Hooray.

 

[Echo North]

I'll just update my two messages above for anyone else that comes through their build and feels the same wiggle. Everything turned out fine. I continued with the build, calibrated, fired it up, and it works beautifully. Hooray.

Ya the pins have a little "play".

Mike

 

[stephan.gueguen]

With all this quarantine time, I finally have some free time to look into an old issue. I built a FET500 rev D several months back and all went well, however there always has seemed to be an issue with unpleasant distortion at high levels of GR. Could this possible be an issue with the signal preamp linearity? At just a few dB of gain reduction with slow attack times, the ‘distortion’ or clipping quality isn’t heard, but when smashed it really becomes unpleasant. Is this normal or is there something I should check on the PCB?

 

[aaronmc]

Hi! I have a question about biasing my FET/500 Rev D units. I built 2 stereo matched units and went through the biasing procedure. I ran into a minor issue with step 2 on two of my units - the -10db light lights up at .384v instead of .388v.  I could not adjust V2 any further to get closer to .388. I figured .004v was close enough so I continued through the rest of the calibration process without any additional problems. This might have to do with the accuracy of my DMM reading a 1k signal.. not sure.

After completing the calibration, when I connect the units using the link cable (sending the same 1khz sine @ 775vac), one unit's meter (both VU and GR) seems to be off by 1db. This is happening on both stereo matched pairs. When I place the unit in bypass mode, one meter on each of the pairs shows -1db on the GR meter. When I remove the link cable the GR meter goes back to 0db. When not linked, the GR and VU meters on all units seem to track pretty closely with minor variances in GR. Any ideas what might be causing this?

 

[Echo North]

With all this quarantine time, I finally have some free time to look into an old issue. I built a FET500 rev D several months back and all went well, however there always has seemed to be an issue with unpleasant distortion at high levels of GR. Could this possible be an issue with the signal preamp linearity? At just a few dB of gain reduction with slow attack times, the ‘distortion’ or clipping quality isn’t heard, but when smashed it really becomes unpleasant. Is this normal or is there something I should check on the PCB?

Hard to say without looking/analyzing it, but yes at some point the GR FET distorts.  So if you "smash" it, it's going to distort.  You can try the input mod, that might help.

https://www.hairballaudio.com/fet-compressor-input-mod

Mike

 

[Echo North]

Hi! I have a question about biasing my FET/500 Rev D units. I built 2 stereo matched units and went through the biasing procedure. I ran into a minor issue with step 2 on two of my units - the -10db light lights up at .384v instead of .388v.  I could not adjust V2 any further to get closer to .388. I figured .004v was close enough so I continued through the rest of the calibration process without any additional problems. This might have to do with the accuracy of my DMM reading a 1k signal.. not sure.

After completing the calibration, when I connect the units using the link cable (sending the same 1khz sine @ 775vac), one unit's meter (both VU and GR) seems to be off by 1db. This is happening on both stereo matched pairs. When I place the unit in bypass mode, one meter on each of the pairs shows -1db on the GR meter. When I remove the link cable the GR meter goes back to 0db. When not linked, the GR and VU meters on all units seem to track pretty closely with minor variances in GR. Any ideas what might be causing this?

Not totally weird.  You could try the re-calibrating the QBias, but probably just some component tolerances stacking.

 

[deep_transmissions]

This community and site are so helpful. I built a Hairball 1176 Rev D that my wife got me for my birthday. Took me almost three weeks (going really slow) but it worked perfectly audio wise. I did have to go back and open it whole calibrating a few times, at first I thought I may have heated the LEDs too high and burnt them out, but as it turns out, it's sort of an SMD soldering situation with those and I just didn't have them mounted as firmly as I had thought when soldering.

I did have to reorder 2 parts: I put the bipolar transistor in too soon and clipped the legs before realizing I needed space for the spacer for the PCB heat protection so I needed to re-order that. Also, mounted the bypass switch a little funky and had to reorder that ... it may not have been broken but I wanted a perfect build.

Overall this went really smoothly. I Need to recalibrate it now that I've been running it for a few weeks, but this thing sounds so incredible on drums that I really am having a hard time finding time to not use it. I get the feeling a lot of you are using these for actual drum recordings, for me I'm running my Jomox Alpha Base and MFB Tanzbar through it and let me tell you, an 808 kick from the Jomox into this beast is absolutely bananas.  All button mode is pretty much where I'm living and I cannot believe my ears. You can't even begin to compare this and a plugin. I have my CPAI VP28's between the drum machines and the 1176 and the 1176 is feeding into an Elysia Karacter and then an EQ pass with an Xfilter.

One thing I'd love to see on these as it seems the output runs super hot is a PAD switch. Is that something that could be added as a mod? I'd love to drive these hard and get that sweet saturation from the output transformer but not have to have an attenuation circuit after it. I guess I can build a DIYRE attenuator box, they're something like 50 bucks or so.

Any suggestions?

 

[Echo North]

This community and site are so helpful. I built a Hairball 1176 Rev D that my wife got me for my birthday. Took me almost three weeks (going really slow) but it worked perfectly audio wise. I did have to go back and open it whole calibrating a few times, at first I thought I may have heated the LEDs too high and burnt them out, but as it turns out, it's sort of an SMD soldering situation with those and I just didn't have them mounted as firmly as I had thought when soldering.

I did have to reorder 2 parts: I put the bipolar transistor in too soon and clipped the legs before realizing I needed space for the spacer for the PCB heat protection so I needed to re-order that. Also, mounted the bypass switch a little funky and had to reorder that ... it may not have been broken but I wanted a perfect build.

Overall this went really smoothly. I Need to recalibrate it now that I've been running it for a few weeks, but this thing sounds so incredible on drums that I really am having a hard time finding time to not use it. I get the feeling a lot of you are using these for actual drum recordings, for me I'm running my Jomox Alpha Base and MFB Tanzbar through it and let me tell you, an 808 kick from the Jomox into this beast is absolutely bananas.  All button mode is pretty much where I'm living and I cannot believe my ears. You can't even begin to compare this and a plugin. I have my CPAI VP28's between the drum machines and the 1176 and the 1176 is feeding into an Elysia Karacter and then an EQ pass with an Xfilter.

One thing I'd love to see on these as it seems the output runs super hot is a PAD switch. Is that something that could be added as a mod? I'd love to drive these hard and get that sweet saturation from the output transformer but not have to have an attenuation circuit after it. I guess I can build a DIYRE attenuator box, they're something like 50 bucks or so.

Any suggestions?

Might be the input making the output super hot.  Did you see the input mod?

https://www.hairballaudio.com/fet-compressor-input-mod

 

[Blondino]

hello everyone...
I have a weird question. For some reason this year i decided to supply several components for different DIY projects and one of those is for a FET500 rev D.  Thanks to Mike I got a nice BOM  at mnats.net but I'm having an hard time figuring out some parts. Brands or equivalents, and voltage. Even if I already own a revD there are some parts where the voltage is not printed. 
Obiouvsly I'm not talking about original parts I should get directly from hairball, but general components.

Does anybody put together a BOM with manufacture or mouser parts numbers yet?
I did it for other projects, maybe we can share 
thanks

 

[loubli]

hello!

I just finished fet500 rev.A.I have a question about calibration in the step1
>Adjust the Output control so the FET/500 output reads +11 dBu (2.75 VAC)
mine's output is maximum 2.3-2.4 VAC,when fully clockwise.
so can't go to next step...there is any solution about it?
thanks!

 

[Echo North]

hello!

I just finished fet500 rev.A.I have a question about calibration in the step1
>Adjust the Output control so the FET/500 output reads +11 dBu (2.75 VAC)
mine's output is maximum 2.3-2.4 VAC,when fully clockwise.
so can't go to next step...there is any solution about it?
thanks!

I would start with the help guide:
https://help.hairballaudio.com/hc/en-us/articles/360048218173-FET-500-Troubleshooting-Guide

Mike

 

[loubli]

I would start with the help guide:
https://help.hairballaudio.com/hc/en-us/articles/360048218173-FET-500-Troubleshooting-Guide

Mike

thank you!
I checked one by one,then found problem.
mistake of putting component...careless.
now working!

 

[loubli]

hello mike!
sorry for disturbing again.
my rev.A function and calibration is fine.
but there is white noise.not much big volume,but still problem.
when turn clockwise output,it comes with volume. even GR off,nothing change.
and when touch pot without knob,there is hum a little bit.
using another mic pre by same slot,it doesn't come.

there is any idea about it?

thanks!

 

[Echo North]

hello mike!
sorry for disturbing again.
my rev.A function and calibration is fine.
but there is white noise.not much big volume,but still problem.
when turn clockwise output,it comes with volume. even GR off,nothing change.
and when touch pot without knob,there is hum a little bit.
using another mic pre by same slot,it doesn't come.

there is any idea about it?

thanks!

You need the knob to prevent hum.

You're going to hear the noise floor of the unit if you tun it up loud enough.

Mike

 

[FarisElek]

Built the Fet/500 today. I really had trouble with the LED's because my lead cutters are dull and I ended up ripping a couple off the pcb trying to cut  them after soldering  :-[

Also, my bypass button does nothing it seems. No level change or loss of compression.


Besides that it went great. Loved the BOM. So easy to follow. The Rev A seems to have a very touchy input. I noticed there is a mod for a 6db slug, but I don't have a 100R resistor on me.  I'll probably end up doing it eventually.

First thing I noticed when I loaded it up is that at moderate levels of compression it's actually quite smooth and transparent. A lot more so than people seem to say on the forums. Some folks make Rev A sound like it adds too much character even as reasonable levels.

Love squashing with this thing. Used the "Slam" function on a kick that was ringing out a bit too much and it changed it into a fat thump.

Thank you to everyone responsible for this.

Ryan

 

[FarisElek]

If I could get any help figuring out why my true bypass doesn't work that would be rad. I've went into and messed with it quite a few times and It's functioning perfectly now, including the LED's i destroyed....except for one.

The red Led for the bypass I ripped both pads off due to my insanely dull lead cutters that I've thrown in the trash because they truly made this project go bad. I believe I connected them to the right places and -- flag side to R1 and the other to one of the SW3 pins that have connectivity with each other. I'm getting no light and it doesn't do anything. I've followed some of the circuit and the switch has continuity all the way to the relays and D1. What could be going wrong?

 

[Echo North]

If I could get any help figuring out why my true bypass doesn't work that would be rad. I've went into and messed with it quite a few times and It's functioning perfectly now, including the LED's i destroyed....except for one.

The red Led for the bypass I ripped both pads off due to my insanely dull lead cutters that I've thrown in the trash because they truly made this project go bad. I believe I connected them to the right places and -- flag side to R1 and the other to one of the SW3 pins that have connectivity with each other. I'm getting no light and it doesn't do anything. I've followed some of the circuit and the switch has continuity all the way to the relays and D1. What could be going wrong?

The LED is part of the relay circuit.  Either the LED is connected wrong, or it's dead.  Maybe try a new LED.

Mike

 

[FarisElek]

The LED is part of the relay circuit.  Either the LED is connected wrong, or it's dead.  Maybe try a new LED.

Mike

I had a feeling that might be the case. I appreciate your response. Is there a particular recommended part? I noticed the mnats BOM doesn't have a part number for the LED's. Would this one do?

https://www.mouser.com/ProductDetail/Vishay-Semiconductors/TLHR4400-AS12Z?qs=nQ9vpdMXC6AwxmxsGskxgg%3D%3D

Ryan