[Hairball Audio]

Got it. Resoldered all the points in the DI section and it working great!

Thanks for the help mike! looking forward to building some more Hairball stuff!

Nice!

[rwrwrw]

Hi,

I recently built a Gold preamp and the DI seems to not be working properly. It sounds quiet and super distorted. I've tried it with the gain all the way down & the output up, the pad in, different instruments and cables (I checked all these too and they are working fine) but no luck. XLR In and out work great. I resoldered some parts but that did not help. I've attached a photo and can include more if needed. Any help is greatly appreciated!

[Hairball Audio]

It would have to be something in the DI Buffer box on the PCB.  Check all solder joints and values.

Mike

[rwrwrw]

I checked all the parts and everything seems to be in the right place as far as I can tell. I re-soldered all the parts in the DI buffer box  but I'm still having the same issue. Seems like the DI output is even lower in volume and crispier sounding. XLR I/O still works fine. Maybe theres something wrong with the LME49720?

Any points I should test?

I attached a new photo.

[Hairball Audio]

I checked all the parts and everything seems to be in the right place as far as I can tell. I re-soldered all the parts in the DI buffer box  but I'm still having the same issue. Seems like the DI output is even lower in volume and crispier sounding. XLR I/O still works fine. Maybe theres something wrong with the LME49720?

Any points I should test?

I attached a new photo.

Could be.  They are sensitive to heat.  You could check the AC signal at the input pin VS the output pin (see datasheet). They should be the same(ish).

Mike

[rwrwrw]

Which pins do you mean? On one of the transformers? Also I could not find what data sheet you are referring to... thanks again for your patience haha

[Hairball Audio]

Which pins do you mean? On one of the transformers? Also I could not find what data sheet you are referring to... thanks again for your patience haha

On the DI Op-amp.  Google "LME49720 Datasheet".

Mike

[ssttoo]

One of my Coppers stopped working today. I had with an AKG C1000 as a room mic, it was a little quiet so  turned up the gain and the output and recorded again, only this time the track was silent. I tried moving to different slots in the 500 chassis. My other Copper still works fine so I do the exact same thing with the two of them and the 1st one doesn't seem to do anything. Neither the DI, nor the mic input seem to work.

The phantom power is the only thing that works fine - it lights up the AKG414

Any pointers to start debugging are welcome!

[Hairball Audio]

One of my Coppers stopped working today. I had with an AKG C1000 as a room mic, it was a little quiet so  turned up the gain and the output and recorded again, only this time the track was silent. I tried moving to different slots in the 500 chassis. My other Copper still works fine so I do the exact same thing with the two of them and the 1st one doesn't seem to do anything. Neither the DI, nor the mic input seem to work.

The phantom power is the only thing that works fine - it lights up the AKG414

Any pointers to start debugging are welcome!

Swap the op-amps.  Maybe a bad op-amp?

Mike

[ssttoo]

> Swap the op-amps.  Maybe a bad op-amp?

Ha, why didn't I think of that! Thanks Mike! Unfortunately that didn't fix it I swapped the op-amps and the unit that works still works, and the one that doesn't still doesn't.

Two other things I noticed about the non-working unit:
1) turning up the gain increases the noise a little
2) plugging into the DI and touching the cable has an ever-so-slight buzz

[Hairball Audio]

> Swap the op-amps.  Maybe a bad op-amp?

Ha, why didn't I think of that! Thanks Mike! Unfortunately that didn't fix it I swapped the op-amps and the unit that works still works, and the one that doesn't still doesn't.

Two other things I noticed about the non-working unit:
1) turning up the gain increases the noise a little
2) plugging into the DI and touching the cable has an ever-so-slight buzz

Check all of your component placement.
Solder Joints.

We also have a killer repair deal on those:
http://www.hairballaudio.com/build-support-services

Mike

[ssttoo]

Thanks, I'll try reflowing all joints. Though it was working while testing, just failed on the first real-life usage. Do you have any pointers as to identifying faulty components?

[Hairball Audio]

Thanks, I'll try reflowing all joints. Though it was working while testing, just failed on the first real-life usage. Do you have any pointers as to identifying faulty components?

It's difficult to test a 500 series unit without an extender jig. If you can, insert it without op-amp and test the DC V between the op-amp pins:

0V/GND and +16
0V/GND and - 16

See if you're even getting DC V to the op-amp pins.

Mike

[Bendo]

Hi all.

My kit arrived with only one component missing. Since I live pretty far away, (Southern most tip of africa) and don't necessarily want to wait for a single replacement cap to be sent, I'd like to know if I can substitute the part locally without compromising the preamp.

The missing component is C500 which has a value of 680pf and is part of the filter network at the input stage.

Is the type of capacitor critical here, or will I be able to get away with an easily available substitute?

Thanks in advance.

[Hairball Audio]

Hi all.

My kit arrived with only one component missing. Since I live pretty far away, (Southern most tip of africa) and don't necessarily want to wait for a single replacement cap to be sent, I'd like to know if I can substitute the part locally without compromising the preamp.

The missing component is C500 which has a value of 680pf and is part of the filter network at the input stage.

Is the type of capacitor critical here, or will I be able to get away with an easily available substitute?

Thanks in advance.

Hi,

Yes any ceramic cap +/- 100pF will be just fine.

Mike

[Bendo]

Thanks Mike.

Completed the build, and all works great except the DI input.

Reading above, seems another builder had a similar problem. (DI sounds very distorted and very low in volume) I've tried re-flow, and can confirm all components are placed correctly with the right values. Any advice on how to troubleshoot?

[Bendo]

Update - I've tried everything that I can think of - still no improvement.

I've swapped out the IC (was very difficult to remove from the board - gosh!) I noticed that the IC is getting quite warm. I assume this means there is a power issue? I'm not 100% sure - buy I think the relay was getting a little warm too.

The XLR input works flawlessly. Dead quiet and super clean. No issues anywhere else except for the DI input. Relay is switching when I plug the DI in.

Any advice? I can't read any voltages since I have no extender jig.

Thanks.

[Maggot Brain]

Hey all. Just about to wrap up my 1st copper build. Just a quick question....

When I installed the TO220 style transistors, I pushed them until they stopped and soldered them assuming that they had gotten as close to the PCB as they could. Anyway, after looking at pictures, I can see that they are able to be flush to the PCB.

Just wondering if it matters that they stick up higher before I de-solder them, because that is a pain haha.

thanks

[Hairball Audio]

Hey all. Just about to wrap up my 1st copper build. Just a quick question....

When I installed the TO220 style transistors, I pushed them until they stopped and soldered them assuming that they had gotten as close to the PCB as they could. Anyway, after looking at pictures, I can see that they are able to be flush to the PCB.

Just wondering if it matters that they stick up higher before I de-solder them, because that is a pain haha.

thanks

You shouldn't mount those flush. There should be a little lead showing.

[Maggot Brain]

You shouldn't mount those flush. There should be a little lead showing.

Ok cool. There's probably a lot of lead showing, comparative to how you would build it, but it's soldered properly and all that. I tried to de-solder them to seat them a little lower and felt like I was going to damage the components from too much heat, so I stopped. I'll just leave em where they are for now.

Thanks!