Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #20 on: August 24, 2014, 11:04:14 PM »
Hi guys...

Just finished my first of two Golds.

After a first power-on, I believe I have a problem:
I am too getting extremely weak signal out of a SM58 with both pots cranked up... And the DI signal is so weak, I am barely getting a signal from my bass with passive pickups. With both pots cranked up I can get a "decent" level, but it is highly distorted and thin.

I am also measuring a slight DC offset.

Where should I start looking?

Thanks!

You used the build guide correct?

Building the second could rule out any component issues, though that would be rare.
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Re: [BUILD] Hairball Audio - Elements
« Reply #21 on: August 25, 2014, 01:42:06 PM »
You used the build guide correct?

Building the second could rule out any component issues, though that would be rare.

To the T...

Will update you on the second build!

Thanks!

Re: [BUILD] Hairball Audio - Elements
« Reply #22 on: August 27, 2014, 01:36:16 PM »
May I suggest that this image from your build guide is wrong?



According to Jensen's website (http://www.jensen-transformers.com/datashts/11dmcf.pdf), primary should be BROWN-RED and secondary should be ORANGE-YELLOW...

Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #23 on: August 27, 2014, 02:03:09 PM »
Yikes.  May appear so.  I'll be back at the shop in an hour and post back.
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Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #24 on: August 27, 2014, 03:12:28 PM »
You are correct.  Red and Orange need to be swapped.

However this actually has little effect on the audio other then some super HF rolloff.  Basically it's like having an inductor on the output rather than a transformer.  Does not change the gain or distortion.

The Mic Pre itself has slightly more 63dB of gain which is normal. (60-65dB).  However, if you have the variable input, most of this gain is near the end of the pot and it's very sensitive.  That is why we have the Grayhill upgrade do get a better sweep.  The variable is meant to be a budget option.

That said it should sound great.  It's hard to know if your having an issue or just not excited about the variable pot performance.

Did you build the second one yet?

Mike
Hairball Audio, LLC
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Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #25 on: August 27, 2014, 05:11:07 PM »
Build guide updated and everyone has been notified.

Thanks for the catch!

Looking back at your symptoms, it definitely seems like something is not right at all.  If you like post some pictures.  Worst case you can send it in and we'll look at it.

Keep me posted, we'll get you up and running!

Mike
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
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Re: [BUILD] Hairball Audio - Elements
« Reply #26 on: August 27, 2014, 06:32:21 PM »
Good! Thanks for your quick replies.

Upon swapping wires, gain was somewhat better on a SM-58, but most importantly DC offset disappeared from the output.

Still no joy on the DI input with my bass though. The relay seems to work, as the XLR input is effectively muted when a jack is inserted on the front panel. But I can barely get any signal and when I do, it's still thin and distorted.

I also discovered I had confused C104 and C105 for C303 and C601 so I swapped these but it didn't fix my DI problem.

Waiting for missing parts in order to build Gold #2.

Cheers!

Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #27 on: August 27, 2014, 06:38:52 PM »
Good! Thanks for your quick replies.

Upon swapping wires, gain was somewhat better on a SM-58, but most importantly DC offset disappeared from the output.

Still no joy on the DI input with my bass though. The relay seems to work, as the XLR input is effectively muted when a jack is inserted on the front panel. But I can barely get any signal and when I do, it's still thin and distorted.

I also discovered I had confused C104 and C105 for C303 and C601 so I swapped these but it didn't fix my DI problem.

Waiting for missing parts in order to build Gold #2.

Cheers!

Cool.  Keep me posted.  Build up number two and see what happens.

If you like post some images.  Sometime I can spot things but this build is mostly straight forward.  Gold has lots of components that are shorted/jumpered make sure you have all those.

It should not sound thin.

Mike
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
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Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #28 on: August 27, 2014, 06:41:47 PM »
Good! Thanks for your quick replies.

Upon swapping wires, gain was somewhat better on a SM-58, but most importantly DC offset disappeared from the output.

Still no joy on the DI input with my bass though. The relay seems to work, as the XLR input is effectively muted when a jack is inserted on the front panel. But I can barely get any signal and when I do, it's still thin and distorted.

I also discovered I had confused C104 and C105 for C303 and C601 so I swapped these but it didn't fix my DI problem.

Waiting for missing parts in order to build Gold #2.

Cheers!
Also have a good look at the R Values in the DI section.
Hairball Audio, LLC
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https://hairballaudio.com

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Re: [BUILD] Hairball Audio - Elements
« Reply #29 on: August 28, 2014, 03:32:10 PM »
Here are two pictures I just took...

Full: http://i.imgur.com/i88NC2E.jpg
DI section: http://i.imgur.com/I1Fc351.jpg

Thanks for your time!
P


Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #30 on: August 28, 2014, 05:59:54 PM »
Looks like a good clean build!

Maybe a defective part.

Have you double checked all our cabling/patchbay to make sure something isn't out of polarity or unbalanced?

You could always send it in if you like, we're happy to look over weird acting builds.

Mike
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio

Greenote

Re: [BUILD] Hairball Audio - Elements
« Reply #31 on: August 28, 2014, 07:00:28 PM »
My first build was a copper. It sounds good, I just finished the stepped pot board, but haven't put it in yet.

Second build is a Bronze. I used the stepped pot on this one. I got no sound and realized I'd forgot the shorting resistor in R606. It's now working (sorta) however it' very distorted at most gain stages and cuts in and out. I've looked over my traces and parts placements.

I'm suspecting something amiss in the Input stage or the Opamp. I have several types of 2520 DOAs. Can I pop in a J99 from my Lola or the working DOA from the Copper?

Any other ideas.

Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #32 on: August 28, 2014, 07:04:57 PM »
My first build was a copper. It sounds good, I just finished the stepped pot board, but haven't put it in yet.

Second build is a Bronze. I used the stepped pot on this one. I got no sound and realized I'd forgot the shorting resistor in R606. It's now working (sorta) however it' very distorted at most gain stages and cuts in and out. I've looked over my traces and parts placements.

I'm suspecting something amiss in the Input stage or the Opamp. I have several types of 2520 DOAs. Can I pop in a J99 from my Lola or the working DOA from the Copper?

Any other ideas.

You could try another DOA but we do test them before we ship.

Make sure the two silver can-type (TO39) output transistors on the op amp are not touching.  You can use your fingers and pry them apart a little.

Trying another opamp would help to figure out if it's the op-amp or main PCB.

Report back!
« Last Edit: August 28, 2014, 07:26:03 PM by Hairball Audio »
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Re: [BUILD] Hairball Audio - Elements
« Reply #33 on: August 28, 2014, 07:37:13 PM »
Looks like a good clean build!

Maybe a defective part.

Have you double checked all our cabling/patchbay to make sure something isn't out of polarity or unbalanced?

You could always send it in if you like, we're happy to look over weird acting builds.

Mike

Thanks Mike... gain issues with the mic input have been sorted out as far as I'm concerned... I'm just not used to cranking volume controls so much. I might look into upgrading the pots to Grayhills, eventually.

The DI situation however, isn't solved. Tried different instruments and cables without success. Although "some" signal passes through, it is still highly distorted. It's even more obvious with a signal from a higher-gain source such as music playing back from my iPhone. Just nasty distorted.

I'll hold on to shipping it back until I get the other one finished and tested... plus, I really enjoy troubleshooting stuff ;)

We'll move on from there.
P

Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #34 on: August 28, 2014, 07:48:54 PM »
Looks like a good clean build!

Maybe a defective part.

Have you double checked all our cabling/patchbay to make sure something isn't out of polarity or unbalanced?

You could always send it in if you like, we're happy to look over weird acting builds.

Mike

Thanks Mike... gain issues with the mic input have been sorted out as far as I'm concerned... I'm just not used to cranking volume controls so much. I might look into upgrading the pots to Grayhills, eventually.

The DI situation however, isn't solved. Tried different instruments and cables without success. Although "some" signal passes through, it is still highly distorted. It's even more obvious with a signal from a higher-gain source such as music playing back from my iPhone. Just nasty distorted.

I'll hold on to shipping it back until I get the other one finished and tested... plus, I really enjoy troubleshooting stuff ;)

We'll move on from there.
P

Ya we actually made the Grayhill the default gain option this morning.

Sounds like a funky part.  We'll gladly look at it for you.

Keep me posted!
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
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Greenote

Re: [BUILD] Hairball Audio - Elements
« Reply #35 on: August 29, 2014, 04:11:20 PM »
Bronze: I used the DOA from the copper in my Bronze build. It's way less distorted, but the sound is cutting in an out.

I was looking at Fern's Jensen OTP issue, so I thought I'd double check the EA wiring an see if a similar mistake was made.

The schem appears on your site. http://www.hairballaudio.com/docs/B11148/b11148.pdf
This is for the B frame package I assume but the wiring should be the same.

This doesn't seem to match up to the picture in the build guide for the Bronze Tranformer.

I won't assume the Rain Dog is bad until I sort out the OTP wiring.

Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #36 on: August 29, 2014, 04:32:57 PM »
The wiring looks right (on my phone now). Both windings in parallel.  I'll double check when I get back to my computer but it appears right.

Should not be cutting out at all.  Something is up.  Post a picture?  Send it in for a check if you like.

Keep me posted!

Mike
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

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Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #37 on: August 29, 2014, 04:36:04 PM »
If it's cutting out you may want to try re flowing any suspect solder joints on the main PCB.  Cold joint could cause that.  Make sure the output transistors in the output stage are not swapped or backwards.  The Q600 and 601.
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Hairball Audio

Re: [BUILD] Hairball Audio - Elements
« Reply #38 on: August 29, 2014, 08:20:48 PM »
That wiring is definitely right.

With distortion and cutting out I would suspect:

1:  Op-amp output transistors (silver cans) are touching.  Though we confirm they are not when they ship.  Make sure they didn't get pushed back together in shipping on installation.

2. Output transistors Q600/601 are reversed or installed backwards.

3. Cold solder joint.

4. Damaged semi conductor.

Mike

Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
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Greenote

Re: [BUILD] Hairball Audio - Elements
« Reply #39 on: August 29, 2014, 11:56:05 PM »
Thanks!

1. No-touchey Confirmed. used 512 DOA, distortion gone
2. I have these correct.
3. I've re-hit most the joints.
4. Hmm.

I'll re-heat remaining pads. then likely post a pic if I'm still having issues.  I have a few different ic's, just hoping not to have to undo a chip as I don't have desoldering gun.

BTW, This kit was missing 200k resistors (had 100ks) Also the ceramic 100pf paired with R503 was the wrong value. I had these in my cache.

Stepped Gain is the way to go!
Cheers