[BUILD] Hairball Audio "Lola" Mic Pre - On Sale Now

[shortyboyboy]

Hey Paul,

Thank you so much for the reply.  After getting stuck on a build like this it is very reassuring to know that there are people like you out there to help.  . Okay, I'll run through it.

When I turn on the Lunch Box the Lola will pass signal through the Mic Preamp for 1 second and than will fade out.  I am sure the preamp was working because I spoke into the mic while I adjusted the preamp output knob. In that brief time period I could hear the signal move with the output knob rotation. It also worked for a Phantom Powered Mic and DI input the same way.

To answer your other questions:

-I hear something inside click al little when I power up the lunch box.  I don't hear any different clicks when I plug the DI in other than the normal sounds of plugging a 1/4" into a socket.
- I am not sure how to test the voltages to the DOA's (I'm a newbie).  Do you have any youtube links on how to do this?
- Yes, I built the 2 JE-990's that Hairball supplied.
- I have not tested the IC's and Jfet's.  I'm not sure how to do this either :\
- I haven't built the LED meters yet, because I'm at the testing stage before hand.  Maybe I should?

When I put the pin inside of the Grayhill stepped gain knob I did as the directions said:  turned it all the way clockwise (gain all the way up) and inserted the pin in at 12'o.

Thanks again, Paul.

Do the relays click when you insert the 1/4" cable? Have you tested voltages to the DOA's? Did you build the 990's? have to tested voltages to the IC's and Jfet's? Power is usually the first thing you should check.

Do the LED's on the meter light up when you try to run signal through it? Have you tried adjusting the gain settings? You may have some bad connection with one of the Grayhill pins and or it's resistors.

Thanks!

Paul

 

[Potato Cakes]

Do you have any DOA's that were bought premade? If not, you need to get some before you really go any further. You also need an extension jig if you don't.

For testing voltages, take the (-) or Com lead from your multimeter to a ground connection and the (+) to the pins on the DOA which should be labeled V+, V-, C, O, In-, In+. If they are not you will have to look up the 2520 pinout. Pull your op amps and power it on and test the voltages. If they seem fine, power it off, put the DOA's back in, then power it back on and remeasure.

You should hear a relay click when you insert a 1/4" cable in the DI jack.

LED metering is not necessary for audio.

Go back over the build guide if necessary. It's very well laid out and if followed exactly you should have a working unit.



Thanks!

Paul

 

[Echo North]

Hello! I am at the testing stage of the lola mic pre and am having no luck getting sound. 

The Line, Phase, and +48 buttons light up.  The actual buttons click when I engage and disengage them, but not through my monitors or anything.  When I plugged the instrument 1/4" into the front there was no signal either. I think I may have heard a pop the first time i plugged it in.  Just nothing after that. 

I have checked my signal flow with cables and I should be getting a signal. No smoke is coming from the preamp, and it doesn't look or smell like anything has fried

I'm wondering steps I need to take to figure out what I did wrong here.  I will include pictures that can possibly help you see if I did something wrong.

Thanks so much!  I'm really looking forward to getting this preamp to work.

Also, make sure the edge card pins are very clean. Then look for suspect joints.  Like Paul mentioned, if you have other 2520 style op-amps, try those to see if you can isolate the issue to the op-amps.

Mike

 

[shortyboyboy]

Thanks Mike and Paul.

I'm looking at one of my JE 990 Built Op Amps and notice the two Output Transistor and Diode Maps may be touching at the inside legs.  They are super close together.  Do you think that could be an issue?  If so, is it okay to heat the part and then try to scrape it down the middle?  Thanks Guys

 

[Echo North]

Thanks Mike and Paul.

I'm looking at one of my JE 990 Built Op Amps and notice the two Output Transistor and Diode Maps may be touching at the inside legs.  They are super close together.  Do you think that could be an issue?  If so, is it okay to heat the part and then try to scrape it down the middle?  Thanks Guys

Those are connected on the PCB. They should be touching.

However, make sure the clips are not touching either leg.

Mike

 

[lordnielson]

Just finished a second Lola but have run into troubles.

One of the diy-990s doesn't work and when inserted it literally burns the 10r resistors (r31,31,36 and 37) on the main board.
I've checked, rechecked and compared it to the one that works and simply cannot find any errors solder nor component placement wise.

Any educated clues as to what would cause this malfunction ?

Also, I've got some spare api 2520s so I've got the unit working but unfortunately the DI distorts. When I use an external DI box all is good. Maybe something died when the 10r resistors burned (have since been replaced) ?

Thanks in advance.

 

[Potato Cakes]

Assuming all the parts are in the right place and oriented correctly, you may have a cold solder joint if you don't see any bridges. Reflow solder to all your connections and see if that does anything for you.

Thanks!

Paul

 

[lordnielson]

Assuming all the parts are in the right place and oriented correctly, you may have a cold solder joint if you don't see any bridges. Reflow solder to all your connections and see if that does anything for you.

Thanks!

Paul

Had the q8 and 89 transistors mixed upon the faulty one

Any suggestions on the DI issue ?

 

[Potato Cakes]

Same thing. Component placement, orientation, solder joints. It is possible to have a faulty transistor in the DI section. Measure the legs of the DI transistors of the  working Lola and compare them to the one with the issue. Be advised, if there is an issue with any of the items first items listed in this post that will affect voltage measurements.

Thanks!

Paul

 

[Echo North]

Just finished a second Lola but have run into troubles.

One of the diy-990s doesn't work and when inserted it literally burns the 10r resistors (r31,31,36 and 37) on the main board.
I've checked, rechecked and compared it to the one that works and simply cannot find any errors solder nor component placement wise.

Any educated clues as to what would cause this malfunction ?

Also, I've got some spare api 2520s so I've got the unit working but unfortunately the DI distorts. When I use an external DI box all is good. Maybe something died when the 10r resistors burned (have since been replaced) ?

Thanks in advance.

If it's just the DI, you may have a bad J201/2N5457 in the buffer.  You can shoot us an email.

Mike

 

[totalnoise]

Hello,

Just finished building my first Lola, and I'm doing some tests before assembling the meter pcb.  Line & phase buttons are making the appropriate click.  I started with a condenser mic using phantom, and everything seemed to be working great.  Only thing I noticed was with gain all the way down, and output all the way clockwise, I was still getting pretty significant level (possibility of clipping).  Is that normal? The input was all the way down on my soundcard (rme babyface pro).  I have a -10db pad on the mic I was using, which helped a bit when engaged.  The sound was great, so maybe this is normal. 

The primary issue, however, is with the DI.  I tested a synth and a guitar, and I was getting a very low level.  With the gain cranked, the level was still super low, with some noise.  I took the board out and checked a bunch of solder joints, redoing anything looking remotely iffy in the DI section.  The same problem persisted. 

Any help you can provide would be much appreciated.

Thanks,

Jeff

 

[totalnoise]

One other thing that may be worth specifying.  The DI when line mode is not engaged works great - only when the line button is engaged am I having these problems.  I did check all the solder joints for the line switch to be safe.

Thanks,

Jeff

 

[darkus]

One other thing that may be worth specifying.  The DI when line mode is not engaged works great - only when the line button is engaged am I having these problems.  I did check all the solder joints for the line switch to be safe.

Thanks,

Jeff

You shouldnt be using di with line input engaged. In line mode, the line input is the same where you would connect your mic.

 

[totalnoise]

You shouldnt be using di with line input engaged. In line mode, the line input is the same where you would connect your mic.

Well shoot, thanks Darkus!  Checked the line input with a mic, and it sounds great. 

False alarm!  I guess after building those op amps, I was convinced something would be off

 

[trevascus]

Hi!
Just built a pair of Lolas. All went well.

We can't seem to get enough level out of the preamps into Pro Tools without the meters hitting red. I don't have much experience testing so ELI5 where possible... ha!
Our converters are calibrated at 0dBU = -16dBFS

Running a signal at -50dB using the Behringer test box, using 50dB input  gain and output gain fully clockwise, the Lola meters 0dB in VU mode.
Running this back into Pro Tools, we see a level of roughly -20dB. With our converters calibrated as mentioned, we should see, -16dB correct?

This means that we can't get any more level out of the Lolas without distorting (not a nice distortion either!) I assume that's them clipping the output transformer? Cranking the input and rolling back the output so the meters aren't red lighting sounds good and saturates as expected, but we can still only get a max level into PT at -20dB ish.

So recording with acoustic guitar for example, the peak meter mode is smashing the red, and the VU is hovering around the 3rd LED.  It sounds a little splatty with transients. Hope I'm making sense...

We usually record at roughly -10dB into PT, but can't get to this level without the units distorting somewhere. Has anyone had anything like this happen before? How can we get more out of the unit without running into another processor to boost the gain?

Cheers,
James

 

[darkus]

trevascus Might want to check that you are not unbalancing somewhere. Make sure there is no continuity between xlr pin 2-3-1 anywhere in the chain

 

[trevascus]

That all looks good.
There just seems to be no real headroom. We have to set the input level really conservatively, otherwise it'll splat.

 

[Echo North]

That all looks good.
There just seems to be no real headroom. We have to set the input level really conservatively, otherwise it'll splat.

A few things. 

The Lola should have just under 65dBu of gain with a source impedance of 150Ω or less. 150Ω is a common condenser mic output impedance.  Also, do all of your testing with the output full CW. That means there is no attenuation on the output.

Secondly, the red light on the Lola is not a clip light. It's just a standard VU meter. like you see on say an 1176. When the red light illuminates in +4 metering, it just means you have +8dBu (1.95VAC) on the output. That has nothing to do with either your the Lola or your converters clipping. So don't be afraid to smash your signal into red.

Thirdly, protools meters in dBFS which is a different scale than dBu. Since the dBFS is dependent on your converter brand there is no conversion to dBu.

At -50dBu (not dBFS) it should be impossible to distort a Lola. -50dBu would mean you have 0.0025VAC across pin 2 and 3 of the input XLR. In that case with a source impedance of around 150Ω and both input and output fully CW, I would expect to see 3.88VAC across pin 2 and 3 of the output.

I'll be away for the rest of the day but give it a try again, I really think you just have gain staging issue. Don't worry about the red light.  Just hook up a condenser and talk into it. With the output fully CW you should be able to get a good strong signal in the 12-2 o'clock position.

Mike

 

[Echo North]

As a rough guide, depending on your converter model, 0 dbu is roughly in the area of -16 to -20 on your PT meter which is in dBFS.

Just for reference, here at Hairball we use a -40dBu test signal @ 150Ω.  With the input and output full, there is no clipping and 65dBu of gain.

Again, be careful of mixing up dBu and dBFS.

Good luck!

Mike

 

[trevascus]

Hi Mike, thanks for your response.

Good to know that the red light doesn't mean it's distorting. But the problem is then, with something dynamic like a vocal, when a loud part gets up into the red it throws out a nasty midrange peak, it almost sounds like the 600-1.5kHz seems to just poke right out. It does sound like it's distorting.

To avoid the vocal hitting the red (having the very loudest parts only getting up into that area) the rest of the vocal is only coming in at say -35dB in PT and isn't really showing on the lola meters...