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

[lowend]

I can't.... I dont know why....

Last step doen't works....

What is the size of allen key ?

I tried with 1mm : too small // with 1,5mm too small (??) // with 2mm too big
Do you have a 1,75 mm Allen Key ??

Now I'm afraid to have broken the screw because a lot a try....

EDIT : that's OK.... I used the 1,5mm and I forced... So it's OK now !!! I thnik I need a 1,75 mm Allen Key !!

Thanks again for your answers, your time, your video

 

[Echo North]

I can't.... I dont know why....

Last step doen't works....

What is the size of allen key ?

I tried with 1mm : too small // with 1,5mm too small (??) // with 2mm too big
Do you have a 1,75 mm Allen Key ??

Now I'm afraid to have broken the screw because a lot a try....

EDIT : that's OK.... I used the 1,5mm and I forced... So it's OK now !!! I thnik I need a 1,75 mm Allen Key !!

Thanks again for your answers, your time, your video

Cool glad you got it.

 

[bulghur]

Hey Mike,

After using the pre-amp for a few months, I definitely need to employ a pad on some instruments.  I wanted to run a couple of ideas past you on the DI input.  I see two FETs (infinite) and the 1M to GND.  I figure I will make an H network.

T-----R1------------> to C11
              |
            Rshunt = ?
              |
R-----R2----------- >to C10 (which is ground for unbalanced)

I want to make a switchable 10/20dB pad.

My first assumption is that the FETs are saturating on some active outputs. So, I will pad before hitting the FETs.  Does this make sense.  Next, what do you recommend as the Rshunt if I will be plugging basses and other passive devices in?  Will 1M or even 500K work to not load them down. 

I am using the maths from this site:  http://www.uneeda-audio.com/pads/

Should I pad elsewhere like before the input transformer.  If so, what do you recommend for Rshunt there? 

Thanks!
             

 

[Echo North]

Hey,

To be honest I've never done an instrument pad, just the more common mic. 

Hard to say what's clipping.  The FETs are set very near unity and are just impedance buffers.  The instrument is seeing buffer (near unity)->Input TX->(+6dB)->Opamps (+7ish)->Output tx (+4dB) IIRC.  I assume you're turning the output pad right down and still hearing clipping (confirming it's in the Lola?

It's hard to say without testing it on the bench but I'll tell you where I would start.

I would try a balanced H pad off the T and R into C10 and 11 like you suggest.  I'd use something like this calculator:
http://www.nu9n.com/tpad-calculator.html

5 Resistor (w/ shunt) version to be safe.  I'd keep the input and output impedance in the calculation for you pad something general and similar to your instrument out (10K?) to start.  Hard to say what neg effect that might have on loading.  Hopefully just a little level loss, which is ok in this case.  If it's neg (ie bad sound) maybe try 50K on the in/out or even 100K which would be more than enough for anything.  But I would start there.  Report back or call me crazy if I'm crazy!

Mike

 

[bruce0]

Hairball:

I use that site too, but I should warn you or you should be aware that if you are using it to calculate H-Pad's (as opposed to T-Pads), it is not accurate. (  I reported to the site manager, and they are aware ) Here is an example:

I input 30db H-Pad with input impedance of 32500 and output of 970 and it
gave me primary resistors of 16105 ohm secondary of 308 ohm and a shunt of
355 ohm.  When I calculate (and actually built that) it is a 39.24dB pad not
a 30 db pad.

The uneeda tables are a better approach if you want the pad accurate.  Or trial and error with a spreadsheet works, or Audiocylopeadia has some tables.

 

[bulghur]

Thanks Bruce0 and Mike,

I am going to calculate my own "k" values using the form: k=10^(desired dB drop/20).  I think this should give me what I need for the H network.  Then I will work using the form Rser/Rshunt=k-1.  I will then half the Rser values for each end of the input relative and that should give me the drop. 

Mike, to your questions:  Yes, the input distorts on high output devices -- some more than others -- with the gain set minimum and the output set to low.  Hmmm, the FETs are unity.  I might put the Lola on the bench and scope the signal to see where the distortion is occurring -- it is not all out, it just scrapes the upper end here and there.  I'd prefer to pad it deeper in the beast -- say, right before the input transformer.  That way, lower impedance means easier to find resistors in my stock . I'd like to minimise loading passive instruments and like that FET in the path for that purpose.   

 

[mylesgm]

what other DOA could work in the lola?  I've got a pile of yamaha opamps and am wondering if they would suit this build... NE80200 and NE80100.

cheers

 

[Echo North]

what other DOA could work in the lola?  I've got a pile of yamaha opamps and am wondering if they would suit this build... NE80200 and NE80100.

cheers

I've only tried  2520 and 990 types.  If they are rated for +/-16V give them a try!

 

[mylesgm]

they are both rated for +/-24v and they are touted as replacements for any 2520 opamp.  I've used them in places where you could use a 2520 without problems but I wanted to know if anybody had tried it.  Seems like I might be the first when I get around to building a pair...

 

[domus]

Ah shit, just fried one of the op amps and atleast the 31 and 32 resistors...thought I had checked everything but apparently not...

Don't know where I went wrong, but my guess is the op amp....?

I'm kinda a noob with electronic stuff, but I am trying to learn and get better...pretty good at soldering and follow instructions though, haha

I checked the build without the op amps, and the blue light come on when I press the buttons and I can hear the relays. I've tried to connect a guitar and mic to it, but don't get any real signal. Should I get that when the op amps are not connected?

Can anyone point me in the right direction here I would be very thankful!

Thx
Nikke

I can hear the output increasing and decreasing when turning the output knob, but that just the noise I'm hearing. Not the guitar or mic...

 

[Echo North]

Ah sh*t, just fried one of the op amps and atleast the 31 and 32 resistors...thought I had checked everything but apparently not...

Don't know where I went wrong, but my guess is the op amp....?

I'm kinda a noob with electronic stuff, but I am trying to learn and get better...pretty good at soldering and follow instructions though, haha

I checked the build without the op amps, and the blue light come on when I press the buttons and I can hear the relays. I've tried to connect a guitar and mic to it, but don't get any real signal. Should I get that when the op amps are not connected?

Can anyone point me in the right direction here I would be very thankful!

Thx
Nikke

I can hear the output increasing and decreasing when turning the output knob, but that just the noise I'm hearing. Not the guitar or mic...

You need the opamps in there.  The amplify the signal. 

If you fried 31/32 then you have an issue with the opamp in the DOA 1 slot. You have a short or misplaced part.  Check that the output transistors ME171 and ME 181 are in the right spots.  Look for shorts.  Look for the diode leads touching the clip on the output transistors.

Mike

 

[domus]

Thx, I'll check that. I need to get new parts though, cuz I think I fried some of the components on the DOA...

Looked awesome with all the smoke, but didn't make me happy, lol

/Nikke

 

[Echo North]

Thx, I'll check that. I need to get new parts though, cuz I think I fried some of the components on the DOA...

Looked awesome with all the smoke, but didn't make me happy, lol

/Nikke

Unless you did something REALLY messed up.  Just the 31/32 on the main board should have fried.

 

[domus]

The R13, 14 on the DOA are fried. The JE 171 and 181 seemed to have gotten very hot, but I don't know how much they can take? Atleast they are in the right place...

/Nikke

 

[Echo North]

The R13, 14 on the DOA are fried. The JE 171 and 181 seemed to have gotten very hot, but I don't know how much they can take? Atleast they are in the right place...

/Nikke

Ya it's like you have a dead short rail to rail there.  Carefully inspect the diode orientation of CR9-12 and look for any shorts around there.

 

[domus]

Do you think I need to replace the 171, 181 too?

The diodes are in the right direction, but I will redo all the solder work. Hopefully I didn't destroy the circuit board

/Nikke

 

[Echo North]

Do you think I need to replace the 171, 181 too?

The diodes are in the right direction, but I will redo all the solder work. Hopefully I didn't destroy the circuit board

/Nikke

Those are pretty tough transistors.  They are probably fine.

The 10Ω resistors that fried on the main PCB are there to protect the rest of the circuit.  They are like little fuses.  If something is wrong they fry and keep your main PCB and rack safe.

 

[gyraf]

Question:

We just had two incidents of a Lola killing the -16V line in 51x supplies (we do not know the cause yet) - the schematic in the Lola manual does not show reverse-spike-protection diodes on the supply lines (ya'know, from minus to gnd and from gnd to plus) - wouldn't these be a good thing to include? Or are they already there?

(please excuse me if I'm wrong, just trying to do a quick diagnostics for the guys in our studio)

Jakob E.

 

[Echo North]

Question:

We just had two incidents of a Lola killing the -16V line in 51x supplies (we do not know the cause yet) - the schematic in the Lola manual does not show reverse-spike-protection diodes on the supply lines (ya'know, from minus to gnd and from gnd to plus) - wouldn't these be a good thing to include? Or are they already there?

(please excuse me if I'm wrong, just trying to do a quick diagnostics for the guys in our studio)

Jakob E.

Hi Jacob,

That's really weird.  I've not come across anything like this.

Yep the protection diodes are there.  D1 and D3 they are up by the edge card connector/input transformer.

Mike

 

[gyraf]

Thanks for quick answer - I found two 1N4007 diodes over between the two transformers, beside the ribbon connector.

These two are apparently connected in series with +/-16V power in, protecting the module from reversed power. Which is obviously good. And Both Lola's survived the incident - which proves them well protected.

At a side note - we don't know WHAT killed the 51x supplies, only that Lola's were the only modules mounted at the time (they sound good btw, but you already know that).

The sort of protection I was looking for is reverse diodes from ground to plus and minus rails, preventing them from being pulled to wrong polarity no matter what happens.

At a second thought, this type of protection should probably go in the PSU - afaik, there is no such protection in the 51x supply (again, I'm not absolutely sure, the 51 system is new to me). Will report back.

Jakob E.