MONO Ver2 Mic pre kit BUILD THREAD

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MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Wed Apr 27, 2011 5:36 pm

JLM MONO Ver2 mic pre is a compact tough transformer balanced input mic pre with electronic balanced output which can run on 2 x 9v Normal Alkaline or Rechargeable NiMH batteries and provide 18v phantom power which will run most modern condenser microphones or you can use our 48v 520mA SMPS which can charge NiMH batteries at the same time as running the mic pre with 48v phantom power and greater headroom. One 48v SMPS can run and charge 8 MONO Mic pres easy. As usual the same large variety of input transformers can be used as Baby Animal and Baby Animal Dual. The pre is made to run one Dual NE5532AP on 18v battery power up to 27v with zener reg fitted or OPA2604AP opamp on 18v battery power up to 48v SMPS power but can have 2 x JLM99v and compatible footprint discrete opamps fitted with no component changes but the battery power option is then lost. Kit comes with a full laser cut die-cast aluminum box and black lexan text front panel top.
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Internal single sided PCB fitted with components for electronic training version for JMC Academy and TAFE Colleges.
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Parts List MONO Training Version
MONOv2 Schematic

MONO Upgrade options on JLM web shop
(Main upgrade the training version needs is the input transformer to get a real top end mic pre & 48v SMPS for true 48v phantom power and +28dBM huge output level)
JLM14 Input transformer (Great for drums, bass, samples and general very good all rounder)
OEP262A3C/VTX Input transformer (Great Vocals, Acoustic Instruments. Bit more coloured as used in our Dual99v mic pre)
JLM99v discrete opamp (Fatter low end and silky high end then OPA or Hybrid)
6 Sockets to plug in JLM99v etc
48v SMPS power supply (Can run & charge 8 x MONO mic pre at one time)
2 x 9v NiMH batteries

1. Install all resistors in there correct locations using chart to the left or better still by using a multimeter with no leads fitted and bending the legs of the resistor and putting them in the meter sockets to double check you have the right value before putting it into the PCB.
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Red Transformer Training Version RPad = 120R, RGain = 22R Rload = Not Fitted, RZobel = LINK, Czobel = 390pF.
(If you are thinking of upgrading your college version later to one of the better transformer versions below it is fine to fit the below values now with the Red transformer. Rload will not affect the red transformer and the larger Rgain will just give less gain until the upgraded transformer is fitted.
JLM14 Transformer fitted fitted to Training Version MONO RPad = 120R, RGain = 68R Rload = 10k, RZobel = LINK, Czobel = 390pF.
JLM14 Transformer fitted fitted to Normal Version MONO RPad = 120R, RGain = 68R Rload = 2k2, RZobel = LINK, Czobel = 390pF. Impedance pot 50k log
[/b][/color]OEP 262A3C / VTX Transformer fitted to Training Version MONO RPad = 120R, RGain = 68R Rload = 27k, RZobel = LINK, Czobel = 390pF.
OEP 262A3C / VTX Transformer fitted to Normal Version MONO RPad = 120R, RGain = 68R Rload = 10k, RZobel = LINK, Czobel = 390pF. Impedance pot 100k log
(The MONO PCB has a impedance pot option which is not used in the Training kits so when fitting RLoad the small white line between 2 holes at one end of RLoad needs to be jumper over with a resistor leg cut off. See near bottom of this post)

1.Fit all resistors before soldering them as this can also help check that you haven't put a resistor in the wrong place.
2. Install all diodes with there Grey/White/Black strip band lining up white white band on the PCB.
RC can be either 47R or 51R. Kit may have 3 x 51R or 2 x 51R + 1 x 47R
27v zeners maybe red or silver type but check number on zener is 1N4750 or 1N4750A

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RPad 120R can be mistaken for a 10k if the code is read from the wrong end.
The colour stripe spaced wider apart then the rest of the stripes is always the tolerance stripe and should be kept to the right hand side while reading the colour code value.
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RGain is 22R in training version with red transformer and 68R with JLM14 & OEP/VTX transformers.
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RZobel is a zero ohm link resistor for all normal MONOv2 configurations
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3. Once all resistors and diodes are fitted solder them in with the PCB held upside down on a flat surface and then cut there legs just flush above the solder joint.
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Use one of the cut off resistor legs for the IMP link and solder in then cut there legs just flush above the solder joint.
Note if installing variable impedance Z control fit 2 wires here instead
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4. Fit IC Socket with the U aligned with the overlay and solder in. Then fit R7 & R8 the 2 x 100pF caps either way around. And CZobel 390pF cap.
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5. Place the 1 x 100uF and 6 x 470uF caps on the PCB with there long leg fitted in the hole marked + which is a square pad under the PCB.
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6. Solder in all 7 caps which should all be facing the same direction when finished.
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7. Fit transformer to the PCB. No gap needs to be left for any of the transformers as the PCB is single sided. Red transformer shown below. JLM14 bolts to PCB and the four colours of its wires are marked on the top of the PCB. Black is not connected to anything. JLM14 wires go into large centre hole and solder under the PCB. OEP transformer only fits one way on the PCB making it easy.
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8. Solder in the transformer wires and then fit the XLR's and solder them in.
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9. Push in all toggles with there U notch away from the XLR's. Make sure they are sitting flat and level to the PCB.
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10. With the XLR's fitted you can do a test fit into the case and check the 4 toggles switch up & down in there slots ok with only one centre pad soldered encase the toggle needs to be moved slightly before soldering all the switch legs.
(Watch out when cutting of soldered legs that they are actually soldered otherwise they can be hard to fault find later)
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11. Fit BD681 transistor as shown and solder in.
Note if installing JLM99v opamps no NOT fit BD681. Instead fit link wire between C & E as PCB overlay shows
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12. Use long nose pliers to bend the 3 pot legs 90 degrees.
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13. Extend the legs by using the full leg length from the two spare zero ohm links in the kit.
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14. Extend the DC connector legs with 3 cut off zener diode legs as shown. The zener diode legs are thicker and stiffer than the resistor legs.
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15. The DC connector fits into the PCB with its 3 legs going directly into PCB as shown.
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16. The 3 LED's are placed into the positions long leg to A. Do not swap the LED colors around at all as this will affect the charge circuit.
(Placing your thumb over the LED hole while bending the LED legs sticking out of the solder side outwards from each other slightly will allow the led to hang at the right height ready for soldering)
You want the led in the hole but not sticking out the other side of the hole as the lexan panel cover the hole with a frosted lens.
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17. LED's in position but will not be soldered until fitted to the case with the gain pot to get the right height.
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18. PCB placed upside down on top of the case to get lengths right and then DC connector and 3 LEDs can all be soldered.
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The PCB can then be test fitted inside the case go the Gain pot height can be set and soldered in place.
(This cannot be done outside of case as pot keyway will stop the pot going into position correctly.)
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19.Fitting the Battery leads. Note positive and negative are reversed on each side.
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20. Leave these solder pads unsoldered for normal 9v batteries.
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Only solder together when using rechargeable NiMH batteries.
(Soldering together enables charger and orange charge LED)
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21. Fit NE5532AP IC into the DIP socket with its U aligned with the IC socket upwards as shown below.
Ready to test in the open with 2 x 9v batteries or 48v SMPS.
If testing without batteries fitted put some tape on the 9v clips to stop them shorting to anything.
Please make sure you have your monitors or headphones turned down when power on or off on the MONO mic pre to save your ears :-)
Note you can only fit IC1 DIP8 opamp like NE5532AP or IC1A,IC1B large JLM99v opamps. Do NOT fit both types at once.
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22. MONO training version PCB fully built.
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23. Shows the stick on black rubber strip for holding in the 9v batteries firmly.
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24. Shows plastic protective sheet used to stop the 3 points in red circles from touching the lip of the diecast bottom panel.
Make sure all soldered pad joints especially the ones in the red circles are cut short and the plastic sheet need to be a tight fit in the back of the case.
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25. Black edge of slots and XLR holes with black permanent pen to remove shine from edges.
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26. Fit PCB to case and do a test fit of the lexan panel before removing the backing to check best alignment.
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27. Remove sticker backing
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28. Flex lexan panel so it can be aligned by the DC and Gain pot holes.
Sticker can be removed if not pressed hard down on.
(Sticker can be fitted with the case empty or with the PCB fitted so DC connector and Gain pot can help to align the sticker)
(Note sticker holes for DC connector and Gain pot are 0.5mm larger so the sticker can still be moved around slightly for better overall alignment)
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29. alignment is correct the sticker can be pressed down hard from the center out.
After about 24 to 48 hours the glue on the sticker will bond with the case making it very hard to remove.
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End of Training version

Z pot wiring on MONO normal version.
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Shows Z pot wiring and MONO with 2 x 99v Fitted.
NOTE When fitting JLM99V to MONO do NOT fit C7 or C8 100pF caps as we have found this makes the MONO pre more stable and less prone to oscillation when using the 99V
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For Z pot wiring do NOT fit this jumper. Wire the two Z pot wires to here instead.
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Note first 99v opamp removed only to show wiring better
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Note first 99v opamp removed only to show wiring better
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Joe :-)
JLM Audio
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TiravTiger
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby TiravTiger » Sat Oct 01, 2011 9:26 am

Heyy!
Did this as the electronics assignment at JMC Academey Melb. Loved how easy this was to build and sounds great, thought i would share some pics of my finnished version :wink:
As mentioned about battery life too, its a single 3mm LED on the spare 2K7 resistor i had, overkill but works great and still going strong and it has had a fair beating already on the same pair of batteries!

Off -
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On -
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oh and the teachers loved it so much they gave me a second to do but in all red. Red paint job, red LED. Tried red perspex but the LED didn't shine through, so will be using clear again but have a brighter (compared to the white LED) red LED for this one. Will post pics when completed :wink:

Travis.

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Mon Oct 03, 2011 9:51 am

Wow a Pimped Bling MONO Cool :D
Joe :-)

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TiravTiger
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby TiravTiger » Tue Oct 25, 2011 3:46 pm

Finished it two backs but didn't have time to upload pics, but here is the blue and the new red pre :D hope you like!

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On-
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Cheers,
Travis.

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Wed Oct 26, 2011 8:41 am

Cool. Just need a red and blue chicken head knob on them and they would be perfect :-)
Joe :-)

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TiravTiger
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby TiravTiger » Thu Oct 27, 2011 10:36 am

i did try to find some but my local jaycar and altronics both don't have them!

They sound great though, used the blue one for 4hours the other day for a recording
straight into the line in on a MBP (ran out of pres), crystal clear even running through the line in,
was actually quite amazed, and still going strong on original 9v batteries!

Travis.

mattsyd7
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby mattsyd7 » Wed Dec 07, 2011 1:52 pm

Here's some notes from my experience, including some excerpts from emails back and forth with Joe. Hope this helps newbies like me starting out.

Email to Joe:
The mono sounds great. It leaves the pres on my metric halo 2882 for dead. Thanks. It really did sound good, brought my RODE NT 1000 to life. I have a Groove Tubes GT-67 valve and a ribbon mic I'm looking forward to testing out when I get them back from my mate.

That first test was with a cracked volume pot too by the way. When I put it together I tightened up the 10K rev log pot (alpha 8h1) and it cracked at its base. NOTE: Be careful not to tighten it too much!! It seemed to me not to be tight enough, but obviously it was.
I got a new one sent down and replaced it.

Next, because I used a cheap soldering iron, I heated up the board too much and lifted some of the tracks. Joe suggested I use a component leg to solder the part to its proper place following the track on the back of the PCB. See picture with arrows pointing to fix.
back pcb.jpg


Mistake no. 3
I cut the plastic to narrow and as a result the unit shorted against the case. I charred the brown carbon resistor named 10R, (10 Ohm) which acts as a slow blow fuse. Upon Joe and Josh's advice I replaced the 10r slow blow carbon with the only 10r Jaycar had, a 5w metal
film resistor. JLM use carbon so that it smokes up on fault, letting you know there's a problem. The one I replaced it with will just go open circuit making the fault harder to trace but still acting as a fuse. I'd say 9 times out of 10 if there's a fault with this device it'd be 10R anyway. Right Joe?

Moving along in the Comedy of Errors...
The left battery got quite warm at one point. I noticed the black lead had shorted against the red lead due to me moving it around too much. I fixed this up and moved on.

The unit still wasn't working so Joe suggested I test the power supply, it read 47V so it was ok.
Next, Joe says "Do you get about 25v at the pin 8 of the IC to the
ground or case? This proves the reg it working when running on the 48v
supply."
Yes, I did, 25.1V. All good there.

Pin 8 is this one ->**** where the dot on the op amp is on the left.
****
I found ground by putting my multimeter on the middle pin of the AC power adapter which is mounted on the PCB.

Next, the unit was only passing audio when I had the gain pot UP, and it sounded hissy and horrible.

So we decided to replace the op amp which I would have shorted somewhere along the way. I ordered it from RC Components in Smithfield, Sydney. Next day delivered for few bucks!

That next afternoon I hurriedly replaced the op amp as by this stage I was running out of steam.

The f*%$ing thing still didn't work. It distorted like crazy, it actually sounded quite cool as an effect.

I called JLM and then it started working again, perfectly. It was then that I noticed the right hand battery lead was loose. I soldered it up and am now pleased to say it's been going strong ever since.

So the moral of the story is, remove the op amp when doing repairs, make sure the plastic back covers the entire board and use a decent soldering iron. Lastly, if this is your first project, be patient!

Here's a pic of the finished version, doing just what it should.

Thanks Joe and Josh for your help.

Matt
jlm finished.jpg
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Risto
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Risto » Sun Apr 28, 2013 7:13 pm

Hi all, I've almost completed this kit. The glowing recommendation for the kit came from Rob at Proharmonic and I feel I'm in safe hands. Some observations/questions:
- Don't link the "IMP" with cutoff resistor legs if making the non-student version. In fact, probably wire up the impedance pot before installing the capacitors nearby.
- Using the JM14 transformer, white washers go between the transformer and the board. (still not sure whether the transformer wires should be pulled through and wired from bottom. I left the wires on top of the board and pulled them through and soldered them like everything else).
- Missing a red LED light (but received 3 battery leads), will get one from Jaycar but a little worried I might get something wrong. Do I need to concern myself with voltages or anything in relation to this?
- Had to remove the 100pF capacitors after reading much later about the JLM99V stability improvement.
- Was missing a bolt and washer for my gain pot.

I will fire it up after installing the red LED. My only real suggestion is that there might more appropriately be a separate thread dedicated to the educational vs other versions.

Either way, great fun and thank you for the well thought out and implemented kit.

cheers
Risto

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JLM14 & single JLM99v combination

Postby Risto » Fri May 03, 2013 1:35 pm

With some help from Joe, I have mine working. My most fundamental problem with using an XLR cable that was faulty. I haven't been wrong for anything for so long that this humbled me and has helped me with with my self-proclaimed God complex.

Some observations and advice (some repeated from my previous post) that may be relevant to anybody that wishes to manufacture this permutation of an excellently conceived preamp:

- Don't link the "IMP" with cutoff resistor legs if making the non-student version. In fact, probably wire up the impedance pot before installing the capacitors nearby.
- Don't install the 100pF capacitors, leave empty (read much later about the JLM99V stability improvement).
- JLM14 transformer washers go between the transformer and the board and coloured cables are pulled through the hole in board and soldered from the bottom.
- Single JLM99v configuration is installed in the "A" side which is the left hand side of the board.
- "B" side (empty JLM99V section) remains empty but add a wire to the B 99v position (where the 99v was in the photo) between -v
and out.
- Do not use the BD681 transistor (if supplied) and instead put a wire link between C and E (white line on PCB overlay between middle hole.)

If you were given the NE5532AP in your kit, you do NOT use the NE5532AP AND the JLM99V together. I may well be the only one who tried this unholy (and unworkable) combination.

Some testing that was useful to Joe for diagnosis:

Is there 48v between -v and +v on the 99v?
Mine 47.2

Is the output of the 99v sitting at roughly 24v measured from the -v?
Mine 24.9

What ohms do you get between red and green on the JLM14?
Mine 27

What ohms do you get between blue and yellow on the JLM14?
Mine 429

My results apparently checked out fine.


Hope it helps someone and thank you again to Joe for his help.

dane999
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby dane999 » Thu Jun 06, 2013 3:25 am

Hi there !
I'm building the mono V2, and the red led is missing too ! Risto or joe : which kind of led should I get ?
Can't wait to hear this little big pre !
Thanks !

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Thu Jun 06, 2013 7:35 am

dane999 wrote:Hi there !
I'm building the mono V2, and the red led is missing too ! Risto or joe : which kind of led should I get ?
Can't wait to hear this little big pre !
Thanks !

The Red led is a 3mm high brightness of about 600 to 1000mCD (or more if fine) so it can light via the 100k resistor on the board and not use much current.

I can send you one by mail today if you need.
Joe :-)

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dane999
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby dane999 » Thu Jun 06, 2013 4:59 pm

Hi Joe,
Thanks for the answer and the proposition ! No problem for the LED, I'll get one by myself, seems more appropriate than sending it overseas to france...
Will this one do fine ? http://fr.farnell.com/jsp/search/productdetail.jsp?SKU=1142524

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Thu Jun 06, 2013 6:00 pm

dane999 wrote:Hi Joe,
Thanks for the answer and the proposition ! No problem for the LED, I'll get one by myself, seems more appropriate than sending it overseas to france...
Will this one do fine ? http://fr.farnell.com/jsp/search/productdetail.jsp?SKU=1142524


OK Cool :-) That led in the link will work perfect.
Joe :-)

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dane999
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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby dane999 » Fri Jun 07, 2013 10:32 pm

Working perfect indeed ! Fired up first try, everything working fine. I'm quite happy (and a bit proud) as a first "serious" DIY project...
Had only a small problem to fit the circuit in the case because I pushed the JLM99v's sockets a bit too deep, but solved that after some unsoldering struggle...
The sound is really awesome compared to my amek-tac bullet preamps, which are already cool, but with this one, after a quick test, the sound is obviously fatter, cleaner, and a lot more quiet. Impedance option is also absolutely useful in my case, and worth the time spent to get the pot in the right place to fit the case...
Thanks a lot again Joe for making these kits !

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Re: MONO Ver2 Mic pre kit BUILD THREAD

Postby Joe Malone » Tue Jun 11, 2013 10:03 am

dane999 wrote:Working perfect indeed ! Fired up first try, everything working fine. I'm quite happy (and a bit proud) as a first "serious" DIY project...
Had only a small problem to fit the circuit in the case because I pushed the JLM99v's sockets a bit too deep, but solved that after some unsoldering struggle...
The sound is really awesome compared to my amek-tac bullet preamps, which are already cool, but with this one, after a quick test, the sound is obviously fatter, cleaner, and a lot more quiet. Impedance option is also absolutely useful in my case, and worth the time spent to get the pot in the right place to fit the case...
Thanks a lot again Joe for making these kits !


Great to hear you got it working and like the tone :D 8)
Joe :-)

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