BAN Build Thread

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Joe Malone
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Re: BAN Build Thread

Post by Joe Malone »

prhunt wrote:Thanks for fuse info, Joe.

I have finally built my 4 BANs and have power tested and performed alignment.

As mentioned previously, I am using the BD681 and a 39V zener, which gives about 38.6V at the base of the BD681 and about a volt less at the emitter. I'm setting 1/2V at TP3 at about 18.8V.

I found that the voltages took a while to settle during the alignment procedure, particularly the gain pot trim. Is this expected?

In any case, I am going to double-check everything - I'll let the boards idle and warm up for 10-15 minutes and test voltages again before installing in the case.

Thanks again.

Paul
The DC trim is best done after the unit has been on for 30 minutes or more with the lid sitting on it so the unit is at it normal running temp.
Joe :-)
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prhunt
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Re: BAN Build Thread

Post by prhunt »

Joe Malone wrote:The DC trim is best done after the unit has been on for 30 minutes or more with the lid sitting on it so the unit is at it normal running temp.
Cheers Joe. That's what I ended up doing.

Paul

mybishi
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Re: BAN Build Thread

Post by mybishi »

Does any one know where the variable impedance pot connects in the BAN circuit. It is an available option yet the schematic, pc board, overlays, and build thread do not mention where this component interfaces. Unfortunately, I am not yet learned enough to be able to deduce the pots correct location, referencing the schematic alone. I know that on the BA PC and schematic, the pot connects at RLoad but no such label exists on the BAN pc, schematic, etc. I'm not sure that this makes a difference, but there is no output transformer and I am utilizing 2 x BC550C and 1 x OPA2604AP in IC2 and a JLM99v in IC 1.

Thanks in advance and thanks for all of those that donate their time to help educate audio electronic freshmen like myself,
Nick

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Re: BAN Build Thread

Post by Joe Malone »

mybishi wrote:Does any one know where the variable impedance pot connects in the BAN circuit. It is an available option yet the schematic, pc board, overlays, and build thread do not mention where this component interfaces. Unfortunately, I am not yet learned enough to be able to deduce the pots correct location, referencing the schematic alone. I know that on the BA PC and schematic, the pot connects at RLoad but no such label exists on the BAN pc, schematic, etc. I'm not sure that this makes a difference, but there is no output transformer and I am utilizing 2 x BC550C and 1 x OPA2604AP in IC2 and a JLM99v in IC 1.

Thanks in advance and thanks for all of those that donate their time to help educate audio electronic freshmen like myself,
Nick
The BAN usually is used for its high 20k input impedance and has no impedance pot.

But you can add one directly across the +in and -in terminal.

Use our normal Z pot (dual 100k centre detent log pot) wired using both halves of the 100k log pots wired in parallel to make a 50k log pot (join front 3 legs to back three legs) in series with a 330R resistor to make 300ohm to 15k variable impedance for BAN. It will be 6k at the center detent position.
Joe :-)
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msmithers
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BAN with phantom power and no output transformer?

Post by msmithers »

Hi Joe, et. al.,

Sorry if I'm missing the obvious. Can the BAN run with phantom power and no output transformer? The product page says the kit runs on a single 48V power rail, but does this also supply the phantom? Is there anything else I need other than a BAN, my choice of output op-amp, a 48V SMPS and maybe a variable impedance pot?

Thanks & regards,
Michael

prhunt
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Re: BAN with phantom power and no output transformer?

Post by prhunt »

msmithers wrote:Sorry if I'm missing the obvious. Can the BAN run with phantom power and no output transformer? The product page says the kit runs on a single 48V power rail, but does this also supply the phantom? Is there anything else I need other than a BAN, my choice of output op-amp, a 48V SMPS and maybe a variable impedance pot?
I'm sure Joe will jump in, but here's my few cents' worth...

The BAN runs from a single +48V DC supply. Phantom power is available on each board, and is taken from the +48V DC supply - no separate phantom power required.

You need to know the supply voltage for your chosen op-amp, and apply the power supply mod to the BAN board, as appropriate to suit the op-amps.

The BAN circuit provides a fully balanced differential output, so no output transformer is necessary.

Not sure I personally would implement an impedance pot - the BAN is more about capturing natural sound, and not introducing colour of its own. But each to his/her own!

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Re: BAN Build Thread

Post by Joe Malone »

Yes like Paul said above

The 48v is used for 48v phantom power and also as +/-24v for the opamps or less +/-V if on board reg is used.

If using normal OPA2604AP as output opamp as well the BAN is electrically balanced out.

If using a 990 type footprint output opamp you can run quasi balanced out like modern neumans and mastering gear by linking pin 4 to pin 7 on the output DIP8 socket under the 990.
This pulls XLR pin 3 to 0v via the 51R output resistor so the XLR pin 2 with audio and XLR pin 3 with no audio have the same impedance to 0v for noise cancelling.

Both ways above work fine or you can add a output transformer when running 990 footprint opamps if you want fully floating output but this is not really needed in most studio use.
Is there anything else I need other than a BAN, my choice of output op-amp, a 48V SMPS and maybe a variable impedance pot?
No that is all you need plus a case and knob.
Joe :-)
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mybishi
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Re: BAN Build Thread

Post by mybishi »

I'm miffed as to where the 68r resistor goes on a BAN with JlM99V output opamp and no transformer. I don't see it on the board schematic or anywhere on the build thread. I think it's RG but I don't know enough to be able to place it correctly in the circuit. Any ideas y'all?
Thanks
Nick

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Re: BAN Build Thread

Post by Joe Malone »

mybishi wrote:I'm miffed as to where the 68r resistor goes on a BAN with JlM99V output opamp and no transformer. I don't see it on the board schematic or anywhere on the build thread. I think it's RG but I don't know enough to be able to place it correctly in the circuit. Any ideas y'all?
Thanks
Nick
BAN doesn't use 68R for RGain. RGain on the BAN is made up of two 10R resistors as gain is made by the transistor pair on the front end of the BAN.
Joe :-)
JLM Audio
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mybishi
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Re: BAN Build Thread

Post by mybishi »

Joe,

Again, thank you for such a quick reply. Glad to know I'm not going crazy. In the case of an oversight, I thought I'd mention that the BAN kit includes the 68R resistor and it is on the parts list. Howevrer, I can't complain about a free resistor with every purchase ;)

Nick

mike
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Re: BAN Build Thread

Post by mike »

Hi Joe,

I have just populated my first BAN PCB and I have a few simple questions before I start soldering.

1) In what direction do I solder the LED across the top two pins of the 48 v switch?

2) For inductors L1 and L2 I received the parts that look kind of like two diodes connected in series. Do I just pass these through the two outermost holes and leave the center hole unused?

3) I am doing a standard 4 PCB build. Is it correct that I do not need anything in the following spots:
- *47v
- *10k
- #10k
- Zener

4) Do I put a jumper across the two pins on the BD681 that is towards the switches and center of the board? Do I do anything with the BD681 that is toward the back of the board?

5) For my transistors, I have purchased SSM2212 surface mount components I will be soldering to surface-to-DIP boards, and then putting in a DIP8 socket. I am not sure of the direction of the SSM2212 after all this. Is there any harm from accidentally reversing the SSM2212 when I power on?

6) My power adaptor is Output 48V 0.52A 25 W "Mean Well GS25A48-P1J". Do I need to do the soft start mod? If so is it correct this involves:
- Adding #10k resistor
- Cutting the two traces coming from the indicated hole
- Adding a jumper from the indicated hole to the other indicated hole
- Adding BD681 at back of board (I do not have a BD681 in my received parts kit)

The first post in the thread suggests this mod is needed but later in the thread you say:
Joe Malone wrote:We do not recommend doing any mods on new builds. Just use the correct size power supply for the correct number of BANs.
Thanks,
Mike

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Re: BAN Build Thread

Post by Joe Malone »

mike wrote:Hi Joe,

I have just populated my first BAN PCB and I have a few simple questions before I start soldering.

1) In what direction do I solder the LED across the top two pins of the 48 v switch?
Anode long leg to top 48v switch leg closest to the side of the PCB. Cathode short leg to other top 48v switch leg.
2) For inductors L1 and L2 I received the parts that look kind of like two diodes connected in series. Do I just pass these through the two outermost holes and leave the center hole unused?
Yes correct
3) I am doing a standard 4 PCB build. Is it correct that I do not need anything in the following spots:
- *47v
- *10k
- #10k
- Zener
Yes if you are using 48v (+/-24v)type opamps these parts are no needed.
4) Do I put a jumper across the two pins on the BD681 that is towards the switches and center of the board? Do I do anything with the BD681 that is toward the back of the board?
Yes jumper between C & E where there is a white line between on the overlay on both.
5) For my transistors, I have purchased SSM2212 surface mount components I will be soldering to surface-to-DIP boards, and then putting in a DIP8 socket. I am not sure of the direction of the SSM2212 after all this. Is there any harm from accidentally reversing the SSM2212 when I power on?
Hard to say it would be best to get it correct first time but I think since they would be reverse polarity you should be fine.
6) My power adaptor is Output 48V 0.52A 25 W "Mean Well GS25A48-P1J". Do I need to do the soft start mod? If so is it correct this involves:
- Adding #10k resistor
- Cutting the two traces coming from the indicated hole
- Adding a jumper from the indicated hole to the other indicated hole
- Adding BD681 at back of board (I do not have a BD681 in my received parts kit)
We do not recommend doing the soft start mod on any new builds. It is best to use the correct size power supply. Test the 4 normal built BAN on your power supply first to see if it is ok or if power supply goes in to hiccup protection.
Joe :-)
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mike
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Re: BAN Build Thread

Post by mike »

Thanks Joe. That's all pretty clear. I've finished soldering the main board and now I just have wiring to do. I'm wondering if you can simplify it for me so I don't screw it up. Do you have a picture of one wired? It might be easier to figure it out from.

1) If the volume potentiometer pins are numbered as follows:
Image
Which pin is wired to the "gain pot" circuit pad spot closest to the edge of the PCB and which pin to the pad closer to the middle of the PCB?

2) What are the green 6 pinned potentiometers for?

3) On the xlr board, do I need to put two 6k8 resistors, the 10 ohm resister, and "RLoad" or can I leave those empty?

4) On the picture here:
Image
The "Out 0v" pad from the main board is not soldered to anything. Should this not go to the "Out 0v" on the XLR board? Or is it redundant?

5) Is regular 22 gauge hookup wire sufficient for carrying +V and wiring up the power jack and fuse?

6) Do you have a picture of diagram showing how the fuse and jack should be wired and/or grounded?

Thanks again. I feel like I am getting there.

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Re: BAN Build Thread

Post by Joe Malone »

mike wrote:Thanks Joe. That's all pretty clear. I've finished soldering the main board and now I just have wiring to do. I'm wondering if you can simplify it for me so I don't screw it up. Do you have a picture of one wired? It might be easier to figure it out from.

1) If the volume potentiometer pins are numbered as follows:
Image
Which pin is wired to the "gain pot" circuit pad spot closest to the edge of the PCB and which pin to the pad closer to the middle of the PCB?
Join 1 to 2 and wires to BAN go from 2 and 3 and can go either way
around.
2) What are the green 6 pinned potentiometers for?
Did you buy impedance pots ? If so the pot can be wired across the input XLR with 220ohms in series.
3) On the xlr board, do I need to put two 6k8 resistors, the 10 ohm resister, and "RLoad" or can I leave those empty?
NO only the XLR's and terminal blocks in the kit.
4) On the picture here:
Image
The "Out 0v" pad from the main board is not soldered to anything. Should this not go to the "Out 0v" on the XLR board? Or is it redundant?
Both 0v are connected so you only need to use one.
5) Is regular 22 gauge hookup wire sufficient for carrying +V and wiring up the power jack and fuse?
Yes
6) Do you have a picture of diagram showing how the fuse and jack should be wired and/or grounded?
Look at the Dual99v BA BAD build thread PDF's as all have the same power wiring.
Joe :-)
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mike
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Re: BAN Build Thread

Post by mike »

So I just finally finished my first channel and it is alive and working! I am getting normal sounding audio output when I plug a mic in and it seems to be behaving as any mic preamp should.

I am having trouble with the "alignment" process though. I initially tried to do it without my IC1/IC2 plugged in. At that stage I was getting 48.1 V at TP1, then with turning the trimmer next to that, I was able to get TP3 to 24.5 V. Turning the trimmer further (no matter how many times) would not allow me to go any further down on TP3 voltage. Next I was able to turn the other trimmer enough to at 1 K get the DC voltage across the volume pot down to 5 mV.

When I put the opamps in though all this changed. TP1 (on a different socket) is giving me 47.9 V (still fine), but TP3 is giving 34.8 V. If I turn the trimmer clockwise I can get this to go up from here, but not to go down any further than that when I turn it counterclockwise. It doesn't make any sense to me, and I'm worried about frying my OPA2604's fiddling with it while it's abnormally idling at ~35V.

Any idea what could be wrong? I've double/triple/quadruple checked all my soldering and parts and they all seem correct. As I said, the unit is passing sound which sounds overall fine. But I can't figure out how to get the TP2 down to ~24V now that the opamps are in. I am using a standard build with OPA2604 opamps. I used SSM2212 transistors with a SOIC-DIP8 adaptor (which seems to be doing fine since as I said the audio is coming through). All other parts were as you provided.

I'm wondering if my 10K trimpot is broken, since no matter how much I seem to turn it counterclockwise I can't get the resistance across the two pins closest towards the front panel to go higher than 6.6K. Also it seems to turn infinitely counterclockwise.

A further question regarding these trimmers: Are they infinite turn? I feel like I can turn them pretty much forever though maybe that's not actually true.

I am also having trouble determining how I should ground the chassis itself. Currently, the chassis conducts well with itself (ie. from a screw on one face to another screw on another face), but there is no conductance between the chassis and the black ground terminal of the DC power jack. I tried to resolve this by grinding off a bit of powder from the bottom panel with my dremel and soldering a ground cable from the black ground terminal of the DC power jack to it, but it does not stick well to the metal of the chassis, and if I remotely bump it this lead will come free. I am debating drilling a hole and putting a bolt/nut through the bottom of the unit that I can crimp a ground wire to. I just find it peculiar though that for an otherwise comprehensive project the grounding solution for the chassis is missing. Or am I missing something?
Last edited by mike on Mon Nov 17, 2014 12:53 pm, edited 1 time in total.

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