Palpigrade Build Thread

[Joe Malone]

Palpigrade Build Thread
8 Channel balanced to unbalanced output driver kit.

Link to Tradigrade Build thread


Notes and Errata
R1 8PIN SIL is now 4 x 10k for balanced to unbalanced -6dB (originally 4 x 5k for balanced to unbalanced -12dB)
C2 & C3 are 39pF not 47pF. 39pF gives 200kHz flat bandwidth.
Extra 39pF can be added under pcb to improve CMRR over whole audio bandwidth.

PCB size is 55.25mm (2.18") x 77.35mm (3.05") with 4 x PCB mounting holes 47mm (1.85") x 56.7mm (2.23")
Or PCB can be mounted on the 2 x DB25 mounting bolts.

[downbeatstudio]

Hi there,
I just purchased some Palpigrade kits. I'm going to be leveraging the LME49720NA and adding them to a summing mixer that's running on +-24VDC. What zener diodes should I leverage to bump down the +-24VDC? Sorry I'm new to adding in zeners.

Thanks for the help!

[Joe Malone]

Hi there,
I just purchased some Palpigrade kits. I'm going to be leveraging the LME49720NA and adding them to a summing mixer that's running on +-24VDC. What zener diodes should I leverage to bump down the +-24VDC? Sorry I'm new to adding in zeners.

Thanks for the help!

Ok LME49720 is max +/-17vdc so you can fit 15v 1W or 16v 1W or 16v 1W in series with 1N4007 to make 16.8v.
8 x LME49720 use 80mA total idle current at +/-15v to +/-17v.

Make sure all 1W zeners are mounted in the air about 1cm or the height of the IDC header of the pcb as they run warm and also need at least 1cm lead length to achieve the 1W rating.

To drop the +/-24vdc add a 39R or 47ohm 1W carbon resistor in series with the +24v and -24v power on the way to the +V & -V of the Palpigrade

or you can replace the 2 x 10R on the palpigrade with 47R or 56ohm 1W which again would need to be mounted about 1cm off the pcb for cooling.

Make sure you have all LME49720 fitted with Zeners fitted & series resistors fitted before powering up.

[MrMesh]

Hi Joe, is there a parts list available for the Palpigrade yet?

[Joe Malone]

Hi Joe, is there a parts list available for the Palpigrade yet?

Palpigrade kit parts list

1 x Palpigrade PCB
8 x DIP8 IC socket
8 x 10k 4pin SIL
8 x 10k 8pin SIL
2 x 10R
8 x 100uF 10v Non Polar caps
16 x 1uF MONO caps
24 x 39pF ceramic caps
1 x 16 IDC header
1 x 3way terminal block
1 x DB25 pcb mount
1 x 26 way IDC header

Options

NO opamps
8 x LME49720
8 x LM4562

[Gersef]

Hi Joe,

two awesome Palpigrade kits arrived today for my summing box build.

Signal flow will be the Palpigrade followed by a passive summing network with 4 push/push switches to make the first 8 channels operating in mono instead of stereo pairs. Then the CAPI 2-ACA-BO and then to a balanced stereo output. No VUs, no trim or anything else, just plain summing and boosting.

All boards (Palpigrades and 2-ACA-BO) will be supplied with +/- 16V voltage from the PSU.

I am currently finalizing the PSU and am wondering what current I have to provide for this unit... From the Spec sheet provided by TE for the LME49720s I can see 10mA quiescent current (which you also mentioned above) and +/- 26mA as typical output current.

So would I have to calculate for the power supply to be able to provide the full 16 x (+/- 26mA) = +/- 416mA for this setup or less.
I have the choice between a transformer with 18V and 690 mA per secondary winding or going straight to 18V and 2 x 1,39A

Your insight and help would be highly appreciated.
Thank you very much for your support.

Best regards,
Jonas

[Joe Malone]

Hi Joe,

two awesome Palpigrade kits arrived today for my summing box build.

Signal flow will be the Palpigrade followed by a passive summing network with 4 push/push switches to make the first 8 channels operating in mono instead of stereo pairs. Then the CAPI 2-ACA-BO and then to a balanced stereo output. No VUs, no trim or anything else, just plain summing and boosting.

All boards (Palpigrades and 2-ACA-BO) will be supplied with +/- 16V voltage from the PSU.

I am currently finalizing the PSU and am wondering what current I have to provide for this unit... From the Spec sheet provided by TE for the LME49720s I can see 10mA quiescent current (which you also mentioned above) and +/- 26mA as typical output current.

So would I have to calculate for the power supply to be able to provide the full 16 x (+/- 26mA) = +/- 416mA for this setup or less.
I have the choice between a transformer with 18V and 690 mA per secondary winding or going straight to 18V and 2 x 1,39A

Your insight and help would be highly appreciated.
Thank you very much for your support.

Best regards,
Jonas

The idle current is usually all you need to allow for under low load summing setups. You can work this out easy by working out the lowest resistive load the opamp will see. If 10k summing resistors or higher the there is no extra load and the DIP8 opamp will basically run in full Class A for its output.

[petermelichar]

Hi Joe -

The Tardi/Palpi boards arrived quickly and I managed to build both in a few hours during the weekend just gone. Although I have soldered cable connections/studio cables, etc for probably close to 30 years, building/populating a PCB was a first this time around. Total noob in circuit building. Have to say it couldn't have been easier. Everything so nicely laid out and colour coded. At first I thought the build instructions are missing, but then I quickly realised that the pictures on top of either build tread have all the info you need.

The only question I'd like to double check on is the 'direction' of the zeners. As you will recall, I am going to build an enclosure to run 1xTardi and 1xPalpi from a single SMPS turned down to 36V. I checked, and it applies to both boards, in terms of amount of zeners (2xper board) and position - if I have either board is in front of me so that the JLM logo and the product logo are bottom LHS, and the -V,0,+V block is bottom RHS, which way around would the zeners go ? Anode in 'left hand side' holes and Cathode in 'right hand side' holes or other way around ?

I just realised that now I am a registered forum member there are two further pictures/attachments I can see below the diagrams on the top of the thread though I'm afraid my electronics symbol knowledge is not 100%, although I can sort of see which way around the zeners are mounted from that, just not 100% on how to 'translate' onto the actual PCB.

I read in an earlier reply that you recommended to mount the zeners 1cm-1.5cm off the PCB for cooling, is that correct ?

Many thanks in advance,
Peter

[Joe Malone]

Hi Peter
Great to hear you found the build easy.
The stripe on the end of the zener diode lines up with the white stripe on the pcb overlay.
Yes it is best to mount the zeners up off the pcb as they can run a bit hot.
Check the power supply is set to 36 to 37vdc before connecting. The power supply +V goes to +V on each pcb. And -V to -V on the pcbs. The Ground on the power supply goes to 0v. All pcbs need the 18v zeners fitted.

[petermelichar]

Hi Peter
Great to hear you found the build easy.
The stripe on the end of the zener diode lines up with the white stripe on the pcb overlay.
Yes it is best to mount the zeners up off the pcb as they can run a bit hot.
Check the power supply is set to 36 to 37vdc before connecting. The power supply +V goes to +V on each pcb. And -V to -V on the pcbs. The Ground on the power supply goes to 0v. All pcbs need the 18v zeners fitted.

Good morning, many thanks, that's easy to get done, get to it right away. Was definitely going to double check the PSU also, just in case. Assume if I somehow manage to get too much power or the power the wrong way around I'll fry the OpAmps...

If I understood correctly re earthing scheme:
- Mains Earth >> PSU ground >> chassis ground
- 0V on the Tardi >> chassis ground
- 0V on the palpi >> chassis ground
Three earth wires meeting on the same chassis ground lug

Or would it be better practice to go:
- Mains Earth >> PSU ground
- 0V on the Tardi >> PSU ground
- 0V on the Palpi >> PSU ground

and then PSU ground >> chassis ground
for just one singele chassis <> PSU connection wire ?

Or am I overthinking this

Have (black/red) 16AWG silicone wire (with spec to withstand 12A / 600V) for the V +/- L/N connections and 2.5mm solid core copper for the earth connections.

I will report back once I have everything in place in the enclosure , have my Dremel at the ready. Bank holiday weekend coming up here in UK.

All the best,
Peter

[Joe Malone]

Hi Peter
Great to hear you found the build easy.
The stripe on the end of the zener diode lines up with the white stripe on the pcb overlay.
Yes it is best to mount the zeners up off the pcb as they can run a bit hot.
Check the power supply is set to 36 to 37vdc before connecting. The power supply +V goes to +V on each pcb. And -V to -V on the pcbs. The Ground on the power supply goes to 0v. All pcbs need the 18v zeners fitted.

Good morning, many thanks, that's easy to get done, get to it right away. Was definitely going to double check the PSU also, just in case. Assume if I somehow manage to get too much power or the power the wrong way around I'll fry the OpAmps...

If I understood correctly re earthing scheme:
- Mains Earth >> PSU ground >> chassis ground
- 0V on the Tardi >> chassis ground
- 0V on the palpi >> chassis ground
Three earth wires meeting on the same chassis ground lug

Or would it be better practice to go:
- Mains Earth >> PSU ground
- 0V on the Tardi >> PSU ground
- 0V on the Palpi >> PSU ground

and then PSU ground >> chassis ground
for just one singele chassis <> PSU connection wire ?

Or am I overthinking this

Have (black/red) 16AWG silicone wire (with spec to withstand 12A / 600V) for the V +/- L/N connections and 2.5mm solid core copper for the earth connections.

I will report back once I have everything in place in the enclosure , have my Dremel at the ready. Bank holiday weekend coming up here in UK.

All the best,
Peter

Mains ground always has to go to chassis first and then you can use the chassis point to star the power ground and audio ground if you want.

But as long as all the audio and power grounds are all connected you will be fine.

[Gersef]

Hi Joe,

I finally have all parts of my summing amp built, wired and running. +/-16V supply to all PCBs is stable, the CAPI 2 ACA Bo PCB is working properly and amplification is done properly as well.

I have one issue with one of the Palpigrade PCBs being that the Opamps run reeeeaaaallllyy hot almost immediately and there is actually an audible noise (like a 'beeeeeeep') coming from the board...

On the other board the opamps run warm quickly but not really hot to the touch. I assume this is normal and due to Class A operation?

What in the world could have gone wrong with the other board?

Thank you very much for your time and support!

[Gersef]

Ooooookay...... Stupid me...
I had the ribbon cables that go to my summing board clamped in the wrong direction.
So all signals went to ground and all ground wires were in the signal path... Fixed !

[Joe Malone]

Ooooookay...... Stupid me...
I had the ribbon cables that go to my summing board clamped in the wrong direction.
So all signals went to ground and all ground wires were in the signal path... Fixed !

OK cool great to hear you worked out the problem.

With ribbon cables

If using the grey cable with red stripe we always put the red strip to pin 1 end which is the end with the Triangle symbol on the connectors.

if using the coloured rainbow cable we always put the brown wire to pin 1 end which is the end with the Triangle symbol on the connectors.

[Gersef]

Hi Joe,

Wanted to share the finished Summing Amp with you.
This unit is absolutely dead quiet, no noise floor, amazing.
The difference in output voltage between the 16 channels is within +/-0,0015V.
The sound is really nice and it works beautifully.

The only not so nice looking parts are the ribbon cables as they are right now, but doesn‘t affect sound so who cares…

All of that could not have been achieved without your Palpigrade kits.
So a really cool little kit that is really fantastic quality.
Good thing I found that in your shop when I decided to build a summing unit.

And luckily it came with a sticker I put on the top of the box (above the input modules).

I am looking forward to the countless hours of fun I will have with this summing box.

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