Palpigrade Build Thread

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Joe Malone
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Palpigrade Build Thread

Post by 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.

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Joe :-)
JLM Audio
Capturing Audio without Injury

downbeatstudio
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Joined: Mon Jul 06, 2020 11:01 am

Re: Palpigrade Build Thread

Post by 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!

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Re: Palpigrade Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Mon Jul 06, 2020 11:31 am
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.
Joe :-)
JLM Audio
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MrMesh
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Re: Palpigrade Build Thread

Post by MrMesh »

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

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Re: Palpigrade Build Thread

Post by Joe Malone »

MrMesh wrote:
Fri Nov 20, 2020 7:59 pm
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
Joe :-)
JLM Audio
Capturing Audio without Injury

Gersef
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Joined: Mon Mar 08, 2021 9:35 pm

Re: Palpigrade Build Thread

Post by 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

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Re: Palpigrade Build Thread

Post by Joe Malone »

Gersef wrote:
Thu Mar 11, 2021 10:19 pm
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.
Joe :-)
JLM Audio
Capturing Audio without Injury

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