Tardigrade Build Thread

[Joe Malone]

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

Link to Palpigrade Build thread


Notes and Errata
First batch of pcbs have 1uF mono caps marked as C1 & C2 instead of correct C4 & C5.

PCB is simple build by overlay from lowest to highest.
1. Fit 8 x R2 100k & R3 & R4 10R and solder
2. Fit ZD1 & ZD2 18v zeners if needed for running on one 32v power rail. If using split +/-V rails do NOT fit.
3. Fit 8 x U1 IC 8 pin sockets with pin 1 closest to the DB25 and solder (If you fit one backwards it doesn't matter)
4. Fit 16 x C2,C3 47pF caps and solder
5. Fit 8 x R1 10k resistor array with pin 1 dot into the white box below R1 text
6. Fit 16 x C4,C5 1uF mono caps
7. Fit 8 x C1 1uF MKT caps
8. Fit 16 pin header with triangle to pin1 on the overlay and solder
9. Fit either DB25 or IDC26 pin header and solder
10. Fit 8 x Dual opamps with pin 1 dot towards the DB25 header as shown on the overlay.

Tardigrade pcb to scale
http://www.jlmaudio.com/Tardigrade/Trad ... 0scale.pdf

Tardigrade parts list
http://www.jlmaudio.com/Tardigrade/Tard ... 20list.pdf

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.

[living sounds]

Hi Joe,

looks like this is exactly what I need as balancing/output driving stage for my discrete multichannel DAC!

I'd like to use NE5532 (got old Signetics ones that I consider the best sounding op amp out there), any reason why they wouldn't work here? What can you expect WRT to SNR and THD?

Also, I might need more gain from it, is there any reason not to simply change the feedback resistors to a slightly higher value to get more gain?

The 1 uf decoupling caps are X7R ceramics I guess? What's the rationale behind using those instead of the usual combination of bigger electrolytics every 2-4 op amps (say 10uf) and 10 or 100 nf ceramics at the pins?

Thanks!

[Joe Malone]

Hi Joe,

looks like this is exactly what I need as balancing/output driving stage for my discrete multichannel DAC!

I'd like to use NE5532 (got old Signetics ones that I consider the best sounding op amp out there), any reason why they wouldn't work here? What can you expect WRT to SNR and THD?

The LME49720 & LM4562 have nV input current so will have no offset with the 100k input resistor. The bipolar input of NE5532 will make dc offset on the output of the tradigrade as there are no output caps. You can reduce this by lowering the input impedance from 100k to 10k and change 1uF to 10uF Non Polar. Or if connecting to a opamp unbalanced output directly with no offset, link out 1uF cap so unbalanced output and input direct connect so NE5532 doesn't offset. But it will never be a good offset wise as the LME49720 & LM4562.

Also, I might need more gain from it, is there any reason not to simply change the feedback resistors to a slightly higher value to get more gain?

Easy to get more gain. link the 12dB pads and add resistor across last 10k in the resistor SIL. But if using NE5532 again dc offset will need to be addressed. Instead of solder link for 12dB pads fit a 100uF 10v Non Polar cap across the pads so gain at DC is unity to minimise dc offset.

The 1 uf decoupling caps are X7R ceramics I guess? What's the rationale behind using those instead of the usual combination of bigger electrolytics every 2-4 op amps (say 10uf) and 10 or 100 nf ceramics at the pins?

Audio path Cap is 1uF MKT polyester not ceramic. If lower input impedance is need then cap needs to be increased to 10uF etc so Non Polar electro will be best. The ceramic mono caps are power rail decoupling to keep the opamps stable. PCB has 8uF of these per +/-rail for super low impedance power.

[living sounds]

Thanks Joe. I thought offset might be the problem. Since adding output caps is not really an option I guess I'll use modern op amps after all...

Audio path Cap is 1uF MKT polyester not ceramic. If lower input impedance is need then cap needs to be increased to 10uF etc so Non Polar electro will be best. The ceramic mono caps are power rail decoupling to keep the opamps stable. PCB has 8uF of these per +/-rail for super low impedance power.

Yes, I meant the PSU decoupling caps. I've never seen 1uf mono caps only for analog decoupling, usually it's bigger electrolytics (ideally not the low-ESR type, for better stability) + small ceramics (10-100nf).

[Joe Malone]

Thanks Joe. I thought offset might be the problem. Since adding output caps is not really an option I guess I'll use modern op amps after all...

Audio path Cap is 1uF MKT polyester not ceramic. If lower input impedance is need then cap needs to be increased to 10uF etc so Non Polar electro will be best. The ceramic mono caps are power rail decoupling to keep the opamps stable. PCB has 8uF of these per +/-rail for super low impedance power.

Yes, I meant the PSU decoupling caps. I've never seen 1uf mono caps only for analog decoupling, usually it's bigger electrolytics (ideally not the low-ESR type, for better stability) + small ceramics (10-100nf).

The 1uF mono cost about the same as the 0.1uF mono in bulk so we use them as you can get super low esr much closer to opamp power pins and few 1uF add up to electro size uF. So makes most unstable opamps super stable.

[living sounds]

The 1uF mono cost about the same as the 0.1uF mono in bulk so we use them as you can get super low esr much closer to opamp power pins and few 1uF add up to electro size uF. So makes most unstable opamps super stable.

Very interesting, thanks!

[survivorsound]

For gains between 6dB and 12dB, one would add a resistor across the gain pads, correct?

[Joe Malone]

For gains between 6dB and 12dB, one would add a resistor across the gain pads, correct?

Yes correct add 6k8 across the gain pads for 10dB.

[JakeRuben]

Hey joe quick question about parts. The 10k sil, is that bussed or iso?

[Joe Malone]

Hey joe quick question about parts. The 10k sil, is that bussed or iso?

4 Isolated resistors

[Jemplayer]

I keep having a problem where after about 15 min the sound goes out and is replaced by low-volume extremely distorted sound. This happens on all channels and I eventually burn out the chips. I did go several months before this happened last time, but now its like clockwork. I can unplug the power and when I plug it back in it resets.

Im changed to a new 12 volt wall wart made sure it was working with my multi meter.

I dont even know what else to look at.

[Joe Malone]

I keep having a problem where after about 15 min the sound goes out and is replaced by low-volume extremely distorted sound. This happens on all channels and I eventually burn out the chips. I did go several months before this happened last time, but now its like clockwork. I can unplug the power and when I plug it back in it resets.

Im changed to a new 12 volt wall wart made sure it was working with my multi meter.

I dont even know what else to look at.

Since all channel stop together it is the power supply. Or you do not have the correct zeners fitted. 12vdc is very low for the tradigrade to run on but if you have 2 x 6v2 zeners fitted to make it into +/-6v it may work. The tradigrade really wants a floating 24vdc regulated plug pack with 2 x 12v zeners fitted to make +/-12v.

Put up a top photo of the pcb and a photo of the 12v power supply label you are using so I can advice more on how to set it up right. Also let me know what Zener values you have fitted.

[Jemplayer]

Alright, thanks for the direction!

I have one of your Trex2 power supplies, I've got it set to 24v and have it connected to the + and - power input of the tardigrade. Is this right?

Im measuring 24 volts at the #4 and #8 pins of the chips with the negative hooked up to either 0v or negative.

Thanks for your help.

PXL_20240703_150707561.jpg

PXL_20240703_155745852.jpg

[Joe Malone]

Alright, thanks for the direction!

I have one of your Trex2 power supplies, I've got it set to 24v and have it connected to the + and - power input of the tardigrade. Is this right?

Im measuring 24 volts at the #4 and #8 pins of the chips with the negative hooked up to either 0v or negative.

Thanks for your help.
PXL_20240703_150707561.jpg
PXL_20240703_155745852.jpg

The photos are too out of focus to really see anything. But it looks like a 12vdc plug pack so cannot be 24v. Trex2 can only make lower power rails on its output and only positive so cannot run tradigrade. What Zener diodes did you fit? Do you have a photo of the wiring to and from the power supply trex2 and tradigrade. You need minimum a floating 24vdc plug pack and 2 x 12v zeners to make this work and no trex2

[Jemplayer]

Sorry for taking a sec to get back to you, 4th of July and all that for us ungrateful colonists.

So I ordered a 24v wall wart and some 12-volt zeiners. I think I have 18's installed.

I'm not following your rationale for how you power things. I'm just a basic level understanding of things, attach 12 volts to the circuit and be done with it, and the whole floating voltage thing I'm reading up on and trying to wrap my head about. Feeling I'm overcomplicating things in my mind.

I've done some reading and guessing that you are using the higher voltage and zeniers for voltage regulation to reduce ripple. Most common DC wall wart power supplies are floating, and you connect them to the + and - like normal. The 0v is ground and there if you need to ground the chassis or need a common ground for your system.

I don't understand what you mean about the Trex not being able to supply the correct amount of and type of power. What type of power is it designed to provide, again dc is dc in my mind.