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PDX DAC project


Guest Benjet

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2 minutes ago, scumbag said:

One wee problem, under the purchase section it reads - "EDIT: The offer is closed, and payment buttons are removed.""

 

Hence the 'ask Pedja' bit. I 'asked Pedja' and got lucky, now @zenelectro has put one in a box for me with nice power, inputs and outputs. No you can't have it :D 

 

Seriously Pedja is super nice to deal with and even if there was a wait I'd hold out. A quick search on phase noise vs oscillator frequency will confirm it's worth it.

 

No harm putting a WTB out on diyaudio either, FWIW.

Edited by rmpfyf
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28 minutes ago, rmpfyf said:

 

Hence the 'ask Pedja' bit. I 'asked Pedja' and got lucky, now @zenelectro has put one in a box for me with nice power, inputs and outputs. No you can't have it :D 

 

Seriously Pedja is super nice to deal with and even if there was a wait I'd hold out. A quick search on phase noise vs oscillator frequency will confirm it's worth it.

 

No harm putting a WTB out on diyaudio either, FWIW.

Well put! :thumb:

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Hi Ben,

yes I would try 12k for the plate resistors & then remeasure the voltage across each tube section - cathode to plate

The tube heaters are elevated other wise the top section of the SRPP stage will have too high of a voltage difference between the heaters & the cathode. The tube heater voltage elevation is done with a simple voltage divider. Just two resistors in series from the HT rail to ground. You probably don’t even need to change what's in place as that should still be within the voltage acceptance range. 

 

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2 hours ago, rmpfyf said:

 

Hence the 'ask Pedja' bit. I 'asked Pedja' and got lucky, now @zenelectro has put one in a box for me with nice power, inputs and outputs. No you can't have it :D 

 

Seriously Pedja is super nice to deal with and even if there was a wait I'd hold out. A quick search on phase noise vs oscillator frequency will confirm it's worth it.

 

No harm putting a WTB out on diyaudio either, FWIW.

Can I ask what you were charged for the board? 

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10 minutes ago, scumbag said:

Can I ask what you were charged for the board? 

 

Came in around AUD$265 delivered at the time. This is around 2.5x an Amanero, and it's more than 2.5x better. So bargain. The 'customers' bugging Pedja to prove out 384kHz support were myself, @zenelectro and @rawl99.

 

Compares favourably with iancanada's kit with is >AUD$400 plus clocks plus more complex power supply plus USB interface.

 

@zenelectro is actually kitting me out one of each, pretty soon we'll be able to compare. He's very much probably in a better position to give thoughts on this and others, having done the JLsounds, Audial, iancanada, Amanero, others etc... and a lot of work on oscillator selection. 

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You may have missed a quote from [mention=110074]zenelectro[/mention] - the new i2soverUSB is FPGA-based (like an Amanero) and that's going to limit clocking accuracy irrespective of the oscillator used. 
 
You'll probably find better phase performance for 22/24 (or so) Mhz pairs in the NDK NZ2520SDA range; the question then is can you find a solution that'll give you genuine simultaneous performance out of lower-speed clocks (i.e. 384kHz) - this isn't possible with I2S - look at the bitstream. 
 
Pedja Rogic's USB board is one such contender, if he's got stock I'd ask. From memory it can be configured to spit out data for PCM DAC ICs, I could be wrong. Otherwise you're stuck at the aforementioned (double) clock speeds for kits  that are I2S native, and iancanada's kit is about as good as it gets - though there's a few boards involved and it ain't cheap. 
 
I would move on from the Crystek's. 
 
Seriously - you want this one https://www.audialonline.com/topics/usb-to-simultaneous-data-or-i2s-converter-series-2/ - get in touch with Pedja.

Email sent, fingers crosses ?he’ll be able to help. Otherwise I might go down the original path of the iancanada solution. Bit more expensive and complicated, but ticks every box. I’ll be over in Toronto later this year, so I might pop in and see him.
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Guest Benjet
 
You may have missed a quote from [mention=110074]zenelectro[/mention] - the new i2soverUSB is FPGA-based (like an Amanero) and that's going to limit clocking accuracy irrespective of the oscillator used. 
 
You'll probably find better phase performance for 22/24 (or so) Mhz pairs in the NDK NZ2520SDA range; the question then is can you find a solution that'll give you genuine simultaneous performance out of lower-speed clocks (i.e. 384kHz) - this isn't possible with I2S - look at the bitstream. 
 
Pedja Rogic's USB board is one such contender, if he's got stock I'd ask. From memory it can be configured to spit out data for PCM DAC ICs, I could be wrong. Otherwise you're stuck at the aforementioned (double) clock speeds for kits  that are I2S native, and iancanada's kit is about as good as it gets - though there's a few boards involved and it ain't cheap. 
 
I would move on from the Crystek's. 
 
Seriously - you want this one https://www.audialonline.com/topics/usb-to-simultaneous-data-or-i2s-converter-series-2/ - get in touch with Pedja.

Found a series 1 Audial board. Will that do the trick?

Thanks,

Ben
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Guest rmpfyf
1 minute ago, Benjet said:


Found a series 1 Audial board. Will that do the trick?

Thanks,

Ben

 

Not likely - again ask Pedja. You will need a firmware tweak on the series 2 to run 384kHz on the PCM DAC IC'S you have.

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Guest Benjet
 
Not likely - again ask Pedja. You will need a firmware tweak on the series 2 to run 384kHz on the PCM DAC IC'S you have.

Good news, the series 1 board will do 384kHz as it had the 22.5792MHz/24.576MHz clocks. Only differences between the series is the series 2 has output buffers to drive terminated lines and also has the provision to power the USB side locally. Two things I can do without.

Board ordered [emoji4]
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Guest rmpfyf
6 minutes ago, Benjet said:


Good news, the series 1 board will do 384kHz as it had the 22.5792MHz/24.576MHz clocks. Only differences between the series is the series 2 has output buffers to drive terminated lines and also has the provision to power the USB side locally. Two things I can do without.

Board ordered emoji4.png

 

If you have Pedja's blessing on the 1704, go for it :) (redundant, you went for it!) There are a few places you can order yourself the 'last word' in clocks too if you want to upgrade. 

 

I'd power the USB locally but really you can do that with a split cable or a nicer USB card or some other trickery. 

 

Nice little rig you're putting together. 

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Guest Benjet
 
If you have Pedja's blessing on the 1704, go for it [emoji4] (redundant, you went for it!) There are a few places you can order yourself the 'last word' in clocks too if you want to upgrade. 
 
I'd power the USB locally but really you can do that with a split cable or a nicer USB card or some other trickery. 
 
Nice little rig you're putting together. 

It’s shaping up pretty nicely[emoji106]
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5 hours ago, Benjet said:


Good news, the series 1 board will do 384kHz as it had the 22.5792MHz/24.576MHz clocks. Only differences between the series is the series 2 has output buffers to drive terminated lines and also has the provision to power the USB side locally. Two things I can do without.

Board ordered emoji4.png

Just a quick addition:

 

The ultimate performance of your DAC will be highly dependent on how you implement the digital side of things.

It's all about keeping noise out, distances short, ground impedance low, ground planes where possible etc etc. 

 

A 100 MHz Cro is also your friend.  

 

T

 

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Guest Benjet
Just a quick addition:
 
The ultimate performance of your DAC will be highly dependent on how you implement the digital side of things.
It's all about keeping noise out, distances short, ground impedance low, ground planes where possible etc etc. 
 
A 100 MHz Cro is also your friend.  
 
T
 

IMG_3761.jpgIMG_3626.jpg
Will get a chance to use some of these [emoji106]
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Guest Benjet
7904 / 500 Meg will do it! 
 
Are there any modules you haven't got?  [emoji4]
 
 
 
 
 
 

There’s a couple I haven’t got yet [emoji6]
Also got a 2335 as a backup.
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Guest Muon N'

Cool, I hadn't noticed the PCB is actually more so constructed in a point to point fashion, at least in part. Was this done when replacing parts?

 

Looks like traces in some places and wired in others.

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Guest Benjet
Cool, I hadn't noticed the PCB is actually more so constructed in a point to point fashion, at least in part. Was this done when replacing parts?
 
Looks like traces in some places and wired in others.

Think she’s had a few mods over the years. I’ll probably be adding a couple myself.
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Guest Benjet
Are those Siemens A frames. Can't quite tell from the angle of the photo.

Hope so, they were the ones from eBay you told me about ?What should I be looking for?
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Guest scumbag
31 minutes ago, Benjet said:


Hope so, they were the ones from eBay you told me about ?What should I be looking for?

The 2nd from the left shows it well. The 2 strips have a vertical section then turn in diagonally. There seem to be minor variations in the proportions.

 

s-l1600.jpg

Edited by scumbag
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