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If 70s uses digital volume control (by reducing the bit length) before signal reaches DACs it is not optimal - PCM5102a is a low cost solution and for low level music could be resolution degradation, so it is no no for me as the pre-amp solution.

And what about analog inputs - are they digitised/sampled? I think that there is some analog volume chip on the side pcb between upper and lower pcb, or on the lower pcb next to the RCA pre-outs.

Great teardown tlr, but do you know what volume control chip is used?

Nice test and results. What about reactive loads test?

What is your external DAC? Is it miniDSP? If so, I suggest to check miniDSP settings... P.S.: MCK is 256xfs - in this case 12,288 MHz (for fs 48 kHz).

Try to check LRCK (fs) signal on yellow wire - should be like on the pic (it is from AVR-X3400H, but I think it is the same as 3600): Or you can measure frequency of LRCK by multimeter - should be 96 kHz (or 48 kHz), I suppose. Edit: The best is to measure it on the WM8805 on your board...

I would check the audio interface formats (and MCLK frequency) - they should be the same (see data sheets of the AK4458 and WM8805 and check the appropriate chip pins): Your board is here:

Next possible solution could be HDMI multichannel extractor to 4 x I2S and 4 x I2S to AES/EBU interface. Than you can use direct connection via AES/EBU to the okto dac8 PRO. HDMI multichannel to I2S extractor: https://vi.aliexpress.com/item/33031920347.html I2S to AES/EBU interface (4x)>...

Hi MAB, I am facing up the same problem with my Linkwitz Orion tweeters - they are more than 20 years old and sound "dull" without the life and highs. Initially, I was looking for some xover or amp problem, but it seems that dry ferrofluid is the reason (I did not opened the tweeters yet). So...

Any chance to see the PowerCube/reactive load tests?

Nice work, but all of the THD+N/SINAD numbers are a little-bit "optimistic" - when you use AES17 notch option in Multitone SW the analyser excludes lot of noise from the calculation (see the "skirt" around 1 kHz signal in the picture) which is not correct. See the noise number in the table - it...

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Here is a nice LM1875 implementation as a composit amp: https://www.kaltecs.com/2-x-32w-lm1875-ultra-low-distortion-amplifier-kit/ But I have no experience with it. Martin

Nice review Amir, but again Power Cube is not correct - 41Vrms into 4 Ohm gives 420W... It is 200W more than you have measured! There has to be a bug in the AP script. Martin

In the Power Cube I see 60 Vrms into the 4 Ohm - is it correct? Then maximum power should be 60*60/4 = 900 W!

Thanx, I will try. But it is too early if contacts need cleanning... And it is hard to detect this problem - to check/recalibrate after each DIP change is not very easy.

After 7 months of occasional use the DIP switches in my Cosmos ADC in left channel start to loose contact - I am looking for spare one. This should be good as replacement: https://www.mouser.sk/ProductDetail/Wurth-Elektronik/416131160812?qs=2kOmHSv6VfSn2jguIjHTtg== Martin P.S.: 1000 Cycles...

How about THD and THD+N vs. power at 20 Hz/4ohm?

Nice review, but I did not find the way how Scaler indicate gain used - in manual and autoranger mode. There are 16 gains and for dBu/dBV/V scale you should know what gain is used.

Very nice, but I suggest to switch level in your charts to dBr (not dBFS) - Multitone Analyzer calculates THD relative to FS, therefore when your fundamental is lower than 0 dBFS, THD is not correct. In your case is THD about 10 dB lower then in reality...