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JP

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Fair progress on the printer. Held up for a week waiting on replacement parts due to numerous quality issues.


IMG_1455.jpeg
 

egellings

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I have that R & S scopeski. It's a honey of an oscilloscope. I got the 350MHz option with mine.
 
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pma

pma

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Fixtures for capacitor distortion measurements


elyt12_thd_test.jpg


bipolar_vs_MKT.jpg



class D testing
square_Dtest.jpg
 
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pma

pma

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Measuring Hypex NC252MP in the bridged mode. Coming very soon :)

NC252MP_bridged_distortion_measurement.JPG


NC252MP_BTL_load.JPG


The new thread with measurements:

 
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pma

pma

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venquessa

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This in on the bench. It's got to that stage where it works enough to wire it up and use it. So it's harder to work on it.

It's a DIY digital audio hub for my desk. Somewhere to connect various PCs, headsets, speakers, headphone amps, have a centralised, mix, route and EQ.

Current core is an STM32H7 MCU with 90% custom DSP software the other 10% was nicked off Phil's Lab.

In to out latency at 96kHz is about 20 us, including mix, route and EQ. EQ is (currently) 7 basic IIR peak filters (14 technically, 7L 7R)
 

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dualazmak

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Interesting thread!

Last year, large glass-face VU meters (fully compatible with IEC 60268-17) have been occupying my workbench quite a while.
WS00005258.JPG


Please refer to here and here for the details.
 
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pma

pma

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That looks nice @pma. Is that your design and build?

Marantz is not :), the rest described below:


 

solderdude

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I once converted this Philips AG9016 2W stereo tube amp to a tube-pre amp.
I could switch between it and a SS pre-amp.
Couldn't really tell them apart except for hum, noise level and the time it took to work after it was switched on, so while fun for a while returned to the good old op-amp for practical reasons.
Surprisingly the potmeters and input switch still worked fine despite its age.
(DIN input and output so needed conversion cables. Still have it... somewhere.

tubepre.jpg

It is not on my workbench at the moment but on the attic somewhere.
 
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pma

pma

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More fun - tubepreamp +poweramp from this post and the distortion measurements of that combo:

Tubepre+A250W4R_thdnlevel_1k_4R%.png


Tubepre+A250W4R_thdfreq_10W_4R.png

Distortion is absolutely dominated by H2.

Someone might think that distortion like this would be audible, but it is not in the blind, level matched test against the direct DAC-amp path.
 

ahofer

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More fun - tubepreamp +poweramp from this post and the distortion measurements of that combo:

View attachment 276874

View attachment 276875

Someone might think that distortion like this would be audible, but it is not in the blind, level matched test against the direct DAC-amp path.
Well, having done the distortion detection tests online, im not too surprised. Lower level harmonics?
 
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Sal1950

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I'm finally getting around to replacing the innards of my main music server box that got fried by a lightning strike last fall..
Not a brand new board but I got a friend that's a gamer and upgrades his box every few years. Couldn't pass by the deal.
I paid the shipping only for the board and i7 cpu. I've got it all up and running and in the system now, smoking fast with
my Linux OS, Delivers 4k Video w/Atmos sound without a blink. Yippee.

IMG_0026.JPG
 
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pma

pma

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Well, having done the distortion detection tests online, im not too surprised. Lower level harmonics?

Yes, of course. H2 is dominating up to the knee above 200W, all else negligible with respect to H2 and noise.

Tubepre+A250W4R_thdnlevel_1k_4R_H2-6.png
 

venquessa

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Too much. In the cardboard box is the DSP (so I can protect it from me being an idiot). It has it's new power supply (in the unshrunk shrink tube) as the onPCB regulator died. Along side the UI dev bed. Which as you can see from the random gibberish "volume" value is coming along really well (sarc).

On the left is my complete mess of 12V/5V USB and DC wiring running off that little power supply (coming from the solar LFP 12V garage system)... and the 100Ah Marine lead acid "buffer battery" on the floor... which is about to be capacity tested this weekend with the colourful little gizmo. Out of shot the internet router and network switch are running off said lead acid. It itself is a temp surrogate for a new "Audio lab battery", a 6S LiFePO4 battery, which I will multi-tap for a range of voltages including -10+10.

My little blue 1.5 Watt headphone amp glowing nicely.

(Yes, that feed does come in through the wall via a 6mm cable ... and I tap it with croc clips. It's 12V FFS. It's fused at 15A, if the cat shorts it, the fuse will blow.)

EDIT: ON protecting the thing from "me". This week I am healing a nasty blister a whole in my pocket and feeling dumb. I set said new power supply on top of the MCU board. It was powered off of course. Not that dumb. Until later on, when I switch it on and didn't immediately play any music. So I didn't notice it was shorted. When I did notice I lifted the PSU board off the MCU and immediately dropped it because of how hot it was. Being even more dumb I then put my finger on the MCU itself to see how hot it was. It now bears the tattoo of my fingerprint and I lost about 1mm of the skin off my finger . I figure it was just below glowing orange 300+C. £40 replacement.... already in stock.
Not two nights later I put my multimeter into the mains outlet of an inverter on the wrong setting and fried it. £100 replacement. Meter "should" have survived it, but due to design/wear and tear it failed to.
IMG_20230405_182351084_HDR.jpg

EDIT: The MCU in it's shorted state was consuming 1.6A at 12V. Most of that heat seems to have been centred in the exact point I touched.
 
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Doodski

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@venquessa. I have worked extensively with 12V high current batteries like the battery you have on your floor in the house. I've personally witnesses maybe a dozen explosions caused by lead acid batteries. The explosions where in a battery shop that I used to manage and several where in a huge industrial building and so the roof, walls and windows where never damaged but it scared the heck out of the staff. I suggest you get that battery out of the house to avoid some sort of fire hazard or explosion potential. It's really dangerous.
 
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