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Old 26th September 2021, 11:59 PM   #251
xrk971 is offline xrk971  United States
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The power trafo is Antek 400VA, and Antek's run on the large side. The custom EI balanced choke is wound on a nominal 600VA core. It is large (11lbs of grain oriented silicon steel (GOSS) wound with bifilar 14ga copper magnet wire for nominal 0.5ohm DCR and 60mH at 10kHz) and oversized on purpose to make sure it doesn't saturate.
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Old 27th September 2021, 12:50 PM   #252
xrk971 is offline xrk971  United States
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A careful study of the source of noise/buzz/hum on SuSyLu was performed in flat plank amp mode. It seems adding a second SLB helps. The location or proximity of the toroidal trafo to the inductor did not matter. The biggest culprit is the ground loop caused by connecting the PSU ground pin at the peripheral of the layout star hub ground. Simply moving that to the physical star hub ground (where speaker out was) solved the majority of the ground loop. The amp is now silent again in this mode flattened, two SLBs, and ground pin location moved. Reassembling to a box may change things die to EMI with other components.

Trafo far apart from inductor reads 0.1mV rms:
SuSyLu Where Are You?-cd9b6127-ef7c-471a-be9d-eaa7e4b2b420-jpg

Trafos close together reads the same:
SuSyLu Where Are You?-14b2d2e1-f9ff-454b-9fe8-70783d5b559a-jpg

Move the SLB ground pin to the star hub location:
SuSyLu Where Are You?-a179ed4a-1b0c-4d1a-ae4b-7db3e8475b10-jpeg

Noise with ground moved to star hub now is quiet at 0.1mV rms (it was in 1.4mV range before):
SuSyLu Where Are You?-ee17d72a-d1ba-4d0c-9bc3-189522763fc8-jpeg

The Fluke 101 in mV AC mode has unique ability to show what we hear as mains induced hum/buzz/ground loops. If it reads 0.1mV the speakers are silent with ears pressed to cone. I had speakers connected simultaneously in order to debug source of noise as I moved things around. Good news is that location of trafo near inductor did not matter. I was able to move them father apart by more 1in, if that matters.
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Last edited by xrk971; 27th September 2021 at 12:54 PM.
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Old 30th September 2021, 02:35 AM   #253
xrk971 is offline xrk971  United States
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On the bench tonight is a test of the SuSyLu with a basic silicon diode bridge and CRC power supply. 15,000uF // 2x 0.33R 3W in parallel // 15,000uF per leg. With the Antek AS-4224 it’s getting 30v at 3.1A. The amp output at the speaker is pretty quiet at 0.2mV rms. No audible hum with ear 2in away from the speaker cone.

However, the moment I connect the balanced preamp input from the TRS jack, there is ground loop hum. Continuing to debug the ground loop. But it does look like the balanced amp has decent PSRR as a standard CRC appears to be quiet enough.

-0922b854-0252-46a1-a9e5-d2d9d8de94cc-jpeg

-9da5743a-d5f0-45ad-b945-34b078f04c09-jpeg

-c71e8563-da40-4067-ae12-86c3445a3dd2-jpeg
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File Type: jpeg 9DA5743A-D5F0-45AD-B945-34B078F04C09.jpeg (862.4 KB, 307 views)
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Old 1st October 2021, 01:32 PM   #254
xrk971 is offline xrk971  United States
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On the bench last night Sept 30, 2021:

I finally solved the ground loop on the SuSyLu amp. The balanced input nature of the amps means that the output stages need to be driven by a driver stage that has low impedance ground between each opamp (ideally on same PCB). Since the drivers are on the output stage boards as this was adapted from the single ended LuFo, the way to do this is to put a big low impedance ground strap between the two ground bolts on the HV OPA454 daughter boards. I used two 16ga silicone RC race car wires for this. It worked! With a CRC PSU, the hum is gone and output shows 0.2mV rms on Fluke 101. Residual noise is probably just CRC ripple and not audible if ears more than 4-5in from speaker cone.

Click the image to open in full size.

Click the image to open in full size.
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Old 1st October 2021, 02:03 PM   #255
poseidonsvoice is offline poseidonsvoice  United States
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When you have a time, your cool diagrams illustrating this would be useful!

Thanks again X for sharing in your diyaudio adventures!

Best,
Anand.
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Old 1st October 2021, 02:11 PM   #256
nigelwright7557 is offline nigelwright7557  United Kingdom
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Been working on a DCC booster for model railways.
It takes in DCC signal and outputs same signal unless a short is detected.
If short detected it lights an LED, makes output signal o/c and waits for reset button to be pressed.
The signal in and out must be exactly aligned as the track will short between them as the loco cross the separator joint.
Seems simple enough.
I started by using a PIC16f753 but it wasnt switching fast enough.
So tried a PIC32mx230 50MHz and that was fine.

It has 2 uses, one is for driving accessories that work off DCC.
And powering remote track.
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Old 1st October 2021, 06:04 PM   #257
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by poseidonsvoice View Post
When you have a time, your cool diagrams illustrating this would be useful!

Thanks again X for sharing in your diyaudio adventures!

Best,
Anand.
Hi Anand,
Here is how it is currently hooked up. I am finding out that ideally, the balanced TRS jack shield connection should go to chassis ground and not signal ground as I have it connected. The green ground strap between the two daughterboards was the key thing that fixed the hum.

-1afd9659-ff90-4e4e-94e7-18074f36dd49-jpg
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Old 1st October 2021, 09:53 PM   #258
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by nigelwright7557 View Post
Been working on a DCC booster for model railways.
It takes in DCC signal and outputs same signal unless a short is detected.
If short detected it lights an LED, makes output signal o/c and waits for reset button to be pressed.
The signal in and out must be exactly aligned as the track will short between them as the loco cross the separator joint.
Seems simple enough.
I started by using a PIC16f753 but it wasnt switching fast enough.
So tried a PIC32mx230 50MHz and that was fine.

It has 2 uses, one is for driving accessories that work off DCC.
And powering remote track.
Hi Nigel,
I made a DCC controller using Arduino and a standard “Motor Shield”. Software is all online of course. It worked. But in the end, I plunked down $90 for a prebuilt DCC controller all boxed and ready to use. Much simpler - no chassis or PSU to build. Plus, my 6yr old (at the time) could use it easily.m
There is a huge following of people programming $1 ATTtiny286 (DIP8 RISC MCU’s) as Arduino compatible controllers for doing all sorts of model RR functions for switching tracks, lifting gates, operating draw bridges or blinking custom lights, etc along the track. All self-running once programmed.
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Last edited by xrk971; 1st October 2021 at 09:55 PM.
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Old 2nd October 2021, 04:43 AM   #259
xrk971 is offline xrk971  United States
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On the bench tonight Oct 1, 2021 is adding a CRCRC power supply to the SusyLu amp. This reduced the supply ripple down to 50mV rms from 100mV rms, however, the amp has pretty good PSRR so the output noise is still 0.2mV rms. I also added my Gen2 SSR DC speaker protection module which can be used with BTL amps where both speaker outputs are "live".

SuSyLu Where Are You?-susylu-crcrc-ssr-photo-03-jpg

SuSyLu Where Are You?-susylu-crcrc-ssr-closeup-photo-04-jpg

SuSyLu Where Are You?-susylu-crcrc-closeup-photo-02-jpg
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Old 3rd October 2021, 12:49 AM   #260
xrk971 is offline xrk971  United States
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Sound Clips of SuSyLu in main system with a real DAC.

https://www.diyaudio.com/forums/atta...1&d=1633221958
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