DIY Front End 2022

I finished my FE2022 as a line stage, I had most of the parts in-stock except the power supply and capacitors. I had 2 matched quads of Toshiba 2SK369 JFET's, which I'm using for Q1 & Q2. I used sockets on Q1, Q2, R3, R4 and C6. R14 was omitted, R13 is 10 ohms and R6 is 750 ohms. I had a 4 pole 24 step Vishay Dale resistor 50K volume control as I wanted the XLR inputs for my DAC and FET-10Pe phono. I had an e-Bay relay input selector, it is fully balanced with 8 relays for the 4 inputs.

Question about this front end kit when using a 48v Single V+ switching PSU.

I am getting a high pitch squealing sound with the larger 48V,

I had the same problem when I used a Mean Well LRS-75-48 SMPS, I tried 33pF 48pF, 65pF & 100pF on C6 with no change. I swapped out the 48v SMPS with a 36V Mean Well LRS-75-36 SMPS with the same results, C6 made no difference. I then tried a 24v linear supply and the preamp worked and sounds great. I ended up using an ANTEK 50VA 48V single supply linear power supply and all is well.

It's been playing music for a couple of days so far, I'll move it to the music room next weekend.
 

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Let me ask, does the supply have an AC plug ground connection?

Yes, the IEC ground was attached to the chassis via the rectifier hold down bolt. The SMPS ground was wired to the - pin on the rectifier along with a jumper to the + pin with a CL-60. Here is a picture of the SMPS and the preamp with the SMPS installed.

There was no hum, just a very loud squeal at full volume to the amp (volume control was at zero).
 

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Have you mentioned where you got your chassis? eBay? And did it come with the pack panel holes you needed?

Thank you. Yes, the enclosure I found on eBay, it had all the holes and knobs for the front panel. It was for an XLR output and RCA output, so I found plastic plugs for the RCA output holes and used the XLR holes for RCA output. The inputs were just what I wanted, I did have to drill holes for the LED's on the input selector on the front panel.
 
Let me ask, does the supply have an AC plug ground connection? If so you have the potential for a ground loop, depending on what other component shares that connection.

I hooked up the Mean Well LRS-75-36 (single rail 36vdc) SMPS to the FE2022 boards with a 10K resistor on the output and input shorted.

Here is the scope patterns and scope settings using a X1 probe. Not sure if this helps, it was how I tested the FE2022 using the 36v and 48v SMPS and then the 48v linear supply so I didn't have to subject the amp and speakers to the noise.
 

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The first shot shows multiple approximately 0.2Vpp at 80kHz riding on a lower frequency, and there are also other lower frequencies visible.
This only shows up when the SMPS powers the FE2022, it's been playing music all week with no hick-ups using the 48v linear supply.

I forgot to mention, the SMPS ground was connected to an outside IEC connector powered by the mains in my workroom. There is always a sight buzz if I don't power recent builds with an isolation transformer.
 
Yes, the IEC ground was attached to the chassis via the rectifier hold down bolt. The SMPS ground was wired to the - pin on the rectifier along with a jumper to the + pin with a CL-60. Here is a picture of the SMPS and the preamp with the SMPS installed.

There was no hum, just a very loud squeal at full volume to the amp (volume control was at zero).
Hi @elwood625, could you please post the link to the input selector. It is 6 way right?
 
@ Ben, per your posts 636 and 1623 could you please share your PS Gerber with me. It would be appreciated. The other Gerbers you sent me are in production at JLCPCB. Thank you for that.

Just curious, why didn't you use one of your existing PSU PCBs and just resize the toroid for 62V and lower power rating to fit the FE2022.

Thanks,