To Monk55, mgb1965, and everyone who may be interested in the PS boards, the amplifier boards are about to leave JLCPCB and make their way to me. I will hopefully be able to have the amplifier board tested in a couple of weeks. If you intend to order the amplifier board and PS board together, then I will send both files to you after the amplifier board is tested.
I have a tube stage that runs on the 40V rail - - and still delivers some 8 Vrms/22Vpp. Amplification something like 2Vpp. (?) Any interest?
The boards were delivered on Christmas Eve and I finally got them stuffed and installed.
I'm still learning Kicad and trying different things, and that resulted in some silkscreen labels not getting on the Gerber files. I could have discovered the issue before ordering the boards if I had done a more thorough review of the Gerber files - lesson learned. Fortunately, the labels are only missing on one side of the board. So one channel is assembled, the existing power supply changed from V+ to V-, the power supply tested, and the board installed.
It is now powered up and has been running for about two and a half hours. Currently it is at design Iq of 2.5A, with V- at -37.5V and Vds at 35.0V.
Tomorrow I will do some power and distortion measurements. Hopefully there will be no problems.
I'm still learning Kicad and trying different things, and that resulted in some silkscreen labels not getting on the Gerber files. I could have discovered the issue before ordering the boards if I had done a more thorough review of the Gerber files - lesson learned. Fortunately, the labels are only missing on one side of the board. So one channel is assembled, the existing power supply changed from V+ to V-, the power supply tested, and the board installed.
It is now powered up and has been running for about two and a half hours. Currently it is at design Iq of 2.5A, with V- at -37.5V and Vds at 35.0V.
Tomorrow I will do some power and distortion measurements. Hopefully there will be no problems.
Attachments
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Tokin SIT Follower 193V PCBs-Missing silkscreen .JPG -
Tokin SIT Follower 193V PCB stuffed.JPG -
Tokin SIT Follower 193V PS Polarity Change.JPG -
Tokin SIT Follower 193V Testing PS.JPG -
Tokin SIT Follower 193V Setup-Bias adjustment.JPG -
Tokin SIT Follower 193V Bias Adjust in progress-V-37.19V Iq 2.3A Vds 34.89V.JPG -
Tokin SIT Follower 193V PCB in Amp.JPG
Testing turned up a major noise issue at 60 Hz and 180 Hz. Since I had revised the power supply, I checked it thoroughly but didn't find anything wrong with it. I then turned my attention to the bias voltage supply on the pcb and that was the source of the problem. That all took several frustrating hours but with the addition of a capacitor at the end of the bias supply, the noise is now at a much lower level.
I have revised the pcb and hopefully this version will be the keeper. I'll review it again tomorrow and if I don't see any issues, I will order another five boards.
FFT-before and after, revised schematic and board attached:
I have revised the pcb and hopefully this version will be the keeper. I'll review it again tomorrow and if I don't see any issues, I will order another five boards.
FFT-before and after, revised schematic and board attached:
Attachments
Hello,
I've been reading this thread for a long time and I can't wait to use my THF51 with your new Pcb.
I LIKE YOUR WORK.
I just read:
https://www.diyaudio.com/community/threads/sit-choke-loaded-follower.393966/
which on the main board integrates a buffer with DN2540. But I don't understand if this solution offers advantages when I then drive everything with a preamplifier that is able to supply current and directly drive the THF51s like the one that they used. or ACP+ or Aksa Lander or USSPA2 and so on.
What do you think about?
Regards
Guglielmo
I've been reading this thread for a long time and I can't wait to use my THF51 with your new Pcb.
I LIKE YOUR WORK.
I just read:
https://www.diyaudio.com/community/threads/sit-choke-loaded-follower.393966/
which on the main board integrates a buffer with DN2540. But I don't understand if this solution offers advantages when I then drive everything with a preamplifier that is able to supply current and directly drive the THF51s like the one that they used. or ACP+ or Aksa Lander or USSPA2 and so on.
What do you think about?
Regards
Guglielmo
Tokin SITs have high input capacitance. If your preamplifier driving it has high output impedance, the high frequency response may be affected. See My earlier post re: preamp output impedance. So an input buffer would solve that problem.
Once in a while a Tokin SIT with very high gate leakage current shows up and creates havoc in an amplifier, causing runaway quiescent current. One solution to that issue is to have a buffer in front of the SIT and move the SIT bias voltage from the SIT gate to the buffer gate.
However, if your preamp has low output impedance and if you don't have any problematic SITs, then an input buffer is not a necessity.
By the way the ACP+ has low gain and low voltage output, so it is not a good preamp for a follower amplifier.
Once in a while a Tokin SIT with very high gate leakage current shows up and creates havoc in an amplifier, causing runaway quiescent current. One solution to that issue is to have a buffer in front of the SIT and move the SIT bias voltage from the SIT gate to the buffer gate.
However, if your preamp has low output impedance and if you don't have any problematic SITs, then an input buffer is not a necessity.
By the way the ACP+ has low gain and low voltage output, so it is not a good preamp for a follower amplifier.
Hi Tom,
What Zen Mod said. Unfortunately the B1 Korg has very low voltage output. Since this amp is only single stage and has no voltage gain, it needs a preamp or gain stage that can output about 15Vrms to get full power output. Of course in real life, you can probably made do with less as most people don't max out their amplifiers but the B1 Korg's output is still too low.
The good news is that Nelson's latest DIY Front End 2022 is a good candidate for that.
Attached is the B1 Korg Distortion vs Output graph showing the low voltage output.
By the way, the new pcbs finally cleared Customs today so perhaps I will have them tomorrow. Shipping took quite a bit longer this time, probably slowed by Lunar New Year celebrations.
What Zen Mod said. Unfortunately the B1 Korg has very low voltage output. Since this amp is only single stage and has no voltage gain, it needs a preamp or gain stage that can output about 15Vrms to get full power output. Of course in real life, you can probably made do with less as most people don't max out their amplifiers but the B1 Korg's output is still too low.
The good news is that Nelson's latest DIY Front End 2022 is a good candidate for that.
Attached is the B1 Korg Distortion vs Output graph showing the low voltage output.
By the way, the new pcbs finally cleared Customs today so perhaps I will have them tomorrow. Shipping took quite a bit longer this time, probably slowed by Lunar New Year celebrations.
