Great!D'oh! R107 is 1R - I made the same mistake!CCS current set to 30mA and all is well. I now need to connect it up and have a listen.
Many thanks for your assistance.
Hello,
I'd like to check some numbers before I hook it up to the stereo system.
Edit - I also just want to make sure no heat sinking is needed on the new parts. I don't own anything that could be used for heat sinking for this packaging.
Thanks,
Alan
I'd like to check some numbers before I hook it up to the stereo system.
- I preset CSS to 10 mA.
- I changed Q101 to BC550C.
- I changed Q102 to VP0106 (there was a pinout change needed here as well as above, but its not the same pinout change).
- I am running about 6x gain from my original SCG build.
- VS on left channel is 2.614 volts. VD is 18 volts. VG is at 17.5 mV (as low as I can get it).
- VS in right channel is 2.585 volts. VD is 17.82 volts. VG is at 0.7 mV (as low as I can get it).
Edit - I also just want to make sure no heat sinking is needed on the new parts. I don't own anything that could be used for heat sinking for this packaging.
Thanks,
Alan
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No heatsinking needed with 10 mA. However, given that you have a gain of 6x, Vs gets multiplied by 6. So, I would put a few volts on the gate of the VP0106. Targetting a Vd of 36V, you would put 36/6 = 6 volts. If you do this, you can increase the current to 13 mA (about 10 mA through gain device, about 3 mA through resistor network) and still remain within the dissipation limit of the BC550.
So, the liberal arts translation of the above would be:
Turn RV103 until I measure 6 volts between Vg and ground?
And then double check that I have about 36 volts at Vd and ground?
Then, when setting current of the CSS to 13 mA, is it still a good idea to short the drain leg or rlim to ground, or is that only needed when first setting it?
Turn RV103 until I measure 6 volts between Vg and ground?
And then double check that I have about 36 volts at Vd and ground?
Then, when setting current of the CSS to 13 mA, is it still a good idea to short the drain leg or rlim to ground, or is that only needed when first setting it?
Lol!!!
Almost, 6 volts between Vs and ground.
Yes! You might get slightly higher than 36V, which is okay.
No, that’s only for the first time. You can do it live by measuring across R107.
Went to the Shakti concert last night at the Mondavi Center in Davis. Absolutely world class! Zakir Hussain and John McLaughlin were phenomenal as were the rest. The Shakti tour is on right now and I highly, highly recommend it as a dose of pure joy.
Just like Nelson, this group of musicians have never stopped honing their art. They continue to grow and have fun and we get to enjoy it.
Just like Nelson, this group of musicians have never stopped honing their art. They continue to grow and have fun and we get to enjoy it.
@ra7
Checked the schematic vs. the BOM vs. the Mouser project...everything seems accounted for.
As you said, the Mouser project doesn't have the resistors, but these are no issue.
Other notes:
1. The footprint of the radial 10 uF caps is not a perfect match, but they will fit.
2. In the Mouser project, you put in FQPF9P25 instead of FQP12P20, but I think that's a valid substitute.
3. In the Mouser project, you put in TL431BCLPR instead of TL431LP, but again same family and valid substitute.
I put in my Mouser order.
And forgot to add the 100 mA fuses. Ehehe. Classic. Luckily I think I have some of those stashed somewhere.
Also, I kinda assumed the Qs won't need any heatsink, but I have plenty of those otherwise.
So, all good Rahul.
Now, you just need to send me the PCB itself.
Checked the schematic vs. the BOM vs. the Mouser project...everything seems accounted for.
As you said, the Mouser project doesn't have the resistors, but these are no issue.
Other notes:
1. The footprint of the radial 10 uF caps is not a perfect match, but they will fit.
2. In the Mouser project, you put in FQPF9P25 instead of FQP12P20, but I think that's a valid substitute.
3. In the Mouser project, you put in TL431BCLPR instead of TL431LP, but again same family and valid substitute.
I put in my Mouser order.
And forgot to add the 100 mA fuses. Ehehe. Classic. Luckily I think I have some of those stashed somewhere.
Also, I kinda assumed the Qs won't need any heatsink, but I have plenty of those otherwise.
So, all good Rahul.
Now, you just need to send me the PCB itself.
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See schematic below. This is the gain stage plus buffer. I just discovered something new about the PS, so I am working on revising it. Also discovered C1p few days ago, which makes a big difference. The schematic shows the new CCS, absence of pot for setting CCS value, removal of bias adjustment at input and for the gain stage (Part I upgrade), new p-channel input FET, and zener protection of output devices. The gain device shown below is the same as the old one, but on the PCB there will be place for various pinouts and footprints so that a variety of BJTs, MOSFETs, and JFETs can work. After all, the genesis of this design is the ability to make triodes out of ordinary devices. It puts the gain FET in a most favorable position and I am always amazed at the different sounds coming out of various SS parts.
Thanks Rick! I appreciate that very much. Good to know that when you put an effort into something, it is being noticed. ❤️
SCG will be at BAF next weekend. Hope to see some of you there. Still not sure if I will bring the old SCG plus Part I upgrade or new one plus buffer. Been hearing really good feedback about Part I upgrades.
SCG will be at BAF next weekend. Hope to see some of you there. Still not sure if I will bring the old SCG plus Part I upgrade or new one plus buffer. Been hearing really good feedback about Part I upgrades.