anatech said:
Yes, the jfets should be cascoded, most amps cascode the input jfets. It also improves PSRR and makes the input less reactive. 🙂
Mike
Here's the BOM for my PCB. I hope that I got all the parts, let me know if I goofed up anywhere. All the parts on the amplifier section are labled according to Mike's schematic. The PS is labled according to the schematic found in post #114. Also, label R23 near the bottom right mounting hole should be R12.
Al
Al
Found a mistake in the BOM for Q7,Q8 ratings. Here's a new BOM.
Mike, just wondering If you've taken a look at my PCB. Any thoughts, ideas about others building it?
Thanks,
Al
Mike, just wondering If you've taken a look at my PCB. Any thoughts, ideas about others building it?
Thanks,
Al
AAK said:
So many amps, so little time....sigh...
I sure am watching with a lot of interest. Education by osmosis?...at least until I dig into it.
So many amps, so little time....sigh...
I sure am watching with a lot of interest. Education by osmosis?...at least until I dig into it.
I make some measurements between original symasym and my amplifier, modified version with k170 and more tail current.
Open loop gain:
1kHz -> original 27400, mod 13800
10kHz -> original 22900, mod 11100
20kHz -> original 16100, mod 7700
100Khz -> original 3600, mod 1700
Slewrate:
original 23V/us, mod 18V/us
PhaseShift at 1Wrms/8ohm 20KHz:
original -3.8grd, mod -3.1grd
I want to reduce close loop gain by 2 but I don't know if the amplifier will be stable.
I can't do that in spice, I don't know how. Can you help me Mike?
Open loop gain:
1kHz -> original 27400, mod 13800
10kHz -> original 22900, mod 11100
20kHz -> original 16100, mod 7700
100Khz -> original 3600, mod 1700
Slewrate:
original 23V/us, mod 18V/us
PhaseShift at 1Wrms/8ohm 20KHz:
original -3.8grd, mod -3.1grd
I want to reduce close loop gain by 2 but I don't know if the amplifier will be stable.
I can't do that in spice, I don't know how. Can you help me Mike?
I would like to use current mirror and jfef cascode ion the input stage and also a cascoded JFet current source. To my expirence that improves clarity and texture.
I also think tha the secondary filter would be better if devided into two sections r-c wit 22 ohm and 2000 microfrarads.
It could also be a good idea to insert diodes in front of R14-15
best MiB
I also think tha the secondary filter would be better if devided into two sections r-c wit 22 ohm and 2000 microfrarads.
It could also be a good idea to insert diodes in front of R14-15
best MiB
Hi all,
Well, good news. Everything works great with the new revised PCB. As you can see from the pic the output transistors no longer mount underneath the board. You'll need 4" of heatsink instead of three, but it's now DIY friendly. I'll post gerbers, and a revised BOM later today.
Al
Well, good news. Everything works great with the new revised PCB. As you can see from the pic the output transistors no longer mount underneath the board. You'll need 4" of heatsink instead of three, but it's now DIY friendly. I'll post gerbers, and a revised BOM later today.
Al
Attachments
AAK said:
Hi AAK, nice work! 🙂
Just one question, where are the 100uf for filtering supplyrails to the frontend gone ?
Mike
MikeB said:
Sorry, my fault, you have used the 1000uF as filtering to the drivers + frontend...
Mike
Hi Mike,
There on the board. R31,C8,C10 filter the positive rail front end, and
R32,C9,C11 the negative. I'd guess the size of C8 and C9 through you off. There Nichicon KZ series 220uF/100V O.D 620 mils.
Al
There on the board. R31,C8,C10 filter the positive rail front end, and
R32,C9,C11 the negative. I'd guess the size of C8 and C9 through you off. There Nichicon KZ series 220uF/100V O.D 620 mils.
Al
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