PeeCeeBee

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#2,267
shaan said:
Here is the V3 schematic and BOM.

Have Fun!😉
Click to expand...

Hello Shaan.

Thanks for you work on PeeCeeBee.

I was looking for an amp similar to yours, I have tested a F5 and I was looking for a simple and elegant amp like yours.

my question is did you tried to put something similar to the P3 on the F5 v3.
I was wondering if it would have give a way to adjust the "distortion" on your amp similar to was it possible on the F5.

Thanks

F5 v3 schematic link
 
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#2,268
Hi brunogiovs.

P3 doesn't like Class-AB amplifiers with 85dB open-loop gain. 😉

There's the matter that in peeceebee it will be hard to implement due to no DC component in the feedback network flowing to ground. But the bigger problem is that in peeceebee it adds huge amount of higher order harmonics to the output which IMO is universally regarded as a bad thing.

There's another way that works the same thing in PeeCeeBee, which is to unbalance the 2K2 feedback resistors. Just install a 100K resistor in parallel with any one of the 2K2 resistors and you get a lot of even harmonics with some output offset which can be easily re-set to zero with the trimmers. Expect some loss in transparency when playing through highly sensitive speakers.

Thanks and cheers.
 
#2,269
brunogiovs said:
...did you tried to put something similar to the P3 on the F5 v3.
I was wondering if it would have give a way to adjust the "distortion" on your amp similar to was it possible on the F5.

Thanks

F5 v3 schematic link
Click to expand...

If you want to experiment then you can try placing the P3 the way shown in the schematic. In this config it will have more or less the same effect as it has in F5. 😉

Cheers and all the best. :up:

Btw, why don't we try the vanilla V3 first? 😉
 

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#2,271
You're welcome!

Just some thoughts about the trimmer (P3). In my experiments I found it to be very easy to make the amplifier produce a lot of even harmonics (not just the second harmonic) with the help of the trimmer. But the point at which distortion (mainly even-order components) measured lowest was when the trimmer was exactly at mid-point, i.e. providing equal resistance in both FB paths. At the end of the day the realization was that other than deliberately increasing distortion, the trimmer has no purpose, at least in PeeCeeBee.

🙂
 
#2,272
shaan said:
You're welcome!

Just some thoughts about the trimmer (P3). In my experiments I found it to be very easy to make the amplifier produce a lot of even harmonics (not just the second harmonic) with the help of the trimmer. But the point at which distortion (mainly even-order components) measured lowest was when the trimmer was exactly at mid-point, i.e. providing equal resistance in both FB paths. At the end of the day the realization was that other than deliberately increasing distortion, the trimmer has no purpose, at least in PeeCeeBee.

🙂
Click to expand...

cool that you already tried a "p3".
I was looking for reduce 2nd order harmonics.

how the biasing works ? what is the recomended biasing?
Thanks.
 
#2,273
brunogiovs said:
cool that you already tried a "p3".
I was looking for reduce 2nd order harmonics.

how the biasing works ? what is the recomended biasing?
Thanks.
Click to expand...

Hi brunogiovs.

Input and VAS biasing is done primarily by two 15K resistors sourcing and sinking current to and from the input BJTs' emitters.
Only VAS bias needs to be monitored/trimmed to ~10mA by the two 2K2 trimmers which also help trim the output offset.
Output MOSFET bias is auto-set to between 150-200mA by the two 1N4148 diodes.

That's all really. 🙂
 
#2,274
shaan said:
Hi brunogiovs.

Input and VAS biasing is done primarily by two 15K resistors sourcing and sinking current to and from the input BJTs' emitters.
Only VAS bias needs to be monitored/trimmed to ~10mA by the two 2K2 trimmers which also help trim the output offset.
Output MOSFET bias is auto-set to between 150-200mA by the two 1N4148 diodes.

That's all really. 🙂
Click to expand...

So If replace de diodes I can get 30-50ma. did you or someone already measured with a lower biasing?

Thanks
 
#2,277
V3 Gerbers

Hello Guys!

Here are the Gerber files for V3 PeeCeeBee. Hopefully these will make local printing easier for those whose PCB-plants don't accept PDFs.

These have been checked with gerber-viewer.com's online viewer and seemed okay to me. If anyone finds a mistake, let me know.

Happy DIYing to all.
shaan
 

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#2,279
You can use them in PeeCeeBee without any problem! 🙂

edit: PeeCeeBee doesn't have gate ESD protection zener diodes as the 1058/162 pair MOSFETs have them integrated. If you use the MOSFETs you mentioned then add 12V zeners between gate and source of each device.
 
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#2,280
After some days listening with Olafs clever 1.0 boards i enjoy more the simple vssa.
Choose good parts build and enjoy.
I was a bit reading back and found the way how to came to different bias point- good explained by Olaf too.
What is the reason to add 1 Ohm resistors in V3?- i think it's written here and sorry for asking again.
 
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