May i ask why the transistors are under the pcb? I am fairley new to building stuff, and it seems strange to me that they are there, and not on the edge of the pcb. It seems harder to mount and fix when i blow one, and you end up paying for pcb mm2 that are "not used" to other things than covering the transistors. I have seen this in several other designs as well, and i always find it strang.
Compact design fits small footprint on heatsink. Also securely mounts the board without additional fasteners, standoffs etc.
Thanks shaan for the designs and group buy. I've been following peeceebee thread for a while, good opportunity to get involved.
Shaan
Thanks for arranging the first ever GB for PeeCeeBee and give us a chance to get the one of the best PeeCeeBee design (sonically & aesthetically) so far.
I've already ordered 2 pcb for me and will order more later after playing with the first pair.
Can you please tell me what will be the mode of payment and shipping charge for India.
Regards
Sent from my GT-N7100 using Tapatalk
For buyers within India, payment is through PayPal or Bank Account Transfer and shipping charge is Rs.100/- for 4 PCBs or less. For more than 4 PCBs shipping charge is Rs.150/- per consignment. Package and processing included. Maximum 8 PCBs per consignment.
🙂
Hi Shaan,
One cant make a payment via paypal within India, Government rules!.
Just for the info.
reg
Prasi
Hello guys.
Alert !! Beginners question on amplifier design:
I found that the challenge of building a VSSA is the matching of transistors.
So my question is did someone already: to put a trimmer between the input of the first BJTs, and the idea is to not put the 2k2 feedback resistors. So one could adjust first the trimmer to account for mismatches on the BJTs and mosfets included. So only after the trimmer adjustment the 2k2 feedback resistors would be put in place.
is this idea work?
Thanks
Alert !! Beginners question on amplifier design:
I found that the challenge of building a VSSA is the matching of transistors.
So my question is did someone already: to put a trimmer between the input of the first BJTs, and the idea is to not put the 2k2 feedback resistors. So one could adjust first the trimmer to account for mismatches on the BJTs and mosfets included. So only after the trimmer adjustment the 2k2 feedback resistors would be put in place.
is this idea work?
Thanks
Attachments
Capacitor coupling at input might be inevitable.
IME, trimming without the feedback resistors is extremely hard or nearly impossible as without them the amplifier is working with its full OLG and the output will stick to one of the two rails.
You may want to try this idea with the feedback resistors installed and turning the trimmer to find the sweet-spot while looking at the 1KHz spectrum on a PC based analyzer.
Matching of the input and VAS BJTs is good but extreme matching is not necessary. A difference of +/-5% will be no problem in this amplifier.
The two trimmers on the PCBs does the same thing as R1 in your attachment, but work in the emitter nodes which is much safer and also doesn't demand capacitor at input.
Interesting. the idea is to have the amp on a lab psu during the adjustment phase and the tests should be with no load. and oscilloscope is somehow also needed to help with the adjustment or detect any sticking to rails.
I got like more around of 200 bc560c/bc550c already .. and best match I got was ~15%.
So I'm a bit frustrated. 🙂
Thanks for your explanation.
You are welcome.
Have you got the V3 PCBs? If yes then take pix fast and show us. 🙂