As you can see from voltages posted by bogdan, the voltage at the output of inductor is about 1/2 the rail as this amp being a single ended amplifier. The output cap is must keep the dc out and pass only AC to speaker.
Yes, the output cap bank is optional. There is already a provision for a 30mm dia electro and 22mm pitch film cap on the PCB as output capacitor.
However with cap bank, One can use 35mm electro cap and many audio grade caps of 13mm dia ( 11 nos. I think) along with film caps.
Advantage of output capacitor (either on-board or via the cap bank) is no need for any DC protection for speakers. blessing in disguise.
here is how cap bank is used (/ instead on-board caps are used)
Single Ended cfa
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Thanks Prasi for the info and link.
It's rather new to me. I like the 'simple' design and the very nice expected sound from Bogdan comments. Following the thread, even if I don't really understand everything 😱
It's rather new to me. I like the 'simple' design and the very nice expected sound from Bogdan comments. Following the thread, even if I don't really understand everything 😱
I`m writing the article with all the information needed, so it could be more clear after reading. 🙂
Hi Prasi, I need some help (confirmation), is this the trimmer VR20 on the pcb that you forgot to add to the schematic?
Look at attachments..
Cheers!
Look at attachments..
Cheers!
Attachments
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Hi Bogdan,
its a dummy pot and extra pads to allow for external mounting of pot to vary bias as per one's wish since you had said that wiring a pot to access from front panel does not pose any risk of oscillation.
Here is the post by me to explain use of either the bias pot or RB1 -RB4.
Single Ended cfa
kind regards
prasi
its a dummy pot and extra pads to allow for external mounting of pot to vary bias as per one's wish since you had said that wiring a pot to access from front panel does not pose any risk of oscillation.
Here is the post by me to explain use of either the bias pot or RB1 -RB4.
Single Ended cfa
kind regards
prasi
Ok thanks a lot Prasi. I don`t think pot is a good idea (it must be doube-stereo pot) but never mind I`ll explain everything in the article.
I guess you used footprint for trimmer right?
Cheers!
I guess you used footprint for trimmer right?
Cheers!
Yes bogdan, I used trimmer with 0.9mm hole dia. and 2mm pads I think. If it's not required, simply one can ignore.
If anything else is desired please let me know package, I will adjust accordingly.
Kind regards
Prasi
If anything else is desired please let me know package, I will adjust accordingly.
Kind regards
Prasi
Sorry Prasi just one more question, what is the diameter of the holes for L1 footprint, or what`s the maximum diameter of the wire for inductor?
Hello Bogdan,
No problems, here are the dimensions of the inductor outline that pcb uses.
I think 10 turns of 1.5mm dia on a AAA battery would give approx 0.6uH value.
Holes of pad on pcb are 1.8mm, so one can use upto 1.5-1.6mm dia inductor wire max.
regards
prasi
No problems, here are the dimensions of the inductor outline that pcb uses.
I think 10 turns of 1.5mm dia on a AAA battery would give approx 0.6uH value.
Holes of pad on pcb are 1.8mm, so one can use upto 1.5-1.6mm dia inductor wire max.
regards
prasi
Attachments
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I'm not good at that, you'll have to wait for some member to write about the sound... I don't even have something right now to compare it with.
Thanks a lot for the article Borko, I have printed it out and will have a good read over the next few days. Any questions, I will get back to you as I really want to build this amp and I have Prasi's pcb's already ordered.
Well done, Borko, designed beautifully and thoroughly documented. I thought your use of the Hiraga drive to the upper output device was impressive, and the cascoded input stage was original and clever.
A great addition to the DIYaudio stable of fine amplifiers.
We wait the reviews....
Hugh
A great addition to the DIYaudio stable of fine amplifiers.
We wait the reviews....
Hugh