Single Ended CFA

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Nice job on the SECFA build guide, Borko. I’m sure it will be very helpful. It already cleared up how to adjust VR6 :)

The parts arrived today and I made a bit of progress on the first board.
So far, all the components picked in the Mouser project cart fit perfectly ;)
I couldn’t resist sneaking a couple red PRP’s in!
 

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Nice job on the SECFA build guide, Borko. I’m sure it will be very helpful. It already cleared up how to adjust VR6 :)

The parts arrived today and I made a bit of progress on the first board.
So far, all the components picked in the Mouser project cart fit perfectly ;)
I couldn’t resist sneaking a couple red PRP’s in!

Nice progress Vunce. Are those feedback resistors on your pcb 390 ohms?
 
Hello Bogdan,
Congratulations on the comprehensive write-up!, Surely it will be very useful to every builder.:cheers:

To Vunce,
Incorrigibly fast and beautiful build . Like the PRPs and silver mica's:up:. Inductor also from mouser cart or you woundup something on your own. looks perfect.
from pcb i see that it was designed on 7th July and in 9 days already pcbs are almost completely populated!

regards
prasi
 
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Joined 2014
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Thanks for the kind words fellas :)

@r_jik45,
Good eyes!! Since the BPR58 resistor legs are radial, these added test leads will make for easy DMM attaching points.

@gary s,
Yup, 10 turns/1.5mm/AAA battery

@bogdan_borko,
2//392 = 196R, it’s within 1% tolerance of 195R.

@prasi,
There is a CoilCraft inductor listed in the Mouser cart, but it’s backordered so I wound my own.
 
Thanks for the kind words fellas :)

@bogdan_borko,
2//392 = 196R, it’s within 1% tolerance of 195R.

No, tolerance is not a problem, never used these resistors, I wonder why are they coded that way, for caps 392 usually means 3900?
Btw I noticed that you placed 3 pins instead of VR20? That trimm pot is not optional
it is used as a RB for max idle current and RB1-4 are used in parallel connection to VR20 for lower idle current settings.
 
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In the first post, Bogdan wrote that there is "no noise or hum of any kind with sensitive speakers 97dB".
Does it mean that this amplifier is better coupled with sensitive speakers? What about 'less sensitive' ones around 90dB?

No I just wanted to say that there is no hum or buzz on sensitive speakers, easier to hear than on 85dB ones...
Hi efficiency speakers are better for this amp in therms of power needed, haven't tried but I don think there will be the power shortage even on 90>dB speakers for home listening. :)
 
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

Thanks Hugh, nothing original here, just one of many variations no one tried, as far as know. I wanted it to be as simple as possible and with lower distortion then the popular low power class A amps retaining same harmonic structure. I'm also curious how it compares with some other small class A amp, I hope someone will write a word or two.
 
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