Why not ask if TeaBag has some of his boards left?
http://www.diyaudio.com/forums/blogs/tea-bag/941-f6-clone-convertible-pcb-blog.html
It certainly has some nice features in it,
basic design rules implemented nicely, like; feedback taken from the output, quite small loop areas (at least if compared to some of the boards seen here), feedback and input ground returned to same point, forming a good audio ground including the speaker return, DOUBLE BUFFER which is important if one wants a similar frequency response as the Master got from the Original with the Semisouths,
and so on....
No wonder he (also) measured quite low distortions on it...
Nice work from him (TeaBag).
Wow, super fast fulfillment. I ordered mine on the 23rd and received it today. The boards and transformers look great. Good job guys. Thanks.
Just the standard FW power supply, for example, the last page of the
F5 manual.
http://www.firstwatt.com/pdf/prod_f5_man.pdf
Why is it that the F5 needs the thermal compensation with the 4K7 thermistors, and this F6 doesn't?
Is it because of the use of only N-channel MOSFET's?
In the article Nelson talks about the Semisouths having a tempco of zero just above 1 Ampere, but I thought this isn't the case with a IRFP240?
Just curious....
Is it because of the use of only N-channel MOSFET's?
In the article Nelson talks about the Semisouths having a tempco of zero just above 1 Ampere, but I thought this isn't the case with a IRFP240?
Just curious....
Probably because the bias reference, the Zener, is a fixed voltage, instead of being derived from a voltage divider off the rails.
That's a guess, hopefully somebody who actually knows will speak up.
"Paging Mr.Pass, Mr. Nelson Pass, please pick up the white courtesy phone..."
That's a guess, hopefully somebody who actually knows will speak up.
"Paging Mr.Pass, Mr. Nelson Pass, please pick up the white courtesy phone..."
From the F5 manual:
"Th1 and Th2 are small 4.7 Kohm thermistors that have been placed in series with R15 and
R16 respectively. The resistance of the thermistor declines with temperature, and if placed
in close proximity to the output transistors will help compensate for thermal drift. You can
build the amplifier without them, but you will have a longer warm-up time and you will spend
more time adjusting the bias."
From my experience with the F6:
I will have a longer warm-up time and I will spend
more time adjusting the bias (in the F6).
My experience with F6 is quick warm-up time, cause heatsinks are a bit too tiny 😉
But bias is surprisingly stable, stays within 10 mV when heated up.
And that's what I really didn't expect with absence of a correction circuit.
Only today I noticed that when the amp is turned on, it takes about 15 seconds before it plays music 😀 Probably the charging of the 1000uF.
Also strange, in this first 20 seconds of power up, the offset wanders up to just above 200mV and then quickly back to 10 - 15mV and then slowly lower when heating up.
I love this simple amp 🙂
But bias is surprisingly stable, stays within 10 mV when heated up.
And that's what I really didn't expect with absence of a correction circuit.
Only today I noticed that when the amp is turned on, it takes about 15 seconds before it plays music 😀 Probably the charging of the 1000uF.
Also strange, in this first 20 seconds of power up, the offset wanders up to just above 200mV and then quickly back to 10 - 15mV and then slowly lower when heating up.
I love this simple amp 🙂
The Fairchilds in the F5 have a bigger temperature coefficient, so they
drift more with temperature than the IR N channel parts.
Also, you can use higher values for the Source resistors on the F6 if you want,
as they are not seen in the AC performance, only the DC.
😎
I see that we have lost cool icon again.
drift more with temperature than the IR N channel parts.
Also, you can use higher values for the Source resistors on the F6 if you want,
as they are not seen in the AC performance, only the DC.
😎
I see that we have lost cool icon again.
