The AX of a handyman french

[Phill]

Hello

I will present my achievement :
http://domainedupossible.free.fr/pag...-X/alephX1.htm

schema rev 1.0
PCB : GB, rev 1.0

transfo : 2 x 15v / 225 va : 2 for a nono block
CRCRC : 68000µF/50v , 0R15 ...
The voltage rails : 17V (232/17.3---228/16.8)
8 IRF240 / block and matching here :
http://domainedupossible.free.fr/pag...H5/aleph55.htm
bias : 5A ..?...

R2-3 / 44-45 : 6x0.68 = 0.113 ohm
R5-6-40-41 : 3 x 1.2 = 0.4 ohm
jump j1a, Q12a, R17= 3.5k, d1a = zener9.1v/0.5w
R12-34, Rv =2K...

The measures after an hour heating and settings :
I made the measures 3 days in a row and the results are not very stable

-----------------block1-----/-----block2----

Source Resistors R5-40 :482,480,461,480 /478,493,493,475mv
offset relatif : 105 mv / 150 mv
offset absolu : Unstable, They vary continuously from -200 to +150 about 2 blocks
AC gain : input symetrique, 1khz, 115mv :
r2-3/r5, R42-43/R40 : 48mv block1/ 55mv block2

Air temperature :20 °C
Heatsinks : 47 °C

I do not know anything about electronics,But I see some things.
The matching is not perfect...
The offset is too high. It may be necessary to change the pair of irf9610, Or can you improve something ?
I do not understand why the values of AC gain are not identical...

And finally, I am also gifted in electronics than in English ....

Thanks to all
Phill

[jupiterjune]

Very nice work Phil! Those are some nice looking monoblocks.

Don't worry about your English, it is much better than my (and most American's) grasp of any foreign language. Sadly, it is better than many American's grasp of the English language as well.

JJ

[Magura]

Originally posted by Phill
Hello

I do not know anything about electronics,But I see some things.
The matching is not perfect...
The offset is too high. It may be necessary to change the pair of irf9610, Or can you improve something ?
I do not understand why the values of AC gain are not identical...

And finally, I am also gifted in electronics than in English ....

Thanks to all
Phill

This sounds like the problem we have cured previously, by increasing the source resistors to 1R0.

Magura

[carpenter]

Beautiful, very professional!

[wuffwaff]

Hi,

very nice but I´m missing the blue led

Yes,

trying another pair of IRF9610 would help to bring the offset down. 5-20mV is realistic.

The absolute offset varying by 400mV is normal. What is the startup value from cold?

What McMillan resistors are you using? There´s a lot of potential for better sound quality here.

About the ac-current gain. Depending a bit on the grade of matching it can vary from channel to channel. How much ac-c-g do you have now? (too lazy to calculate it myself)

William

[Phill]

hello

trying another pair of IRF9610 would help to bring the offset down. 5-20mV is realistic.

I do more in stock. I must find.The substance of the problem is certainly there.The matching must be carried out in the hundredth or thousandth of volts ?

What McMillan resistors are you using? There´s a lot of potential for better sound quality here.

R46-47 : 4.7K, 1%. Why and how better ?

the ac-current gain

We will see later!

thank you
Phill

[wuffwaff]

Hi,

0,01V would be nice, done at the right (ca. 10mA) current

10k makes your amps sound much nicer but could cause absolute offset problems. There must be a thread somewhere where some people describe the differences in sound.
I´m at 22k at the moment (with a JFet diffpair)

William

[wayne325]

Phil,

How much heat do your power supply resistors generate?

The heatsink for them is internal and may get very hot, while
also heating the inside of the amp.

Just a question.

Ton amplificateurs son magnifique!

W.

[Phill]

hello

0,01V would be nice, done at the right (ca. 10mA) current

On Block 1, R23: 4.70v and R25 : 4.70v.
This is not proof of a good matching?

10k makes your amps sound much nicer but could cause absolute offset problems.

I want to solve a problem offset, not add! But it costs nothing to try...

How much heat do your power supply resistors generate?

0R15, Approximately 60°C. Aluminum support of 4 resistors is at 50°C. No lid on the box...

Ton amplificateurs son magnifique!

tes amplificateurs sont magnifiques !
Thank you for the congratulations and Thank you for this goodwill!

I will start by changing pairs of 9610
After is another day

Phill

[wayne325]

Phil,

Are you saying you will never put a cover on your amps ?

If you're getting temps of 50C on the resistor plate with no cover,
then you have only one choice if you want to put a cover on
the amps. The front is made of wood and it is a good insulator.
The sides already have the transistors mounted directly to
them, and the back is covered. So the only choice you have,
if you want to put a cover, is to get the resistors mounted
onto the bottom or the heatsinks on the sides. Clearly the
sides is the better option. If you put a cover the internals will
pretty much be at 85C or higher and you don't want that.
The key is to reject the heat to the ambient air, not the inside
of the amp.

Please don't take this as a criticism. The intent is to help you
with a problem you have (if you want a cover).