The Mini-A

[Zen Mod]

second link is not working

first you need to tell us what dissipation per channel you are planning

 

[jpdunord]

Sorry for the link here the two links here:

0.40c/w
Dissipateur profilé peigne 661 - Profilés coupés
21.65

0.35c/w
Dissipateur profilé peigne 661 - Profilés coupés
45.90

The dissipation per channel is 54w.
I used the excel's Aleph power for the calculation

+-18v alim voltage
2 fets per channel
1 or 1.5amp bias

Thanks a lot

Patrice

 

[Zen Mod]

Pdiss=Urails x Iq

so , (18x2) x 1A5 = 54 W of heat

first case , rough calculus :

Th=Tamb. + (Pdiss x Rth)x1.1 = 25C + (0.4 x 54)x1.1 =49C

skipping plenty of details , I believe (from experience with similar heatsinks) , you'll be good with that , less expensive one

maybe you'll need babysitter in hottest part of year

 

[jpdunord]

Thanks a lot for your explanation, thank you very much : my wallet will be happy thanks to you.
A last question i plan to use a CRC filter for the psu. I'll take 6 capacitor of 10 000uf 25v
but for the resistance it will be 0.22ohm but what the rated power? 5 watts 10, 25watts ???

Thanks a lot for your answer for a newbie as me.

Patrice

 

[jpdunord]

Maybe i'm a little silly but i what the babysitter in the topic?

 

[Zen Mod]

Thanks a lot for your explanation, thank you very much : my wallet will be happy thanks to you.
A last question i plan to use a CRC filter for the psu. I'll take 6 capacitor of 10 000uf 25v
but for the resistance it will be 0.22ohm but what the rated power? 5 watts 10, 25watts ???


Thanks a lot for your answer for a newbie as me.

Patrice

3W is plenty

Maybe i'm a little silly but i what the babysitter in the topic?

click on word babysitter in that post

 

[Zen Mod]

3W is plenty

resistor dissipation in that case :

P=I^2 x R

if I is Iq x 2 ( PSU for two channels together) then

P=(2x1A5)^2 x 0R22 = 9 x 0.2 =1W8

choose resistor of double or triple power and you're good

3W one will be hot , 5W will be colder , due sheer size reasons

 

[jpdunord]

Hi Zen Mod

And sorry to be late to answer you. I want to thanks you a lot for your answer.
Instead of answering me stupidly you put all the calculations it took to find the power of resistance. As I could use the formula for other amplifier. It's like the saying: "it is better to teach someone to fish rather than feed him." Some thing like her.
I will post pictures Some when it's over. Maybe is this the beginning of the Adventure Pass. I already feels to be aleph X but I have already look at the size of heatsinks budget to see what I need. See and wait ...

Sorry for my bad english it's google translate

 

[Hedliden66]

Has anyone made a Mini with Irfp250 and Irfu9210 ?
If so, I'm interested in the sound impression

 

[Nag]

mini-A with 18Volts.

Hi All,
Initially I planned to build PLH amp. While reading threads suddenly red mini Aleph. I changed my mind as PLH has capacitors in signal path. So I want to build Mini-A. In this thread so many schematics. I want to build with PSU +18V,-18V as it gives 15Watt output into 8ohm. Can any one help me which resistor values need to change and where is trim pots to adjust bias. bias >2A will give low distortion as per NP. I already bought two heat sinks which are 300m length. Sorry for asking so many already discussed but its messed up.
Thanks,
Nag.

 

[Zen Mod]

mini or not mini , it is more (or exactly) matter of PSU rails and Iq , not so much any difference in parts values

generally speaking , thinking about mosfet's capacitances in function of rails voltage ( read D-S voltage) , it's clever not to go under ,say,18Vdc

then think about Iq , counting that current envelope is aroundish 2.5 times Iq , meaning - if Iq is 2A, you can count ar something as 5App delivered to load

if you're feeling insecure in own calculus , at least think of desired power range , then ask what you need to ask

regarding construction - everything is easy when you solve input JFets issue , after that you can use any of available pcbs , altering values to your need ...... or you can even make it PtP or on veroboard - plenty of successful examples around

in case of unsolved JFets issue , there is my Babelfish J iteration (observe - blatant advertising ! )

 

[JimT]

ZM, do you have a mini Babelfish J version?

 

[Zen Mod]

as I said - there is no difference in pcbs and most values

you're making it Mini or not-Mini , choosing rails and Iq , using any decent pcb package

(yup , I have it)

 

[Nag]

15watt aleph3

Dear All,
Can I remove parallel output stage for 15watt output without changing any components and rails.
As per NP nothing to adjutant in this circuit. And I want use IRFP240 instead of IRF244. It is interchangeable as per NP.
If I want to increase bias 2A and reduce rail voltage to 18V what change is required.

Thanks,
Nag.

 

[Zen Mod]

read this thread , everything explained in details

also ,study attached pdf

 

[res07njc]

Dear All,
Can I remove parallel output stage for 15watt output without changing any components and rails...

....If I want to increase bias 2A and reduce rail voltage to 18V what change is required.

Thanks,
Nag.

I have one that runs ~18.5V.. you may need to start with .22R at the output source to reach 2A. Mine with .33R maxes out around 1.65A per device, IIRC.

 

[Nag]

After giving some thought, I don't want to modify anything in schematic in post #894 as It is tried, tested and build circuit by NP. So I will use only one output stage. As per my understading it wont give any problem up to 15Watt@8ohm. What will happened if it draws 20Watt@8ohm.

 

[Zen Mod]

first thing first

for full version you need heatsinks capable of dissipating at least 80W/channel , which means no more than 25C of temp. rise above ambient

if you have smaller heatsinks - it's easy ...... just decrease Iq to follow Papa's palm rule

 

[vdi_nenna]

Anyone try Grey's original schematic with jfets on the input?

If not, can input be modded like the Aleph 3 with the SJ109??

 

[Eric]

oops- post removed, was thinking of Grey's original small scale Aleph-X, not the Mini-A...