Another amp

[csl113]

i finaly set my bias right....

at 54V rail, it worked to set it at 1.8 mA...

the amp is working fine but,boy is it getting hot..., and i don't mean the final transistors, because i have a huge heat sink, and a big fan...

but the mje340/350, and the mje 15030/31 are getting hot..., i supose i will put them a bigger heat sink...


the amp, sounds good, easy to build...nice sound, cheap...

i can hardly wait, to test it on a osciloscope, to see how it preforms there...

 

[chemelec]

For any persons Interested, I have Cleaned up and Re-Drawn the Schematic.

http://www3.telus.net/chemelec/Projects/Misc-PCB

I Agree with: amplifierguru, Especially on the Supply Rails.
The Amp that I Designed and currently use is Less Power than this one and I used a Decoupling circuit on its supply rails.
So I plan to make a Few Revisions on this one in the near future.

Probably also a revised board at some point.

But it is Becoming Gardening Time so that may be awhile.

Take care...........Gary
PS: I'll give it another week and than Anounce the Winner.

 

[desert00rat]

Before committing myself to ordering all the parts I need, I have a few questions for those that have already built them or are in the process of building theirs. BTW: I live in the US.

1. I know of several places to get most of the parts (Avnet, DigiKey, Arrow). What places do you people recommend?

2. Where can I get a heat sink of such large proportions (like the one pictured on the author's web page)?

3. Since there is a huge variety of parts, what kinds of capacitors are used? (I'm used to seeing the ceramic and electolytic...not the square ones that are pictured.)

4. I'm planning to build a dual-channel amp. Will the power supply be sufficient to run both channels? (I will be using a 500VA 2x37 Torid).

Thanks in advance.

 

[csl113]

[B
3. Since there is a huge variety of parts, what kinds of capacitors are used? (I'm used to seeing the ceramic and electolytic...not the square ones that are pictured.)

4. I'm planning to build a dual-channel amp. Will the power supply be sufficient to run both channels? (I will be using a 500VA 2x37 Torid).
[/B]

500W is sufficient for both channels only at 8 ohms... for 4 ohm, you should use a bigger transformer...

also, i think a 37V ac is a bit low...(50V cc)


i am using a 550W normat transformer, 44V ac, 58 cc...



C3,4 -normal, electolytic
C2,5,8-ceramic
C1,6,7-have to be non-polar,non-electolytic , and also non-ceramic ... there are lots of other types(i just don't know how they are called....), for ex: mkt, film , multy-layer...

and C7 has to be at least 200V...





the transstors, 15030/31 work in class A or class AB...???

 

[csl113]

could someone please tell me if the prefinals(MJE 15030/31) work in class A or class AB ???

i believe that they work in class AB, but someone told me that they work in class A, and only the finals work in AB....am i right or wrong...???

 

[chemelec]

My Number was 66 , So I Believe "csl113" has won these Boards as his number was 56.

I Don't want to screw-up on this, So can someone else chech the past postings and Varify This.

PS: I Also Believe those drivers work in AB.

Take care............Gary

 

[csl113]

yes, i believe that is corect

nobody else said a number after 50...

 

[csl113]

so, how can i contact you....so we can talk...???

i tried to send email, but it appears that it's confidantialy...

caold you send me a mail at csl1131@yahoo.com

 

[chemelec]

csl113 so, how can i contact you....so we can talk...???
i tried to send email, but it appears that it's confidantialy.

Hi, Send me an Email at: chemelec@hotmail.com

You MUST Put the Words: "Electronic Free PCB" in the Subject Line.

And give me your Name and Address so I can get these Mailed out to you.

Take care...........Gary

 

[chemelec]

Those Boards were Mailed to "csl113", Yesterday.

Hopefully he will get those amps assembled and post his results on here.

Thank to all the persons that submitted a number.
But I am Surprised there were not more.

Take care all.............Gary

 

[Dragance007]

the pcb's arrived and they r good

 

[Dragance007]

another shot

 

[a_p_deguzman]

m250

is anyone have tried using MJL4281A(NPN)/MJL4302A(PNP) as the output transistor instead of MJ15024/MJ15025.

 

[ldanto]

cool. can anyone tell mewhat fuction 'p1' has in life- does it control gain or what?

 

[csl113]

it sets the bias.. the idle curent ...

at first it should be set to it's maximum position....is it is set to it's idle position.. you may burn the output transistors..

 

[vAD]

Excuse! Did not read everything, likely wrote R 6, 7 - 100, D1 - D4 - are unnecessary, the shunt 0,1uF, R16,17 - 3k. And I would change a feedback.
It only my opinion, and is more than anything)
Excuse for my English.

 

[ldanto]

See on the schematic- p1- it's the only pot on the schematic!!!

let me know if there are any other problems in the schematic

 

[ldanto]

And the final question is:

is it absoloutely essential that the amp runs off a dual rail power supply. it's just that i've found a tordial transformer in RS which has 2 55 volt outputs and if i use it as a dual rail it will give me an output of 110v- the same as in the us

 

[csl113]

there is NOTHING wrong in the schematic....

it works fine...

the amp run's on dual power suply...
a simple power can NOT be used...

if the transformer has an output of 2*55V AC this will be 2*75V dc,and you can't use this much voltage..

i would sugest a 2*60V dc max

is this your first amp??? if it is i would sugest you read a little more about amplifiers...

after you build it before testing it relace the fuses with a 50-120 ohm 3-5W resistor ,because if you did something wron smoke will come out of these resistors and not out of the output transistors

 

[ldanto]

ok ok, calm down, just checking

right, so i've got to try and find a 2*38vac transformer, right?

the output must be smooth though with the size of the smoothing caps