Class A amp all over :) Need PSU!

[Semir]

Hi there!

I'd need psu circuit for the thing written below. (and some sentences about transformators, amps, etc )

I took it into my head to build two new speakers... How does this connect to the Class A amps? Cos my second thought was to create a good amp for it!

Now I am strugling with the circuits. The finest, which I like most, is a 60W amp (www.tcaas.btinternet.co.uk/curtis60w.pdf I'm sure you know it). But I dont need that much amplifying!! I believe I'm too dumb to re-design that one, so I looked for an other http://web.telecom.cz/macura/pma2_en.html . Like it? That seems good, but I dont know whether the two OA pre stage is noisier or not than the preamp of the 60w-ts. But still I'm not able to mix the two and believe it does not worth the job.
After all I decided to build the 25w one, that will do with respect to my experience.
I'd need psu for it! I'd like to make seperate 15/-15 and 25/-25 v rails.

Or if you can help me with my first two problem with re-designing, than that )

Looking forward...
Yours,
Semir

Million thx! )

[moamps]

Hi,

a suitable PSU design (+/-25V) can be found at http://www.tcaas.btinternet.co.uk/index-1.htm (great website, IMO). Output voltage should be set to the value you need but this is done fairly easily.

PSU for input opamp supply (+/-15V) can also be found there - http://www.tcaas.btinternet.co.uk/jlhlm3x7cb.htm. However, "slight" modifications will be needed: Q1, Q2, Q3, Q4, R3, R4, R9 and R10 should be thrown out; R1 and R2 should be replaced with a jumper; C1 and C2 should have at least 470uF.

PMA, who is the designer of the amp you're interested in, is also a member of this forum so you might want to ask him for further advice.

Regards,
Milan

[Semir]

Wow! Thanks a lot!

[Semir]

Hi again!

Actually that helps me very much. But still I dont know anything about transformators. Could you help me with that too?

Your,
Semir

[sajti]

Originally posted by Semir
Hi again!

Actually that helps me very much. But still I dont know anything about transformators. Could you help me with that too?

Your,
Semir

Szia,

for unregulated PSU, I recommend 2x18-19V transformer with about 100-120W/ch. Regulated PSU results lower noise and hum, but in this case You need bigger transformer, and regulator, with large amount heatsinks as well...
I would use unregulated with RC filter, and big capacitors.

sajti

Jó bütykölést!

[Semir]

Originally posted by sajti



Szia,

for unregulated PSU, I recommend 2x18-19V transformer with about 100-120W/ch. Regulated PSU results lower noise and hum, but in this case You need bigger transformer, and regulator, with large amount heatsinks as well...
I would use unregulated with RC filter, and big capacitors.

sajti

Jó bütykölést!

Hali!

I believe regulated psu is needed as I'd want to get two suply rails (+-15 and +-25). What does that do with the transformer? I mean, the two circuits meant by moamp looks good for it. Those are regulator circuits, and I'm in the need of a transformator for those two. Am I wrong? Or you mean that this kind of regulating is unimportant in contrast with an unregulated but filtered psu?

After all, you could help me in something else, too. Where can I buy it? (I learn at budapest, so thats not a problem.)

Thank you for the reply!
Happy xmas for everyone!

Köszi!
Csáó!

[sajti]

Szia,

for regulated power supply You need the secondary AC voltage same as the final DC. So 2x25V looks good. This will provide enough headroom, if the mains lower few percent. With this solution, I recommend 150W transformer for each channel. You can get the 2x15V from the regulated 2x25V DC, with two zener regulator.
Please keep in mind, that regulation means 27-28W more dissipation in the power supply.


sajti

[Semir]

Hali!

Thanks! Im keeping )

150W per channel??

I know that it is advisable to use seperated psu for each channel, but isnt it a bit too expensive? (I cannot even imagine the price of a tranformer, and I think a 20000uF cap is about 2-3 thousand Ft-s)

So you mean not to use any regulation, but something like that I attach?

And at last: do you know where can I buy any transformer?

Eh basszus, kezdem úgy érezni, hogy túl nagy fába próbálom belevágni a fejszémet... )

Thx a lot!

Have nice day!

Bye!

[sajti]

I don't think that it's too complicated. 22000uF/40V, is about 2-3Euro (500-750HUF), so it's not expensive. You can use single transformer, with 300W or more (bigger is better, because class A use the full power from the PSU every time). The price of a single 300W transformer is about 60-70% of the double 150Ws.
The regulator can be simple darlington emitter follower, with 27V zener as reference. Use separated regulators for each channel to reduce crosstalk.

Menni fog!

sajti

[edl]

hello

http://www.lomex.hu
440Ft egy 33mF/35V
here you can buy 33000uF/35V elkos for 440HUF (about 2 Euros)

átersztõtranyós stabilizátort 24V-os stabkockából is csinálhatsz. egy párszáz ohm-os trimmer kell a GND-láb és a föld közé. azzal be lehet állítani a 27V-ot. vagy a trimmert egy 3V-os zénerrel helyettesísd. ebben az esetben nem kell állítgatni.

[if you build the reg.PSU with pass-transistor tech, you can use 24v/1A regulator (7824) as reference. you need to take a 3V zener between the "gnd" leg and the ground. now it will give 27V.]


http://www.elektris.hu
itt kapsz jó áron jó toroidtrafót.
here you can buy good toroid-type trannys. they are so cheap.