psu question n° ???

hugobross · 6th September 2002, 11:22 AM

I've checked out many amplifier designs, and especially the PSU designs. But there's a big difference in the recommendation for the power of the transformer (sometimes it varies about 2 or 3 times for the same output power).

So, I would like to ask you what class AB amplifier (stereo, maybe 4 amps bridged) (?? watts) I can build with 8 transformers of 120 VA (1x30~34V). The transformers can be placed in parallel without any problem (because that's what I'm doing right now). The amount of capacity is no problem...
The load will be an 8 ohm speaker. I normal conditions the amp would play 2 x 100W (rms) into 8 ohm load, but what is the limit I can push the amp to (without blowing any transformer) when we need some more power? (in this case quality of sound isn't that important)

I would like to protect those transformers against too high currents with fuses, what fuses should I use there the max. current in the secondary winding is 4A??

HB.

Nelson Pass · 6th September 2002, 05:21 PM

You should be able to get a nice +-40 volt supply which
will give you enough for about 90 watts into 8 per channel
using two transformers per channel, or four transformers
per channel if you want to get medieval in 2 ohms....

skaara · 6th September 2002, 06:23 PM

hmm whats than "wrong" with leach that it gives "only" 120w into 8 @ +-58V ??

JensRasmussen · 6th September 2002, 08:00 PM

Well nothing is wrong, mine are about 130 W into 8 Ohms and 200 W into 4

\Jens

hugobross · 7th September 2002, 02:08 PM

Nelson,

do you mean that I can handle that with four 120VA transformers with only one secondary winding (maybe this wasn't clear with my explanation above).
so I've build this supply (and have the components for the second one). It would be fantastic if I can drive a 4 ohm load with this psu.

EDIT: the 1khz of the mains isn't correct of course: must be 50Hz

best regards,

HB.

skaara · 7th September 2002, 02:56 PM

+-40v = 90w
+-58v = 120w
Isnt that big difference? Ive seen some other amps that can provide 160-180w at this voltage, why is this one an exception?

hogobross maybe you could use p3a..

JensRasmussen · 7th September 2002, 05:20 PM

Quote:

Originally posted by skaara
Isnt that big difference? Ive seen some other amps that can provide 160-180w at this voltage, why is this one an exception?

Well they must be using magic

\Jens

JensRasmussen · 7th September 2002, 05:22 PM

Hi,

I would use a bridge for each transformer, since they are likly not to be completly identical.

\Jens

hugobross · 7th September 2002, 06:11 PM

Jens,

maybe a good idea, although I didn't have problems with that single bridge. I'm thinking about using a bridge for each two transformers in series, and then connect the outputs in parallel.

do you think I can drive a 4 ohm load with this psu or not? Because I'm a little confused about what I've read about the psu's in the articles I've got here...

HB.

kristijan-k · 7th September 2002, 07:03 PM

Hello,

Here is an example of one other way.

Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip

6th September 2002, 11:22 AM	#1
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	psu question n° ??? I've checked out many amplifier designs, and especially the PSU designs. But there's a big difference in the recommendation for the power of the transformer (sometimes it varies about 2 or 3 times for the same output power). So, I would like to ask you what class AB amplifier (stereo, maybe 4 amps bridged) (?? watts) I can build with 8 transformers of 120 VA (1x30~34V). The transformers can be placed in parallel without any problem (because that's what I'm doing right now). The amount of capacity is no problem... The load will be an 8 ohm speaker. I normal conditions the amp would play 2 x 100W (rms) into 8 ohm load, but what is the limit I can push the amp to (without blowing any transformer) when we need some more power? (in this case quality of sound isn't that important) I would like to protect those transformers against too high currents with fuses, what fuses should I use there the max. current in the secondary winding is 4A?? HB.

6th September 2002, 08:00 PM	#4
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Leach Well nothing is wrong, mine are about 130 W into 8 Ohms and 200 W into 4 \Jens

7th September 2002, 05:22 PM	#8
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	To hugobross Hi, I would use a bridge for each transformer, since they are likly not to be completly identical. \Jens

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6th September 2002, 05:21 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	You should be able to get a nice +-40 volt supply which will give you enough for about 90 watts into 8 per channel using two transformers per channel, or four transformers per channel if you want to get medieval in 2 ohms....

6th September 2002, 06:23 PM	#3
skaara diyAudio Member Join Date: Jun 2002 Location: Europe, Slovenia	hmm whats than "wrong" with leach that it gives "only" 120w into 8 @ +-58V ??

7th September 2002, 02:56 PM	#6
skaara diyAudio Member Join Date: Jun 2002 Location: Europe, Slovenia	+-40v = 90w +-58v = 120w Isnt that big difference? Ive seen some other amps that can provide 160-180w at this voltage, why is this one an exception? hogobross maybe you could use p3a..

7th September 2002, 06:11 PM	#9
hugobross diyAudio Member Join Date: Jun 2001 Location: Flanders, Belgium	Jens, maybe a good idea, although I didn't have problems with that single bridge. I'm thinking about using a bridge for each two transformers in series, and then connect the outputs in parallel. do you think I can drive a 4 ohm load with this psu or not? Because I'm a little confused about what I've read about the psu's in the articles I've got here... HB.

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