Hi,
I have a 30-0-30 300va (no dual secondaries)custom made EI core transformer which outputs about ~42v DC. It's HUGE (sorry for the caps) and rugged and I really want to keep it and don't mind keeping it separate from the amp unit. Now I'm planning to make a Gainclone stereo amp. I have performed a preliminary forum search and I couldn't find a suitable PSU circuit to regulate the voltage so that I get about 25V to drive two 4ohm speakers (stereo). Can anyone suggest me a suitable PSU circuit? I can design and make a PCB.
Thanks
Vijay
I have a 30-0-30 300va (no dual secondaries)custom made EI core transformer which outputs about ~42v DC. It's HUGE (sorry for the caps) and rugged and I really want to keep it and don't mind keeping it separate from the amp unit. Now I'm planning to make a Gainclone stereo amp. I have performed a preliminary forum search and I couldn't find a suitable PSU circuit to regulate the voltage so that I get about 25V to drive two 4ohm speakers (stereo). Can anyone suggest me a suitable PSU circuit? I can design and make a PCB.
Thanks
Vijay
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Hi Andrew,
Thanks. I have already looked at Decibel Dungeon and I don't think I could find a suitable circuit. However, I found that the two secondary windings can be used separately. The center-tap on the transformer has two cables coming out. Will I be able to identify the two secondaries using a multimeter? I haven't done that yet as I have to do some tinkering before that.
Thanks. I have already looked at Decibel Dungeon and I don't think I could find a suitable circuit. However, I found that the two secondary windings can be used separately. The center-tap on the transformer has two cables coming out. Will I be able to identify the two secondaries using a multimeter? I haven't done that yet as I have to do some tinkering before that.
Well, it looks like I can find out the two secondaries using a multimeter. But before that, I would like to know if there is any other way I can do the PSU without meddling with the center tap.
You dont need to identify the 2 secondaries etc. Use center tap as the ground. The other 2 points of the transformer go to the A/C input of the bridge and you take the + and - from the outputs of the bridge rectifier. Only 1 bridge rectifier is to be used. You need smoothing caps between +, - and the ground. Output voltage will be around 1.41 x Vac - 1 Volt approx.
set the DMM to lowest resistance range. Some have a bleeper on this range to give audible shorted or very low resistance indication.
Insert each transformer lead into a separate receptacle of an insulated terminal strip.
measure the leads to find which are connected together.
A simple/single winding can only have TWO connected leads.
A centre tapped winding will have THREE connected leads.
A multi-tapped winding will have even more connected leads. eg some primaries are wound for 100, 110, 115 and 120Vac operation. This winding would have five leads. 0 to 120Vac will have a higher resistance than the 0 to 115Vac section, etc.
Insert each transformer lead into a separate receptacle of an insulated terminal strip.
measure the leads to find which are connected together.
A simple/single winding can only have TWO connected leads.
A centre tapped winding will have THREE connected leads.
A multi-tapped winding will have even more connected leads. eg some primaries are wound for 100, 110, 115 and 120Vac operation. This winding would have five leads. 0 to 120Vac will have a higher resistance than the 0 to 115Vac section, etc.
You didn't read properly.
Building an LM3886 Gainclone chip amp with a regulated power supply (PSU).
I want to say more but someone will object!
Building an LM3886 Gainclone chip amp with a regulated power supply (PSU).
I want to say more but someone will object!
I actually read that but what I was thinking was if there is any other way to regulate the voltage without messing up the transformer, that is, regulate the output voltage with center tap intact. Hope you got my point.
You can use a +ve regulator on the +ve half output and use a -ve regulator on the -ve half output.
The problem that DD has overcome is using two +ve regulators, because the -ve regulator is not available.
The problem that DD has overcome is using two +ve regulators, because the -ve regulator is not available.
if you used something like the TDA7293/94 for your chipamp you wouldn't need to regulate it down to 25v as they can handle 42v rails ......
Okay, thanks. It looks like I'll have to mess with the center tap for now. I'll do that and report a little later.
Well, I'll save it for later. Symasym is better than that anyway
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