psu for grado ra1?

**oldson** · 15-10-2012, 11:22

does anyone know where i could get one of these.

drew a blank at maplin & rs.

12v output is via 4pin din.

thanks

**Puffin** · 15-10-2012, 16:29

I can't understand why the power supply has a 4 pin din. The power supply is a split rail supply (said to be provided by two 9v batteries?) therefore there is 18+ 0v 18- which would require only 3 pins. I have found this link which others (who probably have more technical knowledge than me!) might like to comment on.

http://diyaudioprojects.blogspot.co....amplifier.html

If you simply require a split rail supply then these are a doddle to make.

Rob.

**oldson** · 15-10-2012, 17:57

Originally Posted by Puffin

I can't understand why the power supply has a 4 pin din. The power supply is a split rail supply (said to be provided by two 9v batteries?) therefore there is 18+ 0v 18- which would require only 3 pins. I have found this link which others (who probably have more technical knowledge than me!) might like to comment on.

http://diyaudioprojects.blogspot.co....amplifier.html

If you simply require a split rail supply then these are a doddle to make.

Rob.

hi Rob
mine is not the battery version, its the AC one.

bought off ebay one night following too many shandys

it is supplied with a 110vac to 12vdc (4pin din) psu.

cant even try the amp until i replace the psu.
when i know it works, it will go straight back on ebay.
you live'n learn, eh

**Puffin** · 15-10-2012, 18:13

Are you sure it is the right PSU?

If it is, then it would need to be a split rail supply. I see no reason why you could not use either a split rail DC suppply (either battery or mains powered - 240vac, converted to DC) provided you can identify which pins go to +/-/0v. Opening the case would tell you.

**oldson** · 15-10-2012, 18:45

Originally Posted by Puffin

Are you sure it is the right PSU?

If it is, then it would need to be a split rail supply. I see no reason why you could not use either a split rail DC suppply (either battery or mains powered - 240vac, converted to DC) provided you can identify which pins go to +/-/0v. Opening the case would tell you.

yeah i am as sure as i can be.

i am not as technically minded on this as you.
so this "split rail" supply does not mean a lot to me.

ironically , i dont want to keep the amp anyway.
i just want to sell it as working , with a uk usable psu.

**Puffin** · 15-10-2012, 19:31

I am not sure that you will easily (or maybe at all) find an off the shelf split rail power supply. However they are very easy to make. You will see reference in the link I posted to a C-Moy amp. I have made several of these with split rail supplies. The Grado RA1 is basically a C-Moy amp.

Of course it has just occurred to me that the simplest thing to do would be buy a step-up converter from 110v to 240v

http://www.maplin.co.uk/300w-uk-to-u...nvertor-265288

**oldson** · 17-10-2012, 22:02

http://www.lpgear.com/product/GRADORA1PS.html

went for this in the end. could not find cheaper alternative.

at least with this, and if the amp works, i will have some re-sale chance.
cheers

**Puffin** · 18-10-2012, 13:38

Keep us posted. I am intrigued as to what the +5v feed is for.

**oldson** · 06-11-2012, 19:23

psu arrived today, and appears to be totally useless.
it has a 5-pin output plug, and the ra-1's input is only 4-pin.
looks like i've been had.

**Puffin** · 06-11-2012, 19:29

What does the product info say the PS is for and what are the voltages of the 5 pins?

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