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ward beck modules on +/- 24 v instead of 25v Utility Plugins
Old 4th January 2013
Gear interested

Thread Starter
ward beck modules on +/- 24 v instead of 25v

Hi folks! Anybody here has racked some ward beck module with a +/- 24v PSU instead of +/- 25 volts ??

i'm about to rack some m460b and m470a modules, i know they run on +/-25v, but i have acess to a realy good +/- 24v PSU. and to get
+/-25v, i would need to order another power transformer.

Looking at the schematic i see there is some kind of regulation on the board wich drops down the 25v to +/-18v ( +/-21v on the m460b) but on the m470 i see r134 and r137 drops it to +/- 24 volts to feed Q6-Q9 ...

could i use 24 volts instead of 25v? or if i do, should i bypass these 2 resistors and straight feed +/- 24 volts.

Thanks alot for your input, i'm not enough knowledgeable in electronics to be sure about this one.

i attached a schematic, full manual here:
Attached Thumbnails
ward beck modules on +/- 24 v instead of 25v-ward-beck-m470-schematic-me.jpg  
Old 4th January 2013
Lives for gear
SP2016's Avatar
No problem seen in using your 24v supply.
As you already mentioned there is a regulation down to +/- 18vdc.
So that 1 volt will make no difference.
Old 4th January 2013
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Richard Crowley's Avatar

I agree with SP2015 that the difference between 24V and 25V is unlikely to be significant in this situation. Furthermore, it seems unlikely that getting 25V out of your unidentified "really good" power supply involves a new transformer. Unless it is designed right up at the limits of the transformer in which case it isn't "really good".
Old 4th January 2013
Gear interested

Thread Starter
Thanks for your help!

here is the psu im planning to use for reference:

PSU-2448mk2 Kit

(i said "very good" for me cause i already used them and they are well
built, small and easy to work with. )

I spoke to Ruel (awesome customer service btw) and he said he supplies the kit with a 18-0-18 transformer wich should be good for +/- 24v but might be on the limit for 25v. i would need to find a 22-0-22 and put bigger heatsinks.

back to the m470 schematic, there is a resistor that drops the 25v to 24volts ( r134 and r137, the last booster amp still uses +/- 24volt) should i just bypass them? or else it would probably drop my 24v to 23v, and maybe it would compromise the dynamic range a little?

thanks again for clearing things up for me
Old 4th January 2013
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Ike Zimbel's Avatar

I haven't looked at the schematic, but I wouldn't just bypass them. If you decide you need to take them out, you should replace them with 10ohm resistors of the same wattage and type, and stand them off the board a bit if they are not already like that. These will help prevent serious board damage in the event that the o/p amp fails.
Old 4th January 2013
Lives for gear
SP2016's Avatar
Just use that psu !
Do not bother about the 1v difference as the regulation does not care at all and the modules will not fully load the +/- 24VDC power supply.
Do not care any further. Connect the psu and enjoy your Ward Beck modules.
They deserve it....
Old 5th January 2013
Gear interested

Thread Starter

Thanks alot guys!

i feel a lot more confident! i'll use the 24v supply.

Ike, thanks! thats the kind of info i needed, i was wondering if they were for
some kind of protection, i'll do that.

infinite thanks!
Old 14th January 2013
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hymenoptera's Avatar

thanks for sharing. hope the PSU works out for you.

this 2448 mkII might be just what I need to supply +/- 17v plus 48v to a couple Soundcraft modules I want to rack sometime soon.
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