JLM PEQ500 with 16v DOA's good for 24v use?

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mahe66
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JLM PEQ500 with 16v DOA's good for 24v use?

Post by mahe66 »

Hi I just bought a used PEQ500 with two JLM99v DOA's marked with "+/- 16volt", and my question is:

Is it possible to use this PEQ500 with a +/- 24volt PSU for increased audio headroom (... my intention is to put the 500 module in a separate box with external PSU).

Kind regards
/ Mattias

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Joe Malone
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Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by Joe Malone »

mahe66 wrote:Hi I just bought a used PEQ500 with two JLM99v DOA's marked with "+/- 16volt", and my question is:

Is it possible to use this PEQ500 with a +/- 24volt PSU for increased audio headroom (... my intention is to put the 500 module in a separate box with external PSU).

Kind regards
/ Mattias
Yes the audio circuit is fine as the 99v +/-16v to +/-24v opamps are used in the PEQ500.

The bypass relay will be driven with a few more volts as will the leds but that should be fine.

Otherwise ideally you would change R12 from 1k to 2k2 so the relay ran at it correct voltage.
Joe :-)
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mahe66
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Joined: Sun Nov 24, 2013 1:38 am

Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by mahe66 »

Changed the R12 and it works like charm! :)

Thx!

A question about the gain trim pot, what is it doing? I thought it might be possible to change the vol/gain to "unity gain" but its not... hope i didn't ruin anything when trying to adjust the gain trim.

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Joe Malone
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Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by Joe Malone »

mahe66 wrote:Changed the R12 and it works like charm! :)

Thx!

A question about the gain trim pot, what is it doing? I thought it might be possible to change the vol/gain to "unity gain" but its not... hope i didn't ruin anything when trying to adjust the gain trim.
The trim pot is for matching pairs of PEQ500 gain wise. If you cannot drop the level to unity change R15 to the next largest standard value and re-adjust the trimpot for unity.

Or put 1k load resistor across the balanced output of the PEQ500 and you should be able to adjust unity gain without changing R15. Note trimpot is 25 full turns from one end to the other.
Joe :-)
JLM Audio
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mahe66
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Joined: Sun Nov 24, 2013 1:38 am

Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by mahe66 »

Thanks for your support! I did get a little confused after reading that I supposedly was about to drop the output level, mine was about 6dB low already... I then remembered reading somewhere that if the output wasn't hooked up right (using both sides of the output-transformer... ), there would be a 6dB loss. And I found out that I didn't get the cabling from the edge connector to the XLR out right... Fixed it and now it works just fine!

Thanx!
/ Mattias

mahe66
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Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by mahe66 »

Those DOA's in the PEQ500, which is input buffer and which is for makeup gain and driving output transformer?

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Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by Joe Malone »

mahe66 wrote:Those DOA's in the PEQ500, which is input buffer and which is for makeup gain and driving output transformer?
Input buffer is closest to the front panel
Output amp is closest to the edge connector
Joe :-)
JLM Audio
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mahe66
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Joined: Sun Nov 24, 2013 1:38 am

Re: JLM PEQ500 with 16v DOA's good for 24v use?

Post by mahe66 »

Joe Malone wrote:
mahe66 wrote:Those DOA's in the PEQ500, which is input buffer and which is for makeup gain and driving output transformer?
Input buffer is closest to the front panel
Output amp is closest to the edge connector
Thx! :)

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