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Old 6th March 2008, 11:06 PM   #1
adrianc is offline adrianc  United Kingdom
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Default increasing ouput on adcom GFP750

i was wondering if there is any way of increasing the ouput voltage on the gfp750 from 1v to around 2v.would there be any detrementle effect of doing this.
could this be achieved by changing the resistors on the oput sidr r 317 r277 r197 and r237.
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Old 7th March 2008, 01:10 AM   #2
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What do you mean by that? I recall that it will do several volts
output if you turn the knob up.
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Old 7th March 2008, 02:04 AM   #3
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>resistors on the oput sidr r 317 r277 r197 and r237.

can you post a schematic ?
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Old 7th March 2008, 03:24 AM   #4
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Switch to active instead of passive?
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Old 7th March 2008, 07:27 AM   #5
adrianc is offline adrianc  United Kingdom
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hi guys

please forgive my lack of terminology, i am l am still learning.
The problem i have is that the output on the preamp to poweramp has a maximum output of 1volt,? the poweramp a gfa5800 requires 1.6v of input for full power output of 250w.
in passive the output is even less, and the power amp is not as loud.
i was looking for a way of increasing the output voltage to 2v so as it would cater for any power amp i wish to use at a later date
i understand that the volume control will regulate the power level to the power amp . but only to 1 volt at the moment.

i place a link later to the schematics

many thanks
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Old 7th March 2008, 07:29 AM   #6
adrianc is offline adrianc  United Kingdom
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http://www.diyaudio.com/forums/attac...amp=1162392670
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Old 7th March 2008, 07:30 AM   #7
adrianc is offline adrianc  United Kingdom
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http://www.diyaudio.com/forums/attac...amp=1162251878

Hope this helps adrian
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Old 7th March 2008, 02:29 PM   #8
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Looking at tje schematic, it will take a 1 volt input and give you
5 volts at its highest gain setting, and with a 57 volt rail, you
aren't likely to run out of voltage swing.
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Old 10th March 2008, 09:40 PM   #9
adrianc is offline adrianc  United Kingdom
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thank you guys for all your help, pre amp sound great, and volume is good, the 1v in the owners manual was misleading.

thanks again
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Old 11th April 2008, 09:51 PM   #10
Heiney9 is offline Heiney9  United States
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Not to mention that power and pre's from the same manufacturer generally are designed to work well together. I take it you didn't have any "hands on" experience just looking at a spec sheet. Not the best way to make a judgment.

Here's one of my favorite quotes; it just happens to be from the "One and Only"

"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not."--Nelson Pass.

Perhaps not fully appropriate for you situation but certainly a great method to live by. Listen, not measure and read specs. Measurements and specs are useful but don't tell the whole story.

Good luck you have a couple of great pieces there.
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