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Old 18th January 2010, 05:30 AM   #1
JZatopa is offline JZatopa  United States
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Default How can I modify this grommes little jewel amp for guitar.

I have a single Grommes LJ-6 mono amp and since I have enough stereo gear I think I would like to use it as a guitar amp. I have found a review and schematics here http://www.grommesprecision.com/grom...ewelreview.PDF. I haven't worked on any electronics in a while so I could use a little walk through. Is there more to it then just changing one of the rca's to a 1/4" jack but I am not sure what.
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Old 18th January 2010, 06:00 AM   #2
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Should be able to make a fine gee-tar amp outta that.

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Old 18th January 2010, 12:49 PM   #3
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I suggest you compare the circuit to a Fender or other amp of your liking - and change the circuit to match. The preamp is equalized for RIAA phono - you want a flat response. The tone controls will have little affect in the guitar frequency range. The large amount of negative feedback will result in an abrupt transition into nasty distortion as you overdrive it. The makers of guitar amps have learned how to make good-sounding amps - take advantage of their experience.
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Old 18th January 2010, 01:41 PM   #4
JZatopa is offline JZatopa  United States
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only one of the inputs is RIAA phone. The rest are not. To just get started can I just replace one of the RCA's with a 1/4" jack or does a guitar need something different between the jack and input then an audio input?
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Old 18th January 2010, 01:47 PM   #5
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The phono input is the only one with enough gain for a guitar - the other inputs need a higher level input (SOME pedals have enough output to drive them...). Try it. You WON'T like it. Hi-fi amps are not guitar amps.
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Old 18th January 2010, 02:13 PM   #6
OneyedK is offline OneyedK  Belgium
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Looks like a solid base to build a Fender deluxe 5E3 clone...

deluxe_5e3_schem.pdf

You can even buy a loaded_fender_5e3_tweed_deluxe board and start from there.

The Grommes, the way it is, will simply sound bad for guitar...

Last edited by OneyedK; 18th January 2010 at 02:20 PM.
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Old 19th January 2010, 02:24 PM   #7
JZatopa is offline JZatopa  United States
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Looks like this has been done before.

Grommes Little Jewel conversion

Custom Designed Guitar Tube Amp

I am now debating if I should find a matching amp to make a stereo setup for some reason, sell it or make it a guitar amp.

Looking at the circuit could this design be made to sound good by today's standards without totally gutting it and redesigning it?


*edit* Can anyone confirm the pricing on this ebay post? http://cgi.ebay.com/Grommes-Precisio...item35a3b09e58

I thought these amps sold for $20-$50 now a days.

Last edited by JZatopa; 19th January 2010 at 02:37 PM.
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Old 20th January 2010, 06:46 AM   #8
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Someone is asking a bit much...maybe someone laundering money?

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Old 20th January 2010, 10:30 AM   #9
OneyedK is offline OneyedK  Belgium
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Quote:
Originally Posted by planet10 View Post
Someone is asking a bit much...
I agree, amps age like milk, not like wine...
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Old 20th January 2010, 09:19 PM   #10
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Can anyone confirm the pricing on this ebay post?

I can confirm that the asking price is completely insane!
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