How can I modify this grommes little jewel amp for guitar.

DJNUBZ · 18th January 2010, 05:30 AM

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.

planet10 · 18th January 2010, 06:00 AM

Should be able to make a fine gee-tar amp outta that.

dave

Tom Bavis · 18th January 2010, 12:49 PM

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.

DJNUBZ · 18th January 2010, 01:41 PM

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?

Tom Bavis · 18th January 2010, 01:47 PM

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.

OneyedK · 02:20 PM

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...

DJNUBZ · 02:37 PM

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.

planet10 · 20th January 2010, 06:46 AM

Someone is asking a bit much...maybe someone laundering money?

dave

OneyedK · 20th January 2010, 10:30 AM

Quote:

Originally Posted by planet10

Someone is asking a bit much...

I agree, amps age like milk, not like wine...

Palustris · 20th January 2010, 09:19 PM

Can anyone confirm the pricing on this ebay post?

I can confirm that the asking price is completely insane!

18th January 2010, 05:30 AM	#1
DJNUBZ diyAudio Member Join Date: May 2003 Location: Chicago	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. __________________ http://www.caraudioconnoisseur.com/

18th January 2010, 06:00 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Should be able to make a fine gee-tar amp outta that. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

18th January 2010, 01:41 PM	#4
DJNUBZ diyAudio Member Join Date: May 2003 Location: Chicago	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? __________________ http://www.caraudioconnoisseur.com/

18th January 2010, 02:13 PM	#6
OneyedK diyAudio Member Join Date: Oct 2007	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.

19th January 2010, 02:24 PM	#7
DJNUBZ diyAudio Member Join Date: May 2003 Location: Chicago	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. __________________ http://www.caraudioconnoisseur.com/ Last edited by DJNUBZ; 19th January 2010 at 02:37 PM.

18th January 2010, 12:49 PM	#3
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	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.

18th January 2010, 01:47 PM	#5
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	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.

20th January 2010, 06:46 AM	#8
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Someone is asking a bit much...maybe someone laundering money? dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

20th January 2010, 09:19 PM	#10
Palustris diyAudio Member Join Date: Aug 2006 Location: Cape Cod	Can anyone confirm the pricing on this ebay post? I can confirm that the asking price is completely insane!

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