Sound Model X404 - Recap, Ground Mod, Retube

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buildafriend

Well-known member
Joined
Jun 30, 2009
Messages
1,392
Location
Omnipresent NYC
Hi guys,

I have a Sound X404 here that seems to be working great other than a sometimes failing 2 prong power plug. Usually I say if it aint broke don't fix it but the person would like the caps replaced, tubes changed, and a grounded plug added so here go's. I think it's a pretty rare and underrated piece. It seems to handle both bass and guitar very well while coming across as clean and thick. It only breaks up a hair at loud volumes with a strat with regular american pick ups.

I don't see a schematic anywhere online, or recognize the power tube type. Unfortunately there is no label on the power tubes other than RCA. Does anyone recognize these or have a schemo for this amp?
 

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scott2000 said:
7868??

https://cdn.shopify.com/s/files/1/0333/7633/products/1_dc16e8b7-962d-49a4-9f2f-c991ba105bfa.jpg?v=1505071391

It looks close. I want to see if it tests out as one but I don’t want to break the tube tester...
 
There's a mention of the 7868 in another model here...

https://www.premierguitar.com/articles/Souping_up_a_Sound_X-305-R

and here

http://www.tdpri.com/threads/sound-electronics-corp-mineola-ny-model-600.410123/


So maybe a possibility at best???

Good luck!
 
Tubes caps and grounded power plug came in. I installed them all and it sounds much better. I think only have to troubleshoot one bad section that doesn’t “Bass boost” the way it should.

A note to anyone changing these power tubes - the electro harmonix ones will stretch out the output power tube sockets. Once you put them in the old tubes don’t fit right unless you go in with a micro screwdriver and bend the inside of the sockets back. I’m not taking that path, it sounds great with the new tubes. Much brighter and a little louder. It breaks up a little more at loud volumes now. You can hear the tele switch positions much more clearly and there is no amp buzz even at high volumes. This amp is underrated.
 

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