Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Trall on October 08, 2012, 11:22:29 am
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Hello I have Jolida SJ 302a and i love this amp but its to week for my Usher be-718.
So i was wondering if anyone has any idea how to change it to pre-amp.
it has no RCA outputs , guys at Jolida told me that it is possible but did not say anything more.
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Show us the schematic and I will show you where you can connect some RCA ouput jack.
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This is the schematic ;
www.drtube.com/schematics/jolida/sj-502a.gif (http://www.drtube.com/schematics/jolida/sj-502a.gif)
I'll connect a RCA jack at resistor R2 ( 1K) Kathode side of the tube, disconnecting this wire to V2A . I'll add a 0.22 capacitor before the RCA jack to insulate from voltage.
Use shielded wire, grounded at one end only.
Do the same for other channel.
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If you could guide me with some paint job on that schematic i would be eternally grateful.
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> Jolida SJ 302a and i love this amp but its too weak for my Usher be-718.
That's a 60 Watt amplifier. The speakers review well with a 60W amplifier. And 7" woofers shouldn't need (can't handle) a lot more than 60 Watts.
It shouldn't be "to week". Something is wrong.
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If you could guide me with some paint job on that schematic i would be eternally grateful.
I never use paint , I don't know how . I have to learn.
Other explanation ; disconnect the wire from R2, the wire going to R4 and V 2a
In place from R2 you connect a shieded wire to your RCA jack with 0.22 cap in serie
In other word ;
The wire from R2 don't go to R4 and V2a , It go to you RCA jack. Is it ok ?
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Great thank you very much. Usher is very power hungry.
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Great thank you very much. Usher is very power hungry.
The Usher Be-718 loudspeaker is specified as Sensitivity: 87dB/W/m.
It's not "power-hungry" but in-sensitive. You may be used to getting more volume from your Jolida amp with other, more sensitive speakers.