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Dirty-South Blues Harp forum: wail on! >
Epi VJ head/Harley Benton GA5H/Legacy Valve Head
Epi VJ head/Harley Benton GA5H/Legacy Valve Head
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SuperBee
1036 posts
Mar 31, 2013
6:16 AM
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A while back I scored a Mk3 Epi VJ combo, which I was gonna modify. Not long after I picked up a Legacy Valve Head, which I found was much friendlier for harp.
It puzzled me though. I'd heard these amps were just re-badged Epi VJs, and in appearance they are almost identical. The only obvious difference is the Legacy has an "Eq" control. This makes it very similiar to an amp which was sold in Europe as Harley Benton GA5H. I worried why it was so much tamer than my Epi.
I took the amp apart to have a look. Turns out its identical to the HB, right down to the detail of being wired for 230 vac mains power, despite being sold into Australian market.
Essentially it's an Epi VJ head, with a grunt-sucking tone circuit.
There was obvious discolouration (from heat) around the EL84. the wires leading to the tone control mini-pcb had melted insulation.
I decided the time was right to modify this amp. (The Epi VJ mk3 is doing duty as a guitar amp and it sounds ok. I'll leave it for now.)
(The first change was to convert it to run from 240vac!.)
I just got through installing the mods. I guess it may have been wise to do 1 at a time, but the line out, standby, and HT fuse all seemed desirable as did dumping the stock eq and installing Nigel's treble cut kit. I understand that old Eq was the main reason the amp had such reduced volume compared to the "eq-less" epiphone version.
Anyway, no chance to test anything yet. Home tomorrow, and I'll be able to plug in a speaker and power up for the multimeter.
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Last Edited by SuperBee on Mar 31, 2013 6:20 AM
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SuperBee
1038 posts
Apr 01, 2013
4:14 AM
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I didn't die.
i have to revisit my line out, but everything else is working as it should. this thing is now every bit as loud as my valve junior combo.
sounds pretty good i think. the el84 is now measuring 305v on pin 7 and 9.45v on pin 3. i measured 39.9mA on the lead to the output tranny. i didn't measure it before the mods but i believe those numbers are now within spec for the tube anyway.
thats my first hands-on experience with working on a valve amp...i think it was an ok place to start.
i think though this amp is now rather loud for the bedroom, oh well, it seems to have a bit of cut, i'll try it with the band...after i attend to that line out...
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Last Edited by SuperBee on Apr 01, 2013 4:15 AM
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SuperBee
1049 posts
Apr 07, 2013
5:17 AM
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I got the line out working, but I'm puzzled by an observation I made while I was doing it. I soldered a 100R resistor across the tip and sleeve contacts for the jack, a 20R resistor to the sleeve, and a 2K2 resistor to the tip contact.
The 20R and 2K2 resistors were connected between the new line out jack and an existing speaker jack.
To check I had continuity I put the multimeter across all the connections. Tip to sleeve was around 100ohms, sleeve to sleeve around 20ohms. I.E. about the values of the resistors between those points. Tip to tip though was 114. I gather that's telling me there is an easier path than via that 2200ohm resistor, but where is the flow?
I guess I'd see it if I looked at the schematic. I'll do that in a sec, but guess I may as well post this in the meantime...
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arnenym
125 posts
Apr 07, 2013
5:50 AM
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Watch out. Modify amps is addictive! ;)
In europe they sell copies of epiphone Valve junior as Harley Benton GA-5. I bought one and it had a circuit board from epiphone :D
Last Edited by arnenym on Apr 07, 2013 5:53 AM
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SuperBee
1050 posts
Apr 07, 2013
6:01 AM
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Yeah Arne, this is the very same as the GA5H. Just in a black box instead of a blonde, with the words Harley Benton crossed out and Legacy written on in crayon (;0) but electronically identical.
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5F6H
1603 posts
Apr 07, 2013
9:54 AM
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"I got the line out working, but I'm puzzled by an observation I made while I was doing it. I soldered a 100R resistor across the tip and sleeve contacts for the jack, a 20R resistor to the sleeve, and a 2K2 resistor to the tip contact."
Sorry Superbee, what is the 20R for? 2.2K from speaker jack tip to line out tip, 100R from line out tip to sleeve gives you a 20:1 drop ratio, about 250mVAC out at 5W, 500mVAC out at 16ohms.
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SuperBee
1051 posts
Apr 07, 2013
4:03 PM
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Hi Mark, I believe the idea is to reduce potential hum in the line out by grounding the sleeve. I guess this would only be of value if there was a problem with the ground of the slave amp. I confess I'm just following instructions here. Hence the ignorance evident in my question.
I need to take a closer look at the triple speaker out of the Legacy head.
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SuperBee
1055 posts
Apr 09, 2013
7:34 AM
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I tried this unit out in the practice room last night through a peavey valve king 4x12" cab, up against drums, double bass, strat/deluxe. Plenty of volume and sounded fine. So tonight I took it to the open mic in the city with the 2x8" cab (weber 8A100) and it went over a treat. Just mic'ed it with a 57...great night down there. Our first outing with the duo, nice house, full bill...and the organiser made a point of asking us back for their anniversary show next month so it must have been ok...despite me playing wish you would in A instead of G (I do it in A with the band, but usually G in the duo...Adam just realised it was easier for him to change than me...bless him!)
Anyway, I'm happy with this little rig and I've found the venues for it so ...yay!
Thanks Alnicomagnet for the mods and instructions. Really easy to follow for a newbie like me. I enjoyed the process, learned a bit, and got a cool little amp as a result!
I still like my VibroChamp XD, but this one is more personal...
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