SuperBee
3130 posts
Dec 27, 2015
2:54 AM
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i know this topic was probably done to death the first time around, but i'm a slow starter and ive just got around to it...
and i know i started a thread a couple weeks ago about big amps, but i also enjoy building these little amps for fun
This Valve Jr started out as Mk3 Combo. a while back i removed the PCB and replaced it with a hand-wired board which essentially emulated the original circuit, with a few small changes...like replacing the EL84 with a 6V6:
i dunno if that pic is too big...if so it means your looking at it while i'm in the process of editing...
here is the layout of the 6V6 mod. this is prior to doing the LW mod:
even though it now runs AC heaters, and as you can see there is not much attention to lead dress, no twisting of heater leads etc...it is very quiet.
this was gonna be a guitar amp but while it was ok for guitar it was really nothing special so i put it aside and eventually i decided to do the LW mod, and just forget about the fact i'd already done a 6V6 mod.
and then i became involved in repairing harps and i just didnt have the energy for both things simultaneously...but at the moment i have a clear bench and so i broke the soldering iron out and got stuck into the LW mod..
which is really a fairly straight forward process...it didn't really make much difference that i was working on a hand-wired board instead of a PCB.
heres the thing with the LW mods in place..but before i installed the treble cut:
i did Randy's 'option 2' which mainly differs from option 1 in that it has a single input rather than 2. in essence the mod is about the preamp, dropping the gain by removing the cathode bypass caps from both preamp stages and dropping the voltage on the plates of the preamp by increasing the value of the voltage dropping resistor. there are a couple of other changes too. i opted to instal the treble cut tone pot, which is perhaps the hardest part, only because it requires drilling a hole in the right place..
the important part is how it sounds...
with the stock 8" lady luck, it sounds ok but really...its an 8" speaker sound...not bad at moderate volume but inclined to nasality...if thats a word...the amp is much easier to control than when stock and i think the tone is a bit fatter, smoother, other words that may not mean much...however i plugged it into a closed back 8 ohm 20 watt 12" cab and that was a different deal
its still not the biggest sound but in a jam with bass, drums, 2 guitars and vocals it was definitely there and sounding good. i took a risk taking it to jam but in the room it sounded good. i'm actually quite impressed with it
i know the VHT 6 has pretty much taken over as the popular cheap amp, which makes sense since its been 5 years or more since the Valve Jr was produced,
but there are still a few valve jrs around and they are cheap enough...i have 3 and haven't paid more than $180 for any of them. i think this is still a viable unit for someone looking at a diy practice amp for garage jams and quiet gigs.
Last Edited by SuperBee on Dec 27, 2015 3:22 AM
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Barley Nectar
1001 posts
Dec 27, 2015
1:21 PM
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SuuuperBee. I also used the LW, VJ single input preamp configuration when I built my 5F6H inspired "Honker"
This amp uses a rare screen feed self inverting push pull power amp configuration that Mark experimented with and runs EL84 finals. There is no phase inverter used in a SFSI configuration. I built this amp using a salvage Hammond AO44 reverb chassis and iron. Nice platform! Added one 9 pin socket to chassis. Amp is housed in an ancient 1x10 tweed cab that I found in a barn covered with pigeon poop! Amp makes 6W clean and 16W max. Sounds fantastic thru a vintage Jensen C10P. This amp is gigable also and is freakishly strong. I'll see if I have some pics.
Randy gave us some nice circuits to work with but I think the VJ schematic has been pulled down from his site. Pitty that...BN
Last Edited by Barley Nectar on Dec 27, 2015 1:33 PM
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SuperBee
3131 posts
Dec 27, 2015
1:44 PM
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Wow! That's a funky unit BN!
The Valve Jr project is still up on the Lone Wolf site. I also thought they'd gone and was counting my blessings that I've made hard copy, but next time I looked all the projects were where they've always been.
Which I'm pleased about because I'm just starting on the SE6L6, converting one of the cheap Chinese 'champ' amps. I bought a so-called 'Strauss' SHW-10, $150 NOS. it's a champ circuit running a 6L6 and a 10" speaker. Possibly the worst-sounding harp amp I've ever plugged into. So I figure why not rebuild it...basically it's a cheap kit.
I agree, Randy has done some good work on his site and made a generous contribution to share these projects.
Your use of the valve Jr preamp design is a good example. It's a solid idea for getting a good sound out of a harp mic to the power amp.
Last Edited by SuperBee on Dec 27, 2015 1:47 PM
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Barley Nectar
1003 posts
Dec 28, 2015
7:20 AM
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Go git um Supe. Good luck with the SE6L6. They get good reviews...BN
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eetechTom
14 posts
Dec 29, 2015
10:01 AM
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Cool stuff. I'm in the process of building the SE6L6 myself. Adding a VVR circuit to it. It's going into a Fender Sidekick Bass cabinet with stock 10" speaker. Plan on a speaker upgrade at some point.
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blueswannabe
587 posts
Dec 30, 2015
5:05 PM
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Here is a 1954 Supro Spectator Clone I just built. Great tone!
Last Edited by blueswannabe on Dec 30, 2015 5:09 PM
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SuperBee
3154 posts
Dec 30, 2015
7:35 PM
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i like that! is that a 5Y3 rectifier? and the preamp? 6SL7? Tone seems same set up as i used in my other harp epi, though not sure of component values.
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blueswannabe
589 posts
Dec 30, 2015
8:41 PM
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@superbee, yes, 5y3, 6v6, 6sl7
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Barley Nectar
1013 posts
Dec 30, 2015
9:07 PM
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Nice job BW. True point to point. Everything is get toable. Try an trim those little wire ends at the solder lugs. They become little antennas and can create noise. That tweed looks nice also, nice color...BN
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SuperBee
3156 posts
Dec 30, 2015
10:36 PM
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I'm getting cexcited about building amps again!...had to break out my 5F1 for a blow this arvo...got my daughter out of bed (yes, this arvo)..waiting on my parts order to come in...might have to have a crack at something bigger...
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Barley Nectar
1016 posts
Dec 31, 2015
7:09 AM
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Everyone builds the 5F1 with the 12AX7, I built a 5C1 Champ once with the 6SJ7 Pentode preamp. That thing was awesome! Simple circuit too. What the hell is an arvo?
Bigger amp, hell ya, now your talkin. Your ready. How bout my Masco Hybrid. Fairly simple and great tone. About 18W clean IIRC. Here is the build thread. http://www.modernbluesharmonica.com/board/board_topic/5560960/5483695.htm?page=2
Last Edited by Barley Nectar on Dec 31, 2015 7:20 AM
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SuperBee
3160 posts
Dec 31, 2015
12:32 PM
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Haha, "arvo" = afternoon
Same way that david becomes davo and bottleshop becomes a bottle-o i think
Good-o
Thanks for the link, i'll check it out later. Happynew year.
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blueswannabe
590 posts
Dec 31, 2015
5:59 PM
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@BN, thanks ! amp building is very addictive! tha masco looks real nice as does superbee's EPI Vale JR.
really like the octal pre-amps.
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blueswannabe
591 posts
Dec 31, 2015
5:59 PM
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@BN, thanks ! amp building is very addictive! tha masco looks real nice as does superbee's EPI Vale JR.
really like the octal pre-amps.
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