SuperBee
1561 posts
Dec 04, 2013
4:42 AM
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I just finished testing my new amp...i rebuilt a Valve Junior to run a 6V6.
This was a V3 combo. Now it has a hand-wired board with a 6V6.
well, it was more of an exercise in amp building than anything.
next one i think will be a 5F1 to fit in my hg2 cab
in some ways the amp has gone backwards because its now running AC heaters, and it is a bit noisy when you take your hands off the strings...
oh yeah, i built it primarily as a guitar amp for my daughter.
I also built the board to be pretty much drop-in...so the original board can easily be replaced...just the hole in the chassis is a bit bigger and the retainer for the el84 wont ever go in again
of course...i'm gonna plug a harp mic into this thing...tomorrow..its 1120PM here.
Frankly, I'm just stoked to have built a hand-wired board and have it work pretty well straight up. 315v on the plate, 18.75v on the cathode, 38.7mA plate current for 11.5w plate dissipation. i think thats just within the design spec
No doubt it can suffer some improvement. i expect i'll have it apart again soon enough to fit a standby switch and a fuse on the high voltage line, and a line out...and see if i can quieten that heater...
i do think it has some nice tone for guitar though, as is. it has some better- quality parts now, if nothing else...
from this:
to this:
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Last Edited by SuperBee on Dec 05, 2013 11:28 PM
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Barley Nectar
200 posts
Dec 04, 2013
6:58 AM
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Nice job SuperBee. Is that a cathode biased amp? Or is it fixed bias? If fixed, you may have those 6V6's running a little hot. Fixed bias rule of thumb is, idle current not over 70% of plate dissipation. Cathode bias amps can run at 100% at idle. The plate current actually drops when passing signal.
Now that you got the bug, anything goes. Yahoo...BN
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SuperBee
1562 posts
Dec 04, 2013
12:46 PM
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Yeah it's cathode-biased BN.
I'm afraid I do have the bug. There was no real reason to do this, except I had these old 6v6 tubes. And I saw this board...
And I wanted to build a cool little amp for my daughter. The VJ combo is built in a decent little cab and the V3 speaker is reasonable too IMHO (eminence Lady Luck). As a guitar amp I think it's good for encouraging experimentation with use of pickups and guitar tone and volume, because there isn't too much you can change on the amp!
I really don't need more little amps...
But yeah, little amps it is. Now I'm looking for a broken VJ to bolt my good stock board into. And thinking about upgrading the OT in this one I just built...
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SuperBee
1563 posts
Dec 04, 2013
1:59 PM
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Oh oh oh ...
It sounds GREAT with the harp. I just busted out a few of Dave Barrett's tongue blocking instrumentals, using A, D and G harps.
When I added a bit of LW Delay...that's a sound I'm very happy with.
But.
It's got a bunch of gain. I can't turn the volume knob very far at all before its feedback ville. Oh well, it's a 5 watt amp designed for guitar.
I'm gonna make sure to keep good records of the circuit though. I tested all the resistors before I fitted them. I know there are a couple which had drifted up quite a way from their nominated values.
Maybe I'm just full of new dad pride...but I do think this is the best (blues)harp sound I've had from an amp.
I think I might swap a 12ay7 in, 'just to find out' ;0)
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HawkeyeKane
2193 posts
Dec 04, 2013
2:26 PM
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"It's got a bunch of gain. I can't turn the volume knob very far at all before its feedback ville. Oh well, it's a 5 watt amp designed for guitar."
Would any of the EVJ preamp mods from Lone Wolf help you there?
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Hawkeye Kane
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SuperBee
1565 posts
Dec 04, 2013
5:34 PM
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yeah i expect so Tim, but the harp tone is just incidental on this one. this is bound for my daughter to use as her guitar practice/jam amp, so i'll not make any harp-specific changes until she tires of it...which may be never.
i may build another one though... :0)
ive got my mind set on a 5F1 for my next build, but i know the stock board i removed from this epi is gonna bug me until i do something with it. definitely going to be checking out Randy's mods real soon.
i think i better leave the amp building alone for a couple of weeks now though.
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Barley Nectar
202 posts
Dec 04, 2013
7:48 PM
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Aww Comeon. Build a Tweed Harvard. Fantastic for harp. I built my first one out of a Zenith console chassis with one 10" speaker. The wood is salvage 100 yr old flooring from a collage stage. A lot of mojo in that wood. I gave this one to my brother...
Last Edited by Barley Nectar on Dec 04, 2013 7:52 PM
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SuperBee
1569 posts
Dec 04, 2013
9:32 PM
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very nice BN!
thats a good idea. might have to go there. i plan on a 5F1 because i need to put this little HG2 cab to good use.
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arnenym
239 posts
Dec 05, 2013
4:07 AM
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Superbee. Nice work with the eyelet board! It be a hot gain amp because you're not have a tone control. A tonecontrol cut a lot of signal and drop it to ground.
BN What model of Harvard is it?
Beautiful cab. - I wanna have it..
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Barley Nectar
203 posts
Dec 05, 2013
4:25 PM
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Arny, That is the 5F10. This circuit turned into the Vibrolux and the Tweed Bandmaster. Both great harp amps! I like it so well I built one for myself. Mine is a little different though. It's two Harvards on one PS/chassis. Stereo Harvard, 35W per channel w/ NFB defeat and two line outs but you don't need them. Runs 2x6L6WGB's per side, seprate OT's of corse. This thing has some serious grunt!
I run it thru these babies that I built. 2X10 Jensen P10P and a Ragin Cajun in each.
Sorry I stole the thread SuperBee. Just trying to inspire you.
Last Edited by Barley Nectar on Dec 05, 2013 4:32 PM
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SuperBee
1570 posts
Dec 05, 2013
10:32 PM
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It's cool! I like that stuff. I have to get some stuff together and make use of this empty cab, and then I think it's time to get back to my '48 filmosound. That really just needs some work to enclose it properly.
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arnenym
240 posts
Dec 06, 2013
12:14 PM
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BN. "Both great harp amps! I like it so well I built one for myself. Mine is a little different though"
Hmm ;) ;) Hahaha.
Maybe,, just maybe you should call it "inspered of" or "loosely based on" a Harvard insted of a type of harvard? ;)
Cool build. I don't argue about the serious grunt. Do you use two 6AT6 for the pream or one double triode?
Superbee.
I got a filmosound amp. I don't tried it. I have to get a step down transformer from 230-110 Volts and change to a 3 prong cord before i test it.
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Barley Nectar
205 posts
Dec 06, 2013
12:52 PM
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Arney, I use a dual triode for V1. V1a is the input for channel 1. V1b is the input for channel 2. Currently there is a GE ***** 5751 in V1. If you look, Fender used a 6AT6 and also a 6AV6 in V1 on the Harvard. Depending on which schmo you look at. I believe the 6AV6 is the higher gain of the two. This triode is the same as one side of a 12AX7. I also used the Marshall 2204 type bias supply in the Harvard "inspired" stereo amp. LOL...
My next step is to remove it from the temporary Flag cab. I will build a V front cab using the same wood as my brothers amp above. It will get 4 Weber 6x9's, two per channel on floating baffles.
BTW SuperBee, you did a nice job on that little board. For some reason, I didn't see the pics before...BN
Last Edited by Barley Nectar on Dec 06, 2013 12:54 PM
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SuperBee
1573 posts
Dec 07, 2013
5:12 PM
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Thanks BN. Yeah I went back and put some code around my link...and added a shot of the original board
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