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Base theme by DesignModo & ported to Powered by Vanilla by Chris Ireland, modified by the "theFB" team.
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Looks good! Can’t wait to start mine, when funds permit.
Todays progress was building a variable power board and bolting/wiring it in. I'm going to run the amp without it first, to make sure all's working ok, then put it into circuit.
Looking forward to seeing pic's of your build when you get going.
Photo shows up flux spots from soldering, I'll give it a clean up.
I'm going to fit the 0.022uF coupling cap directly on the V2 valve base, hence the unused turret.
On the first filter cap I've got a link to the 4K7 dropper. That'll be removed when I've got it working and I'll bring the variable power output in there. The output transformer centre tap will come off the same point (4K7).
Don't know if it makes any odds but I worked out the foil direction on the coupling caps and oriented them accordingly. Two of them ran one way with respect to the writing and two the other, hence I paired them as you see. Never bothered before but I'm keen to see how quiet I can make this amp, without going too overboard.
The resistors are all Vishay 2W metal film. I've got some carbon comp's I might try later just on V2, i.e. the 100K V2A anode load and the 2 x 56K's on V2B. Maybe also the 2 x 220K grid leaks. I've always used carbon or metal film on other builds but might be fun once it's working to see if it makes any difference (apart from noise).
Thought I'd test the variable power board in advance of finishing the build. I strapped one 16uF cap across the rectifier output and put a DMM at that point and another downstream of the mosfet. Light bulb limiter in place and buttocks firmly clenched...
440V ish raw output, no load. Power control varies that down to about 70V. This was halfway up, 286V.
Transformer should hopefully arrive next week then I might get some sound out of it!
(formerly miserneil)
It had an outing to the LPF meet in Stockport last year where we had about 12 juniors and specials from '55 to '60 and hence a gloriously loud P90 shoot out through an amazing sounding Gartone Tweed Deluxe, which is what inspired this build. My special was not quite as beefy sounding as some of the early Juniors, more detailed, less compressed. Pretty similar to a DC 59 special that was there. It made a wonderful sound through the Gartone.
So now, a bit of hum with either Volume on 0 which fades as you turn up - that normal for these amps or is that a clue to possibly a poor ground somewhere?
The variable power works well. I think it'll be useful at a gig or rehearsal to take the level down a little and preserve the tone. You can knock it right back and whilst it doesn't get fizzy like an attenuator might it loses the tone somewhat.
Planning on taking it to a rehearsal room so I can properly crank it beyond domestic levels but from the few brief loud moments I've tried with it I think it's going to be a winner. It absolutely loves a Strat, match made in heaven. Can get a bit ragged and wooly with humbuckers but I think that's par for the course with these.
I've played around with valves a little. Currently an NOS Phillips 5Y3, a pair of new Tung-Sol 6V6GT's, a Mullard 12AX7 (yep, marked as such, not ECC83) and a TAD 12AY7. I've got a NOS pair of CBS Hytron 6V6's but in early tests one was pulling a fair bit more current than the other. Might re-visit those.
Here's a couple of pic's:
Power control is in the Ground/Standy hole.
Gentle word of warning from someone who has built the same (with a Tayden Ace), and then thought yeah, upgrade to 6L6 power:
a) you need to be sure that your trannies are up to it - and...
b) you are likely going to need to make a new speaker baffle - as a 6L6 may well snag the speaker bell (does in my case !). Looks like it will in your case as well.
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
Can only imagine how satisfying it must be to build it for yourself!
Pretty much there though apart from some residual hum and noise which is probably typical for these but it's noticable in a quiet home environment - would been more than fine for a gig.
I also need to find somewhere I can run it at gig level and get a proper feel for the distortion - that might show up any lurking problems. Like fizz in note tails that can be any number of things. I'll probably pony up for a rehearsal room and give it a good thrash.
I split the power section and pre amp grounding which is what I think you have also done. On the pre amp I went with a ground bus back to the input jacks. I was running jj6v6 at first but switched to tad 6v6. I liked the sound but there was too much flubby bass. I went back to the JJ 6v6 because they tighten up the low end and I think I prefer the higher headroom. Mine has a 10 inch jensen p10r. Its finally broken in and sounds fantastic.
@kreggs - I've got one bolt near the PT with the HT centre tap, 6V6 cathode resistor, first filter cap and the ground from the variable power stage. I did have the heater centre tap from the 2 x 100R resistors there too but it seems to prefer that point going to the pre-amp. The pre-amp ground being a bit of solid wire between the volume pots (tags, not the back of the pots) with the input jacks wired wired to that. So the pre-amp goes to ground via the 4 jacks (I've got but haven't used the isolating shoulder washers).
The Tung-Sol 6V6's sound good. I'm going to give the NOS CBS/Hytrons another go. I ran it first with them and put the hum partially down to the imbalance between them - one pulls more current than the other. Now I've tarted up the grounding and got the noise down I'll give them another go.
What are using in the pre-amp for yours? I've got another thread running about 12AY7's. I've discovered the frying bacon noise on the bright channel isn't a dodgy solder joint it's one triode in the JJ 12AY7 I was using! The TAD doesn't have that problem, and has lower hiss too. Got a Harma (selected Reflektor/EH) 12AY7 on the way for comparison.