casework
Thanks for the compliment Ben. For the casework I put my long woodworking hobby to work along with some English Walnut I had laying around (still need to put some nobs on the front!). Top deck is 1/8 inch thick aluminum from an old street sign, i belt-sanded off the reflective sign lettering and graphics, then sanded smooth with about 200 grit paper, then used a random-orbit sander and 320 grit paper to put a nice, subtle swirly pattern on it. Followed with a coat of clear laquer on the top surface.
Thanks for the compliment Ben. For the casework I put my long woodworking hobby to work along with some English Walnut I had laying around (still need to put some nobs on the front!). Top deck is 1/8 inch thick aluminum from an old street sign, i belt-sanded off the reflective sign lettering and graphics, then sanded smooth with about 200 grit paper, then used a random-orbit sander and 320 grit paper to put a nice, subtle swirly pattern on it. Followed with a coat of clear laquer on the top surface.
Congratulations on your build! This was my first push pull amp and I loved it. Then I swapped it with a friend for a weekend and never saw it again.
I remember I had to fiddle with the feedback resistor / cap combo for a bit, but EC8010 walked me through his variable air capacitor calibration trick and I eventually got the feedback where I wanted it and eliminated some lingering oscillation.
See here:
http://www.diyaudio.com/forums/tubes-valves/99218-kofi-annan-oscillatin-bevois-valley-8.html#post1220238
Going back through these posts reminded me what a great forum this is and what a great group of people we have.
Good luck with your BV.
Kofi
I remember I had to fiddle with the feedback resistor / cap combo for a bit, but EC8010 walked me through his variable air capacitor calibration trick and I eventually got the feedback where I wanted it and eliminated some lingering oscillation.
See here:
http://www.diyaudio.com/forums/tubes-valves/99218-kofi-annan-oscillatin-bevois-valley-8.html#post1220238
Going back through these posts reminded me what a great forum this is and what a great group of people we have.
Good luck with your BV.
Kofi
follow-up on the my new bevois valley amp
I scoped a little deeper into the 'fuzzyness' of the square waves shown a few posts back, stretching the time scale way out, etc., and comparing to the source square waves. From what I could see (through noob eyes) the high frequency component on the amplified wave matches a high frequency component on the square wave from my old RCA WA-504 audio generator. So my guess is its not ringing or oscillation in the amp?? Also, I forgot to mention a possibly important point: the scope images in my previous post were with the amp connected to speakers. When I got around to putting together a dummy load and hooked that up, the curves looked a lot 'nicer' (didn't change the high freq fuzzy, but they were squarer). Anyway, amp sounds great, classical piano, for example sounds like the piano is in the room, so no more tweaking for now.
One last thing, for constructing the circuits I used cheap perf board and small copper-plated brads or tacks inserted from the bottom up. I had to drill the holes a little larger to fit them. Then put a small bead of solder around the base of the shaft of each brad on the front side of the board to secure them in place. The copper plate wets quick and easy with solder and soldering components later higher up the shaft didn't melt the base solder. I built a guitar amp like this last year, still going strong after couple hundred hours. A big sheet of perf board was about 3 bucks at 'the shack', the copper 'weather strip nails' were about 2 bucks per hundred at hardware store. Cheap. Like me.
I scoped a little deeper into the 'fuzzyness' of the square waves shown a few posts back, stretching the time scale way out, etc., and comparing to the source square waves. From what I could see (through noob eyes) the high frequency component on the amplified wave matches a high frequency component on the square wave from my old RCA WA-504 audio generator. So my guess is its not ringing or oscillation in the amp?? Also, I forgot to mention a possibly important point: the scope images in my previous post were with the amp connected to speakers. When I got around to putting together a dummy load and hooked that up, the curves looked a lot 'nicer' (didn't change the high freq fuzzy, but they were squarer). Anyway, amp sounds great, classical piano, for example sounds like the piano is in the room, so no more tweaking for now.
One last thing, for constructing the circuits I used cheap perf board and small copper-plated brads or tacks inserted from the bottom up. I had to drill the holes a little larger to fit them. Then put a small bead of solder around the base of the shaft of each brad on the front side of the board to secure them in place. The copper plate wets quick and easy with solder and soldering components later higher up the shaft didn't melt the base solder. I built a guitar amp like this last year, still going strong after couple hundred hours. A big sheet of perf board was about 3 bucks at 'the shack', the copper 'weather strip nails' were about 2 bucks per hundred at hardware store. Cheap. Like me.
I'm not sure myself what its called, 'keyed mitre' sounds good though. It was easy to do: after cutting the 45 degree mitres on the boards I just cut the shallow 45 degree slot, one blade width wide. Not too critical for it to be centered on that 45 degree face, just looks better that way (used a radial arm saw; table saw should work well too) . The 'keys' are just small chunks of wood, less then cm long, cut to fit the groove. I placed three keys per groove. You want to make sure the grain of the keys runs across the joint, not along the joint, much stronger that way. Then test-fit and glue it all up, light clamping, making sure its all squared up.
I used the regulator schematic on page 361 of the Morgan Jones book. That circuit shows a 1k and a 22k in parallel (about 950 R) between Out and Adjust, to give 300 volts. I used just the 1k resistor and get something like 285-290 v when the amp is operating, I forget what the exact voltage was. The amp has been working very well for several months, sounds great. Good luck
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