digger945
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Posts posted by digger945
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Who wouldn't LOVE those cans. Absolutely fantastic.
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Just noticed that all 2 ohms were connected to the source pins on both of Kevin's pcb's, and it would match all schematics if you look at the symbol for the J76 and turn it upside down.
I'm now working witha build using LED3 reversed as it is on all of Kevin's pcb's and I have the output of the 2nd stage down to +/- 15V which looks high. I will connect the servo tomorrow and see what happens.
Enjoy the rest.
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If anyone else has built this I would like to compare some numbers.
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Pinout on the J76. 2 & 3 reversed?
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Are you sure those small caps are 5mm lead spacing, I measure 3mm.
7.5mm on the 6 big polars.
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I think so, being the same part as CMF55 they should be good to 1/4 watt within specs.
I just put a RN55D in the calipers and I get .246" length on the body.
This might work for the 5 ohm.
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I think it's safe to say C9 and C10 can be .1uF 50V with small lead spacing, say .1"/2.54mm. They will need to be populated regardless of opamp choice, with or without regulators. .1uF is used in some of the example circuits for the 445 at ti.com and was the value for the servo on the Dynahi.
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Is that $43 per device, or $43 for a stereo differential front end? Cuz if you could even find the 109/389, you would be paying at least that much for 2 pairs of them...
I would like to know also. Worth the money if they sound good.
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Yeah I think j4cbo is already done populating most of 8 boards (No diodes/heatsinks/fets yet)...
Prototypes on pcb's?
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LED3.
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No, you won't need these to use a balanced source with SE amp/headphones.
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If the lead spacing for the 15V regs is the same as the Dynahi board a TO-92 part should fit nicely with no problems, but why if a TO-92 part is all that will be needed.
I agree it would be nice to have lead spacing for standard box films, where those may be appropriate. Are you thinking just one spacing or a dual spacing?
Great looking board.
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I think I'll take your word for it.
It does make building and installing the two halves of the amp simpler once everything is bolted up, for me anyways using the parmetal case.
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I also thought about that for some time. The only consideration in my mind was that it was yet another physical bond that the heat would have to cross and, like with the angle, it would be hot on one side and cooler on the other and maybe cause it to bow and lose complete contact with the large HS.
My thinking may be off here, I'm not an engineer, just thought that maybe bolting directly to the HS might avoid alot of fuss. I have since purchased a drill press slide to make the holes in a nice neat row.
On the pic above I hand lapped each angle on a piece of plate glass with 440 grit until I mated the two parts with a bit of oil and they took a fair amount of force to seperate.
It probably isn't common to see the words "hurry up" and "dynamite" in the same sentence, but I had to decide on a method of attachment and really wanted to get this finished so we can compare it to a B22 at the upcoming meet. I really think it will kick some beta arse.
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yes, they will be compatible with the Dynahi boards. Thanks for the offer
Doesn't matter to me. If I were doin it again I would cut the pcb off next to the output pads(so the pcb can be moved closer to the HS) and mount the output's directly to the heatsink, as I plan to do for this build.
The angle thing just seems kinda cheesy to me, although it doesn't look too bad.
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I don't see how KG could build a working proto and comment on the sound the way he did if there was a problem with the parts selection. However I have purchased pcb's that later had to be modded because of a very minor oversight by the designer.
I am also willing to pitch in if needed just to have one or a pair of the final pcb tested just to make sure. Have you guys agreed on the final position of the ouput devices yet?(I am still trying to catch up on reading)
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Maybe we could agree to at least see if we could get at least 2 boards into someone's hands to do a test build and see if this thing is going to make music before any more $ is spent. I thought I read KG say that he had build a prototype somewhere.
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I agree. 2 sigma22's can more than handle the power needed for this amp, the determining factor will be heatsinking. 1A per sigma(at 30V) is the limit with stock 1.5" aavids, and I don't think going with 2" aavids(the largest alternative I could find that will fit the pcb without alot of work) will improve much. A better alternative would be Conrad MF20-1F or angle aluminum to your choice of larger HS. Probably not that big of a deal with just headphone duty but like you say, no-one knows for sure what the power requirements will be for a fet board.
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By larger do you mean 2" instead of 1.5" Aavid thermalloys that are stock with sigma22 glassjar kits?
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If a much lower gain is possible with the fet(lower than the dynahi), I would be interested in switching capability to use one of the four boards as active ground for a 3 channel SE output. It probably won't get used much but would be great from a resale standpoint.
I need to do some more reading to comment further.
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Ugliest cat I ever seen. Looks like he already used up 8 lives.
a nod to someone who has served us well
in Do It Yourself
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The copper color hardware is perfect.
You are THE can man.