Hallcon83,
At this time the particular boards you describe are not available. The board layout is undergoing beta tests for any problems. We do not expect any just a good idea before producing a large quantity.
This second round group buy, for which I have 4 boards left, was for the Jens Rasmussen layout of the original Leach Tim amplifier with 10 output devices. This amp is just one long board with the outputs soldered to the board. It is a particularly good design and can be configured for several voltages producing upwards of 200 watts.
If you are still interested in this layout post here and I will email you back. The boards were sold for 17,00 dollars U.S. each plus shipping and paypal fees.
Tad
At this time the particular boards you describe are not available. The board layout is undergoing beta tests for any problems. We do not expect any just a good idea before producing a large quantity.
This second round group buy, for which I have 4 boards left, was for the Jens Rasmussen layout of the original Leach Tim amplifier with 10 output devices. This amp is just one long board with the outputs soldered to the board. It is a particularly good design and can be configured for several voltages producing upwards of 200 watts.
If you are still interested in this layout post here and I will email you back. The boards were sold for 17,00 dollars U.S. each plus shipping and paypal fees.
Tad
Yes, I've purchased these before from Michael Percy Audio, primarily for loudspeaker crossover use..
Which one?
The 5W Mills(MRA-5,$2ea) is SO TINY, compared to the silkscreen layout, I wondered if it's a good choice for the emitter resistors...
The 12W Mills(MRA-12, $3.50ea) is just too big to fit the space allotted.
Is there another resistor, comparable to the Mills, that might be the right size/rating?
While I'm curious if the Fukushima MPC74's on eBay are fake, they're surprisingly close in cost to the MPC71's available from Europe (US$0.85, vs US$0.75); however the delivered costs from Europe may be high (tho' I hear these are the finest emitter R's).
http://www.schuro.de/preisl-mpc71.htm
An opportunity for another group buy? -Chas
clm811 said:
I think that on a site schuro.de sells resistors manufactured Robert G. Allen Co.
http://www.ibselectronics.com/ibs/cmpnts/rgaco/catalog/K/K37.pdf
Chas,
Short version: the "little" resistors are fine.
Long version:
Modern materials allow higher dissipation in smaller packages. The power rating is based on continuous average conditions.
Actual dissipation in emitter resistors is quite low. Working backwards, with a 0R47 resistor:
We'll use the rule of thumb that you want to keep dissipation under 1/2 rated dissipation.
For 2.5 W you'd need current under 2.3A. That means your RMS current output for the amp would be limited to 11.5A. That's not peak, which would have to be MUCH higher with music to reach that average.
11.5A into 8R is 1058W and 528W into 4R. Five pairs of MJL4281/4302 wouldn't last long in that environment.
Even 100W RMS into 4R means only 1A per emitter resistor, or .47W.
Short version: the "little" resistors are fine.
Long version:
Modern materials allow higher dissipation in smaller packages. The power rating is based on continuous average conditions.
Actual dissipation in emitter resistors is quite low. Working backwards, with a 0R47 resistor:
We'll use the rule of thumb that you want to keep dissipation under 1/2 rated dissipation.
For 2.5 W you'd need current under 2.3A. That means your RMS current output for the amp would be limited to 11.5A. That's not peak, which would have to be MUCH higher with music to reach that average.
11.5A into 8R is 1058W and 528W into 4R. Five pairs of MJL4281/4302 wouldn't last long in that environment.
Even 100W RMS into 4R means only 1A per emitter resistor, or .47W.
Got some Trannies!
Thanks, pchw!!
Guys, I must say that the only thing better than corresponding with everyone on this forum is meeting you in person.
I've met Pchw and Brutepuppy, spoken with Wjh, and they're all really nice guys!
A few more of us in the SF bay area and we could form a local club...
I look forward to getting together with them for a parts G.B. and, once we have all our parts, for a board-stuffing party!
-chas
Thanks, pchw!!
Guys, I must say that the only thing better than corresponding with everyone on this forum is meeting you in person.
I've met Pchw and Brutepuppy, spoken with Wjh, and they're all really nice guys!
A few more of us in the SF bay area and we could form a local club...
I look forward to getting together with them for a parts G.B. and, once we have all our parts, for a board-stuffing party!
-chas
Regulating front end
Yes, guys. I, too, have been wondering about regulating the front end.
In fact, I found a pair of Boak regulator PCB's in my"box o'stuff"
recently.
These were popular for regulating various SS amps back
in the early 1980's when I was a student
(For details, see back issues of The Audio Amateur 01/1980).
Would these be useful, or are they too out-dated?
TIA
-Chas
Yes, guys. I, too, have been wondering about regulating the front end.
In fact, I found a pair of Boak regulator PCB's in my"box o'stuff"
recently.
These were popular for regulating various SS amps back
in the early 1980's when I was a student
(For details, see back issues of The Audio Amateur 01/1980).
Would these be useful, or are they too out-dated?
TIA
-Chas
Just a fyi, barredboss has on ebay 12"x8.5" heatsinks available. He was mentioned earlier in this thread as a possible source. In addition he states he will discount large orders. The only bad thing with these heatsinks, the fins run horizontal. Is there any interest in a group buy on this?
ps I have no relationship with the seller, just someone looking to save some money.
ps I have no relationship with the seller, just someone looking to save some money.
bulldawg81 said:
You volunteering Bulldawg?
heat sinks here http://cgi.ebay.com/HEATSINK-ALUMIN...14&_trkparms=72:1205|66:2|65:12|39:1|240:1318
Stand them on end 3 in a row and it makes for a nicely proportioned 6 channel amp or cut them down to 9.5-10" and you can mount two channels perpendicular to the fins and make a 17" deep 10" high 4 channel amp.
I would be interested in 6+ if we get enough interest, although I suspect the price break may not be enough to warrant a GB effort.