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Leach Amp pcb group buy interest

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#225
Tad,
Too bad my hd crashed so all pspice layout files were lost.
Only happened to order samples (4+1 promo) from advanced which luckily, with sir Tony's assistance didn't had problem. Just eliminated the small pcb where 4 diode strings are mounted. I had to mount them in the middle of MF151x350 heatsinks directly due to thermal problems when playing at high volumes. With my 2 diy TH115 clone (definimax4015LF) so far, I have been contented with my high power craving. I used MJL21193/4 outputs. I think super leach GB will push through in the near future.
regards,
Roland
 
#226
Roland,
Advanced should still have your files in the re-order area. They are always hoping for reorders.

In the new Leach 12 BOM Jens has the bc556 transistors spec'ed. I can only find these in 60 volts. Is there a higher voltage offered for this transistor or can it be substitured with an mpsa 92 or similar.

Tad
 
#229
Andrew,
Most of the 2sa and 2bc transistors only have at most 120 volt specifications. Though the frontend is only going to be 95-100 volts there is not much wiggle room here. Going to a TO-220 footprint offers more but, the board is layed out TO-92.
Sanyo has some great TO-220 for the drivers with exceptional spec's.

Anyone have some exotic substitutes which I can not dig up.
The parts count for this amp is not lean by any means. More fun sourcing parts and making UPS richer.

Tad
 
#231
tryonziess said:
Roland,
Advanced should still have your files in the re-order area. They are always hoping for reorders.

In the new Leach 12 BOM Jens has the bc556 transistors spec'ed. I can only find these in 60 volts. Is there a higher voltage offered for this transistor or can it be substitured with an mpsa 92 or similar.

Tad
Click to expand...

yeah, perhaps we can organize it in such a way that Roland orders and someone in the states handle the payments and deliveries...sounds like a plan.....

the MPSA92/42 can be used for higher voltages, but it looks like Roland has no issues using the BCxxx....
 
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#232
rolandong said:
Tad,
Too bad my hd crashed so all pspice layout files were lost.
Only happened to order samples (4+1 promo) from advanced which luckily, with sir Tony's assistance didn't had problem. Just eliminated the small pcb where 4 diode strings are mounted. I had to mount them in the middle of MF151x350 heatsinks directly due to thermal problems when playing at high volumes. With my 2 diy TH115 clone (definimax4015LF) so far, I have been contented with my high power craving. I used MJL21193/4 outputs. I think super leach GB will push through in the near future.
regards,
Roland
Click to expand...

Roland,

can you find out from Advanced, how much an order for 100pcs would cost? maybe we can generate enough interest.....thanks..
i will go for 10 boards if ever this pushes thru....
 
#234
O.K. Andrew,
I will try the 2sc TO-92 transistors. They have good spec's I was just concerned about there use with 100 volt rails.
Now do you also recommend the high gain device as the main driver for the outputs. There are some very good Sanyo and Toshiba items for use here.

Anyone know a good source for Rifa/Evox polypropylene film caps in the U.S.?
Evox was always abundant in my old Mcintosh equipment and it lasted for decades.

Tad
 
#236
tryonziess said:
O.K. Andrew,
I will try the 2sc TO-92 transistors. They have good spec's I was just concerned about there use with 100 volt rails.
Now do you also recommend the high gain device as the main driver for the outputs. There are some very good Sanyo and Toshiba items for use here.

Anyone know a good source for Rifa/Evox polypropylene film caps in the U.S.?
Evox was always abundant in my old Mcintosh equipment and it lasted for decades.

Tad
Click to expand...

hey tad, japanese to-92's are not drop-in replacements, their collector leads are almost always in the middle, unlike the bc's or mpsa's where base lead is in the middle.....

regarding caps, luvdunhill did a group buy for vishay polys a few months back, here......http://www.diyaudio.com/forums/grou...ay-roederstein-mkp1837-bypass-capacitors.html
 
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#238
Ive got schematic Leach ver 1.00.12.pdf and the part numbers do not match the BOM. For example, T3 to T8 in the BOM are MJL3281, but in the diagram they these transistors are for the front end.
So whats the safest rail limit for I can use for BC546 and BC556 in this amp?
 
#240
AndrewT,
Sounds like the responses I used to get from by professors at school. Figure it out yourself.
O.K. We calculate the load the transistor sees when it drives the resistor. Just how much extra room in percentage is a safe margin?
Will the higher gain from the BC or SA components actually be noticeable in the final product?

Tad
 
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