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GB for Leach Low-TIM with 8 + 8 BJT outputs (bare PCB)

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L

linuxguru

Member
Joined 2007
Ian, thanks for the update.

At this point, all boards that have already been paid for, have been shipped. I'm holding a few boards that were requested earlier (but unpaid), plus an additional 14 uncommitted boards. Anybody who is interested in the uncommitted boards may PM me or email me at siva dot chander at gmail dot com. The prices are as before: USD 18 each + USD 8 s&h for up to 4 boards + PayPal fees of USD 0.50 / board.
 
L

linuxguru

Member
Joined 2007
Thanks for the update and feedback - the screen-printing is at about the limit of the vendor's capability, and anything finer will result in missing or partially printed characters. If you have queries about any specific locations where the parts designation or the value is ambiguous, I'll try to clear it.
 
L

linuxguru

Member
Joined 2007
scalpel said:
Hello Siva. The little round dot at each position of the driver transistors.Does this indicate the position of the emitter.
Click to expand...

Yup, the little round dot on Q11 (2sd669a or equivalent NPN) and Q20 (2sb649a or equivalent PNP) indicates the position of the emitter. Note that these are pre-drivers (1st stage of the 3-stage emitter follower). The drivers are Q9 and Q21 (2nd stage).

Edit: There may be a heat-sink mounting issue on one or both of Q11/Q20, in that the metal tab of the TO126 devices may not face the heatsink. If you're using fully-isolated versions of Q11/Q20, that won't matter, though.
 
Last edited:
L

linuxguru

Member
Joined 2007
scalpel said:
jumpers j1 and j3 are to go to power ground?
Click to expand...

J1 to J3 are Faston male connectors (to which off-board connections are made). J1 and J2 go to the PSU/rectifier/filter board and speaker return, respectively. J3 is the output and goes to the other terminal of the speaker. There are also two more marked +Vcc and -Vcc, which go to the PSU board.

Also note TT1 and TT2, which are meant for a thermal tracking chain of 3 or 4 series-connected diodes, to be mounted on the heat-sink.

Another unmarked jumper should be wired from the Boucherot node (i.e. junction of R86, R87 with R88) and the right-side of R39 (12k feedback resistor). This jumper is in the main feedback path. The pads already exist, but the labeling on the silkscreen was omitted by accident. You can use a section of thin insulated wire either on the component or solder side for this jumper.
 
Roushon

Roushon

Member
Joined 2004
linuxguru said:
Folks, as the title says: This is a preliminary GB for a Leach Low-TIM clone based on Jens Rasmussen's last published schematic, with 2 additional output pairs for better SOAR management (and a few other minor modifications). Almost all the parts designations have been retained the same as the Jens Rasmussen BOM. With 8 + 8 2STC5200/A1943 outputs and +/- 75V rails, this should comfortably manage about 300W into 8 ohms. Higher rails are possible with appropriate transistor substitutions. Each of these boards is a monoblock of dimensions 265mm x 95mm (see attached picture).

At the moment, I have 16 boards available, but depending on the interest, I can order additional boards (for further rounds of the GB) with about 2 weeks lead time.

The bare boards are priced at USD 18 each, and I can ship up to 4 boards to most locations in the US/EU/Australasia for a flat rate of USD 8.

If interested, please add the quantity required to the thread, and PM me your email address. PM or email me (siva dot chander at gmail dot com) for questions, clarifications, details, etc.
Click to expand...

Hi!
May be I am too late as this is a very old thread.
Nevertheless giving a try. I have Kings open baffle
speakers which I am playing with LM3886 based amp so
far. Would like to try some non-chip amplifier, 200W per
ch. Searching the forum takes me to Leach amp and then
to this page. I know nothing about this amp. Will it be a
suitable project for my requirement based on this Leach
amp? If yes, kindly tell me whether you still have a couple
of boards left with you.

Regards
Roushon.
 
L

linuxguru

Member
Joined 2007
Roushon said:
Hi!
May be I am too late as this is a very old thread.
Nevertheless giving a try. I have Kings open baffle
speakers which I am playing with LM3886 based amp so
far. Would like to try some non-chip amplifier, 200W per
ch. Searching the forum takes me to Leach amp and then
to this page. I know nothing about this amp. Will it be a
suitable project for my requirement based on this Leach
amp? If yes, kindly tell me whether you still have a couple
of boards left with you.
Click to expand...

Hi Roushon - yes, I have some boards still available. They can be populated with 4 pairs of outputs (4 NPN + 4 PNP) to reach 200W into 8 ohms with (say) +/- 60V rails. PM me or email me at siva dot chander at gmail dot com for details.
 
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