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GB for Leach Low-TIM with 8 + 8 BJT outputs (bare PCB)
GB for Leach Low-TIM with 8 + 8 BJT outputs (bare PCB)
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Old 24th February 2014, 07:06 AM   #21
Ranchu32 is offline Ranchu32  Australia
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Thanks Linux, Andrew, good to know I could use this board with fewer outputs, but I was rather hoping there'd be interest in a smaller board purpose-built for lower power.

What do you need 8 outputs for anyway? :-D
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Old 25th February 2014, 02:51 AM   #22
Barrettn is offline Barrettn  United States
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Default Differences between original Leach and Jens design?

Years ago I started a 5.1 channel Leach amp, intending to use it for home theater. Now years later I still have all the parts, but the PCBs were etched by my brother using a process he had access to at work -basically you fed it photo-negative artwork and PCBs came out the other end. Problem is, it looks like the plating wasn't very thick, even just being stored they have some pitting in the traces.

So I'm thinking it'd be REALLY smart of my to jump into this group buy for the PCBs, but I'm worried I don't have time to figure out all the differences between the original Leach design and the redesign Jens has done.

Can someone summarize the differences, or if it's documented somewhere, point me to where? (there's 100+ pages of threads to wade through looking for it!)

I'd planned on using a 84VCT 1kVa torroid to power it all - ~59VDC.

Thanks in advance for any replies!

Barrett
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Old 25th February 2014, 07:43 AM   #23
linuxguru is offline linuxguru  India
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Quote:
Originally Posted by Barrettn View Post
Can someone summarize the differences, or if it's documented somewhere, point me to where? (there's 100+ pages of threads to wade through looking for it!)

I'd planned on using a 84VCT 1kVa torroid to power it all - ~59VDC.
The schematic I'm following for this layout is Version 1.05.12 by Jens - posted for reference here:

http://www.diyaudio.com/forums/group...ml#post3827845

Briefly, the main changes that Jens made were in the number of O/P devices (6 + 6) updated for modern flatpack devices; changed output current-limiting circuit (senses currents from all output pairs and sums them, and some other changes); on-board large filter/bypass caps in addition to the main off-board PSU filter reservoir.

I added 2 additional pairs and beefier drivers to Jens' last schematic, but kept everything else more or less the same. I moved the clamp diodes and the Zobel network in-board of the output inductor. I also separated the small signal section (LTP + VAS) from the rest of the circuit and added ground shields and optimized placement of the signal ground and power ground traces. Some passives are changed to allow physically larger components. Some other minor changes - I'll get everything into a fresh schematic or a release note later and post it here.
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Old 25th February 2014, 11:40 PM   #24
Barrettn is offline Barrettn  United States
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Quote:
Originally Posted by linuxguru View Post
The schematic I'm following for this layout is Version 1.05.12 by Jens - posted for reference here:

http://www.diyaudio.com/forums/group...ml#post3827845

Briefly, the main changes that Jens made were in the number of O/P devices (6 + 6) updated for modern flatpack devices; changed output current-limiting circuit (senses currents from all output pairs and sums them, and some other changes); on-board large filter/bypass caps in addition to the main off-board PSU filter reservoir.

I added 2 additional pairs and beefier drivers to Jens' last schematic, but kept everything else more or less the same. I moved the clamp diodes and the Zobel network in-board of the output inductor. I also separated the small signal section (LTP + VAS) from the rest of the circuit and added ground shields and optimized placement of the signal ground and power ground traces. Some passives are changed to allow physically larger components. Some other minor changes - I'll get everything into a fresh schematic or a release note later and post it here.

Thanks, exactly what I needed to know. Given the smaller size of the original design and the fact that I already have all the parts and heatsinks for it, I'm hurriedly trying to see if I can track down any of the original boards, but if I don't find any in the next two days I will have to put my name on your list and get the newer parts.
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Old 26th February 2014, 09:40 AM   #25
linuxguru is offline linuxguru  India
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The first 5 lots (all the lots for which payment has been received) were shipped today. The next batch will probably be of the order of 20-30 boards - I'll probably freeze on the exact number by Friday.
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Old 26th February 2014, 10:20 PM   #26
John Luckins is offline John Luckins  Europe
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Hi there,

Always wanted to build one of these amps. Can I pitch in for 4 boards to the UK please.

Thanks

John
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Old 27th February 2014, 06:22 AM   #27
linuxguru is offline linuxguru  India
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OK, here's the list or requests (for the 2nd batch);

Tarasque - 8
Earthquake - 8
John Luckins - 4

(The count has reached 20 with a day to go, with several more expressions of interest and some unfilled requests from the 1st batch. I'll probably go with an order of 30..32 boards for the 2nd batch tomorrow or Monday - it's just possible that it will reach 40, let's see how it goes).
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Old 27th February 2014, 06:58 AM   #28
linvalb is offline linvalb  Jamaica
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Default Leach 8+8

I sent Paypal payment for 2 boards a few days ago, just wantted to know if it was received?.

Thanks.
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Old 27th February 2014, 07:07 AM   #29
linuxguru is offline linuxguru  India
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Quote:
Originally Posted by linvalb View Post
I sent Paypal payment for 2 boards a few days ago, just wantted to know if it was received?.
Yup, sorry if I missed replying to the PayPal notification of your remittance. Your boards were shipped yesterday (to the Canadian address from the PayPal notification - I hope that's OK?).
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Old 11th March 2014, 06:43 AM   #30
rao gurappa is offline rao gurappa  India
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two more pcb's for me
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