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Leach Amp pcb group buy interest

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#322
Any boards left?

Hi,
I have probably completely missed the boat but the most recent posts for this are fairly new so I thought I would give it a chance!
I am wondering if there are any boards left?
I am considering building a pair of Leach amplifiers.
Thanks and regards,
Joe

PS First ever post in any forum anywhere on the web (apart from in the introductions thread!)
 
#325
tryonziess said:
Luke,
The Sanyo transistors 2sa1371/2sc3468 which I have ordered are about 40 cents apiece from MCM electronics. If you look up the specs on these and you are interested I will be more than happy to ship them to you. The 2sc is back ordered until the middle of May, but still will be available.
Let me know and I will place an order for them. The 1/16 heatshrink is 1.69 for 4 feet. I do not know what that is in metric.
If anyone can find a high voltage transitor for the TO-92 position with the excellent specs and FOOTPRINT that would be nice.
I am going to keep the mje340/350 and drivers per the BOM. They have specs well within reason and I have some on hand.

Ed lafontaine,
I did not receive any money in my paypal account with your name on it that is why the boards were not shipped. I plan to send out a set once all of the international and domestic units have arrived. I have four boards and will part with 2 of them to fill your order. If the funds do not show up at paypal I have to assume that those persons dropped out. I also had a hard time placing legitimate names to the names we use here at DIY audio. It can be difficult.

I also have 10 of the Leach 10 transitor boards left over if anyone is interested email me.

Tad
Click to expand...

Hi Tad,

I would like 6 boards. would you still have these?

Regards...Marcel.
 
#327
Leach 10 transistor boards

I do not have any of the Leach 12 transistor boards designed by Jens Rasmussen.
I DO Have 10 of the Leach 10 transitor boards layed out by Jens. Information concerning the 10 output board can be found at the beginning of this thread. If you go to Google archive and research Delta-Audio all you need to know about the 10 output board can be found there. As AndrewT so eloquently stated earlier this is a clone of the Leach TIM amplifier designed by Dr. Marshall Leach professor at Georgia Tech.
If you are interested send me an email.I only have 10 left over from the first group buy. Why I ever though I needed ten of them I do not know. These are .093 FR4 fiberglass with 2 oz copper tracks. Very nice quality pcb's.

Question: Will changing the feedback resistor values on the Leach 12 amp make any sonic difference like on the Pass A-75?

Tad
 
#330
AndrewT said:
1uF MKS/MKT are available in 5mm pin pitch.
I hear that one manufacturer makes an MKP in this size. It will be much bulkier than MKS/MKT. Check footprints of all before ordering.

The round fuses are available, but I could not find the fuse holders in the UK.
I soldered these fuses direct to the PCB. Be careful, particularly with start up currents, they are difficult to remove (PTH and heavy copper trace thickness and thick PCB all increase the skill required to remove these without damaging the PCB).
Click to expand...

Andrew thanks for your reply, what mkp and fuses did you use?
I just checked mouser, digikey and farnells dont have an mkp with 5mm pitch spacing, BTW what voltage should these be?
 
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#331
tryonziess said:
Luke,
The Sanyo transistors 2sa1371/2sc3468 which I have ordered are about 40 cents apiece from MCM electronics. If you look up the specs on these and you are interested I will be more than happy to ship them to you. The 2sc is back ordered until the middle of May, but still will be available.
Let me know and I will place an order for them. The 1/16 heatshrink is 1.69 for 4 feet. I do not know what that is in metric.
If anyone can find a high voltage transitor for the TO-92 position with the excellent specs and FOOTPRINT that would be nice.
I am going to keep the mje340/350 and drivers per the BOM. They have specs well within reason and I have some on hand.

Ed lafontaine,
I did not receive any money in my paypal account with your name on it that is why the boards were not shipped. I plan to send out a set once all of the international and domestic units have arrived. I have four boards and will part with 2 of them to fill your order. If the funds do not show up at paypal I have to assume that those persons dropped out. I also had a hard time placing legitimate names to the names we use here at DIY audio. It can be difficult.

I also have 10 of the Leach 10 transitor boards left over if anyone is interested email me.

Tad
Click to expand...

thanks Tad, thats very kind of you. I will keep that in mind when I get into ordering mode🙂
 
#332
Luke said:
I just checked mouser, digikey and farnells dont have an mkp with 5mm pitch spacing, BTW what voltage should these be?
Click to expand...
I had many components in stock for the 3pair PCB. Most of the caps were the wrong pitch.
It was an enormous job finding the fewest suppliers that could supply all the missing cap values to fit this PCB.
I never did find a 5mm 1uF PP, I used PES.

Most of the caps can be 50V or 63V, check the BOM.

The three pin input arrangement provides a choice of AC input or DC input or Shorted input for testing. It's a brilliant layout that covers so many bases, in a tiny space.
 
#334
What resistors to use?

from post 300, tryonziess asks:
To All: We need to get together and come up with some suitable -- affordable -- output resistors. Many that are affordable are not non-inductive or is that a big deal. Any suggestions?
Click to expand...
I find this:

http://www.diyaudio.com/forums/parts/96593-what-resistors-use.html

I measure the inductance of a YAGEO 5W, 0R51 sand cast resistor to be ~0.015 mH.
I measure the same on a "OMCCHINA, TW" 5W, 0R47 sand cast to be ~0.014 mH. This latter has been sold by Tech Diy, The Company Store, as suitable for use as an emitter resistor.

So, my assumption is that these will be fine.

Whadya' think?

Also, AndrewT, Would you care to share the "R" value you are going to use for Re in your build?...and its supporting cast of players? 😉

Thanks
 
#337
AndrewT,

Thanks for the response...and insight into your choices & the way you accomplish them...I'll be interested in the finer point choices you make as you go...

That will be me back there clinging to your shirt tail... 😉

I'll be using 110 vct transformers, one per channel. They are the same as were in the Sansui G-9000 DB
 
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#340
Ed LaFontaine said:
I find this:

http://www.diyaudio.com/forums/parts/96593-what-resistors-use.html

I measure the inductance of a YAGEO 5W, 0R51 sand cast resistor to be ~0.015 mH.
I measure the same on a "OMCCHINA, TW" 5W, 0R47 sand cast to be ~0.014 mH. This latter has been sold by Tech Diy, The Company Store, as suitable for use as an emitter resistor.

So, my assumption is that these will be fine.

Whadya' think?

Also, AndrewT, Would you care to share the "R" value you are going to use for Re in your build?...and its supporting cast of players? 😉

Thanks
Click to expand...

Im not sure to be honest, but I calculate your reactance to be 1.89 Ohm at 20Khz for 15uH, wouldn't that have an effect on a 1 ohm resistor?
 
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