Leach Super Amp Pcb Re-Design (LSAPRD)

[spookydd]

I for one would like the 10 output version.

Board thickness 2,4mm with Cu 70um ?

If price is right I'd be in for 10 boards.

Got a quote locally (small quantity) between 60 and 80 euro depending on thickness, ouch!

I was hoping for the 12 output version, but if the 10 is what the group buy goes for, then I'm in also for 10 boards.

 

[Briek]

Maybe not 100% wright place to ask my question.

I am building a leach amp with 3 pair output transistors. I am using MPSA06/56, 2N3439/5416, MJE15031/15032 and MJL1302/3281 transistors.

Is the value of the miller capacitors important or not very? Which values should i use?

As soon as my first channel is build I post some pictures of it.

 

[noSleep]

To those who built the LSAPRD

Please tell,
what do you think of the sound, did it work out as you expected ?

 

[linuxguru]

Link to GB for bare PCB of 8 + 8 BJT Leach Low-TIM (not Super Amp):

http://www.diyaudio.com/forums/grou...tim-8-8-bjt-outputs-bare-pcb.html#post3822518

 

[shimness]

Does anyone here have the files that were on the Delta-Audio site? I would like the files for both versions of the PCB that Jens did as well as the great PDF he did comparing the various transistor options. I have sent him a couple of PMs with no replies as of yet.

Any help would be appreciated. I would like to build a 5 channel amp using the design he did as a starting point. Going to be something like a Bryston 9B if all goes well!

Thanks

 

[TonyTecson]

Hi, fire me an email and i will send them to you....

 

[mot on/off]

Hello,

I would like to ask for some help about thermal conductive insulators for TO-264 type output transistors for the 10-version by Jens.

As i'm finishing an old project and gathering components etc now i'm searching what to do about insulators for the MJL4302 - MJL4281.

I have the Conrad heatsinks (very nice) from Australia.
Made some M3 threaded holes, but i find it difficult to find the right insulator..

I can find in ebay some TO-247 silpads from Bergquist or 3M (but not for TO-264) but i don't know which of them to use...

Any suggestion?

Thanks a lot!!

 

[TonyTecson]

you may also want to try kapton tapes...

 

[BrianDonegan]

I have done sheets of Bergquist K-10 that I cut up as needed. It works very well.

 

[mot on/off]

Hello!

Thanks for reply!

I'm thinking also about Kapton tape but i don't know how to use them.. Only Kapton tape? First layer of Kapton tape and then some insulator + thermal grease ?

I'm thinking for a piece of sheet that i can use of Bergquist brand but there are several numbers of thickness and thermal conductivity..

@ BrianDonegan : Bergquist K10 can find at ebay but not as sheet only fixed patterns (excluding TO 264). Where can i buy them as sheet ??

Thanks a lot!!

 

[nattawa]

Digikey sells K-10 sheet 11.5" x 12" in size at deterring $83.73.

I use kapton tape as power transistor insulator, I've seen member still4given uses it in his amps. I'm sure we are not alone.

I bought 30mm width tape on ebay. It came with silicone adhesive that's about the thickness of the kapton base material itself. The adhesive does everything but helping heat transfer. It's best to remove it whenever possible, IMO.

Here is how I get rid of the adhesive: (this has to be done outdoor or in a well ventilated indoor area, wearing rubber gloves) lay a length of the tape on a piece of glass, adhesive side up, apply turpentine or mineral spirit with a small piece of rag. Let sit and re-apply, repeat a few times. After a few minutes, the adhesive is softened by the solvent. With a plastic straight edge, an old credit card for example, scrape the adhesive off the tape until the tape is clean.

At installation, make a 3mm hole with a hole punch on the tape for the mounting screw, I use spring clips on transistors so I rarely need a hole on the tape. Apply a very, very THIN layer of thermal grease on the mounting surface of both the transistors and the heatsink. This tape is as thin as the thinnest mica you can get, yet much more easily handled, sourced, and for little cost.

I believe such an installation beats K-10 hands down in performance, as K-10 has the same material (polyimide) in the middle as its "bone" and silicone on both sides, totaling 0.15mm thick before installation, while in our "wet" kapton tape installation, the thermal interface thickness is 0.025mm on the polyimide tape and barely anything else.

 

[mot on/off]

Hello,

Thanks for your reply!

Kapton tape + thermal grease is enough as you say..
I just worred about the strength of Kapton tapes regarding very small thickness.. I thought it was better to use something like 0.1~0.5 mm for better voltage insulation also for use gap filler.

Kapton tapes are cheap at ebay and as i see everything else - sil pads etc are much more expensive.

Thanks

 

[nattawa]

Kapton films have dielectric strength of at least AC rms 100KV/mm. With 25 micro meter thickness you're getting at least 2.5KVrms. You will be surprised by the mechanical strength and toughness this material possesses too. I was.

 

[mot on/off]