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Leach Amp pcb group buy interest

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#564
Ed LaFontaine said:
Luke, I have 110 vct, so the rails will be ~75V.

The 2 transformers also have 84 vct, 42 vac & 8 vac.

They are from scrapped Sansui G-9000DB's.
Click to expand...

Hi Ed,

did a bit of a google, those amps looks nice.
They were good for about 160Watts rms into 8 or 4 ohms or 320W for 2 channels. With these rails your amp can potentially deliver around 450 watts rms into 8 ohms, so your Transformer is probably a limitation here. No big deal but keep it in mind.
If your transformer has 2 X 8V AC then you could use these in series with your 55V AC to give your voltage for frontend, ie 55 + 8 gives 63 V, but you will need two 8 V taps obviously.
 
#565
tryonziess said:
kind of like the states before
Click to expand...

Shocks, the world is turning upside down. :clown:

Glen hangs out at Andy-C's forum nowadays, maybe he'll post there if he continues the project.
Something resembling the SE-A1 was posted overhere, to get an idea.
Class A+ is a combination of of a high bias, low rail voltage Class A stage, and a tracking Class AB amp that drives the ground side of the rail capacitor banks.
Rail voltage is raised with increasing output (raised input voltage level), is Class A operation with a much lower dissipation level.
The same principle could be used to keep rails voltage upright on a Class AB amp.
 
#567
Ed,
Antek has some nice trannys in toroid that will get the voltage you need and you may save quite a few dollars. The 100va 32-0-32 item will get you about 90 volts on the rails and 2 of them are only 18.00 each. Antek ships by U.S postage - if memory is correct -- which also saves money.

Will a 50va tranny have enough current to drive the frontend. It specs at 1.6 anps.

Just a thought. Tad
 
#569
AndrewT,
Thanks for the info.
You still seem to think I have these formulas stenciled to my brain. Where am I to find the load on the frontend and its capablity.
Steer me to this knowledge and I can learn it. I have know idea what the particular specifications on a transistor translate to or for that matter how to plug them into an equation. I am a diagnostic technician by trade not an EE. I solve combustion related issues all day long. The audio thing is my hobby and I enjoy it when I have time. From where I started in this endeavor I think I have come a long way.

Tad
 
#570
have you downloaded the Leach paper on the LO TIM design and build.
It is all in there. You just change some values for different supply voltages.

PS.
I am not an EE either. I'm certainly not a Technician with diagnostic tools tucked into every orifice.
I am a Civil Engineer with no training in Electronics, neither analogue nor digital.

Yes, it's a hobby.
Do you do things yourself and expose yourself to the associated risks, or get someone else to do that for you. You have to decide which you like best, listening to the music or living.
 
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#571
AndrewT,
What I do this for is the shear satisfaction that I did it -- with the help of some experts -- and it worked. At my age I have no one to brag to or make envious. I just want to achieve something that I have not done before and be successful. Analog electronics had always eluded me throughout my life because of nonexposure. I chose to change that and here I am.
Thanks to this great website and its members I am able to construct something useful and gain more than just music. By providing these few modest group buys I try to give something in return. And as alway I thank you for sharing your wealth of knowledge though taxing, at times, it may be.

Tad
 
#574
Ok, an attempt to sumarize:

R4 = R7 = (Vrail - 40)/8.2

Along with that the active devices and caps need to be chosen to (at least) have adequate V & I carrying capacity. Other flavor of the month issues notwithstanding...don't want to get into osculation. 😀

I was afraid it would be more complicated than that...flamesuit going on now...

A "target" range for the front end transformer (75V rails) is 64-0-64, 10 va

Earlier (post 527) in a response to Miguel, I stated that resistor locations were suitable for front end insetion points...duh...Jens put them (and labeled them) on the board, right there...you guys missed your chance on that one. 😀
 
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#577
Ed LaFontaine said:
Ok, an attempt to sumarize:

R4 = R7 = (Vrail - 40)/8.2

Along with that the active devices and caps need to be chosen to (at least) have adequate V & I carrying capacity. Other flavor of the month issues notwithstanding...don't want to get into osculation. 😀

I was afraid it would be more complicated than that...flamesuit going on now...

A "target" range for the front end transformer (75V rails) is 64-0-64, 10 va

Earlier (post 527) in a response to Miguel, I stated that resistor locations were suitable for front end insetion points...duh...Jens put them (and labeled them) on the board, right there...you guys missed your chance on that one. 😀
Click to expand...

Funny guy😀

But isnt it more fun having to do some homework to build this?
Your front end transformer looks right, I expect youll have to settle for 65 0 65 or maybe 70 0 70.
 
#578
jacco vermeulen said:
Class A+ is a combination of of a high bias, low rail voltage Class A stage, and a tracking Class AB amp that drives the ground side of the rail capacitor banks.
Rail voltage is raised with increasing output (raised input voltage level), is Class A operation with a much lower dissipation level.
The same principle could be used to keep rails voltage upright on a Class AB amp.
Click to expand...

Ive never heard of this, who builds this stuff and how old is Class A+?
It seems very complicated for an amp.
 
#580
ah thats what I was reading about last night, looked up the SE-A1 after your post and followed a diyaudio thread about this amp. I like the look of these Technics.
In the 70s, you could just about buy a house here for that sort of money🙂
 
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