AudioCircle
Industry Circles => Sonic Craft => Topic started by: OSIB16 on 7 Dec 2022, 01:04 am
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I wanted to use this thread to document the progress of my latest project; which is a pair of Hifi Monoblock Power Amplifiers based on the original Gainclone design with a LM3886 chip ((all built from scratch)). But there is a twist, because I am going to be using super exotic components (capacitors, resistors, RCA sockets, binding posts, point to point wiring etc), including significant improvements to the circuit layout and chassis, with the aim of solving the common issue of overheating, and increasing transparency/purity. Not forgetting; that I will be removing as many obstacles in the signal path as possible (without compromising functionality and reliability of the finished amplifier).
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Below is an actual photograph of my completed monoblocks. Note that I purposely attached some aftermarket B&O stickers to the front of the aluminium cabinets, mainly for the purpose of covering up holes in the metal chassis where a button was originally mounted, and also because I happened to have the stickers laying around the house.
(https://www.audiocircle.com/image.php?id=247315)
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Credit goes to Jeff for helping me compile the list of components; including his recommendations for the circuit layout
After I did all the basic engineering of the chassis/fitting all the relevant parts onto it, the amplifiers were then sent to my friend Brent Rowe at www.fidelityaudio.com who ensured that everything was correctly wired together, and working properly. He performed all the relevant electrical tests etc, to ensure that the finished amplifiers were fully functional.
(((THE END RESULT IS THAT THE AMPLIFIERS RUN SUPER COOL - VIRTUALLY NO HEAT)))
Here is the component list:-
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‘TWO’ SOLID ALUMINIUM CABINETS (ORIGINALLY FOR MINI PC BUILDS).
‘TWO’ LARGE DONUT SHAPED ALUMINIUM HEATSINKS (ORIGINALLY FOR INDUSTRIAL USE).
‘TWO’ IEC SOCKETS (WITH BUILT IN ON/OFF SWITCH + FUSE).
‘TWO’ LM3886 AMPLIFIER CHIPS.
BREAD BOARDS FOR RECTIFIER AND MAIN (ALL COPPER TRACKS SCRAPED OFF)
‘TWO’ TOROIDAL TRANSFORMERS - 225VA / 2x25V (DISPLAYED BELOW)
(https://www.audiocircle.com/image.php?id=248921)
‘TWO’ KLE INNOVATIONS COPPER RCA SOCKETS.
FOUR NICKEL PLATED SPEAKER BINDING POSTS
((Used only as clamps // Completely disconnected from the electrical signal)).
20 AWG OCC SILVER PLATED COPPER WIRE - 99.9999% PURITY
((For point to point wiring of all components on the main circuit board)).
16 AWG DUELUND COTTON/OIL STRANDED COPPER WIRE
((For jumpers that link both the RCA Socket and Speaker Binding Posts to the main board)).
14 AWG NEOTECH UPOCC COPPER SOLID CORE WIRE - 99.9999% PURITY
((For IEC Socket jumper bars)).
13.5 AWG SUPRA LORAD STRANDED COPPER WIRE - 99.999% PURITY
((For IEC Socket ground wire with ferrite magnet))
11.5 AWG SUPRA STRANDED TIN COPPER WIRE - 99.999% PURITY
((For jumpers that link the Rectifier Board to Main Board))
‘SIXTEEN’ FAIRCHILD STEALTH DIODES - 15A / 600V
((For Rectifier bridge)).
‘TWO’ MIFLEX KPCU-03 FILM CAPACITORS - 1UF / 250V
((For main circuit board)).
‘TWO’ TAKMAN REX CARBON FILM RESISTORS - 1Kohm / 1/4 RESISTORS
((Main circuit board)).
‘TWO’ TAKMAN REX CARBON FILM RESISTORS - 22Kohm / 1/4 RESISTORS
((Main circuit board)).
‘TWO’ TAKMAN REY METAL FILM RESISTORS - 1Kohm / 1/4 RESISTORS
((Main circuit board)).
‘FOUR’ TAKMAN REY METAL FILM RESISTORS - 22Kohm / 1/4 RESISTORS
((Main circuit board)).
‘SIX’ ELNA SILMIC II ELECTROLYTIC CAPACITORS - 100UF / 50V
((Main circuit board)).
‘TWO’ ELNA SILMIC II ELECTROLYTIC CAPACITORS - 22UF / 50V
((Main circuit board)).
GOERTZ 99.99% M2 PURE COPPER STRIPS - “EQUIVALENT TO 10 GAUGE WIRE”
((For rectifier board / To mount components onto)).
‘FOUR’ MUNDORF MLYTIC AG ELECTROLYTIC CAPACITORS - 10,000UF / 63V
((For rectifier board)).
‘FOUR’ REL CAP RTE FILM CAPACITORS - 0.01UF / 200V
((For rectifier board)).
‘FOUR’ SONICAP STAGE III FILM CAPACITORS - 0.10UF / 200V
((For rectifier board)).
‘FOUR’ PRP RESISTORS - 1W / 2.2Kohm
((For rectifier board)).
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Below is an actual photograph of my completed monoblocks. Note that I purposely attached some aftermarket B&O stickers to the front of the aluminium cabinets, mainly for the purpose of covering up holes in the metal chassis where a button was originally mounted, and also because I happened to have the stickers laying around the house.
(https://www.audiocircle.com/image.php?id=247315)
That looks pretty cool!! it kind of reminds me of a slide projector.
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Congratulations its a beautiful amp, first class job :thumb:
How much W do you could say they delivery in 8/16Ω ?
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Thanks. The amps produce 35 Watts into 8 ohms. But the best news is that they run as “COOL AS A CUCUMBER”. No matter how hard you push them; THEY HARDLY GET WARM!! However; bearing in mind the fact that heat rises; The lack of overheating in my amplifiers can be attributed to the circuit layout, where all components have been fitted onto the roof of the aluminium chassis ((ie. the underside of the lid)), with sufficient space and open ventilation available inside the unit. Not forgetting the big circular heatsink fitted on top. Also the larger gauge wiring and the wide copper foil strips in the rectifier, which help to absorb the electrical current.
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Point to point wiring…
(https://www.audiocircle.com/image.php?id=247342)
(https://www.audiocircle.com/image.php?id=248602)
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Simple layout. Not pretty, but does the job…
(https://www.audiocircle.com/image.php?id=247344)
(https://www.audiocircle.com/image.php?id=247325)
(https://www.audiocircle.com/image.php?id=247326)
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Rectifier wired up…
(https://www.audiocircle.com/image.php?id=247327)
(https://www.audiocircle.com/image.php?id=247333)
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Isolation Platform for transformer…
(https://www.audiocircle.com/image.php?id=247330)
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Rectifier board layout…
(https://www.audiocircle.com/image.php?id=247332)
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Direct signal contact to the internal wiring…
(https://www.audiocircle.com/image.php?id=247336)
(https://www.audiocircle.com/image.php?id=247803)
(https://www.audiocircle.com/image.php?id=247338)
(https://www.audiocircle.com/image.php?id=247341)
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Very nice,are they class ' A' .
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Very nice,are they class ' A' .
Thanks, they are Class A/B
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Very nice build. They look badass.
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(https://www.audiocircle.com/image.php?id=247333)
Nice assemblage, these rectifiers are hard to mount.
What your impressions on these Fairchild?
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Tyson,
thanks I aimed to make them as compact as possible. Didn’t want them to take up lots of space, and wanted them to be easy to transport.
Fullrangeman,
Rectifiers are Fairchild Stealths, as recommended to me by Jeff. I understand that they are up there up with the best. I spent ages using a set of tweezers and pliers to carefully bend/curve the legs; which allowed them to be slotted into the holes of the Goertz M2 copper foil strips.
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Here is a simplified version of the schematic for the ‘Main Board’. Some modifications were done to the layout; to keep the electrical pathway as short as possible, while maintaining efficiency and safety…
(https://www.audiocircle.com/image.php?id=247804)
(https://www.audiocircle.com/image.php?id=248599)
(https://www.audiocircle.com/image.php?id=248600)
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I'm interested in this design and I'm able to understand most of it between photos and explanation. However, I have a couple questions.
In the above layout diagram with purple background, what are the white circles? I see location where only one component connects or dead-ends, while another component connects on one end to two circles but nothing else. What do these circles represent? They don't seem to correlate to ground, or to being individual terminals.
Secondly, regarding cooling. I could see how you gain some minimal cooling through larger gauge wire and the copper foil, but are there any components that are directly connected to lid/base for heat dissipation, or is the cooling passive simply through the high surface area aluminum lid dissipating heat from the warmer air below?
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White circles are the pins of the chip. It's a standard 15 pin multiwatt layout.
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Ezee the statement that Folsom made is correct. As for the cooling issue; all components are attached to the underside of the cabinet lid, with a donut shape heatsink strapped to the other side of that same lid. The reason that I did this is because we all know that heat rises. Therefore any heat from the internal components is immediately transferred to the cabinet lid that they are screwed onto, which then soaks through the donut shape heatsink, and dissipates up into the air. But to be honest; I don’t think think that the heatsink is even needed, because it’s always cool to the touch. You could probably get away with not using one.