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AudioSector-chip amp kits, dacs, chassis

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Those are pretty expensive.

From what I've read so far, it doesn't neccessarily has to be 0.1 ohm value. In case of bigger mismatch between chips, even 0.5ohm is quite acceptable (and actually beneficial), so 0.47, 3W Panasonics from Digi Key can be used here as well. It will just generate bigger voltage drop, but with higher impedance loads, and average power levels, it shouldn't be a problem.
 
Here we go, a version with dual output resistor footprints. Caddocks MP-820 and MP-930 can be used as well.
Thanks for suggestion, pinkmouse ;)
 

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Peter Daniel said:
I'm slowly running out of LM4780 boards, and i was considering a revision, with updated layout, accomodating all 3 options: parallel, balanced and stereo.

If balanced would be to implemented, the board does not use inverted method (like per AL-1192 notes), but both halves are non inverting and additional circuit is required.

I will be comming with balanced active line stage, so that could be used there, or I might include a small board, implementing LM6172 for buffering and phase splitting.

Below is the proposed layout I was working on yesterday. As you see, the signal traces lengths are substantially reduced, there is more separation (in layout) between both sections and the chip can be also used in stereo mode, providing same funsctionality as two LM3886 chips.

If stereo or balanced operation is looked for, the balast resistors are not required and output is taken directly before those output resistors. In case of parallel operation, resistors should be in place and there is one output only.

The signal grounding is very symetrical for both channels and also simplified.

I plan to do mirrored boards (2 amp board per one main board, as usually). So if someone uses boards for balanced operation, they can be put back to back with PS connections aligned for paralleling. A multiple number of such parallel modules could be connected in parallel (with bus wires for supply) providing simple power distribution scheme and high power.

The accompanying PS board will feature all presently popular options (large caps and snubbers);)

As usually, all comments and suggestions are welcome. It will be at least a month before those boards become available.

Peter,

I like your layout. I very much like your thinking ahead for multiple uses, if you can pull that off without getting an awkward board, that'll be great.
You've come a long way, buddy!

Jan Didden
 
This board will be offered at the same price as previous version, yet it offers 4 independant channels. So if someone has already LM3875 (or LM4780) based 2 channel amp, with just one kit can upgrade to 6 channel HT setup, and save substantialy (and not neccessarily in UK ;))

Besides, it seems like LM4780 chip has been neglected somewhat, I'll try to revive some more interest with various interesting implementations.
 
Peter Daniel said:
I will be comming with balanced active line stage.

Hi Peter

This sounds interesting. Will this be a stand alone project or intended for use with the power amp boards?

One of the aspects of the Gainclone that appeals to me is that the size and price make it attractive for use around the home to power speakers in different rooms, all fed from a central, high-quality source. A balanced line stage is just what is needed for this.

Colin
 
I spent some time modifying ML380S preamp; it is a pretty good sounding preamp, and apparently one of the most successful products from Madrigal.

I know it's configuration pretty well, there is nothing really propriatory in that preamp (besides volume control), so I was hoping to come up with a design that would be partially based on the building blocks used in that preamp, yet having separate character.


So this would go like that:

Power supply based on MUR860 rectifiers, a pair of 1000u caps (with possibility of upgrading to BG STD), LM2990/2937 regulators which to me are as good as most discreet regulators I tried so far.

Input gain stage based on OPA627 and with switchable gain (2 choices available).

Phase splitting circuit, based on LM6172, allowing conversion from single ended to balanced and vice versa.

Next would be a place for volume control, and here we would have a choice to use either a switching attenuator, matched pots or volume attenuator based on IC (like WM8816 for instance).

The discreet output buffer (modified diamond buffer) would be the most interesting part of a circuit, and I have to experiment here a bit more to fully optimise it (basically make it looking less like ML circuit ;))

The rectifiers, regulators and main caps would be close to a buffer, additonal pair of regulators would be placed at the input circuit. Both sections could be used separately, with buffer being the main attraction.

Another approach to preamp, that I'm also considering, would be using a Jensen transformer at the input (providing buffering and phase splitting), an IC based volume control, and AD815 at the output, basically the configuration used in Rowland Coherence preamp.
 
Peter, that layout looks great. One thing though :) Please consider placing an extra pad on the resistor footprints to allow proper mounting of standard resistors with 300 mil lead spacing. That way it will be possible to build both a high-grade version with caddocks/vishays or a more standard version with standard metal film resistors. Shouldn't be much of a problem and it makes the board a lot more versatile IMHO :)


/U.
 
Actually that board was never really designed with Caddocks or Vishays in mind (although they fit there perfectly). With the kits Brian and me are selling, we are using those 0.5W resistors from Phoenix. They have 0.134" length and fit well in 200mil footprint: http://dkc3.digikey.com/PDF/T051/1011.pdf

If there is more interest in 300mil footprints, I might try to implement it, but this will somewhat affect the planes, which are already looking like Swiss cheese;)
 
I received my PD SE boards today.. They are byooo-teee-full. I'll wire them up when I have some time -- I have about 20 other DIY projects I have to finish first :D I'll probably have to save some of my pure-silver wire to go with my gold plated boards.

Dang. Some of my DIY stuff is starting to look like it belongs around a Rappers neck!
 
Peter,

I would be interested in either a DAC kit with the board and critical parts or a full premium kit, depending on my finances. :D

Would the power and input transformers come with the partial kit? Sometimes it's hard to find parts like this that fit exactly in the circuit board's holes. Then you have to buy and pay extra to ship the same parts anyway.

Thanks,
KT
 
KT,

I should be able to deliver any parts needed for the DAC. It does not feature input transformer though, I prefered the sound with an active driver.

Mike,

I only had two sockets available at a time. Whenever I'll get to Sayal I'll get more and send them later.

I will have the DAC boards tomorrow. They are made the same way as LM3875 SE ones;)
 
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