The most advanced GainClone amp yet

[sharpi31]

Thanks Peter - I too have been loving your LM3875 pcb. I built my first one using the standard component pack and was blown away.

The second amp i built is a bit over the top (in spec, not in build!): huge bank of panasonic fm (12000uF per rail) with 100uf black gate N on the amp pcb. I've also got a 0.1uf black gate NX right on each power supply pin. Cheap ebay stepped attenuator, alps source selector. Each of the 3 analogue inputs has different coupling caps (horses for courses, and i never need more than one line in so i have the choice). I've also got a monica 2 dac board inside the chassis with separate transformer, rectifier bridge and psu cap bank.

Anyway, your work really impresses me - thanks again :-)

[KT]

Originally posted by Peter Daniel Just bend the pins, here's one example:

Hi Peter, Great work, as always. A couple of questions: 1) When bending the chip pins back a la the Patek, how do you get the bolt through the chip to secure it to the heatsink? Seems that the board is in the way. 2) I have enough boards to make the bridged dual-mono version the the Gainclone. Any pointers on how to connect the two sides of the chip together to parallel them? I'm inspired by the dual-mono Patek that was favorably reviewed on 6moons.com. I may also email you about ordering a couple of the AudioSector PS boards - I have the v.1 Chipamp boards from the initial PD/Brian GT group buy and would like to take advantage of the wider pin spacing of the AudioSector PS board in order place the 1000uF caps at that location. Thanks, KT

[twitchie]

Originally posted by Peter Daniel
The switching module is an add on and can be removed if not used.

Hi Peter, those look like Audio Research toggle switches, can you share where you got those from? I've been trying to get a replacement switch for months now and the local dealer want's alot of money for one. Are they the same ones?

Thanks,

Stephen

[twitchie]

Hi Peter, those look like Audio Research toggle switches, can you share where you got those from? I've been trying to get a replacement switch for months now and the local dealer want's alot of money for one. Are they the same ones?

Thanks,

Stephen

[Peter Daniel]

Those are TOCOS with silver contacts available from percyaudio.com They perform very well here.

[Peter Daniel]

Originally posted by KT
1) When bending the chip pins back a la the Patek, how do you get the bolt through the chip to secure it to the heatsink? Seems that the board is in the way.

2) I have enough boards to make the bridged dual-mono version the the Gainclone. Any pointers on how to connect the two sides of the chip together to parallel them? I'm inspired by the dual-mono Patek that was favorably reviewed on 6moons.com.

I install the chip first, then the board. To remove the chip, you need to remove the board. But only 5 pins need to be soldered.

The wiring diagram for bridged/parallel version of LM4780 chip was posted here: http://audiosector.com/lm4780%20amp.pdf
Doing it with LM3875 is the same.

Srajan still uses those amps, here the link to a more recent review when they've been featured: http://6moons.com/audioreviews/esoteric4/trio_2.html

[luvdunhill]

Originally posted by Peter Daniel
The most advanced GainClone amp just got better:

Peter:

How exactly do all those switches work? Are they 4PDT?

[Peter Daniel]

Those are simple DPDT on/on…(TOCOS from Percy). In one position source is on, in the other it's off, such setup allows multiple sources connected at the same time, or switching single channel only (one switch per channel, switching both positive and negative signal, as it's compatible with balanced inputs as well)

[luvdunhill]

So, in the case of the balanced, the grounds are not switched? I was thinking of something similar using the TOCOS 4PDT with a preamp with an input transformer. I'd like a two source selector. I'd put the input and ground of both SE channels on one side, and the positive and negative of the balanced source on the other side. Not quite sure what to do with the balanced ground connection though

[Peter Daniel]

You can add another switch for ground lift, so you can either have it hardwired or floating.

Drop me an email and I can send you schematic from Bentaudio for wiring transformers.