Commercial Gainclone kit- building instructions

[Peter Daniel]

The bottom line is that I offer whatever I use myself. All the kits and projects are extention of the circuits I initially built/designed for my personal use. If something doesn't work as expected, you won't see me promoting it.

The circuits for bass/treble controls are usually popular with lower end systems. While you can adjust frequency response to your preference, other aspects of reproduced music usually suffer and the sound becomes less convincing. For me it's a trade off that is hard to accept.

So even in a system that I presently use while working on my new workshop, tone controls are always off

For me, it's the 'purity' of the sound that matters the most, with tone control, that 'purity' is (usually) lost.

[zebra100]

Hi Peter,

I have recently completed one of your premium kits (LM3875). I have used 2 transformers (120VA, 18V) and 2 rectifier boards in the same case. I initially intended to make 2 monobloc's but had a last minute change of plan.

I connected 4 wires between each of the rectifier and amplifier boards (V-,PG-,PG+,V+) and then the L+R CHG connections to the chassis earth point with a 10ohm resistor on each. I wanted to try and keep both channels seperate, but this is causing a low hum. I have tried it with and without the resistors, and I get more hum without them. I am also getting some distortion in the low frequency range.

Is there any reason why I can't use the same set up as you have used (page 4 of this thread), connecting both channels together with 14ga solid copper wire, or will it have to be modified in some way?

Regards,

Chris.

[Peter Daniel]

What happens if there's no connection between CHG and chassis earth point?

If it helps, you could use the same set up as on page 4 of this thread, connect grounds from both rectifier boards there and from here to earth point on a chassis.

[Bluto]

Hi John -

It's just another 'newbee' question. 'We' don't understand this stuff. The simple explanation that it adds unneeded complexity to signal path and purity is sacrificed as a result is as far as most of our knowledge gets us but is adequate to put question to rest. That we now know design is such that attempting to add such is not possible with this design stops 'us' from attempting something that not only would not work but would cause damage trying. We hopefully learn the why's later.

Thanks Peter -

Bluto

[seventenths]

Originally posted by Bluto


That we now know design is such that attempting to add such is not possible with this design stops 'us' from attempting something that not only would not work but would cause damage trying. We hopefully learn the why's later.



Bluto

Bluto,
Thats not at all what he said. You may want to re-read the prior post.
If you'd like to add tone controls have a look around the ESP site.


7/10

[CFT]

Hi Peter,

1) Noticed your suggestion on the value of snubber is 0.1ohm/ 3.3nF. Could I use it on the 22,000 uF Panasonic TS that I already have on hand? (There is another set out there with value of 1ohm/ 100nF, do they both yield similar results?)

2) The 22,000 uF caps will be shared by three chips. Since I have some extra 1,000 uF FC, is there any merit if I also use them right near each chip?

3) For I/P cap, I wondered if 4.7 uF BG NP would be a better choice than for instance, Panasonic polypropelene or Auricap, etc.?

Thanks for your advice~!

CFT

[rfenergy]

Hello Peter,

I have some caddock MK132 22k resistors, would these be ok for feedback resistors? Or do I need the 22.1k resistor?

Also I am thinking of ordered Antek brand 300VA 22+22 toroid transformers are these any good?

Or should I get the 400VA 22+22 version?

Does this brand suck?

Thank You,

Robert

p.s. peter, (I think) you sent us the blue gold plated boards (unless all the boards are blue), thank you for the upgrade (classic kits were ordered).

[rfenergy]

Also,

I have some 330pf 50V polystyrene caps for RF blocking if needed, they are big(5mm X 12MM). How do you mount the between pins 7 and 8? If needed will the big size cause other problems?
Thank You Again.

Out Here,

Robert

[Peter Daniel]

Originally posted by CFT
1) Noticed your suggestion on the value of snubber is 0.1ohm/ 3.3nF. Could I use it on the 22,000 uF Panasonic TS that I already have on hand? (There is another set out there with value of 1ohm/ 100nF, do they both yield similar results?)

2) The 22,000 uF caps will be shared by three chips. Since I have some extra 1,000 uF FC, is there any merit if I also use them right near each chip?

3) For I/P cap, I wondered if 4.7 uF BG NP would be a better choice than for instance, Panasonic polypropelene or Auricap, etc.?

1 The use of snubber with chipamps was introduced by CarlosFM and he changed suggested values few times, I'm not sure what would be the difference between those two sets of values. I expressed my views on snubbers here: http://www.diyaudio.com/forums/showt...981#post838981

2 You may try adding small caps directly at the chips and the overall effect can be only assessed when listening to both setups (with small caps and without).

3 BG N 4.7/50 (or 10/50) is my first choice for coupling applications. The only other cap that I prefer is teflon V-Cap.

BG N is sensitive to orientation; I chose long pin for output.

Originally posted by rfenergy
I have some caddock MK132 22k resistors, would these be ok for feedback resistors? Or do I need the 22.1k resistor?

Also I am thinking of ordered Antek brand 300VA 22+22 toroid transformers are these any good?

Or should I get the 400VA 22+22 version?

Caddock 22k would be the same as 22.1k. You may even use 24k and it won't make any substantial difference.

I'm not familiar with Anteks, but they look good on pictures. If there is not much difference in price, 400VA is proabably a better choice.

All PCBs are blue now. If I'm out of stock in tin plated, gold plated is supplied instead.

Originally posted by rfenergy
I have some 330pf 50V polystyrene caps for RF blocking if needed, they are big(5mm X 12MM). How do you mount the between pins 7 and 8? If needed will the big size cause other problems?

I don't think the big size will cause any problems, just mount them hanging in the air trying to reduce leads length.

[rfenergy]

Peter,

Do you think a 400VA 25+25 would be even better than a 400VA 22+22 transformer?

I have read as much as I can on transformers here. I was thinking there would be less current inrush (turn on thumping,less problems with lower than 8ohm loads) with a 22v vs a 25v...what is your experience?

Thank You,

Robert