Gainclone building contest details (from BrianGT group order)

[platenspeler]

platenspeler,

I see you used the BrianGT boards by keeping the rectifier PC board attached to the amplifier PC board .

I find that very interesting. I have a set of Brian's boards running now a wood board to get everything tested and working. Sounds great! But I was having noise problems initially

I have the same implementation you do with the rectifier boards attached to the amplifier boards. I originally had the inputs connected with some teflon coated Cat5 cable wire that I had and I was getting quite a bit of noise at the output. It was not 60Hz hum but higher so I figured I was getting 120 Hz noise from the Diodes. I got rid of it by using sheilded cable to the inouts and grounding the sheild. So I figured that the attached board approach would just not work with unsheilded wire unless I separated the rectifier board from the amp board. Looks like it works for you though.

Perhaps since your run is short it works or perhaps I had some other issue. My wire was about 8" long at the time and I do get quite a bit of RF where I live. So you have no noise problems?

I do not have noise problems. Did you twist the transformer wires and the mains AC wires? I did twist the cat5 input wires too.

Did you shield the toroid part from the amplifier part?

Maarten

 

[platenspeler]

Maarten, not only brilliant looking amps, but also briliant pics too. That's always a good thing

I hope your amps aren't getting too wet on that bench though

Vikash,

Thanks for the compliments. I did not like the first two pictures posted on the red tablecloth taken just after finishing the amps.

So I took them outside in the morning and made a few shots in the early sunlight. The table was quite wet indeed but I liked the affect of it in the composition.

regards,

Maarten

 

[wyomitch]

Troubleshooting question

Hi, this is my first post so please forgive me if this question should have been posted elsewhere.

I recently assembled one of Brian's gainclone PCB's in the premium configuration. I have assembled the amp on a piece of wood and some scrap metal. The problem is that one channel sounds fine and while the other has very faint output. As I really do not know where to begin to isolate this problem I was wondering if anyone had a thought about where the problem might lie? Hopefully something short of taking it apart and re-soldering everything?

While the “poor” channel produces sufficient power to drive a speaker, it does so at much lower levels than the other channel. I have wired the “poor” channel directly avoiding the potentiometer and the problem still persists.

Any ideas would be appreciated.

The one channel that works very well indeed.

Thanks,

Mitch

 

[moving_electron]

I do not have noise problems. Did you twist the transformer wires and the mains AC wires? I did twist the cat5 input wires too.

Did you shield the toroid part from the amplifier part?

Maarten

I did twist the AC and cat5 input wires when I tried them. Still I somehow made a pretty good antennae I think as I could affect the amount of noise by toughing the input wires.

I did not shield the toroid. It was about 6" away. The noise did not sound like 60Hz so I am thinking it was the toroid.

I may never know why the Cat5 did not work as I am in the process on moving the completed amp to it's final metal box and will likely use the shielded, grounded cable since it is working fine this way.

I have Microwave, radio and UHF towers near by so perhaps I will end up always having using sheilded. I'll try some more experimentation though next round.

 

[karma]

Re: Troubleshooting question

Hi, this is my first post so please forgive me if this question should have been posted elsewhere.

I recently assembled one of Brian's gainclone PCB's in the premium configuration. I have assembled the amp on a piece of wood and some scrap metal. The problem is that one channel sounds fine and while the other has very faint output. As I really do not know where to begin to isolate this problem I was wondering if anyone had a thought about where the problem might lie? Hopefully something short of taking it apart and re-soldering everything?

While the “poor” channel produces sufficient power to drive a speaker, it does so at much lower levels than the other channel. I have wired the “poor” channel directly avoiding the potentiometer and the problem still persists.

Any ideas would be appreciated.

The one channel that works very well indeed.

Thanks,

Mitch

i had that problem. look over your resisters make sure there in the right place. i have the basic kit and i had a problem looking at the colors on the resisters because there so small. would be nice if thats all it is.

 

[wyomitch]

Thanks Karma,

I took it apart and found that I had switched two resitors that I didn't realize had different values.

Mitch

 

[okina]

220pf at doc

hello.
my friend told me that 220pf cap inserted between
+in and -in work more stable.
and the document also say so.
but where should I insert the cap do you think ?

between R1 and R2 connect to SG, work as RC filter
or, connect +in and SG
or, connect +in and -in
or so....

 

[mhr]

I guess it is my turn to post some pictures (this is my first post on this forum). So let me introduce my GC using BrianGT boards. Main ingredients:

- BrianGT premium kit
- 300 VA 2*18 V toroidal transformer
- DACT CT2 stepped attenuator

And here is the result:

 

[mhr]

Another view:

 

[mhr]

And finally a peek inside the chassis:

 

[BrianGT]

mhr,

I like your amp. I would like to add your pictures to my gainclone gallery. If you are willing, can you e-mail me some pictures (800x600 preferred) to my mail at:
pictures@tastybeef.com

Anyone else that wants their gainclone built with the boards put in my gallery, feel free to send an e-mail to this address with pictures. Don't worry if they are too large, as I can size them appropiately.

--
Brian

 

[the_wonderchild]

Hi mhr

I really liked your GC amp and was wondering how did you make or where did you find the case you have used for the amp.

Thanks

 

[mhr]

Hi Wonderchild,

I am glad you liked my amp. The case is bough from an Italian company called Audiokit. Model is Galaxy Maggiorato and type is GX288. I have seen similar cases available from bigger vendors also, but never in the higher (= Maggiorato) version. I am not sure if they ship overseas, but inside Europe everything seemed to work fine despite their horrible web pages.

The aluminium block inside is custom made.


Mikko

PS. BrianGT: I will send higher res pictures to you later today.

 

[Bas Horneman]

My first gainclone ever..finished...

Built it quickly in whatever I had lying around..so I could listen...have had these boards finished for ages...and finally got round to building it..it's now 3am in the morning ...but I am going to bed content.

It actually sounds very very good!

The first thing I noticed...being used to my 4 watt or so SE amp...is that the gain is MASSIVE....the other thing is that my dc voltages where ALL 36,3 V...on both channels...the + 36,3 and the minus was 36,3.. so four measurements of 36,3v..

I've found one curious aspect that I have not read anywhere else..(and one that I have read of before)..

When I have my DVD player (transport) turned off...I hear an immense amount of hissssssss...with the player...playing..or just on..the noise goes away???

The thing I have read about was...the sensitivity to the mains...switching the cd player on...a massive thump...(more a click really) can be heard.....why would the gainclone be so sensitive to this?

Any way...I am a happy chappy and will report back after it has burned in.

By the way ...I am using it as a power amp..My preamplifier is a tube based transformer coupled pushpull parafeed amp (Raleigh Audio Linestage) aka Mood Indigo.

I've always found the following link one of the most absurd on audio....but I've waited before commenting..until I had actually heard my own gainclone...
http://www.hilberink.nl/amps/lm3875schema.htm
I now know that the joke is on him!!!!

An externally hosted image should be here but it was not working when we last tested it.

 

[x. onasis]

Welcome to the club, the sound is a surprise isn't it? Thank you for your post and pic. With your wire color choice, this is one of the clearest demonstrations of wiring Brians kit for the newbie builder, but I notice you've left out the mains and chassis grounding as well as a fuse, so I thought I'd point that out.

And maybe this could be the reason for your hssss ??

Anyway, I glad to hear I'm not the only one who finishes these projects in the wee hours.

 

[yootk]

I've always found the following link one of the most absurd on audio...http://www.hilberink.nl/amps/lm3875schema.htm.but I've waited before commenting..until I had actually heard my own gainclone...

HI Bas,
I've just check the http://www.hilberink.nl/amps/lm3875schema.htm. It is really funny that the site enthusiastically quote an opinion of a guy who built only one channel of a gainclone and criticised at length the worthliness of the GC. I'm neither a GC opponent or advocate but I appreciate an honest critic.
Cheers
yootk

 

[Bas Horneman]

but I notice you've left out the mains and chassis grounding as well as a fuse, so I thought I'd point that out.

Since most homes in the Netherlands don't have ground. I could not see the point of grounding to the chassis.

The fuse was laziness.

And maybe this could be the reason for your hssss ??

Mark25 also from this forum, visited me yesterday and found out the reason. If the dvdplayer is switched of...for some reason the muting transistors of the dac don't engage. The result is that you can hear the noise of the dac.

I'm neither a GC opponent or advocate but I appreciate an honest critic.

I also neutral in this whole GC business. I still like my valve amps more...but for the money and simplicity of building the gainclone cannot be beat. Just one output transformer costs more than the whole gainclone!

 

[tops]

Built it last Night

Ok...Here is Something I built last night whilst sleeping. As good as Peters...!

 

[tops]

Moi GC

And here is something I built some days before.

 

[fcel]

Peter lend you those pictures, right?