Yet Another Newbie Gainclone

[Kofi Annan]

With some initial guidance concerning basic electricity from a few forum members, extensive studying and research on Decibel Dungeon and forum posts (I used Llammas' post here ), I have made a semi-crappy attempt at my first amplifier-- a Gainclone.

Thanks to all who participate in this forum. The guidance I received here has been indispensable. While I realize that my amps (still need to make a box for the other one) will not be a showcase piece at an audiophile convention it means a lot to me that they are completed. I had absolutely no experience in electronics until I began to study basic electricity three months ago. I built a few low-power amps along the way to get used to soldering and to gain an understanding of the basic concepts (Example: your thumb and forefinger make a really bad signal ground), but I have completed this due in large part to the posts and the responses to my questions that I received in this forum.

Of course, I have a few more questions:

1. There is a rather annoying "power-down thump" in the amp. From what I have read on the forums this will not damage the speaker, but I'd like to get rid of it if I can. Any suggestions?

2. I don't have a "star ground" per se and I don't notice any ill effects. Is there a side effect that I will not notice that will eventually kill me and my family or damage my speakers / amp?

3. I get a little (VERY little) RF interference in the amp. Since I don't really want to rewire the whole thing, can I line the case with foil and get away with a moderate amount of shielding?

4. I have kinda crappy Technics speakers (I'm slowly upgrading all of my audio equipment from the Sears specials I own to something a little more reasonable) and I notice that the highs sound like they're (novice talk here) "tearing" the tweeter. Does this sound like just a crappy speaker or could it be the source, speaker cables, RCA cables, etc.? Maybe I need a line level preamp? I'd also like to build a set of speakers next-- can anyone recommend a cheap / inexpensive DIY speaker kit or design?

By the way, I know that the electrical tape holding the panel mount fuse is unacceptable. I plan to change this soon, but I wanted to make sure it worked in the box.

Thanks again for all the guidance and thanks in advance for any additional remarks or "constructive criticism" you can offer.

[Kofi Annan]

Another photo of my ghetto GC and one more comment. My favorite part of this construction came three days ago when I went to my local electronics shop. I needed something to act as legs / feet for the amplifier box so I talked to the crusty old barnacle behind the counter and the conversation went like this:

Me: Excuse me, but do you have rubber feet?

Barnacle: Yes, I do.

I really enjoyed that.

[sss]

Originally posted by Kofi Annan
Another photo of my ghetto GC

nice one

[analog_sa]

Stunning workmanship indeed. Bet it sounds as good as it looks.

[hacknet]

try shortening the wires between the cap and the chip, i`ve got better sound with shorter leads.

[B.I.G]

A prototype board could have been more confortable .

With your conections you can get your amp dead if you use p2p you should make sure that all the components are rigid .

[Kofi Annan]

I know I'm in for some rewiring. This was my first real attempt at a project so while i planned to make it neat, I wound up settling for this.

I'm waiting for some enclosures to show up. When I transfer this from the prototype box to the real enclosures, I'll plan the rewiring effort and make sure all the components are secured and the wiring is rigid.

I fixed the "power-down thump" and I found the cause of the tweeter "tearing", but I'd still like some answers to my other questions, if anyone would be so kind.

Learning. Always learning.

[fedde]

It would surprise me if your amp is not oscillating like hell...
Really, try to build it 10x more compact! Solder all wires, avoid connectors. Some more information about layout can be found on my website (see below). If you don't want to make it more compact with PP try PCB's...

BTW: my experience is that oscillation often causes power down thumps.

Ciao,

Fedde

[Kofi Annan]

Thanks for the advice. I was concerned about buiding the power supply too close to the chip, but if you think I can compact it, I'll make sure that I get it closer.

I'll rewire once I get the new enclosures. Also, thanks for the link to your site-- I've been there before and its very helpful.

I thought about PCBs, but I thought they might have been more trouble than they were worth. Now that I see the outcome from my point-to-point debacle, I'll PCB in the future.

Any advice on a DIY home speaker kit (cheap / inexpensive one. preferrably)?

[fedde]

The location of the transformer and bridges is ok, I wouldn't put them too close to the opamp. I would connect the supply wires on the same side of the connect block as the wires from the bridges. Then the wires will make direct contact. Put the large caps as close as possible to the opamp, and the feedback resistor even closer...

In the beginning I didn't like the idea of PCB's too, but now I wouldn't make an amp without. Especially when you regarly modify your amp, the solder connections of a PP amp can get bad... (it's really hard to make good star grounds with five wires in the air you know...)

Fedde