Minimalist Pimeta

[digi01 0]

heady,your layout is beautiful,full of logic

I am looking forward to your finished amp.Have you find a sexy case for your amp?

 

digi

[aaa 0]

singapore farnell

click on the "up to 50% off - Semiconductor price guide"

http://www.farnell-asia.com/SG/SemisPriceGuide/2.pdf

Page 44 of 58 lower right coner TLE2426CLP

 

And FYI, that Mary originally swear that she cannot find this part called TLE2426, it was only after I insisted that I saw it on the latest farnel catalog that she found it with more search.

[bpribadi 0]

Right, order code 238-7736, price S$2.41. I have the hardcopy of the new semiconductor price guide.

 

But when you search that order code on their website, 'No results found'.

 

When I go Farnell, I will check with the counter.

[heady 0]

Thanks digi01, appreciate your comments very much. I have a black plastic box for it, not very sexy.

 

Unfortunately now the amp oscillates after I added more caps. Trouble-shooting time!! There are two problems. One is a very high pitch and nearly inaudible screeching which is probably oscillation and the other is hum when I touch the input wires. BTW I braided the wires.

 

aaa. thanks for your info. Although I frust about it, still it is better to know so I won't go back to RS again.

Edited October 8, 2004 by heady

[bpribadi 0]

I suggest, change the cap size. Sometime help. And also put very small cap, around 100nF to 1uF very near the Op-Amp (less than 1/2").

 

Hum is normal when the circuit is not shielded with metal casing. Not all braided cables are hum resistant. It is very difficult to find braided cable that is resistant to hum. Try coaxial cable.

 

Nice battery, what size is that?

Edited October 8, 2004 by bpribadi

[heady 0]

Thanks bpribadi, will try it later tonight.

 

Battery is GP brand rechargeable 8.4V NiMh battery. I bought from SLSq for $28 for two together with charger. The charger has no auto switch off so must remember to switch off manually. Still cheap to buy with charger, as the battery is sold for $14.90 each without charger.

Edited October 8, 2004 by heady

[bpribadi 0]

Hi Heady, that's agood buy Looks like the battery is smaller than the normal 9v is it?

 

If you need small caps, come to my place, I have plenty of stock

[heady 0]

bpribadi, let me check if I have a suitable cap first, if not I will sms you. I bought some caps earlier after misreading the labels, so I may have one. The battery is actually a tiny bit bigger than Eveready 9V.

Edited October 8, 2004 by heady

[aaa 0]

Hi Heady, that's agood buy Looks like the battery is smaller than the normal 9v is it?

 

If you need small caps, come to my place, I have plenty of stock

you talking about the yellow 100n/63v cap?

I have bought some 22n ceramic caps at $0.10 each for the PPA's C3.

Wondering whether film or ceramic better?

Personally I don't like the look of the ceramic disk.

[heady 0]

Unfortunately now the amp oscillates after I added more caps. Trouble-shooting time!! There are two problems. One is a very high pitch and nearly inaudible screeching which is probably oscillation and the other is hum when I touch the input wires. BTW I braided the wires.

 

Happy to report that the oscillation and hum is gone once I removed the capacitors which connect V+ and V- to the virtual ground. Somehow that doesn't work for my set-up. I also discovered one of my caps which is connecting V+ to V- is bulging on top. Looks like I have to change it too. I will have to go to Koba and get some replacements.

 

The cap is rated 50V and my supply is only at most 18V, so must be manufacturing fault right? Or is it possible for my circuit to produce higher volt than supply, impossible right?

 

Thanks.

 

[bpribadi 0]

The cap is rated 50V and my supply is only at most 18V, so must be manufacturing fault right? Or is it possible for my circuit to produce higher volt than supply, impossible right?

 

For your circuit, 25V cap is more than enough, so will be smaller for the same capacity.

 

you talking about the yellow 100n/63v cap?

 

My recipe is 100nF yellow plastic cap + tantalum near the op-amp. The tantalum is for small immediate reservoir near the Op-Amp, while the 100nF is for noise reduction.

[heady 0]

bpribadi, what type of cap is the yellow plastic box cap? Polyester? Thanks.

[heady 0]

Hi,

I think I solved the mystery of the bursting cap, it's my lousy soldering. I probably overheated the small cap. Cest la'vie.

 

I have now taken out all the Nichicon caps and replace with four 470uF Elna Silmic caps and two Evox 1.5uF polyester caps, all connected to V+ and V-. The sound was a little harsh and dark. So I added another two 0.15uF Wima polyester caps and two 100uF Elna Silmic caps. The amp is now sounding better and the higher pitches are cleaner. Will let it run in and report progress. Hmm I think I prefer the sound of Nichicon caps although I don't know why there is a difference.

 

Looking forward to the challenge of casing this amp.

 

[bpribadi 0]

bpribadi, what type of cap is the yellow plastic box cap? Polyester? Thanks.

 

Yes, polyester. Any plastic cap will do.

[heady 0]

Would you believe it? Drilling into plastic is just as bad as drilling the tin cans. I am casing my Pimeta and manage to tear the plastic casing with the drill. Major OUCH!! I am hoping the nut used to tighten the sockets etc will hide the tears somewhat.

 

I also manage to forget the positioning of a cap and one of the sockets is obstructed by it. Looks like I have to reposition the cap since I've already drilled the hole for the socket.

 

Stupid things I do but I hope those of you reading will avoid my mistakes. Will post the picture when I move the cap. I feel really at the moment.

 

---

 

Update - here are the pics of my battered Pimeta clone, which isn't minimalist any more!!

Edited October 14, 2004 by heady