[Robin W.]

Hi Ferrari, here's a bigger version of that pic.
The amp is similar to a pimeta, but instead of buffers it uses parallel op-amps, along with the TLE and an active ground channel. There is a preamp out that is controled by the main vol, which is only active with the headphones removed (like your average receiver) There are switches on the back to select high/low gain and to use or bypass the input coupling caps depending on your source.

 

[Ferrari]

Thanks for sharing!

Don't forget to post pics when your amp is completed.

 

[iareConfusE]

 

[diddy1234]

Hi all

here's my attempt to build a slimline amp.
I originally wanted to build a Cmoy amp but here in the UK its almost impossible to get the op amps.
I could have brought one from Ebay but where's the fun in pre built. I wanted to build my own.
So searching around I found a stereo amp based on the TDA2822 chip.

specs :-

TDA2822 stereo amp (complete amp kit from Quasar Electronics(
Case, LED, knob from Maplin electronics
power supply 3.6volt ni-cad rechargeable, 330ma
Output impedance 4 - 32 Ohm
Freq. response ~ 30 Hz to 100 kHz, 16 ohm
S/N ratio > 80 dB

I have not measured the power output yet but it is really loud
The biggest problem with building this amp was that the internal case size is 11mm.
The circuit hight is 10mm (without solder connections) so everything had to be shoe horned in.
I also had to insulate the circuit board as well from the ali case.
Also the volume control is actually 16mm diameter so I made a small cut out in the bottom of the case below the volume control to enable the volume to fit the case.

The sound quality is very good (to my ears at least) and is slightly bright on the higher frequencies but then this compliments my Schenniser IEM's very well.

The sockets on the back are power on/off, and a USB pass through using two USB sockets.
This is also how the battery is charged up.
This allows me to plug my mp3 player into the back of the amp and then use one USB lead to charge my mp3 player and charge the amp.
The charge current is about 25ma for the 330ma battery, so about 10 hours of charge time is needed.
the amp lasts about 6 hours of listening before charging is needed.

Overall this is the smallest amp that I have made (without going to surface mount building) and works very well.
Total cost was around £40 including the battery and all leads.
I would only recommend the brave try to build something this small.

 

[adamus]

finishing touches applied to the speaker amp.

 

[rhys h]

Very nice adam. Do you have a schematic?

 

[adamus]

yes - its based on this, but with a few mods thown in, e.g i am running at 340v B+ so i had to change the CSS (the square labelled 'bias') to a reduced current (to keep withint the 12w maximum dissapation of the el84).

I also removed NFB (just get rid of the 12k). I also had a play with the 16k shunt feedback resistor, and settled on 22k.

Credit for the schematic goes to gingertube (very helpful chap on DIYaudio).

 

[rhys h]

Thanks, looks great! Can i ask where you managed to find the output transformers?

 

[adamus]

bluebellaudio.co.uk

the guy that runs it is probably the most helpful man on earth too.

I used the hammond 1650e.

 

[rhys h]

Cheers, any idea on the total build cost? Also do you know the power output?

 

[adamus]

total cost... about £290

power output is just over 12 watts per channel.

 

[onform]

I went down to my local plastic suppliers today to see if I could find a surplus piece of clear perspex, (they have cages full of different plastics just sitting outside that is going to be dumped), for something i'm trying out before i buy a decent piece. And I found this sitting on top of one of the cages...!

It turns out that this inconspicuous company churns out the cases for a small but well respected audio company..

Now some of the print is a bit dodgy and there is a slight scuff on the face plate but I don't care... I just got to figure out what to put in it!

I think I may pop in there again to see what else they decide to throw out!

 

[V-DiV]

Quote:

Originally Posted by adamus /img/forum/go_quote.gif finishing touches applied to the speaker amp.

That's pretty

. I like the nice simple look of your amps. I'd love to build a transformer-coupled headamp for my K701 eventually. I love the look of all the tubes and iron. I'll proudly display the tubes and transformer on the Bijou I am preparing to build.

 

[adamus]

cheers mate. Its a heavy beast that one!

 

[-=Germania=-]

Onform, what size is the case?

A nice, free case like that might just be worth throwing a custom front panel on like those from Front Panel Express.