Sweet Box - World-Designs-Forum

andrew ivimey · #1 14th January 2007, 02:16 PM

ecc83 into el84 SE, sweet box

andrew ivimey · #2 14th January 2007, 02:24 PM

So, while PansyPanzer is having heater trouble and I drum my fingers on the table waiting for a huge new 12 volt transformer from Germany, I thought I'd knock together an altogether sweeter little number.

After planning, then drilling cutting and the almost obligatory spilling of blood, I was ready to solder A to B to C; as you do.

Then, switch on and sure enough, ecc83 to el84 is very sweet but oh! what's that hum. So what I thought would be simple becomes (another ) cautionary tale.

Such very light steel and a box to boot, really resonantes nicely to what was, in a wooden or even heavier guage aluminium chassis, utter silence. This time the mains transformer hums a treat and if you pick the swet tin up, or put it on its side it doesn't hum but if you put it down, even on a deep pile carpet - HUUUUUUUMMMMMMMMMMMM. Squeeze it and it goes away. Tighthen up the bolts it gets worse, loosen them off and it is somewhat better.

The cure is to 'de-couple' but with such a weedy chassis I don't think this is achievable.

What a waste of time!

Apart from that, as you can imagine, it sounds very nice; not as sweet as the original contents of the tin, but not bad at all.

Deco-Doctor · #3 14th January 2007, 02:39 PM

Quote:

Originally Posted by andrew ivimey

HUUUUUUUMMMMMMMMMMMM. Squeeze it and it goes away

Try earth bonding twixt the tin and the lid..

Dave the bass · #4 14th January 2007, 03:09 PM

Did you find some of the 'mids' a bit soft.

DTB

andrew ivimey · #5 14th January 2007, 03:13 PM

why doesn't anyone ever want the strawberry ones?

- earth bonding? whassa' please?

(The mains transformers and the choke are bolted to the base of the tin. All the components are on the lid.)

Deco-Doctor · #6 14th January 2007, 03:24 PM

Quote:

Originally Posted by andrew ivimey

- earth bonding? whassa' please?

(The mains transformers and the choke are bolted to the base of the tin. All the components are on the lid.)

Run a piece of thick wire between the lid and the base (bolted to base and lid at each end) to ensure both are at the same potential.

andrew ivimey · #7 14th January 2007, 04:16 PM

ah, okay.

I had it down otoh as some hippy ceremony and on the other as some sort of glue.

thanks,

sleepless & witless in Bedford.

ten minutes later .... nope its just honest to badness vibratoin; not to be cured by earthing. It is interesting as, being a cheap Maplin transformer, I added another to keep the ecc83 heater happy and this is how it repays my kindness.

Ianm2 · #8 14th January 2007, 04:45 PM

I have just been examining one of thorsten's circuits, its too elaborate,clever and embellished.

Nothing wrong with showcases, but imo this is the essence of diy, simple, elegant.

nice little circuit, bit weedy on level I found, used a 6072 to drive, and triode wired, zero nfb, but as you say very good.

mine was light and euphoric sounding, strings were astounding, almost 'lit'

perhaps pentode and some nfb would've given it a bit more oommph

cute as it comes tho, lovely circuit.

shows you don't need to spend megabucks, less than Â£70?

andrew ivimey · #9 14th January 2007, 05:05 PM

About Â£70 if all new stuff Ian, yes.

- this amp is just maplin, hardwarehouse (HongKongebay for the output transformers because I didn't have any other 5-6k trafos lying around) ) and junk box stuff.

No, its the loss of time I rue. I first built this amp into a wooden box and it was fine; no hum, just a nice sounding little amplifer. Then I got cocky and drilled out more space for 807s, then added a more powerful PSU and the box was no more.

Really, I should start again with either or both, with a 'serious' expression on my face. But can I be bothered?

Deco-Doctor · #10 14th January 2007, 05:10 PM

Quote:

Originally Posted by andrew ivimey

ah, okay.

I had it down otoh as some hippy ceremony and on the other as some sort of glue.

thanks,

sleepless & witless in Bedford.

ten minutes later .... nope its just honest to badness vibratoin; not to be cured by earthing. It is interesting as, being a cheap Maplin transformer, I added another to keep the ecc83 heater happy and this is how it repays my kindness.

Ahh yes cheap M****n transformers, they do seem to excel in the supply one of the worlds loudest buzzing transformers, best to burn them on a sacrificial bonfire under the next full moon