Building the housing

Dajgoro · Post by **Dajgoro** » Sat May 26, 2012 10:35 pm

I found a guy who makes all kinds of stuff, i initially ordered audio and power transformers for my EL34 amplifier that i am building (i went to using tubes, because i had bad luck with transistors, and my friend had bad luck with ic amplifiers, and when i tried with tubes, it worked on the first try).
Anyway the guy also makes chassis, housings and all kind of stuff, so i asked him to make a custom housing for my sbc, in which i could fit the expansion board, crtc board, power supply,ect... , and i couldn't resist not having blinkenlights. I got the box, already painted, but i had to drill all the holes myself. The paint started to get off, so i had to repaint it, after few attempts, i finally painted it successfully.
Now before i start mounting switches and leds on the front panel, i need to somehow paint the marks, labels, and stuff, i don't want a blank front panel. I thought about making a mask, and then using a white spray, but i am not sure how would this end up. I could also stick transparent labels, but i don't know where to find someone who would stamp them for me, and how would it look like in the end. Do you have suggestions on how to make the labels and marks for the front panel?

BigDumbDinosaur · Post by **BigDumbDinosaur** » Sat May 26, 2012 11:54 pm

Dajgoro wrote:

...so i asked him to make a custom housing for my sbc, in which i could fit the expansion board, crtc board, power supply,ect... , and i couldn't resist not having blinkenlights...Do you have suggestions on how to make the labels and marks for the front panel?

If the paint is a light color you could use dry transfers for lettering, although getting it to line up would be an exercise in patience. I would use transparent stick-on labels that can be put into an ink jet or laser printer (the latter would be better). The lettering will line up just so, you can use whatever font you think is appropriate and once stuck to the panel, the labels will blend in with the background.

GARTHWILSON · Post by **GARTHWILSON** » Sun May 27, 2012 5:22 am

Use transfer (rub-on) lettering. Black is most common, but I've gotten white too at an art supply, and I think I've seen other colors. I put a clear coating over that to keep it from flaking off. As you can see, the coating has turned somewhat yellow; but it's almost 35 years old!

As far as transistor and IC audio amps go, how much power do you need and what have you tried?

Dajgoro · Post by **Dajgoro** » Sun May 27, 2012 3:53 pm

I really like your rub-on suggestion, if you could explain the process a bit more.

Off-topic:
As for my amplifiers (I am not an expert in the field), i would not dare to go over 10W per channel, since the old speakers(10W old EI Niš) that i have would blow. First i tried with AD161 transistors, as i don't like to make things from schematics(kida cheating), i went to thinker, but i just couldn't get them to work on full power. As for ic, my friend is kinda obsessed with TDA ic, and i can't count anymore how much times they have blown up in his amplifier. At the end i found an old radio on my attic, and i took it apart, and i built a simple amplifier with the EL84 tube, and it just worked, after that, i took apart another radio(all of them being from EI Niš) and i took the transformers, and the rectifying tube. In no time i had a new amplifier built from old components, and it's been almost 2 years, and i use it almost 24/7 and it still works. But EL84 tubes in single ended mode don't offer much power, so i went and bought EL34 tubes, transformers, i recently bought two fancy vu meters, i just need to figure out the chassis and put it all together, also i will try not to make some mistakes that i made in the current version.

Before I've went into building amps, i had a simple amp that i built with AC187 transistors for my headphones, and when listening to music from my pc sound card, it would generate a sort of richer sound, until one day i accidentally made a short circuit, and blew all the transistors...

Since i am building a sound module(i plan to) for my sbc, i was planning to add a small preamp, but i haven't decided how should i build it, should i use germanium(fancy

), silicon, or just put an lm386...

GARTHWILSON · Post by **GARTHWILSON** » Sun May 27, 2012 7:30 pm

The rub-on lettering comes in transparent sheets so you can see the surface behind to position the letter exactly, then just go over it with something like a dry ball-point pen, without moving the sheet, until the entire letter is transferred. The first thing that came to mind is to pull out a sheet and take a picture to post, but it has been so many years since I've used it that I can't remember where I have them stored anymore.

Many IC amplifiers will have thermal shutdown, SOA protection, etc., so they should be difficult to damage by shorting or overheating. We've used tens of thousands of LM386's and thousands of LM380's (without a single failure—ever!) but nothing that would deliver 10W although there are others in that family that will, and their distortion will be considerably lower than what you could build with discrete components. Keep in mind that germanium does not last indefinitely like silicon does if you don't keep it running too hot.

BigEd · Post by **BigEd** » Sun May 27, 2012 8:17 pm

In my day we called it Letraset - whether it always was, or whether that had become a generic term, I don't know.
http://www.letraset.com/products/91-Lettering/
("Dry Transfer Lettering" seems to be the approved term)

GARTHWILSON · Post by **GARTHWILSON** » Sun May 27, 2012 8:29 pm

Ah yes, that's it. Thanks for the name and the link.

Dajgoro · Post by **Dajgoro** » Mon May 28, 2012 1:09 am

I painted the housing in black, so i need white letters.
Could this work: http://www.ebay.com/itm/Letraset-dry-tr ... 19d09b5e90
3/16" is about 5mm if i am right...

GARTHWILSON · Post by **GARTHWILSON** » Mon May 28, 2012 4:36 am

Looks good.—3/16" is about 4.76mm.

BigEd · Post by **BigEd** » Mon May 28, 2012 4:47 am

Also these (taller, less wide, from a UK seller)
http://goo.gl/4iWRM

Nightmaretony · Post by **Nightmaretony** » Mon May 28, 2012 4:53 am

TDA2003. 8 watts mono.

BitWise · Post by **BitWise** » Mon May 28, 2012 7:32 am

I'm disappointed that the numbering on your amp doesn't go up to 11.

BigDumbDinosaur · Post by **BigDumbDinosaur** » Mon May 28, 2012 8:15 pm

BitWise wrote:

I'm disappointed that the numbering on your amp doesn't go up to 11.

Only 11??? Mine goes up to 20! Just kidding!

I do have a Dynaco Stereo 400 power amp I built in 1974 that really does produce 200 watts RMS per channel with better than average (for solid state amps) clarity and transparency. The Dynaco unit replaced my two custom designed 100 watt tube amps (one per channel, using the Sylvania 8417 beam-power tetrode, the ne plus ultra of audio amp power tubes). I "lent" the tube amps to a friend who needed a stereo but was not able to afford a high quality system. The Dynaco unit has worked so well I've stuck with it to this day (along with my Dynaco PAT4 preamp—another model of great engineering).

Dynaco was a very interesting company. It was founded by David Hafler in the 1950s and built its reputation on high performance components that could be purchased factory-assembled, or built by anyone with reasonable skill, meaning you had to know how to solder and do clean point-to-point wiring. Hafler went on to form another company that specialized in top-of-the-line audio. Another friend of mine has an entire system built up with Hafler components. I'd have to say the preamp, power amp, etc., are all works of audio art, and are utterly reliable.

BTW, I may yet switch back to tube amplification for my stereo. Solid state amps have a "stiffness" to them that tends to make the sound a bit too dry for my liking. You'd understand if you could hear side-by-side comparisons. Also, my work over the last 10 years on tube-powered instrument amps has whetted my appetite to step way back in time. Plus tube amps are a great thing to have around in the winter—they cut down on your heating bills.

Dajgoro · Post by **Dajgoro** » Mon May 28, 2012 8:20 pm

BigEd wrote:

Also these (taller, less wide, from a UK seller)
http://goo.gl/4iWRM

7mm letters are a bit too big...

Nightmaretony wrote:

TDA2003. 8 watts mono.

I've built an 3 channel mixer/amplifier using them in my 7.th grade (elementary school with 8 grades), and i had issues with interfacing the preamp with the tda2003. Later i gave it to my friend.

As for the rub on method, i just take the sticker and apply it on the housing with pressure, and then i remove it and the letter is there permanently, or what?

My only concern with tube amps are flying objects, that occur here and there, especially when there is a party, since the protective cage is kinda expensive, i don't have it...

Dajgoro · Post by **Dajgoro** » Mon May 28, 2012 11:23 pm

I bought the letraset from ebay.

Extremely off-topic:
I apologize for this extremely off topic post, but i kinda don't know who else to ask...

I am wondering which tubes should i buy for the preamp stage, i need some ECC82, but which one are good? Ebay gives me this choice: http://www.ebay.com/sch/i.html?_nkw=ecc ... &_osacat=0
My budget is kinda limited to the first half of the page...

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