Hi:

I thinking about what kind of use break shaft of knob. Maybe clean volumen knob is not good condition too.

If you planning to repair it yourself, need to take out the knob broken, so you can see its value, and check clean vol knob too.

Look around the metal part of the knob, and you´ll see a value like "100KA" or "250KB" or something like that.

First part, are the knob (potentiometer) value, ie 100K, last letter is what kind, so, A is Audio Type or Logaritmic, B is Lineal Type.

I guess that any decent electronic supply store can sell you a couple of potentiometers.

For those old dogs that bark in spanish,  and are looking for new tricks, here Kicad tutorial
http://www.aclibre.org/archives/KiCad-es.pdf

Hi:

By the way, this de-soldering pump is very usefull.  Cheap and reliable.


While desoldering component of PCB, be carefull of dont heat so much the tracks, just enough heat to smelt the tin. They lift up very easyly.

Quote from: RubberSalt on November 28, 2011, 11:41:24 AM...
It seems my lm386 builds might actually be louder. Both are equally clean I'd say.....

May ask you: are you using the same speaker for compare LM386 vs TDA2003?

Ha, ha..... if you want, i can send you for free, some samples of ash... so you can do your "Fahey Vulcano Edition" amp with samples of them inside!!!  :lmao:

Quote from: J M Fahey on November 22, 2011, 08:01:12 AM
As the Genius in the Lamp said: you have just spent one of your 3 questions.

so... i do not more questions? or... need a new lamp?.. just joke...

I guess that i need do my homework and found for my old Malvino "Principios de electronica"


thanks for your big help.

Thanks JM, so im ok.

One more, about zener... can you help me?

I returned back to work in my last project.

I trying to mount kinda of a JCM900 1x12 combo clone (at least, its format).

Using a gainclone as amp, and a Sansamps as preamp.

Worked fine assembled on the table, but still rest to resolve some "detailed engineering", and mount all together inside cabinet, and that work well for some jam in a bar.

First one, mounted all stuff, and potentiometers cable are soldered straight to SanAmpClone PCB. Tracks are very thin, so soon they lifted up as moved the pcb to test it. Using dead pc power supply cables. Very nice cables, several colors to choose, as you can see in pictures.

What work best? Do a simple pcb to mount potentiometers, and wire that pcb to sansamps pcb? O put some terminal/screw or something like that in sa pcb?

Second one: SansClone works with 9V. For try it used a cheap multiple voltage supply, but now, i need to resolve its feed inside of cabinet.
Ideas are: use another trafo with its rectifiers and 7809 (JM says dont like it, in addition, i think that will need to couple its 4,5v with 0V of LM3886): Or use zeners. I need to feed it with 34V and put out of them 9V, with i guess about 200ma for feed SansAmp. Calculed a 25V of drop with 200ma. Ill need to use a 120 ohms resistor with 5W of power disipation? Am i right?

Here a couple of picture....

Can you suggest some ideas? Beside, feel free to improve my english 

Quote from: Alexius II on November 13, 2011, 05:04:39 AM
Interesting read. I've built a TDA2003 a while back and it was absolutely noiseless and did not distort with just guitar at the input. Maybe your pickups have much more output... or maybe my 18V supply helped with the headroom.

It's a really nice chipamp for bedroom-practice (with some nice preamp/pedals) :tu:

I remember that i made a tda2003 circuit like datasheet, at secondary school, a lot of years ago.... Just plugging guitar at the input, and it has very low (VERY) volume at the speaker. So i put the higher resistor that i found then. (1M5) in parallel with the input (raising up input impedance), more guitar signal get into amplifier. Worked better like that. Anyway, our friend should use his lm386 as a preamp for better result.

Quote from: J M Fahey on August 01, 2011, 01:42:44 PM
If you build a split supply LM1875 amp (or any other split supply chip amp, which means *all* of them over 15W), you can easily pull +/-15V out of them for your Marshall preamps.
And from one of them you can also easily pull +9V for your Boogeyman or whatever.
You can have your cake and eat it 

I thinking about this since a long time. How you can do that? Maybe a voltage divider? LM7815 a LM7915  is other way, but datasheet of these says that no more of 23V of input for sure..... What you think?

Hi RubberSalt:

May i suggest that use your TDA2005, and go straight forward to its datasheet and make the bridged suggested circuit. It work very well with 12V, even without any preamp. Plus, very low component count needed.

Besides, you can (i do it too) use your ruby as a preamp and work fine too  :tu: . I dont know what version of ruby are you using, but if you use this (http://www.runoffgroove.com/ruby.html), you´ll have a nice 12V amp.

Silly question:

Why cant i use some piece of steel framing (steel galvanized) as heatsink? I have a lot of pieces of them, and it comes in several sizes...

It´s a great stuff this bulb. Saves me (at least) several fuses today. :tu: . I see trouble for it at future.... no more regular bulb in our country, ..just compact fluorescent lamp...

J M;  YOU ARE THE MAN!!!!   :dbtu:

I had readed your bulb and speaker suggestion after do my tests.

I checked again the datasheet and ggg schematics, and you are right!!!

I confused putting the capacitors. Negative pole of electrolytic, always at most negative tension. Using now  2x new 1000uf /63V.

I try replacing speaker of coihue micro (aka ruby with big muff control tone) with lm3886 input and trip like a charm  :dbtu:  :tu:   ( Guitar-> CoihueMicro->Lm3886 input)


Thank you a lot!!!!!

PS: Next step! SansAmps GT2 clone as a preamp!

Now connected a 75W limiter bulb. Using 2A fuse for each rail.

No heatshink attached (just for test ). I did next tests:

1- Power amp stage disconnected from power supply. Turn MAIN switch on. +33.5V, 0, -33.5V at rails. Bulb is OFF.

2- Now connected power stage at supply. Using 8ohm-80W "FAHEY" Speaker. MUTE switch OPEN. Turned MAIN ON. -8,5V at VCC- and 9V at VCC+. Bulb is ON. Turned MAIN off.

3. Now using cheap 8 ohm, W, speaker. Mute switch CLOSE (ON). Turned MAIN ON.  -8,5V at VCC- and 9V at VCC+. Bulb is ON. Turned MAIN off. As result of this C5 (2200uf/63V) get is head a few inflated, and somewhat hot.

No more 2200/63V caps at hand, so i planning to pull them (c5 and c6) off of pcb, and retry. Perhaps c5 in short? It was new brand one. I thinking to pull them out cause i see that them are in parallel with the power supply ones (my supply has 2x4700uf for each rail), so ¿with them are enough filter caps?

I checked the pcb again and nothing seems wrong. At first test yesterday, as i say, PIN11 was wrong joined with VCC - . Datasheet says that PIN 11 is NotConnected. Anyway, the chip can blow for this?

Attached picture from power supply, and back of amp pcb.