Want to build a peavey bandit 112 redline or Randall RX120D

[J M Fahey]

Hi kin:
1) DO you have an mg15? ...  or just a leftover speaker? The MG preamp is very good, its 15W amp is louder than the small Velleman kit.
If you only have the speaker, build the kit.
2) those "12V" are nominal. As you see, it can work from 9 to 18V, power varies of course.
If you have a ready made PSU, use it. 12V (nominal) is a very common voltage, that's why I suggested getting a salvaged or second hand one.
Or you can use one of those cheap chinese "1A" multivoltage power supplies, available everywhere and often sold by street vendors.
If you use a 12VAC transformer, a bridge rectifier (or 4 diodes) and a 4700uFx25V capacitor, you will have around 16V , excellent.
Do you live in a very small town or some faraway place? Because in any reasonable size city, there *must* be some electronics suppliers; worst case mail order ones.
Post some link to electronic suppliers you have easy access too.
Maybe most of us can't read the pages (unless there is an English version too), but sure can look at pictures and labels and suggest you something.
Good luck.

[kin0]

I have an MG15 and I pretty like it's clean preamp. I don't want to use it only the speaker. I have a store (+in the web site there is no products) but the Power Supply are pretty harshy (in FX pedal some power supplies work quieter then other so I think in the amp is the same).

What about the tone mender, the switching and cooling for the whole amp (is it needed)?

Here is links to the store http://www.talmir.co.il/main_category.asp?c_id=427

http://www.talmir.co.il/main_category.asp?c_id=66

[J M Fahey]

Hey !! That store is better than I thought !!
It should be, Haifa is a very important port.
Maybe very expensive, of course, that's a different problem.
From what they have there, you can use those cheap chinese Minwa transformers.
1) 2X6V  1000MA    0202091 (12VA) Good for a 8/10 W amplifier.
Those 12VAC@1A are fine for your TDA2003 amplifier and your Shredmaster.
You'll have 16V DC main, and auxiliary 9V.
It will have less power than your MG15, but if you want to experiment and learn, it will be excellent to start, I suggest you do it.
2)  2X18V  2000MA 0202097 (72VA)
This is a serious one, good for a 50/60W amplifier, much more than what your MG15 speaker stands.
You will have +/-25V rails, an LM3886/7294 chipamp will provide up to
30W RMS into 8 ohms, and around 50W rms into 4 ohms.
If you buy an excellent and not too expensive Jensen MOD1270 in 4 ohms or 2 MOD1050 (8 ohms each) you will be LOUD, in the same class as the Bandit65, and with a heavier sound.
I suggest you build a powered box, with the 12" or 2x10" in it, and drive it from your MG.
I have made tons of powered boxes for guys who have good but small amps.
2xEL84 amps in a metal band, what were they thinking?
The MG is not bad, it only sounds "small" , because, well, it IS small.
Driving external 50W into a big box, it becomes a fire eater.
Good luck.

[kin0]

Fine I'll go with the 2x6v minwa. Is it the power supply or do I need anything else? Also you haven't answered me if the tone mender is a good clean preamp and do the amp need cooling (another heat sinks or whose fans like in computer power supply (I use one for a box).

[J M Fahey]

Hi kin
In Page 7 of http://www.vellemanusa.com/downloads/0/illustrated/illustrated_assembly_manual_k4001.pdf
you have the power supply: transformer, diode bridge and 2200x25 capacitor.
I suggest 4700 x 25 for better filtering.
You can buy everything at your supplier.
The TDA2003 needs a small heat sink.
If you buy the Velleman kit, Im *think* it includes the heat sink; if it does not, bolt it to a piece of aluminum which in turn gets bolted to the chassis.
¿Clean preamp? I don't like the tone mender very much, I do like the one used in Rod Elliott's Project27

but it needs a split supply, easy to get in larger amps but not in the TDA2003.
Really you do not even *need* a clean preamp there, try your guitar straight in the TDA2003 as on page 8 and 9 of the assembly manual.

[kin0]

NVM I think I still will go with tone mender. My last question is how to get a 9v- from the same supply that goes to the power amp? Oh and how can I built a regular channel switch+foot switch that I will connect to a jack (but at least for this project it is optional)

[J M Fahey]

Hi kin.
If you look at the tonemender schematic and Rod Elliott's (draw them side by side on the same (large) sheet of paper), you'll see that they are practically the same, (Op Amp -> Tone control -> Op Amp) with the big difference that in Rod's the first one does provide some gain (15x) *and* switchable Bright control, then passive tone control, which you might consider having a 10x loss, and then a second Op Amp, again with 15x gain. This is a professionally designed preamp, equivalent to what you'll find on most commercial  guitar amps.
In Tonemender, the first Op amp has no gain (1x) , it's set as a buffer, then it passes through the passive tone control, where it is attenuated to 1/10th its  original value, becoming very weak, and then it's strongly amplified (100x) by the 2nd Op Amp, together with internal noise plus any hum or interference it may pick along the way.
This is an amateurish design, the kind you'll often find in non-professional Forums, hardly on Commercial products.
Mind you, *both* will probably seem to have the "same result" ... in simulation ....
In real world design, along the way you must try to keep your signal between certain limits: not so high as to clip, not so,low as to having to pay the penalty of hiss and hum when recovering.
Careful grounding, filtering and shielding can take care of hum, but noise is built-in , we must avoid getting it into our signal.
Being so similar, probably the tonemender board design can be modified somewhat to accomodate Rod's .
Google "zener regulated supply" to see how they work and how to get regulated 9V from an unregulated 16V supply.
Go step by step, build the basic amplifier first, plug your guitar straight into it, enjoy, feel proud (you deserve it), show it to everybody, then go the next step.
My first amplifier was a Class A, 2W single transistor power amp, the kind used in car radios way back then (1968), I was 15 y.o.
In 1969 I built my first guitar amp, a 4 or 5W Gibson GA5 , 1 12AX7 + 1 6V6. 1 jack, 1 volume control, on/off switch.
Boy, was I proud !!!
Then took the plunge and built a point to point wired (no board) Fender Bassman clone, later an Ampeg BT15 clone, fully on Veroboard, and so on.
Just don't hurry too much and enjoy along the way.
Good luck.

[kin0]

Okay so I'll leave the tone mender Idea and maybe later add a tone controls to the clean channel : ). Thanks for help.


I looked for the zenner regulated supply but haven't found any thing that tells me how to design it or how to make it -. Only what it does.

[J M Fahey]

http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

[kin0]

Vsource is the input in volts (16v) right? And I have no idea how much mA the shredmaster uses how can I check it before building it.

[J M Fahey]

Hi kin.
Step by step:
1) Google TL072 datasheet . You'll get:
2) http://www.datasheetcatalog.com/datasheets_pdf/T/L/0/7/TL072.shtml
3) you choose anyone there. I chose the ST one, because it's smaller:
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXrxvrt.pdf
4) there, on the "electrical characteristics" table, I see:
Icc (supply current per amp, no load)= 1.4mA typical , 2.5mA maximum.
Just for safety I assume I may get a "hungry" Op Amp, so I take 2.5mA.
I have 4 OpAmps( 2 per package) so my pedal will eat, 4x2.5mA= 10 mA. I add 5mA so the Zener passes some current, or it will not "Zene", as Enzo would say, I will calculate for 15mA consumption.
I will also consider that on loud volume the supply "raw" voltage will drop, after all it's not regulated at all.
Don't know how much and lack some data for calculation, but from previous experience to consider a loss of 2V is reasonable, so I consider I'll have 14V when loud.
5) The voltage dropping resistor will be: (14V-9V)/0.015A=5V/0.015A=330 ohms.
330 ohms is a standard value.
What power dissipation should it support?: 5Vx0.015A=0.075W so a 1/4W one will be more than enough.
6) How much will the zener dissipate if I have power "on" but pull the distortion board out for any reason? (as to tweak it): 9Vx.015A= 0.135W. A 1/2W Zener will do nicely.
In actual use it will dissipate much less, because most of the current will be absorbed by the 2 TL072.
7) What if I add , say, a clean channel with 1 TL072?: calculate adding 2x2.5mA extra, for a total consumption of 20mA.
If the LED is fed from the 9V, add its consumption too; personally I would feed it straight5 from the 16V unregulated.
Good luck and please re-do calculations yourself, so you can use this knowledge in other, future projects.
Good luck.

[kin0]

Okay, I finally got all the parts except the fuse. I just can't find one in my country. Can I use other fuses or just this? Are this good http://cgi.ebay.com/T1A-1A-20mm-5mm-Slow-Blow-Fuses-250V-RoHS-UL-VDE-x-10-/?250488788457?pt=BI_Electrical_Equipment_Tools&hash=item3a524b95e9?

[J M Fahey]

Hi kin.
I understand you are building the TDA2003 power amplifier plus a couple 9V pedals as preamps.
Since you have 220V, use the 500mA fuse (not 1A) that your supplier carries, the most common one.
Don't worry about slow, fast, timed, whatever, just what's available.

[kin0]

The transformer have 5 wires while there is only 4 in the drawing in the instructions. It has 2 red, 1 white and 2 black. Which goes where?
here is the pic of the parts that I don't know how to connect.


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[J M Fahey]

Does the transformer have any labels? Where? What do they say?
Measure the DC resistance Black/Black; Red/Red/ amd both Grey/Red
Remember to short your test probes and substract that value from the reading.