a few simple questions from a new builder.

[Capacitordeath]

Hi again.

First of all, let me say that the responses to my posts have been heartening. Everyone seems pretty excited and informative on this forum, and willing to converse.

All right, so here's a few more questions to lay out there.

1: I've read that, as far as multimeters go, I'll need one that reads up to 500V. It's a bit cloudy on how low it should go. Will the run-of-the-mill MMs I can pick up at Home Depot work, or do they need to be a bit more fine tuned?

2: I'm making one of those capacitor dischargers, but I think I bought too small of a resistor. I bought a 2 pack of 1000/1watt. Now that I've found some articles on the subject, it looks like this may not be enough resistance to slow the discharge appreciably. As I am not planning on reusing any of these caps, I'm not too worried, but I don't want any crazy fireworks. How about the 2 resistors soldered in series, than heat-shrinked?

3: I'm making an amp with a tweed bandmaster circuit, but I have no interest in making a "Bandmaster", including an amp with 4 inputs for one guitar player (me). This will probably seem like a dumb question, but could I just take three inputs out of the equation? I see that on the schematic, some inputs have a small cap or resistor (which I will make sure of before I start soldering) on it, which I assume would be the "bright" channel. Would making this amp a single-input with a switchable bright seem out of the question? Basically, just add a small toggle switch to the side?

4: 6v6 power tubes and 6l6 family power tubes are, or are not, interchangeable? Apparently the 6l6 tube and the 7027a tube are fairly interchangeable with a smidgen of wiring difference. I've heard again and again that 6v6 tubes are warmer sounding, and that's whadIwann.

5: Is there a preferable gauge wire to use over another? I have some pretty thin stuff that I was using on a guitar project, but I can see this stuff burning up quickly.

There we go. Thanks ahead of time for the answers.

[tubeswell]

1: I've read that, as far as multimeters go, I'll need one that reads up to 500V. It's a bit cloudy on how low it should go. Will the run-of-the-mill MMs I can pick up at Home Depot work, or do they need to be a bit more fine tuned?

Anything with an adjustable scale that can read both mV, a few tens of V, hundreds of volts, and up to 1kV or so. Same goes for ohms and amps. Most MMs will do this. If you can get one that reads farads, that is a bonus - make sure it can read pF, nF and uF scale

2: I'm making one of those capacitor dischargers, but I think I bought too small of a resistor. I bought a 2 pack of 1000/1watt. Now that I've found some articles on the subject, it looks like this may not be enough resistance to slow the discharge appreciably. As I am not planning on reusing any of these caps, I'm not too worried, but I don't want any crazy fireworks. How about the 2 resistors soldered in series, than heat-shrinked?

If you want to put in permanent bleeder resistors, something around 200k 2W will work. (or 2 x 470k 1W in parallel for each filter cap)

3: I'm making an amp with a tweed bandmaster circuit, but I have no interest in making a "Bandmaster", including an amp with 4 inputs for one guitar player (me). This will probably seem like a dumb question, but could I just take three inputs out of the equation? I see that on the schematic, some inputs have a small cap or resistor (which I will make sure of before I start soldering) on it, which I assume would be the "bright" channel. Would making this amp a single-input with a switchable bright seem out of the question? Basically, just add a small toggle switch to the side?

Yep you can. Just use a 33k resistor where you would normally see a 68k. The 1M to ground stays put

4: 6v6 power tubes and 6l6 family power tubes are, or are not, interchangeable? Apparently the 6l6 tube and the 7027a tube are fairly interchangeable with a smidgen of wiring difference. I've heard again and again that 6v6 tubes are warmer sounding, and that's whadIwann.

6V6s and 6L6CG have different load resistance requirements, different bias operating points, and draw different amounts of heater current. Provided that your PT windings and OT are designed for it, you can build an amp that can take either. But you will likely have to accept compromises (the OT will sound better with 6L6s if it is bigger - but that will make operation with the 6V6s very clean and full - not that this is a 'bad thing'. The OT will also have to have several secondary taps to allow you to change the load resistance easily, but they may not get you 'ideal' operation with both types, unless you get an OT that is custom wound to particular specs. Also you will probably want to have a 3A 5V winding for the rectumfrier, for a range of tubes that allow you to more easily obtain different B+ voltages when you are using the different output tubes). The 5e7 is a fixed bias amp, so for that amp you would have to build in a bias adjustment pot. And for safe operation a couple of bias test points would be a good idea so that you can safely re-bias it when you swap tube types.

5: Is there a preferable gauge wire to use over another? I have some pretty thin stuff that I was using on a guitar project, but I can see this stuff burning up quickly.

I use 20-24g multi-stranded wire for most of the wiring, but 18-20g for the heater filaments because these wires carry more current. Other peeps use different types/thicknesses.

[RogerWilco99]

nevermind...

[Capacitordeath]

woo...awesome reply, thanks. I'm not quite sure how to do some of the stuff you mentioned, but I'm sure I'll be able to snoop it out online in no time. Gotta love bookmarking! Chances are, since this will be my first amp build, and basically my first electronics project....and I'm also going off script in several spots (effects loop + some or all of this stuff HomeBrew Tweaks - AMPS! probably leave off the tube-swapping BS until maybe amp #2. I should probably leave all the BS in the parentheses until amp # 2 as well, and make a straight in-straight out amp with a knob or two and a couple of toggle switches, and a couple of alnico speakers on the other end.

but I won't! NO I WON'T! HAHAHAHAHAH!

anyway, thanks again.

[Enzo]

tubes gave some good advice, but i am not sure he directly answered some of what you asked. Here's my take on it.

SInce tube amps use voltages up to 500v or even more, you need a meter that won't go nuts if you connect it to such voltages. The spec sheet or owners manual of any meter will tell you the maximum voltages it can withstand. You don;t have to spend $400 for a good meter, but a $5 meter is a cheap meter, even if it seems to work. Accuracy and reliability are not too important to someone making $5 meters to sell.

A 1000 ohm resistor is fine for discharging caps. 200k resistors are fine for bleeders in the circuit, because they not only discharge the cap, they also have to not draw a lot of current while it is running. But they are darn slow if you are trying to discharge a cap with them. 1000 ohms is high enough it won;t melt the wires or damage the caps, and low enough it won;t take all evening.