First build...possibly a tube comp

[ljzimmer]

Hello everyone,

I have been kicking around the site most of today trying to do as much reading as I possibly can and have found some great information.  I ran across this post and I'm curious if anyone has attempted it:

http://www.diystompboxes.com/smfforum/index.php?topic=65518.0

Here is a post of the same schematic with some additional info:

http://www.diystompboxes.com/smfforum/index.php?topic=78682.0

It looks fairly simple and straight forward.

This would be my first pedal, but as a recording tech I feel very comfortable reading schematics and understanding basic electronics.  Would anyone have any hesitation trying this as a first DIY stompbox?

Thanks,

Loren

[R.G.]

Your problems will be with the mechanical and manual skills of building the boards, boxes, and then doing the soldering. I suggest you do some practicing.

I always count my first efforts in a new technology to be throwaways, a cost of the education. If they happen to be useful, so much the better. But I don't count on it.

But that's just me.

[ljzimmer]

I have some of the first tube connected.  Here is what I have:

1:  to +9v
5:  to +9v
4: to ground via 1k resistor

There is no glow...should I be concerned???

Am I doing something wrong???

I have left the other terminals of the tube unconnected to get the "basics" first.


Thanks,

Loren

[JKowalski]

I have some of the first tube connected.  Here is what I have:

1:  to +9v
5:  to +9v
4: to ground via 1k resistor

There is no glow...should I be concerned???

Am I doing something wrong???

Yes.

Pins 4 and 5 are the two ends of the heater, and pin 1 is the ends of the heaters connected together.

You need to put 12 volts across pins four and five (12 volts on one pin, ground on the other), and nothing on pin 1.

Alternatively, you can put 6 volts on pins four and five and ground on pin 1.

Those two are the standard way to set up heaters.

The way you have it set up, one of the heaters has 9 volts on both sides of it, and therefore cannot dissipate power (no voltage difference across it) and will not heat up. The other heater is conducting, but the 1k resistor is way way to big, it is not letting enough current pass through the heater.

If you want to use 9 volts, you can put 9 volts on both pins four and five, and a resistor to ground on pin 1, which is what I think you were going for. However, the resistor would have to be a ~2 watt type and be 5ohms, not 1,000 ohms.  

You should be using a 12 volt power supply, because thats:

A: More voltage for the tubes
B: a standard heater voltage value (you don't have to deal with a extra resistor dissipating power which you dont need to)

[R.G.]

J's right. You need to push 150ma through each of the heaters. This happens with 6.3V across each half of the heaters, or 12V across pins 4 and 5.

As mentioned, you can use 9V to power each half heater by connecting pin 9 to either power or ground, and then a resistor in series with pin 4 and 5 to drop 3V at 150ma. That's 3/.15 = 20 ohms each or 10 ohms for a single resistor with pins 4 and 5 connected. The power dissipated is 0.45W for the 20 ohm and 0.9W for the 10 ohm version. So you'd need either two 20 ohm/1W resistors or a single 10  ohm/2W resistor.

He's also right that it would be smarter to use 12 for a power supply to run the heaters with no external resistors.

It's quite difficult to get used to the issues with heaters if you've always used solid state.

[JKowalski]

As mentioned, you can use 9V to power each half heater by connecting pin 9 to either power or ground, and then a resistor in series with pin 4 and 5 to drop 3V at 150ma. That's 3/.15 = 20 ohms each or 10 ohms for a single resistor with pins 4 and 5 connected. The power dissipated is 0.45W for the 20 ohm and 0.9W for the 10 ohm version. So you'd need either two 20 ohm/1W resistors or a single 10  ohm/2W resistor.

Woop, you are right, I was thinking it was 300ma/600ma for series/parallel for some reason! 

[ljzimmer]

Thanks for the help.  Your right I have been used to dealing with solid state stuff so far.  I think I've got a 12v supply kicking around somewhere I'll give that a shot.

[ljzimmer]

12v worked like a champ.

So this tube thing has me thinking...Can I substitute tubes for op amps and if so how can someone point me in the direction of some information to read???

Thanks

Loren

[JKowalski]

12v worked like a champ.

So this tube thing has me thinking...Can I substitute tubes for op amps and if so how can someone point me in the direction of some information to read???

Thanks

Loren

Op amps and tubes behave completely different.

You shouldn't think of op amps as a circuit component, you should think of them as a circuit-in-a-box. They are reasonably complicated circuits formed onto a chip of silicon inside a convenient plastic package made to do certain things. If you want to see how they work (see what the schematic of the insides of an op amp look like) read up on differential amplifiers. You can make an op amp (differential amplifier) using tubes, however.

Tubes and semiconductors are not interchangeable. Field effect transistors are the closest things in the semiconductor world to tubes, but you can't just switch them out and get the same result, most of the time. There are a lot of factors to consider.

When you are designing circuits, you have to take into consideration the technologies you are using, what you have available, and the theory behind their operation. If I were designing a tube pedal, I would probably design it much differently then a semiconductor pedal that does the same type of thing.

[ljzimmer]

Op amps and tubes behave completely different.

You shouldn't think of op amps as a circuit component, you should think of them as a circuit-in-a-box. They are reasonably complicated circuits formed onto a chip of silicon inside a convenient plastic package made to do certain things. If you want to see how they work (see what the schematic of the insides of an op amp look like) read up on differential amplifiers. You can make an op amp (differential amplifier) using tubes, however.

Tubes and semiconductors are not interchangeable. Field effect transistors are the closest things in the semiconductor world to tubes, but you can't just switch them out and get the same result, most of the time. There are a lot of factors to consider.

When you are designing circuits, you have to take into consideration the technologies you are using, what you have available, and the theory behind their operation. If I were designing a tube pedal, I would probably design it much differently then a semiconductor pedal that does the same type of thing.

Wow! thanks for the insight.  That is extremely helpful.  I have a bunch of reading to do. 

Here's the next question, I would like to end up with a compressor that has a threshold and ratio controls.  My original thought was to modify a compressor circuit with op amps to use tubes instead.  Do you think that this is possible or am I heading down a road that I shouldn't be?

[petemoore]

Here's the next question, I would like to end up with a compressor that has a threshold and ratio controls.  
  I'm not sure what 'ratio' is exactly.
  My original thought was to modify a compressor circuit with op amps to use tubes instead.
  Whew...there are tube comp build around, I'd see what they're up to.
  Do you think that this is possible or am I heading down a road that I shouldn't be?
  Anything's possible, but I'd get a good hold on the PS, theory, and how comps work first so that the trouble of tube a compressor build actually has some outcome that justifies the time and other efforts put in.
  I bought a Blackfinger instead, seemed like a total bargain having 2 tubes at high voltage and nice controls etc.

[anchovie]

Here's the next question, I would like to end up with a compressor that has a threshold and ratio controls.  My original thought was to modify a compressor circuit with op amps to use tubes instead.  Do you think that this is possible or am I heading down a road that I shouldn't be?

I think that would be more of a case of "redesigning" than "modifying". Why not try building a solid-state compressor? You might like how it sounds.

Even Pete's Blackfinger has a quad op-amp underneath it's visibly-tubed hood! 

[petemoore]

  What's the quad do..pure electronic curiosity.
  Dynacomp is on the pedalboard though, the BF is nice and all, just so darned large !

[anchovie]

  What's the quad do..pure electronic curiosity.

It's makes up the the envelope follower that drives the light source for the LDRs.

[ljzimmer]

  I'm not sure what 'ratio' is exactly.

On a studio compressor there are typically 3 or 4 controls.  Threshold:  The level at which the compressor starts to work.  Ratio:  Once the threshold is crossed how much the compressor compresses the signal.  Attack: how quickly the compressor reacts.  Release:  How long the signal is affected after it the compressor is engaged (assuming it falls below the threshold).



Does anyone have any good links to how these controls work electrically?