"PentaBoost" - 12 volt Pentode Booster using Submini 5672 tube

[svstee]

OK, I used double sided foam tape on both sides of the pot and the switch. Huge improvment, but still not great. I'm gonna run short leads from the pot to the circuit and see if that helps. Another idea and a couple questions.
1: How hard would it be to run an AA battery to the heater and 18-24v from a wall wart to the rest?
2: How long would the battery last?
3: Would a C or D be better?
4: What would the best way to hook it up be?
5: Would it be worth it to run it to an spst as a "power on/heater on" switch?

Thanks!

[Renegadrian]

svstee - here's my pentaboost - altough it works ok with a 9v battery, I have to report a really nice use of my voltage multilier, so I tried running it at 50V - that was a good one!!!

Here's my version...



After I successfully breadboarded it, decided to draw a vero layout by myself, now in my gallery,
and decided to build and box it somehow...Found a little wooden box at Leroy Merlin while shopping
for spray cans, so I thought "WHY NOT?!" 
So here it is...It uses a 5678 tube and it's powered by a 9V and a 1.5V AAA for the heaters.

[svstee]

Nice, how did you wire to the cell? Did you just solder right on to it? I see what you did with the stereo jack, but I like to leave all my pedals plugged in, so I think I'll just run - through an spst toggle.

[svstee]

Well, after getting sick of the microphonics I switched out the tube for another one, NOS, right out of the box. same problem, hardly any better. I'm using foam, rubber washers, and foam tape and am still not having much luck. It really sucks because this circuit sounds GOOD, especially in front of my FF and TS.

[Berger]

What are the requirements for the pentode. I picked up a couple submini 5639 pentodes, and all I've been able to get out of them is some ticking. I was wondering if this pentode is too different to work in this setup?

-Berger

[frequencycentral]

What are the requirements for the pentode. I picked up a couple submini 5639 pentodes, and all I've been able to get out of them is some ticking. I was wondering if this pentode is too different to work in this setup?

-Berger

It should be possible to make a similar circuit with the 5639. have a look at the data sheet:

http://frank.pocnet.net/sheets/087/5/5639.pdf

How have you got it set up specifically?

[Berger]

i used the penaboost schematic and just used the corresponding pins.

I used:
pin 1(Grid #1)
pin 5(Plate)
pin 7(Grid #2)
and the heater connections on pin 3 and 6.

Thanks for the quick response!
-Berger

[frequencycentral]

Let me have a look at it and come back to you tomorrow.

[frequencycentral]

i used the penaboost schematic and just used the corresponding pins.

I used:
pin 1(Grid #1)
pin 5(Plate)
pin 7(Grid #2)
and the heater connections on pin 3 and 6.

Thanks for the quick response!
-Berger

This tube has a seperate cathode which you need to connect. In the 5672 the cathode is internally connected to the heater +ve. So I think you'll need a connection to either of pins 2, 4 or 8, which are all the cathode. You could try referencing it to ground with a low value resistor paralleled with an electo cap, try 1K and 10uf for starters.

I'm assuming you're giving the heater 6.3v ?

[Berger]

That worked! Yup supplying it 6.3 volts. I really like the sound of this. i hopefully will have the 5672s coming in as well, I'm a big fan of the Trotsky drive and am looking to build the red-star drive that you made like it.

Thanks for the quick replies and the help!

-Berger

[frequencycentral]

That worked! Yup supplying it 6.3 volts. I really like the sound of this. i hopefully will have the 5672s coming in as well, I'm a big fan of the Trotsky drive and am looking to build the red-star drive that you made like it.

Thanks for the quick replies and the help!

-Berger

Hey that's cool! Excellent, well done! You should be able to just hang a couple of mixed Ge/Si diodes off the output of your 5639 to make it into a Red Star Drive. Also check out the Deliruim 5672 tremolo thread, you should be able to do that too with the 5639. Is the 5639 microphonic at all?

[Berger]

I have the leads at about 1.5-2" and its not monophonic. I really like this since it uses the 6.3v heaters, much like the other mini tubes I've been using.
I'll look at the Deliruim 5672 tremolo thread, should be fun. I can always use more tubes on my pedal board.

I'm also playing around with a 6U10 triple triode tube, it just sounds like fun.

-Berger

[Magnus]

Hello together,
I am working on a layout to build the PentaBoost MkII,
but there are two points where I am not sure if everything is allright,
would be nice to know if the Voltage-Regulator LM317T is wired exactly
and the trim-potentiometer too (maybee I have to connect two pins of the trimpot?)



I know the layout is not ready yet, the Volume-Potentiometer,
the jacks, the switch and the dc-jack are missing,
I will update everything after I know the things explained/asked above  

Thank you!


Greetings from Germany
Magnus

[Magnus]

Hello,
can anyone help me?

(post above)


Greetings
Magnus

[blackcorvo]

It should be possible to make a similar circuit with the 5639. have a look at the data sheet:

http://frank.pocnet.net/sheets/087/5/5639.pdf

That looks like a tube you could use for a small tube amp design.

I know, "yet 'nother submini amp idea"... but I think this one could make some serious noise from what I see in the datasheet. Maybe you could get something like 1/2w from it in SE at 150v, maybe 2w in PP, I'm just guessing.

It just really sucks that I can't get any of these little tiny tubes. There's only one place here that sells these, but they ask for more than 100 bucks for them, so... no deal. And I don't have a paypal or a credit card, so I can't really buy anything from e-bay.
Otherwise, I'd be making some crazy stuff with these babies. SRPP boosters (trying combinations with 2 pentodes, or "pentode-bottom/transistor-top" and stuff, to see what I can get), distortion boxes, wah wah... anything. Ideas are always flowing from my mind.

[Ratbones]

I've got this breadboarded and I've got no output at all...
I'm using an lm317 and 7812 for regulation and I'm getting 1.26 to the heater and ~ 11.8 - 11.9 volts from the 7812.

my pin voltage readout is as follows:
1 ~ 1.37v
2 ~ 4.16v
3 -  1.26v steady
4 ~ 0v
5 ~ 0v

I'm not sure why the voltage to pins one and two are so low... I've got 100k resistors between v+ and the pins as the schem suggests... Any ideas?

[frequencycentral]

0v at pin 4 - that's the input. Doesn't seem right. How is the input grounded?

[Ratbones]

Ah, I guess when I got readings I had the guitar unplugged... I'll check again with it plugged in.  Is there a reason that pins one and two would be seeing low voltage?

[frequencycentral]

Sure you've got the tube the right way round? The red dot is at pin 1. Have you followed the schematic exactly? 1uF cap from pin 2 to ground even?

[Ratbones]

I'm pretty sure everything is exact, but I may just pull everything and breadboard it over while highlighting the schematic just to be sure. I'll post back with my results