ZH Boost - subminiature tube booster

Stompboxes circuits published in magazines, books or on DIY electronics websites.

ZH Boost - subminiature tube booster

Postby himister » 17 Oct 2009, 14:52

One of the experimental attempts to use Russian sub-mini pentode 1ZH18B (1Ж18Б) turn out odd and simple but quite good.
It's nice clean boost but also could be use as a simple OD pedal, with some tweaking of course.
I experimented on it and you'll see that tube is connected in rather unusual way. Main thing that this pedal needs is good filtered DC and it turns out that DC filtering needs almost more components then signal path passives.
I used 9VAC 1000mA wall wart to be on safe side, smaller current source would make some trouble.
I must say nothing new, nothing so "original" but it could be useful if anyone can obtain these sub-mini's.
To be honest, did some research and been inspired by some previous designs like PentaBoost by Rick Holt "FC".
kudos Rick :thumbsup
Some would say it's almost identical, but I hope in some way it's different just a bit. :D

As I saw on the net these subs are quite cheap, something bellow 2$...correct me if I'm wrong.
Right now I'm working on the pcb that could be put in Eddystone 27969PSLA 'cause they are obtainable here in my place for about 6eu.

I hope some of you will enjoy this one. :wink:

Schematic Ver.1.0:

ZHBoost.gif

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ZHBencldes.gif
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 17 Oct 2009, 15:00

:D Nice to see a design using these Russian tubes! I'm going out shoppoing now, but I have a few ideas to put forward when I get back.
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Re: ZH Boost - subminiature tube booster

Postby himister » 17 Oct 2009, 15:06

frequencycentral wrote::D Nice to see a design using these Russian tubes! I'm going out shoppoing now, but I have a few ideas to put forward when I get back.


Thanks Rick. :wink:
I also have couple more ideas but some testing needs to be done so I'll put it here when it's finished.
Cheers.
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 17 Oct 2009, 18:25

A couple of suggestions:

As we know, tubes will give a bigger boost if you feed them more volts, and also sound sweeter. As you are running on 9 volts AC you could easily add a tube amp style voltage doubler before the rectifier. Just two diodes and two caps should get you up to 18 volts before rectification.

The LM317 is a very precise way to get 1.25 volts for the heater. But you could save a few parts (and a heatsink for the 317) by just using a suitable voltage drop resistor from your rectified DC. As to the ohmage/wattage of the resistor, that would depend on what your DC voltage is after the voltage doubler (if you take up my suggestion) and the rectifier, and how many milliamps the tube draws at 1.25v.
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Re: ZH Boost - subminiature tube booster

Postby himister » 17 Oct 2009, 18:49

frequencycentral wrote:A couple of suggestions:

As we know, tubes will give a bigger boost if you feed them more volts, and also sound sweeter. As you are running on 9 volts AC you could easily add a tube amp style voltage doubler before the rectifier. Just two diodes and two caps should get you up to 18 volts before rectification.

The LM317 is a very precise way to get 1.25 volts for the heater. But you could save a few parts (and a heatsink for the 317) by just using a suitable voltage drop resistor from your rectified DC. As to the ohmage/wattage of the resistor, that would depend on what your DC voltage is after the voltage doubler (if you take up my suggestion) and the rectifier, and how many milliamps the tube draws at 1.25v.



Good idea.
The reason I made this way was to filter the DC much as I can, and eliminate the hum from the supply. Also odd thing was that heaters of the tube wouldn't work with 9VDC 300mA wall wart through LM317T (new-unused). I've looked at the datasheet (included below) and it says that tube needs 0.021-0.026A to work properly... :hmmm:
I picked 9VAC 1A wall wart and rectified like on schematic and even put 7812 reg for extra filtering before LM317 :slap: and heaters were good. Everything was ok.
I changed anode resistor for a trim pot so I could eliminate distortion and made it cleaner.
One more thing that I have in mind is to use a hex-inverting buffer (4049) supply so I could raise the anode voltage to almost 60V which is the limiting value for the tube but didn't get to this yet, and I think it would be too much for this size of enclosure.
I'll try few tweaks and what you proposed and inform here accordingly.
If anyone else tries this I would like to hear their experience.

Thanks Rick. :wink:

1ZH18B Datasheet:
1Zh18B.pdf
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Re: ZH Boost - subminiature tube booster

Postby kurtlives » 18 Oct 2009, 16:40

Why do you have the screen at a higher potential than the plate? I always thought that was a no no.

Personally Id stick with the 317. It's more durable and precise than a resistor.
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Re: ZH Boost - subminiature tube booster

Postby himister » 18 Oct 2009, 21:02

kurtlives wrote:Why do you have the screen at a higher potential than the plate? I always thought that was a no no.

Personally Id stick with the 317. It's more durable and precise than a resistor.


To be honest...I don't know. Maybe datasheet is faulty and they swapped screen for plate. :shock: :lol:
When I tested the tube for the first time I used a resistor to keep a different potential to anode and it sounded like crap. I tried to change the values and even used a trim-pot for both plate and screen and result was the same.
In one moment I connected screen directly to supply rail and it cleaned it self. Usually I wouldn't do such a thing with a HT supply but since I used only 9V I though...what a heck. :mrgreen: At first I though, it a suppressor grid and that awful dirt is made by less amount of voltage going to anode, so I connected directly so it would "pump it up". I left the anode trim-pot to adjust the best value for anode and also it's useful to reduce the hum from supply.
I must say these tubes are very odd little fellows. :D

Last night done some more testing and I cleaned up the sound by using voltage doubler before rectifier and increased the anode voltage to almost 37V. Very worm and sweet sound, and also increased gain. I put a simple tone control and even tried a clipping diodes to get a bit of drive, but not much, very small amount of dirt is coming out right now but I believe some people will love these results, at least for a clean type of play. Also done some odd mods :shock: . I added one more 1uF cap after the same one coupling cap and made a feedback loop as a filter for top high frequencies by connecting another 560p cap between 1uF caps and a grid. This mod tames the harshness from the pickups and it could be used as some kind of low pass filter, still experimenting with that one.

Schematic Ver.1.1:


ZHBoost1.1.GIF
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 18 Oct 2009, 23:02

Hey, did you ever see my Red Star Drive? http://www.diystompboxes.com/smfforum/i ... ic=71350.0

You might have better diode clipping if you use Ge.
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Re: ZH Boost - subminiature tube booster

Postby himister » 18 Oct 2009, 23:15

I guess I did but didn't pay that much attention on details. That's just what I thought last night. Didn't tried yet. It's the next thing on my to do list.
Thanks Rick. I appreciate any suggestion.
Cheers :thumbsup
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Re: ZH Boost - subminiature tube booster

Postby himister » 18 Oct 2009, 23:24

Ohhhh damn.... :lol: :lol: :lol:
I looked over after posting answer and saw the similarities with my latest test. :slap:
Those caps... :oops: Honestly didn't have a clue. Actually I've been inspired by some laney amp designs regarding series connected caps.
I swear I didn't use anything from a RStar. Only wires and blind testing on my bench.
To be more honest I don't lurk that much on diystmpbxs 'cause like it better here, but maybe I should.
It's wonderful when you see that someone else tried a same thing. :wink: :D
So much of originality of things these days. Nothing new under the sky! :lol:

Well done Rick :hug:
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 19 Oct 2009, 00:06

Hey, don't sweat, it's cool. 8)

You might also try back to back diodes in series with a low value cap between grid 1 and the plate, like this:

viewtopic.php?f=13&t=6525&hilit=promiscuous+girlfriend
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Re: ZH Boost - subminiature tube booster

Postby gena_p1 » 19 Oct 2009, 10:34

Looks very cool! Valve alternative to MXR Microamp and SHO.

And these tubes can be used in phasers
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Re: ZH Boost - subminiature tube booster

Postby himister » 19 Oct 2009, 11:25

Thanks. Спасибо. :wink:
I was hoping to build tube alternative like this one. As for the phaser It would be nice if someone would post projects like that.
I wonder if anyone here knows some good reliable US, EU or Russian supplier of these tubes?
http://www.russiantubes.com/delivery.php
http://www.gstube.com/
http://www.globex.com.ru/products/Vacuu ... d_Sockets/
I found a few but I'm more interested in hearing experiences. Any info would be helpful.

Cheers :thumbsup
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Re: ZH Boost - subminiature tube booster

Postby himister » 26 Oct 2009, 18:06

Here are some photos of the prototype. Works very nice. It could be tweaked anytime at personal taste.
I didn't go for a pcb since there are less components then usual but I'll make that one too, when my time allows.
I've tested this one in many variants so it could be useful for boosting the clean guitar signal or single coil pickups, also it's very useful when using in combination with tube amp lead channel and one nice characteristic is that boosts the mid-range freq. so rhythm and solos sound much more present and also boost the amount of gain in very musical way.
Note: I've used first schematic for this one and left out tone control, clipping diodes and low pass cap and switch.
Cheers :wink:

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07.jpg
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 26 Oct 2009, 18:27

That's the smallest tube pedal I've ever seen! :shock:

Respect!
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Re: ZH Boost - subminiature tube booster

Postby himister » 26 Oct 2009, 18:38

Thanks Rick. :wink:
I also think it is. :shock: jeeez.... small, tiny.... but wouldn't believe, it's stable and it doesn't flips when you stomp it. :lol:
I'm very happy with it. :D
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Re: ZH Boost - subminiature tube booster

Postby himister » 28 Oct 2009, 19:49

I hope this will be my last post for today. :mrgreen:
Here it is, for all of our enjoyment I made a "blue prints" how to make this little fellow.
Hope to be useful. Credits noted in the pdf file. :wink:


ZHBoost.pdf
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Re: ZH Boost - subminiature tube booster

Postby frequencycentral » 28 Oct 2009, 19:55

himister wrote:Credits noted in the pdf file. :wink:


You're a gentleman - I feel all immortalised now! 8)
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Re: ZH Boost - subminiature tube booster

Postby himister » 28 Oct 2009, 20:02

frequencycentral wrote:
You're a gentleman


I sure try to be, all the time. Just like to be thankful for any help, anywhere. Doesn't hurt to be polite, and my mom tried to raised me to be a good boy. :lol:

frequencycentral wrote:
I feel all immortalised now! 8)
:lol: :applause: :thumbsup
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Re: ZH Boost - subminiature tube booster

Postby Mr. G. » 28 Oct 2009, 23:04

Goo stuff bud! :thumbsup

Circuit and build looks awesome! Got any soundclips?

Did you have to do much alteration to the template for it to work with the Eddystone enclosure, or are they pretty much the same as the 1590a?
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