Spark Gap: Unusual 9V Hybrid Valve Overdrive

[juansolo]

Wizard's Sleeve
Continuing the wizard theme

Amazing! I'm even reading Unseen Academicals at the moment! Is that just printed onto transparency and then lacquered on?

Haven't read that yet, though it is the next on the list

Stonking pedal BTW. Love it!

The transparency is actually clear adhesive inkjet paper (but yes, basically a sticky transparency lacquered over on a painted box). I get asked about it a lot so did a guide: clicky (yeah, there was a mistake on the first Sleeve label, I did another with the right voltage). Very much my prefered method of decaling.

[misterg]

Wizard's Sleeve

Continuing the wizard theme

...

That looks fantastic!

Here's my #2 - built for a friend who is going to paint / finish it himself. It's a PCB build which I have to say I found much harder to put together than the vero one 

He requested 'protection' and this is the best I could come up with.





Thanks again Merlin.

Andy

[MichelP]

Merlin, wow ! Interesting pedal to build !!  1 question : the Russian 6H2P tube is listed as an equivalent of the EB91, could I use them ? 

[merlinb]

the Russian 6H2P tube is listed as an equivalent of the EB91, could I use them ? 

Yes, I don't see a problem with that.

[jaapie]

I have a couple of 3AL5s. Would I need to adjust the heater voltage to compensate for the different heater voltage rating? It looks like the heater voltage is lowered by 25% for the 6AL5s, so should I run the two 3AL5s at about 4.5V in order to get them to work properly?

[merlinb]

I have a couple of 3AL5s. Would I need to adjust the heater voltage to compensate for the different heater voltage rating? It looks like the heater voltage is lowered by 25% for the 6AL5s, so should I run the two 3AL5s at about 4.5V in order to get them to work properly?

Yes I would expect that to work. However, the transistor regulator in my design won't be able to handle the power dissipation (your heaters will demand close to 500mA), so you'll have to find an appropriate way to do it.

[stevie1556]

Just started building this on strip board until I get a PCB sorted out.

A few questions though:
- What value are the diodes? I can see one on the schematic is 1N4001, is it the same for both?
- Is the transistor BC327-16 ok?
- Is the transistor BC337-25 ok?

[merlinb]

- What value are the diodes? I can see one on the schematic is 1N4001, is it the same for both?

There is:
One 1N4001
One 9.1V zener diode (e.g., BZX55C9V1)
One LED  of your choice.

- Is the transistor BC327-16 ok?
- Is the transistor BC337-25 ok?

Yes.

[stevie1556]

Thanks for the quick reply. Just ordered the extra transistors, and a couple of values of resistors that I seem to be missing.

Will post an update when it's done! 

[danamoose]

Hey guys, I am starting to plan this out for my next build. I am writing out a parts list and have a few questions on some of the values. May be my screen but some are unclear so i wanted to ask. I have gone through all the posts on this several times to see what answers I could find there but here is what i still have pending:

R11 looks to say 220R on my screen....is that supposed to be 220K?
Same with R16/17...they look like 100R on my screen is that 100K?
What is "Link 2-zero"?

Thats all for now.
Thanks in advance!
-Dana

[merlinb]

R11 looks to say 220R on my screen....is that supposed to be 220K?
Same with R16/17...they look like 100R on my screen is that 100K?

No, they're 220R and 100R. R means ohms.

What is "Link 2-zero"?

Means a wire link. Zero ohms.

[danamoose]

Thanks Merlin, sorry for the noob questions 
-Dana

[wesman26]

This is completely awesome; I can't wait to get some tubes and build one.  I have some questions though, mostly because I'm new and don't necessarily understand. 

I don't see how the voltage regulation on the heaters works, what voltage does it set them to?  What would I do to set it up such that I can change the heater voltage?

I saw PRR's post and recommendation, but I'm afraid I still don't understand quite how it works.  Any help would be much appreciated.

Thanks in advance,
--Wes

[armstrom]

wow, nice design and some great looking builds here! While this is an old thread it seems to have been brought back to life so I would like to take the opportunity to ask a question

Some time ago I penned this design:


But have not yet gotten around to building it. My plan is to use a 6AG11 compactron for the tube (it has two high-mu triodes and two diodes with discrete cathodes all in the same envelope) and a nixie SMPS for the HV (Will probably run closer to 180-200V than the indicated 300).

My question is, did you only need to mess around with the heater voltage on your design because you were dealing with the smaller voltage swings inherent in a 9V pedal design? As my chosen tube has a single 6.3V heater for all three elements within the envelope I don't really have the ability to change my heater voltage on the tube section without going to a separate tube for the diodes. I'm also considering adding a pot to the shared ground connection for the diodes so that I can lift them slightly and tame the clipping. I'm not sure how well that will work though. Your thoughts? I don't think I will have the same issue you did with your diodes (too sharp of a transfer function) If you look at the datasheet for the 6AG11 http://tubedata.tubes.se/sheets/093/6/6AG11.pdf you can see that the plate voltage to plate current curve is much less severe. We'll see though I have the tubes I just need to set aside some time to build the thing.

-Matt

[danamoose]

I thought sharing a parts list might help others save time on future builds. Here is what I came up with. Anyone want to give this another look to verify the values are accurate?
Thanks, and hope this helps others!

V1 - EB91 (6AL5), V2 - EB91 (6AL5)
IC - TL074, SW1 - SPDT, LINK 2 - JUMPER WIRE
D1 - 1N4001, D2 - Z9V1, D3 - LED, D4 - LED
Q1 - BC337, Q2 - BC327, Q3 - BD435, P1 - B10K, P2 - B10K,P3 - B10K
R1 - 10M,R2 - 1M,R3 - 1K,R4 - 2.7K,R5 - 1K,R6 - 2.7K,R7 - 10K,R8 - 100K,R9 - 10K,R10 - 10K,R11 - 200OHM,R12 - 10K,R13 - 10K,R14 - 1K,R15 - 470,R16 - 100OHM,R17 - 100OHM,R18 - 10K,R19 - 1M
C1 - 100n,C2 - 10u,C3 - 1u,C4 - 470p,C5 - 10u,C6 - 10n,C7 - 10u,C8 - 10u,C9 - 10u,C10 - 10u,C11 - 10u,C12 - 10n,C13 - 10n

-Dana

[wesman26]

I thought sharing a parts list might help others save time on future builds. Here is what I came up with. Anyone want to give this another look to verify the values are accurate?
Thanks, and hope this helps others!

V1 - EB91 (6AL5), V2 - EB91 (6AL5)
IC - TL074, SW1 - SPDT, LINK 2 - JUMPER WIRE
D1 - 1N4001, D2 - Z9V1, D3 - LED, D4 - LED
Q1 - BC337, Q2 - BC327, Q3 - BD435, P1 - B10K, P2 - B10K,P3 - B10K
R1 - 10M,R2 - 1M,R3 - 1K,R4 - 2.7K,R5 - 1K,R6 - 2.7K,R7 - 10K,R8 - 100K,R9 - 10K,R10 - 10K,R11 - 200OHM,R12 - 10K,R13 - 10K,R14 - 1K,R15 - 470,R16 - 100OHM,R17 - 100OHM,R18 - 10K,R19 - 1M
C1 - 100n,C2 - 10u,C3 - 1u,C4 - 470p,C5 - 10u,C6 - 10n,C7 - 10u,C8 - 10u,C9 - 10u,C10 - 10u,C11 - 10u,C12 - 10n,C13 - 10n

-Dana

I think Q3 should be a BD437.  Also, Merlin, where did you get those tube sockets?

[merlinb]

I think Q3 should be a BD437. 

The BD433 and BD435 will also work.

Also, Merlin, where did you get those tube sockets?

ebay:
http://www.ebay.co.uk/itm/2-NEW-B7G-7-PIN-MINIATURE-PCB-MOUNT-TUBE-SOCKETS-/350515876687?pt=Vintage_Electronics_R2&hash=item519c5fd34f#ht_947wt_1344

http://www.ebay.co.uk/itm/40-7-pin-PCB-Mount-Mini-Tube-Socket-12AE6-3AV6-/270491239967?pt=UK_Consumer_VintageAudio_RL&hash=item3efa88c61f#ht_2555wt_1297

[juansolo]

Don't think I ever posted this. This is Merlin's Spark Gap feeding into Rick's (Frequency Central) Promiscuous Girlfriend. Pretty much a pedal of mass destruction. Absolutely epic thing

[blackcorvo]

...what if one used a diode tube in the Diode Compression Op-Amp?

And what do you guys think of the 6H6? It's a tiny twin-diode in an octal base (looks like a midget 6L6 lol), that I happened to find on the site I usually buy tubes from. They have a nice stock of brands like General Electric and RCA.

I guess if you used these little guys for a distortion/overdrive pedal, you could even get some octal bases, each with different diodes types/combinations, and you could change them like you change tubes in an amp! OR you could have a single octal base, and a small board connected to it with lots of diodes, LEDs, transistors... and switches to change between them, make different combos... and an orange or amber LED connected to the heater pins...

Doesn't sound very practical, I know. But I bet that would be lots of fun to play with!

[iccaros]

Don't think I ever posted this. This is Merlin's Spark Gap feeding into Rick's (Frequency Central) Promiscuous Girlfriend. Pretty much a pedal of mass destruction. Absolutely epic thing

nice, but crap, I have another project on the list now.....