# Help me pick out some tubes



## BuddytheReow (Jul 10, 2022)

I think it may be time to tinker with some tube circuits. The problem is I know virtually nothing about how they work or what's considered a "good" one to start out with. I know some of you have built with them and I want to see what all the fuss is about. Can anyone recommend some good reading material on how they work, the difference compared to a transistor, and possibly recommend a few to pick up for tube noob like me?


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## fig (Jul 10, 2022)

I’d start with a good HV primer. Working with a SMPS can go around 350V. I’m currently working on a 12AX7 (dual triode) preamp. It’s a common tube with a lot of circuits drawn around it. But I’m no expert. 

You’ve probably read “A closer look at the Fetzer valve”, but it may be worth a 2nd glance.


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## BuddytheReow (Jul 10, 2022)

fig said:


> I’d start with a good HV primer. Working with a SMPS can go around 350V. I’m currently working on a 12AX7 (dual triode) preamp. It’s a common tube with a lot of circuits drawn around it. But I’m no expert.
> 
> You’ve probably read “A closer look at the Fetzer valve”, but it may be worth a 2nd glance.


Forgot about that fetzer article. Sorry for the noob question, but what do those acronyms mean?


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## Harry Klippton (Jul 10, 2022)

High voltage, switch mode power supply


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## fig (Jul 10, 2022)

or super mario power supply….


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## Bricksnbeatles (Jul 10, 2022)

Or Slimy, milky, pustule-scab


Let’s hope not


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## BuddytheReow (Jul 10, 2022)

I still need to read up a bit on the subject, but would I need a whole separate set of components for the high voltage? Resistors, caps, etc.


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## Harry Klippton (Jul 10, 2022)

@vigilante398 wrote some tube circuit primers around here somewhere a few months ago


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## jeffwhitfield (Jul 10, 2022)

Out of all the tubes I’ve tried (Sovtek, JJ, and EHX), I’ve been quite pleased with the JJ tubes. I use a JJ ECC83 (12AX7) in one of my tube pedals and recently installed an JJ ECC82 (12AU7) in a Butler clone.


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## benny_profane (Jul 10, 2022)

Tubes 101 - Intro to Tube Preamp Design
					

Hi there! I had a couple requests to talk about my design process for tube preamps, so figured I would write up a super boring guide with way too many words and way too many pictures. I’m going to be using a lot of resources from https://www.ampbooks.com/mobile/amplifier-calculators/ which has...




					forum.pedalpcb.com
				








						Tubes 102 - Intro to Power Supplies for Tube Circuits
					

I had planned to add this post on to the previous post about tube preamp design, but as I was writing it I found it getting way longer than I had planned, so I figured I would make it a separate topic.  So how do I power these tubes?  Well let’s start with the heater, without that you won’t be...




					forum.pedalpcb.com


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## cwsquared (Jul 10, 2022)

benny_profane said:


> Tubes 101 - Intro to Tube Preamp Design
> 
> 
> Hi there! I had a couple requests to talk about my design process for tube preamps, so figured I would write up a super boring guide with way too many words and way too many pictures. I’m going to be using a lot of resources from https://www.ampbooks.com/mobile/amplifier-calculators/ which has...
> ...


I may just have to read those again.  So much great knowledge in there.


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## vigilante398 (Jul 10, 2022)

benny_profane said:


> Tubes 101 - Intro to Tube Preamp Design
> 
> 
> Hi there! I had a couple requests to talk about my design process for tube preamps, so figured I would write up a super boring guide with way too many words and way too many pictures. I’m going to be using a lot of resources from https://www.ampbooks.com/mobile/amplifier-calculators/ which has...
> ...


Thanks for pulling those links so I didn't have to  happy to help answer any questions you have if they aren't covered already. I don't think I'm old enough to be considered a tube expert, but I've built a good handful of tube circuits including a fair number of original designs and have a reasonable understanding of their general goings on.


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## Feral Feline (Jul 12, 2022)

Check out The Tube Store, I got a great deal on some JAN 12AX7 there.

While I'm not as tube savvy as HamishR and Vigilante398 (I've bought a drop compared to the buckets of tubes they've bought), The Tube Store has been the best I've found for sourcing tubes.

Yeeps! I just checked the JAN GE prices and they've gone wayyyyheyyyy up. So maybe not mil-spec JANs then...

Still, I got great customer service from The Tube Store, and very good CS from Amplified Parts, too.


For some circuits, and/or for bass, you may want to check out getting some 12A*U*7 tubes, a little less gain than the Xes which may have Xcessive harsher distortion when you're looking for just some smooth grit.

Haven't read this, it was the first hit to find some info for you about 12A?7 series tubes:








						12AX7 vs 12AT7 vs 12AU7 Tube Shootout (Differences, Which To Buy)
					

Swapping tubes is a cheap and easy modification that can have great results. But not all tubes are equal! We put three common types to the test.




					producerhive.com


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## vigilante398 (Jul 12, 2022)

Oh that reminds me, someone brought this video to my intention the other day. It's done on bass so you have to use your imagination on how it carries over to guitar, but I think he did a great job showing the gain differences between different tube types.

Also lets you hear the Space Heater preamp, which I'll hopefully have a working DIY project for soon (but without the turrets and engraved wood faceplate).


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## Alan W (Jul 13, 2022)

A smaller tube amp kit might be a great intro. I started out building tube hi fi stuff in the late 70s, at first 12ax7 preamps, then 6DJ8 preamps*, and eventually some mono blocks. You do need different components, but more importantly, you need to unlearn many of the build habits that learning on low voltage DC projects can lead to. While any AC project can be dangerous, ones that use 350 or 450 v  are definitely “sit on one hand when you reach in” devices.

Anyway, a lower powered amp head or combo kit would be a great intro. There are also several good micro tube amp projects (that could be made in larger pedal format) that would be fun too. I have most of the parts sourced an easy decade ago, for a .5 watt micro tube amp in a box, somewhere in my attic, that I really should hunt down.

(* I’ve never understood why the 6DJ8 (E88 family) tubes never made any inroads as guitar preamp tubes. Every hi fi preamp I made with them was better than any of the 12a*7 variants I tried.)


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## vigilante398 (Jul 13, 2022)

Alan W said:


> (* I’ve never understood why the 6DJ8 (E88 family) tubes never made any inroads as guitar preamp tubes. Every hi fi preamp I made with them was better than any of the 12a*7 variants I tried.)


Guitar preamps are designed differently than hi-fi preamps, we don't use 6DJ8 mostly because they don't have enough gain. 12AX7, every amp-builder's dual triode of choice, has a mu (amplification factor) of 100, whereas 6DJ8 has a mu of 33, putting it just above a 12AU7. Typically for guitar amps you want something in the 70-100 range, so things like 5751 and 6SL7 on the lower gain side and 12AX7 on the higher gain side. We play tube amps because we want tube dirt.


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## Bricksnbeatles (Jul 13, 2022)

vigilante398 said:


> Oh that reminds me, someone brought this video to my intention the other day. It's done on bass so you have to use your imagination on how it carries over to guitar, but I think he did a great job showing the gain differences between different tube types.
> 
> Also lets you hear the Space Heater preamp, which I'll hopefully have a working DIY project for soon (but without the turrets and engraved wood faceplate).


I saw that video a few days ago. How do you think it would transfer over to the Black Eye? 

Another thought I had, but was not sure about since I’m not too adept at reading tube circuits: could you do 12AX7 for v1 and a 12AU7 for v2 or vice versa similar to how you might put a low gain transistor as q1 and a high gain transistor as q2 or vice versa in a two-transistor fuzz? Of course the black eye is two dual-triodes so it would be more comparable to a 4-transistor circuit, but just for the sake of my question, the two-transistor fuzz is what popped in my head. Not sure if the two tubes have to match each other (only glanced over the build doc and schematic), but if not, do you think that might be a worthwhile idea?


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## jeffwhitfield (Jul 13, 2022)

Feral Feline said:


> Check out The Tube Store, I got a great deal on some JAN 12AX7 there.
> 
> While I'm not as tube savvy as HamishR and Vigilante398 (I've bought a drop compared to the buckets of tubes they've bought), The Tube Store has been the best I've found for sourcing tubes.
> 
> ...


Good reading on the tube differences. In my case, it turned out that a 12AX7 wasn't the best choice for my BK Butler clone. They have the highest gain, which makes total sense. A 12AT7 type tube still felt a bit too high. 12AU7 was the magic one. A lower gain tube made all the difference in this circuit. Might consider one of each just to test things out with.


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## vigilante398 (Jul 13, 2022)

Bricksnbeatles said:


> I saw that video a few days ago. How do you think it would transfer over to the Black Eye?
> 
> Another thought I had, but was not sure about since I’m not too adept at reading tube circuits: could you do 12AX7 for v1 and a 12AU7 for v2 or vice versa similar to how you might put a low gain transistor as q1 and a high gain transistor as q2 or vice versa in a two-transistor fuzz? Of course the black eye is two dual-triodes so it would be more comparable to a 4-transistor circuit, but just for the sake of my question, the two-transistor fuzz is what popped in my head. Not sure if the two tubes have to match each other (only glanced over the build doc and schematic), but if not, do you think that might be a worthwhile idea?


I think it would carry over reasonably well, it gives you an idea of how much the tubes themselves will overdrive. As for mixing and matching in different positions it's absolutely something you could do. A single tube stage by itself doesn't distort really, it's only when you feed it too hot of an input signal that it gets into overdrive. So running a 12AX7 as V1 would give it more gain in the earlier stages, which would push the later stages harder, whereas a lower gain tube like 12AU7 in V1 wouldn't push very much and you would get much less distortion, even with a 12AX7 in V2. I wouldn't go out of your way to source a bunch of tubes to try it, but if you already have a couple different types on hand I would definitely say it's a worthwhile experiment.



jeffwhitfield said:


> Good reading on the tube differences. In my case, it turned out that a 12AX7 wasn't the best choice for my BK Butler clone. They have the highest gain, which makes total sense. A 12AT7 type tube still felt a bit too high. 12AU7 was the magic one. A lower gain tube made all the difference in this circuit. Might consider one of each just to test things out with.


Yeah on lower voltage circuits like Valvecaster and Tube Driver the rules change a bit. 12AX7 doesn't like being starved and sounds harsh and brittle when plate voltage is less than 150V or so. 12AU7 doesn't mind a low plate voltage and runs quite well starved.


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## Chuck D. Bones (Jul 14, 2022)

Check this out.  You can mess with tubes and not get shocked or your fingers burnt.

https://forum.pedalpcb.com/threads/this-week-on-the-breadboard-a-mini-tube-pedal.12468/


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## HamishR (Jul 14, 2022)

I got into using dirt in my sound from amps which had dirt channels. I believed that distortion had to come from tubes. That's what all the magazines said! Then along my playing journey I got into single channel amps for various reasons, and felt I needed a tube pedal at least for my dirt. My favourite of all of them was/is the Badcat Two-tone, which is a Vox top-boost preamp in a box. It uses two 12ax7s running at full B+ voltage via a transformer built into the box and it runs off wall voltage. There are others which are very good too - the Kingsleys are excellent and work in a similar fashion with different flavours available.

But because the Badcat has the transformer inside the enclosure noise can be an issue. Mine was ok - the Matchless versions are smaller therefore noisier, as the transformer is closer to the very sensitive 12ax7 circuitry. Layout is critical in these things because space is tight and the high voltages make everything susceptible to picking up noise and hum.

Then I discovered that I could get sounds I liked as much or possibly even more with SS pedals. I did a lot of blind testing and was delighted/dismayed to find that often I couldn't tell the difference between a tube OD and a well designed SS OD. It's easy to pick a Tubescreamer as a SS pedal if you use it purely for dirt. But a more natural sounding pedal is not so easy to pick in blind testing - it's surprising.

The benefits to me of my favourite SS ODs are things like size, noise and consistency. I can build my favourites into a 1590B or two of them into a 1590BB. They can be extremely quiet. And I don't have to worry about varying wall voltages or tube wear affecting my signal in audible ways. And, having worked on the Badcat after an outdoor gig blew the power transformer (generators and guitar amps don't mix well) I know that 9V pedals are less likely to zap my fingers! I've never got a buzz from an amp but the tube preamps have serious voltages all over the place. Treat them like an amplifier. It makes swapping tubes tedious because there is potential HV right where you might want to put fingers to ease tubes out of sockets.

This mainly applies to pedals using tubes at proper amp voltages. The pedals can sound fantastic and I still love the Two-tone. But I've found the convenience and affordability of building SS ODs very attractive and the main reason I had for using tubes - sound - is just about moot.

So don't let me put you off! It's a lot of fun using tubes in pedals. And easy to change the sound because tubes all sound different. More and more I turn to JJs because I like the sound, the cost and the consistency. Also I don't like New Sensor as a company and I don't want to buy Russian right now!


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## BuddytheReow (Jul 16, 2022)

What kind of tubes can I get to experiment with that don’t require HV? I’ve got plenty of breadboard worthy components and just looking for something new. I would like to try Chuck’s build when I pull the trigger on them


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## Feral Feline (Jul 17, 2022)

Build a Valvecaster ?


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## Chuck D. Bones (Jul 17, 2022)

Try higher plate voltage.  Better to run the filaments at the correct voltage. Running a 12V filament at 9V can produce unpredictable results.


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## fig (Jul 17, 2022)

Chuck D. Bones said:


> View attachment 29204
> 
> Try higher plate voltage.  Better to run the filaments at the correct voltage. Running a 12V filament at 9V can produce unpredictable results.


Can charge pumps be used to acheive a reasonable voltage?


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## vigilante398 (Jul 17, 2022)

Chuck D. Bones said:


> View attachment 29204
> 
> Try higher plate voltage.  Better to run the filaments at the correct voltage. Running a 12V filament at 9V can produce unpredictable results.


I've had pretty good luck running 12V filaments at 9V. Anything below 8 starts to get dicey, but 9V has been fine. Lower current draw, less heat, and longer tube life, but agreed you don't want to go too low.


fig said:


> Can charge pumps be used to acheive a reasonable voltage?


Depending on the tube, sure. There's a commercially available preamp out there that uses a charge pump for a B+ of 27V. It's fine. 12AX7 doesn't like low voltage as much so wouldn't sound as good, but something like a 12AU7 runs fine with 27V up there.


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## Scruffie (Jul 17, 2022)

fig said:


> Can charge pumps be used to acheive a reasonable voltage?


You can add as many stages of diodes/caps as you like practically, but the quantity required for anything over 50V (70 if you go with a 12V supply, which you're gonna want if you're playing with triodes any-who) makes it a bit impractical...

I made this project some time back, layout ain't perfect but it works and is a fun little amp, a 1W(ish) AC30 to fit a 1590BB with self-split triode output stage, MAX1771 SMPS & MOSFET source follower, got the layout still if you desire.


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## Chuck D. Bones (Jul 19, 2022)




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## BuddytheReow (Jul 23, 2022)

Just ordered some 6418 tubes from eBay to try out on a breadboard. Should be here sometime next week


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