I have a bunch of 6SN7 and EL34 tubes, from my hifi amps and projects, and a bunch of big Lundahl chokes and power supply from my old Aikido preamp build. Lots of caps, resistors etc on hand.
My 15yo son is a bass and guitar player with a strong interest in jazz. I would love to work on a guitar amp project with him, and build a pretty simple headamp with a 6sn7 driver and EL34 power tube, either in pp or se. Not too picky there. Would be a practice amp, so no need for high power.
I think I have most everything I would need for a simple guitar amp (with just volume, no bass/mid/treble controls or anything else). I would only need to buy an appropriate output transformer.
Any good simple 6SN7/EL34 guitar amp schematics that someone can recommend? I just started looking online as well...
Thank you!
My 15yo son is a bass and guitar player with a strong interest in jazz. I would love to work on a guitar amp project with him, and build a pretty simple headamp with a 6sn7 driver and EL34 power tube, either in pp or se. Not too picky there. Would be a practice amp, so no need for high power.
I think I have most everything I would need for a simple guitar amp (with just volume, no bass/mid/treble controls or anything else). I would only need to buy an appropriate output transformer.
Any good simple 6SN7/EL34 guitar amp schematics that someone can recommend? I just started looking online as well...
Thank you!
@jayme :
Search for :
- Fender 5E1 or 5F1 tweed Champ amp.
- Gibson GA-5 Les Paul Junior amp.
For the most praised ones.
Otherwise, you have also a bunch of Valco / Supro / Gretsch / Harmony / Danelectro models, which are great little amps too !
The choice is wide ! Just remember that a Guitar amp is rather a Lo-Fi amp for good sounding... 😉
T
Search for :
- Fender 5E1 or 5F1 tweed Champ amp.
- Gibson GA-5 Les Paul Junior amp.
For the most praised ones.
Otherwise, you have also a bunch of Valco / Supro / Gretsch / Harmony / Danelectro models, which are great little amps too !
The choice is wide ! Just remember that a Guitar amp is rather a Lo-Fi amp for good sounding... 😉
T
You're probably going to have more luck with 6SL7 + 6V6. Just sub in your EL34, and bias accordingly.
https://www.prowessamplifiers.com/schematics/fender/princeton_5b2_schem.pdf
jeff
Hmm. What are the multiple inputs on those schematics? For multiple inputs? (Aka make it easier to swap to an effects pedal?)
I will look at my stash of tubes. I might have a 6sl7 lying around....seems that is close to a 12ax7.
I will look at my stash of tubes. I might have a 6sl7 lying around....seems that is close to a 12ax7.
Pretty sure having a couple of inputs was standard back in the day. Don't think there were a lot of effects pedals back in the 50's & 60's. 😉
jeff
jeff
Yes. For accordion, guitar, microphone, etc... It was very common at that time.
Guitar amps are not an Audiophile thing : small coupling caps values, small speaker with stiff cone and 100Hz resonance, anemic transformers... See my little 1964 Danelectro DM10 - once restored :
T
Google "Single ended EL34 guitar amp" and you'll come up with lots of ideas.
for example:
http://ephaseaudio.com/audio/EL34SE amp/The Bluesman.htm
https://www.tdpri.com/threads/single-ended-el34-amp.753467/
Good luck!
for example:
http://ephaseaudio.com/audio/EL34SE amp/The Bluesman.htm
https://www.tdpri.com/threads/single-ended-el34-amp.753467/
Good luck!
The AX84 P1 was a popular SE EL34 amp (does have tone controls). Swap out the 12AX7 for your preferred tube and tweak the bias to taste?
http://ax84.rru.com/media/ax84_m37.pdf
Note that the classic Fender circuits didn't have a screen stopper, which you definitely want in a modern guitar amp. 1k 2W+ is ideal (R5 in the P1 circuit).
http://ax84.rru.com/media/ax84_m37.pdf
Note that the classic Fender circuits didn't have a screen stopper, which you definitely want in a modern guitar amp. 1k 2W+ is ideal (R5 in the P1 circuit).
Yes. It's recommended for EL34 by the way... That's what you can see on the rare and odd SE Marshall Mercury 2060 amp (R14) :
And you retrieve those 1K 5W resistors on many other well-known Marshall, like the 2203 and 2204 :
T
I can't find a single guitar amp schematic with 6SN7 because it's such an unusual choice. I think if you insist on using it you will have to use 2 of them for 3 triode sections in series, or just 1 tube with 2 triode sections in series and live with the low gain.
Yeah, looks like the 6SN7 is the wrong choice here. I might just pick up extra 12AX7 for this. I would prefer the octal 6SL7 (which has a similar mu at 100), but I saw comments about the 12AX7 having humbucking filaments due to its inherent design.
Another issue is that the octal 6SL7, 6SN7, 6SC7 were rather microphonic compared to the 12AU7/12AT7/12AX7... Think that a guitar amp is sometimes a good vibrator with its incorporated speaker : EL34 and EL84 are more affected by vibrations than 6L6 and 6V6 on this point.
T
You need to work backwards with valve amps. Start with EL34 what will it be biased at? Say -35V - guitars put out roughly 100mV so you need a gain of 350 to drive the EL34 to maximum. Remember this is the peak voltage. 2x 6SN7s with a gain of x15 each (both cathodes bypassed) will give you a total gain of x225 - without any feedback around the power amp (valve) - which is no bad thing and you might even prefer the sound. But all is not lost because guitar amps tend to be very loud and you might not need all that volume…or you could bias your EL34 hotter. Remember guitar amps are about tone so there is no inherently wrong design. Also you could easily use both SN7s and SL7s: use say 100k anode resistors for SL7s and parallel them with 68k-100k for SN7s do the same for cathode resistors 2k2 or more for SL7s parallel them to get 470 - 1k for SN7s. Fiddle and let the player use their ears. Put the volume control between thee two triodes so you can dial some overdrive in or out
Disagree with previous post, I doubt an amp can be constructed as described and be stable.
Without feedback stability is not an issue - of course one must use grid (and screen) stoppers on all valves. If you’re using SL7s you include the feedback loop but you would probably prefer the sound without it. You will be surprised at how good these small amps can sound,,,
I'm a bass player and I've played around with input tubes. Sure enough, the 12AX7 has the best tone. For hi-fi I'd use a 6SN7 but for a stage amp the tone is nicest with the 12AX7. They had good reasons for using it. Never tried the 6SL7 - I think Ampeg used that.
Ampeg B15 used octal preamp tubes (6SL7), paired with 6l6gc output, but they can easaly be changed for EL34 with some changes in schematic.
I would suggest going for a push-pull amp instead of single ended. With a bass amp you want some power to get the lows out there.
I have build and repaired some guitar amps, never really build or look into tube hifi so far. Guitar amps are quiet simple i think compared to hifi stuff.
When i started out i had a lot of info on this site http://www.valvewizard.co.uk/
This is also a great site https://www.ampbooks.com/ with lots of usefull calculators.
To answer your question about the inputs. Vintage amps often have more input for more instruments or guitar+microphone or something. But sometimes the inputs are switched in a way that you got a low and a high gain input. Look at the marshall schematics, high input has a 68K grid stopper, while the low input forms a voltage dividers with the two 68k resistors, halving the input signal. Sometimes amps have on input bypassing the first triode stage to create a high and a low gain input.
I would suggest going for a push-pull amp instead of single ended. With a bass amp you want some power to get the lows out there.
I have build and repaired some guitar amps, never really build or look into tube hifi so far. Guitar amps are quiet simple i think compared to hifi stuff.
When i started out i had a lot of info on this site http://www.valvewizard.co.uk/
This is also a great site https://www.ampbooks.com/ with lots of usefull calculators.
To answer your question about the inputs. Vintage amps often have more input for more instruments or guitar+microphone or something. But sometimes the inputs are switched in a way that you got a low and a high gain input. Look at the marshall schematics, high input has a 68K grid stopper, while the low input forms a voltage dividers with the two 68k resistors, halving the input signal. Sometimes amps have on input bypassing the first triode stage to create a high and a low gain input.
