Schematic for a small SE EL84 amp

[earx]

Oh sorry, I should have mentioned TRIODE mode. It's a lot more linear. You can get about 5W with a pair of push-pull EL84 in triode mode.

The schematic from planet10 is nice but I don't like it (just my opinion). What's the point of trying to go SE with a pentode? And feedback? It will kill all the magic of SE. Go push-pull and it will be cheaper (you save on OPT).

I also don't like the 680pF feedback cap. This is CURRENT FEEDBACK, not voltage. A capacitor in the feedback loop only makes the amplifier more unstable. The loop compensation cap should be on the plate of the first stage.

RMS: if you realy want to go SE, then you must get a REALLY linear tube. And that's why the 300B, 2A3, 45, etc. have achieved cult status. Nothing else comes even close. Measure the EL84 or EL34 or 6L6, they just don't have the linearity. That's why they're used with feedback.

There's more to a guitar amp than bandwidth < 5kHz. They need distortion, and lots of it. And tone controls that make it far from flat. It's a whole different way of looking at things.

jh

hi
i test this amp, is working only if i cut the entire loop with the 680pF feedback cap.
what do u think i must do ?
what cap must i put on the plate in the first stage if i cut
or try different values in the loop or remove the cap ?
this loop is for linear response ?
thanks for reading all this question and the future answer
cheers

Ps: the sound is very good for my first test

 

[Tom Bavis]

If it oscillates, the transformer must have its phase revered. Swap the primary or secondary leads and try again. Gain should go DOWN with feedback applied.

 

[earx]

thanks tom for this fast answer

 

[M Gregg]

You must be referring to the neat little phase-splitterless PP amp. R3 is the tone control, it & the cap in series with it could just be eliminated. R5 is the volume control, it could be replaced with a fixed R.

dave

Where is the schematic for ( neat little phase-splitterless PP amp) amp?

Getting the want to play feeling again!



Regards
M. Gregg

 

[M Gregg]

This is what the amp i'm currently using would look like (approximately) if wired in triode. (i am just enjoying the system too much to bother pulling it down to fiddle with it at the moment)

An externally hosted image should be here but it was not working when we last tested it.

With suitable anode & cathode loads the 12AU7 could be a 12AX7 or AT7 or 6H1Pi (6N1P) or 6922 or ... with enuff drive off a pre or CD player the EL84 could even be used by itself in a spud amp.

dave

Dave,

What primary impedance o/p Tx are you using with this circuit, 8K ?

Regards
M. Gregg

 

[Yahnsolo]

Simple amp works fine!

There are tons of EL84 SE maps out there... i scanned thru what is on my HD and this one comes closest to what you want. You might need to juggle the PS for whatever trafo & rectifiers you have handy (or want to use).

Wired in Pentode SE it should put out somewhere between 3 & 4 W. Wire it in triode and it will drop to less than 2. I am currently running a similar amp (but with a 12AU7) and there is some real synergy between it and my BD-Pipes.

dave

Hi fellows,

Never late than never, this post is old ^^
I just made this amp and it works really fine!
All was made with scrap components, included an old dark unknown EL84 found on a old Ducretet Thomson radio that stayed outside for days.
So, i had lot of tubes, i used EZ80 valve, one choke for filtering, PC and phone charger psu HV caps, no "50hz" can be heard on the speaker, and no noise at all in idle.
Some resistors are near specifications, but all is ok!
Using 12AU7WA, or 12AX7SH for driver, both are ok.

Total drain current is 34mA

Thanks a lot Dave for your schematic!

I just wired a 24k as feedback from secondary output... As it worked, it seems to be nicely balanced and a very good bandwidth

 

[Alex1975]

Isn't the max voltage for EL84 around 250V? The higher voltage will not reduce the life expectancy of the tube?

 

[earx]

what speaker do you use with this amp ?
thanks

 

[earx]

hi another question fellow
does the first stage is enough in impedance and amplification for a vinyl player ?
thanks

 

[aardvarkash10]

hi another question fellow
does the first stage is enough in impedance and amplification for a vinyl player ?
thanks

no

 

[earx]

thanks, have a nice day
cheers

 

[earx]

yeah !
i test it again, since so many years, the sound is greater without the loopback
more clearer and punchy
do you have an adice on the loopback value ?
thanks

 

[earx]

After several hours of pleasure listening to norah jones, rock, jazz, whisplash and some porsche sound..
it was amazing but on rock sound too much of a mid, that the guitar outbreak the mix.
i'm going to test some values ont the loopback

 

[engel dela pena]

This is what the amp i'm currently using would look like (approximately) if wired in triode. (i am just enjoying the system too much to bother pulling it down to fiddle with it at the moment)

With suitable anode & cathode loads the 12AU7 could be a 12AX7 or AT7 or 6H1Pi (6N1P) or 6922 or ... with enuff drive off a pre or CD player the EL84 could even be used by itself in a spud amp.

dave

hello dave
any power supply for this one

 

[anystereo]

SET EL84 tube amp DIY project | Sarris Custom Tube Amps

I am working with an akai m-8 reel-reel, google for the schematic. It has two el84 output amps which are essentially the same circuit as Steve deckart’s zen. I love the design and the sound is astonishing. It’s right up there with my 45 & 300b amps and really shows what it can do with open baffle lowthers that are 96db/w. You can pick up this akai for really no money and go to it. I am so glad I looked past the skeptics and gave it a go. It’s been really rewarding