2xel84 vs 4xel84 low end

[leroy]

Hi

Long story short. Built lots of amps. love el84's. Don't like the lack of bottom end authority/feel.
Tried the same circuit but with octals el34, 6l6gc etc.. Nice bottom but no EL84 tones.
All else being equally does a quad of el84's have better low end than a duo? Differences in headroom or loudness don't concern me.

I don't want to go to the expense of buying the transformers and building it only to have it sound virtually the same.

The circuit in question is just an 18 watt lite iib /stout variant.

Thanks
Leroy

[Leevi]

Have you tried to change coupling caps in the preamp? Based on my experience a pair of EL84 sounds pretty similar as a quad  of EL84.


/Leevi

[leroy]

Yeah i've tried every thing. fixed bias, Negative feedback etc..
It's not about increasing the bass of the 2xel84. its about 2x vs 4x.
There's a lot spoken about the 50 vs 100 watt plexi's not so much for el84 powered amps

Leroy

[pdf64]

I think that generally, lower power / SPL dB levels are perceived as less bassy. On one hand it tends to take more power to push bass out of cabs, due to them being less efficient at that end of the spectrum. On the other hand, Fletcher Munson showed that the frequency balance we perceive changes with SPL; hence the 'loudness' switch on audio gear (I guess it's built into software these days    ).
And on yet another hand, traditionally lower power amps, eg typical 2xEL84, tended to have a lower spec for their OT etc than higher power amps, eg may be characterised by student grade gear compared to professional grade gear.

...
There's a lot spoken about the 50 vs 100 watt plexi's...

Could you summarise that?
My take is that the paralleling up of the power tubes there is trivial, a key aspect of the difference is due to the power supply 'beefiness' not increasing by the same ratio.

[SILVERGUN]

Have you ever thought of designing around  mixing output tube types?
I hadnt until you posted. Well, actually, I had tried it in SE but never thought to look into PP.
Im sure someone has done it.

[tubenit]

You can mix EL84's and JJ 6V6's easily using cathode biased.  I think those JJ 6V6's have very nice bass response.

With respect, Tubenit

[shooter]

fwiw;
I did a quad 84 audio build, ran them into a pair of Audio Nirvana 8".
was a great stereo but even with the high spl speakers, the amp tweaked as good as I could then,  I was not totally happy with the Bass

[Ed_Chambley]

Sure, Carr has a mixed tube amp.  Egnator had the ability to mix 6v6 and El84's.  Brass Tacks, no way!  What I mean is EL84 tubes in an AC30 sound exactly like an AC15 when distorting, but do have more harmonic content.  Keep in mind, many home console tube stereo units were EL84 and a lit of DIYers still build them.  It is cheaper too.


I believe once you have felt the air movement from a Marshall and 4, 12's, we somehow become convinced we can make the same thing only smaller.  I tried what you are trying until I finally built 2 amps.


A Princeton Reverb with a JBL 12.  This amp is the "wet" amp.  Modulation.
And a Sluckey's AC15 with the EF86 head with a CLOSED BACK cab and a Celestion Blue.  This amp breaks up much easier and also gets distortion/overdrive, but closed back is needed to get any grunt out of it.


I agree the JJ6v6S tube has the best bass response.

[leroy]

I think that generally, lower power / SPL dB levels are perceived as less bassy. On one hand it tends to take more power to push bass out of cabs, due to them being less efficient at that end of the spectrum. On the other hand, Fletcher Munson showed that the frequency balance we perceive changes with SPL; hence the 'loudness' switch on audio gear (I guess it's built into software these days    ).
And on yet another hand, traditionally lower power amps, eg typical 2xEL84, tended to have a lower spec for their OT etc than higher power amps, eg may be characterised by student grade gear compared to professional grade gear.

...
There's a lot spoken about the 50 vs 100 watt plexi's...

Could you summarise that?
My take is that the paralleling up of the power tubes there is trivial, a key aspect of the difference is due to the power supply 'beefiness' not increasing by the same ratio.

I've seen stuff from Kevin O'Connor were he talks about something like the gm is halved. He has a project called the 5100 which is a 4 x EL34 which runs at 50watts. The idea is you get the sound of the 100 watt but at 50watts. It's all above my head to be honest.

I've thought about mixing 6v6 and el84. But when ever i've replaced el84 with 6v6 the bottom end hasn't changed that much. The over tone becomes smoother though.

I've read with the Egnator that can change between both sets that the change isn't that much.

I have the PT and OT for a 50watt plexi so i might just try the mix. If i don't like it i can change the sockets to noval and run 4 x el84.

Thanks
Leroy

[HotBluePlates]

... love el84's. Don't like the lack of bottom end authority/feel.
...
All else being equally does a quad of el84's have better low end than a duo?  ...

Well, "all else" is never equal.

I've got a '65 AC10 Twin (stock with 10" speakers) and a '63 AC30.  I also have a 2x12 cab that I've put some silver Celestion alnicos in (but also open-back).

Playing the AC10 through the 2x12 cab pumps up the low end considerably.  Though my AC30 has yet more low end. Partly due to 4x EL84s vs 2.  But also partly because there are the old blue Celestions in that amp.  And also partly because the because the Woden transformers are pretty huge in that AC30.  But then again, partly because it's an AC30/6 Bass model that doesn't have all the low end shaved out.

So depending on the circuit & speaker you're using, you will get some extra low end authority by doubling-up output tubes but you're probably not changing the core sound.  I'd say your choice of speaker will make very much more difference.

[tubeswell]

...I'd say your choice of speaker will make very much more difference.

And the size of the OT

[leroy]

Well i have currently in stock three OT's to try.
Classictone 18watt
GDS Heyboer 36watt
Classictone 50watt Plexi/800

As far as the speakers i use.
4x12 Marshall with pre-rola greenbacks.
The sound is 90% there. Just missing that last ingredient. 

[brewdude]

I had a Mesa Blue Angel for a while... it offered 3 modes—2x6V6, 4xEL84 or both at the same time—I liked the El84’s least and both simultaneously best.  I never really bonded with that amp. 

[Bieworm]

Hi

Long story short. Built lots of amps. love el84's. Don't like the lack of bottom end authority/feel.
Tried the same circuit but with octals el34, 6l6gc etc.. Nice bottom but no EL84 tones.
All else being equally does a quad of el84's have better low end than a duo? Differences in headroom or loudness don't concern me.

I don't want to go to the expense of buying the transformers and building it only to have it sound virtually the same.

The circuit in question is just an 18 watt lite iib /stout variant.

Thanks
Leroy

Built some 18 watts. The TMB tremolo and a classic with tremolo. The classic has REALLY got bottom. But to get there I had to swap them 2 x 4n7 in series caps of the preamp of the trem channel into 2 x 22nf caps. In fact it was so boomy I changed them to 10nf and now it's as boomy as my vibro king.
Speaker should also be a g12h30 on an 18 watt. But thát you'll know already I guess?