My brain hurts

[lovedat800]

This amp building stuff is probably best left to real techs ! First i was going to build a 36 watter after i realized my 18 wasn't clean enough at volume. Then i started realizing the bass and treble issues i was having were probably due to the el84's, so i tried 6V6 in my 18 and that helped. So i figured i'd build a 36'er but use 6V6 and just do the 2 or 3 changes necassary to adapt that design to the 6V6's. Then i started hearing about how 6V6 's can be flabby, and i recall playing several 6v6 fenders that were like that and sounded like $#@&. Plus i began to realize my 18 with 6V6 at volumes was sorta brittle sounding and not enough compressed feeling. then i realized by looking at some weber schematics that my new heyboer 4k OT could be used with a duet of el34's, may fav tube. So i then decide to go that route. Now i find i can't use it because the wattage is to low and the OT may fry.

So at this point i'm just plain disgusted and i'm considering going back to square one and using the 84's after all. Yup........my fruging brain is in serious pain.

[leslie]

Hey Lovedat ,it supposed to be fun.
It's simple electronics,but people have tendency to complicate things.
Slow down and build when you have desire.



Here are trannys:

http://www.ampcomponents.co.uk/transformers.html
http://www.thevintagesound.com/store/tr ... a37266fb07
http://www.thevintagesound.com/store/tr ... a37266fb07
http://www.maplin.co.uk/module.aspx?C=S ... ransformer

[lovedat800]

I don't need to buy another OT, just a PT and hammonds are cheap and extremely varied. So thats not the issue. I just need to figure out what to build with this OT because one way or another it's the one i'm using. I have 3 choices that appeal to me in one way or another. The 6v6 or el84 quads, or a el34 duet. problem is i'm just not a tech and there are so many questions before i can start building that i can never find the answers i need. So like i said, i'm probably going to just go with the 36 watt el84 PA after all. I hope to make a firm decision and begin ordering parts within a few days. (fingers crossed)

[davent]

I'll be devil's advocate here, how 'bout a pair of 84's and a pair of 6V6's?

dave

[Alexo]

I can drive myself mad with indecision on a build when I start getting into "what can I build with these two transformers I've already bought?" trains of thoughts. Seriously, maddening, too many options, yet no one option seems like it's quite right. What helps me is to take a step back, look at the build as more of an experiment, rather than an attempt to build the greatest amplifier that has ever roamed the earth.


PS - why don't you just sell your OT and build your JCM800?

[lovedat800]

For one, i really don't want to sell it and i think i can use it for several designs. As for the 800, it's not so much that i want an 800. if i did i'd probably just buy one. I want a amp with that *general* sound and gain structure. (i do love them, but they aren't exactly what i want) My perfect amp would sound similar but would have a rounder tone thats more complex and thats not friggin loud. the 800's are great when you get a good one, but they are just a starting point for me. thats why i began this thing in the first place. Because i know that uncluttered circuits with good components and transformers can sound super rich and complex unlike most any production amp. Add that to the fact you can tailor it to your preferences and thats the reason i'm driving myself crazy with this stuff. But anyways, i'm using that OT.

[Oldschooltone]

The 6v6 will give you what you are wanting in tone, I would change to a GZ34 or go solid state.
I changed my 18w lite IIb to 6v6's and love the tone though I am using an AC/30 PT and pushing about 390+v my tone is not flabby or brittle and one of the speakers in my 2x12 is a G12M Greenback so forget about the Fender flabby.
I also am a big 800 fan, I've owned two 2204 50watts and one was hot rodded by one of those go to guys $$$ in the 90's and I would not trade for what I have now, you can look at the schematic of the amp in the gallery section.

[leslie]

What helps me is to take a step back, look at the build as more of an experiment, rather than an attempt to build the greatest amplifier that has ever roamed the earth.

I agree with you Alexo,process of learning/building and experimenting makes me happy.
I wouldn't do it if it's other way.

Good or best is just byproduct of the factors in process,IMO.

[AndrewR]

I don't know what the exact specs of your transformer are, but with an 8 ohm load it will have a specific primary impedance (anode-anode). It will have half that impedance with a 4 ohm load and twice that impedance with a 16 ohm load. (I'm assuming it has only one secondary winding, but I don't know that for sure). Different power tubes require different loads for optimum performance, but they also require different loads depending on the voltage you're running at and different loads for different classes of amplification and different loads for triode or pentode operation. Yes, I'm not surprised things are getting confusing. However, an absolutely exact impedance match is impossible anyway because 8 ohm speakers aren't 8 ohms at all. The impedance at the cone's resonant frequency will be much higher than 8 ohms (maybe about 40 ohms) and that depends very heavily on the design of the speaker cab. The impedance at high frequencies will be much higher than 8 ohms, too. So now things are getting even more complicated. Is it all impossible? No. Just don't get too hung up on ideas about absolutely right or absolutely wrong. There's theoretical perfection, then there's the real world.
Check out some tube manufacturer's data sheets. They're usually very helpfull and not as complicated as they seem at first.

http://www.drtube.com/tubedata.htm

[zaphod_phil]

Then i started hearing about how 6V6 's can be flabby, and i recall playing several 6v6 fenders that were like that and sounded like $#@&.

That's because they were probably either Fender amps or of similar design. So you would have cap sizes in the preamp that were too large, as well as those 0.1uF caps coupling the PI to the power tubes. There's a recipe for flabbiness if there ever was one! When you build a Marshall amp with 6V6s you get something completely different.

[rjgtr]

I like to use .047 or .022 coupling caps with 6V6s. That makes the amp a lot tighter.

For a just slightly off topic example -

I recently converted my 1987x 50 watt to a full turret board and replaced the OT with a Heyboer. While doing so I used the bass layout because I like Jeff Beck and Duane Allman, who were known to use the bass version. This used .1uf coupling caps in the power amp. I played it for a few weeks and then changed them to .047s and like the amp a whole lot more.

[lovedat800]

Ok, then let me ask you this Phil. I love plexi tone. Possibly my favorite tone. BUT, they're too loud and even a 6V6 one would be too loud if i built it with 4 6V6 to get the headroom i need. So is there a version of the 6V6 plexi that someone has built for more gain that i could build and just use and just build my 4x6V6 PA into it? I suppose the PA part of it is easy....just use the right trannies. But i need more gain. i don't need a ton of gain like i have with the 18, but i need some preamp drive, not just output drive. Putting in a master is no problem, but i'm sure the standard plexi doesn't have enough gain in the pre to get much drive even with a master. So i guess the question is, has anyone done this and been able to retain the plexi tone? I understand part of it is the power amp so it's going to be different, but maybe i should word it different....has anyone done this and kept the plexi "voice".

So in short i'd consider a 4x6v6 plexi with about as much preamp drive as a jcm 800 with the pregain knob on 2-3:00 at least. Any options for something like this?

[Bulatovic]

Well - not being near to any expert - what i think you could do is put switch between the plexi and JCM800 - on plexi you'd have standard cathode on v1 while on the jcm channel you would have 10k which would produce that chainsaw sound and more preamp distorsion. Also you could maybe add a PPIMV instead of the regular jcm master. But that 4x6V6 will be loud! Very loud! properly! (why not doing it with a pair of el34 then?)

[pjb]

Ok, then let me ask you this Phil. I love plexi tone. Possibly my favorite tone. BUT, they're too loud and even a 6V6 one would be too loud if i built it with 4 6V6 to get the headroom i need. So is there a version of the 6V6 plexi that someone has built for more gain that i could build and just use and just build my 4x6V6 PA into it? I suppose the PA part of it is easy....just use the right trannies. But i need more gain. i don't need a ton of gain like i have with the 18, but i need some preamp drive, not just output drive. Putting in a master is no problem, but i'm sure the standard plexi doesn't have enough gain in the pre to get much drive even with a master. So i guess the question is, has anyone done this and been able to retain the plexi tone? I understand part of it is the power amp so it's going to be different, but maybe i should word it different....has anyone done this and kept the plexi "voice".

So in short i'd consider a 4x6v6 plexi with about as much preamp drive as a jcm 800 with the pregain knob on 2-3:00 at least. Any options for something like this?

Fundamentals:
Plexi tone = EL34
EL84 = miniature EL34

Why all this talk about making a 6v6 sound like a plexi?
A 6V6 is closer to a miniature 6L6 than a big bottle EL84.

Not even 6550 gets plexi tone. At a push you could say KT66 a-la Beno album Bluesbreaker, but then that is not "classic" plexi tone that's "Claptone") look at the Metro replicas... now those get plexi tone... and they're not that loud.
IMVHO.

-Paul

[lovedat800]

Why all this talk about making a 6v6 sound like a plexi?
A 6V6 is closer to a miniature 6L6 than a big bottle EL84.

EL84 = miniature EL34

thats what i always felt too. But here i keep reading how they don;'t and how 6V6's do. i always felt el84's had a similar tone to el34's, tho i would argue that they sound almost exact. there are certainly differences. But the main reason i wanted to get away from them is that i have experimented so much with my 18 that it's been about 20 different amps so far and the highs were slaughtering me no matter what i did. My belief at this point is that manufacturers use trannies that are designed to work well in a balanced manner with 84's because all of the 84 amps i've owned and played are not brighter than any other amp. yet mine is a freakin treble fest, and everyone here keeps telling me thats the way 84's are. So thats wht i'm gunshy about using them fro the next build. But as i already said, i may anyways because i keep running into hurdles with el34's. Not that it can't be done easily, but i don't know enough to pull it off safely w/o much chance of another flop.

Not even 6550 gets plexi tone. At a push you could say KT66 a-la Beno album Bluesbreaker, but then that is not "classic" plexi tone that's "Claptone") look at the Metro replicas... now those get plexi tone... and they're not that loud.
IMVHO.

I don't think anyone is talking about *exact* plexi tone. At least i'm not. I'm talking as close as possible given the needs i expressed.

[leslie]

Maybe TAD EL84 would be best of both worlds?
4x6V6 seems to have a lot of bass,but this one is sounding really good to me
http://www.youtube.com/watch?v=TWeEnS0wsVo
Thanks _Phil for sharing

[rjgtr]

IMHO, neither of the two, EL84 and 6V6, sound exactly like an EL34. The 6V6 is closer to a KT-66 to me. The EL-84 is brighter and crunchier than the EL-34. The thing the 6V6 has over the EL84 is a bigger bottom end, probably because it's a bigger bottle.

Having said that, I've gotton good results from both 6V6s and EL84s at getting close to a 'plexi' tone (and even a Hiwatt tone). The preamp voicing has a lot to do with it. The classic plexi tone is a combination of preamp and power amp distortion, both in moderation.

[pjb]

Not sure I'd go for bigger bottom end for Plexi tone. I'd say the lowest should be lower mid-tone at best.

What I've noticed is that the smaller bottles generally have a tighter low end which I personally think is due to a harder vacuum. The bigger bottles can't develop such a hard vacuum because there is too much space to be evacuated. The old skinny Amperex 34s seem to have that tighter harder vacuum tone... and of course I'm using my imagination to describe something I hear going on with the smaller bottles.

-Paul

[lovedat800]

I just got my email reply from heyboer as to the wattage the OT can handle. I was more than pleasantly surprise to hear them say 50 watts. So EL34's shouldn't be a problem now. I believe i may go that route. I will need a lot of advice tho, so if anyone knows of the best forum to ask for guidance when it comes to EL34's, please tell me. Wish i could post here, but i know it's frowned upon to post about other designs.

EDIT: sure enough i done gone and ordered the parts for a EL34 build. Gonna be a somewhat low voltage PA with cathode bias, no nfb, a tube recto and a JCM 800 style cascaded pre. So basically it should be, and i'm HOPING it will be a killer sounding JCM800 with more squish and harmonics and a lower volume sweet spot. Or in simpler terms, the amp that has the sound i've always had in my head. If i get even close i'll be thrilled. Crossing my fingers that i don't have another issue like with the 18.

Anyways, guess i won't be posting in the 36 forum anymore, tho i'm keeping the 18 on the bench as an ongoing experiment and learning tool so i may be posting there now and then. I'll throw a hammond OT in it to replace the blown heyboer and see what i can learn from it and get out of it tonally.

By the way, to the mods....anyone ever consider a sort of general building section where we could post about any kind of build?