Single ended build questions

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Single ended build questions

Postby pinkmarkos » Thu Apr 02, 2009 9:29 pm

hello everyone- my name is mark and i am new to this forum. i am still a pretty new ampbuilder as i have only built two before. I have built a TW express clone (not from a kit), and a TW liverpool. The express is a PP 2xel34 power output, and the liverpool is a cathode biased 4x el84 type output. I love both of these amps but now I want to build a SE amp with 2 6v6's. I don't quite understand how to put this together so I need some advice please. Do I need two SE OT's for 2x 6v6's? Can I use any preamp with this type of power? Does anyone know of any good schematic/layout to use? Any advice would be much appreciated. Thanks!
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Postby Geek » Thu Apr 02, 2009 10:13 pm

May I ask why you want 2 x 6V6? Do you want a stereo guitar amp?

The Fender 5F1 is the definitive beginning building block for simple 6V6 based amps.

EL84 is a little hotter on output (being a 6BQ5 equivalent, where the 6V6 is an octal 6AQ5) and sounds different.... also needed a different Ra load for optimal performance.

SE OPT for a single 6V6 is typically 8K ohms, but some (like myself) like a 6.6K for a more crunchy OD.

SE OPT for EL84 is typically 5K.

HTH

Cheers!
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Postby pinkmarkos » Fri Apr 03, 2009 12:43 am

thanks geek, good info- well, for one, i was thinking maybe a 2x12 combo with one 6v6 for each speaker in stereo. but also simply for volume sake. if i did want to go the stereo route, can you explain in general terms how i could accomplish that? the 5F1 schematic shows 1/2 a 12ax7 for the volume/tone and the other half driving the power tube. so to double this, i would need one 12ax7 for the driver tube to both 6v6's (how do i split the signal?). and also two more dual triode type preamp tubes for the tone stack. i am definitely interested in a crunchier OD tone, so sounds like a 6.6K OT would be good. any more insight would be appreciated. i know i am coming across like a noob big-time, but i appreciate your patience. thanks- Mark
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Postby nyazzip » Fri Apr 03, 2009 1:09 am

i hate to chime in on stuff that i know nothing about(wait, thats not true), but, i think you are talking about parallel single ended designs...this link appears to explain it a bit:

http://www.tubecad.com/articles_2001/Accordion_Amplifier/

my hunch is, when you start merging two or more SE signals, the result might likely be no more "musically pleasing" and certainly far less efficient than a push-pull power equal, due to phasing conflicts both electronically and in the physical speaker movements, if you are using more than one speaker. but, i have wondered the same...
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Postby pinkmarkos » Fri Apr 03, 2009 2:26 am

nyazzip- thanks for the link, i glanced at it, but i am at work so i will have to wait to read the entire thing. the parallel SE design might be what i am looking for, i don't really know. At ax84, they have a design that allows use of any octal tube in a SE design, so with one el34 for instance you could get 10-12 watts (something like that). also at angela instruments, there is a 2x 6v6 SE design i might try. i would just build a champ, but i'd like to have a tone stack as well. I was hoping someone here would be able to share a cool schematic/layout of something they had built. i really like the tone of the 6v6, especially when overdriven, so this is why i am concentrating on this type of tube. i would, however, like a little more volume so i'm looking for a dual SE 6v6 design. thanks for weighing in! (y)
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Postby Geek » Fri Apr 03, 2009 4:31 am

Hi Mark,

We all had to learn somewhere ;)

pinkmarkos wrote:thanks geek, good info- well, for one, i was thinking maybe a 2x12 combo with one 6v6 for each speaker in stereo. but also simply for volume sake.


You'll gain a neglible 3dB that way. If you want volume, think 6L6... maybe a Fender Twin design?


if i did want to go the stereo route, can you explain in general terms how i could accomplish that?


Normally stereo is done with two heads and two cabs (or two combo's) and a stereo chorus stomp.... or a stereophonic pup.

Cheers!
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PSET 6V6s ?

Postby EWBrown » Fri Apr 03, 2009 10:57 am

Angela Instruments has a parallel SE 6V6 guitar amp project here:

http://angela.com/angelasupersingle-end ... oject.aspx

the basic schemo is:

Image

Note that there is no CT shown on the HV secondaty, that should go to the ground buss.

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Postby Geek » Fri Apr 03, 2009 4:34 pm

Thanks Ed, I didn't know about that one! :)
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Postby pinkmarkos » Fri Apr 03, 2009 9:40 pm

hello EWbrown- yes, this is the schematic i was looking at originally that inspired my idea about the SE dual 6v6 amp. thanks for the point about the center tap, i don't think i would have caught that. i think i will probably go ahead and build this one. i will just have to design some type of tone stack into the preamp section. thanks again- mark
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Postby dhuebert » Sat Apr 04, 2009 11:11 am

Here, build this:

Image

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Postby pinkmarkos » Sat Apr 04, 2009 3:58 pm

looks pretty cool dhuebert- how does it sound?
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Postby dhuebert » Sat Apr 04, 2009 4:35 pm

No Idea. I've never built one.

Having said that; this is a starting point.

I know the front end works because I've used it in a couple of other amps. There is alot of room here for experimentation. You can switch capacitors in and out of the first cathode to do gain and tone shaping. You can put attenuators between the first stage and the volume pot to control overall gain and harmonic mix. (this is really REALLY simple stuff). You can go to www.duncanamps.com and download their tone stack calculator and play with capacitor and resistor values live to customize the tone stack. You can play with the gain of the recovery stage to control the mix between the harmonics generated in the preamp and the output amp.

I didn't include feedback but there are a couple of points you could tie into to do more tone shaping with feedback.

There are a couple of places in the circuit to try different kinds of resistors to add harmonic content. ( carbon composition are supposed to be non-linear)

Different 6V6s give radically different sounds when driven into clipping.

There are lots of output transformers to try, including the ones in All American Five radios. If you could find a tube radio that has a single 6V6 ouput tube and a power transformer, it would supply most of the expensive parts for this project.


BTW: A good way to prototype.

Image



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