Seven pin Pentode preampreamp Anyone?

[PlumMojo]

So some of you more experienced gents out there willing to help with some ideas and schematics/ layouts for a 7pin preamp circuit?

I got a beautiful 60s organ with a few seven pin sockets.

In my books by Mr Merlin he speaks on designing with them,I would love a schem/layout for a few.

6au6 is ef90 I believe.   And I bet if the ef86 was used as the second stage it would not be microphinic with the right biasing.

So  any and all info will be wonderful and well taken

Thanks guys!

[kagliostro]

Maybe this can be of your interest



Here documentation and samples
http://bensykora.com/7cylinder.html


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Other stuff


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Here documentation
http://grandpaslab.com/theaviatrix/

Franco

[PlumMojo]

 

Dang!!keep em coming!!

That's cool 6j6 phase splitter.

Wowzers! Oh boy it's beginning to look alot like Christmas!

Thanks so much!!!!!

[kagliostro]

Glad you are interested

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I added some other stuff to the previous post

Franco

[PlumMojo]

Do you know much of the 6j6?

Dual triode in there.

I bet some cool stuff can be done with it.

I wonder how it stacks up to the 12a_7?

I love this !!

That's some good stuff there.

I hear that some of those 7pin tubes really impart alot of Tube coloration upon the guitar signal.

And that can be a really good think.

I am beyond pleased by this!

[kagliostro]

6J6 ? ......

To me the principal defect is the common cathode, I don't think it can be used with satisfaction as two separated gain stages

much better to use it as a single triode (parallel Plates and Grids) or, as shown in the schematic, for a PI (that is a Paraphase PI)

Franco

[PlumMojo]

Thanks, so I'm merely learning ,more or less shooting in the dark here,so I'm just asking.


Thanks so much

[kagliostro]

Other 7 pin amp

http://ampgarage.com/forum/viewtopic.php?f=6&t=30555



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http://ampgarage.com/forum/viewtopic.php?t=28239

Franco

[PlumMojo]

Sweetness!

[Glenn]

That last schematic.... I wish David put his name on that schematic he drew, since he is no longer with us.
Great little amp!

[PRR]

> I hear that some of those 7pin tubes really impart alot of Tube coloration upon the guitar signal.

Not to poke a pin in your imagination, but.... I don't see how the number of pins has much to do with "coloration", or in that way.

Many of the 9-pins are pretty-much two of the 7-pin guts in one bottle.

Except along the way those guts were "hot-rodded" for better spec-sheet numbers, which incidentally increased nonlinearity and "color" just a little bit.

To my eye, the 7-pins are just more work to build a complete amplifier. However some of them were VERY common and still cheap.

[brewdude]

I don’t know if there is anything special or not.  I happen to score 25 of the the cute little 5725 pentodes for about $20. Not really knowing anything about them or what to do with them, I started looking for other 7-pin tubes.  I thought that designing a whole circuit using 7-pins would be an educational exercise.  When I found a Gibson schematic that used two successive preamp pentodes and a large choke in CLC filter as well as a small choke on the screens I was hooked on this project. 



I like the “puzzle” of building amps and tend to avoid well established designs in favor of somewhat quirky and esoteric circuits.  The problem is that being unfamiliar circuits guitar players don’t know whether they are supposed to be desirable or not and are unwilling to pay enough to cover costs of materials let alone labor. Good thing I’m not in business selling amps. 

[PlumMojo]

Well it's the fact that there may be some rarely used tubes that may be a bit differnt than 12ax7 that's all I was getting at.

Now I am not in any way shape or form educated in any electrical or valve way.

So it's not nearly a hit to my ego /imagination or forum splendor that you get a kick out of my exposing the fact that i dont know that much about amps/tubes/electrical things.

So i was simply curious about differnt tubes and how they impart flavor upon the sound they produce in the amplifier circuit.


Brewdude, I enjoy the puzzle too thats all the fun of it.

Bcuz I don't know the half of it and learning is the fun

[shooter]

in favor of somewhat quirky and esoteric circuits.

I came up with this one, didn't update the schematic, or even finish it, the amp worked well, guitar guys thought it was a great grunge amp

[PlumMojo]

Dang that's cool man! Thanks

[brewdude]

in favor of somewhat quirky and esoteric circuits.

I came up with this one, didn't update the schematic, or even finish it, the amp worked well, guitar guys thought it was a great grunge amp

Is that triple SE?

[shooter]

 

I've only built 2 PP amps, but SE, I've done out to QSE

EDIT: like I said, I know the PS was re-work, but that was before my good note taking days

[ckilgore]

Here is a simple SE amp I built a few years ago using a 6AU6A (I also dismantled an old organ and have many of these) and an old radio chassis, its PT, power supply, 6V6 and OT.  Sounds great.  Note: you could replace the 6V with a 6AQ5 and have a 7pin output section as well.

[DummyLoad]

i penned and built the two circuits on my breadboard that are attached circa 2011. rev. 1 had a lot of potential on the breadboard. with this experiment i gained considerable knowledge of which 7 pin valves worked better for audio.


as far as 7 pin pentodes go, the sylvania 6136's are the ticket. another 7 pin pentode i tested is one that slucky pushed my way: the 5654 (6AK5). both sounded good but the 6136 has an edgier tone that i was looking for. as i recall, the 5654 was smoother sounding overall. i have not tested a 6AK5


i built two versions: rev 1 used 2 x 6ABB4 (each 6AB4 is half of a 12AT7) for the long tail phase inverter. rev. 1 has a complement of seven tubes, hence the name lucky7; rev. 2 used 6J6 for the LTPI with mixed results since most of the 6J6 i had on-hand at the time were just too microphonic. rev one sounded much better.


you could sub a pair of 6AV6/6AT6/6BK6 for the 6AB4s without modification to the circuits. the 6AV6/6BK6 are half 12AX7 and the 6AT6 is half 5751.

it's basically a 5e3 front-end of sorts with a deluxe-ish LTPI and output stage. the PS is relatively inexpensive to build: even more so if T-1 is 120V single primary. alternate PT selections in the notes.



--pete

[PRR]

> circuits on my breadboard that are attached

Voltage charts go up to pin 9. Voltages don't look right.

[DummyLoad]

> circuits on my breadboard that are attached

Voltage charts go up to pin 9. Voltages don't look right.

foes it matter?