15BD11A....

[TIMBO]

Hi guys,
Got a heap of these...
6BD11 (pocnet.net)
Worth a headache....

[uki]

It is a very interesting tube, 2 triodes and a pentode !
Have you found any schematics with those tubes?

[PRR]

All your eggs in one basket!

[tubeswell]

Have you found any schematics with those tubes?

A 1-tube SE 'micro' amp (with SS rectifier) I guess

[darryl]

Other than heater requirements, the 15BD11 is similar to the 6AF11, which has been used in a simple one-valve amplifier.

http://solorb.com/elect/musiccirc/squirrelmonkey1/

I've experimented with the 6AF11, but could not eliminate unwanted oscillation when using all three valve sections.

[TIMBO]

Thanks darryl.
I saw that some time ago.
So maybe a push pull with two valves??

[darryl]

So maybe a push pull with two valves??

I haven't tried it, so I won't offer possibly inaccurate advice. Maybe you could pick up the baton from here ?   

[PRR]

IMHO, the best use of that tube is 2 or 3 *different* things. Not an audio amp cascade. The intended use was TV video driver and sound interchannel (IF) gain and a third function as needed. So you don't have gain of 30*35*60= 63,000 all in one bottle. Which is bound to squeal.

[TIMBO]

Thanks PRR.
I'm thinking push pull and only using one of the triodes similar to 6GW8 6BM8 and 12a_7 preamp duties
Any idea what the output of the two pentodes would be?

[kagliostro]

Ciao TIMBO

15BD11A (6BD11) .....

http://www.mymorninglight.org/ham/15BD11.HTM

Unfortunately not an audio amp

BUT .....

https://zeppelindesignlabs.com/product/percolator-2w-amp-kit/



https://www.zeppelindesignlabs.com/wp-content/uploads/docs/Zeppelin_Perc_ASSEMBLY%20INSTRUCTIONS.pdf

https://music-electronics-forum.com/forum/schematic-requests/52075-





---


Some time ago I developed a Layout for this amp
(to be revised and also I don't remember if I followed exactly the upper schematics)



May Be the schematic followed was this .... may be 



---

So maybe a push pull with two valves??

May be here you can read something of your interest

https://el34world.com/Forum/index.php?topic=15489.msg149480#msg149480


---


I'm near sure our friend DummyLoad did something about a PP 6AF11 amp

Franco

[uki]

With 2 tubes maybe you could make a push pull, preamp \ PI \ power push pull
Something like 5e3.

[kagliostro]

Ciao TIMBO

I hope this is of your interest

As I actually remembered a PP diagram with relative layout for the 6AF11 tube was made by our friend DummyLoad

and here is attached both the diagram and the layout, if you want there is also a .vsd file that you can possibly ask to post, if interested





Franco

[TIMBO]

Thanks Franco

[DummyLoad]

Just to clarify, that what K posted was a concept and was not built. If I were to build it today, I'd use one of the hi-mu triodes (V2) for a trem oscillator and the remaining 3 as gain stages + cathodyne for the phase splitter. Should be low-ish enough cascaded gain to function as a mostly "clean" 4 watts, give or take, if you can even consider a 4 watt guitar amp suitable as "clean sounding."


--Pete

[kagliostro]

Ciao Pete

Many Thanks for the clarification

Also I've interest on the compactron use

Franco

[TIMBO]

Thanks for the input guys.
I'll start collection some parts....
HMMmmmm, 12pin sockets..... can't find any local on ebay
 

[kagliostro]

Ciao TIMBO

On the bay I've find a pair of NOS very expensive (~15.00$) sockets

This seems more affordable (at 2.50$)

https://www.tubeaudiosupply.com/products/ceramic-12-pin-compactron-socket-bottom-mount

Here is one other source, a bit more expensive 4.95€

https://www.tubeampdoctor.com/en/compactron-12-pin-for-6c10-6k11-etc.-ceramic

Here a PCB version

https://www.ebay.it/itm/162366561767

Other ones for chassis

https://www.nocrotec.com/shop/product/b12c-duodecar-compactron-tubesocket-ceramic/?lang=en

https://talonelectronics.com/shop/item.aspx?itemid=14028

https://www.ebay.com/itm/173482360764?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338722076&customid=&toolid=10050

https://www.ebay.com/itm/202955069077?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338722076&customid=&toolid=10050&amdata=enc%3AAQAHAAAAkH1Q6d%2BTPZQn%2BvEDTwgZZP%2B30MeqBCa3x%2BybCGZFSOMIGau8lbppI7EJKsfRRinPQGtl%2FTaP1C9iP7V0YhQZAYJcOdO79C0v8XnwXoLQ2R4yRFWH7TcnbPtK6NsCslejk1mdG%2FhDSxDKyUHKadqTUtfKZ2IaqX%2F4LhCJ69MwdMk1A218qKIIhprAEnRHqumwhw%3D%3D

https://www.ebay.com/itm/354100042504?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338722076&customid=&toolid=10050

You can also ask here, I'm near sure they have it

https://www.francoborgia.com


you must contact them also if the item isn't on the web shop, I got 2 or 3 of those sockets there

BEFORE to buy enithing verify if the socket you are trading for is compatible with your kind of compactron tube

Ciao

Franco

[DummyLoad]

Thanks for the input guys.
I'll start collection some parts....
HMMmmmm, 12pin sockets..... can't find any local on ebay
 

maybe not in NZ, but closer to you relatively speaking?

https://www.ebay.com.au/itm/294743575372?hash=item44a0160b4c:g:iUMAAOSw3~5h54LU&frcectupt=true

[kagliostro]

I think the problem is here

AU $8.95
Each additional item Free
Australia
Standard postage (Australia Post Standard Parcel)

Franco

[thetragichero]

just find a ton of stuff to order from em and the shipping won't matter
that's at least what i tell myself when making parts orders 

[kagliostro]

Well, but 4.5AU $ x 2 + 8.95AU $ is 17.95AU $ for a pair of sockets, not very cheap indeed


Franco

[shooter]

not very cheap indeed

the common phase about ANYTHING these days, regardless of location!!

[kagliostro]

Unfortunately you are right

Franco

[TIMBO]

A simple circuit to start with.
Back to back transformers to be able adjust the HT voltage and a good 15/12v heater supply.
Bread board under construction.

[kagliostro]

Step by step another brick in the Wall


👍


Franco

[TIMBO]

[kagliostro]

Being a PP the space engaged Is more than aceptable

We are waiting for further developement

Good job

👍👍👍

Franco

[DummyLoad]

PS node "D" has no connection...I presume "D" is plate supply for V1a?

--Pete 

[TIMBO]

Hey Pete, Yes ATM
It's just about wired up, so should be interesting 

[TIMBO]

Hey guys, The initial fire up was good, adjusted the pentodes cathode resistor to just under 4w diss.
Got good guitar sounds a bit low on volume and a squeal at max volume.
So I'll take the squeal as the "oscillation" that could occur with these valves.
Tried a heap of fixes with no good result...
Swopped triodes on the input and ST recovery so it's now  HI MU- TS- LO MU- HI MU Phase inverter.
Now plenty loud enough.
Still the the oscillation persists.
Changed the taps on the PT's to around 170v on the pentodes plates and also changed the plate load as well, no change.
The overall sound was much better at a higher HT this time with a plate voltage of around 250v.
Adjusted the cathode resistor to just under 4w plate DISS
Even though the squeal persisted the amp sounded great.
I felt the preamp voltage were a bit low and causing some distortion and up setting the pentodes.
I changed the 10k dropping resistor to 3.3k to up the pre amp voltages and at this stage the oscillation had stopped, I can now get max volume with out the squeal
 
All voltage look good.
Also I think 16k plate load is good for these valves???

[TIMBO]

Hi guys, Wet day in Brissy time to do some metal stuff.

Found these C channel offcuts on a job site and are perfect chassis.
They measure 152x50x 1mm thick, I haven't found a source to acquire more ATM.
So a bodgy folder was constructed..


And a perfect 60deg angle bent.
So a 5F1 chassis was bent at the same time.

[TIMBO]

Hey guys, Construction continued...



Wiring almost done...
Would have finished, if I didn't run out of solder.....

[kagliostro]

Ciao TIMBO

Nice, did you paralleled the triodes or you have an unused  one ?


Franco

[TIMBO]

Hey mate,
There is one unused.

[kagliostro]

An oscillator as told DummyLoad ?

Franco

[TIMBO]

Hey guys,
I think I have given this one the good old Aussie crack (go)
As previous explorers that ventured before me found that not all Valves/Tubes are meant to be used in guitar amps.
Overall the amp sounds reasonable with some early breakup, not too flabby but quite bright.
High frequency oscillation is a the main problem as we already knew.
I have spent much of the day tweaking this thing to death, you name it, I tried it.


Long story short...
The oscillation (squealing) only kicks in if the treble pot is turned to max and the volume also turned to max.
With all settings set at half way, there is some decent guitar sounds.
Thoughts....
 

[TIMBO]

Hey guys, This is where I'm at...
As I said I have tried a bunch of stuff and the oscillation persisted.
The primary impedance was an unknown and 16k was a start, whit the OT I have allows for multiple primary's.
8K seem to sound the best with some of the other primary's causing some oscillation.
Some further tweaking and negative feedback was added and the oscillation was under control.
Not knowing what exact amount of feedback was needed so a 100k pot was used
So at this stage the amp is behaving.....

[TIMBO]

Thanks shooter, I may have spoken too soon   
I believe these valves are fickle and doesn't take much to upset them.
The adjustable negative feedback does help, but only to a certain point and also having the speaker on a certain tap of the OT, if this makes sense.
Other tweaks also help, but to some degree it's all too unstable to be a reliable working amp.
So off to the cupboard of the "ones that almost made it"

[shooter]

it's all too unstable to be a reliable working amp.

who knows, in this new world there's probably a snot-nosed kid that might think it's the next great sound 
my shelves were full of ready spares.