"Little Wing" Mini-Bassman w/ 6BM8 tubes

[Geezer]

Here's the schematic to the most excellently toneful ~7watt amp. EH now has the 6BM8 tubes available again. The bonus is that there is a triode in each power tube that can be used for other purposes. I used them for the PI in my design.
This unit has been built & is currently my main "small venue" gigging amp.

Sound clip of the Little Wing :  http://www.musicwebtown.com/jallenshaw/46763

Geezer

[Geezer]

Hmmm.....I just noticed that the recto I had in there for the voltage test was a 5Y3, and the sound samples had the GZ34 installed.
I just checked the plate volts w/ the GZ34 & it's ~320v.
The "cheap" ($20/China mfg) Weber PT is probably not producing "exactly" the spec'd output of 260v. With a "real" 5Y3 I would "expect" a voltage of ~286....so we're not too far off, and the loading/biasing of the 6BM8's could also be affecting the resulting voltage.
BTW, I like the tone better at the higher voltages. I have a SS module that I made up to plug into the recto socket & personally prefer it over even the GZ34, but I like as much clean headroom as possible. The SS takes the plate volts up to ~335v (~310v actual after deducting the ~24v on the cathodes).

Geezer

[jakeolly]

hi tubenit
you sent me a link to this recently on music electronics forum (I live in  uk)
I loved the tone of the little wing and you sold me on the extras with reverb etc
I have compared schematic against layout and wondered if you could help clarify a few things:
from point 4 is it D or C as power supply (I think it is c but says Don layout)
B+ --- point A does it have a 220k resistor in paraleel as per schematic or not as per layout
v1 pin 7/2 out - is it 33k resistor or 27k as per schematic
v3 pin2  - is it 56k(layout) or 108k (schematic)resistor?
reverb tube and dwell -- why put it to the right of the preamp - is there any noise issue as I've built a 763 and obviously the reverb goes in after main preamp section- why not there in your version.
I really appreciate your time
Peace
Chris

[tubenit]

I think the link to the soundbits was DaGeezer's version and not mine.  Use his values (with a single 33k input jack) and insert the one tube reverb.  No there is no advantage or disadvantage in having the reverb on the far right on the layout board.  I have done it both ways with success.

Look at the 56T schematic and layout under the SCH file of the HoSo56 thread for a better example of the layout board with reverb.

http://www.el34world.com/Forum/index.php?topic=6176.0

Hope that helps. I can draw another schematic and layout for you but won't have time in the few days to do so.

Remember these SCH files are easily editable into something else. You can use Jschem if you're on a MAC.

With respect, Tubenit

[Geezer]

I'll see if I can help w/ some of the questions:

B+ --- point A does it have a 220k resistor in paraleel as per schematic or not as per layout

That is a "bleeder" resistor, to drain the B+ voltage after shutdown (safety/convenience), not absolutely needed & has nothing to do with "tone" at all.

 

v1 pin 7/2 out - is it 33k resistor or 27k as per schematic

Any close value will work fine......simply helps block out RF signals (radio stations/CB radios & such)

v3 pin2  - is it 56k(layout) or 108k (schematic)resistor?

Simple preference.....I didn't use a resistor at all at that location in any of my builds.

[tubenit]

OK, this incorporates some of Geezer's and my values in the schematic along with reverb. Compare his schematic with mine.  And I changed the layout to have reverb in the middle instead of the input side.  I prefer 2.2k on the pentode screens of the 6BM8.

NOTE that you could also easily build this with a 5879 V1 tube instead of the paralleled 12AX7.

With respect, Tubenit

[jakeolly]

dear tubenit and Geezer
I am really grateful for your time and expertise
I havent quite decided wether to go with reverb or not but I reckon I 've got a better chance of getting it in the living room  if its smaller so maybe without reverb but with an effects loop
If thats the case what dimensions of cabinet do you think is best  for the combo version ?
 also pine sapele or walnut?
I have a lapsteel comission waiting on the bench but I think this ihas to come first (I think I'm addicted)
thanks again guys

 

[tubenit]

You can use a passive effects loop with a Boss digital delay and get a HUGE sound with it.

My cabinet is about the size of a Princeton Reverb or a Deluxe 5E3. And I am using a Ragin Cajun 10" that is quite loud and has reasonable bass to it. I actually tried some 12" speakers with LWR and liked the Ragin Cajun better. I think pine, sapele or walnut would all sound good. I suspect that walnut would be the brightest sounding.

A few yrs ago, I had a cab built out of either 9 or 11 ply plywood that sounded great to me. If I ever tolex an amp again, I'll try to find some more of it.  I thought it was very resonant sounding and pretty light weight. One reason I say that is that I tried the same amp chassis and speaker in two different cabs. (It went to a good home in Virginia to a great guy and player there.)

With respect, Tubenit