4x6BM8/ECL82 Little Wing Amp

[foghornleghorn]

This one took longer than I thought it would and was more complex to build than I anticipated. Attached is the schematic, pasted up from the original 2x6BM8 of Geezer's, plus an as built gutshot and upper chassis/tube count pic.
Cannot figure out why the schematic doesn't display automatically. I'm hopeless at this stuff, have no clue.
Iron is Edcor from RJ Guitars, as noted on the schem. Chassis was a blank aluminum 14.5" combo from RJ. 3/32" thick. Plenty stiff.
Tube count is a used '58 Mullard EZ81 (6CA4) rectifier, four NOS Mullard ECL82s in two pairs, one from '66, the other from '69, a '60s GE 5 Star 6072 (12AY7) and an early '60s triple mica RCA 5879 pentode. I put a pair of 100 ohm 5W in between the PT secondaries and the EZ81 plates. These old Mullards ain't cheap and while I know they are tough and you lose about 10VAC putting them in, but now it has the datasheet plate resistance.
I used one pair of 6BM8 triodes for the PI, same as Geezer's original, but then I used the second pair as the V2 gain/CF stages. At $50 a pair for these tubes I wasn't about to waste anything! This complicated the wiring some, particularly as I used a separate cathode resistor/bypass cap for each 6BM8 pair. So if you pull the center pair of 6BM8s or the outer pair, you have 7W but with output impedance issues.
The 6072 and 5879 are alternate first stages switched on the back panel, no room left on the front. Switching idea courtesy of tubenit, a very creative guy.
Big difference in these two first stages, 6072 is clean & Fendery, 5879 is tonally quite different, more in your face with higher gain. Each stage has its own gain pot so you can set up the 6072 for rhythm and the 5879 for lead, just flip the switch.. Very slight click only when you do this as it just switches signal to ground.
I tried it thru a Tone Tubby Alnico 12" but it sounds better thru a Celestion Blue 12". A Pretty Dolly analog style delay pedal gives a really big sound.


I would have thought someone would have done a doubled up version of the Little Wing amp by now, it's been 10 years since Geezer came up with the original, but I haven't run across one and I've looked.


Still need to play with it a bit, haven't tried my 335 yet, just my Tele, so I may need to tone down that 5879 gain a tad for the HBs. But it sounds great, and considering the close wiring it's much quieter than I had any right to expect!


I'm thinking about doing a 4x6BM8 Liverpool....aaagh! stop me before I build again!!

[foghornleghorn]

Here's the upper chassis pic as It would not fit the 2MB limit per post.

[tubenit]

What a beautiful job you have done with this build!  Bravo!  Very impressive.

Thanks for sharing your hard work.  IF you get sound clips at some point, we'd love to hear them.

With respect, Tubenit

[drew]

Wow, that looks great. 

Has it got enough beans to use in a band setting, or is it more of a bedroom/recording type of thing?

[sluckey]

That does look very nice. Good layout.

[tubenit]

A Pretty Dolly analog style delay pedal gives a really big sound

As a side note,  I've owned a Boss Digital delay,  Wampler Faux Echo, and have a Carbon Copy delay.   However, my favorite delay is the Pretty
Dolly.  It's sounds the warmest of all of them and is the cheapest too.

Tubenit

[foghornleghorn]

Drew, 15W is NOT a bedroom amp! If your drummer is channeling Keith Moon it's probably not big enough live, but you can always mic it into the PA. Remember 45 years ago Eric Clapton and Duane Allman both played thru Champs on the classic Layla - Derek & the Dominos album. Check out Key to the Highway on it. Like the lady said, it ain't how big it is, it's what you do with it that counts.

tubenit, thanx for your kind words. I currently have no capability to do soundclips, I would have to get one of my musical pals to do it. I'll work on it, this is a great sounding amp.
I bought the Pretty Dolly based on your recommendation a while back. I've no experience with other delay pedals but it does sound good.
Do you know if anyone has done a doubled up Little Wing like this before? Just curious-based on the effort that goes into one, maybe not.


Steve, thanx too. I did the basics of separating signal from rail, AC or DC, used coax where it looked advisable and tried to cross wires at right angles where I could. The board layout is Geezer's with the 5879 added at one end and the additional cathode resistor/bypass cap at the other, and put the plate and screen filter caps on a separate board. There is a fair amount of Dumble methodology in my layout I guess, too, including the grounding points location scheme.

[Willabe]

Looks great!!!!! 

What brand e-caps are the 33uF/450v on the far left?

Eric Clapton and Duane Allman both played thru Champs on the classic Layla - Derek & the Dominos album.

The song Layla itself was probable an old tweed Champ EC had for years that Delaney Bramlet gave him that had a 10" Altec speaker and probably ran a 6L6.

But, there's a number of interviews with the session engineer, the producer and with band members that say EC also used a BF Princeton Reverb and that Duane used a brown 2 tone Gibson 2x6V6's (Butch Trucks also said this), which 1 is anybody's guess as Gibson had several of those amps with different tube line ups for the preamp.   

[foghornleghorn]

Interesting detail! I stand corrected. However, none of those amps are more than 15W so I think the lady is still correct!

Those 33uF filter caps are the reservoir filter for the rectifier, and feed the 6BM8 plates. Manufacturer is B.M.I., Barker Microfarads Inc., of Virginia. I got them a couple of years ago from Steve at Apex Jr., the excellent surplus dealer in Southern Calif., Burbank I think. They were made in 2013 and were so cheap I bought 15 of them! $1.50 each, he's still listing them, I just checked.

[kagliostro]

Very Nice Job !!


 


Franco