Bassman 5b6

[M Fowler]

RP

Originally I built the 5b6 with no 68k grid stoppers and used 2m2 grid leak for each input.

Recently I added 68k grid stoppers and one input has 1m grid leak to use for regular guitar and pedal guitars with 4k pups. The second input has 10m grid leak.

[rp]

Don't you need a cap to make the grid leak work?

[JazzGuitarGimp]

Thanks guys.


Would one of you be willing to spend a minute and describe the sound of the bias-vary term in the 5B6 vs. say, a blackface reverb amp? I am not sure I've ever heard the bias-vary varietal.

Many thanks,
Lou

Lou, the 5B6 does not have a trem circuit. You might want to start another thread about the brown verses black term circuits though.

TM

Thanks Tone, I've been looking at so many schematics lately that they're all starting to blur!

[M Fowler]

Don't you need a cap to make the grid leak work?

RP

I used a different schematic which has been posted many times. https://tubeamparchive.com/download/file.php?id=25858

[rp]

So you did do it grid leak, no wonder you like so much. I'm surprised it's ok with pedals - even boost pedals. IME hit it with too much signal and it'll make wounded animal sounds (but excellent ones if you're in the mood). Interesting that it handles the signal from a pedal steel, though actually I've no idea if they are any hotter than guitars.

[M Fowler]

The old steel testing with had 4k pups. The other pedal steel not sure of but was different wind. We used 1m and 10m input for testing.

We tried a TC Furlong Split 400W Class D amp with Black Widow 15" speaker too. I didn't have the line out jack installed at that time for complete testing yesterday.

Single coil can run from 14k to 20k and humbuckers are even higher 22k.

But from what I have been reading the guys are using specially made tube buffer boxes between guitar and input and they also have rack mount tube preamps along with high powered SS amp/speaker cabs. I think a Dumblelator might work.

Mark

[M Fowler]

So you did do it grid leak, no wonder you like so much. I'm surprised it's ok with pedals - even boost pedals. IME hit it with too much signal and it'll make wounded animal sounds (but excellent ones if you're in the mood). Interesting that it handles the signal from a pedal steel, though actually I've no idea if they are any hotter than guitars.

Just the opposite really this amp takes pedals so well you'll be surprised and the compression is so sweet. Dark mellow tones with a level tone pallet (treble, mids, lows) that stays consistent. With regular guitar especially LP type or humbucker pups the breakup is gentle not gritty, damn hard to explain must be heard.

A lot of the old amps sound like this to me. Might try build a Standel 25L15 since it uses Trainwreck Express iron 300-0-300 PT and 6k6 OT.

[rp]

I posted before you put up the schematic. Isn't V1 in that diagram cathode biased? With grid-leak the large value resistor is from grid to ground and cathode straight to ground with a cap from the input to the grid. Do I have it wrong are there other types? I pulled this off the web:

http://www.groupdiy.com/index.php?topic=7623.0

[M Fowler]

This preamp is cathode bias both halves are tied together to the 250uf cap/2k7 resistor. Not grid leak bias.

[rp]

Try the grid leak set up from the 5C8. It'll take you 20 min to swap. Trust me it's way cool. Not the best if you overload it but straight in with a tele or strat it has a sensitivity and immediacy that'll amaze you if you never tried it.

I gotta turn on the heat or go to bed, buona notte.

[M Fowler]

https://tubeamparchive.com/download/file.php?id=19503

Found your old post.

That circuit is probably even better for guitar it has the coupling caps .05 right where they should be for good tone. Rather then the .1 coupling caps in 5b6.

Ha another amp I have to build just freaking great

[Matt D]

I just noticed no screen grid resistors on the power tubes.

[M Fowler]

Yeah this is old school but you may choose to spice your amp up a little with some modern touches like screen resistors.

[M Fowler]

Had a good week but I'm still a little bummed I was suppose to be in Nashville today to meet up with Troy Jennings (nephew of Waylon Jennings) and Tony King (Brooks & Dunn Band) to toss down a few beers and I don't even drink anymore. Both are great guys. I couldn't make the trip and that pisses me off!

But I did get more amp parts in today and my amp book.

Told my lovely wife we are getting small Class A land yacht and going motoring

[rp]

Ha another amp I have to build just freaking great

At least you sell them! I just pile them up in a tiny apt. Everyone I know is happy with just one amp. Like I said, 12 step program.