Bassman 5b6

[M Fowler]

Well I decided to finish up that PTP Bassman 5b6 tonight and was pleasantly surprized at how quiet this amp is. The lack of knobs is nice change too.

This one is based on Tino Zottola's Book and was a blast to build. Hammond 12x8x2 chassis, bottom plate, and cage. Need to paint the cage a darker gray to match the black chassis. Mounted the plate, cage and rubber feet late tonight and gave it a test drive, I like.

Mark


EDITed Tino's name:

[Structo]

Nice!

How does it sound?

[mcrracer]

Hey Mark, Great looking build, What trannies did you use? I have never noticed this one before. I take it that it has plenty of volume...but how is the TONE? Did you build it from the Fender schematic? I have planned a Bassman build along the lines of the Bluesmaker eventually. Now this one looks cute and simple. Simple is good. I think I will add this one to the list. I already have to live to 100 to build everything on my list!!!

[Structo]

Do you have a scan of the schematic you used?

I was wondering if you made any modern tweaks to the amp like screen resistors and swampers on the output tubes?

Did you follow the tube type from the 5B6?

[M Fowler]

Thanks guys this was a project I have been wanting to do since I bought Tino Zottola books from AES (tubesandmore.com). This is a project in Volume 1 Fender Bassman 5b6 but wired PTP it has 30watts into 4 ohm load.

The preamp tubes are 6SC7 preamp driver, 6SL7 phase splitter, 6L6s and 5U4 rectifier. I used Weber W404248 4000 primary/2,4,8 secondary. 40 watt rating. PT is Weber W022798 120/125v is used the 125v 360-0-360, 6.3ct 6A, 5v 3A.

Nothing fancy for caps as you can see plain old yellow caps and 1w CF xicon resistors. 250R/10w bias resistor. It uses inverse feedback.

I do have the schematic which is the same as the Fender but I used Tino's PTP layouts in his book.

Mark

[txbluesboy]

Nice job. How well does the tone control work? I built an all octal tube amp into an old radio using a Fender 5E3 Deluxe single knob tone control but the tone control really affects the volume. Would this be a good one to try?

[M Fowler]

txbluesboy,

Thanks, the tone control works very well and is actually responsive unlike some I have tried for a passive circuit. Yes this would be a good one to try.

I like the sound of the amp and it does have 30watts using recommended 50w rating OT. Edit: I ended up using 40w OT. I only used my Les Paul for testing but my friend is bringing over his Gretsch guitar for a test run this weekend. He wants me to build him a Gretsch playboy looking amp as I have no intentions of actually using a Gretsch circuit in the amp.

I just wanted to make some simple amps to have fun with before I start on my kids and grand kids small Fender tweed amps for keepsake gifts.

[mcrracer]

Mark, What is the value of the plate resistor on the first tube? Thanks

[M Fowler]

That is 270k with 216v on the plates pin 2 and pin 5 of the 6SC7.

[mcrracer]

Thanks Mark!

[M Fowler]

Your welcome let me know if you need anymore information.

Mark

[M Fowler]

I would love to have a gut shot of the Komet 19 to see what kind of 18watt marshall PTP circuit is being used.

[mcrracer]

I searched on this and could not find any real details. Any one up to educated guesses? 3 way bright switch...possibly the same as in the Express?? And what exactly is the Sat. contriol?? maybe a gain control on the second gain stage? any other guesses?

[M Fowler]

Yeah Zaphoid Phil on 18watt.com figured it was a gain control. In recent post some one had the info but I did not get a response on a PM.

[mcrracer]

The descriptions make it sound like a pretty useful amp but I agree with Phil the 18 watt comes pretty close for my money! If they can get those prices great. I aint mad at 'em!