Bassman 5b6

[Milkmansound]

yeah, he makes an "80W" version now

all he had to do was switch over to grid bias and the headroom would follow but I am not sure if he understands these things

the hoopla about those amps has quieted down to a faint whisper over on the steel forum. I have seen them sell for as low as $1200 including shipping.

but anyway -

The 5B6 that I was a spiritual adviser on (hands off - just advice and helped bring it up for the first time) was perfect from the get go. Was point to point wired into an old Bell and Howell amp chassis. No special attention was paid to grounding, routing or even values for that matter. We subbed in a 6SL7 in the preamp and changed the input jacks to a later period Fender style. Also added stoppers and screen resistors to the output tube sockets. The amp is very toneful even with the inexpensive Sovtek tubes and EH power tubes.

I think this amp works well when built PTP but long leads may be the death of it - which is strange because the original Fender version had very long leads to the controls. The Bell and Howell chassis was a real squeeze but I think that is a good thing!

Really a great sounding amp - however the octal tube thing is a real monkey wrench in the reliability factor. Its hard enough as it is making a reliable tube amp with noval tubes making octal amps is not going to be in my wheelhouse

[rp]

I read that Little Walter now is running two amps each with pair of KT120 tubes to get some clean headroom.

I'm thinking if you want more headroom from a 5B6 do what Leo did - Build a Blackface Bassman, if still not enough make it a Showman

Still, I don't want to poop on LW's parade, it's fun to mess around with old circuits in new ways.

[M Fowler]

I'm not sure that Phil knows what he is doing either, but he has a fan base

I need to build two more and then that's it for the 5b6 saga. Tim glad your kicking ass on those nice Milkman amps, sell a bunch.

Mark

[renshen1957]

RP, can you clarify what you mean? Which grid leak set-up?

I'm curious why the 1952 Bassman got cathode bias while its brethren got grid-leak,

Thanks! Yes, those old octal amps sound fantastic.

Hi,

The Bassman had a history of being the test bed amp for new circuit designs.

Best regards,

Steve

[telentubes]

I'm going to have to rebuild mine, point to point, as it's not really up to snuff. I can't seem to give up on it as it has some really nice full rich tones, but along with that comes a bunch of ghost notes and faint fizzy distortion. Not really acceptable.

[renshen1957]

RP, I'm using Haltron 6SC7GT

I was going to post and ask about those. There are several web sellers with stocks. Does yours state a country of origin? The only old USA GTs I've seen have been smoked glass and Raytheon and Tungsol brands, the Raytheon probably a Tungsol too. I'm thinking those Haltrons are a 60-80s Euro/East Euro make? Any clue?

Hi,

Eastern European, most likely.

New Sensor sells 6N10S (or 6H10C depending on the alphabet), as Sovtek 6SC7 for only $30.88 each. Somebody in the Hi Fi crowd discovered the 6SC7 as a sub in valve one in a phono preamp stage).

http://vinylsavor.blogspot.com/2011/06/ ... -6sc7.html

Best regards,

Steve.

[M Fowler]

I'm going to have to rebuild mine, point to point, as it's not really up to snuff. I can't seem to give up on it as it has some really nice full rich tones, but along with that comes a bunch of ghost notes and faint fizzy distortion. Not really acceptable.

If you do go PTP follow Tino's layout in his book otherwise leaving the tubes all in a row on back of chassis defeats having nice short PTP wire/component runs. Leave room between the power tube sockets to put in some KT120's you'll like them. Right now I have 6550's in one amp.

Mark

[M Fowler]

A steel player near me has a LW 50w head and the Hammond OT was wired incorrectly per him and his tech. They rewired the OT and presto it sounded great. They are running KT120's in that LW amp right now.

But the 85w Milkman kicks ass over the LW 50w.

Mark

[Phil_S]

Holy cow, $30!!!!!!!!!!! For a Sovtek???????
At that price, it is worth rolling the dice at a place like this http://www.fourwater.com/xradio/xradio-xr3.htm#6SC7 where you can get used test as nearly or better than new real Tung Sol glass tubes for $15 and metal ones for half that, and there is probably nothing wrong with the metal ones at the bottom of the list for $3 and $4. While you are at it, have some fun and buy a few pounds of octal (10¢ per pound) or noval/7-pin ($1 per pound) bargain bin tubes:
http://www.fourwater.com/bargain/junque/tmini1.htm
http://www.fourwater.com/bargain/junque/octpound.htm
Admittedly, this place is like a carnival. You really should figure the games are rigged in favor of the house, but it looks like too much fun to pass it by. Maybe you'll get the ball in the bucket and win the teddy bear!

[M Fowler]

Phil good place to shop, I'll give them a try. Thanks.

[rp]

Holy cow, $30!!!!!!!!!!! For a Sovtek???????

I agree completely, might as well try ebay too, I've had good luck both NOS and ANOS. As octals tend to be microphonic I don't hold that against the seller.

So on those 5B6s running KT120s did the power tube voltages get cranked up or the same with just a tube swap? What is the power tube plate voltage on the stock Tino 5B6, ~400V? I would try upping the voltage to 475V or even a bit more and just using good 6L6GCs to try and keep more of the original Fender flavor. Pretty sure you'll loose some sweetness, however.

I have a pair of 807s I'd like to use in a 5B6 one day, more for aesthetics than for any sound quest. If anyone wants to try that and report back...

[M Fowler]

390vdc on plates, Tino spec's 700vct PT and 4k primary OT 50w rating.

No changes made to stock amp running KT120's on two different amps one LW and other 5b6 cage amp.

My other experimental 5b6 is so changed it is more like a Ampeg B15n circuit using 6SL7 and 6550 power tubes.

[Phil_S]

Phil good place to shop, I'll give them a try. Thanks.

Just don't get too excited about the bargain boxes. Here's my report from a while ago: https://tubeamparchive.com/viewtopic.php?t=19987
Short report, the $0.20 spent for octals was good, the $1 for the 7/9 pin tubes was wasted, except maybe for the fun factor.

[Blackburn]

390vdc on plates, Tino spec's 700vct PT and 4k primary OT 50w rating.

I know that Tino calls for a 350-0-350 PT, but is this the same as Fender's specs on this amp back then? I may have Heyboer do one for me and if the original specs were lower, that's what I'll have them do.

[M Fowler]

I don't know what original Fender Bassman 5b6 voltages were not shown on schematic.

Mark