The Fender Super Bassman 300 thread

[G-Dog]

... ... ... Does adjusting the bias cold or warm really affect the sound? If so please explain the effect on tone.

"Too cold and the amp can be flat and sterile sounding, too hot and it runs out of headroom and distorts sooner than it should."

"Biasing an amp's output tubes “hot” means they will work harder (and potentially burn out sooner) while sounding warmer and softer with an easier onset of distortion."

For more info, just google "tube amp bias".
.

 

[Bassi5t]

"Too cold and the amp can be flat and sterile sounding, too hot and it runs out of headroom and distorts sooner than it should."

"Biasing an amp's output tubes “hot” means they will work harder (and potentially burn out sooner) while sounding warmer and softer with an easier onset of distortion."

For more info, just google "tube amp bias".
.

Yes I’ve read that but I am asking more specifically about the effect on the Super Bassman rather than a general rule.

I play an SVT 3 pro at rehearsals and it has a “tube tribe” knob that adjusts the plate voltage. I like the sound at about 1/4-1/3 up. Wonder if the bias on the SB works the same way.

 

[G-Dog]

... I am asking more specifically about the effect on the Super Bassman rather than a general rule. ... ... ...

Have you read about the Automatic Bias system, starting on page 3 of the Super Bassman manual?
.

 

[Bassi5t]

Have you read about the Automatic Bias system, starting on page 3 of the Super Bassman manual?
.

Yes. Again, just looking for real world/ player’s experience with this feature.

 

[Wasnex]

I’m selling my Mesa Prodigy to get either a 100t or super bassman. I’ve been reading all I can and still have so much to read but have yet to find the answer to a question I have.

Does adjusting the bias cold or warm really affect the sound? If so please explain the effect on tone.

Adjusting the bias can have a small effect on tonal balance and how tight or loose the amp is.

Results can vary by model of amp and brand/model of tubes. YOU DO THIS AT YOUR OWN RISK! In general the hotter you run the tubes the quicker they were and more risk of some sort of failure.

The Prodigy is pretty hard on the tubes, so I would not run them hot.

The 100T and Super Bassman have autobias. You can select from one of 3 levels: Cool, Normal, Warm. See the Owners Manual. Super Bassman_0081440000d.pdf (fmicassets.com)

Some amps have test points and bias controls. In order to experiment you would need to measure the bias current in each tube and then calculate how much dissipation is being used. The general rule is adjusting no hotter than 70% in class AB designs. Some people run a bit hotter (75%). Also factory bias for some amps is significantly lower than 70%. I would not push these more than about 5% over the factory setting without confirming it is safe to do so. AFAIK it's safe to run the tubes colder, but you may not like the sound.

Some amps use bias lights and bias controls. There is a range of adjustment where the green (good) LED is on and red (bad) LED is off. So you can adjust closer to the red threshold for hotter and closer to the green threshold for colder.

 

[Bassi5t]

Adjusting the bias can have a small effect on tonal balance and how tight or loose the amp is.

Results can vary by model of amp and brand/model of tubes. YOU DO THIS AT YOUR OWN RISK! In general the hotter you run the tubes the quicker they were and more risk of some sort of failure.

The Prodigy is pretty hard on the tubes, so I would not run them hot.

The 100T and Super Bassman have autobias. You can select from one of 3 levels: Cool, Normal, Warm. See the Owners Manual. Super Bassman_0081440000d.pdf (fmicassets.com)

Some amps have test points and bias controls. In order to experiment you would need to measure the bias current in each tube and then calculate how much dissipation is being used. The general rule is adjusting no hotter than 70% in class AB designs. Some people run a bit hotter (75%). Also factory bias for some amps is significantly lower than 70%. I would not push these more than about 5% over the factory setting without confirming it is safe to do so. AFAIK it's safe to run the tubes colder, but you may not like the sound.

Some amps use bias lights and bias controls. There is a range of adjustment where the green (good) LED is on and red (bad) LED is off. So you can adjust closer to the red threshold for hotter and closer to the green threshold for colder.

Thank you for the detailed response. Fortunately or unfortunately I’ve already gained that knowledge.

Just looking for REAL WORLD experience on the 100t and different bias setting. They make it adjustable for a reason. I’m not interested in generalizations or how it works/sounds in other amps. Those that have messed with the adjustment on the 100t, what was your experience and where do you usually have it set?

 

[flatwound62p]

Never bothered with cold bias but tried running on the hotter settings on my Super Bassman a couple of years ago. Honestly couldn't hear any difference so I put it on Normal bias and left it.

 

[rodl2005]

Thank you for the detailed response. Fortunately or unfortunately I’ve already gained that knowledge.

Just looking for REAL WORLD experience on the 100t and different bias setting. They make it adjustable for a reason. I’m not interested in generalizations or how it works/sounds in other amps. Those that have messed with the adjustment on the 100t, what was your experience and where do you usually have it set?

I've got a Super Bassman and altho I've meaned to try hotter or colder on mine, Ive never done it.
Honestly, it sounds so good as it is, in normal setting, I probably won't. Never say never tho.
If I do, I'll be sure to post here

I've tried the 100T only instore, and it did sound sweet.
Real happy with the Super Bassman tho

Just seems to nail it using any bass

 

[Bassi5t]

I've got a Super Bassman and altho I've meaned to try hotter or colder on mine, Ive never done it.
Honestly, it sounds so good as it is, in normal setting, I probably won't. Never say never tho.
If I do, I'll be sure to post here

I've tried the 100T only instore, and it did sound sweet.
Real happy with the Super Bassman tho

View attachment 5203475
Just seems to nail it using any bass

There is a 100t and super bassman locally that I am trying to decide between. On a $250 difference. I’m really interested in the 100t because of the weight, less money when I need to re-tube and ability to do 25 watts. I have a bassman 410 to go along with it and figure if 100watts is. It enough I can just add another cab. I’m really interested in the power tube breakup and just think I’ll never get to that point with a super bassman.

 

[Meghans Dad]

I have a Super Bassman and the difference is negligible, especially at lower and mid levels. It might be my imagination, but I think I get just high touch of distortion on Warm when I go over 6 or 7, then get told to turn down. I also keep mine at set normal because I want the tubes to last...damn, those big things are expensive and hard to find. Think twice about the SB because it is a heavy bastard. Make sure you have a dolly and a good friend with you.

 

[rodl2005]

There is a 100t and super bassman locally that I am trying to decide between. On a $250 difference. I’m really interested in the 100t because of the weight, less money when I need to re-tube and ability to do 25 watts. I have a bassman 410 to go along with it and figure if 100watts is. It enough I can just add another cab. I’m really interested in the power tube breakup and just think I’ll never get to that point with a super bassman.

They're good reasons to go with the 100T, I use a V4B reissue for the same.
That said, the SB300 can get dirty quickly thru the vintage channel into a Bassman 115. But, 100w is pretty sweet for that particular spot, and the 25w setting would be great too

 

[oldskoolskatedad]

Thank you for the detailed response. Fortunately or unfortunately I’ve already gained that knowledge.

Just looking for REAL WORLD experience on the 100t and different bias setting. They make it adjustable for a reason. I’m not interested in generalizations or how it works/sounds in other amps. Those that have messed with the adjustment on the 100t, what was your experience and where do you usually have it set?

I have both the 100T & SB300. To me, I don't find any noticeable affect of the bias settings on either. When I got the 100T I would have my wife change the setting and try to guess which was selected and was wrong as often as right. I leave them both at Normal.

 

[oldskoolskatedad]

There is a 100t and super bassman locally that I am trying to decide between. On a $250 difference. I’m really interested in the 100t because of the weight, less money when I need to re-tube and ability to do 25 watts. I have a bassman 410 to go along with it and figure if 100watts is. It enough I can just add another cab. I’m really interested in the power tube breakup and just think I’ll never get to that point with a super bassman.

I'm fortunate enough to have a 100T and a pair of Bassman 410neo cabs. You are quite correct that if you are mainly interested power tube breakup, which I initially was, then the 100T and a 410 is perfect. If you decide you would like more clean headroom a second 410 will get you there. I also have a Super Bassman and it provides a certain "heft" to the notes that is hard to put into words that the 100T doesn't quite have. I would highly recommend trying them both if possible, you may be surprised which you enjoy more. To me the coolest feature of the 100T is the internal power soak that allows the "post" XLR signal to be taken directly from the power amp output in Silent Record mode. It may not matter to you but the 100T at 25 watts is an amazing guitar amp as well.

 

[rodl2005]

I have both the 100T & SB300. To me, I don't find any noticeable affect of the bias settings on either. When I got the 100T I would have my wife change the setting and try to guess which was selected and was wrong as often as right. I leave them both at Normal.

Now you've got me thinking to try the hotter/colder thing with my Super Bassman.
I need to do this at a gig, or at a gig level rehearsal perhaps (tbh, a gig is more likely ), and I've a couple of gigs midway thru Oct. That should be suitable.

A part of me thinks.... . 'I've had my Super Bassman since 2012 or something, and it's still on its original power tubes. Using the HOTTER setting uses more power tube life, sorta.... Let's not feck with it' And with the current situation with 6550 tubes......'

I reckon I'll give it a try at one of these gigs.

Will report back

 

[Rodrigues]

Hello,
I need help!

my super bassman 300 showed bad tubes (all led were flashing).
So I bought new tubes. Now the amp is able to bias the tubes.
But I get no sound out of the amp.
There is a hum but no bass signal.
Changed other tubes as well - no joy.
When I plug into the Poweramp directly there is also no sound.
Has anyone faced the same issue?

 

[Wasnex]

Hello,
I need help!

my super bassman 300 showed bad tubes (all led were flashing).
So I bought new tubes. Now the amp is able to bias the tubes.
But I get no sound out of the amp.
There is a hum but no bass signal.
Changed other tubes as well - no joy.
When I plug into the Poweramp directly there is also no sound.
Has anyone faced the same issue?

Since the output tubes are biasing and producing a hum, it seems the amp is transitioning from standby to operate.

Things you can try.

Check Speaker Output switch on the back of the amp. Toggle it on and amp a few times. Pull the Master in and out a couple of times. Both of these control mute switches.

Run a jumper from the preamp out to the power amp in. One of the jacks probably has a switching contact. The jumper is intended to bypass the switch, which may be dirty or damaged.

You could also try patching the preamp out into the effects return of a another amp or a recording interface. The idea is to see if the signal is getting to the preamp out.

The only other thing I can think of is make sure all of the small signal tubes are properly seated, and make sure you did not accidentally unplug and connectors. If you have spares, you can try replacing the existing small signal tubes one at a time.

If the problem remains, take the amp to a good repair shop.

 

[Rodrigues]

Since the output tubes are biasing and producing a hum, it seems the amp is transitioning from standby to operate.

Things you can try.

Check Speaker Output switch on the back of the amp. Toggle it on and amp a few times. Pull the Master in and out a couple of times. Both of these control mute switches.

Run a jumper from the preamp out to the power amp in. One of the jacks probably has a switching contact. The jumper is intended to bypass the switch, which may be dirty or damaged.

You could also try patching the preamp out into the effects return of a another amp or a recording interface. The idea is to see if the signal is getting to the preamp out.

The only other thing I can think of is make sure all of the small signal tubes are properly seated, and make sure you did not accidentally unplug and connectors. If you have spares, you can try replacing the existing small signal tubes one at a time.

If the problem remains, take the amp to a good repair shop.

Thank you.

I bridged preamp out with poweramp in. No success.
I got a good signal from di out.
Hum is steady loud but when I turn up the master it doesn’t affect the loudness of the noise.
4 cables in the back (connectors) are tight.

 

[Rodrigues]

One strange thing.
When I reset the bias (hold up and down together for 2 sec) the ham is low.
When the biasing is finished the noise gets louder.

 

[agedhorse]

One strange thing.
When I reset the bias (hold up and down together for 2 sec) the ham is low.
When the biasing is finished the noise gets louder.

This is normal.

You have another significant problem. You should use a Fender authorized service center that’s experienced with this amp. The last thing you want is the amp returned with new and potentially worse issues.

 

[pre-cbs]

just saw this in the manual ...

1. Replace all the necessary fuses. NOTE: The type of fuses used for the tubes can be blown without showing any visible signs of failure. If Fender Automatic Bias indicated that one or more tubes have failed, you should replace the fuse for the corresponding pair(s) of tubes, even if it looks okay.
   

... might be worth a look.

One strange thing.
When I reset the bias (hold up and down together for 2 sec) the ham is low.
When the biasing is finished the noise gets louder.