Fender Bassman 100T Chapter 3

[GG7]

Well, that's odd. Not really practical for live, but if you're happy with how it sounds good in the practice room then cool.

I just have the reverb pedal box upstream of the input to the amp. Guitar goes into the verb and the verb plugs into the input of the 100T.

Its not really that odd. Lots of players run some reverb out of their rig and send that to the FOH as part of their overall tone. As I mentioned, Chris Squire of YES runs his stage reverb the same way, although he uses a more expensive version of what I have from T.C. Electronics.

EDIT: Saw your second post just now further down...

Yeah...I just put it before the amp and let the verb get processed by the amp's tone controls and stuff just like the bass tone itself. Works great for me. Wouldn't always use it when recording, but there are some things I am working on right now that I plan to run the verb in the signal onto the recorder because in my mind it is part of the sound of the bass and works with the song better than adding it later in the mix.

 

[tombowlus]

What really disappoints me is that Fender has a great product here, this is now one of the longer running threads and must have had some influence on promoting it, yet no-one from Fender will officially talk to us or support us on this forum. Some other companies input when necessary to support or reassure their clients, I just wish Fender would do the same. It must be a conscious decision on their part for whatever reason, I suppose.

Yup, you guessed it. Fender's corporate policy prevents their employees from posing on online forums. But, we worked closely with the tech-heads at Fender on the SB300 review, so I ran some of these issues by them.

That notwithstanding both new Fender tube amps remain superb examples of a mix of new and old technology and the sooner this bias issue is finally put to rest the better it will be for them and their loyal users.

Here's what they had to say about the bias issue:

1. First off, the ‘bias chip’ replacement has nothing to do with any hardware issue, but was an update to correct a software bug relating to memory storage (every so often the system stores the current bias setting in memory) that we found after the first implementation of Autobias in the Super Sonic 100 guitar amplifier. The 4x6L6 output section of the SS100 is similar in the 100T. It was statistically 100% likely that the ‘out of memory’ issue would at some unknown point in time cause the system to crash with no way to recover (not even power cycle). Several SS100 amps failed in this manner in the field which altered us to the issue and we were able to update the software just before the Super Bassman and 100T shipped out to dealers/customers. I’ve not heard of any SB or 100T amps having this freeze problem. In the frozen state, the tube bias voltage was pulled to the most negative DC voltage, so there was no harm to the amp but it sounded bad.
2. A few other ‘bias chip’ issues were related to intermittent connection of the ribbon cable from the main amp PCB to the AB PCA. This has been addressed at the factory and authorized Fender service centers have been notified of the appropriate action to take to rectify the issue.
3. There are UI improvements found in the next gen AB code (found in 6-tube Super Bassman) that were not able to be implemented into the original 4-tube version. As a result there is more intelligence in the Output Tube Status LED display on Super Bassman than on 100T (or SS100).
a. The 6-tube Super Bassman code incorporates the slow blink rate when the amp is in STANDBY (or PWR AMP MUTE) to acknowledge the state change. When the tube HV is off the tubes are not ‘on’ (however when the PWR switch is in ON the tubes still have heater voltage applied and will still glow) and the tube status at that point is truly unknown. The last known tube status is maintained, meaning if a tube was good (Green) before it will blink Green slowly during ‘standby’ mode.
b. The 4-tube version does not have direct knowledge of the Power or Standby switch, which the 6-tube version does. Instead that logic line is dedicated to the Output power switch (100W/25W) on the 4-tube models. The consequence of that is that the 4-tube version does not instantly know when the switch has toggled (see above) and has to wait until the current in the output tubes falls as the HV tube supply voltage bleeds off. Only when all tubes have fallen below the ‘off’ threshold does the AB system enter into ‘Standby’ mode and not attempt to make any adjustments to the bias (or update the display). This can take several seconds to happen and during that time it is possible for AB to falsely think that a tube has failed and update the status LED from Green to Orange for the pair. I think TB’ers with 100T amps may be reporting this as a bias issue (but the amp still works correctly) when the amp is in STANDBY.

Presuming it's not a violation of any TB posting rules, I might be able to get them to give me feedback to share regarding other questions, so feel free (I think) to hit me up if you want me to run more questions past them.

Later, Tom.

 

[GG7]

Been messing around with really pushing the overdrive on the active channel today and wrote a new riff/tune based on that tone.

Details of the settings and the tubes used are listed on the YOUTUBE page for this video.

For those who may not own a 100T and are curious about what you can do with the active channel beyond traditional bass guitar tones, this is a good example of what you can do by pushing the V2 preamp tube hard. This is where high quality vintage preamp tubes really shine.

Running a 1961 vintage Amperex Bugle Boy 12AX7 in V2 for this demo.

http://youtu.be/jfOwU69D_7Y

 

[GG7]

b. The 4-tube version does not have direct knowledge of the Power or Standby switch, which the 6-tube version does. Instead that logic line is dedicated to the Output power switch (100W/25W) on the 4-tube models. The consequence of that is that the 4-tube version does not instantly know when the switch has toggled (see above) and has to wait until the current in the output tubes falls as the HV tube supply voltage bleeds off. Only when all tubes have fallen below the ‘off’ threshold does the AB system enter into ‘Standby’ mode and not attempt to make any adjustments to the bias (or update the display). This can take several seconds to happen and during that time it is possible for AB to falsely think that a tube has failed and update the status LED from Green to Orange for the pair. I think TB’ers with 100T amps may be reporting this as a bias issue (but the amp still works correctly) when the amp is in STANDBY.

My amp did this the other day. Two of my GE 6L6 GCs came out of standby as ORANGE, but I knew that there was nothing wrong with them, so I shut the amp off, waited a couple of minutes and powered it back on, and they were back to green.

This detail you quoted above is very likely responsible for much of the reports of a defective bias circuit. If I didn't know my power tubes so well with my own high end tube tester etc. I would be confused by this behavior, although this was the first time I have ever seen this on my amp, and I have hundreds of hours on mine now.

All my power tube tests using known borderline tubes and even one with a known gas/leakage problem were correctly flagged by the 100T bias circuit and went either orange or red depending on the known condition of the tube prior to installing these "bad" tubes in the amp to see how good this circuit was. Personally I am VERY IMPRESSED by how savvy this little circuit is, although I wish there was a way to retrofit the more advanced SB version into our 100Ts. That improved version sounds even better!

regarding the guy with the bias issues again after being serviced...

If this amp in question is still having bias circuit issues after everything that has already been done, I would push Fender for a replacement at this point. Better to just replace the entire amp than continuing to encounter problems like this.

 

[joemer]

Yup, you guessed it. Fender's corporate policy prevents their employees from posing on online forums. But, we worked closely with the tech-heads at Fender on the SB300 review, so I ran some of these issues by them.

Here's what they had to say about the bias issue:

Presuming it's not a violation of any TB posting rules, I might be able to get them to give me feedback to share regarding other questions, so feel free (I think) to hit me up if you want me to run more questions past them.

Later, Tom.

Hi Tom,
I posted a few days ago with the issue mentioned in item B. I am showing 2A and 2B as orange yet the amp seems to be working normally. This explanation seems to suggest that this will only show up when the amp is in standby mode( unless i am misunderstanding this) yet in my case it is displayed with the amp fully powered up. I brought my amp into the authorized servicer in my town and am waiting to hear back. Do you know if the have a fix for the issue in item B? I have the 100T.

 

[GG7]

Hi Tom,
I posted a few days ago with the issue mentioned in item B. I am showing 2A and 2B as orange yet the amp seems to be working normally. This explanation seems to suggest that this will only show up when the amp is in standby mode( unless i am misunderstanding this) yet in my case it is displayed with the amp fully powered up. I brought my amp into the authorized servicer in my town and am waiting to hear back. Do you know if the have a fix for the issue in item B? I have the 100T.

What item B is basically saying is that the AB is being fooled by the voltage of the power tubes as they are coming back up to full power out of stand by mode. As if it is trying to check them too soon, before they are back up to operating voltage. If you time it just right when coming out of standby on initial cold power up, it appears that you can fool the AB into thinking it has identified bad tubes when in reality, it tried to check them while the power tube voltages were still rising out of standby. This is what happened to me the other morning. This would only occurr when coming out of a cold power up for the first time. Once the amp is up and the tubes are all green, going into stand by and back to FULL ON again would not likely cause this problem. Provided I am reading Fender's explanation correctly.

A full shut down followed by a 2-3 minute wait before powerup again should resolve this particular problem. Provided that the power tubes are indeed good and not actually having a real problem that would mkae them go orange. If this doesn't fix the problem you could try reseating the tubes, and/or just rearranging them from their original order.

I wouldn't go as far as to say that this is a defect, but more of a slight design flaw in how the AB works. It seemed realatively easy to correct by just powering down the amp for a few minutes and restarting it, taking care to give the amp at least 2-3 minutes in standby mode before turing it to full ON.

 

[joemer]

Try reseating the tubes, or just rearranging them from their original order.

What item B is basically saying is that the AB is being fooled by the voltage drop in standby mode. If you time it just right when coming out of standby on initial cold power up, it appears that you can fool the AB into thinking it has identified bad tubes when in reality, it tried to check them while the power tube voltages were still rising out of standby. This is what happened to me the other morning. This would only occurr when coming out of a cold power up for the first time. Once the amp is up and the tubes are all green, going into stand by and back to FULL ON again would not likely cause this problem. Provided I am reading Fender's explanation correctly.

A full shut down followed by a 2-3 minute wait before powerup again should resolve this particular problem. Provided that the power tubes are indeed good and not actually having a real problem that would mkae them go orange.

Thanks. My amp is in the shop now but I will share this with the tech.

 

[Tim1]

Tom, thanks very much for such a valuable and informative post. You are a real asset to the forum. It is a relief to have it confirmed that Fender is acknowledging and addressing tnese issues, as indeed I was sure they would be. It seems tbat the majority of us, having experienced no issues, can expect a long and healthy life from our amps (rather than go on a gig wondering if it is going to strike). The issue with the ribbon cable was reported on in one of the original posts and successfully fixed. One would hope that it is now only the occasional "lemon" that slips through and Fender or their agent is replacing these. It is also a relief to hear that the bias chip issue should only apply to the guitar amps and no Bassmans have gone out with the old faulty chip.
Fender have a great product here, with proper dealer support it could become the stuff of legends.

 

[PhatRon]

I find myself quite often looking at the back of the amp for any of these issues. so far thumbs up every time. I really feel for those of you having issues. Hope that you all get some resolve with your efforts.

 

[Tim1]

I have refused to obsess, and simply do not look at the back of the amp any more than I would with any other amp. Naturally, if my ears told me something was wrong it would be my first act.

 

[GG7]

Pretty sure if you give the amp ample time to warm up in stand by before engaging the amp, this particular problem will probably never present itself.

When it happened to me the other day, I was in a hurry to get the amp up, and I didn't leave it stand by as long as I usually do.

 

[rodl2005]

Yep I do the same. Treat my Super bassman like all other tube amps I've ever had.
I do check the rear sometimes but only once per gig abouts

 

[tombowlus]

Thanks. My amp is in the shop now but I will share this with the tech.

FWIW, Fender did say that it's easier to swap out the AB PCA than to reprogram it "in circuit" (though that is possible).

 

[Moosehead1966]

Here's a pic of my new 100T atop the Hydrive 410. Sounds rich and 'tubey'. Any advice on the mid settings for the overdrive channel?

Thanks, Marc

p.s. sorry for the 'side view' pic. Just click on it. Should go straight...

 

[Freight Train]

View attachment 368499

Here's a pic of my new 100T atop the Hydrive 410. Sounds rich and 'tubey'. Any advice on the mid settings for the overdrive channel?

Thanks, Marc

p.s. sorry for the 'side view' pic. Just click on it. Should go straight...

First, the wall mount is unique, but I'd put it on the floor for a more solid base and bass.
All seriousness aside, there's no real way to answer, it depends on your taste, the music you're playing, and the sound of the cab. With the Bassman 410 Neo cab, tweeter level around 11:00, I don't use much eq at all. On the overdrive channel I usually peak the mid eq around 6.5 to 7 centered at what I'd guess is around 2k - 2.5k or so. I don't know the number on the frequency knob, I do it by ear. Just enough to make it a little more aggressive in the upper mids, so the channel has a more distinct bite to it compared to the vintage channel even when not using overdrive. I'll usually use this for my roundwound bass and the vintage channel for the flatwound. But that's me. Other guys may crank the chili out of it, plus use an eq pedal. Depends on what you want and what you're hearing.

 

[MrCool84]

View attachment 368499

Here's a pic of my new 100T atop the Hydrive 410. Sounds rich and 'tubey'. Any advice on the mid settings for the overdrive channel?

Thanks, Marc

p.s. sorry for the 'side view' pic. Just click on it. Should go straight...

100t fits perfect!!! Stoked for u! Well back to work in jacksonville fl for two more weeks luckily I have my Hartke a70 down there so I can thump some but geez do I miss hammering my 100t 610 neo!! Nothin like it!

 

[Freight Train]

I just have the reverb pedal box upstream of the input to the amp. Guitar goes into the verb and the verb plugs into the input of the 100T.

Its not really that odd. Lots of players run some reverb out of their rig and send that to the FOH as part of their overall tone. As I mentioned, Chris Squire of YES runs his stage reverb the same way, although he uses a more expensive version of what I have from T.C. Electronics.

EDIT: Saw your second post just now further down...

Yeah...I just put it before the amp and let the verb get processed by the amp's tone controls and stuff just like the bass tone itself. Works great for me. Wouldn't always use it when recording, but there are some things I am working on right now that I plan to run the verb in the signal onto the recorder because in my mind it is part of the sound of the bass and works with the song better than adding it later in the mix.

There's a major difference. This is way off topic, but others here may be interested in this regarding the use of fx. In recording, the 'normal' way to use reverb on bass would be to add the reverb during the mix, and not to add reverb to the bass in-line before the amp or in the amp's fx loop. The reason is this: the 'normal' purpose of reverb is to create the illusion that the instrument or voice is in a different acoustic environment, anything from a closet to a club to a canyon. In order to get this effect on bass or guitar the reverb is added to the sound of the mic'd or speaker-modeled signal, so it sounds like an amp sitting in a space. Plus, even if you're using a mono input, any quality reverb has stereo outputs in order to correctly simulate an acoustic space. Since the DI of the 100T in the post position is both post power tubes AND speaker modeled, if you record it and add the reverb in the mix you are getting an excellent simulation of an amp in whatever space you set the reverb for. For rehearsing you could also patch the DI to a reverb then stereo out of the reverb to the board, but recording this way you are committing to the reverb. If you add it in the mix you can change it.
However, if you use a reverb pedal before the amp, you are not getting this effect. Not saying it's wrong and that it might not be a cool sound in certain situations, but there's a distinct difference. In this case you have the sound of a reverb'd bass playing through a mono bass amp, and the reverb on the bass signal is also being overdriven and eq'd by the amp and effected by any processor in the fx loop. And it is being distorted by the instrument speakers or speaker modeling. If the reverb is added to the recorded bass track or after the DI, clean reverb is being added to the sound of a bass amp, regardless if it is clean or distorted. And it is in stereo. That's the way it would be in the real world - the reverb itself would not be distorted or eq'd, the amp would. And the reverb would be coming from all around you, not just from the amp. Again, this is if you are going for the REALISTIC sound of a bass amp in a space. But you aren't always going for realistic, especially in recording, so it'd be good to get familiar with both sounds so you know when to use them.
Patching reverb inline before the amp would not work in most loud live situations. The amp is already working too hard to be able to reproduce a more subtle effect like reverb; it would only muddy the sound. In a case like Chris Squire that you cite, it's most likely that aside from his bass pedal rig one of either the Marshall or the Ampeg rigs is an effects amp, so one is always punchy and out front and not softened up by effects. Most of us don't have that luxury, and once you're cranking at volume with a single amp, and once cymbals start crashing, what may sound beautiful in the basement or the studio totally gets in the way live. Patching reverb post-DI or asking FOH to add reverb to your bass might work, but their problem is usually just the opposite; too much reverb already, don't need to add any.
Sorry to drag this so far off topic, but again thought some might be interested.

 

[Moosehead1966]

100t fits perfect!!! Stoked for u! Well back to work in jacksonville fl for two more weeks luckily I have my Hartke a70 down there so I can thump some but geez do I miss hammering my 100t 610 neo!! Nothin like it! View attachment 368506

MrCool84..That 610 cab is the thing of funny dreams I am having in the night. I totally want that cab! Thanks for the support. Hey, do you notice any difference using ported cabs with this head? Marc

 

[Tim1]

Moosehead, the head works as well with a ported cab as with sealed, it just brings out the relative strengths and differences of each cab. Depending on the cab and speaking very generally, with a sealed cab the low end is tighter and not quite as deep (as you would expect). I run my 100T into both a neo 610 and Bergantino sealed NV215 and 115 cabs. My favourite cab with the 100T is the Berg NV115 - just a matter of personal taste, of course.

 

[tombowlus]

My favourite cab with the 100T is the Berg NV115 - just a matter of personal taste, of course.

+1 I have a similar preference, but with the SB300.