Fender Bandmaster Amp (early silverface) - what are they like??

[the guy who invented fire]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

I think at a point in history many players were looking for more punch, more stiffness more authority if you will and a lot of the older small and mid size amps didn't have that.

Now, over filtering a Bandmaster won't make it punch like a 100 watt metal front Marshall but for some players it might get them a step close to that.

Personally I like to get the nice compression and sort of clay like feel from an amp like this once it's cranked up...almost like you can shape the notes with your flat pick attack and finger vibrato...that quality goes away with over filtering...

 

[Stratman]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

You are right, I was typing from memory

TDL 5005 should have been TFL5005D.

Yes, it has reverb and I still feel that is is the better Bandmaster amp!

Now, having stated that correction, your post is not exactly in line with the spirit of this forum, something that I in the past have been also guilty of - new year for your change don’t YOU think? I have already made mine!

 

[Lewguitar]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

Personally, I'd rather own a Bandmaster Reverb. Even though the master volume is almost useless for getting the tones I like and I'd probably mod it!

 

[RayBarbeeMusic]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

Let me correct some technical things since I work on these for a living.

As far as "over-filtering", as a general rule, I am against it altogether. It makes the amp feel stiff and solid state-ish, there is a reason vintage amps feel the way they do and part of it is because designers weren't putting mega capacitance in the first few stages to try to squeeze a few micro DB of noise floor out of them the way many seem to do now, when proper design in the first place would make the amp plenty quiet. There are a lot of posts around the web and in books by 'techs' who recommend over-filtering an amp to make it 'quiter' and have 'more bass response'. I do not believe anyone recommending that is a serious player, if they were, they would immediately notice the degradation in feel of the amp from doing that. If you really want that, get a solid state amp with 2000uf or more in the power filters. For demonstration, get a 200uf-1000uf cap and put it in the first stage of your tube amp (solid state rectifier only) and see what it does. Bigger caps hold more juice, BUT they also charge much slower, they just do not feel the same. Also, a vintage Fender has overwhelming bass response into sub-aural frequencies from the circuit already, I don't know why you'd need more, and those are limited by the power amp and by the speaker anyway. What you end up getting is just stiffness. The only reason I'd ever recommend bumping up capacitance is in the rare case of ghost noting, and even then as little as possible (and I'd probably suspect the speaker long before the caps unless the caps had drifted way down).

Having said that, 2x100uf in parallel is 50uf, stock values were nominally 70uf (not available anymore) in parallel for 35uf, BUT, the over under tolerance on those stock caps was HUGE, meaning they might come in at 55uf or 110uf a piece when brand new. Personally, I use 80uf in there when I do cap jobs, but 100uf for each cap is in no way "over-filtering", it is within the tolerance of the orginal caps. When I think of 'over-filtering', I think of designers who use 100-250uf (total, not paralleled) in the first couple stages, sometimes more. I could name names but I'll refrain.

Also, there are a whole slew of reasons why a cranked Bandmaster doesn't sound like a BF Bassman, the power supply being the least of them (the phase inverter and pre-amps were very different on the Bassmans). Yes, a BF bassman had bigger iron, but that doesn't weigh in as much as the other differences. Take it from someone who has done a LOT of transformer swaps.

A BMR is probably my favorite classic Fender, along with the closely related Pro Reverb. My personal BMR has a blackface Pro Reverb circuit (minor, minor changes required to any Fender circuit except the Bassman to make that happen). Early BMRs did not have Master Volume, and on any SF Fender that DOES have master volume, it is simple to remove it, or simply leave it on 10.

 

[glassman]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

As far as "over-filtering", as a general rule, I am against it altogether. It makes the amp feel stiff and solid state-ish, there is a reason vintage amps feel the way they do and part of it is because designers weren't putting mega capacitance in the first few stages to try to squeeze a few micro DB of noise floor out of them the way many seem to do now, when proper design in the first place would make the amp plenty quiet. There are a lot of posts around the web and in books by 'techs' who recommend over-filtering an amp to make it 'quiter' and have 'more bass response'. I do not believe anyone recommending that is a serious player, if they were, they would immediately notice the degradation in feel of the amp from doing that. If you really want that, get a solid state amp with 2000uf or more in the power filters. For demonstration, get a 200uf-1000uf cap and put it in the first stage of your tube amp (solid state rectifier only) and see what it does. Bigger caps hold more juice, BUT they also charge much slower, they just do not feel the same. Also, a vintage Fender has overwhelming bass response into sub-aural frequencies from the circuit already, I don't know why you'd need more, and those are limited by the power amp and by the speaker anyway. What you end up getting is just stiffness. The only reason I'd ever recommend bumping up capacitance is in the rare case of ghost noting, and even then as little as possible (and I'd probably suspect the speaker long before the caps unless the caps had drifted way down).

100% agreement...no argument here.

Having said that, 2x100uf in parallel is 50uf, stock values were nominally 70uf (not available anymore) in parallel for 35uf, BUT, the over under tolerance on those stock caps was HUGE, meaning they might come in at 55uf or 110uf a piece when brand new. Personally, I use 80uf in there when I do cap jobs, but 100uf for each cap is in no way "over-filtering", it is within the tolerance of the orginal caps. When I think of 'over-filtering', I think of designers who use 100-250uf (total, not paralleled) in the first couple stages, sometimes more. I could name names but I'll refrain.

I agree with this but it should be noted that Ruby offers a 70uF @ 350v axial that measures and performs really well. 68uF @ 350v radials are available from a number of suppliers. Personally, I've used (and stock) them all but generally use either TVA1613s or TVA1620s depending on how the amp is used with the TVA1613s being used 90% of the time.

Also, there are a whole slew of reasons why a cranked Bandmaster doesn't sound like a BF Bassman, the power supply being the least of them (the phase inverter and pre-amps were very different on the Bassmans). Yes, a BF bassman had bigger iron, but that doesn't weigh in as much as the other differences. Take it from someone who has done a LOT of transformer swaps.

I just can't agree with this. Though both amps (normal channels only) are structurally different, they are, for the most part, functionally very similar; both produce a remarkably clean signal through the preamp and both PIs behave in a similar manner when overdriven. The main differences you hear ARE the power supply; when you Thevenin a tube circuit, you HAVE to include the power supply, unlike a SS circuit where the power rails are technically held firm. There's a whole lot of signal communicated through the power supply, particularly in the preamp stages. You can completely change the whole character of a Fender amp with power supply changes and without ever touching the primary signal circuit.

Transformers are probably the most misunderstood part of a tube amp and transformer manufacturers don't help this much by not reporting the characteristics that are most important in a guitar amplifier application. Coupling characteristics are NEVER spec'd nor are the changes that occur at different signal levels. I've said this before...size has NOTHING to do with coupling efficiency or characteristics; larger size WILL reduce the effects of eddy current losses but not on hysteresis losses...it can actually make them worse. The latter is FAR more important when it comes to guitar amplifier applications. The engineering specifications for all transformers (power and output) are given at constant level...an environment that none of them exist in.

Note: I'm not trying to start a fight here...I'm just offering information that I've picked up from 18+ years repairing/building guitar amplifiers and 20 years as a quality/application engineer in the magnet wire industry, serving, among others, the transformer industry.

 

[RayBarbeeMusic]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

I'm not trying to start a fight here...

Nor am I, but:

1) The phase inverter differences in a BF Bassman vs. any other BF Fender combined with the extra tube stage, negative feedback, etc. make a whole lot more difference in why a Bassman sounds different than other Fenders than the Iron does. You can take the identical amps (which none ever are due to component tolerance) and switch OTs and the difference may or may not be audible, and often falls into the 'subtle' category, but those circuit differences count for a whole lot more.

2) My philosophy is, never advise a client to do anything I wouldn't do. If I bought that BM, I wouldn't bother to change from 100uf to 80uf caps, just not audible, and I wouldn't tell someone "you need to rebuild that" because of it. I'd tell them it needed caps if they hadn't been updated, but in this case I'd tell them it was good that the caps had been updated otherwise it would have to be done. Given the huge tolerance variance on electrolytics, you'd have to prove to me you could even hear/feel a difference between a nominal 50uf and 35 or 40uf, which would overlap each other given tolerances anyway. I'm very sensitive to such things and I doubt I could.

If you wanted to change the feel of the amp, you'd get a lot more bang for the buck changing the Cks to 10uf or even 4.7uf non-polar than you would changing filter caps. The amp wouldn't be wasting it's time trying to push so many sub aural frequencies and would still have plenty of whoomp in the lows.

 

[glassman]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

1) The phase inverter differences in a BF Bassman vs. any other BF Fender combined with the extra tube stage, negative feedback, etc. make a whole lot more difference in why a Bassman sounds different than other Fenders than the Iron does. You can take the identical amps (which none ever are due to component tolerance) and switch OTs and the difference may or may not be audible, and often falls into the 'subtle' category, but those circuit differences count for a whole lot more.

As far as the OT goes, I'm in agreement with you and I think you may have misunderstood the intent of my comments; it's become increasingly popular these days for guys to "up the size of an OT"...a practice I discourage, especially in a classic amp that was designed around a particular OT. I'll also agree with you on the feedback insertion point of the AB165 vs the AA165; the AB165's "harder" insertion point definitely adds more compression in comparison to the AA165's "softer" insertion point. I still stand by my original assertion that though structurally different, the PI's are functionally the same. The AB165's third stage has a gain factor of slightly over 1, thanks to localized feedback; it doesn't distort regardless of signal level (within practical parameters) but it does invert the signal and it does widen bandwidth. The AB165 reduces the bandwidth of the normal channel with the power supply (bass frequencies) and the 500pF cap bypassing the plate resistor (treble frequencies). There is a difference in "feel" between the two but it is mostly due to the power supply differences; swap the 8uF for a 20uF in the AB165 and you get a whole different amp...muddy bass and all.

2) My philosophy is, never advise a client to do anything I wouldn't do. If I bought that BM, I wouldn't bother to change from 100uf to 80uf caps, just not audible, and I wouldn't tell someone "you need to rebuild that" because of it. I'd tell them it needed caps if they hadn't been updated, but in this case I'd tell them it was good that the caps had been updated otherwise it would have to be done. Given the huge tolerance variance on electrolytics, you'd have to prove to me you could even hear/feel a difference between a nominal 50uf and 35 or 40uf, which would overlap each other given tolerances anyway. I'm very sensitive to such things and I doubt I could.

I agree with this in principal...I can't hear a difference either...but I have a few customers who can. I learned this the hard way early on and changed my default to assume that everyone but me can hear/feel a difference. It has served me well. It really depends what amp and how it's used with the importance increasing with lower wattage amps. Capacitor tolerances are one of those things where the definition and context has shifted over time. The stated tolerance is a temperature dependent derating and is applicaple at the rating temperature. Most modern capacitors are 105C rated with some rated at 85C; the capacitors used in older amps were often rated at 65C with some as low as 45C. Capacitor values always reduce with temperature; this means that if you replace a 65C rated cap with a 105C rated cap of the same value, you have significantly increased the the filtering at normal operating temperatures. This may or may not be of any consequence but I do remember the old days when guys preferred the way their amps responded when they heated up...the "third set" tone/feel was always their favorite...I never hear this from guys with newer amps. Back in the mid-90's, when everyone was trading in their classic Fenders and Marshalls for new amps, all the trade ins from local stores came through my shop. With permission, I was allowed to blueprint some of the best examples. i learned a ton and started applying what I learned to my repairs...it has worked out very well.

If you wanted to change the feel of the amp, you'd get a lot more bang for the buck changing the Cks to 10uf or even 4.7uf non-polar than you would changing filter caps. The amp wouldn't be wasting it's time trying to push so many sub aural frequencies and would still have plenty of whoomp in the lows.

We'll just have to agree to disagree on this point...please understand, I don't think you are wrong...it's just that my experiences have led me in a different direction.

 

[Lazarus1140]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

I wish I knew enough about circuits to fully appreciate what you guys are talking about. I could definitely use the education, but I'm not quite up to kindergarten in my study of amp circuits. Nonetheless, I am enjoying this dialog immensely!

 

[glassman]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

Nonetheless, I am enjoying this dialog immensely!

I am too.

RayBarbeeMusic is obviously a tech at a highly reputable business so he most likely is pretty darned good at what he does. I enjoy talking tech with other techs since we all have different clientele who drive us in different directions. We can learn a lot from each other as long as we don't let our egos get in the way.

 

[Jeffblue]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

I own a Fender Silverface Bandmaster Reverb and I like it a lot. Couldn't imagine letting it go.

 

[crusty philtrum]

Re: Fender Bandmaster Amp (early silverface) - what are they like??

I can't help thinking that it would be easy enough to disable the normal channel and rewire it so that the normal channel's first valve became the missing gain stage in the reverb circuit for the tremelo channel, thus adding the extra gain that a reverb-model has. The mod would be easily reversible and no holes would need to be drilled. Just a thought.