Low Volume Bass response

[jmv]

I've been noticing this more and more recently, as i get more familiar with my amp.

When i'm using my amp (my '66 bassman) at lower volumes (not nessesarily queit, but low enough to get a clean sound), i have problems with getting a nice full bass response. Could this be attributed to something wearing out on the amp, such as the output tranny or the speakers?? And also, i notice it more on the A string... perhaps its just those higher frequencies don't project as much, or maybe i need heavier strings... I use 9's on my les paul, but i'm no stranger to heavier strings, as i regularly use 11's on my strat. I don't seem to notice this problem as much when i crank it up for distortion, but thats perhaps because its so loud i FEEL it, which i suppose could make the problem seem not as bad as it actually is....

Any suggestions??

 

[Scott_F]

Re: Low Volume Bass response

it's the nature of the human ear. ever notice how a nice home theater system has the little bass boost button for low volume levels? They call it "Loudness" on my of them.

Same thing you are experiencing if you ask me. At low levels you are probably going to have to crank up the bass knob a bit. I would not worry about it too much if I were you. I seem to remember you telling me that they power tubes in it were new when You got it. So, it's unlikely that the tubes are starting to go.

Tube amps are meant to be played loud IMO. You just have to make a few concessions when you turn it down a lot.

 

[flank]

Re: Low Volume Bass response

the more you turn that volume pot down, the less frequencies are getting through......could, although simply put and me having no electrical experience, just be the reason.........when you turn that volume pot up, more of the frequencie is getting through, and more bass frequency it getting through........like scott said, tube amps are meant to be turned up for the full power and frequencies to show through

keep in mind i was just babbling there and using my limited experience to try to figure out your problem........but more or less, you will just need to turn it up to hear everything

 

[Guitarist]

Re: Low Volume Bass response

Tube amps are meant to be played loud IMO. You just have to make a few concessions when you turn it down a lot.

I'd recommend using a nice overdrive in conjunction with your Bassman. Even not necessarily distorting the signal - lower the frequencies, put the drive very low, and the volume boosted. It'll give you a thump without the mush.

 

[jmv]

Re: Low Volume Bass response

Okay, all the things you guys are saying make sense.

The thing is, however, this problem is happening at a level that is right before the amp starts to break up. So, if i turn up more, it'll be dirty, and if i boost the signal with a pedal, it'll get dirty... i can turn up the volume on the amp and turn down the guitar, but it'll be the same problem.... Which means i can't really get nice clean tones...

Perhaps i should invest in a 12AT7 for the phase inverter, rather than the 12AX7 in there now, for more headroom, and i can see if that helps the problem... but then, i won't be able to get the breakup at semi-manageable volumes.... grr, oh well, its a trade-off, i guess i'll just try it and see which works best for me. But first i gotta get some cash....

 

[Kent S.]

Re: Low Volume Bass response

it's the nature of the human ear. ever notice how a nice home theater system has the little bass boost button for low volume levels? They call it "Loudness" on my of them.

Same thing you are experiencing if you ask me. At low levels you are probably going to have to crank up the bass knob a bit. I would not worry about it too much if I were you. I seem to remember you telling me that they power tubes in it were new when You got it. So, it's unlikely that the tubes are starting to go.

Tube amps are meant to be played loud IMO. You just have to make a few concessions when you turn it down a lot.

Scot's answer nailed it, yeah sure there could be something going on with your amp, but what Scott is referring to are the equal loudness phon curves, established by Fletcher and Munson I believe (there were two other gentleman alsoin and earlier experiment) ... basically our ears hear midrange with the greatess sensitivity, and do not respond as well to high and low frequencies until they become greater in sound level pressure (SPL), then out hearing starts to flatten out a bit, this is also the reaso nwhy SPL Meters ahave various *weighting curves* to account for various sound level ranges. The effect is also noticed if you mix a recording at high levels (loud)...whenyou play it back at low volumes it will be lacking in bass (and some highs), if you mix at low levels (softly) then when you listen to it loud it will be to bassy (and a bit overly bright). Something that you could try (clean anyway) is at low volumes to lower your mids and boost your bass and treble, then raise your mids for louder levels ... really playing with your mid control more so than the other two ... the reason has to do with the way that the fender tone stack is set up, the mid control actually just controls the amount of cut of midrange, and corespondingly the *difference that the treble and bass controls can *appear* to boost in relation to the mids. FWIW.

 

[jmv]

Re: Low Volume Bass response

Scot's answer nailed it, yeah sure there could be something going on with your amp, but what Scott is referring to are the equal loudness phon curves, established by Fletcher and Munson I believe (there were two other gentleman alsoin and earlier experiment) ... basically our ears hear midrange with the greatess sensitivity, and do not respond as well to high and low frequencies until they become greater in sound level pressure (SPL), then out hearing starts to flatten out a bit, this is also the reaso nwhy SPL Meters ahave various *weighting curves* to account for various sound level ranges. The effect is also noticed if you mix a recording at high levels (loud)...whenyou play it back at low volumes it will be lacking in bass (and some highs), if you mix at low levels (softly) then when you listen to it loud it will be to bassy (and a bit overly bright). Something that you could try (clean anyway) is at low volumes to lower your mids and boost your bass and treble, then raise your mids for louder levels ... really playing with your mid control more so than the other two ... the reason has to do with the way that the fender tone stack is set up, the mid control actually just controls the amount of cut of midrange, and corespondingly the *difference that the treble and bass controls can *appear* to boost in relation to the mids. FWIW.

huh... thanks for the explanation, thats actually really cool, and i didn't know that, and that'll be usefull.... but i don't have a mid control.

But i didn't know the things about spl and whatnot, that really will come in handy.

 

[Kent S.]

Re: Low Volume Bass response

huh... thanks for the explanation, thats actually really cool, and i didn't know that, and that'll be usefull.... but i don't have a mid control.

But i didn't know the things about spl and whatnot, that really will come in handy.

You DO have a mid control, it's just that it's preset ( a resistor), I apologize as I couldn't remember if that amp had a mid knob of not ... however it still stands that you have a preset amount of mid cut, in your case you'll have to swing your bass and treble controls (hey you already knew that), but what you may not know is that the treble control on a fender style (or marshall, or vox .. except for a few design departures) is a type of balance between the bass and treble, not just a treble amount control ... you'll have to play around with it a bit, maybe trying to get the best tone you can at low volume, and then just leaning the bass off at higher levels.
BTW, if anyone is curious where the *flat* spot is on a fender eq (with bass,middle,treble) it's mids @10, and treble and bass @ 0 ... sounds weird but it's true. The fender eq also can't cut treble, it's more of an illusion ... I'm not going into that, but I'll try and dig up a text I had on it, and post it ..it concerns the Baxandal eq design (similiar the fenders E -series), wait a second ... your amp might have that layout on second thought, hhmm.
Just for my curiousity what was the exact amp model again? Thanks.

 

[jmv]

Re: Low Volume Bass response

Its a '66 fender bassman halfstack, labeled as circuit AA165, but more likely circuit AB165....

Thats real interesting about the way those tone controls work. If you have a specific reference you could link to, or some text i could buy, that'd be awesome, all that stuff is really interesting.

 

[Kent S.]

Re: Low Volume Bass response

Its a '66 fender bassman halfstack, labeled as circuit AA165, but more likely circuit AB165....

Thats real interesting about the way those tone controls work. If you have a specific reference you could link to, or some text i could buy, that'd be awesome, all that stuff is really interesting.

Well, you can go to ... www.ampwares.com/ffg/index.html
To the Fender Amp Field Guide and look up Blackface Bassman ... scroll down and click the schamatic for AB 165. As far as proving to you *how*they work ... well I'll do you one better ... for free ... go here ...
www.duncanamps.com/index.html ... an download the Tone stack Simulator program ... Select Fender model, then you can adjust you cap values per the BF schematic, and your pot values, as well as taper, since you don't have a mid control ... put the mid control shown at *10* and then set the pots value for 6.8K ohms (6,800 ohms). Both channels are identical except that the bass channel has that deep control, and a .1uFas the *mid cap*, and the normal channel has a bright control , and a .047uF as the *mid cap*... err... switch. The bright switch just switches in a cap to boost the highs at lower volumes, once the volume is at *10* it has no effect, the lower the control is set, the more effect, the higher the less.
The deep switch however is either on or off. It runs a .1uF cap to ground, I'd have to look again to see ewxactly what they are doing there, as it's a different porcedure than what they did on some other Deep switch designs.
As far as the Baxandal eq arrangement that's used (at least in a similar fashion) on some of the older tweeds, champs, and I think some brownfaces ... maybe not there ... So many changes, so many models ... you get the picture. Anyway, I really have to try to find that article, as I printed it out, but deleted the text, and where i got it from ,I'll keep looking though. The Bassman is the *regular Fender tone stack*, You could you the VOX on that simulator ... but the source impedace of the preceeding stage is different so, it will shift all of the filter frequencies, so use the fender and make the adjustments. That will let you see what the eq is doing. For any more on the how, ... you'll have to invest in a good book on electronics theories and applications. :cool3:

 

[jmv]

Re: Low Volume Bass response

cool, thanks a bunch!!