Reducing Tube Amp Volume without Effecting Tone

[JFrankParnell]

May 12, 2006 11:50:43 GMT -5 UnklMickey said:

so now your drummer complains he can't hear you quite enough.

good! he'll play a little quieter.

and the bass player will turn down a bit too.
unk

BWAHAHAHAHAHAHAHHAHAHAHAHA!!!! The drummer? will play a little quieter? What planet you from, man?!?! ;D ;D ;D

Well I've never tried any of the power soaks and whatnot, but it is my belief, (and that of messers Fletcher and Munson [loosely translated]) that what you like about your tone is not just that of the tubes melting but the actual volume, spl, in the room. I just dont know that you can ever get "that" sound at lower volume. I bet you can get close enough for rock and roll, though.

[D2o]

Geez! quoting from a 4 year old post ... and by none other than Unk!

[ashcatlt]

chuck started it!

Both he and jfrank make good points, though I'd add that speaker excursion has something to do with it as well.

[chuck]

thats it ... blame the new guy !

oh , wait ... it IS my fault ... oh well , at least the discussion is alive once again.

you have to have a speaker that will function properly at very low power levels for " bedroom level " attenuation to sound awesome.
it IS possible to get incredible power tube saturation at "TV" volume .
if you love the tone of LOUD , then lower volume levels wont cut the mustard for you.

[sjsrocks]

Here is an attenuator I use on my Fender Blues Deluxe Reissue. It's a 500K CTS pot with a 0.001uf 100v Orange Drop Cap. Put it in the send/return and it works great.

[chuck]

how does that allow you to actually push your power tubes at low volumes ?

[D2o]

Sounds like a great idea.

I wish I had known about this last year. I had a Peavey Delta Blues 115 ... lovely tone, but it was just too much for the better half.

By the way, Welcome, sjs!

[D2o]

Jun 28, 2010 23:51:45 GMT -5 chuck said:

how does that allow you to actually push your power tubes at low volumes ?

If it does what I think it does ... if ... then it seems to me that it is a "volume control", after the volume control ... so you get to let loose all the tube's fury with the amp's volume control, and then tame the actual volume between where it goes out and where it comes back in.

So I think the external pot effectively attenuates the signal between the "head" and the "cab" (so to speak, only) and the cap is small enough that the tone is not changed much ... am I correctly understanding the concept?

What about using a resistor and a cap as a treble bleed? I've seen JohnH mention 220K and .001uF* (or even smaller) as a combination ... I wonder if there would be any benefit to that here?

... or has the cap got everything pretty well covered on it's own?

D2o

[chuck]

i assume " send / return " = effects loop in and out.

FX loops are between the pre and power amps ...

how can adding a volume control in the FX loop allow you to push your power section at a lower volume level ?
that sounds like yet another master volume knob ... and we all know that they only drive your preamp at low volume .

you have to attenuate between the amp and the speaker to get both preamp sizzle , and power amp saturation .

[D2o]

Jun 29, 2010 10:48:23 GMT -5 chuck said:

..... and we all know .....

Well, not all of us know.

I may be underestimating myself, but I am not ashamed to suggest that I know very little about amps - especially tube amps.

I'm looking forward to hearing more about this idea from sjs.

D2o

[D2o]

Jun 29, 2010 10:48:23 GMT -5 chuck said:

You have to attenuate between the amp and the speaker to get both preamp sizzle , and power amp saturation .

I don't understand (honest, I don't) why you couldn't crank the preamp for sizzle, and then use the external volume pot to limit the actual input that gets amplified by the power amp - so that you could crank the power amp too (for saturation, but manageable volume).

Maybe it's the low power of the preamp that enables this to work with a simple pot - without burning out the volume pot, instead of using an attenuator?

D2o

P.S. this, of course, assumes that any of my previous assumptions on which I am basing further assumptions upon are even correct! Talk about perilous!

[chuck]

an amp with a " master volume " does not really allow you to achieve cranked amp tones at lower volumes.
the amp companies just put that incorrect propaganda out there to sell amps.
the amp companies have shoved so many of their lies down out throats over the years ... all to line their pockets , while we have had to resort to horrible little pedals to TRY to make their over priced amps sound good.

with a master volume you can crank the PREAMP tubes , but that is not the same thing as cranked power tube saturation.

preamp distortion is only half of the equation ... they provide the sizzle , while the saturated / overdriven / pushed / cranked / whatever you like to call it, power tubes provide the smooth , thick , singing warmth and sustain.

in my opinion one without the other is .... lacking.
together they are AMAZING .

but , that is only my opinion ... whatever works to get YOUR tone is what is right for you.

[D2o]

Well said ... this could well be where the confusion sets in.

If I recall, the Delta Blues had a normal, pre and post - plus a channel switch ...

It seems to me that I used pre when I wanted some crunch, and that the normal and post didn't really do a whole lot other than make things get really loud (as opposed to make things break up the way I was expecting).

In fact, it behaved much like my 1980s SS Peavey amp, which has pre, saturation, and post.

That really is what has me intrigued ... I feel like I never got a chance to truly experience what all the fuss about tube amps is.

Heck, maybe I did experience that legendary tube tone and it's just not what it's cracked up to be?

Anyway, I look forward to sjs' further input (pardon the pun).

D2o

[chuck]

i need to try one of those FX loop gizmos for myself ....
i just do not see HOW they can actually do the job of a power attenuator.

they might be another option , something different , but not the same thing.

[chuck]

you want " legendary " cranked tube tone .... get a legendary tube amp and crank it.
yes , it is THAT simple.

not all tube amps are the same ... they each have their own unique thing going on.

pick a tube amp ,and ( after proper warm up ) start playing .
take note of the tone as you crank it.
as you get louder the tone thickens , sustains , and really sings.
you will find a "sweet spot " where it sounds the best for you.

a power attenuator allows you to play at the sweet spot , and control the volume from the speaker.

for some things preamp distortion is awesome , for others a solid state amp is better , it just depends on what works for you.

Jun 29, 2010 11:51:38 GMT -5 D2o said:

Well said ... this could well be where the confusion sets in.

If I recall, the Delta Blues had a normal, pre and post - plus a channel switch ...

It seems to me that I used pre when I wanted some crunch, and that the normal and post didn't really do a whole lot other than make things get really loud (as opposed to make things break up the way I was expecting).

In fact, it behaved much like my 1980s SS Peavey amp, which has pre, saturation, and post.

That really is what has me intrigued ... I feel like I never got a chance to truly experience what all the fuss about tube amps is.

Heck, maybe I did experience that legendary tube tone and it's just not what it's cracked up to be?

Anyway, I look forward to sjs' further input (pardon the pun).

D2o

[sjsrocks]

If you ever go on Ebay and see "The Volume Box" this is the same principle. The 0.001 cap is like a Tele Treble Bleed. It keeps the tone stable without muddin out. I tried the 220 resistor with it but there was too much treble when rolled back.
I'm thinking on buying "The Volume Box" just to take it apart to see what it's made of. I made it without the box to see if it works and it did quite well. I can crank up to 12 and get the grit, turn down the volume at the send/return and still have the grit. Roll off the guitar volume and it will clean up.
It's a simple and cheep solution. Try it and tell me what you think.
Steve

[sjsrocks]

I know it works with Fender Hot Rod Deluxe & Blues Deluxe Reissue.

[chuck]

my question is HOW it works ...

i just need to build or buy one and find out for myself ....

[D2o]

FWIW, selected posts from this thread about the volume box.

Word of warning:

These simple boxes will not generally work with tube driven FX Loops (not much will) because the impedance (resistance) of the pot and the cable capacitance will load the tube driving the SEND far too much, resulting in signal loss and poor hf response. This is fairly typical for most 'all toooob' amps frankly.

Remedy, build a 1M input impedance buffer stage into the amp just before the SEND jack. A TLO71 chip should do using the + input for the signal and O/P and - input connected together. You will need ±9 to 15VDC too! So starts to get difficult if your a 'homebrew' electronics guy! But you could rectify the heater voltages to get the supplies.

Hi Guys.

New poster here, hi.

The Classic 30 effects loop is Solid State, so that's why the Volume works without any need of internal modding.

But like said, it's only on the pre-amp stage, and typically that means: suck

That said, if you want to practice the Classic 30, this is a good compromise.
Why? Because how else are you going to hear an Amp without a master or headphone out?

As to Attenuators, they are the real deal at keeping all that tube crunch, but it comes at the cost of some tone suckage. Attenuators use Transformers, not pots, so they sacrifice less sound.

How much depends on how cheap you go. Weber sucks tone, which is why they put a tone knob to adjust it back up. Is it as GOOD as your amp at full power? No, but it's close for the money.

I have NOT tried more expensive attenuators (Hot Plate, et al), so I'll leave it to others to swear by them and how little they suck tone.

BUT, it SHOULD be noted here, and has NOT been noted, that reducing volume with an Attenuator or Volume pot is just adjusting the sound of your hardware! What most people love is Hardware PLUS Speaker, and speakers only sound good at louder volumes.

The point of an amp can NOT be separated from: the Speaker

If you want to get a better approximation of tone crunch and loud volume, then I suggest something like Vox's Tonelab stuff. You can use Headphones and go deaf with tube crunch that will fool anyone but a tone junkie. And probably even then once in a while!

Meanwhile, BUILD the volume box, if only to learn or practice your soldering and learn first hand what tone suck truly means.

Note: I find it interesting that the poster says, among other things, that “Weber sucks tone, which is why they put a tone knob to adjust it back up.”, implying that the tone knob restores tone.

Hi and welcome to the forum!

Since there are TWO types of attenuator on the market, Volume & Power, it is necessary, therefore, to differentiate between the two when we all converse. As it is, the term 'Attenuator' is being misunderstood by many players who think that 'Attenuator' only means 'Power Attenuator'.

Because musicians have corrupted the term, many electronics professionals can be confused by this over simplistic reference. I would like to suggest that we modify the term so that everyone will understand what type we are talking about. Maybe something simple like 'Vatt' or 'Patt' as an abreviated but distinct description for extra clarity?

With greatest respect to the new poster... Without several reads, I found it difficult to know what type of attenuator was being talked about, and at what point, from the post above that I am replying to.

I am writing a book for guitarists which helps them understand everyday electronics used by them. It deals with many of the topics which appear on this forum over and over again. It is a collection of articles and one was inspired by this thread. I have attached a draft copy of that article for your interest.

… and so on … worth a read. There is an article on attenuators in there as well - you have to log on to get access to it.

[chuck]

in my opinion if a POWER attenuator has EQ circuitry , it is to cover a design flaw .
try the Dr.Z Airbrake ... it is the most transparent POWER attenuator i have found on the market

and you DO have to keep the speaker in mind when you REALLY attenuate the amp's output.
every speaker needs a certain amount of power to drive it , and when you attenuate your amp's output below that number the tone from the speaker sucks.

what makes tube amps special is the saturation when you crank them puppies ...
if you are not pushing your power tubes , why have a tube amp ?
tube amps are expensive to maintain ... if you are not taking advantage of the magic that only tube amps have to offer then why waste the dough ?

[ashcatlt]

Jun 29, 2010 11:19:38 GMT -5 D2o said:

I don't understand (honest, I don't) why you couldn't crank the preamp for sizzle, and then use the external volume pot to limit the actual input that gets amplified by the power amp - so that you could crank the power amp too (for saturation, but manageable volume).

It's because the power amp section is always "cranked"! Unless I'm horribly mistaken, the power section in most guitar amps has a set gain factor by which it tries to multiply the voltage it recieves from the previous stage.

Both the Master Volume and this effect loop attenuator thing simply turn down what's being fed from the preamp section before it gets to the power section. There's no knob on the thing that lets you change the amount of gain applied by the power amp.

All amplifier circuits have an upper limit on the amount of voltage they can output, which is set mostly by the amount of "rail" voltage supplied to the device. The kind of distortion we've been talking about here comes when the input voltage multiplied by the gain factor exceeds this upper limit. The amp tries to follow the wave up to its peak, but it can't. It hits the upper limit and stays there until the wave comes back down.

Let's just say that our power amp has a gain of 100, and a rail voltage of 250V. If the preamp outputs a 1V signal, the power amp will be acting within its linear range and there will be no distortion. If the preamp sends out a 3V signal, though, the power amp will try to output 300V and fail, which is apparently this "holy grail" sound that we're chasing here. Now, if you stick a pot between after the preamp and divide that 3V back down to 1V, where do you suppose we end up?


Then there's the thing with the power transformer saturation and the rectifier sag, both of which depend basically on how much voltage the power amp is trying to provide.

[D2o]

Thanks, ash

I will re-read this thrice in the hopes of fully getting it, but I think I know where I blundered.

I started off by referring to the “pre” and then I incorrectly used the term “power amp” that was introduced.

My incorrect interpretation of the term “power amp” was that it was akin to either the “post” or, more likely, “normal” that I later referred to with the Delta Blues … it isn’t.

So the power amp is, well, “what it is” … you turn it on and it’s on, and that’s that. You use the other controls to feed what goes into it. It’s kind of like the drum of a clothes dryer – no matter the heat setting (pre, post), the drum rotates at the same speed (power amp). Do I sort of have the idea now, or have I taken an excursion to *Chattanooga©? (*I have vicariously obtained expert training on that)

So my interpretation of what was happening is that the guitar signal goes:

- from the guitar
- to the amp input
- to the pre (and maybe post)
- blasted out the effects send
- “attenuated” by the external volume pot
- attenuated signal received in the effects return
- attenuated signal managed by (maybe the post and) master volume
- … what the hell am I going on about again?

Oh! Yes, so I think I meant to write

I don't understand (honest, I don't) why you couldn't crank the preamp for sizzle, and then use the external volume pot to limit the actual input that gets amplified by the power amp - so that you could crank the post too (for saturation, but with manageable volume levels via the normal/master volume).

[/size]

Is that a more appropriate / accurate way of asking what I think I’m asking?

Thanks again,
D2o

[chuck]

No matter what the seller on Ebay claims / implies , the volume box does not allow you to drive the power section at low volume levels .
It allows you to drive the preamp harder and control it with the knob ... which is mostly useless.
I did say mostly .

Keep in mind that tube and solid state amps are different beasts .
Generally , you WANT to overdrive a tube power section ... but you do NOT want to do that with a solid state amp.
There ARE exceptions to the rule.

sometimes a distorted SS sound is what works ... it just depends on what you are looking for

[JFrankParnell]

There was this Ampeg VL-503 that is pretty cool. It has pre and power amp volumes, with an attenuator, too. I only got to play it for a little bit, in the dude's appartment. So we had the pre and power dials on 12 and used the attenuator. I just remember it was freaking insane sounding, like you could hear the tubes melting, the distortion was so gnarly.


www.leejackson.com/VL503.htm


whoops! can you put size attributes in the img tag? fixed.

[chuck]

power attenuators ARE awesome gadgets arent they ?

[newey]

AFAIK, you have to do your resizing in photobucket (or whatever you're using). I don't think the BBC code will allow resizing of a JPEG.

But you could give it a shot . . . either way, please do resize it.

[sumgai]

jfrank,

That Ampeg's Attenator knob? It's nothing more than a "final" master volume pot. The Slope and Presence knobs are really "Gain" and "Contour" knobs for yet another pre-amp stage found just before the power-amp.

This thing was insane, to be sure, but once again, Marketing trumped common sense when it came to labeling the knob functions. Sigh.

When seeing items like this, it helps to remember that a true power attentuator is attempting to control beaucoup watts. A normal pot is good for about a half-watt or perhaps a full watt, under the best of circumstances. High-power pots are very expensive, and need lots of air (cooling) in order to not become part of the smoke-and-mirrors show. (Emphasis on the smoke portion.) This why many external attenuators use switches instead, selecting between various fixed resistor values. Cheaper, and easier to keep cool.

HTH


sumgai

[JFrankParnell]

ahh, the switching thing, that explains this z-brake thang:

[chuck]

ahhh ... the amazing Air Brake ... you should try one

[elderik]

HI all,
Anyone out there tried the London Power Scaling kit recently?

Same old issue with my H&K Switchblade 100W Combo - sings loud but its too beastly for small rooms.

Thanks