That certain point...

[daz]

You know what i mean.....that point in your amp's master volume where when you are at very low volume and as you keep turning down it hits a spot where very abruptly the tone goes completely mushy and you can no longer hear any of the details in the tone that make it good. This is VERY low, but for me it's the level i have to use where i live. Bearing in mind that it's NOT the pot taper (i found the best taper already after going thru many pots)

My question is whether you think like i do that it is the speaker thats to blame because it's too low a volume and the speaker just hits a point where it stops responding normally. And if so, does anyone know of a way around this? Please note that i AM NOT asking for a way to make the amp sound great or even good at that volume because i know thats not possible. I'm just asking if there is a way you can think of that will improve it to any degree, because where i live i cannot practice at all at this point. (yes, i do use phones and a modeler at times, but that gets tiring) I've thought about a low SPL/wattage speaker, but i really don't want to spend $50-100 a couple or three times to find thats not going to work. So while i doubt there is an answer for me even for a tiny bit of improvement, i had to at least ask.

[Steve Conner]

I think I know the effect you mean. On my amps the point for playing late at night is about a gnat's ball-hair off 0 and you have to kind of prod at the volume control to get it there.

The only way I know around it involves renting a rehearsal room for the evening, or taking the day off work and letting it rip while your neighbours are out.

I think there's just a law of nature that says that electric guitar is going to suck unless it's loud. They're like motorcycles: if a Harley made a tiny farting noise that you could barely hear with your ear to the tailpipe, I don't think they'd sell half as many.

Turning the treble and presence up on your amp might help, though. Or maybe making a simple attenuator with a couple of power resistors to knock 20dB off the signal to your speakers. This is the electric guitarist's version of putting a sock into a trumpet.

[daz]

yeah, i've done that. In fact i made several 2 resistor ones and one of those ones with 4 thats supposed to sound better but DOESNT ! (at least for me) They just make the amp so muddy i have to turn up even louder to hear any definition.

I think the master and VVR together are doing a reasonable job, but the problem is my preamp starts to lose gain and sound bad with the VVR way down. And for some odd reason when i tried to scale the PA only it didn't work. I'm quite sure i did it right...I took the B+ and Y'd it off to 2 diodes, one going to the VVR and out of that to the 32/32uf can and on to the screens. After that i disconnect it before the PI and take the second diode off the B+ Y and connect that to the PI node and from there as normal to the rest of the pre. That way only the PA should be scaled. But when i do that i can turn the VVR all the way down and i hear no volume difference ! It's wierd. But if i could figure out how to do the PA only i think i'd be much better off, maybe even real good between that and the master.

[Enzo]

Look up "Fletcher Munson curves" and see if that adds anything. YOur ears do not hear the same at different levels. That is why they add the "loudness" switch to stereo receiver amps. Perhaps this effect is involved.

[daz]

I have no doubt thats part of it. But i also have no doubt that it's not the only thing. I have gotten very low volume tones that were better than this in the past. There are many factors some of which i have thought of and some i'm sure i haven't. But at this time with these guitars and this amp in this room i Thats why i'm asking....hoping for a suggestion that turns out to be the right one. Like i believe i said tho, i'm not naive enough to believe i will get very good tone at such low volumes. Usable is all i ask for, and again, if i could figure out why scaling the PA only isn't working i think i'd have it nailed.

[hamfist]

yeah, i've done that. In fact i made several 2 resistor ones and one of those ones with 4 thats supposed to sound better but DOESNT ! (at least for me) They just make the amp so muddy i have to turn up even louder to hear any definition.

I suspect an attenuator is what you need, but building a half-decent attenuator is not easy. Just look at all the commonly available commercially available ones. They all give terrible tone with heavy attenuation.
My Ultimate Attenuator is night and day better than a Hotplate for example. You need the right attenuator. The only truly great ones out there that I know of are the UA, the Ho (same as the UA, but built by mr Ho in Canada), and the Richter Control.
If THD can't really get anywhere close, then I would imagine it would be pretty difficult to build anything half decent oneself.

[R.G.]

Here's an interesting thought:

Listening to something like an ipod or a CD player through headphones, can you hear really good recorded tone?

If that's possible, then it's *possible* to get good tone at low volumes. It's just difficult.

If the tone characteristics you want only happen at some specific point on the power curve of the amp and beginning of breakup on the speakers, then it will be impossible for a master volume to get you the same thing - you're not operating the amp and speakers at the right place.

Fletcher Munson gets into it as well. So does the acoustic response of the air in your lungs.

It might be good to approach this a different way - what is it that is not the same if you are playing with a very small master volume level, considering everything?

[daz]

what is it that is not the same if you are playing with a very small master volume level, considering everything?

Well, thats why i suspect the speaker first and foremost. At that point i think the speaker has too little power to it and it stops responding normally. That why i felt it might help to use a speaker with low power, low SPL, or both.

[PRNDL]

There's several things involved:
- the speaker
- the pot's resistance/impedence, which is on a preamp tube grid
- the signal to noise ratio

The speaker is certainly the easiest to test. Weber makes an inexpensive 6" 15 watt alnico that sounds fantastic. It's worth a try.

Turning a pot to near zero decreases its resistance. In the case of a bright cap, the highs get rolled off. When its connected to the grid of a preamp tube, the internal capacitance of the tube is the "bright cap". That's why amps sound better on 10 (or 11), and why attenuators sound better than master volumes.

Low volume signals are easily lost in the noise, although this doesn't seem to be the issue you describe.

Another solution is to substitute low power output tubes. Groove Tubes makes a substitube that does this. The tone, however, is dependent on that tube, which is usually different.

What amp are you using?

Another possible solution would be to get a tube preamp connected to a low power monitor amp, like a T amp, and a pair of good speakers. Imagine a TS808 to a stereo chorus to the T-amp ... it could really sound nice.

[daz]

It's a 18 watt i converted to 6v6.

[PRNDL]

Is that certain spot based on clean tone, or is it where the amp begins to break up?

Some people use a pedal with a tube amp at low volumes, others prefer to connect guitar to the amp. With the former, the specific pedal has an effect on the tone.

Also, as the amp is turned down you usually get cleaner cleans and less squish and fun from the amp.

With the latter, the solution is a lower power amp (i.e. single-ended 5W champ, etc)
Some boutique builders are now making low power amps.

My basic question is what are you missing in the tone?
- squishy fun (usually why people like 18 watt amps)
- that point of clean with neck, rock with bridge pickups
- highs & treble, or certain harmonics, or the sound of the guitar itself
- lows and thump

[daz]

Distortion tone, and It just turns to mush. Take any tube amp you have with a master and turn the master down slowly till it hits a sort of "on/off" point. thats what i'm talking about, tho it is NOT the pot taper because i found the best pot for that issue. But after that certain point the tone changes completely to undefined mush. And the VVR works to make the issue much better except that when turned low it kills the preamp gain due to the voltage being so low. Thats why i posted that new thread about the problem with the VVR because if i can figure out how to make scaling the power amp work then i think i'll be all set.

[chipaudette]

In reference to the comment about "turning the pot near zero decresases its resistance", I've always been interested and concerned about this. The concern is that the wiper to ground resistance is so low that it might affect the frequency response of surrounding elements (like near-by caps or the following tube stage)

In the case of the Marshall 18 Watt amps, there is sometimes a cap following the volume knob just before the phase inverter (I'm assuming this schematic). When the volume knob is really near zero, is the effective cutoff frequency of this cap affected? I don't know.

Related, I've always been concerned about the quality of the pot itself when turned down this low. Is the very end of the resistive strip within the pot built with any manufacturing controls? It could be total crap and affect the tone.

So, there are two things to try to discover or eliminate these two problems. For issue (1), the low resistance problem, insert a 100K resistor after the pot. So, unsolder the wire connected to the pot's wiper, solder a 100K resistor to the wiper, and solder the wire to the end of the resistor. This'll keep the resistance "looking" high to the rest of the circuit even with the pot turned way down. How does it sound? If it sounds better, then leave the resistor in place...that's your solution. It should have little effect (no effect?) at normal volumes.

For issue (2), you need to get the low volume without being way down at the end of the pot. To do this, put a big voltage divider just before the pot. If you've got a 500K volume pot turned way down to so that it's only got, say, 10K between the wiper and ground, then you've got a big 50:1 cut (34 dB) reduction in your signal. If you put in a voltage divider that does, say, 25:1, then you've only got to do a 2:1 cut via the volume your pot. This means that you'll be able to turn the pot up to be within the proper part of its useful range. It might sound better.

To do a 25:1 voltage divider, try a 1M for the first resistor and 40K for the second resistor. Unsolder the first tab of the volume pot (the "top" of the vol pot) from the circuit. In its place, connect one end of the 1M to the circuit and connect the other end of the 1M to the 40K resistor. Connect the other end of the 40K resistor to ground. Finally connect the top of your volume pot to the joint between the 1M and the 40K. Fire up the amp and see how much quieter it is. It should really kill the volume on your amp -- big time. You'll probably have to open up the volume knob to somewhere between "5" and "10" to hear it. Does it sound any better than the original configuration where the volume knob was way down at its bottom?

If it does, then you know the crappy sound was due to the low end of the pot. You won't want to leave the voltage divider in there so pull it out and try replacing the volume pot with a different one. The new one might sound better at the low end of its scale (or it might sound worse...who knows).

Good luck!

Chip

[daz]

Interesting thoughts, thanks. I'll certainly try them and i'll let you know how it works. I think the VD idea is likely to help especially. If i did that i would just make it switchable.

[PRNDL]

When the volume knob is really near zero, is the effective cutoff frequency of this cap affected?

The cutoff frequency is 1/RC with the R coming from the pot (there's a 2pi in there).

Another issue is the DC current into the grid, which is not a concern in this amp, but is in others.

Another idea would be to add a post PI master volume (dual pot), which will allow you to set the preamp gain for the amount of distortion, and the PPI for volume.

If you're really into mods, you could wire one of the preamp halves as a cathode follower with another volume pot. That would solve the impedance issues.

At low volumes, you'd have preamp distortion, but it doesn't take much to push the power tubes in a 6V6 amp.