For the millionth time...

[Govmnt_Lacky]

I am looking to build a simple CLEAN volume boost.

I DO NOT want it to go into OD or break up when it is in my chain ALONE.

I merely want it to "amplify" the signal that it is provided. If I want to do a clean lead, I just want it to be louder than the rythym. If I want to do a dirty lead, I just want it to be a LOUDER dirty lead.

I have looked over the search function and the forum in general and it seems like all of the "boost" pedals either sputter, break-up, or go into OD territory.

Any ideas? 

[R.G.]

There aren't any of those, for good reason. Well, OK, there are, but you won't like it

If you just want what you have, but louder, then you have to get a bigger amplifier and more/bigger speakers. What goes into an amplifier can only get louder to some point, then the amp can't make it any louder, and the amp clips. This can happen several ways; you can clip the output section, the phase inverter, or one of the preamp stages. But at some point, something clips. The only way to get just "more" is to get a bigger horse. Er, amplifier.  If the amp can't do it, no pedal in front of it will make it do it.

So you have to verify that the amp will cleanly do whatever loudness you want it to, then put whatever sound you want into the input. Note that the signal going into the input can only be big enough to make the input clip. For a 12AX7, the input clip range is from about 0V to 1.2V max. If the signal is bigger than that a the 12AX7's grid, the tube clips regardless of what you do to it afterwards.

This is a lot of the reasoning that went into the Workhorse amplifiers. They were designed to play clean, just at the barest edge of beginning distortion, when the volume knob was full up. They were NOT designed for amp distortion. Instead, they were designed to let you hear what you put in from your pedalboard.

If you are looking for a clean boost, irrespective of the above, use an opamp with +/-15V to +/-18V power supplies and set the gain to whatever you need. Any reasonably good opamp will be clean, squeaky clean, right up til it bangs into its power supply. There is no real trick there. It's just that I don't know of any guitar amp that can take a +/-14V signal into its input and not distort whatever is coming in.

[Govmnt_Lacky]

Thanks for that explanation. I get what you are saying. It looks like I will need to find a happy medium between Volume increase and signal clipping.

I have been looking at SHOs, LPBs, and the AMZ booster. Can anyone testify as to which of these will be the "most clean before clipping?"

[tubelectron]

Hi,

I would use an OPA134 op amp with a 2x9VDC symmetrical PSU... I use it for audio measurements and spectrum analyser ; it provides low distortion and suitable headroom.
But it also depends on the signal level you deal with, and the gain you want to draw from your pure clean booster.

Fortunately, while writing, R.G. came to help more likely than me...

A+!

[CynicalMan]

I have been looking at SHOs, LPBs, and the AMZ booster. Can anyone testify as to which of these will be the "most clean before clipping?"

http://www.generalguitargadgets.com/pdf/ggg_mamp_sc.pdf

The SHO and the AMZ booster will both be clean. The issue with them and the Micro amp is that they have very high input impedances. This increases noise, but it also provides less treble rolloff than we're accustomed to. For a completely "transparent" boost, make one of them with a 470k or 1M input impedance, like most tube amps. IMO the micro amp with the bias resistor lowered to 1M is your best bet.

[Gurner]

I see little point of a running boost circuit @ +/- 15V PSU ....if it's then feeding into an amplifier, with a preamp stage base on 12V single rail, so it's probablly worth asking - what amplifier is this elusive boost circuit going to ultimately be feeding into?

[Mark Hammer]

Although I have to say, in fairness, that most amplifiers are designed with a certain amount of clean headroom.  Not gobs of it, but some.  So a player should be able to add a gain factor of, say 3-4 and, unless they"re packing overwound humbuckers and doing Pete Townshend windmills, still be as clean as the amp allows.  That's why people can play compressors and still get a clean sound, even though compressors boost overall average output level; the compressors don't push the amp that hard.  Once you start getting into boosts of 20x, though, "clean" is going to be much harder to maintain unless the amp has lots of wattage, and more headroom than most.

Though while I'm on the topic, one of the nice things about compressors is that they CAN be used for clean boost.  If you set them for moderate to light compression, you can add some boost to the output level, yet not push the amp into clipping, because the compression keeps the peaks under control.  That was, when you think of it, one of the traditional uses for a compressor/limiter: preventing "peak excursions" from extending too high and distorting broadcast amps.

[caspercody]

The SHO is a clean boost, and it does have a boost to it. Also, the Klon is a very clean boost to it (with the gain all the way off). Plus it has tone control with the boost.

[Puguglybonehead]

I used to run a Bi-FET PreAmp pedal. (made by DOD or Boss, can't remember which) It provided a very decent clean boost. Something FET based, along those lines, will probably work well. I currently use an LPB1, which, while not exactly sparkly clean, is much less fuzzy than the FuzzFace clone I used as a "solo-boost", before that. (also much easier to build) Of course, I'm playing through a Supro 1600, so nothing stays very clean these days.

[Govmnt_Lacky]

Thank you all for the great responses.

I think I am going to go with Alex's suggestions and throw the SHO circuit on the breadboard (low part count is also a considerable factor) and fiddle with the resistor values to try different impedances.

Now, I may need to post up a For Trade offer for the 5KC pot. It always seems that I am missing ONE piece of the puzzle  

Dont you hate it when you are 1 component short for a build?!!   

[Kearns892]

I think I have the 5KC pot... Maybe we could work up a trade but since you're on the other side of the pond it may not be worth the trouble to pay for shipping

[Earthscum]

Quick question while this thread is fresh...

Has anyone built the Micro Amp using different chips? My current project involves an active A/B input pre with mute for my buddy so that he can use both his EB and his upright. I'll be running Jfet gain into a 3band tonestack into a final gain. I have been planning on using a dual chip  set up, pretty much like the MA (one for each channel), plus another dual for the DI out (probably just run an 072 there).

Anyways, I'm wondering about the noise, or if there is even much of a difference between an 072 and a 5532 in this circuit. Secondary concern is power (want it to run on 9V... for as long as possible). opinions? (facts?)

[Gurner]

Although I have to say, in fairness, that most amplifiers are designed with a certain amount of clean headroom.

Now there's one phrase I'd like to banish....in my books, headroom is headroom ....ie the bit left over in reserve before you start whacking your signal into the rail - I see "clean" preface it all the time...maybe I just need to be enlightened....can someone explain dirty headroom, lol

Once you start getting into boosts of 20x, though, "clean" is going to be much harder to maintain unless the amp has lots of wattage, and more headroom than most.

Agreed, if someone is after a boost of 20x & still keep his sound clean ...they should really be focusing their attention on the latter part of the 'guitar to ear' signal chain - ie the power amp, which is going to be the limiting factor wrt getting clean at high volume levels..

[Govmnt_Lacky]

I think I have the 5KC pot... Maybe we could work up a trade but since you're on the other side of the pond it may not be worth the trouble to pay for shipping

I appreciate the offer Jordan but sadly, you are probably correct. It would most likely be cheaper for me to order the part by itself and pay shipping!  

Anyone in the US interested? I suppose I should put something up in the FS section  

[harmonic]

'course, the other option might be to just attenuate a bit. So that switching it off means the full signal goes through. Gives you what you're looking for, with a VERY low parts count! ;-)

[Mark Hammer]

Although I have to say, in fairness, that most amplifiers are designed with a certain amount of clean headroom.

Now there's one phrase I'd like to banish....in my books, headroom is headroom ....ie the bit left over in reserve before you start whacking your signal into the rail - I see "clean" preface it all the time...maybe I just need to be enlightened....can someone explain dirty headroom, lol

No, you're right. , and it was stupid of me to imply that there was some other form of headroom by using the "clean" descriptor.  Headroom IS headroom.  

[Mark Hammer]

I think I have the 5KC pot... Maybe we could work up a trade but since you're on the other side of the pond it may not be worth the trouble to pay for shipping

I appreciate the offer Jordan but sadly, you are probably correct. It would most likely be cheaper for me to order the part by itself and pay shipping!  

Anyone in the US interested? I suppose I should put something up in the FS section  

Just use a 10k linear and a tapering resistor, or wire up a 10log backwards.

[boogietone]

Have not read many of the replies so this may be repetitive. I like the LPB 2tube or the LPB1 for this. You will want it as the last pedal in your effects loop. As long as the boost won't overload your power amp it will do what you want. The 2ube does use those pesky big clear melted silicon things instead of the small black ones but I actually prefer it. It has to be cranked all the way on both channels in series to get into OD territory.

[Govmnt_Lacky]

Just use a 10k linear and a tapering resistor, or wire up a 10log backwards.

I would Mark BUT, this is not for me. Building it for a friend who just did a complete pro setup on my baby!

[Hides-His-Eyes]

If you want a clean boost use an attenuator and wire the LED backwards. Clean clean clean!