Soundhole vs Piezo volume difference

[Oldskool Texas]

Saturday night I played out with a LR Baggs M1 soundhole pickup on one guitar, and an under-saddle piezo on the other. Both go through a Baggs Par-DI, then to the PA.

 

The piezo guitar was about twice as loud as the M1, meaning I had to perform a major volume tweak every time I changed guitars. Besides routing each guitar through a different PA channel, how can I minimize this difference? Anyone have experience with the Baggs M1? Are they notoriously quiet? Have you adjusted the pole pieces, and would that help?

 

BTW, the M1 sounds awesome - no quack, and a very rich sound.

[pipedwho]

If it's the M1 active, then you should just be able to turn up the volume - it does get pretty loud.

For the piezo equipped guitar, if it has an onboard volume control, you can just turn it down.

If you can't do either of the above, then it might be worth getting a stomp box like the Boss GE-7 EQ and stomp it as a level control. You could also get something like the Zoom A2 and use a different patch with a volume preset that makes the level and EQs similar for both guitars.

[sdelsolray]

Adjust the volume of the M-1 equiped guitar to playing level (gain staging appropriately between the PADI and PA board). When you plug in the other guitar with the hotter signal from the UST, turn the gain down, a bit at each gain stage.

That's simple, effective and doesn't cost anything.

[pipedwho]

Originally posted by sdelsolray Adjust the volume of the M-1 equiped guitar to playing level (gain staging appropriately between the PADI and PA board). When you plug in the other guitar with the hotter signal from the UST, turn the gain down, a bit at each gain stage. That's simple, effective and doesn't cost anything.

 

 

But, that sounds to me like it belongs to the category of 'major volume tweak'.

[sdelsolray]

Originally posted by pipedwho But, that sounds to me like it belongs to the category of 'major volume tweak'.

 

 

Yes it is. Because the two pickups put out different signal strengths, a volume adjustment is necessary if you want both guitars to have the same nominal volume. How that is done really isn't that important. My suggestion just used what was already available. No need to add another device to the signal chain.

[Oldskool Texas]

Sorry, I should have mentioned that neither guitar has any onboard controls. The under-saddle was installed aftermarket, and the M1 is passive. I like the EQ stompbox idea - good suggestion.

[pipedwho]

Originally posted by Oldskool Texas Sorry, I should have mentioned that neither guitar has any onboard controls. The under-saddle was installed aftermarket, and the M1 is passive. I like the EQ stompbox idea - good suggestion.

I have a number of effect patches (ie. different combinations of subtle chorus, compression, air, harmonizer, etc) that I use on my Zoom A2. I put all the patches in one bank that I use for one guitar, and in another bank I have a duplicate set of patches that are set up with slightly different EQ, level and 'guitar model'. This means I can bring either guitar with me, and all I have to do is use the appropriate bank - I don't need to tweak it each time I setup. (I don't use two guitars at the same time though.) The Zoom only cost me US$70, is very quiet and does a great job.

I used to use the Boss GE-7 to EQ the guitar and a Boss CH-1 Chorus for subtle effects, but the Zoom is quieter, more versatile and way more convenient.

[Terry Allan Hall]

Install an inline potentiometer (volume control)...Radio Shack sells a great one (100Mohm) for a couple of $$$.

[pipedwho]

Originally posted by Terry Allan Hall Install an inline potentiometer (volume control)...Radio Shack sells a great one (100Mohm) for a couple of $$$.

 

The problem with this, is that it either makes the piezo look like an even higher impedance load (which will cause the treble frequencies to be significantly rolled off), or it will put an excessive load on the piezo (which will cause the bass frequencies to be significantly rolled off).

 

It can be done, but it requires a couple of extra capacitors. The value of these caps is dependent on the amount of inline and load resistance. I've done this inside my guitar to stop the internal preamp from clipping, but it took quite a bit of effort to work out the effective impedances of the piezo and the preamp, and then to calculate the right component values. And I still don't think it sounds as good as going directly from the piezo straight into a good high-headroom preamp.

[Terry Allan Hall]

Originally posted by pipedwho The problem with this, is that it either makes the piezo look like an even higher impedance load (which will cause the treble frequencies to be significantly rolled off), or it will put an excessive load on the piezo (which will cause the bass frequencies to be significantly rolled off). It can be done, but it requires a couple of extra capacitors. The value of these caps is dependent on the amount of inline and load resistance. I've done this inside my guitar to stop the internal preamp from clipping, but it took quite a bit of effort to work out the effective impedances of the piezo and the preamp, and then to calculate the right component values. And I still don't think it sounds as good as going directly from the piezo straight into a good high-headroom preamp.

 

 

Actually, you're mistaken...it merely lowers the volume...I've done this to balance the volume of the P/U in my Taylor to match the volume of the P/U in my Guild.

 

It's just a simple 100Mohm potentiometer...possibly you used the wrong value (250Kohm or 500kohm) in your pot selection...the lower values do trim the highs, thus you might need to add capacitance...or it could just be that "Cool-Tube" preamp that's Takamine's latest pre-amp "swonder"...

 

Try this site for more useful electronic info: http://www.stewmac.com/cgi-bin/hazel.cgi?action=SERVE&sku=I-4000&PG=4&s1=Free_info_sheets&item=freeinfo/fi.html

[Cldplytkmn]

am i the only one thats thinking volume pedal???

[Oldskool Texas]

Originally posted by Cldplytkmn am i the only one thats thinking volume pedal???

 

 

LOL.. yeah, that's something I considered as well. Boy, between the A/B box, the tuner, the Para DI and now a volume pedal or an EQ, I'm going to need a bigger pedal board. So much for the "simplicity" of playing acoustic!

[pipedwho]

Originally posted by Terry Allan Hall Actually, you're mistaken...it merely lowers the volume...I've done this to balance the volume of the P/U in my Taylor to match the volume of the P/U in my Guild. It's just a simple 100Mohm potentiometer...possibly you used the wrong value (250Kohm or 500kohm) in your pot selection...the lower values do trim the highs, thus you might need to add capacitance...or it could just be that "Cool-Tube" preamp that's Takamine's latest pre-amp "swonder"... Try this site for more useful electronic info: http://www.stewmac.com/cgi-bin/hazel.cgi?action=SERVE&sku=I-4000&PG=4&s1=Free_info_sheets&item=freeinfo/fi.html

Are you sure you found a 100Meg pot? I've never seen anything bigger than 20Meg and they are very hard to find.

Anyway, a lower value pot (like 250k or 500k) in series-parallel with the circuit will trim the lows and make the pickup sound tinny and thin. A higher value pot can theoretically work, as long as there is an extremely small capacitance (ie. femtofarrads) on the input of the preamp (assuming the pot is right at the input of the preamp).

This has nothing to do with the preamp per se, but you're right, the Takamine preamp has a 'class-a' j-fet input buffer with about 3pF of capacitance and 2.2MegOhms input impedance. To both reduce the level and smooth out the curve I needed a two pole network of R's and C's, with the R's on the order of 3Meg and 2Meg with caps of 8.2pF and 2.2pF. These values are tailored to my piezo/preamp, but the principle applies to other preamps also. After doing frequency sweeps into calibrated loads, I calculated an equivalent circuit, and then used a spice model to work out the above filter values to flatten the curve. It sounded much clearer than with only a 4.7Meg pot (which was my first attempt to reduce the level of the piezo. ). Through my guitar amp it didn't make much difference, but it was very obvious through a PA (without the correction caps, frequency roll off was about 3dB down at 10kHz, and 10dB down at 20kHz.)

I suppose I could've just gone with the 4.7Meg pot, and used an EQ to bring back the lost treble frequencies. But, I wanted to blend the piezos with a Baggs M1, and the Cooltube doesn't have individual EQs for each input.

BTW, there doesn't appear to be anything magic about the Cooltube, it's a just a dual source preamp. The 12AU7 tube is always in the circuit and has a gain control that dials in some tube warmth (ie. a little nice sounding harmonic distortion ). As far as preamps go, it's not bad, but more headroom on the first input stage wouldn't have gone astray.

[pipedwho]

Originally posted by Cldplytkmn am i the only one thats thinking volume pedal???

These are good, but you want to make sure you get one that has a settable minimum/maximum level. This is especially important if you can't hear what the audience is hearing from the stage. I used to use one for this sort of thing, but it is so much easier to just set up a few patches on my Zoom A2 for different types of songs (ie. soft picking, aggressive picking, loud strumming, solo, etc). Now I just use it occasionally on the effect level control of the Zoom A2 when I want to do volume fades or effect sweeps.

[Terry Allan Hall]

Originally posted by pipedwho Are you sure you found a 100Meg pot? I've never seen anything bigger than 20Meg and they are very hard to find. Sure did...not hard too find at most of the local electronic outlets. Anyway, a lower value pot (like 250k or 500k) in series-parallel with the circuit will trim the lows and make the pickup sound tinny and thin. A higher value pot can theoretically work, as long as there is an extremely small capacitance (ie. femtofarrads) on the input of the preamp (assuming the pot is right at the input of the preamp). Actually, I wired it in between the P/U and tyher output jack, as I don't use internal preamps...no good reason to. This has nothing to do with the preamp per se, but you're right, the Takamine preamp has a 'class-a' j-fet input buffer with about 3pF of capacitance and 2.2MegOhms input impedance. To both reduce the level and smooth out the curve I needed a two pole network of R's and C's, with the R's on the order of 3Meg and 2Meg with caps of 8.2pF and 2.2pF. These values are tailored to my piezo/preamp, but the principle applies to other preamps also. After doing frequency sweeps into calibrated loads, I calculated an equivalent circuit, and then used a spice model to work out the above filter values to flatten the curve. It sounded much clearer than with only a 4.7Meg pot (which was my first attempt to reduce the level of the piezo. ). Through my guitar amp it didn't make much difference, but it was very obvious through a PA (without the correction caps, frequency roll off was about 3dB down at 10kHz, and 10dB down at 20kHz.) I suppose I could've just gone with the 4.7Meg pot, and used an EQ to bring back the lost treble frequencies. But, I wanted to blend the piezos with a Baggs M1, and the Cooltube doesn't have individual EQs for each input. BTW, there doesn't appear to be anything magic about the Cooltube, it's a just a dual source preamp. The 12AU7 tube is always in the circuit and has a gain control that dials in some tube warmth (ie. a little nice sounding harmonic distortion ). As far as preamps go, it's not bad, but more headroom on the first input stage wouldn't have gone astray. A good clue as to how popular/useful a musical item really is is how long it's out before someone puts out a cheaper version...the Cool Tube is an excellent example of this maxim...how many "clones" have you seen of it, compared with solid state-only preamps?

[Terry Allan Hall]

Originally posted by Oldskool Texas LOL.. yeah, that's something I considered as well. Boy, between the A/B box, the tuner, the Para DI and now a volume pedal or an EQ, I'm going to need a bigger pedal board. So much for the "simplicity" of playing acoustic!

Try the inline volume control, 1st....much easier, less expensive and you don't have to drill any holes (unless you want to)...mine is just wired up, then I set the volume where I wanted it to be, and taped it in place, inside, so it wouldn't rattle around.

Simplicity is always good!

[pipedwho]

Originally posted by Terry Allan Hall A good clue as to how popular/useful a musical item really is is how long it's out before someone puts out a cheaper version...the Cool Tube is an excellent example of this maxim...how many "clones" have you seen of it, compared with solid state-only preamps?

I can see that you don't like the Cooltube, but let me say again that it is just a normal preamp, but with an extra 'effect' that just happens to use a vacuum tube. IMO the 'effect' enhances the sound in a nice way. I don't dial it all the way up, but I don't leave it at zero either.

The tube effect can be done in many ways - eg. the Tech21 and Behringer ADI21 do it with a solid state circuit. Other manufacturers use modellers. It is all the same thing, with slight differences in personality between manufacturers. Takamine chose to use a tube, probably mainly for mojo reasons, but that doesn't mean it doesn't actually work.

[Cldplytkmn]

just cause behringer hasn't ripped it off YET, doesn't mean its not an effective unit... I've only played one cooltube and it was in a noisy GC, so i can't judge its sound, but i don't see any fatal flaw in the concept. Running acoustics through tube preamps is hardly uncommon.

[DeepEnd]

Originally posted by pipedwho But, that sounds to me like it belongs to the category of 'major volume tweak'.

It's not. Psychoacoustically (i.e., the way we perceive sound), "twice as loud" means a difference of 10 decibels, which the volume control on the M1 should've been able to handle with ease if it were active.

[pipedwho]

Originally posted by DeepEnd It's not. Psychoacoustically (i.e., the way we perceive sound), "twice as loud" means a difference of 10 decibels, which the volume control on the M1 should've been able to handle with ease if it were active.

 

 

I was assuming 'major volume tweak' from the OP's start post meant effort required to tweak the volume, as opposed to the actual amount of volume being tweaked. By this definition, twiddling knobs on anything while you're trying to play a song would be considered major - eg. a PITA, especially if you can't properly hear the level going to the audience.

 

As per all the previous mentioned solutions, this is not an unsolvable problem. I used to play with a guy that used an A/B instrument selector box that had inbuilt volume settings for each of the two channels. I think it was a Radial something-or-other. He had his classical going into one input, and his steel string into the other. Seemed to work fine.

[sdelsolray]

Originally posted by pipedwho I was assuming 'major volume tweak' from the OP's start post meant effort required to tweak the volume, as opposed to the actual amount of volume being tweaked. By this definition, twiddling knobs on anything while you're trying to play a song would be considered major - eg. a PITA, especially if you can't properly hear the level going to the audience. As per all the previous mentioned solutions, this is not an unsolvable problem. I used to play with a guy that used an A/B instrument selector box that had inbuilt volume settings for each of the two channels. I think it was a Radial something-or-other. He had his classical going into one input, and his steel string into the other. Seemed to work fine.

 

 

The OP wasn't concerned about twiddling knobs during a song. He reported an amplitude difference between two different guitars, each with a different passive pickup. He would only need to adjust volume of a guitar when he changed instruments, which is between songs, not during one. I still think he can solve the problem by turning the knobs he already has. Adding another budget piece of gear into his signal chain could easily degrade the sound.

[Cldplytkmn]

Originally posted by sdelsolray The OP wasn't concerned about twiddling knobs during a song.

 

 

 

meaning I had to perform a major volume tweak every time I changed guitars

 

 

sounds like he doesn't want to be twiddling knobs between songs either... "deal with it" isn't exactly grand advice

 

[sdelsolray]

Originally posted by Cldplytkmn sounds like he doesn't want to be twiddling knobs between songs either... "deal with it" isn't exactly grand advice

 

 

Dunno if the OP does or does not want to turn a gain control a bit to equal out the relative volumes between his two guitars during a gig. How many times would you swap guitars during a couples of sets? 3 or 4 times? How painful having to reach over to the PADI and turn a knob. Why even bother playing if it takes that much effort and involves that much inconvenience?

[Terry Allan Hall]

Originally posted by sdelsolray Dunno if the OP does or does not want to turn a gain control a bit to equal out the relative volumes between his two guitars during a gig. How many times would you swap guitars during a couples of sets? 3 or 4 times? How painful having to reach over to the PADI and turn a knob. Why even bother playing if it takes that much effort and involves that much inconvenience?

 

 

Well, in my case, the PADI is on the floor and I just prefer to have all of my guitars be the same volume, so I don't have to mess with the PADI or PA channels volume control....thus, I wired the internal volume control, set it to where I wanted it to be and don't have to mess w/ it further.

 

And I don't have to worry about blasting the audience w/ feedback when I'd forget to turn down between instruments...it's easy to do!

[Cldplytkmn]

Originally posted by sdelsolray Dunno if the OP does or does not want to turn a gain control a bit to equal out the relative volumes between his two guitars during a gig. How many times would you swap guitars during a couples of sets? 3 or 4 times? How painful having to reach over to the PADI and turn a knob. Why even bother playing if it takes that much effort and involves that much inconvenience?

 

 

it doesn't matter I do... i just know its not a big deal to turn knobs if they're above waist level, but it sounds like he's using a floorboard, and bending over is really obnoxious for me. I also have no idea where he is in relation to his soundboard... might be close, might not... thats why i wouldn't assume its easy to just turn 'the knobs he already has'... TAHs solution is pretty slick... it'd be cool also to see an A/B box with a couple volume pots, dunno if that exists or not.