Blues Harp Hi-Impedance Mic Effects Pedal Mods

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Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby blues u can use » Tue Nov 04, 2008 1:52 pm

Hi all,

From time to time I've used a Danelectro BLT Slap Echo effects pedal (when an amp with spring reverb is not available, or when I'm using a vintage Silvertone or similar tube amp with great tone but no reverb), with the pedal's knobs set to just a teeny bit of delay, not excessive to where it sounds cheesy, but just a tiny touch to add some fullness to the sound. It's worked pretty well, and I've ramped it up a tiny bit when doing lead, and brought it back down when comping, particularly behind a vocal soloist, as I want to support, not compete or detract from her singing.

It's been not a bad arrangement, but am wondering about a specific point to do with impedance, and the possibility of improving the matchup even more, to avoid any needless decrease in low-end tone through mismatched impedances.

I realize that a high-impedance mic MUST be connected to something which 'expects' a high-impedance instrument. A guitar combo amp would be the most often used example we usually connect a hi-Z mic to, but our simple audio signal path becomes a little subtly more complex when we start adding in effects pedals enroute to our amp.

I had thought that the high-impedance mic (a homemade unit using a vintage Shure Controlled Reluctance capsule) I'm using would be OK connected to the input of the BLT effects pedal, and again, it seems like a decent solution, so far.

But, as always, with most of us who play amplified blues harp, I continually listen and when I find areas to improve (whether in playing technique or my rig) keep fine-tuning things. I compare different ways of running my signal through the various setups I end up playing through, so use that as an opportunity to listen and observe what works better or not.

Since I play different places with different setups, some of which don't allow me to use my own amp, or even mic, just the house setup (which is tough, but teaches flexibility, I guess one could say is the upside of that), it's only natural to hear differences, and hopefully learn what will help improve my sound.

Some of the differences are room acoustics from one place to another, and I realize a big part of tone is playing technique, breath, embouchure, cupping, etc.

Back to what I had the question about, though: Had thought the BLT slap echo, or any similar inline guitar effects pedal, would be fine enough for a high-impedance mic, because both guitars and hi-Z mics can plug into the same guitar amp 1/4" unbalanced input jack, neither are low-Z XLR balanced or line-level signals, both simply what I thought are much the same instrument level signal.

However, I've read something about the impedance of guitar pickups being different from these vintage high-impedance mics that blues harp players like, so the effects pedals, which are basically designed for guitar players, might not be matched properly to our mics, and therefore, as some have phrased it, "suck the tone" right out of our sound, due to that impedance mismatch.

I realize that those who try to plug a hi-Z mic's 1/4" connector through a simple, NON-transformer, 1/4-to-XLR adapter, into a balanced, low-Z P.A. mic input or similar, will lose both amplitude as well as a fair amount of the low end to their signal. That's basic stuff, getting the right impedance and levels matching for instrument level, hi-Z, vs XLR balanced mic lines. I thought that very basic, large distinction was enough, and all I really need to have figured out and set up correctly.

If you look at some of the online talk about impedance mismatch, and pedal mods to fix the too-low input impedance of typical guitar pedals in order to better match hi-Z mics, or check out the info on some of the newer blues harp mic-specific pedals (one example would be, for instance, the Lone Wolf harmonica inline effects pedals), there are folks talking about regular guitar pedals not being the best thing to use for a harp mic.

I wonder, if this is true, about modifying (or getting modified by someone else) my little Danelectro BLT Slap Echo guitar pedal, so it better matches the Z of my mics. I'm not able to afford a ton of pricey solutions, and great as some of them might be, some of them are just a bit out of my budget right now, including things like Harp Commander, Lone Wolf products, etc. I'd love to have 'em all, but can only afford what I can do at this moment. Just like I'd love a Victoria amp, or a Sonny Jr, or an original '58 Bassman. Or some of the top-notch harp reed techs who customize things for you for $150 on up, in addition to the original cost of the harp you send them. I know these things are all definitely well worth the money, but for now, I have to use my own jeweler's files and do it myself, find vintage cheap Sears amps, and fix them up myself, and truth be told, I love the process of doing these things.

What this discussion of money issues leads to is, I wonder if there is an affordable way to modify my existing BLT Slap Echo pedal, rather than just yet save up and buy a special pedal custom-made for harp player mics?

Is there a mod I can do to change the impedance the pedal expects to "see" on its input? Or does someone do such pedal mods at an affordable enough price for me to send it out? The pedal itself was only about $25, and I realize I might have to pay at least that much in addition to get it fixed, set up correctly, and it's still a bargain $50 or so pedal, rather than a $150 to $200 harp-specific custom one (which again I'm NOT at all knocking, just can't quite afford right now).

Thanks for any info/assistance on this matter.

Colette
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby jeffl » Tue Nov 04, 2008 7:26 pm

Colette: I'm ignorant on the technical aspect of your post, but for what it's worth, I use the BLT you're talking about, into either one of my tube amps, and I haven't been dissatisfied with my tone; admittedly, I may not have the most discerning ear, but neither do the folks who are subjected to my music. If I were you, I'd only spend the money if you just can't be satisfied unless you're on the perpetual tone search. Much of the reason that musicians switch gear is 'cuz our ears get accustomed to the way we've been doing things and we want something different to wake them up. The result may not be better-- just different. If you think the Harp Commander may be the ticket (I have a Commander I), you might contact Brian Purdy at http://www.harpgear.com and see if he knows anybody who's purchased a Commander II or III and wants to dump their HC One for a song. I bought my Commander, pre-used, through him. I bought mine before the II and III came out, and paid more than I'd guess you'd want to, but I'd guess that the original ones aren't worth much at all right now.
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby t bone bruce » Sat Nov 08, 2008 9:00 am

Hi Colette,
Although guitar pickups and vintage mics are both "high impedance", there's a significant diference in the impedances of a mic and a pickup. Crystals are very high, 5Meg +. The other problem with most guitar effects is that the output voltage of a guitar is much less than a harp mic. I tested the output of a hot 1963 CM on my votlage meter and o'scope, and when cupped and playing hard, peak voltages of 2V were possible. Obviously during normal play the output is lower than that, but 1V output is reasonable. Conversely when I plugged a Strat into the same setup, the output voltage was 250mV while playing the guitar as hard as I could. Peak output for the harp mic was 8 times greater!

Money is always an issue! I have saved up and bought the Lone Wolf Delay, Tone+ and the new octave pedal is on the way. They are well worth it. If you had to get just one, I'd get the Tone+ and put it in front of your BLT. That way you'd have impedance matching from the Tone+, and the ability to fatten up the harp sound going into the delay.
There is a cheaper option if you are handy with a soldering iron, and that's the JAYPHAT. Stephen Schneider posted the schematic on harp-L a while back, but if it's not there still PM me because I have a copy, and have built 2. It's a buffer that provides a high impedance input for mics, can provide a little extra gain for weak mics or turn down realy hot ones, and you could get the parts for about $25. Should improve the impedance matching with a BLT. I have even used mine with a high impedance mic straight into a PA with pretty reasonable results.
Hope this helps.
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby bottleneck » Mon Nov 10, 2008 7:01 pm

to get the best tone and sounds,why not skip the effects?.then you don't have to worry about it.

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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby jeffl » Mon Nov 10, 2008 7:46 pm

bottleneck wrote:to get the best tone and sounds,why not skip the effects?.then you don't have to worry about it.
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I'll try again. The purist sentiment is always impossible to refute, since tone is a subjective matter, but when it comes to delay or reverb, there's no shame in using it; most guys jus' use a little, but I've heard very good harpers who use very deep reverb. I personally prefer a little delay.
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby bottleneck » Tue Nov 11, 2008 5:30 am

where as i do not use effects,not even reverb,i was only trying to be funny.as in haha,:) :)

no offense to guys who use effects as long as they're not after me,haha : ) :)

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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby bottleneck » Tue Nov 11, 2008 5:35 am

oh,and to answer the original posters question,you could use a transformer in the shell or in a seperate project box to match the output more closely to a guitar.however,i don't know if that would make the effect work any better.hope this helps.

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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby t bone bruce » Wed Nov 12, 2008 11:08 pm

You could use a transformer, but you have to make sure the ratio is right otherwise you can end up with too low an impedance. That's the advantage of using a buffer.
Delay (echo) is used in Little Walter's recordings, as well as many others: There's definitely no shame in using delay as an effect. To my mind it sounds better for harp than reverb. In the past the tape delays would have been tube devices, with appropriate input impedances for the mics of the day. So using an impedance matching set up to get the best of your mic and a modern delay is not "cheating"
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby ricochet » Thu Nov 13, 2008 3:01 am

As far as transformers go, the impedance ratio is the square of the turns (voltage) ratio. Problem is that the current from a high impedance mic is extremely low, and with many transformers that will get swallowed up magnetizing the core.
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby jeffl » Thu Nov 13, 2008 7:06 pm

So, the smaller the core, the less that gets swallowed...? Is that right...?
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Re: Blues Harp Hi-Impedance Mic Effects Pedal Mods

Postby ricochet » Thu Nov 13, 2008 10:40 pm

Pretty much.
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