CreativeAudioLabs Redeemer Circuit. WOW!!!

[SGD Lutherie]

In a while I'll be giving David's clips a critical listen.... can't right now. It strikes me that one of the reasons why people are skeptical about the Redeemer is due to the way it has been marketed, shrouding the device in mystery. Why not say it is a proprietary circuit like the Villex equalization circuit? Surely the Redeemer doesn't violate the laws of physics and works according to well understood principles.....

Thank you. That's my only objection with the device. They also claim it's patent pending, and as far as I can tell, that doesn't seem to be true either.

Even with Villex... he doesn't say he's doing something impossible... and he's clearly using transformer based circuits, such as what he designed for Lace with the Transsensor and Alumitone pickups.

 

[SGD Lutherie]

It's not an FET and it's not an Op-amp and passes signal without battery...

WATCH OUT! IT'S KRYP-TO-NITE!!!

he he he.

Patent Pending = "We haven't gotten around to applying for one, yet."

It's already encapsulated in the mu metal box... what are they worried about? Actually filling a patent would show the world what's going on in there.

As for David's Test...my ears must be shot...I can't tell the difference between A,B, OR C

That was kind of the point. They do sound a bit different, but nothing earth shattering. Use high quality headphones. You will hear a difference.

I prefer one over the other two, but I'll say which one that is after I reveal the answers.

 

[PilbaraBass]

I still say it sounds like it may be an FET buffer...

I've done some experimenting a while back with FET buffers and I can get it to pass signal without battery power...it seems that in certain configs I've experimented with my input byassing resistors will pass signal via the +Ve, albeit it is still high impedence.

(everything I've messed with thus far electronically says "FET" or at least "first stage FET" )

Look...I'm not doubting that Redeemer is very good at what it does...In fact, I've checked out the youtube vid, and I can tell that there are no smoke and mirrors there...

If I were a builder like Pete Skjold, I'd probably be on the redeemer bandwagon, too. Because it's exactly the product that suits Pete's vision of electronics. (Compact, simple, doesn't complicate anything...makes instruments sound better and when in business..a reliable, supported supplier)

Pete's an upright guy and willing to put his time and money where his mouth is (or this case, keyboard). Thanks, Pete...I respect that...


Finally for a new instrument or a mid-priced instrument it's a great addition. Price is a bit steep, but not outrageous.

For a budget hack like myself, I still go DIY when I can...

I'm having a bit of fun with my skepticism...but mostly, I'm CURIOUS! WHAT YA GOT IN THERE????

 

[awelti]

Hi Pete, (I'm posting this against my better judgment)
Thanks for all that you posted here about the Redeemer. I think the one "claim" everyone takes issue with is the one about sustain. Maybe we just ought to delete that one... We didn't even think of it ourselves in the first place, it was the beta testers - all pro guys and some session cats here in Nashville - who reported that they "felt" a difference in the responsiveness and that we should tell people about it. I have mine on in/out switches, and the guitar definitely seems to get a little quicker. I might be wrong about the counter EMF - but my reasoning is that the pick-up coil produces a signal voltage and the outside load draws a small current which has to flow through the pick-up coil and generate a small counter magnetic field which resists the changing signal, perfectly legal physics... So, get rid of the load, get rid of the current, get rid of the counter EMF, and get rid of the resistance to your playing. Yeah, I know if it exists at all it must be absolutely miniscule - but a lot of people say they can feel a difference... Back in the day, I didn't believe you could hear the difference in two different cables until someone sat me down and made me listen. This is the same sort of thing - you have to put it in a guitar on a switch and feel it for yourself - maybe sustain was the wrong word to use.

True - any good buffer would do the same thing in terms of unloading. I have an obsession about noise and distortion, and I was conditioned in my studio days to hate the sound of FETs so I just can't see myself going there - if I ever do, it would have to involve having an epiphany of some sort. I think the rest of the story with the circuit is minimizing self noise and distortion. Can I say that the published specs that everyone scoffs at are actually conservative? The input impedance is really about 20M and I can push it to 80M if I tweak the circuit on the bench. The distortion is never higher than spec'd and most of them come out less than half that. The noise floor is easily better than -120dBu on a routine basis from batch to batch - this is according to the Audio Precision System One.

Yes there are active devices in there, but they are "around" the signal path - supporting the signal path - just not "in" the signal path in a strict sense. That's why it still passes signal without power. Just be clear that removing power is not the intended way to "bypass" because without power it has somewhat higher output impedance than a passive pick-up by itself. The idea is that if your battery goes dead, it's not going to be a show stopper; you can get through the set list. BTW, removing the battery doesn't work on very early Redeemers...

It is patent pending - you can't claim "Patent Pending" until after you file. If some guy in China wanted to cob the circuit there's no way we could ever afford to fight it, even with a patent - Personally, after going through the patent process, I think it's a crock and in hind-sight maybe we shouldn't have done it, but I hope it turns out to be for the best in the end.

Comments about price are well noted - add to the price of parts, the cost of marketing, the cost of labor, the labor taxes, utilities, insurance, going to trade shows, etc... That's not even half the list. We're not getting rich! I heard what my neighbor's son was making stocking the shelves at Wal-Mart and I caught myself thinking twice about it! That's not to say "poor me" I love doing this stuff and I would rather go broke doing this than anything else. That said, we are always working at getting the price down, but they are hand made in Hermitage TN. I don't think I could stomach the idea of buying them from a robot, or from China... I'd rather not go that route, but we may be forced to in the end.

Thanks for your indulgence - I'm not a big "forum" type guy, but I'll try to check back in a few days...

Skip

 

[bongomania]

Hey, we're just glad to get some info straight from the horse's mouth. Still plenty to be curious about, but some info is better than no info, so thanks!

 

[12bass]

My guesses on the Redeemer sound samples:

A: EMG BTC
B: FET Buffer
C: Redeemer

FWIW, sample A reminds me the the BTC in my Hamer Chaparral 12. I hear a boost in the highs, but a bit of an unnatural character to the sound, with a bit of a notch in the upper midrange. Sample B sounds a bit dampened and lifeless, like the highs have been run through a capacitor. Sample C is a little louder which confounds the test a little, but it sounds clearer, more open than the others.

 

[awelti]

BTW - Why does the Redeemer help Active Pick-up's? All the active pick-ups I've looked at still have about 2K output impedance so that they can be blended without fighting each other. The Redeemer goes at the very output of the guitar/bass – after the blending, so it still drives the cable better. It is less obvious than the affect it has on passives, but it still helps – it is especially helpful for actives and passives if you are using the Redeemer instead of a direct box to plug straight into a lower impedance line input of a mixer.

Thanks, I’m off to look for lower priced (but not cheapo) parts ;-)

Skip

 

[SGD Lutherie]

I think the one "claim" everyone takes issue with is the one about sustain...I might be wrong about the counter EMF - but my reasoning is that the pick-up coil produces a signal voltage and the outside load draws a small current which has to flow through the pick-up coil and generate a small counter magnetic field which resists the changing signal, perfectly legal physics...

OK, I see what you were thinking. The thing about pickups is current will not flow without a load! That's true of any electrical circuit, of course. The current does produce counter EMF, as does any metal parts in the pickup, such as pole pieces or covers. Eddy currents form on the metal parts which produce their own magnetic fields which oppose the magnet in the pickup. This leads to loss of high frequencies, and a slightly inefficient pickup. This is the reason transformers have laminated cores.

But these fields are swamped by the permanent magnet in the pickup, which is far more capable of effecting the sustain of the string.

The effect of varying loads on the passive pickup is to lower the resonant peak which occurs right before the frequency starts to roll off. The greater the load, the lower the peak, and the "warmer" (or darker) the tone of the pickup. Then of course there is the cable's capacitance, which also has a dulling effect.

Some people like the tone of loaded down pickups, and therefore don't like the tone of buffers.. but it really is the real sound of the pickups. Having a lower input impedance on the buffer will achieve that, and also reduce noise, at the expense of high frequency reproduction.

Since we hear high frequencies better, a brighter pickups seems louder and quicker.

I'm a big fan of buffers myself. I also think your device sounded very good. The reason people use FET's is the high input impedance. Bipolar devices generally have a much lower input Z, around 200K. FET's are known for their tube like distortion, but you should never get to that point with a buffer! Low output impedance is important for driving cables and other devices, but it's the high input impedance that gives you that buffered tone.

You want a very low output impedance though, and any active bass can be plugged into the line inputs on a mixer without the need of a DI box. I do that all the time.

As far as the patent application... I couldn't find one, and I looked through a couple of hundred listed applications.

 

[12bass]

The idea of buffered pickups appeals to me. However, I've found the sound of a lot of onboard electronics lacking. In my experience, most of the better sounding parts take more current than is practical for battery powered operation. So that leaves me preferring passive basses and better quality parts in the outboard gear for recording. For live use I still use a Bartolini NTBT and an EMG BTC with an LT1352.

 

[SGD Lutherie]

My guesses on the Redeemer sound samples:

A: EMG BTC
B: FET Buffer
C: Redeemer

FWIW, sample A reminds me the the BTC in my Hamer Chaparral 12. I hear a boost in the highs, but a bit of an unnatural character to the sound, with a bit of a notch in the upper midrange. Sample B sounds a bit dampened and lifeless, like the highs have been run through a capacitor. Sample C is a little louder which confounds the test a little, but it sounds clearer, more open than the others.

Good ears! A is indeed the EMG BTC, and I agree totally with your assertions. Eutgard also guessed A correctly. I think the issue is the tone stack never really goes flat. It's close... closer than I expected it would be, but there's still an upper mid notch, and I think the lows are attenuated a bit. I don't think it's an issue so much with the IC they used as much as the tone stack, and maybe the tolerance of the pots.

I'm actually using that in by bass at the moment so I could test the pickups with a preamp, and I had a few laying around. With the highs and lows boosted it's not as bad.

This is making me think onboard preamps need to be able to bypass the tone controls, while still buffering the signal.

That leaves us with B and C. C was indeed louder, so I changed the level to match B, and I present it again:

Link Removed

Link Removed

Now they are the same average level, but C clearly has deeper lows, which makes it seem louder, while B seems to have almost EQ'd highs.

Ah.. the suspense!

 

[awelti]

OK, I see what you were thinking. The thing about pickups is current will not flow without a load! That's true of any electrical circuit, of course. The current does produce counter EMF... .

That was kinda my point... by making the load as tiny as possible current won't flow (as much) on the input side and would reduce that part of the counter EMF. It's not as noticible on a bass, but on a fast electric guitar, a lot of end users told us they thought they "felt" a difference, they planted the seed in our mind to tell people about it, we didn't plant the seed in their minds (the beta-testing happened before we put it on the website) - so what are people feeling? The counter EMF might be imeasurably small, but over the years I've learned that humans can be hyper-preceptive to phenomenon that I would normally rule out as being significant enough to make a difference... The difference between two cables is pretty well understood and accepted now, but that wasn't always the case. People claim they can hear the diffence between carbon resistors and metal oxide, people claim they can hear the difference between a mica cap and a ceramic cap, and these are fairly well accepted - something is going on with the Redeemer that people say they can feel, maybe it's the super high impedance (around 20M these days)

Some people like the tone of loaded down pickups, and therefore don't like the tone of buffers.. but it really is the real sound of the pickups. Having a lower input impedance on the buffer will achieve that.

I actually made a batch with a variable input impedance (from 10K to over 10M, like the input circuit I made for the MW1) and we sent it out to a bunch of beta testers. Pete got a few… The idea was to use it in place of the tone knob, it worked, but the consensus came back that it was going to be too much of a learning curve to have any broad appeal, so it’s on the shelf for now…

As far as the patent application... I couldn't find one, and I looked through a couple of hundred listed applications.

Well, only couple million left to go ;-) I assure you I invested a month of my time to file, and I have the letter of receipt so I know I wasn't imagining it...

I'm just trying to push the limits of making audio as clean as possible - here's a good analogy I heard from Sarge, which I will clean-up a little.

"If you wanted to make a cup of coffee, would you want to start with pure clean water from the mountain spring, or would you want to use water that came through a sewer pipe? sure, in the end, if you make it black enough and add some cream and sugar your guest might not know the diffence"

You can add FX, overdrive and noise in a controlled way if you want to, but that doesn't mean it's OK to start with a dirty buffer - if I can find a way to make it even better, I will even if it doesn't make a diffence to the audience - just because it's my obession - I would love to get to absolute zero on the spec's.


Skip

 

[12bass]

Hmmmmmm..... I'm staying with my original choices. C still sounds a bit louder to my ears. It has a bit more "life" to it than B. B sounds a bit compressed.

And as for the BTC, the LT1352 definitely helped open it up. The LF442 is not a very hi-fi chip IMO... sort of "papery" sounding.

 

[SGD Lutherie]

That was kinda my point... but over the years I've learned that humans can be hyper-preceptive to phenomenon that I would normally rule out as being significant enough to make a difference...

Yeah, I agree here. I learned a long time ago that I could hear the different in a pickups polarity, but I wouldn't even be able to put it into words, and in the big picture was so subtle that it was meaningless.

I think with caps it's all about where and how they are used.

I actually made a batch with a variable input impedance (from 10K to over 10M, like the input circuit I made for the MW1) and we sent it out to a bunch of beta testers. Pete got a few… The idea was to use it in place of the tone knob, it worked, but the consensus came back that it was going to be too much of a learning curve to have any broad appeal, so it’s on the shelf for now…

I'm sure you a re familiar with the Audere bass preamp? Same concept.

I'm just trying to push the limits of making audio as clean as possible

Nothing wrong with that.

 

[SGD Lutherie]

Hmmmmmm..... I'm staying with my original choices. C still sounds a bit louder to my ears. It has a bit more "life" to it than B. B sounds a bit compressed.

And as for the BTC, the LT1352 definitely helped open it up. The LF442 is not a very hi-fi chip IMO... sort of "papery" sounding.

I've been wanting to stick a LT1352 in there, but I'll be replacing the thing soon enough.... It is a bit cardboardy. Reminds me of an Ampeg tone stack set flat. :scowl:

OK... might as well spill the beans.

B is the Redeemer, and C is the FET preamp.

When I first hooked up the Redeemer my reaction was "hey, this sounds really nice!" And it does. You certainly don't want to go back to passive after using it. So I was really curious about the comparison to the FET buffers I have been using for a while.

The FET was a bit on the hot side, even with the gain all the way down, but this was because it was meant for a low output pickup. It's also DC coupled to the pickups, with the DC/AC conversion at the output. This gives it unlimited low frequency response, down to DC current. The clipping you hear is at the mixer, and not in the buffer. I could have padded the input on the mixer, but I was trying to leave everything set the same.

After playing the two awhile, the Redeemer sounded as if the low end was a tad attenuated, and I could really hear a difference when going from the low B string to the E. The B got a little thinner sounding.

The low end was similar to the BTC, so it wasn't until I tried the FET that I heard the difference. You can especialy hear it on the neck pickup, which sounds warmer to me though the FET. They are both hi-fi, but the Redeemer is a bit cooler sounding. Would really help out a muddy sounding bass.

I liked the Redeemer when I had both pickups on, it seemed to have a boost in the highs. The loading on the Redeemer seems to be higher, as you can hear the resonant peak on the pickups is lower, more in the upper mids, which is good spot if you want a ringing treble tone.

To my ears the FET sounds fuller in the mids and upper bass, and the resonant peak induced on the pickups is higher. The low B really stands out and you can hear its fundamental vibrations better. This FET buffer has no input impedance setting resistor, so it's pretty damn high. JFETs have input impedances of about a billion ohms.

I've been using this circuit since the mid 80's on both basses and guitars.

Bottom line is they are both very similar sounding, each having their own personality.

Alex, thanks for coming here and clearing up some of the stuff that was bothering me. It removes the snake oil from the equation and lets the quality of the product shine though.

 

[SGD Lutherie]

Well, only couple million left to go ;-) I assure you I invested a month of my time to file, and I have the letter of receipt so I know I wasn't imagining it...

Well that was search results.

OK I found your application just now. Very interesting circuit configuration. You have more going on in that little box than I imagined!

 

[alexclaber]

Regarding the effect of pickup loading upon string response:

[Invalid or Expired Link Removed]

And regarding the output impedance of active pickups, the output impedance of EMGs is pretty high. Using my EMG+OBP-3 bass to drive a QSC PLX the bass sounded perfectly normal (though quiet due to the low sensitivity of the QSC) with the OBP-3 switched on. Once I took the OBP-3 out of circuit so the EMGs had to drive the powe amp directly the tone and output changed drastically and not for the better.

It's quite a challenge to write blurb on something as technically complicated as a pickup buffering preamp, especially as there isn't really such a thing as the 'true sound' of the pickup - the sound is always dependent on what it's driving.

I have a mic preamp that takes an even more counterintuitive approach, using a very low impedance input and then sensing the current rather than the voltage. Am still baffled as to what's going on but it works great!

Alex

 

[SGD Lutherie]

Regarding the effect of pickup loading upon string response:

[Invalid or Expired Link Removed]

I saw that previously, and even dropped Dave an email about that. It's just not correct IMO. A high impedance load will draw more current from the pickups, and that might affect sustain, as you are loosing energy from the pickup faster, but a regular passive pickups just wont work in reverse. You need something like the Moog guitar to stop a string from vibrating.

The other thing is impedance is frequency related, so the AC resistance goes up with the frequency. A large load on a pickup will kill the high frequencies, while leaving much of the low frequencies.

And regarding the output impedance of active pickups, the output impedance of EMGs is pretty high.

That's true. EMG's have an output impedance of about 10K. The BTC has an output impedance of 2K.

It's quite a challenge to write blurb on something as technically complicated as a pickup buffering preamp, especially as there isn't really such a thing as the 'true sound' of the pickup - the sound is always dependent on what it's driving.

Also true. However, the loading can take the form of reduced frequency response and output. So if you want to design a pickup with a wide response, you are going to loose some of that if you don't buffer the pickup. So, right, it is not the tone of the pickup though a typical passive signal path, but it is the tone of the pickup isolated from all that stuff.

I designed my latest pickups to sound good passive, but I think they sound better buffered, and truer to my intention. It's all a matter of degree, and passive systems are often a compromise.

Rick Turner has said all electric basses are active, it's just a matter of where your first gain stage is.

Audere has a very elegant solution to making active sound passive, if that's what you want. I was working on a similar preamp 3 years ago, and then I decided to go in a different direction. I got my inspiration from variable Z mic preamps. I think Dave nailed it on the head though. Seems like a nicely designed preamp on a whole.

 

[PilbaraBass]

David,

On your recordings, I actually prefered "A" sonically...I must have liked the mid hump (or maybe it was the playing )...

C definitely had more lows...but it was difficult to compare to A and B because the music line was different (different high and low root notes...uh ohhh! )

Question:
Have you experienced with certain FET circuit designs that you can bleed the signal sufficiently through input biasing resistors such that it can actually play "ok" without a battery connection?

I have had this experience with a couple of breadboard designs that I was messing with.

Kerry


And thanks so much, Skip, for joining the thread...I am truly curious about your circuit...

I SAY....I SAYYYY...WHAT YOU GOT IN THERE, BOY???

 

[seanm]

Question:
Have you experienced with certain FET circuit designs that you can bleed the signal sufficiently through input biasing resistors such that it can actually play "ok" without a battery connection?

I have had this experience with a couple of breadboard designs that I was messing with.

I have designed one fet circuits that could run for long periods of time (10s of minutes IIRC) just off the power stored in a medium sized cap (100uF, again IIRC).

If you have a filter cap (and you should), try removing it and see if the fet dies.

 

[eutgard]

Great thread!

I think any kind of impedance buffer should have bypass switch.

Because there is time when mellow/sweet passive tone is desirable.

I thank awelti for great product and SGD Lutherie for clips!