Anyone know the circuits in the Seymour Duncan and Dimarzio active pups?

[J M Fahey]

The Polish drawn preamp drawing above does not click right for me.
The left coil is loaded by 30K in series with a .022uF cap. Cutoff frequency: around 240 Hz.
The right one is loaded by two 178K resistors in paralell, in series with another .022uF ; cutoff frequency around 82 Hz.
There is no way said coils can cancel 50 or 60 Hz hum effectively, *and* higher frequency noise/interference too.
You *may* optimize turns ratio for one or the other job, not both at the same time.
jm2c

[Alan0354]

Sorry to have confused you. I'm using the term humbucker affectionately like a nickname. "Noisebucker" would be more apt. But we feel we have some significant benevits vs. the EMG circuit. Our noise level is improved by 12-14dB while also freeing up more headroom up top. So the noise at rest is 12dB quieter, but the increased headroom means that at some point when the EMG preamp clips, having a hard limiting effect on the signal, the Blackouts do not clip and therefore something could be said about the signal to noise ratio, but it's only apt once the EMG preamp clips. It clips the attack (call it peak?) of almost any moderately picked note, and clips what you could loosely refer to as "RMS" under medium-to-hard playing. Many players run the EMG's at 18 volts, but the headroom of Blackouts at 9v is equal to or higher than the EMG at 18.

The hows and whys of our preamp are proprietary. I can't disclose various secrets, but like everything else we talk about here (vintage pickups, Wal bass pickups, etc) anyone can buy one and reverse engineer it. I don't want to "Mike Sulzer" this thing across three pages, so I'll say what I can and hope to move on.

The preamp is quiet. The resonant peak of a coil is pretty narrow, and narrowest at the peak. The at rest noise received within the peak area is not proportionately reduced by the amount the dB reduction the peak undergoes in the loaded coil. One way to think of this is that if the resonant peak of a coil was responsible for substantially more noise than the surrounding frequencies, the self noise of a single coil would be dominated by peak frequency of the coil. That's not how we hear it. In other words, you'd see a meaningful spike in noise at the peak frequency. It's just not really an issue. You don't "lose the cancellation of higher harmonics" as you say. You may affect it, but you do not lose it. That's where I say it is not proportionate. An 8dB flattening of the peak does not equal an 8dB increase in noise in the shape of the gap between the two peaks.

I don't buy the higher dynamic range. Normal peak of the single coil ( that has average of less than 120mV )never goes above 1V peak. Unless you have gain more than 4.5 time or 12dB, you should not hit the hard limit. All you need is an output rail to rail op-amp or common source/emitter output, you can swing from rail to rail( almost for transistor). Unless you use voltage doubler, you only have 9 volt total room. I don't think you want to use step up converter due to switching noise nor the cost would allow you to do so. Unless your increase dynamic range is just using a rail to rail opamp!!!!

If you just imply you have better signal to noise ratio, then I can buy it.

Hey Mike, do you have a way to increase head room of a circuit with a set limit of the DC rail in case I miss it?

[Mike Sulzer]

The hows and whys of our preamp are proprietary. I can't disclose various secrets, but like everything else we talk about here (vintage pickups, Wal bass pickups, etc) anyone can buy one and reverse engineer it. I don't want to "Mike Sulzer" this thing across three pages, so I'll say what I can and hope to move on.

I did not understand the technical stuff you wrote, but if you cannot really talk about it, no problem, let's just let it drop. And if you do not want to talk about it, you can just say so. There are two or folks talking in every three page discussion.

[David Schwab]

The Polish drawn preamp drawing above does not click right for me.
The left coil is loaded by 30K in series with a .022uF cap. Cutoff frequency: around 240 Hz.
The right one is loaded by two 178K resistors in paralell, in series with another .022uF ; cutoff frequency around 82 Hz.
There is no way said coils can cancel 50 or 60 Hz hum effectively, *and* higher frequency noise/interference too.
You *may* optimize turns ratio for one or the other job, not both at the same time.
jm2c

But you will notice how quiet EMGs are. They are totally shielded also. Each coil is wound the same.

[frankfalbo]

I don't buy the higher dynamic range.

You're in good company. Neither did one of our engineers on paper, but he does now. Poor man's test: Plug in the EMG, record direct, bang on the strings. The wav will flatline. No matter how hard you hit, the wav doesn't get any bigger. Swap it for a Blackout and do the same. The wav is bigger. We even pulled 5 dB of gain out of our preamp (for testing purposes, not in the final product) and the wav was still bigger. It was 5dB smaller when playing softly, under the clipping point.

[Alan0354]

You're in good company. Neither did one of our engineers on paper, but he does now. Poor man's test: Plug in the EMG, record direct, bang on the strings. The wav will flatline. No matter how hard you hit, the wav doesn't get any bigger. Swap it for a Blackout and do the same. The wav is bigger. We even pulled 5 dB of gain out of our preamp (for testing purposes, not in the final product) and the wav was still bigger. It was 5dB smaller when playing softly, under the clipping point.

From schematic, EMF use OP134 which when driving a light load, the output swing is about 2V below 8.7V( EMG has protection diode MBD701), so if you use a rail to rail output opamp, You gain that 2.3V already. See the schematic by David on post #2. Also just by strumming the strings is not a good way. If EMG has higher gain( it has gain of 5), it is going to clip much faster. The only true way is to actually look at the output waveform on the scope. If EMF is only 6.7V peak to peak, AND IF you can show on the scope that the Blackout can swing bigger than 9V peak to peak, then you can make this assertion.

I am an engineer for almost 30 years designing all sort of opamp, transistors, RF circuits that is much more advance than those in musical instruments. I yet to get more swing than the power supply voltage short of using step up converters. Using transformer to boost voltage don't count because you don't increase the signal to noise ratio and it really mess up the frequency response. If it the signal to noise ratio that matter, not the total output signal. You can get 100 volt signal going through a stage of 12AX7!!! That don't improve the signal to noise.

[Mike Sulzer]

From schematic, EMF use OP134 which when driving a light load, the output swing is about 2V below 8.7V( EMG has protection diode MBD701), so if you use a rail to rail output opamp, You gain that 2.3V already. See the schematic by David on post #2. Also just by strumming the strings is not a good way. If EMG has higher gain( it has gain of 5), it is going to clip much faster. The only true way is to actually look at the output waveform on the scope. If EMF is only 6.7V peak to peak, AND IF you can show on the scope that the Blackout can swing bigger than 9V peak to peak, then you can make this assertion.

I am an engineer for almost 30 years designing all sort of opamp, transistors, RF circuits that is much more advance than those in musical instruments. I yet to get more swing than the power supply voltage short of using step up converters. Using transformer to boost voltage don't count because you don't increase the signal to noise ratio and it really mess up the frequency response. If it the signal to noise ratio that matter, not the total output signal. You can get 100 volt signal going through a stage of 12AX7!!! That don't improve the signal to noise.

Yes, the signal to noise ratio is defined at the input of the amplifier. It really has nothing to do with the output capability. This statement in particular bothers me: "Many players run the EMG's at 18 volts, but the headroom of Blackouts at 9v is equal to or higher than the EMG at 18." For that to be true, the EMG would have to put out less than 9 volts p-to-p when running on 18 volts. If that is true, then that is more a statement of the inadequacy of the EMG than about the amazing performance of SD's preamp. You are not going to get more than 9 V when using a 9 V battery, as you say. And you should never need more than that, by the way.

So I do not know what they are up to, and I do not think that Frank is going to tell us. In any case, it would probably take a lot more than the three pages he does not want to spend to convince us, and then he would have to kill us (company secrets and all!). So I suggest just letting it go.

Rest assured that there is no magic; despite the complaints about obnoxious engineers and scientists in that other discussion, you can actually put limits on things, but you do have to understand them in order to do that.

[J M Fahey]

But you will notice how quiet EMGs are. They are totally shielded also. Each coil is wound the same.

Dear David, I have no option but trusting you, since I never opened an EMG and it looks like you did.

Yes, I know from practical use how low noise they are.

No, I still don´t trust *the drawing* or schematic posted above, for the reasons I wrote and still maintain.

Are both these statements contradictory?
Not at all.

As A. E. Van Vogt states time and again in "The World of Null-A", .... "the Map is not the Territory" .... in this case meaning "the schematic is not the actual pickup"
Thanks.

[Alan0354]

Yes, the signal to noise ratio is defined at the input of the amplifier. It really has nothing to do with the output capability. This statement in particular bothers me: "Many players run the EMG's at 18 volts, but the headroom of Blackouts at 9v is equal to or higher than the EMG at 18." For that to be true, the EMG would have to put out less than 9 volts p-to-p when running on 18 volts. If that is true, then that is more a statement of the inadequacy of the EMG than about the amazing performance of SD's preamp. You are not going to get more than 9 V when using a 9 V battery, as you say. And you should never need more than that, by the way.

So I do not know what they are up to, and I do not think that Frank is going to tell us. In any case, it would probably take a lot more than the three pages he does not want to spend to convince us, and then he would have to kill us (company secrets and all!). So I suggest just letting it go.

Rest assured that there is no magic; despite the complaints about obnoxious engineers and scientists in that other discussion, you can actually put limits on things, but you do have to understand them in order to do that.

I am going to bet Blackout has less gain than 5 like the EMG and so you can hit as hard as you want without clipping the output. I am out of the industry for only 6 years, I would like to think I am not that out of touch. If anyone can get more signal to noise ratio out of the given input(with noise), they can publish a paper in the scientific journal, get a big patent or win some award!!! Active electronics has never.....I repeat.......NEVER been a gating factor in guitar applications where the peak output of any pup is in hundreds of mV. Even if I let the dynamic range to be 60db.......(which means the smallest useful signal is in hundreds of uV), you are not going to push the noise limit of most of the el cheapo opamps in the market. Most of the opamp are better than 30nV/sqrt(Hz) which is 30uV/sqrt(MHz)!!! Even at 1MHz BW, you only has 30uV!!!! The opamp I am playing and 4558 is only 9nV/sqrt(Hz). The noise is just never a problem.

BTW, who cares about the output, all we care is signal to noise ratio. Just because you can have 1V output vs some vintage pup of 100mV don't mean you are better, it's the signal to noise ratio. It is useless if you pup is loud AND with a lot of noise!!!!

Here is a link on why they don't patent it:

http://www.edroman.com/parts/blackback.htm

[CRU JONES]

OPA134 should be LM4250. The LM4250 is a "programmable" op-amp. By selecting the Rset resistor on pin 8 you can "program" the current consumption, and; more importantly the Slew rate.

Ethan

[David Schwab]

Dear David, I have no option but trusting you, since I never opened an EMG and it looks like you did.

Yes, I know from practical use how low noise they are.

No, I still don´t trust *the drawing* or schematic posted above, for the reasons I wrote and still maintain.

Are both these statements contradictory?
Not at all.

As A. E. Van Vogt states time and again in "The World of Null-A", .... "the Map is not the Territory" .... in this case meaning "the schematic is not the actual pickup"
Thanks.

I'm positive about the schematic either. I know who did it, and he had sent me photos of the pickup (EMG 81) being dissected. They took quite a while to trace the preamp.



I have dissected an SA, but I have not removed the epoxy from the preamp yet. I was more interested in just looking at the guts than to reproduce the preamp.

But if we are to believe EMGs marketing, they say they "tone model" the pickup by tuning the coils. Some of their earlier pickups, like the 58 where not dead quiet, so it was replaced with the 85. But the 58 sounded better, even if it had a little bit of noise.

TONE MODELING
One of the most important aspects governing the tone of a pickup is the resonant frequency. EMG Pickups use "Impedance Modeling" to manipulate the two coils. This innovation allows us to shape a mix of the reactive slope and resonance from each of the two coils. The idea is to achieve a complex mixture of each coils phase and frequency response resulting in a richer tone from the pickup. This means the sound is vibrantly alive with more harmonics than from conventional passive pickups. EMG Pickups like the EMG-S, EMG-SA, and the EMG-60 use this technique to its fullest, while the EMG-81 uses modeling in only a small way. Modeling might work well for a single coil pickup, but not for a design such as the EMG-ACS Acoustic Sound Hole Pickup. As each pickup design is approached differently, it all depends on the final result we're searching for.

So it seems the preamp in the schematic didn't load the two coils much compared to some other models.

We have discussed humbuckers here with mismatched coils, and how far you have to go before noise is an issue. I have an old Hi-A pickup with mismatched coils. One reads 4.62k, and the other is 3.4k. Bill Bartolini has said he used the same gauge wire on both coils. So that's quite a mismatch, and yet the pickup is dead quiet.

[David Schwab]

OPA134 should be LM4250. The LM4250 is a "programmable" op-amp. By selecting the Rset resistor on pin 8 you can "program" the current consumption, and; more importantly the Slew rate.

Ethan

Yes, and that's the same op amp used in the original Musicman basses.

[J M Fahey]

Agree.
Specification of "exotic" or instrumentation grade Op Amps in regular Guitar products, usually screams "noob" designer to me, the kind that thinks that expensive parts mean good sound just by themselves.
The NE5534 shown as an alternative is *most* unlikely, because of battery killing high idle current.
"Poor performance" LM4250 makes sense because of extremely low (and programmable to boot) idle current.
Yes, I know "good" Op Amps may be had for only $2 to $4 and that should not be a factor.
Think again.

EDIT: just checked:
R5 (1M) into pin 8 is the current programming resistor (set for very low idle current) in an LM4250.
That same resistor into either the stated OPA134, OP27 or NE5534 pin 8 not only won´t do that, but will whack output voltage off value wildly, because it´s feeding *one*of the offset compensation points.
That alone, disqualifies the schematic.

[David Schwab]

Here is a link on why they don't patent it:

Seymour Duncan BlackBack  Pickups - Ed Roman Guitars

I don't think that's the Blackouts. I'm not sure what that is. I never heard of Black/Back pickups. Also, they mention some design by "Ultratone division of New Technologies Ltd." But try to find that company's website. The only company buy that name I found was this one: New Technologies Ltd.

I don't think that's the company being talked about.

Frank would know.

[David Schwab]

"Poor performance" LM4250 makes sense because of extremely low (and programmable to boot) idle current.
Yes, I know "good" Op Amps may be had for only $2 to $4 and that should not be a factor.
Think again.

The LM4250 is not a bad sounding op amp. I was actually quite surprised.