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

[frankfalbo]

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.

You are wrong. In fact you just described the EMG X Series preamp. They simply changed a couple resistors to reduce the gain by 6dB. That is how they manufactured headroom. Every other component in the preamp is identical.

Before the original EMG's clip, our output levels are about the same, maybe we're a fraction of a dB higher. But hit hard and the EMG clips before the Blackouts. This is part of the perception that Blackouts are louder than EMG's, but it's not because we've added gain. I agree with you more output isn't always a good thing. It certainly isn't for me. I like vintage, medium, and high output pickups but don't need the extra juice of actives very often.

Ed Roman's Black Back pickups are passive and have nothing to do with Blackouts. I can't understand the connection you're suggesting between them except they both contain the word "black".

[David Schwab]

Frank, some of the best active bass pickups I have ever heard were the old Duncan set with the DIP switches. I installed a P/J set into a bass I put together for my then current girlfriend back in the 80s and everyone would comment on the tone of that bass. They were nice and smooth, and not at all like EMGs, which I was using at the time.

I think these are now the ProActives, sans the DIP switches?

[CRU JONES]

Before the original EMG's clip, our output levels are about the same, maybe we're a fraction of a dB higher. But hit hard and the EMG clips before the Blackouts. This is part of the perception that Blackouts are louder than EMG's, but it's not because we've added gain. I agree with you more output isn't always a good thing. It certainly isn't for me. I like vintage, medium, and high output pickups but don't need the extra juice of actives very often.

.

The reason I pointed out that the the emg circuit uses the LM4250 is because it is "programmed" to have a low slew rate. the OPA134 was causing confusion. The EMG experiences slew limiting on the transients, whereas; maybe the blackouts preamp does not. This is the reason Alan and Mike don't get what you are saying about the blackouts having more headroom than the EMG's- even when the EMG's are running from 18V.

Slew rate limiting isn't necessarily a bad thing. Maybe it's the reason all the active pickup guys are abandoning their blackouts to ebay and are reinstalling their EMG's. The three pin molex connector! It's so easy to get your tone back

Ethan

[Alan0354]

The reason I pointed out that the the emg circuit uses the LM4250 is because it is "programmed" to have a low slew rate. the OPA134 was causing confusion. The EMG experiences slew limiting on the transients, whereas; maybe the blackouts preamp does not. This is the reason Alan and Mike don't get what you are saying about the blackouts having more headroom than the EMG's- even when the EMG's are running from 18V.

Slew rate limiting isn't necessarily a bad thing. Maybe it's the reason all the active pickup guys are abandoning their blackouts to ebay and are reinstalling their EMG's. The three pin molex connector! It's so easy to get your tone back

Ethan

That is an awfully slow opamp and it is quite noisy at over 40nV/sqrt(Hz). What is the point of saving the battery if the performance suffer? The commonly used 4558 is 3MHz GBWP and 2 to 3 V/uS, don't think anyone will complain about slew rate limited. The OPA134 is a much better opamp but at 4mA current!!!

Are you saying the Blackout don't sound that good?

[J M Fahey]

I wrote "poor performance" surrounded by semi-colons because of that.
Itīs good enough where itīs being used.
We live in the electric guitar world, where the cableīs 1000pF of more , plus the high generator impedance (a 500K or 250K volume pot on "7" add respectively 125K or 65K in series), kill more slew rate than any Op Amp used.
Not to forget that guitar speakers usually have a strong peak between 2000 and 3000 Hz, dropping like a brick after that, between 12 and 24 dB/octave.
So in that world, an LM4250 or the other old low current workhorse, TL06x are adequate.
And yes, ear tested "sound good", why not?
After all they are to be compared to the passive pickup situation I described above, not to any recording or Hi Fi equipment.
Under those circunstances, getting a "better Op Amp" which uses 10X to 20X the battery current and does not sound audibly better is not justified.

[Mike Sulzer]

You are wrong. In fact you just described the EMG X Series preamp. They simply changed a couple resistors to reduce the gain by 6dB. That is how they manufactured headroom. Every other component in the preamp is identical.

Before the original EMG's clip, our output levels are about the same, maybe we're a fraction of a dB higher. But hit hard and the EMG clips before the Blackouts. This is part of the perception that Blackouts are louder than EMG's, but it's not because we've added gain. I agree with you more output isn't always a good thing. It certainly isn't for me. I like vintage, medium, and high output pickups but don't need the extra juice of actives very often.

Ed Roman's Black Back pickups are passive and have nothing to do with Blackouts. I can't understand the connection you're suggesting between them except they both contain the word "black".

This sounds like some kind of soft limiting circuit, or whatever might be the right term.

[J M Fahey]

We must be realistic as to *what* we are driving with our pickups.
The typical 12AX7 gain stage has around 50X gain and can swing 250VPP with a 300VDC supply (approximately, letīs not nitpick here, itīs a generic example), so the maximum signal it can accept before clipping is 250/50=5VPP, which can be supplied by most 9VDC powered circuits.
"Regular" Op Amps (such as TL072 and most others) can *just* do it, because they canīt reach +9 and Ground , but rail to rail Op Amps or some discrete designs can.
My point?
"Higher headroom" , if we call so "output swing" is not a bad thing, of course, but canīt be used properly if any higher.

And if we are driving SS gain stages powered from +/-15V or +24/40V ... forget it.
Unless your input stage has a gain of, what, 3x?

[Mike Sulzer]

We must be realistic as to *what* we are driving with our pickups.
The typical 12AX7 gain stage has around 50X gain and can swing 250VPP with a 300VDC supply (approximately, letīs not nitpick here, itīs a generic example), so the maximum signal it can accept before clipping is 250/50=5VPP, which can be supplied by most 9VDC powered circuits.
"Regular" Op Amps (such as TL072 and most others) can *just* do it, because they canīt reach +9 and Ground , but rail to rail Op Amps or some discrete designs can.
My point?
"Higher headroom" , if we call so "output swing" is not a bad thing, of course, but canīt be used properly if any higher.

And if we are driving SS gain stages powered from +/-15V or +24/40V ... forget it.
Unless your input stage has a gain of, what, 3x?

Over driving the first stage is what many guitarists want to do.

[David Schwab]

Over driving the first stage is what many guitarists want to do.

Very true, and is why we have hot pickups.

[J M Fahey]

Fine with me, couldnīt agree more ... but then we need 5VPP or higher pickups, active or otherwise.
If active, and powered by 9VDC, over 5VPP output means that the pickup electronics themselves will clip ... meaning "dreaded SS" distortion and not "smooth, velvety, mojo-full, whatever" Tube distortion.

Can anybody post some scope screen picture showing an over 5VPP pickup output?
Never seen such, I would be most impressed.
Specially if picking, rather than with a Pete Townshend type windmill strumming.

[Mike Sulzer]

Fine with me, couldnīt agree more ... but then we need 5VPP or higher pickups, active or otherwise.
If active, and powered by 9VDC, over 5VPP output means that the pickup electronics themselves will clip ... meaning "dreaded SS" distortion and not "smooth, velvety, mojo-full, whatever" Tube distortion.

Can anybody post some scope screen picture showing an over 5VPP pickup output?
Never seen such, I would be most impressed.
Specially if picking, rather than with a Pete Townshend type windmill strumming.

I think the curves for a 12AX7 show that 3 VPP will put you into substantial non-linearity.

A humbucker can do this.

9V and rail to rail gives you more than 8.5VPP. That will pretty much move you from on to off, which is what some folks want.


(Fender amps bias the first stage between 1.5 and 2.2 volts, draw about 1ma and use 100K plate resistors with a supply of maybe 315V.)



If you want a pickup that can put out 5VPP, use slugs for both coils and put a 3/8" dia. 1/4 inch thick neo on the back of each slug. Of course the instrument is unplayable from the string pull.

[J M Fahey]

OK, thanks.
Good practical info

[Mike Sulzer]

OK, thanks.
Good practical info

And I forgot to add that assembling that pickup was very hard. Magnets flying all over the place. Once was enough! And it sounded dreadful.

it is fun to spend a little time playing with extremes. Puts good practice into perspective.

[Alan0354]

If you use a rail to rail output opamp to drive even a 50K volume pot, you can go to within 25mV typical to the rail, you almost get 9 volts peak to peak output. Even 7Vpp is plenty. I have to check the output of the SC pup on the scope bare, but I venture to guess it is not going to be over 600mV max. At gain of 5, you get 3V peak to peak. I really doubt it is going to hit the rail even.

Let me calculate if the EMG using LM4250. At 10KHz, period is 100uS so each edge is 25uS, say the rise time is 16uS. For Iset of 10uA, slew rate is 0.2V per uS. So 16uS can slew 3.2V only. That is really slow. Even if you say 5KHz is all you can hear from the guitar speaker, you get 6.4V peak to peak, that is not acceptable to me. Why EMG put OPA134 on their schematic and even put OP27 and some other? It never dawn on me that people will use something so slow. If that is what Frankfalbo refer to as Blackout have more output range, I guess so!!!!. But is that the big secret?

If you can live with 70nV per sqrt(Hz) input noise opamp, you can get a ton of other that is using below 300uA and have much better slew rate. I don't have much experience designing guitar electronics, I mainly use LM4558 as a guide line of 3MHz GBWP, 9nV/sqrt(Hz) at about 100Hz and 2 to 3V/uS. My believe is to taking the electronics out of the picture.

One question is why does opamp make a difference in sound? Opamps are very low distortion unless you push it like the LM4250 or clip it. If you want to do clipping or get second harmonics, use FETs!!! FET dI/dV curve has steeper slope like the tubes, you get plenty of even harmonics out of them.