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Double Bass An Ehrlund blog, sort of
- Thread starter drurb
- Start date
I have. Plugged it directly into an AI Clarus. It sounded good, but I needed almost all the gain in the Clarus preamp to get a usable signal.
It sounded the same as it does plugged into my headway edb1-- I didn't detect any obvious impedance related sonic differences. I've also plugged it straight into a mackie srm 150, which is a small monitor with a preamp. It sounds good, no obvious sonic differences not related to the different speaker. But again I have to crank the gain to very very high levels to get a signal.
I have a great old ampeg guitar amp from the late 60s-- later today I'll try plugging into that and see what happens
Ok so I plugged it into an ampeg Gemini, a tube guitar amp from the 60s. Gorgeous sounding guitar amp, not fashionable because everybody wants to sound like fender. But made for mag pickups. Single volume knob--no separate gain control
It sounded good--no piezo artifacts, no obvious sonic oddities. It was louder than I expected. I thought I'd have to turn it way up to get any volume, but seemed to be behaving about like my guitar when I plug that in.
It sounded good--no piezo artifacts, no obvious sonic oddities. It was louder than I expected. I thought I'd have to turn it way up to get any volume, but seemed to be behaving about like my guitar when I plug that in.
Thanks, Francis. I didn't have a proper understanding of electrets. Electret condenser mics are "passive" only in the sense they are operated without the necessity to supply voltage to the capsule. They do typically require power for an FET module. Hmm...does this fit with the behavior of the EAP? Is the module in the Ehrlund pre? Is it in the pickup? Is there a "plug-in power" voltage at the input of the Ehrlund pre? That can be determined, of course. Check here, re "plug-in power." Invalid Link Removedis a nice source as well.
Then again, maybe it's not an electret at all. Inquiring minds want to know!
Thank you.
I have to confess that in my case, I'm in love with music and playing bass, but I'm also in love with electronics and physics. The latter is the basis of my day job. I can't just set one passion aside to concentrate on the other -- somehow I have to find a way to enjoy both!
I have always enjoyed your posts and found your technical work very helpful. Your work on compressors is great, since I have no way to try out that many. It is all about balance...
Thanks, Francis. I didn't have a proper understanding of electrets. Electret condenser mics are "passive" only in the sense they are operated without the necessity to supply voltage to the capsule. They do typically require power for an FET module. Hmm...does this fit with the behavior of the EAP? Is the module in the Ehrlund pre? Is it in the pickup? Is there a "plug-in power" voltage at the input of the Ehrlund pre? That can be determined, of course. Check here, re "plug-in power." Invalid Link Removedis a nice source as well.
Then again, maybe it's not an electret at all. Inquiring minds want to know!
I remember lots of discussion on earlier Ehrlund threads about what is actually in the EAP. Ehrlund isn't telling outside of calling it a linear microphone, whatever that is supposed to mean. I know for sure it isn't piezo but that is all.
Does anyone have a failed unit? We should give it an "autopsy" and find out exactly what is going on in there...
Also, it seems a little strange that they're guarding this secret. Shouldn't a patent protect any innovation they've made? I mean other manufacturers can easily determine what they're doing....
+1 on enjoying and learning from Francis' posts and website, but I must have missed the compressor stuff -- you're not thinking of Cyrus (bongomania) are you?
Kind Sirs,
I've changed the battery inside the Ehrlund Pre Amp a couple of times. Now, I'm no engineer, but the tiny little "magic circuit" is sealed inside some kind of protective composite. I think that it's definitely a chip of some kind and, if you were to try and take a look at it, you might actually destroy the device. All things considered, retro engineering someone else's design seems like a waste of time IMO. Just my opinion though.
Ric
An electret microphone is a condenser microphone where one plate of the capacitor is precharged (over lifetime of the capsule). So using them, there is no need for a capacitor charing voltage.
But since condenser capsules have very very high impedance output (around 1 GigOhms!) they need a FET buffer (basically for the same reason the piezos need them). Directly connected (without the FET) you get almost nothing with a 1 MegOhms input load. So every electret capsule I know comes with the FET stage built-in and needs at least 1.5 Volts around or below 1 mA for the FET to get a loadable output.
I'm sure there is no electret microphone capsule in the EAP since it works when directly plugged into an amp.
But there is electret foil which seems to work without a battery, like in the APT-Flex pickup. The output signal of the APT-Flex is also a bit weak and needs more amplification than most other pickups.
But since condenser capsules have very very high impedance output (around 1 GigOhms!) they need a FET buffer (basically for the same reason the piezos need them). Directly connected (without the FET) you get almost nothing with a 1 MegOhms input load. So every electret capsule I know comes with the FET stage built-in and needs at least 1.5 Volts around or below 1 mA for the FET to get a loadable output.
I'm sure there is no electret microphone capsule in the EAP since it works when directly plugged into an amp.
But there is electret foil which seems to work without a battery, like in the APT-Flex pickup. The output signal of the APT-Flex is also a bit weak and needs more amplification than most other pickups.
I just got my ehrlund preamp and opened it up to put a battery in. It already had a battery. There's very little in there and the important stuff is slathered in epoxy so you can't see what it is.
Later tonight I'll record some cliPs of the ehrlund dry and with the preamp
Later tonight I'll record some cliPs of the ehrlund dry and with the preamp
I was think Bongomanie. Francis stuff is awesome though. I have been putting off buying his HPF for a long time now. I may not need with with the Ehrlund, I have not noticed a real problem.
Ok, here are two clips--the first of me hacking through an old standard with the ehrlund pickup straight into an Apogee duet and then into Logic Pro, no eq of effect
[Invalid or Expired Link Removed]
The second clip is the same standard played through the Ehrlund preamp, into the Apogee Duet, into Logic, no eq or effects
[Invalid or Expired Link Removed]
I think the second clip sounds a little better, fuller and more flat in eq terms, is how I would describe it. It's hard to get the gains even. It's not a huge difference, but I think I hear it. My playing aside, does anyone else hear it?
Still at a loss as to why it would sound better.
Bonus points for knowing the tune
PS Bass is a Shen 7/8 flatback with three year old evah perazzi weichs on it
[Invalid or Expired Link Removed]
The second clip is the same standard played through the Ehrlund preamp, into the Apogee Duet, into Logic, no eq or effects
[Invalid or Expired Link Removed]
I think the second clip sounds a little better, fuller and more flat in eq terms, is how I would describe it. It's hard to get the gains even. It's not a huge difference, but I think I hear it. My playing aside, does anyone else hear it?
Still at a loss as to why it would sound better.
Bonus points for knowing the tune
PS Bass is a Shen 7/8 flatback with three year old evah perazzi weichs on it
The "Preamp ..." sounds better, definitely. More clean and not slightly muffled like the "Dry ..." example.
For people who like a dark sound the dry example may sound better, but I prefer a more open and clear sound which could be heard in the example with the preamp. I also like the lighter lower notes better in the preamp example.
Thanks for posting both examples.
If I ever want to buy Ehrlund (it's more a money thing...), I know now, that I want it with the preamp.
For people who like a dark sound the dry example may sound better, but I prefer a more open and clear sound which could be heard in the example with the preamp. I also like the lighter lower notes better in the preamp example.
Thanks for posting both examples.
If I ever want to buy Ehrlund (it's more a money thing...), I know now, that I want it with the preamp.
I hear the dry clip as more "nasal" and more direct, but not in a pleasing way.
I think, admittedly based on the flimsiest of knowledge, that there is some change having to do with impedance.
Impedance changes slightly with frequency, doesn't it? I wonder if he's varying impedance with frequency? There is so little on the board of the preamp that I suspect some kind of microprocessor. Again I speak from gross ignorance
I think, admittedly based on the flimsiest of knowledge, that there is some change having to do with impedance.
Impedance changes slightly with frequency, doesn't it? I wonder if he's varying impedance with frequency? There is so little on the board of the preamp that I suspect some kind of microprocessor. Again I speak from gross ignorance
Impedance is frequency dependant resistance. So, yes to your first question.
I rather think it is a simple resistor setting the input impedance of the preamp, but the output impedance of the pickup might vary over frequency. Depending on the input impedance of the preamp, there might be more or less attenuation of some frequency ranges, so one have to find the best fitting input impedance for this pickup.
Maybe there is some fixed eq following the input stage to get a non-coloured sound out of the package. I think this is the reason why the Ehrlund preamp works best with the Ehrlund pickup, it is simply made to clean up what the pickup delivers.
I rather think it is a simple resistor setting the input impedance of the preamp, but the output impedance of the pickup might vary over frequency. Depending on the input impedance of the preamp, there might be more or less attenuation of some frequency ranges, so one have to find the best fitting input impedance for this pickup.
Maybe there is some fixed eq following the input stage to get a non-coloured sound out of the package. I think this is the reason why the Ehrlund preamp works best with the Ehrlund pickup, it is simply made to clean up what the pickup delivers.
Here is the analysis that Les (Durb) did on the Ehrlund Pre
"Okay, I decided to find out! As it happens I have a gig tonight so my bass and rig are here at work. I took the Ehrlund pre into my lab. The picture below shows the spectrum of the Ehrlund pre between 0 Hz (DC) and 200 Hz with the switch set to "LOW." The vertical cursor is sitting at 20.5 Hz:"
"Note that the response is essentially flat down to below 20 Hz. I measured the response as being ruler flat up to at least 10 kHz. Changing to the "HIGH" setting increased the gain by 6 7.3 dB with no effect at all on the spectrum. There you have it, folks."
"Now, unless there is a passive front-end filter designed to interact with the microphone itself, then there is no evidence of a high-pass roll-off anywhere near 40 Hz on either setting. I doubt there is such a passive filter."
"Okay, I decided to find out! As it happens I have a gig tonight so my bass and rig are here at work. I took the Ehrlund pre into my lab. The picture below shows the spectrum of the Ehrlund pre between 0 Hz (DC) and 200 Hz with the switch set to "LOW." The vertical cursor is sitting at 20.5 Hz:"
"Note that the response is essentially flat down to below 20 Hz. I measured the response as being ruler flat up to at least 10 kHz. Changing to the "HIGH" setting increased the gain by 6 7.3 dB with no effect at all on the spectrum. There you have it, folks."
"Now, unless there is a passive front-end filter designed to interact with the microphone itself, then there is no evidence of a high-pass roll-off anywhere near 40 Hz on either setting. I doubt there is such a passive filter."
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