An Ehrlund blog, sort of

[drurb]

Originally Posted by Adagio

But the Ehrlund preamp has a HPF built-in, about 40-45 Hz when set to "low" if I'm not mistaking.

I'm not aware that that's the case.

Edit-- 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.

[Adagio]

Drurb you're a very resourceful man, as always! That's some very interesting stuff. Did you try without the preamp? Would you read the same by bowing the E string loudly for instance?

So the high/low switch would be a mere 6db pad?

From EAP website:
High and Low: for adjustment of the input signal, for upright bass use the level Low.

I guess I'm confused about the use of this feature then...

[Ric Vice]

Originally Posted by Adagio

Drurb you're a very resourceful man, as always! That's some very interesting stuff. Did you try without the preamp? Would you read the same by bowing the E string loudly for instance?

So the high/low switch would be a mere 6db pad?

From EAP website:
High and Low: for adjustment of the input signal, for upright bass use the level Low.

I guess I'm confused about the use of this feature then...

I talked with Goran Ehrlund himself about that switch, he commented that the High setting for that switch was intended for instruments other than bass, (i.e. guitar) and you should use the Low setting with a Double Bass.

Ric

[drurb]

Originally Posted by Adagio

Drurb you're a very resourceful man, as always! That's some very interesting stuff. Did you try without the preamp? Would you read the same by bowing the E string loudly for instance?

So the high/low switch would be a mere 6db pad?

From EAP website:
High and Low: for adjustment of the input signal, for upright bass use the level Low.

I guess I'm confused about the use of this feature then...

The spectral measurement I posted was created by feeding the pre-amp with a broadband Gaussian noise source. It is strictly a measure of what the pre-amp does. The microphone was not connected. The response does not reflect its properties. Believe me, the system would not be flat if the response of the transducer were included.

Yes, the "LOW/HIGH" switch simply sets the gain through the device. It's actually a change of 7.3 dB. It does not alter it's power spectrum (frequency response).

Originally Posted by Ric Vice

I talked with Goran Ehrlund himself about that switch, he commented that the High setting for that switch was intended for instruments other than bass, (i.e. guitar) and you should use the Low setting with a Double Bass.

Ric

Ric, I suspect that the recommendation from Goran has to do with the expected acoustic level that's transduced by the mic on different instruments. My educated guess is that the level is substantially higher when it is fitted to a double bass and the pre-amp is set to "LOW" so as not to overdrive it or the amplifier stage that follows it. The response from DC to 10 kHz was unchanged across the two settings, save for overall level. Therefore, the pre-amp, per se, does not have different "tonal characters" across the two settings.

[PB+J]

I just posted clips of the Ehrlund compared to the DYN B, straight into an Apogee duet, no eq or other follderall

Clips: Ehrlund compared to DYN-B

[Adagio]

Originally Posted by drurb

The spectral measurement I posted was created by feeding the pre-amp with a broadband Gaussian noise source. It is strictly a measure of what the pre-amp does. The microphone was not connected.

Sorry I didn't get your methodology at first.

Originally Posted by drurb

Yes, the "LOW/HIGH" switch simply sets the gain through the device. It's actually a change of 7.3 dB. It does not alter it's power spectrum (frequency response).

It's settled then! I would have swear my tone shaping was changing when I hit that switch though...

Originally Posted by drurb

Ric, I suspect that the recommendation from Goran has to do with the expected acoustic level that's transduced by the mic on different instruments. My educated guess is that the level is substantially higher when it is fitted to a double bass and the pre-amp is set to "LOW" so as not to overdrive it or the amplifier stage that follows it.

Perhaps that could also be useful for one who wants to use a particular spot on his bass' top that sounds good but that has a weaker output?

[drurb]

Originally Posted by Adagio

...I would have swear my tone shaping was changing when I hit that switch though...

That's not surprising at all. In open-ended judgments, people often attribute changes in overall loudness to other factors. This fact has often been exploited in selling audiophile equipment. A 2-3 dB mismatch in level of two otherwise identical music systems will often lead to judgments of the more intense sound being "better." So, even though you probably re-adjusted your amplifier's gain when switching to the "HIGH" setting, any residual difference could explain your impression. Congratulations, you're human!

Now, wouldn't it be fun to run spectral analyses on a bunch of amps that people are convinced are "voiced" or are convinced are not? Maybe not, lest it end up with this.

[PB+J]

I just added a clip comparing the Ehrlund to a Revsolo


Clips: Ehrlund compared to DYN-B

Ehrlund wins again, though not by as much as I expected

[Badong]

So most of you find the Erhlund preamp to do a better job with this PU than the fDeck? I have a series 1 and 2.

[VegasGutPlucker]

I find the preamp indispensable with the pickup. The one time I forgot it and had to use the fdeck I was sorry. Less volume, different tone shape, just not the same. Not slamming the fdeck at all, it's a great tool but does not have a place in my EAP setup.

[Ric Vice]

Originally Posted by Badong

So most of you find the Erhlund preamp to do a better job with this PU than the fDeck? I have a series 1 and 2.

While I think the FDeck is a wonderful device, it's not the way to go with the Ehrlund, as I've experimented with all of the different versions of the HPF and the EAP. Goran designed and matched the Ehrlund Pre Amp to his pickup, so it will give you the optimum volume and timbre from the device. Even the Headway EDB-1 won't do that, although it does work.

Ric

[Badong]

OK, jumping on the band wagon here. I just ordered the EAP with the preamp. Will update once I get to play with it.

@Ric - Thanks for that. I was debating about whether or not to order the EDB-1 or the Ehrlund preamp. I feel better about my decision now.

[PB+J]

I'm not doubting anyone's experience, but I have to wonder what kind of secret sauce could be in the Ehrlund preamp that can't be duplicated with another preamp. There's impedance, and there's EQ, and I'm not sure what else could be different. There are a lot of preamps out there with a pretty sophisticated set of parameters--the headway, for ex.--and it's hard for me to see what could be different

For those who've done the comparison, what was the nature of the difference?

[drurb]

Originally Posted by PB+J

I'm not doubting anyone's experience, but I have to wonder what kind of secret sauce could be in the Ehrlund preamp that can't be duplicated with another preamp. There's impedance, and there's EQ, and I'm not sure what else could be different. There are a lot of preamps out there with a pretty sophisticated set of parameters--the headway, for ex.--and it's hard for me to see what could be different

For those who've done the comparison, what was the nature of the difference?

Take a look right here and here.

The response of the Ehrlund pre-amp is ruler flat from below 20 Hz to at least 10 kHz. There is no "eq." The "High/Low" setting affects only the gain through the device.

The fdeck also has a flat response.

What I don't know is what is the response of the Ehrlund transducer plus pre-amp as a system. That's difficult to measure as the device responds more to transmitted mechanical vibration than to acoustic energy. I haven't tried the Ehrlund transducer with the fdeck for more than a few seconds. To the extent that the response is different through the Ehrlund pre vs. the fdeck, as far as I can tell, that difference would be related to how the device is loaded by each pre-amp's input impedance.

One could measure the spectrum of the transduced sound of a given bass through the Ehrlund pre and through the fdeck pre. Maybe I'll get around to that...

[Ric Vice]

Originally Posted by PB+J

I'm not doubting anyone's experience, but I have to wonder what kind of secret sauce could be in the Ehrlund preamp that can't be duplicated with another preamp. There's impedance, and there's EQ, and I'm not sure what else could be different. There are a lot of preamps out there with a pretty sophisticated set of parameters--the headway, for ex.--and it's hard for me to see what could be different

For those who've done the comparison, what was the nature of the difference?

PB+J
Since I hadn't compared the two devices since I purchased my HPF Version 3, I just went out into the practice room and did a quick A/B comparison into a pair of Fostex T50RP headphones, using my Fodera Private Practice Amp.
While the new HPF Version 3 certainly sounds fine, the Ehrlund Pre Amp has better bass response and more volume into the same device. Turning the volume knob on the Ehrlund quickly yields a significantly louder signal with better tone quality. While the Headway EDB-1 has a excellent 5 band EQ with all the bells and whistles, it's to much of a good thing into my two Walter Woods amps. The only way I can use it is directly into the power amps of the Woods, or as the pre amp for a QSC K8 Speaker.

Ric

[drurb]

Hmm... I'd like to know what is the input impedance of the Ehrlund pre.

[PB+J]

I've had a couple more gigs with the Ehrlund and I'm really sold on it. Even without the Ehrlund pre, it's an easier sound to deal with than the DYN-B I was using. It's reasonably flat and has no piezo artifacts. I've had zero problems with feedback. I haven't felt the need to move it around and am probably going to cut the extra cable shorter.

Last night I had a relatively low volume gig and fed the Ehrlund straight into the left input on a Mackie SRM 150, which is a small personal monitor. The Ehrlund sounded great, even with the relatively primitive EQ on the Mackie. All I did was roll off a little high end.

One thing I'd say about it is that it needs a LOT of gain. I had the gain control on the Mackie full up, and I generally have the gain control on the Headway close to full as well. What's the signal level coming out of the Ehrlund Pre?

[Ric Vice]

Originally Posted by PB+J

......I haven't felt the need to move it around and am probably going to cut the extra cable shorter.


One thing I'd say about it is that it needs a LOT of gain. I had the gain control on the Mackie full up, and I generally have the gain control on the Headway close to full as well. What's the signal level coming out of the Ehrlund Pre?

PB+J
I'd be pretty conservative about shortening the cable to much, IME it's better to have a little extra stowed with a cable tie than, have it to short.

The Ehrlund Pre Amp gives you a significantly higher gain from the EAP into an amplifier. That's why I like it so much, it's a no mess, no fuss, Volume control that's right under your fingertips or belt loops.

Ric

[drurb]

Originally Posted by Ric Vice

PB+J
I'd be pretty conservative about shortening the cable to much, IME it's better to have a little extra stowed with a cable tie than, have it to short.

The Ehrlund Pre Amp gives you a significantly higher gain from the EAP into an amplifier. That's why I like it so much, it's a no mess, no fuss, Volume control that's right under your fingertips or belt loops.

Ric

Agree, agree, agree! I shortened the cable but kept an extra loop as seen here. I have changed from the Gollihur-supplied jack (seen in the pics) to a Switchcraft. The gain is likely pretty hefty through the Ehrlund pre, I'm guessing substantially more than through the fdeck. I didn't check that when I made my measurements.

[Adagio]

Originally Posted by Ric Vice

I'd be pretty conservative about shortening the cable to much, IME it's better to have a little extra stowed with a cable tie than, have it to short.

While I agree you don't want to shorten it too much, it's no use either to keep too much. When I first got my Ehrlund, I tried it everywhere on my bass, including sides, back, even the tailpiece and the head scroll. I found out that the only area I can get a usable sound is located in between the f holes, lower than the bridge. So after a few weeks of experimentation I shortened the wire but I kept an extra 6" in case I changed my mind. As a result, I shortened it again a month or so afterwards, because the extra length was a hassle to manage often caused unwanted "distortion-like" sound as it was touching something else. The cable is now shortened at less than 10" and I have no regrets whatsoever, I never experienced the same kind of problems since then. Even when I place it closer to the tailpiece, I can orient the PU so the wire is looping around.

Originally Posted by drurb

I have changed from the Gollihur-supplied jack (seen in the pics) to a Switchcraft.

So did I! It's a nice upgrade IMO, I think we may have different version, but I can't really tell from your pics. Mine is the guitar endpin version, it's going through tailpiece so it's easier to plug the FC simultaneously with a twin 1/4 cable.

My Ehrlund is currently placed below the bridge on the treble side, I don't know why but it always sounded better on this location for in-ear monitoring and direct recording. When it's too close to the bridge, the signal is "peaking" but at a reasonable distance it sounds just perfect, very woody. The signal is a bit weaker than the usual "sweet spot" on the bass side, but still, very usable.