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Post subject: 150 low Volume
Posted: Mon Sep 13, 2010 11:39 am
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Hello Ken and everyone,

I sold my old, bulky PA and bought the Passport Pro 150 for it's ease of use and portability. Sorry to rehash this topic, as you have addressed it before, but I have a little different take that merits investigation. And of course, the proper subject title would be "apparent low gain on line inputs", but "low volume" is easier to search for.

Basically, all the previous amps I've used worked fine with the output from my Takamine 132 series guitars with their built-in preamps. Using the line inputs on those other amps and powered mixers delivered full audio output at the speakers, no problem. But with the 150, my Takamine CP-132SSC, creates only enough sound for private listening when I run it into a line input. And this is the problem that others have written about. Although certainly a few were trying to plug bare magnetic pickups into line inputs, and we know that won't work, I think some users are justifiably concerned that that internal-preamp instruments that had worked with line inputs on other systems, just don't get amplified enough in the 150.

I don't have a VU meter, so can't guarantee that my Takamine is at 0 dBm, but it still works in other guys' amps, and when they plug their guitars and ukuleles into the 150, they are surprised that it does not amplify sufficiently.

So the issue is, that maybe 150 does meet specs (though the Fender spec pages that I've found don't expressly mention input sensitivity for line inputs) yet functionally, it just isn't working with a lot of instruments out there that have built-in preamps. And those instruments are working with other mfr's gear.

As a "tote, plug and play" device, we are really paying for compact size and ease of use and it would be better if the 150 did work with the large majority of preamped intruments. Sadly, I've taken to carting around a small mixer with the 150. One more power cord needed, more cable and clutter on the floor--a real detraction from the ease of use feature that got me into Fender Passport. One forum member asked for your recommendation for a preamp. That would be a good recommendation to offer. Another choice, if you have enough channels on your Passport, is to to purchase a passive impedance matching device from the local electronics store. These cost $19, accept a 1/4" phone plug and will plug into one of the 150's XLR inputs without any extra cables.

The best solution would be a little resistor change internally to boost the gain in the line input stages. Or a recommendation for a battery powered preamp that didn't add to the cable count. I may be completely off-base, but this does reflect my experience, and I believe the experience of others.

This forum is a good resource, thank you and I hope we can get everybody playing at full volume.

Bill


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Post subject:
Posted: Mon Sep 13, 2010 5:58 pm
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Joined: Tue Feb 09, 2010 1:39 pm
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Location: Scottsdale
Hi Bill,

Thank you for your post. Most of the posts here seem to come from people trying to plug in their electric guitars without pre-amps into a line input. Not only will the line input not provide enough gain, but also the impedance mismatch will make it sound dull.

Most guitars with a built-in pre-amp will work fine. The Passport was setup to provide full power output at a nominal unbalanced signal of -10dBV which is consumer audio line level. If you are using balanced signals of +4dBu (pro level) the Passport will easily provide enough gain to get full volume output (master volume set to max, channel level se to about 1PM). We have tested the Passport with several Fender acoustic guitars with pre-amps as well as other line level products like our GDEC, even iPod's etc. and we didn't have any problem producing full power out.

We didn't add excessive gain to the line inputs because one of the major complaints we received from previous Passport users was that they were noisy.

I don't know what the output of your Takamine guitar is but if it would put out consumer level line output levels (-10dBV) then you should have plenty of gain. As I said we've tested it with many Fender acoustic guitars that have built-in pre-amps without any issues. People here are using Passport systems for rehearsals and gigs, and we're using them for company functions without any issues.

Furthermore, if your guitar doesn't provide enough gain or if it doesn't have a pre-amp for it, the easiest thing one could do is using a DI box. Plug the output of the guitar into the DI box and plug the low impedance output of the DI box into the mic input. This will not require any power, you will get plenty of gain for any high impedance or low level output and you won't need any external power either.

Considering that we have sold thousands of these units we only received a handful of posts and calls from people that they cannot plug their Strat into the Passport directly. After informing them that they should use a DI box most users are extremely satisfied with this solution as it will not only provide them with enough gain but also will fix the impedance mismatch and make their electric guitar sound good, and not dull.

Again, I don't know what the output of your Takamine pre-amp is, but if it were consumer level line output then the line in should function as designed.

Hope this helps!

Thanks,
Ken

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Ken Porter
Director, Audio Electronics R&D
Research & Development
Fender Musical Instruments Corp.
www.fender.com

Proud to be a Fender band member since 1997
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Post subject:
Posted: Tue Sep 14, 2010 8:30 am
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Joined: Sun Sep 12, 2010 12:23 pm
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Ken,

Thanks for the prompt reply. Yes, the "local electronics store $19 phone/XLR" impedance and balance device that I mentioned is I believe, equivalent to the passive DI that you mention. The $19 device has the advantage of being a rigid metal cylinder that plugs into to the XLR jack and therefore does not increase cable count or leave a box on the floor for your chair leg to land on. But this arrangement does use up one of your XLR inputs. A similarly rigid pre-amp that could go straight into the 1/4" phone jack input would be ideal. Do you know of any?

One of these days, I'll get a VU meter and let you know of the output level for some of these instruments. Thanks for the data on input sensitivity: Line input is -10 dBV.

Bill


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