The Steel Guitar Forum

My Quilter US block got fried back in August and I’ve used the contact form on their website and still haven’t heard back from them.

I’ve played over 50 shows with that amp and enjoyed it while it worked. I’ll bring a small speaker cab and for the smallest rooms, just the speaker is plenty enough volume (even able to be heard well over some drummers). For larger rooms I’ll just run the line out to the sound tech and use the speaker as an extra monitor for myself in addition to whatever the monitor situation is at the venue.

Well… at one club my sound came out totally fine through the PA but the speaker I was using to monitor the sound was sputtering in and out and really distorted. Turns out at the venue’s system was sending phantom power which I believe to be the culprit. Ever since that gig my line out works fine, but my speaker output is still distorted.

Looking for somebody from Quilter to replace my amp as I was relying on it so heavily as it seemed like the perfect solution (for me) to play any sized venue with a consistent sound without breaking my back with other amps.

Also wanted to warn all of you not to use the line out live without a phantom power blocker and/or be VERY communicative with your sound tech before anything gets plugged in

714-519-6114

That’s their sales number…they’ll connect you to service

Zoots, everyone should be aware of the dangers of a PA with Phantom Power. Here is what Phantom Power is: On many big PA system there is a switch that will send two lines of 48 volts out on the XLR cables. To turn on Phantom power a switch has to be turned on--- on the PA. Most PAs use XLR cables. XLR cables have two signal wires and a shield around the twisted pair of signal wires. The two signal wires carry two sine waves 180 degrees out of phase to the PA. Inside the PA the two 180 degree out of phase sine wives are converted to one signal through a differential amplifier. The differential amplifier only amplifies the difference in the two sine waves. The differential amplifier will not amplify noise common to both signals. XLR cables are called balanced lines and eliminate noise.
The problem here is this: The two signal wires of the XLR cable can send voltage back on the same wires. Meaning the 2 wires in a XLR cable can send sine waves one way and receive voltage back the other way----on the same wires at the same time!!!!!! The voltage going back is 48 volts on each of the signal wires. Most of the time this 48 volts is intended for Phantom Powered microphones. The problem is XLRs connected to equipment not designed to received this voltage. For example most integrated circuit chips are only rated at 35 volts. So you can see why problems happen when two lines of 48 volts hits a single supply IC circuit chip rated at 35 volts.
Beware of sound guys who don't know what they are doing.

Interesting. I just looked at the manuals for the Tone Block amps and none of the ones I looked at said anything about phantom power on the XLR outs, one way or the other. It would be good to know if that's generally a problem, or not. I use my Tone Blocks in exactly the same way as Zoots - speaker as my monitor, XLR to PA.

Doesn’t sound like anything to do with phantom power being sent to the device. Sounds like a blown speaker. Anyway, this is from Quilter’s FAQ page.

WHAT WILL HAPPEN IF I AM PLUGGED IN TO A MIXER AND SOMEONE SENDS PHANTOM POWER?
The Line Output accepts phantom power without any stress or problems at all.

Also, in regards to this statement “Beware of sound guys who don't know what they are doing” it should be noted that many/most professional analog mixing consoles have just one switch for phantom power, meaning it goes to all channels or none. While there are situations in which the 48v power feed can cause problems, it’s obviously not universal or even common to have this destroy gear.

Sorry if I caused alarm concerning Quilter. It was my favorite amp for live application and hopefully it’s just a fluke.

I have tried using it with other speakers and still had the same issue so it’s not a blown speaker.

Also the sound while it was connected was like a downward sawtooth tremolo chopping up the volume with chirping sounds and pulses even when I wasn’t playing. I have played the club since then and for the sake of troubleshooting I brought my speaker back in and had none of the sputtering/chirping/pulsing after phantom power was turned off. I now use the line out of it into a powered monitor and let the sound tech use the thru out of the monitor if they need to.

I will call them ASAP. Thank you Ken for their contact

If you don't get any help from them I would be happy to look it over and see wgat it needs, if the line out still works and the speaker is good the fix should not be difficult

I've dealt with Quilter support. I would rate them excellent and on a par with Telonics and Hilton. On a problem with a Steelaire I even had a call from Pat Quilter.

I checked the schematic on the "direct out" output from one of my bass amps -- on each of the two signal lines, there is a 50V capacitor in series, so that's about 2:1 voltage protection against phantom power damaging anything.

I've heard that you can't use ribbon mics with phantom power. Also, when you connect/disconnect with PP on, you could get a substantial pop which is unpleasant.