Schertler Amp Phantom power buttons

[rockabilly69]

I was a little perturbed when I found out my Schertler phantom buttons are far from what they state they are in the way of voltages. The 10V setting on my Jam 200 only puts out 7.5V and the 24V setting puts out 29.5V. Why this is so perturbing to me is that I really wanted to use the 10V setting on one of the channels to power my internal Highlander pickup in my resonators. Typically you power the pickup with an external power 9V battery box which requires you use two cords, one TRS from the reso to the power box, and one TS from the box to the amp/PA. I thought ten volts phantom would be perfect because when measuring the voltage of a brand new 9V battery it's actually much closer to 10V. As I said, to get the power into the reso from the battery box you have to use a TRS cord (three conductors) and the power comes in on the ring. Well Schertler wire there TRS 1/4" amp inputs to have the power come in on the tip. So I had Highlander make me a special cable (which was kind of expensive) to reverse the leads on one end so that I can have the power come into my reso on the ring. This way I wouldn't have to drag a battery box and the extra TS cord to my gig, as I could plug straight into the Schertler with my special cord. Imagine my surprise when I found out the voltage was only 7.5 v and my new cable was worthless.

This is what Schertler's website lists as specs...

Technical Specifications
Weight 12.2 kg (26.89lb)
Dimensions 324x297x380 mm
Frequency Response 40 Hz to 20 kHz
Speakers 1” dome tweeter, 8” woofer
Construction Birch laminated
Channels 5 independent channels
Inputs Channel 1 Jack 6.3mm unbalanced,
Channel 2/3 XLR balanced
Channel 4 Jack 3.5mm stereo, \
Channel 5 2x Jack 6.3mm unbalanced
Outputs DI, LINE, AUX
Phantom Power 10V on Channel 1,
24V(nominal) and 10V on Channel 2,
24V(nominal) on Channel 3
Effect Digital reverb with Decay


So emailed Schertler and asked if my amp was broken because of the voltages I measured didn't line up with what their specs were listed as...

Here's their reply, which was polite, but still confused me ...

Hi Dan,

thank you for your email and support to Schertler products.


The P10 and P24 phantom provided by the amps follow the nominal labelling for phantom powers and they're subject to tolerances. The values that you measured (for both P10 and P24) are actually correct and in tolerance for the nominal values declared, so there's no actual problem or defect with your amp.

Please remember that the P10 phantom power is designed to let proprietary Schertler condenser transducers work, but we cannot ensure the perfect functioning for other brands devices that may sink low currents.


I'm sorry if this is not what you expected, but there's no problem with your amp.

Should you need any further information, feel free to write me directly.

Best regards
Thomas Brusati
R&D - Lutherie

So what they are saying is the tolerances are +/- 25% for P10???? And all nominal labeling tolerances according to AES is P24 should be within 4 V and 29.5 is out of spec.


And in their advertising they don't talk about using the amp with their proprietary gear. This is all it says in their product description... "Phantom power is supplied for condenser and electrostatic microphones".

[rockabilly69]

Right after I posted this I got another letter from support about possible mod to my amp but I would have to ship to Switzerland to do that and it wouldn't be warranty work so I would have to pay an hour labor and shipping.

[Schertler USA]

Hi Dan,
thank you for the explanation.
I think I found the problem here: the jack plug on the Jam is TS connection, not a TRS, because it is designed for electrect microphones (wich is a standard, like lavalier microphones or Schertler's transducers), both the voltage and the audio signal are connected on the tip of the Jack.

The TRS connection required by Highlander probably carries the signal on one pin, the tension on the other pin and the ground on the last pin. Being the jack plug on the amp a TS connection, even with your special cable, it "reads" just the tension on the tip but the audio signal is not connected to anything, so probably your pickup is fed with the tension and turns on, but you still cannot listen the audio signal (because it is not actually connected).

At this point, I think you should know from Highlander if their system can work as an electrect microphone otherwise I'm sorry but I think you can only keep using the external power supply to feed their system and have the audio connection done.

Best regards

Thomas Brusati
R&D - Lutherie

[rockabilly69]

Thank you for explanation and following up on this. I have been a very vocal supporter of the Schertler Jam series of amps, and although I can't use this phantom power, I still love Schertler amps...

[DDHull]

I was more than a little perturbed by a Schertler rep a few years ago. I was told the amp would have no problem with my GrooveTubes GT-33 microphone, yet when I plugged it in, nothing. The rep told me my mic was broken. I had a phantom power supply with me, ran the mic through that, plugged it in and voila! it worked. A major point to me is cutting down on the number of cords and boxes I need to carry. An item that promises to deliver enough juice to power a professional mic should work with a professional mic. I passed on the amp.

That being said, even Fender's "acoustic" amps won't power a GT mic, and they actually owned GT for a time.

[Rudy4]

Originally Posted by DDHull

I was more than a little perturbed by a Schertler rep a few years ago. I was told the amp would have no problem with my GrooveTubes GT-33 microphone, yet when I plugged it in, nothing. The rep told me my mic was broken. I had a phantom power supply with me, ran the mic through that, plugged it in and voila! it worked. A major point to me is cutting down on the number of cords and boxes I need to carry. An item that promises to deliver enough juice to power a professional mic should work with a professional mic. I passed on the amp.

That being said, even Fender's "acoustic" amps won't power a GT mic, and they actually owned GT for a time.

Many "professional" condenser microphones plainly state that they will NOT work with phantom power below 48 vdc.

I don't know if that's the case with the GT condenser, but it's worth considering that Schertler is listing phantom power as 10 or 24 volts, so they are leaving it up to the consumer to determine applicability of their product for individual use.