DJ PRE II Preamp Constantly Clipping...

[hanzo]

I've picked up an DJ PRE II Preamp and noticed whenever I put the needle on the record at the 'lead in' (before the music starts) the clipping led goes red immediately.

When I turn up the 'gain' (after the music starts), the led will flash green then occasionally red. The led will never be off (no colour) when the needle is on the record.

If I turn the gain to zero, I get solid red.
If I turn the gain fully clockwise, I get solid green.

I even tried changing needles (Ortofon Digital MK2, Shure M44-7) but with the same result.

My setup:

Technics 1200MK2 -- RCA x2 + Ground --> Preamp Line In (DJ PRE II) Preamp Line Out --> Line 1 (DJM-450MK2 Mixer) --> CD (Onkyo Amp).

The goal is to by-pass the mixers (this mixer's preamp is rubbish) Phono Preamp. If I ignore the clipping led and leave the Gain at like +2. The audio sounds ok to my old mans ears.

Ortofon Digital MK2
Output voltage at 1000Hz, 5cm/sec. - 10 mV

Shure M44-7
Output Voltage
Typical at 1 kHz
9.5 mV RMS at 5 cm/sec peak velocity

Are my DJ cartridges output too hot to use this phono pre-amp?

For example the Nagaoka cart M150 is half the output..

• Output voltage: 4,5mV bei 1kHz, 5cm/sec.

Thank you.

 

[cgallery]

Does the signal get louder when you turn the gain knob clockwise (and the led turns solid green)?

I wonder if they installed the wrong pot by accident.

Seems like something internal is wired incorrectly.

Can you exchange the unit?

 

[hanzo]

Thank you for commenting.

Yes, when I turn the gain fully clockwise it turns solid green.

Here is what I sent to the retailer. I'm waiting for a response from them. I think (and hope) you might be right!

One would have thought there would be better QA on these things, but then it's a very cheap unit comparatively speaking...

The symptom is that the Gain control and LED indicator appears to be indicating incorrectly. It is constantly indicating clipping (red indicator) when the music is playing.

Below is from the manual (https://artproaudio.com/framework/uploads/2018/06/DJPREII_Manual_A6_V1.3.pdf)

5. Adjust the gain control so the indicator briefly indicates clipping (red) during the loudest portions of the music. If the sound is distorted and the led is red constantly, turn the gain down.

My understanding is that:

When the needle is dropped and the music/signal is *not* clipping, the led will be green.
When the needle is dropped and the music/signal *is* clipping, the led will be red.
When the needle is dropped and there is no music/signal, the led is off.

But this unit is indicating:

When the needle is dropped and the music/signal is *not* clipping, the led is red.
When the needle is dropped and the music/signal *is* clipping, the led is green.
When the needle is dropped and there is no music/signal, the led is off.


When I turn the Gain all the way down (fully anti-clockwise) and the led will be red.
When I turn the Gain all the way up (fully clockwise) and the led will be green.


I have tried 2 different turntables and 3 different cartridges (Shure M44-7, Ortofon Digital MK2, Stanton Disc Master II) all with the same symptoms.

 

[hanzo]

Just a follow up on this one. I received a replacement unit and it now works as advertised.

Hope this helps someone.

 

[DSJR]

Those pickups do have around twice the output of a typcal MM, my favourite AT's give 3mV at 5cm/s for example...