[S.O.]

Hello Sound Skulptor Team,

I asselmbled the DI503J and everything is working fine, except the reamping function. In reamping mode, the signal, coming from the "out" jack, is very quiet. The reamp-potentiometer is working but the signal level is very, very low. I have to activate the preamp of the device. Otherwise, reamping is not possible due to the low signal level. The rest of the signal chain is okay because when using another passive reamp box, all works as expected.

Now, I want to find out if I did a mistake during the assembly and if yes, where the error is located in the DI503J signal path. Could you give me an advice how to measure that? I have a digital multimeter and a Rigol oszillioscope. The DI503J is connected to a 501 single host via an XT500 extender.

Best regards,

Stefan

[JPK]

This test can be done without power because the reamp circuit is passive:
Check your reamp signal arrival on the XT500 between pins 8 & 10.
You should get a similar signal but 30% lower on pot P1 between the 2 side pins.

[S.O.]

Thank you for your fast response. I connected the "out" and "instrument" jacks with an patch cable and measured the signal as follows:

1. Channel 1 at XT500 pins 8 & 10. Channel 2 at pot P1 pins 1 & 3. Pot P1 turned fully counter clockwise. (see probe locations and osci-plot at pictures).
https://drive.google.com/file/d/1Jk8ZcMMbHLgpYk1_dtmxkztYjzTfwCzx/view?usp=drive_link
https://drive.google.com/file/d/1JiQwnnQV-ol7DF7o0LJJwaQqOPnom6ye/view?usp=drive_link

2. Channel 1 at XT500 pins 8 & 10. Channel 2 at XT500 pins 2 & 4. Pot P1 turned fully clockwise.
https://drive.google.com/file/d/1K6pycRZt1gy7PSBQMaqo-VcAWtPI3xYJ/view?usp=drive_link
https://drive.google.com/file/d/1K9ol95WocO1HwssxOpYnDjJPzWh57bNy/view?usp=drive_link

I think signal at pot P1 is okay. But in my opinion the signal at channel 2 at measurement 2 does not arrive correctly. I am not an electronics pro. Does the measurement 2 make sense?

[JPK]

I would recommend to use a DMM in AC volts mode instead of a scope because the scope Ground clip is common to both channels and this may affect the measurement.

[S.O.]

Hello JPK,

sorry for the late response. I measured with an DMM in AC Volts mode. Testsignal: Sine wave, 1kHz. 

At XT500, between pins 8 & 10: 973 mV

Pot P1 turned fully counter clockwise:
Voltage at Pot 1 between side pins: 672 mV

Pot P1 turned fully clockwise:
Voltage at Pot 1 between side pin & pin 2: 620 mV
Jensen Transformer T1, between pin 5 & 8: 592 mV
Jensen Transformer T1, between pin 1 & 4: 48 mV

I measured also the DC resistances at the transformer sides:
Primary, between pin 5 & 8: 3,9 kOhm
Secondary, between pin 1 & 4: 61,5 Ohm

Does the voltage at the secondary side of T1 make sense? 

Best regards,
Stefan

[JPK]

Voltage at Pot 1 between side pin & pin 2: 620 mV
Perfect.

Jensen Transformer T1, between pin 1 & 4: 48 mV
Normal. The Jensen transformer has a 10:1 ratio.

It looks like your unit is working.

[S.O.]

Sounds good, thank you. But I am still a little confused. Maybe, I am wrong what I am expecting from the DI503J.

I thought, if I am sending a line signal from the DAW into the DI503J and reamp it passive without operating preamp, the returning signal from the lunchbox output is equal or higher in level depending on the reamp potentiometer setting.

Now I measured three configurations in my DAW:

Configuration 1:

• 1000 Hz sine wave - signal directly routed to stereo out

Signal level: -15.9 dB

Configuration 2:

• FX-Loop connected by patch cable.
• Audio interface preamp gain adjusted to match level according to config 1.

Signal level: -15.7 dB

Configuration 3:

• DI503J inserted in FX-Loop
• Re-amp mode active
• Out- and instrument jack connected by patch cable
• Re-amp level potentiometer turned fully clockwise
• Interfce preamp gain untouched (same gain as at config 2)

Signal level: -41.8 dB

Configuration 1
Configuration 2
Configuration 3

As you can see, the returning signal from the DI503J XLR output is 27 dB lower as the sent input signal. Therefore, I thought, I did a mistake during the assembly. Is that signal drop intended by the circuit design?

[JPK]

if I am sending a line signal from the DAW into the DI503J and reamp it passive without operating preamp, the returning signal from the lunchbox output is equal or higher


The DI attenuates the input signal ten times (-20dB) to bring it down to microphone level. The DI output must be connected to a microphone preamp (internal or external).

The reamp just takes a line level signal and attenuates it with a potentiometer to make it compatible with an amp input.

[S.O.]

Hello JPK,

okay, thank you for your support. Now it’s clear what mistake I did. In my home studio I connected a patchbay to the line in- and outputs of my audio interface. My mistake was, that the passive reamped returning signal from the lunchbox output was connected to patchbay, and thus to a line input with too low input impedance. Now I connected it to a high impedance input and all is working fine.  I am happy that I did not make an assembly mistake.  Btw, with operating internal preamp it worked already, I was just wondering about the signal levels when reamped passive.

So, problem solved. Thank you!

Best regards!