AMS Neve 1073 Sweeps

Aaronrash · Jan 1, 2014

Hi,

I'm looking for somebody who owns a Neve1073/1084 to run some sweeps with the EQ disengaged, preferably up to 100Khz. My tech and I are trying to diagnose some issues with some units I have and it would be highly beneficial if someone could provide sweeps. Here's my unit in REW

Aaronrash · Jan 1, 2014

Super high res

ruffrecords · Jan 1, 2014

The bottom end looks fine to me but there seems to be the beginnings af a serious resonance just above 50KHz.

Cheers

Ian

Aaronrash · Jan 1, 2014

ruffrecords said:
The bottom end looks fine to me but there seems to be the beginnings af a serious resonance just above 50KHz.

Cheers

Ian

Hi Ian,

This is actually a artifact caused by my AD/DA. Or at least that's what I think, but there's no way to be sure without an AP

Aaron

ruairioflaherty · Jan 1, 2014

Aaronrash said:
This is actually a artifact caused by my AD/DA. Or at least that's what I think, but there's no way to be sure without an AP

Easily proven by doing a loopback test with your AD/DA?

Biasrocks · Jan 1, 2014

ruairioflaherty said:
Aaronrash said:

This is actually a artifact caused by my AD/DA. Or at least that's what I think, but there's no way to be sure without an AP

Click to expand...

Those modules should be terminated with 600 ohms, if they're not that would most likely explain the resonance at 50khz.

Regards,
Mark

ruffrecords · Jan 2, 2014

Biasrocks said:
Aaronrash said:

This is actually a artifact caused by my AD/DA. Or at least that's what I think, but there's no way to be sure without an AP

Click to expand...

Those modules should be terminated with 600 ohms, if they're not that would most likely explain the resonance at 50khz.

Regards,
Mark

They will drive a 600 ohm load but they should not need to be terminated in 600 ohms.

You can get a low frequency resonance from the transformer primary inductance and the output capacitor but this is damped by the amplifier output impedance in parallel with the reflected load. As the amp output impedance is much lower than the reflected load the damping is much the same for any load.

High frequency resonances are usually caused by leakage inductance resonating with the winding capacitance. It is my understanding that the Zobel network across the transformer secondary is intended to manage this.

Cheers

Ian

CJ · Jan 2, 2014

rolloff at 50 K seems normal,

low freq damped sine wave could be blocking cap in measurement device resonating with xfmr primary,

bruno2000 · Jan 2, 2014

I can post some sweeps from my Dual Mid 1084 and 1073 Lite (with several different transformer combinations) clones if that would help. They are, however clones, and not commercial products. I am using an Audio Precision System Two.
Best,
Bruno2000

Biasrocks · Jan 2, 2014

ruffrecords said:
I'd still be curious if terminating them at 600 would take care of this.

Also, according to the 1073 manual, there must be a 5K1 resistor placed between pin E and K in lieu of a fader being present to get a flat response.

Per the manual: Frequency Response: +/-0.5dB 20Hz to 20kHz, -3dB at 40kHz Eq
Out.

Regards,
Mark

CJ · Jan 2, 2014

a resistor will certainly flatten out any hi rez peaks,

600 ohms might be too much, it could roll off the high end to quickly,

try 2K and see what happens,

Aaronrash · Jan 2, 2014

Here's my loopback response with my interface.

The little rise at 50K is there but not very much.

Aaronrash · Jan 2, 2014

Here is the sweep through the EZ, unterminated into the standard zobel

Aaronrash · Jan 2, 2014

bruno2000 said:
I can post some sweeps from my Dual Mid 1084 and 1073 Lite (with several different transformer combinations) clones if that would help. They are, however clones, and not commercial products. I am using an Audio Precision System Two.
Best,
Bruno2000

Hi Bruno,

That would be great if you could post some sweeps on your units, even though they're clones it would still be educational. Preferably up to 100K

Aaron

ruffrecords · Jan 3, 2014

Biasrocks said:
I'd still be curious if terminating them at 600 would take care of this.

Also, according to the 1073 manual, there must be a 5K1 resistor placed between pin E and K in lieu of a fader being present to get a flat response.

Per the manual: Frequency Response: +/-0.5dB 20Hz to 20kHz, -3dB at 40kHz Eq
Out.

Regards,
Mark

Terminating with 600 ohms and repeating the sweep is definitely worth doing as is checking for the 5K1 resistor. Good points.

Cheers

Ian

ruffrecords · Jan 3, 2014

CJ said:
rolloff at 50 K seems normal,

low freq damped sine wave could be blocking cap in measurement device resonating with xfmr primary,

I am becoming confused (again). I thought the top trace was amplitude which means a peak at 50K.

Cheers

Ian

AErige · Jan 3, 2014

you're right Ian : top is amplitude. bottom is phase.
For CJ's defense, a graph without details for axes is often no good. and maybe our good old pal is still celebrating new year's eve

Aaronrash · Jan 3, 2014

Hi guys

Yes sorry I forgot to clarify, top is amplitude and bottom is phase.
I'll try into a 600Ohm as well to see how much frequency response is affected.
The 5K fader pot is in per Neve manual, all is good on that end

Tekay · Jan 3, 2014

Here we go.
Neve 31102, EQ out, 0dBu input with gain at 10dB. Same signal flow as in a 1073
Top = no termination
Bottom = 604ohm termination

Hope this helps!

AErige · Jan 3, 2014

sweeps in REW with 2 different ez1073 units : one with modern parts , the other with vintage parts. 3 different transformers (vtb1148 manufactured in 2012,vtb1847 manufactured in 2009,vtb1847 manufactured in 2011) and with 600 ohms termination.

AMS Neve 1073 Sweeps

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