PD170 Audio Mod

[Pete Wilie]

I have been reading about the Greg Winters audio mod for Sony VX1000, VX2100, PD150, and PD170 that provides a 20db improvement in S/N. His original mod was for the VX series. For Greg's comments specific to the PD170 see his post VX2100 Schematic and Mod. See Winterized PD150 Before & After for tests/comments by Jay Rose.

While I very much like obtaining this improvement in audio, I am concerned about modifying my PD170. And I really wonder if it is necessary for the PD170.

Rather than modifying a PD170, I wonder if an alternative approach would provide just as good audio.

If the audio quality of your PD170 (which has a 6db improvement in S/N over the PD150) is still not acceptable, then what about using the PD170 LINE IN with an external mixer/preamp, or recording audio to a separate device like either of these devices:

1. iRiver Portable Digital Recorders-Players
2. Sony Hi-MD™ Walkman® Digital Music PlayerMZ-RH910

The price of either of these is significantly less than the Greg Winters mod, plus it gives you the added benefit of recording audio independently from the camcorder. And it continues to work for any camcorder you now have, or may purchase in the future.

Wouldn't using the PD170 LINE IN bypass the noisy PD170 preamp that is fixed by the Winter's mod?

With the Winter's mod to the PD170 you have to buy some type of mixer/preamp to generate the LINE input the mod expects. With the other recording devices, you have a choice of using either mic or line inputs. I would imagine for best audio you would still want to purchase a mixer/preamp to feed the audio recording device.

Your thoughts/comments?

[Mike Rehmus]

IIRC, Line In is inoperative in Camera mode. It only works in VCR mode.

A reasonable question to answer, before one goes beyond the PD's audio capabilities is of what use is the target use of the footage? If there is going to be any background audio such as music, normal environmental noise, etc., the improvement will not be detectable.

The only place I get concerned is when I'm working on a very quiet stage and need to capture very clean dialog or music from a single source (like a guitar or flute). Then I may reach for the DSR-300 or a separate recorder and a studio microphone. But then, in those situations, a second audio setup is easier and better.

But for everyday use, especially run and gun, the PD sound is very adequate in my opinion.

[Pete Wilie]

Originally Posted by Mike Rehmus

IIRC, Line In is inoperative in Camera mode. It only works in VCR mode.

Mike,

The "LINE" that I was referring to is the position on the "INPUT LEVEL" switch on the XLR input selection block on the left side of the camera. The choices are "LINE", "MIC", and "MIC ATT". See page 55 of the PD170 manual for details.

The manual states:

When connecting audio equipment
Set the +48 V switch to OFF and set the INPUT LEVEL selector to LINE.

So I'm pretty sure that this is for connecting input from a mixer with LINE output, and should definitely work in "Camera" mode.

My thought is that setting the "INPUT LEVEL" to "LINE" would bypass the PD170 preamp, hopefully eliminating some of the noise caused by the inferior camera circuits. If you then use a good mixer with a good preamp you should have better quality audio.

Has anyone does this?

[Mike Rehmus]

Sorry, I thought you were talking about the RCA connectors, not the XLRs. Actually, IIRC, the preamp is never switched out of the circuit. The line/mic switch is actually switching in an attenuator.

[Pete Wilie]

Originally Posted by Mike Rehmus

Actually, IIRC, the preamp is never switched out of the circuit. The line/mic switch is actually switching in an attenuator.

This doesn't make sense to me. According to Greg Winter, the PD150 and PD170 both use preamps. If you have a LINE LEVEL input, why would it need go to through a preamp?

The XLR "INPUT LEVEL" switch has 3 positions:
1. Line
2. Mic
3. Mic Att

The manual states:

When set to MIC ATT, you can reduce the volume by about +20 dB.

Why would Sony have a "Mic Att" and a "Mic" choice that does the same thing?

I thought that "LINE LEVEL" was a standard audio term that meant the audio level would be recorded without any further amplification. Please correct me if I am wrong.

[Mike Rehmus]

I understand the switch positions. Either Greg or someone else reported that the amp is never out of the circuit. Given where the switch is located and where the amp is, a three-level attenuator is entirely reasonable. Remember that no matter what the input level setup is, eventually it all has to be set to the level the Analog to Digital converter expects.

What 'Line level' means has nothing to do with what goes on inside the electronics. And Line level is, perhaps a term that is used as if it were a standard but it is a bit more tricky than that. Where 0 dB is placed is different on pro and amateur equipment.