8mm Forum: GS1200 Aux or Earphone Jack

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Topic: GS1200 Aux or Earphone Jack

Graham Ritchie
Film God

Posts: 4001
From: New Zealand
Registered: Feb 2006

posted December 29, 2008 01:07 AM

Picking up on another topic about connecting projectors to a external amp in my case a graphic equalizer in line as well, what do most GS1200 owners use and why? last week I started using the rear earphone jacks for the first time instead of the usual Aux out. There does seem to be more range of base and treble "more effective" of the sound leaving the projector for the external amplifier, considering the Aux output is coming of the projector pre-amp, what is it with the earphones jack "circuit wise" that improves the sound over the Aux out? I have in the past come across photos of GS1200s with an external amplifier connected to the earphone jacks, but never could figure the why [Roll Eyes]

.

Graham.

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted December 29, 2008 04:19 AM

The Aux output sockets come off a seperate circuit before the vol and tone controls. In fact its the same circuit which is used to drive the level meters. The oputput is therefore flat in its frequency response which is what you really need when using the machine with an external amplifier which will then have it's own tone controls.
The headphone/earphone outputs come off the output circuit at the same point as the speakers. This means that the signal is going via the internal vol and tone controls. Any adjustments made to these controls will then be heard via an external amp.
If for instance you turn the vol controls up too much you may hear distortion (clipping) via the external amp and the same would be true if you had the bass up too high.
Really the use of the various sockets is down to what you are feeding the signal into externally. If for instance you are feeding the signal into just an external power amp then it may be beneficial to come out of the earphone outputs so that you have some control of the sound quality by using the projectors controls. If you have a power amp with built in controls then come out via the aux sockets.

Hope that helps, Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Martin Jones
Phenomenal Film Handler

Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008

posted December 29, 2008 01:25 PM

Agreed Kevin,

The biggest advantage of Aux Out (Line Out) sockets is the fact that none of the additional noise due to the relatively low quality Power Amplifier in the machine will be in the output signals so won't be amplified by the external amplifier. But it's no good using a c---p external amplifier!!.
If going down this path the external amplifier must be of very good quality, low noise, low distortion, with a wide range of tone control. Preferably it should have much more power than you need so that it operates at a low volume setting.
And be very sure (this applies generally to other projectors, not the subject one) that the "AUX" output is a genuine low level "Line" output; some of the smaller Elmos' AUX Outputs are just an attentuated version of the EXT Speaker output, and many other machines are like that! Such outputs are of little use.

Martin

--------------------
Retired TV Service Engineer
Ongoing interest in Telecine....

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Graham Ritchie
Film God

Posts: 4001
From: New Zealand
Registered: Feb 2006

posted December 29, 2008 11:09 PM

Thanks Kevin and Martin

The amplifier I use is a Yamaha RX-V750 its very good, however I gave up using the Sub long ago with most of my Super8 films the "amplifier was not interested in giving me much base if any". The strange thing though was when I wired up the 35mm projector with its 70 year old mono sound head a few years ago, "now has reverse scanning red", the quality of the sound coming out of the Yamaha even in mono was incredible and the sub worked really well, the same goes for running DVD Dolby Digital 5:1 although all the projectors run at about the same volume level on the Yamaha, Super8 for some reason was missing out. I will try using the sub again and see it it works now the sound output is coming from the rear earphone sockets.

Graham.

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Graham Ritchie
Film God

Posts: 4001
From: New Zealand
Registered: Feb 2006

posted December 30, 2008 02:32 PM

Ran some film last night "Gone Nutty" was one, the sound was much better than using the AUX out, the sub was very responsive this time [Eek!]

other films including a Look at Life I found the dialogue clearer, setting the Yamaha to a set volume and using the projector controls for everything else has worked out really well, from now on its the earphone sockets [Smile]

.

Graham.

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