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Author Topic: Photodiode / cell suggestions David Rigby Expert Film Handler Posts: 134 From: Chorlton, Manchester, UK Registered: May 2002 posted 08-04-2002 11:18 AM                     I'm going to have a bash at fitting a stereo cell to my Microcine portable. Currently it has a mono cell and mono integrated amp, but I'm hooking that up to a switch so I can switch the cell output to an external amp. While I'm at it I may as well fit an extra cell (especially since I can fit the new cells on ther reverse of the shaft and leave the current cell in place in case it all goes horribly wrong...) Anyone got any good tips for specific photo diodes to use? Just how bad would the noise be if I was to take the output from the projector via 1.5m of reasonable cable to an external amp - is it crucial that I shove a stereo preamp in projector? Would a standard phono preamp suffice in that case? Thanks for any advice folks! David  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-04-2002 11:22 AM                     A phono preamp will have a RIAA curve for eq so it will roll off a lot of highs worse than the academy curve also its input impedance is very high the cell would like to see a virtual ground or at least a very low impedance Also the cell must be close to the film plane to get any degree of seperation Microcine has stereo cells available  |  IP: Logged David Rigby Expert Film Handler Posts: 134 From: Chorlton, Manchester, UK Registered: May 2002 posted 08-04-2002 11:55 AM                     Thanks Gordon. I'm planning on rotating the shaft 180 degress, getting it ground flat to the same depth as the mono side and fitting the new cell(s) on there. The cells from Microcine seem somewhat expensive (aren't they like $300?) - although this includes the preamp. Have you seen the cells as supplied by Microcine first hand? It may be that the $300 includes the shaft and plate and a VERY good preamp... Thanks David  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 08-04-2002 02:46 PM                     Dolby has a raw stereo cell chip 33008 which as a list price of $75.00 / 47.77 GBP / 75.75 Euro if you are into building something. Richard Fowler TVP-Theatre & Video Products Inc. www.tvpmiami.com  |  IP: Logged Patrick de Groot Expert Film Handler Posts: 161 From: Sprang-Capelle, Netherlands Registered: Apr 2001 posted 08-04-2002 05:56 PM                     You can use some mic preamplifier to amplify the signal. I have succesfully used the following preamp: Vivanco MA 222. It has a variable impedance and two inputs/outputs L&R. Just go to www.vivanco.com and search for MA 222. You can also use a mixer, but then you need to pay attention to the input impedance (or hope for the best...). You should buy that vivanco and put the output signal to the mixer's cd input or directly to you're amplifier. The cable length isn't a real issue. Make you're own mic cable's.  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-04-2002 07:12 PM                        I would do it right and spring for the $300 upgrade. It will usually work better and in the end be well worth it. But after all, I just had payday. Josh  |  IP: Logged David Rigby Expert Film Handler Posts: 134 From: Chorlton, Manchester, UK Registered: May 2002 posted 08-08-2002 10:41 AM                     OK, so I've decided to cough up the dough and buy the Microcine parts (assuming that $300 gets what I need for the job...). With that in mind I need to run the output from the preamp to an external amp since the internal one is mono. There are situations though where I'll probably still want to use the internal amp, so I hooked the preamp output up to a switch so I could switch between internal and external amplification. Trouble is, though the internal amp sounds great (seems to have improved since I rewired the cell), if I route the output through a hi fi amp it sounds absolutely dreadful...what have I overlooked?! I recently bought a CP50 but I wouldn't expect that'd make any difference to a mono source - or am I wrong? Should it go via the CP50 to the amp? I'm still learning when it comes to setting up my sound - as you can probably tell!!! David  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-08-2002 10:53 AM                        Assuming that the kit comes with a new preamp, why are you trying to rewire the old one if it will be taken out anyway? That cp50 of yours should have a pair of cell preamps in it so you could run the cell leads to the CP50 and have better sound than anything homebrew ever would. just a though, Josh  |  IP: Logged David Rigby Expert Film Handler Posts: 134 From: Chorlton, Manchester, UK Registered: May 2002 posted 08-08-2002 11:37 AM                     I rewired the old cell when I figured that with the new one coming in at $300 it might be a little while before I get one! (...and it takes time to get stuff from Microcine ) Great tip about the CP50 - I hadn't realised it'd have a direct cell input. David  |  IP: Logged John Anastasio Master Film Handler Posts: 325 From: Trenton, NJ, USA Registered: Sep 2000 posted 08-08-2002 11:51 AM                        It sounds like you've wired the preamp output to another preamp input. Yup, that'll sound like hell, all right. The levels will just overload the preamp and it will clip like crazy. Only wire the preamp out to the input of a power amp.  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-08-2002 03:10 PM                        ah, IC well, in the mean time, you'll have a good sounding mono setup. We all started somewhere. Josh  |  IP: Logged David Rigby Expert Film Handler Posts: 134 From: Chorlton, Manchester, UK Registered: May 2002 posted 08-08-2002 06:01 PM                     John - odd thing is, it sounded distorted both through the the phono preamp direct from the cell and via the aux input from the projector preamp (but sounds great through the projector amp...). Oh well - now that I'm aware of the cell inputs on the CP50 I'll be using that instead (thanks Josh ) David  |  IP: Logged Rick Sanjurjo Film Handler Posts: 26 From: Omaha, NE, USA Registered: Jul 2002 posted 08-09-2002 08:02 AM                     David, It will sound funny through a phone preamp because it adds an equalization curve intended for use on records. An aux input is normally intended for line level signals that the solar cell is not, so that will also sound funny if it works at all. The cell inputs on the CP50 are the way to go. Rick  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 08-09-2002 10:43 AM                        You could use the phono input, but you would have to turn the bass down, as the RIAA curve emphasises the bottom end and cuts the treble. Josh ------------------ "Film is made of silver, video is made of rust" 'nuf said  |  IP: Logged

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