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OC-150 with headphones


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#1 avraham

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Posted 24 August 2005 - 02:09 PM

I have a Crown OC-150 that I am using to help drive headphones with a small amplifier.  The amplifier I am using is a Parasound Zamp Zone, about 35 watts per side @ 8 ohms.  The amplifier's inputs are connected to the outputs of a preamp and the amplifier's outputs are connected to the amp 2 inputs of the OC-150.  I have my headphones connected to either of the two headphone connections on the front panel of the OC-150.  If I understand the OC-150 manual, using this hookup I should now have my headphones being powered directly by the amplifier.  This should be the same as using a headphone amplifier.  Is this assumption correct?

#2 avraham

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Posted 26 August 2005 - 10:49 AM

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#3 DGlass

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Posted 26 August 2005 - 05:11 PM

QUOTE(avraham @ Aug 26 2005, 10:49 AM)
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Let me look over the OC-150 manual when I am back in the office on Monday and get back with you as it has been discontinued for a very long time. smile.gif

My apologies for our delay in getting to your question I have been out of the office most of this week and with my absence Tech Support has been short handed. Participation on the forum by Crown staff is offered as a supplement to Crown telephone and email technical support. Most questions for Crown staff posted on the forum are answered with a reply post within 1 to 2 business days, sooner when possible. Crown makes no guarantee as to when questions will be answered via the forum by Crown staff.

#4 Artie

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Posted 30 August 2005 - 08:27 PM

For what its worth, since the OC-150 has headphone jacks on it, and it was designed to be directly connected to an amplifiers output, it probably has current limiting resistors added to the headphone jacks. You would never want to connect headphones directly to a 35 watt output. Thats several hundred times too much power. If an output transistor were to short . . . its taking your eardrums with it.   ohmy.gif

Typically, even hard to drive headphones only require milliwatts to drive.  Hope this helps.

Artie

#5 DGlass

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Posted 31 August 2005 - 12:48 PM

For those of you who are wondering "what is an OC-150?" blink.gif
It was an Output Controller designed for speaker switching and output metering in home audio applications many.... many..... years ago.

I have located a manual for an OC-150A and will try to get it scanned and posted on our website next week. Besides a few small changes in the circuitry and the buttons being square on the OC150 and round on the OC-150A they were basically the same.

According to the manual the headphone jacks are driven directly from the Amp 2 input. This means you would need to use a separate amplifier for the headphones and yes there was an attenuator switch on the back for the headphones to help protect your ears.

The output terminals for Speaker sets 1 and 2 were both driven from the Amp 1 input with separate on off front panel buttons.

Amp Input 2 could be hard jumpered to Amp Input 1 for monitoring of the main amplifier if a second amp wasnít being used. However, even with the attenuator engaged CAUTION was need when using headphones and speakers together with one amp.

#6 6502dude

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Posted 31 August 2005 - 03:39 PM

I have a product datasheet (marketing material) for this unit in my collection of old hi-fi info. It dates back to about 1976 era smile.gif

#7 avraham

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Posted 31 August 2005 - 05:07 PM

Thanks, this information supports my understanding of the manual.  Yes although this unit was built many many years ago, it still works perfectly.  It is a Crown after all.  I have two D-150A Series II amplifiers, one D-60 amplifier, one IC-150A and the OC-150.

#8 DGlass

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Posted 10 November 2005 - 05:15 PM

I have got both the OC-150 and OC-150A manuals scanned in and to our website manager. Check back later next week on the Discontinued Line-Level products web page.   smile.gif