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It is currently 16 Jun 2019, 06:49

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 Post subject: RCA console pull newbie
PostPosted: 27 Jan 2019, 21:45 
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Joined: 27 Jan 2019, 21:37
Posts: 1
Hi

I got an amp pulled from an RCA console. It had a pre/tuner chassis and power amp chassis. it has 2 umbilicals 1 for power and 1 for signal from the pre/tuner to the power amp. I thought this is great, looked simple enough. I have a few questions.

1. I was able to change the power switch and the power amp does power on - lights on the 2 el84s and the 6FQ7. My question is so that I am not using the pre/tuner how to I terminated the power wires to the pre/tuner. Do I just leave them not connected?

2. I connected the power amp to an iphone headphone out (I dont have a stand alone pre) and with the volume turned all the way full very low output is coming out. The speakers are old philips around 90 db sensitivity. What am I missing here?

3. Also, can somebody comment on what circuitry I have? power output? I dont think it could possibly be any simpler that this, Theres not much in the chassis.

I am attaching schematics.


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PostPosted: 09 Apr 2019, 10:09 
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Joined: 26 Oct 2012, 21:00
Posts: 200
Location: ontario canada
straight into the power amp? it's a high impedance input, use the "TAPE" in jack that will put your signal through the preamp giving you full use of the tone controls and volume....and make sure you remember to turn the volume down first...you don't want to hurt those vintage Phillips drivers!


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PostPosted: 09 Apr 2019, 10:20 
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Joined: 26 Oct 2012, 21:00
Posts: 200
Location: ontario canada
sorry thought occurred to me if your looking to eliminate the preamp section you could try a matching transformer.


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PostPosted: 18 Apr 2019, 16:22 
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Joined: 19 Oct 2018, 15:30
Posts: 117
Location: Montréal, Québec
Looks like a really simple 2 valve single ended power amp. I’m pretty shure that it could be modified to work as a stand-alone unit, but it may become complicated quite quickly. I’ll let the experienced members comment about that subject.


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PostPosted: 19 Apr 2019, 12:05 
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Joined: 05 Aug 2016, 14:35
Posts: 227
If you want to drive that power-amp as a stand-alone device:

Purchase the correct Molex Connector for the amp input. Center is ground. Right is right, left is left.
Purchase a FEMALE Stereo RCA cable.
Strip one end, both shells to the center lead of the Molex connector.
Red center conductor to the Right Side.
Black (or other) to the Left Side.

What plugs into the RCA jack will need to be a line-level device, 0 - 2 V of output. So a tuner, pre-amp out, or similar. And it MUST have a volume control.

Going down-hill with a tail-wind on a good day, you might get about 6 watts, continuous out of one EL84/6BQ4. Should be well-enough to drive high-impedance phones, but make sure you have (at least) a 100-ohm, 2-watt resistor in series with each channel out (for headphones).


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