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Old 12th October 2012, 01:01 PM   #31
DrDyna is online now DrDyna  United States
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I'm going to resurrect this thread because I'm planning on trying something similar, but I wanted to run it past everyone, just in case.

I have a 7 channel Onkyo receiver and I'd like to experiment with some EQ on my center channel, but unfortunately, it lacks pre-outs.

What I'm planning to do is use a basic L-Pad of resistors to convert the output to line level, so I can connect this to an external DSP and amplifier, but this resistance would be all that's across the output of the center channel, something like 10k ohm.

Anyone think this would make the receiver grumpy?
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Old 12th October 2012, 02:06 PM   #32
AndrewT is offline AndrewT  Scotland
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you should be able to intercept the INPUT to the power amplifier of the centre channel.

Feed that into a 100k Rin buffer and you have a good output that can drive a cable.
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Old 12th October 2012, 05:06 PM   #33
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Quote:
Originally Posted by DrDyna View Post
I'm going to resurrect this thread because I'm planning on trying something similar, but I wanted to run it past everyone, just in case.

I have a 7 channel Onkyo receiver and I'd like to experiment with some EQ on my center channel, but unfortunately, it lacks pre-outs.

What I'm planning to do is use a basic L-Pad of resistors to convert the output to line level, so I can connect this to an external DSP and amplifier, but this resistance would be all that's across the output of the center channel, something like 10k ohm.

Anyone think this would make the receiver grumpy?
I would not expect it. The SS amps I know run the headphones off the power amp through series resistance or voltage divider and work perfectly with speakers disconnected. OK, resistance is a little lower than 10k, but I don't think that makes much difference.

I must say that I like AndrewT's idea of intercepting the signal where VAS and power amp (CAS?) interconnect, though.
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Old 12th October 2012, 05:32 PM   #34
DrDyna is online now DrDyna  United States
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Quote:
Originally Posted by jitter View Post

I must say that I like AndrewT's idea of intercepting the signal where VAS and power amp (CAS?) interconnect, though.
Agreed, that would be ideal. There's enough room on the back to have 2 rows of 8 rca jacks for pre out, amp in that could be jumpered or not, but I think that would require some fairly hefty surgery on the receiver.

I'm not against trying I suppose, maybe I'll pull the top off in the next couple of days and see, perhaps I'll get lucky and the power amp board is connected to the rest of it with cables that can be easily tapped.
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Old 13th October 2012, 05:52 AM   #35
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Which model is it? Perhaps we can find a service manual and have a look too...
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Old 13th October 2012, 09:30 AM   #36
AndrewT is offline AndrewT  Scotland
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intercept at
Quote:
the INPUT to the power amplifier
not surgery
Quote:
intercepting the signal where VAS and power amp (CAS?) interconnect,
inside the guts of the power amp.
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Old 13th October 2012, 10:40 AM   #37
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A question just arose. Wouldn't a DSP in the centre channel only create a delay with respect to the other channels?
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Old 13th October 2012, 10:45 AM   #38
AndrewT is offline AndrewT  Scotland
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DSPs are being adopted and recommended for everything these days.

I am a digital ignoramus, but couldn't we use the dsp to create a negative delay? They allegedly can do everything else.
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Old 13th October 2012, 11:13 AM   #39
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You'd be a trillionaire with such a DSP because you'd have to go back in time DSPs generally queue up the sound in order to process it properly considering the time domain, then perform their 'trick' and make sure the result is aligned time-wise before it goes into the DA converter. Only if all channels are delayed by inserting a digital time buffer, you could achieve negative delay for one by extending the delay for others. It's all about relativity, even time-wise.
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Old 13th October 2012, 12:10 PM   #40
DrDyna is online now DrDyna  United States
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Quote:
Originally Posted by MagicBox View Post
You'd be a trillionaire with such a DSP because you'd have to go back in time DSPs generally queue up the sound in order to process it properly considering the time domain, then perform their 'trick' and make sure the result is aligned time-wise before it goes into the DA converter. Only if all channels are delayed by inserting a digital time buffer, you could achieve negative delay for one by extending the delay for others. It's all about relativity, even time-wise.
The MiniDSP I'm planning to use has ~1.5ms delay. I can counteract that by changing the "distance" setting in the AVR higher by 2 feet and moving them around a tiny bit, or just re-running Audyssey and letting it re-adjust the speaker delay, which is what I did to get my subs (which also go through the MiniDSP) back in phase/time.

Quote:
intercept at

the INPUT to the power amplifier
not surgery
I think you've misunderstood what I have to work with. I've got an AVR (Onkyo TX-NR609) which gets signal from HDMI and has only speaker level outputs. My plan was to use a pair of resistors to pad down the speaker output (because there's no other output) to line level, run it into one of my MiniDSP's unused channels, do a little processing and then feed it into an external amplifier.

If the AVR had pre outs, this would be a non issue, but what I'm planning to do would mean that the center channel section of the amp in the AVR is only seeing ~2k ohm rather than the 6 ohm center channel speaker it has on it's outputs now.
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