Problem running my power amp through receiver.

T

Tday78

Audiophyte
Hey all. New to this forum, I have searched previous threads, found some instances that were close to mine but not exact, sorry if this may repeat. I have a AB precedent 600a, 1/4 inch jacks for the feed. I have a JVC 5456x receiver. Has preout/main in and scope out. I used scope out which allowed me to use the pre amp controls on the jvc. However, my amp attenuators would need to be full blast. My jvc volume control would then turn to the 12/1 o’clock position for the loudest setting. The same as if using the jvc onboard amps. What am I missing here? Seems I am only using half the amps power. Amp nice and Luke warm. Limiter lights are working &clip lights up past the 1oclock position. Pushing Cerwin Vega At-15s and Klipsch epic cf-3s.
 
P

PENG

Audioholic Slumlord
Hey all. New to this forum, I have searched previous threads, found some instances that were close to mine but not exact, sorry if this may repeat. I have a AB precedent 600a, 1/4 inch jacks for the feed. I have a JVC 5456x receiver. Has preout/main in and scope out. I used scope out which allowed me to use the pre amp controls on the jvc. However, my amp attenuators would need to be full blast. My jvc volume control would then turn to the 12/1 o’clock position for the loudest setting. The same as if using the jvc onboard amps. What am I missing here? Seems I am only using half the amps power. Amp nice and Luke warm. Limiter lights are working &clip lights up past the 1oclock position. Pushing Cerwin Vega At-15s and Klipsch epic cf-3s.
If your 5456X is actually the 4VR-5456X, then I don't think you can do much about it because it does not have pre outs, only scope outs.

The scope outs are for use with oscilloscopes so the output voltages will likely be too low for any power amp.

Found a photo here:
JVC 4VR-5456X Quad Receiver Photo #475559 - US Audio Mart

1642860418955.png
 
T

Tday78

Audiophyte
Thank you for the answer, I thought I could build a nice 2 channel stereo system, running four speakers, 2 left/ right off of the JVC and 2 speakers left/ right coming off of the power amp…. The 4vr 5456x sounds really good pushing 100 watts a channel in stereo.. too bad it has no preouts. Scratch that idea.
 
lovinthehd

lovinthehd

Audioholic Jedi
Two channel stereo systems use just two speakers; I'd pick the best pair and use them. 100 wpc may not be 270 wpc, but should do fine. You do have a quad capable unit there, which might be interesting for four speakers, tho.
 
T

Tday78

Audiophyte
Two channel stereo systems use just two speakers; I'd pick the best pair and use them. 100 wpc may not be 270 wpc, but should do fine. You do have a quad capable unit there, which might be interesting for four speakers, tho.
4 channel on that receiver, cuts the power significantly. Using 2 channel on the JVC bridges the four amps together into 2 channel. I have used 4 speakers together before with an external amp( pushing 2 speakers)and a receiver( pushing 2 other speakers) the receiver being in stereo 2 channel mode, with splendid high power results, was thinking scope outs should have carried the same signal as preouts. Surprised that it doesn’t.
 
T

Tday78

Audiophyte
If your 5456X is actually the 4VR-5456X, then I don't think you can do much about it because it does not have pre outs, only scope outs.

The scope outs are for use with oscilloscopes so the output voltages will likely be too low for any power amp.

Found a photo here:
JVC 4VR-5456X Quad Receiver Photo #475559 -
Preamp out voltage specs are can be viewed and measured using o scopes tho. Why would the scope out not match the voltage put out by the preamp?
 
TLS Guy

TLS Guy

Seriously, I have no life.
Preamp out voltage specs are can be viewed and measured using o scopes tho. Why would the scope out not match the voltage put out by the preamp?
I could, but I doubt it. The bigger issue is probably the output impedance. The only thing you can do is try it, and connect an amp to the scope outs.
Those old Hafler matrix based four channel receivers really were in a supreme junk class of their own.
 
P

PENG

Audioholic Slumlord
Preamp out voltage specs are can be viewed and measured using o scopes tho. Why would the scope out not match the voltage put out by the preamp?
You can certainly measure it to see if it can output at least 1 V into a 10 kOhm resistor and remain perfectly linear. Oscilloscope in those days typically would have input impedance of 1 MOhms or higher, so while the Scope out of those vintage receivers such as yours can drive scopes easily, they most likely were not designed to drive power amps that could have input impedance as low as 5 kOhm, though most should have more than 10 kOhm, up to may be 20 to 47 kOhms, but that would still be much too tough a load for the pre outs designed for scopes.

If the scope output can drive power amps, they would have called it pre out. Also, you have already tried, and if I understood right, you were not getting enough output. That pretty much confirm it cannot handle the load demand from the power amp.
 
T

Tday78

Audiophyte
I could, but I doubt it. The bigger issue is probably the output impedance. The only thing you can do is try it, and connect an amp to the scope outs.
Those old Hafler matrix based four channel receivers really were in a supreme junk class of their own.
Quadraphonic didn’t enhance your experience all that much?
 
lovinthehd

lovinthehd

Audioholic Jedi
4 channel on that receiver, cuts the power significantly. Using 2 channel on the JVC bridges the four amps together into 2 channel. I have used 4 speakers together before with an external amp( pushing 2 speakers)and a receiver( pushing 2 other speakers) the receiver being in stereo 2 channel mode, with splendid high power results, was thinking scope outs should have carried the same signal as preouts. Surprised that it doesn’t.
At first wasn't sure if it had four channels of amp or just the ability to add a processor/amp for quad. I'd still only use 2 speakers for a 2ch stereo signal myself, duplicating the speakers for more volume doesn't do much for me....altho I do still play quad audio material thru a surround avr as well as other multich sources. I don't see anything in the manual for an external amp tho. https://www.hifiengine.com/manual_library/jvc/4vr-5456.shtml.
 
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