Switching between built-in vs external amp on SR-120

[sailsong]

I have a SR-120 and a Conrad Johnson tube amp.  The SR-120 has built in amps for 7 channels and so far, it is a very clean sounding amp and great for home theater.  I'd like to use my CJ amp for 2 channel direct music listening.  I know I can use my pre-out in the SR-120 to connect my external amp.  So here is my question.  Is it possible to do this?

2 sets of speaker wires:
    Set 1 would connect SR-120 Left and Right to Left and Right Speakers
    Set 2 would connect CJ and go to the Left and Right Speakers

Connect SR-120 Preout Left and Right to CJ input left and right.

Now when I want to use the SR-120 amp L+R, I connect those to my speakers. 
When I want to use the CJ, I pull out the SR-120 speaker cables from my speakers and plug in my cables coming in from the CJ?

I know enough to NOT keep both sets of amp wires connected to the speakers at the same time.  If I do, I can probably kiss my CJ goodbye

My plan is to switch amps by simply switching Cable pairs but what I don't know is if connecting the pre out to the CJ effective shuts off the SR-120 L+R output.  Does anyone know?  I know I can probably experiment but I wanted to see if someone already knew.

Thanks!
    

[Porscheguy]

Well, I've used my SR-120 just as a preamp for a while as I waited for my XMC-1. Worked well and sounded great. Not sure if that helps.

[sailsong]

I thought I'd share what I discovered. The pre-outs on the SR-120 act like a line out splitter. If the Internal Amp is switched on, the speaker connects are always active. So if you have the pre-outs for the Front Left and Right going to an amp and the internal left and right and going to another set of speakers. Both sets of speakers will work. I don't mind this as offers more flexibility for me.

The more I play with the SR-120 the more I feel like it is a PT-7020 and a 7 channel amp all put in one shared chassis. You could completely turn it into a processor only if you switch off the internal amp. It is definitely neat

Does anyone have any detailed specs for the internal amplifier? What I am looking for is the class designation, the max output amperage, slew rates, and size of the transformer and capacitors.

[teaman]

I am quite happy with the power of my SR-120 and don't really hear any difference between the SR-120 and my PT7020C4 and XPA-5 set up. So sailsong, are you saying that with the pre outs to the two channel amp it essentially gives you 9.1 ability? If so, that is even cooler. Below is some info from a review.

Features

Decoding support for Dolby Digital, Dolby Digital EX, Dolby Digital Plus, Dolby Digital True HD, Dolby PLIIx, DTS, DTSES, DTS HD, DTS Master Audio, DTS Neo 6, SPDIF, PCM 8 channel , true processing up to 196kHz
Twin Cirrus® 32 bit dual core DSPs
Multi-channel Dolby Volume. Genesis/ST® Torino high performance scaling engine featuring a full implementation of the Faroudja DCDi image processing suite
Sherbourn, full color graphical OSD with adjustable transparency presented over live video, including HDMI
Front panel surround mode indicator lights
RS-232 two way communications for independent computer control
Sherbourn automatic multi-channel room correction and loudspeaker setup. Calibrated measurement microphone is included.
Quadruple bass manager with independently selectable high and low pass frequencies from 40 Hz – 250 Hz, in 5 or 10Hz increments.
The PT-7020A also utilizes a balanced output section. A balanced system minimizes noise that may enter the processor via external input cables. Especially in cases where very long lengths of cable are being used, balanced connections offer excellent induced noise rejection
Selectable 12db or 24db per octave high pass and low pass filters by channel groupings
Independent 11-band graphic EQ with global bass and treble controls by channel groupings Balanced subwoofer output
All legacy video inputs can be scaled and output over HDMI at up to 1080p 1080p/24 fps video support
Video pass-through mode with 12 bit compatibility
HDMI sources can be format converted to component video up to 1080i
HDMI 1.3a Deep Color compliant
Assignable inputs featuring input labeling, selectable decode modes, selectable triggers, etc. 0.5dB level trims on all channels
High voltage, low impedance main analog outputs for uncompromised dynamic headroom
1 – IR output (3.5mm mini)
1 – Microphone input (3.5mm stereo mini)
1 – USB data input (for software upgrades only)

Specifications

Rated power 125-watts x 3, 75-watts x 4 @ 8 ohms
175-watts x 3, 100-watts x 4 @ 4 ohms
With no more than 0.05% THD.
From 20 Hz – 20KHz all channels driven.
Power bandwidth 5Hz-150KHz
Gain 30dB
Signal to noise ratio 110 dB/ A weighted
Input impedance 40 K ohms
Sensitivity 1.1 volts
Dynamic headroom 1.3 dB
Power supply 120v/60Hz or 230v/50Hz (selectable)
Dimensions 17″ W x 14.5″ D x 7″ H
Carton weight 77 lbs.

[Gary Cook]

Class AB
LCR = 120 watts and others 75 watts into 8 ohms.
THD = less than 0.05%
SNR = 110 db
Gain = 30 db

Cheers
Gary

[sailsong]

Hi teaman,

No, that is not what I am saying. What I am saying is that the SR-120 seems to split the signal to amp section and the pre outs. So if you have a speaker connected to the Left and Right Speaker out and the left and right pre outs are connected to the an external amp and you have another set of speakers connected to that external amp then BOTH SETS OF SPEAKERS will play the same source material (probably at different volume levels to because of gain differences between the internal and external amps).

To do 9.1 like you are asking, you need to find a way to have those channels assigned to go out to the pre-outs and I don't think you can do that.

However, in the current situation, it is possible to bi-amp a speaker by connecting say the internal amp to the left and right speaker lows and then use the external amp (such as a tube amp) to connect to the left and right speaker highs. This is a passive bi-amp with some probable coloration because of gain differences between the two amps but the sonic characteristics could ultimately be pleasing to the ears. I am going to try this next to experiment

Lastly I should note that this behavior seems to be the same for all the pre-outs and their corresponding speaker connects.  I got the same behavior for the center and the left and right surrounds for example.

Feb 9, 2016 14:28:18 GMT -5 teaman said:

So sailsong, are you saying that with the pre outs to the two channel amp it essentially gives you 9.1 ability?

[teaman]

Feb 9, 2016 16:28:15 GMT -5 sailsong said:

Hi teaman,

No, that is not what I am saying. What I am saying is that the SR-120 seems to split the signal to amp section and the pre outs. So if you have a speaker connected to the Left and Right Speaker out and the left and right pre outs are connected to the an external amp and you have another set of speakers connected to that external amp then BOTH SETS OF SPEAKERS will play the same source material (probably at different volume levels to because of gain differences between the internal and external amps).

To do 9.1 like you are asking, you need to find a way to have those channels assigned to go out to the pre-outs and I don't think you can do that.

However, in the current situation, it is possible to bi-amp a speaker by connecting say the internal amp to the left and right speaker lows and then use the external amp (such as a tube amp) to connect to the left and right speaker highs. This is a passive bi-amp with some probable coloration because of gain differences between the two amps but the sonic characteristics could ultimately be pleasing to the ears. I am going to try this next to experiment

Lastly I should note that this behavior seems to be the same for all the pre-outs and their corresponding speaker connects.  I got the same behavior for the center and the left and right surrounds for example.

Feb 9, 2016 14:28:18 GMT -5 teaman said:

So sailsong, are you saying that with the pre outs to the two channel amp it essentially gives you 9.1 ability?

Yeah, I noticed after posting that was not what I was meaning to say. I was just making reference that you could make possible a front soundstage that offered two sets of front main speakers. I think that would sound good as long as it did not overwhelm your center. Having four front main speakers across the wall of your source could probably sound pretty cool. I understand it would not be decoded and processed for it's own distinct channels but still think it would fill the room with cool sound.

[sailsong]

Yeah, glad we are on the same page

I did actually try this and run the 4 speakers - 2 lefts and 2 rights at the same time, and you are right it is louder. You could use your room EQ to adjust it but in the end I would not recommend it. What I found is that it ruined the soundstage and imaging. Also because the speaker sets are different, the different timbres of the sets of speakers made the sound a little unpleasant - kinda smeared and there were noticeable changes in sound and quality as you moved around the room. So it definitely affected the off-axis response.

It might be possible to run 2 lefts and 2 rights with the right setup. For example if you had 4 identical speakers and the external amp was also an emotiva. then the timbers would all match and you could put one left upside down on top of the other left and do the same for the right and make up a d'appolito arrangement. That might sound good. But I don't have such a setup to try.

Anyway, I'm going to see if I can bi-amp my speakers and use my tube amp to power the highs and see how that sounds next. I got to get back to my family responsibilities first before I can play around again LOL!