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-   -   Can you have both LFE and High Level inputs at the same time? (http://forum.hsuresearch.com/showthread.php?t=96109)

glassetcher February 8th, 2019 10:24 AM

Can you have both LFE and High Level inputs at the same time?
 
My system is used for both HT and Stereo music listening. Subs include a VTF-2 mk5 and as STF-2. For stereo, the R/L and subs are powered by a PS Audio Stellar Gain Cell DAC/S300 amp combo, with the subs power coming off the high level outputs of the S300 and daisy chained together. That works fine for listening to stereo inputs such a phonograph, digital out from BR player for CDs, or USB directly from my iMac. For 7.2.4 HT, my Denon 4300 AVR handles all of the 8 surround and the center channel, with the PS Audio, via preouts from the Denon, handling the front L/R and subs with the subs connected as described above. With the subs connected like this I obviously lose LFE input and Audyssey control of the subs. Would it be possible to hook the subs up via the sub-outs from the Denon to the LFE input at the same time as the high level inputs are also connected, but have the subs only respond to the LFE input when the inputs are routed thru the Denon, such as for BR movies, and any other AV signal being handled by the Denon? I'm happy with the current setup, but it would sure be nice to get LFE/Audyssey control of the subs back for HT viewing.

Kevin_Hsu February 8th, 2019 3:21 PM

Hi there,

Possibly, but sometimes the LFE can still introduce a high impedance signal that may actually end up causing a large volume drop when you play your 2 channel setup. That can also be a bit messy in terms of material delivered from potentially two difference sources. My recommendation would be to run XLR from your Setllar Gain Cell preamp to your S300 (if you are not already). Then I would run the RCA preouts from your Stellar Gain Audio and the LFE (subwoofer) preouts from the Denon 4300 to a RCA switch box. From the RCA switch box, you can run that to the STF-2 and VTF-2 Mk5. That way you can select that source that you want to go to the sub. When you use your 2 channel stereo only setup, you also want to set the crossover to in on both subs as well. For HT, you can set them to out because the denon has a built in crossover for you.

glassetcher February 9th, 2019 9:12 AM

Quote:

Originally Posted by Kevin_Hsu (Post 137012)
Hi there,

Possibly, but sometimes the LFE can still introduce a high impedance signal that may actually end up causing a large volume drop when you play your 2 channel setup. That can also be a bit messy in terms of material delivered from potentially two difference sources. My recommendation would be to run XLR from your Setllar Gain Cell preamp to your S300 (if you are not already). Then I would run the RCA preouts from your Stellar Gain Audio and the LFE (subwoofer) preouts from the Denon 4300 to a RCA switch box. From the RCA switch box, you can run that to the STF-2 and VTF-2 Mk5. That way you can select that source that you want to go to the sub. When you use your 2 channel stereo only setup, you also want to set the crossover to in on both subs as well. For HT, you can set them to out because the denon has a built in crossover for you.

Kevin, thanks for getting back to me.
So, can the subs still process the LFE signal going from the RCA switch box into their high level inputs the same as if the LFE signal was going to the LFE input? What is the difference in the high level speaker signal and the LFE signal from the receiver?

Kevin_Hsu February 11th, 2019 1:52 PM

Quote:

Originally Posted by glassetcher (Post 137013)
Kevin, thanks for getting back to me.
So, can the subs still process the LFE signal going from the RCA switch box into their high level inputs the same as if the LFE signal was going to the LFE input? What is the difference in the high level speaker signal and the LFE signal from the receiver?

Basically in this method, the high level inputs on the subs will not be used. It will all be connected via RCA cables to the low level inputs on the subs. Generally speaking, it's always better to run from a preamp source than the amplifier outs. The reason being is that using the amp outs will add in an additional gain stage to it and if you play your material loud enough, the amp may easily be sent into distortion and will start to compress which will affect how clean and how linear the subs will be. Also usually for preamp/power amp separates, the power amp usually will clip before the preamp stage will.

glassetcher February 23rd, 2019 9:23 AM

Kevin, Paul McGowan of PS Audio recommends powering the subs from the amp rather from the preamp. Not that it can't be done from the preamp, but that is just his suggestion, especially if there would be long interconnects between the preamp and the subs, which I have. So, if I want to continue to connect to the high level inputs of the subs from the S300 amp instead of the preamp, and also direct the LFE sub-outs of the AVR to the high level inputs of the subs for HT listening via the RCA switch box, will the sub high level inputs handle an LFE signal properly?
Thanks,
John

Kevin_Hsu February 25th, 2019 11:09 AM

Hi there,

I'm not sure I agree fully with his stance that running from the power amp is better. Some do like running from the power amp in that they want the signal going to the sub bass to be given the same distortion/compression characteristics as their amp ("maintaining the sound quality"). However, the downside is that more distortion and compression is going to the sub so it technically won't be a clean reproduction of the bass signal from the source material. A good example would be the majority of tube amps. A good majority of tube amps out there do not handle deeper bass very well as they go through things like transformer saturation. As a result the signal in the low bass tends to have a good amount of compression and distortion so the sub bass will not sound as full and will sound strained due to that. The other part of the double long interconnects doesn't apply as you are using two separate preamp outs, one balanced and one unbalanced. So you don't have to worry about parallel capacitance. In terms of the length of the unbalanced run to the sub, long unbalanced interconnects don't affect the sub as much as it does your main speakers. With main speakers, most tend to recommend keeping the runs below 20ish feet or so due to capacitance and signal degradation at high freq. However since the sub is reproducing frequencies in the low sub bass, you would have to run hundreds of feet before those frequencies are affected.

If you run to both the high level and low level inputs on the sub, then your LFE might still work, but I feel that it still may cause some odd effects such as freq overlap as it would be receiving signal from two separate sources. You also need to engage the crossover on the sub for both 2ch and HT. If you want to connect it that way, then the best way is to get an RCA switcher to disconnect the signal from the LFE when you're playing 2 ch material, and get a speaker switcher to disconnect the speakers from the sub when you're playing HT.

glassetcher February 26th, 2019 7:07 AM

Kevin, here's my latest plan, which I think pretty well follows along with your last suggestion. I would connect the RCA outputs of the S300 amp to one of the RCA inputs on the switch box. Then, the RCA outs of the switch box would go the high level inputs of the subs, one channel to one sub, and the other to the other sub. The sub-outs of the Denon 4300, which would only be turned on for HT, would go directly to the LFE inputs on the subs. Thus, when I want to listen to stereo only, I would switch to the input on the switch box from the S300 amp, and for HT, switch the box to an unused input, thus cutting out the input from the S300, and turn on the Denon so the LFE sub-outs then input to the subs. This also lets me get back to Audessey control of the subs for HT. None of my speakers are connected thru the subs, so there is no problem there. In addition, the RCA box has a remote, so I can incorporate control into my Logitech Harmony Elite universal remote to switch the box to the proper input remotely. I'm getting the switch box Thurs and will hook up this scenario to see how works. :rolleyes:
Thanks for your input.
John

Kevin_Hsu February 26th, 2019 11:36 AM

Quote:

Originally Posted by glassetcher (Post 137020)
Kevin, here's my latest plan, which I think pretty well follows along with your last suggestion. I would connect the RCA outputs of the S300 amp to one of the RCA inputs on the switch box. Then, the RCA outs of the switch box would go the high level inputs of the subs, one channel to one sub, and the other to the other sub. The sub-outs of the Denon 4300, which would only be turned on for HT, would go directly to the LFE inputs on the subs. Thus, when I want to listen to stereo only, I would switch to the input on the switch box from the S300 amp, and for HT, switch the box to an unused input, thus cutting out the input from the S300, and turn on the Denon so the LFE sub-outs then input to the subs. This also lets me get back to Audessey control of the subs for HT. None of my speakers are connected thru the subs, so there is no problem there. In addition, the RCA box has a remote, so I can incorporate control into my Logitech Harmony Elite universal remote to switch the box to the proper input remotely. I'm getting the switch box Thurs and will hook up this scenario to see how works. :rolleyes:
Thanks for your input.
John

Hi John,

Let me correct that a bit. Basically, if you're running from your S300 amp to the sub (high level inputs), instead of your PS Audio Stellar Gain Cell Preamp/DAC to the sub (low level inputs), then you will need to run it to a speaker cable switch box instead. The RCA switch box is only used if you're running from your PS Audio Preamp/DAC to the subs. So when you're using your Denon HT system, then you switch the speaker cable switch box to an unused input, like you stated. The rest is OK to try. The only thing that you may need to consider is if your Denon AVR is sending some high impedance signal to the sub even if it's off. If that happens, then you will lose a lot of signal from your PS Audio 2 ch system. So what you can do is try your 2 ch setup with everything hooked up. Remove the RCA cable from the sub and see if the volume gets louder. If it does then my recommendation is to use your RCA switch box and connect the subs low level inputs to that. Like the speaker switch box, when you're using the 2 channel system, you will select an unused input on the RCA switch box.


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