Tube Noob - Setting Up MX151 Pass Through?
 

I am contemplating adding a 2-channel tube pre-amp to my system. This pre-amp will be dedicated to 2-channel music listening only.

I want to have my MX151 pass the signal through to the MC501 amps with no processing added by the MX151.

All 5.1 channel audio comes into the MX151 via optical cable.

My thoughts on the connection diagram are:

D100 (DAC) ===Bal XLR===> Tube Pre ===Bal XLR===> MX151 Bal In 1===Bal XLR===> MC501s

My current connection has the DAC feeding the MX151 Bal In 1. Would that be a conflict connecting the tube pre XLR outputs there? Or do I use the second set of balanced inputs on the MX151?

Do I need to do anything in the MX151 menu to keep it from touching the tube pre-amp signal in either scenario so that it works?

I'm probably not asking the right questions simply due to massive ignorance.

But your assistance will be greatly appreciated.

The idea is to have your 5.1 system and 2.0 system independent. Run all your 2ch sources into your tube preamp.

Run all your 5.1 sources into your 151. Blu-ray, dvd, AppleTV, cable box etc.

Take your L&R outputs of the 151, run them into the tube preamp. If the preamp offers passthru, it will have a dedicated set of inputs you need to set up for passthru mode.

When the 12V trigger from the 151 turns on, it triggers the preamp passthru mode. This will power up the preamp, go to the passthru input, it disables any source selection, volume control and tone controls of the tube preamp.

In essence it’s sending the front L and R signals from the 151 to “passthru” of the preamp to your 501 amplifiers. That way you can enjoy the 5.1 home theater surround easily with your 2.0 preamp in line, but the preamp not doing anything.

When you listen to stereo music, vinyls, streams, CD etc, all those sources go to the preamp and just the preamp is powered up, leaving the 151 off and not part of the system.

You would build your 2.0 system as you would without the theater, DAC, phono etc. Passthru allows you to send the theater front L&R through the 2.0 system without any affect on the signal. The preamp will say “passthru” on it when it’s engaged and all controls are disabled. It’s pretty seamless.

This is exactly how I have my system set up. Pre is C 1100. It all works flawlessly.

Tom,

Which setup were you referring to? Post #1 or Post #2?

I see what you are saying. So no changes to the MX151 are needed if I run the R/L main outputs from the MX151 to the tube pre.

That explanation does bring up a couple of questions in my mind:

1. So what if the tube pre has no power trigger input? It does come with a remote so I suppose I can trigger it on and off as part of my programmable remote function? I certainly don't want it powered On all the time.

2. So if I want to watch TV or a movie the tube pre-amp will be on in order to get sound with your connection suggestion, right?

The tube preamp needs to have a passthru trigger input. For example the C22 and C70 do not support passthru. The C2700 and C1100 do support it. They have a trigger input, unbalanced and balanced inputs dedicated to this feature and the necessary hardware to support this.

https://www.mcintoshlabs.com/-/media...dandrp-01.ashx

Sorry, I wasn’t clear. #2

When the preamp sees the passthru trigger it selects the correct input and sets the gain of the preamp to 0 dB.

You could do it without the passthru trigger input but it would not be nearly as convenient as you’d have to manually select the correct input and set the gain of the preamp to some known and repeatable value. If you have other family members using the system it is probably a non-starter.

Back end of the tube pre-amp:

https://www.schiit.com/public/upload...ack%201920.jpg

So if I can power up the tube unit separately, set the volume at a fixed level and since there's no issue with other family members using the system; can I not have the DAC feed the tube unit, then run the tube unit output to a MX151 balanced input and make it work that way?

Yes but that’s not what you want because the MX 151 digital processing would then be in circuit all the time.

You want to experience that tube magic unencumbered by another set of A/D and D/A converters.


Try this:
MX 151 front L , R outputs to Freya Input #1.
Freya Bal output to front L,R power amp inputs.

2 channel sources to remaining Freya inputs.

5.1 inputs to MX 151.

This way MX 151 is out of the loop on all 2-channel listening.

HT Passthru is then Freya input #1 and preset volume.

If this makes sense and you have power amps with meters I’ll explain how to set the Freya for 0 dB gain.