I need an Audio Detective

What do you mean it crushed the signal on the tuner?

No clue really because I don't know what your preamp/amp/receiver/controller is. Most likely is that the control unit is switching inputs when it detects the DAC. That is often something that can be turned off. 

I was playing music with a strong 9 on signal strength meter and no multipath. Cut DAC on and signal goes to around 3 and just noise like between channels. Cut DAC off signal is restored to a 9 and music comes back on clear as a bell. That’s what I was referring to with crushing the signal

Preamp is a Mcintosh C1100

How close is your DAC to your tuner?  Are you running balanced between the tuner and the preamp? Where is your antenna located?

Sounds like RF interference. 

I want to point out though that this isn't much of a problem unless you like to keep your gear warmed up.  Distance, shielded interconnects and shielded power cables are the usual solutions.

DAC and Magnum Dynalab are about a foot apart, both plugged into a PS Audio P12. The second tuner that I had the same thing happen is 4 feet away and is on a Furman power conditioner. Balanced on both Magnum and DAC unbalanced or second tuner which is a Mcintosh MR71

Erik you are right it really isn’t a problem because I don’t keep the DAC on but you will have to admit this is a head scratcher

@jr96aolcom

Is this the first time this has ever happened when both units were powered up, and you were listening to the tuner? Or have you never had a reason to power up the DAC before, when listening to your tuner?

It sounds like the DAC is emitting some RFI which is getting into the tuner circuitry. The question is, how is the DAC emitting this RFI; via audio interconnects, or AC cable? Is the RFI energy entering the tuner circuitry by each chassis being so close together? 

If I really want low noise FM reception, I have to turn off all LED lighting in my house. Most LED lighting and dimmers emit RFI which reaches into the FM and AM bands.

Antenna is on the roof. I have 4 tuners with a quick disconnect I have set up so I don’t weaken my signal by having all 4 on a splitter. I only have 1 at a time. I am beginning to believe it is an RF issue being picked up by cabling. I am going to try this with my other 2 tuners tonight to see if the same thing happens

Coop. Yes first time and quite by accident 

I hate spell check dpop 

Try a different antenna.

@jr96aolcom

This is one of those situations that will drive many audio-enthusiasts crazy. It really depends on how much work you want to put into this. You could simply keep the DAC off (along with all LED lighting) while listening to your tuners. That would be the easiest solution here.

Or, you could unplug all audio interconnect cables from the DAC (with the unit powered ON), and see if that makes a difference, and report back your findings. It’s very possible you *might* be able to reduce this RFI using ferrite on some of the DAC cables (which ones will need to be determined). One tuner (the Magnum) might be more sensitive to this RFI vs your other tuners.

Hmmm, an audio-enthusiast that still values OTA (over the air) FM listening. I'm impressed. 

Love my tuners got into in a big way a few years ago

Magnum Dynalab MD108t SE

Mcintosh MR71 fully restoted

Mcintosh MR 78 with RM mods

Tandberg 3001 A

@jr96aolcom

For over 25 years I was Chief Engineer of a number of both FM and AM radio stations. I was always on the hunt for a tuner that provided to me at home (to monitor the audio quality of the FM station’s I engineered) the same performance of our station’s modulation monitors (which sample RF directly from the station’s transmitter output - no multipath of any sort is introduced). I found that one day in the Yamaha T-85 (I also owned a MR 78 at one point in time). If you’ve never tried one...

I was actually able to confirm the audio performance of the T-85 by installing a few (at different transmitter sites), and hooking them up to an A-B audio switch (A being the station’s modulation monitors, and B being the T-85). With audio levels matched, I could easily switch back and forth between the two, and the T-85 always sounded almost exactly like the modulation monitors. Just in case you were interested.

One last thing; for outdoor FM antenna reception, many times I used lower loss Belden 9292 (RG-11) over various RG-6 cables. It’s harder to terminate (as RG-11 connectors require a special crimping tool), but can help with fringe reception.

Belden 9292

@erik_squires 

Erik has it right, disregard my first post.

I don’t keep the DAC on but you will have to admit this is a head scratcher

Um, no it isn't!!

Anything with a computer or DAC generates some RF.  Your particular situation is just more noisy than others.   I'm not sure why this is a puzzle, really. What's probably happening is that the RF from the DAC is broadly across the channels you are trying to tune, and it's lowering the quality of the signal lock.

Follow up all 4 of my tuners are behaving in the same way and the other two are on the left side of preamp nowhere near the DAC and it’s interconnects or power cable. The interconnects only get close where they connect to preamp. Thanks for all your thoughts. Like I said not really a problem I don,t leave DAC on but the curiosity factor was quite interesting 

erik_squires

Sounds like RF interference. 

I want to point out though that this isn't much of a problem unless you like to keep your gear warmed up.  Distance, shielded interconnects and shielded power cables are the usual solutions.

Awhile back I read a lot of claims that equipment sounds best when left permanently powered on. 

Could it be the opposite is true and powering off after each listening session and then powering on 30 minutes before the next is the best option?
 

 If I may ask,

Denafrips recommends you leave your DAC on all the time. Why do you turn it off?

I have the ddc Gaia hooked up to the Denafrips and it is always on. The units are behind glass doors(open completely in the back) and I cut it off for heat reasons. I have left on for weeks at a time and cut it off I cannot tell any sonic difference either way. 

Hello jr96aolcom. It is possible your two devices share a code your remote control is sending. Put a piece of opaque tape over one of the two units and see what happens. If not successful, put the tape on the other unit and try again. No improvement? At least it cost nothing to try. Good luck.

 I have worked in Audio stores for almost 50 years and only encountered a similar situation once.  Guy had bought a Fisher HiFi VHS machine and brought it back saying it didn’t work.  We hooked it up and it was fine. 2nd unit, same result.  I went to his apartment in Boston’s South End to see what was going on, and sure enough the thing had no output at all, plugged into the same amp input as his CD player, which played fine.  Cables were checked.  Finally occurred to me we were located a block from the Prudential Tower, where a lot of broadcast antennae are located.  I switched him up to an NEC deck, and all was well!  RFI was the culprit, and the NEC had effective shielding, where the Fisher didn’t.  This was after Fisher was bought by Sanyo, 

Whether gear sounds better left on or not is very much dependent on the gear. My Luxman sounds great even after a minimal warmup. My previous Class D amps needed 2-4 days to sound their best again.

If you don’t hear any benefit to leaving your DAC off, I don’t understand the problem. It may be worth trying a different AC circuit though, if that fixes your problem the noise is being transmitted through AC and a Furman with LiFT and SMP will fix you right up.

Try a few RF Chokes on the digital cables coming and going from the DAC.

https://www.amazon.com/rf-choke/s?k=rf+choke

So it's confirmed the DAC is emitting RFI garbage. I wonder if that RFI is permeating any other audio gear (besides the tuners) when it's ON, to the point it's having an effect on noise floors.