How to turn on Unity Gain on Pre Amp

Leedh Processing  and Lumin

Set your pre-amp to unity gain (refer to your amplifier's manual or ask the manufacturer about this - some have it labelled) and leave it there. Use LUMIN App volume to adjust your listening levels.

I tried the LEEDH processing in my Lumin streamer last night and I must say I was mightily impressed. If I didn’t have a TT, I would have no need for a preamp anymore. It’s that good.

70% volume is unity gain.

C2500 at 70% volume after passthrough

If it has a HT bypass just engage that. 

The best way to hear what the LEEDH processing is really doing is to bypass your preamp completely. Going forward, I intend to only use a preamp for my vinyl front end. Digital is going directly into the amp.

thanks for input all, i’ll check HT bypass. I am running dual subs so eliminating the pre is not a great option. at this point i’m wanting get the best test i can with the leedh with preamp in place and see what i hear. I can’t help it go down the rabbit hole a bit but the truth of the matter is I would prefer to maintain using my preamplifiers remote control as opposed to the iPad through the lumin app or roon app. if I like what I heard I can investigate the LUMIN remote but I’m not sure how that would integrate with and everything though?

Can't find HT bypass mentioned in the owner's manual. Is tone bypass the same thing? below is the section from the manual 

Tone Bypass Press the Front Panel Tone BYPASS Push-button to remove the C2500 Tone Circuitry from the signal path for the currently selected Input Source. The LED above the TONE BYPASS Push-button will illumi�nate. Refer to figure 50. The C2500 remembers for each selected Input whether the Tone Control Circuit�ry is deactivated. To reactivate the Tone Control for the currently selected Input Source press the TONE BYPASS Push-butto

Not the same thing....

Tone bypass is not HT bypass, its function is to deactivate tone control setting.

On the C2500, " Passthru " is HT bypass. To activate passthru, you need to sent a 12Volt single by an external source to the back panel "power control" "Pass-thru" jack via a 3.5mm stereo cable (see owner's manual page 4).

Once the "Passthru" function is activated, all front panel control knobs and buttons including volume control will be deactivated except the "output 1/2 buttoms" (see owner's manual page 25), and the volume level will be automatically set and lock into unity gain (70%?).

I misspoke on the subwoofer being one of the reasons why I need the preamp. It has been a while since I looked behind my gear and the REL subs are taped into the amp, only the grounds are on the preamp. So easily hooked up the Lumin direct taking the preamp out of the system and surprised to say it looks / sounds like a clear winner. Didn't want that to be the case as I love my tube preamp, paid a lot for it, and it has cool blue meters.... Still got some A/B testing to do, but I know my system and every audio adjective there is seems to be noticeably improved. Makes no sense to me??  I guess less is more.

So easily hooked up the Lumin direct taking the preamp out of the system and surprised to say it looks / sounds like a clear winner. Didn't want that to be the case as I love my tube preamp, paid a lot for it, and it has cool blue meters

Yeah, I worked for Magnolia for a short stint and they had the KEF Blades hooked up to Mac gear.  I’d heard the Blades at shows and they’re quite impressive.  Hooked up to tha Mac gear, it sounded mushy and slow and not at all like what I’d heard from the Blades at shows.  Bottom line, I think you’re hearing what I heard and that you’d prefer a more detailed and neutral sound.  But I also wouldn’t use the Lumin’s preamp.  Preamps are hugely important to a system’s sound and I’m sure you can find a better preamp than the one in the Lumin.  Look at brands like Pass Labs, Linear Tube Audio, Backert Labs, Audio Research, etc. and I think you’ll find Audio nirvana.   The Mac is veiled , cloudy, and obscures detail, which is obviously not the case using your Lumin preamp section.  Pretty blue meters aren’t worth un-involving sound, which I think is what you’ve now realized.  Hope this helps, and best of luck in your search. 

@soix 

The Lumin has no preamp. The LEEDH processor is a volume control only. And a damn good one. If a system is passive friendly, i.e. high efficiency speakers, high input impedance amp, robust source output, there's really not many preamps that can beat no preamp. But if you have a hard to drive SS amp with low input sensitivity, yes, you will need an active preamp. But even the best active preamp will not be needed in every system.

If a system is passive friendly, i.e. high efficiency speakers, high input impedance amp, robust source output, there’s really not many preamps that can beat no preamp.

I respectfully disagree. If it works out that way, fine. But many, many audiophiles find value in incorporating a quality preamp. I’d encourage @atmasphere to chime in here because, well, he’s a damn icon in this industry and a voice of reason here. IME, preamps are more consequential than amps, but yours is not my system or  my listening experience. My only message from personal experience, do NOT minimize the impact of the preamp on the ultimate sound of your system. FWIW.

I am only streaming so the preamp really only serves as a sound conditioner and volume control. I am a Mac fan and have auditioned other brands and settled on Mac. I do believe in my case that less is more vs some other preamp option. I wouldn't be surprised if some ultra-expensive preamp performed better than c2500 but I have no interest in going down that road. It sounded great with the c2500 and now seemingly better direct from the S1. Further listing tests on that is yet to be done.

While I don't have any experience with uber expensive preamps, I've had a few well respected ones. Here is one example.

I had in house three very good active preamps and one passive. CJ Premier 17LS, Art Audio VPL, Lamm LL2. The passive was a Sonic Euphoria autoformer preamp. To my ears the SE beat all three in every aspect in my system.

I have owned many transformer, autoformer, light dependent resistor, and resistor based passives. Many of these were better than preamps costing several time their retail price.

@soix you are right, to each his own.

OK I feel like a bit of an idiot..  just goes to show in the hi-fi world psychosomatic pre-expectations can be real.. I put the preamp back and it sounds every bit as good maybe even better than without.. crazy, I know i was convinced that it was better without it when I first took it out. i do have the leedh volume turned on but experimenting with the unity game at 70% on the preamp and going back-and-forth using the preamps volume not hearing much a difference either but the leedh is on the entire time which I think is a good thing.