Hi all,

I have been using an Aric Audio preamp to drive my Torii MK IV.  It is a good combination and both amplifiers use point to point wiring, good parts, simple circuits and VR tubes.  The preamp has a pair of 60s Bugle Boy 12AU7s and is nice and transparent.

I have never used a tube pre before this.  I have also never used a preamp with a gain control and a volume control. I noticed right away that the signal distorts if the gain is too high.  My approach has been to set the Torii's volume at around 80%. The volume control on the preamp is a motorized Alps.  That ends up at about 40% when I back off the gain so there is no audible distortion (to my ears).  

I have read plenty about riding the gain here. My summary is try higher input levels to the Decware amps and see if you like the sound better. I have little experience with setting gain on a pre however.  Is this similar to a bias control on amplifiers.  Higher gain = higher tube bias?  Should I aim for minimal gain on the pre?

What approach would you guys take? What should I listen for?

This isn't a big problem, the system sounds amazing, but I want to learn more.

-Karl

Gain riding/ structuring is a great tool to enhance the sound of your system.   It’s subjective on what sounds good to you based on your system.  In my system…I max out my DAC to 4V via the XLR’s into my ZBIT when I am using my Tori MKIV.  With my pair of Zen SE84C+ that are configured as mono’s, I dial back the ZBIT to 80%.  When the signal hits my CSP2+, I generally like to run that higher and my amps lower….but that sometimes depends on which preamp tubes I am running.

Like Lon says..you just have to play around with it until you find what sounds good to you.  Running the preamp high and the amp lower, and vice versa will give two different distinct sound signatures.  Good luck and happy experimenting!

Karl. Rereading your post, and "gain" and "volume" being a confusing area in audio circles it seems, potentiometers or attenuators often called "volume" but being gain adjusters too...it took me a minute to read your post more accurately. Now I am thinking you do have the Alps potentiometer and an output gain adjuster, and I think you are on the right track by adjusting the output gain down to avoid distortions.

Still, using a pre for sound tuning, it is all so interrelated, nothing in isolation, for me it is not easy to get a handle on all specifics that are affected by adjusting the Pre's input gain/voltage and what that does to the signal via tubes, caps, resistors, bias, etc... But we know it does have relatively predictable sonic effects... Then the trick is getting the most from the adjustments we have... aside from cables and vibration management, mainly tubes and gains in this case.

I am imagining with your setup that, beyond playing with gain riding the Pre and Amp gains (volumes) to optimize sound, it could be fun to play also with balancing the two pre gains for optimal signal sound before the amp. Beyond using the output gain to adjust distortions, it could be fun to gain ride the Pre gains independently, as well as riding the Pre and Amp gains to see what you hear.

Something like this. Since you like the sound you are getting, and have the Pre output gain set for minimal distortion, it would be interesting to play with gain riding the way Lon and Dom and I were thinking, referring to the gains as the "volume" controls of the Pre and Amp mainly. Maybe 1st set the Torii at 70% rather than 80, and turn up the Alps potentiometer on the Pre to get the same volume you had previously. Adding more Pre sound to the mix, see if that is a direction worth playing with. And if that is "better," maybe try the amp "volume" a little lower and the pre "volume" a little higher. Or the other way, depending on optimal sound for your average recordings.

The other thing I would like to play if I had your Pre output gain, is leave the amp at the setting your prefer from above, then, I suspect you will get more sonic tuning power in your Pre from turning the Alps voltage up and down, adjusting the signal as we have been talking about. But also, in your case, adjusting the Pre "volume" up too much might require turning the output gain down some to avoid distortion, and this could possibly give a better sonic effect...more input gain and less output gain, or visa versa will likely have a meaningful affect.

So I am thinking that creating a baseline by tuning the Pre "volume" range to be relatively narrow, and optimized for sound as it balances with the Torii "volume" will be a strong sonic tuning set... But you may get some more by optimizing the Pre output gain by riding it with your Pre's Alps gain. I suspect the output gain will have a sonic effect beyond distortion, guessing it must be adjusting the voltage of the signal before the amp, though sonically I imagine not as much effect as the input gain, the input gain working on all that collectively makes the Pre sound. But what would happen with the Pre input gain adjusted up, perhaps even notably, and the output down... maybe another nice tuning tool...

Sounds like a good plan. I always gain ride by ear, but a meter would be interesting. I guess most would adjust the output gain of your Pre for distortion, but you may find it can be lower, dissolving subtle distortion more while opening the sound some. Depends what you need, but wherever I have played with less voltage from an active pre stage it creates a more open, less concentrated sound for better or worse. So I agree... if it is noticeable, it depends if you like the sound with the output gain lower and compensated for elsewhere. I look forward to hearing your impressions.

Yes interesting, as it did make sense to me that by reducing output voltage you were able to reduce Torii distortion. I wonder if he described what his intentions were from a design perspective.

Been dealing with a similar issue, but with a UFO and a Maple Tree Audio pre (similar to the Aric). For me, I had a noisy signal that limited very much on my pre, I could barely open up the input levels without making the noise worse. Got past that with a Snubway cleaning up the signal. Now I can push the limits on the pre. Karl, maybe I missed it, but is your signal path good n clean?

Will, as always, your insights have given me some light in the tunnel. One thing I didn't see mentioned, speaker sensitivity. The Lores I'm using on this system are rated somewhere in mid to high 90's depending who you ask. While this plays well with the UFO, it also seems to add another layer to setup/playback...at least for me.

I'm typically using the UFO between 1/2 and wide open (better bass the higher I go), the pre inputs about 50% and use the Alps knob to set overall system volume. This is a moving target that highly depends on the quality of the recorded source.

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Will brings up a great point that I overlooked in my previous reply. In my ZRock2… I run a Amperex Holland Pinched Waist 7062 tube, which is a higher gain tube than the normal 12AU7.  For the longest time I enjoyed the higher gain tube in my system… Especially when playing vinyl. When it was time to replace the tube I went back to a really good NOS 12AU7 as a test. The clarity that the 12AU7 brought was quite enjoyable, especially when it came to Digital playback as compared to the 7062.

Edit….

This comes alongside another topic that has interested me in quite some time.  That is how the quality of the gain being produced in the signal chain coming from your outlet. While the  quality of the current coming from my wall is clean with a dedicated home run line and a PS Audio Soloist outlet, and a Monster Power Conditioner, I sometimes wonder how the added voltage coming out of the XLR‘s could be degraded a bit because of the internal component of my Schiit Bifrost DAC  that does not have a toroidal power supply, as other higher end DAC’s incorporate.  I only bring this up because we are talking about distortion and overdriving the components with too much gain.  Point being that if you are already starting off with dirty power so to speak at the wall…then the  gain being produced is going to be degraded and possibly affect the signal on the back end. Just wanted to point this out as some food for thought. Now I could be completely wrong and if I am somebody, please correct me.