2. amps-preamps
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Low gain preamp options

I’ve read lots of preamp suggestion threads and discussions on amp matching. I don’t know what percentage of people have digital only systems, but it seems like there is a missing niche for preamps.

Most DACs have at least a 2V output which exceeds the input sensitivity of most amps. So unlike a phono input there isn’t a real need for gain in most cases. The problem with a passive preamp is some amps don’t have high enough input impedance. Also a preamp allows longer cable runs (if needed). Then there’s the whole tube warmth or tone that some people are so fond of in taming perceived digital harshness.

I’ve read about lots of tube preamps, but even the low gain ones are still in the 10dB range. It would be nice to have a useful amount of volume adjustment instead of silent to too loud with just a wiggle.

The only unit that comes to mind that’s even close is a Schiit Saga+, but it seems like even mid-fi systems should be able to do better. Don’t get me wrong, I’m using one now. It’s great for $400, but at some point it’s going to become the weak link in my system (if it isn’t already). 

List of desired features:
<6dB gain 
<500 ohm output impedance
tubed output
at least 2 sets of outputs
balanced in/out optional

Anything out there that fits the bill?

cat_doorman
oldhvymec
5,101 posts
 
I added a passive pre with a remote that was almost perfect for a guy. He would NOT give up his tricked out Fisher 500 pre. He couldn't get up to change the volume either.  The guy had it made for 4-500 dollars.. Silver traces and good pots.. I thought it was Dodd, wonderful work.. 20-25 years ago.. It lost nothing in SQ that I could hear.. La Scala will show noisy or bad equipment.. 100+ sensitive.. OH YEA..

Regards
cat_doorman OP
236 posts
 
A passive might work with the amps I have now, but I've been looking at some others that have input impedances in the 10k range. When running at full volume that may be fine but at lower volume I think it might cause issues. If I remember right poor impedance matching can get you some roll off on the low end which is where you would theoretically want to boost it to compensate for perceived roll off at lower volumes. (Fletcher-Munson) 
The other thing is I really like whatever the tube in the Saga+ is doing. I think I'd miss that. When I first got it I did a lot of comparing to my MF A300 integrated preout even going so far as to use it as a pre into the A300. I'll need to start paying attention to how much I actually use the volume control. Maybe I'd like even more tube sound even if it means having to put up with only a very small portion of usable adjustment. I really hope the eventual solution isn't to spend $10k+ on a vinyl rig and record collection.
russ69's avatar
russ69
3,360 posts
 
A pre-amp is very important for many reasons. As example for driving multiple amps such as bi-amping or mono blocks. Most of the problems come from high power amps with very efficient loudspeakers but you can always pad down the pre-amp's output but it's very hard to add gain you don't have.  
verdantaudio's avatar
verdantaudio
1,470 posts
 
So...I certain that I can have the gain customized on my Art Audio preamps.  The Conductor and Conductor Simply have adjustable gain.  The Conductor I had switched between 0dB and 25dB, the latter driven by gain for the headphone amp.  

Basically, depending on what you need explicitly, Art Audio can probably accommodate with one exception, the chassis is not large enough to support XLRs.

If you tell me what you want explicitly, I can get a quote and timing from Tom.  
georgehifi's avatar
georgehifi
10,312 posts
 
Most DACs have at least a 2V output which exceeds the input sensitivity of most amps.
So unlike a phono input there isn’t a real need for gain in most cases.
There’s many phono stages now that have 60db of gain, so no extra gain needed with them either.

The problem with a passive preamp is some amps don’t have high enough input impedance.
This is true, especially with Class-D, the industry standard was 47k or 50k input impedance for amps, but some Class-D’s are a silly 2kohm!! even 1kohm!!! input impedance, not good with passives and most tube preamps!!!.
You should have 1:10 ratio or more, output to input impedance, to be matched.
EG: If you have a 10k passive it will be at worst position 2.7k output impedance, the lowest amp input impedance "should" be 27kohm or higher, no damage will occur if it’s not, say 1:5 ratio or even 1:1 just cuts the volume down lower and becomes even more of a voltage divider.

Cheers George
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