Are Pre-Amps necessary?

@vanson1 My Benchmark HPA4  preamp improved the sound of my Benchmark DAC3 HGC. This DAC has a volume control for DAC direct to amp. The preamp improved on the DAC direct to amp on low level volume listening. I used to do a lot of that late at night when the baby was sleeping.  You could hear all of the music at low volume with the preamp. Without the preamp there was music missing at the low volume. A rather frustrating listen. 

I have another preamp that is very interesting for those that want a straight wire with gain. It is the Topping pre90 for about $700. Unfortunately it is incompatible with my current office amp but if it matched I would keep it and sell a 10x more expensive preamp. The only amp that I got it to match was the Benchmark AHB2 amp. However, other people have had more success than me matching amps to that preamp. So if you have a lot of sources, for relatively low cost, you can try this invisible preamp to see if a preamp makes a positive difference. 

I have Room Correction via ROON Core Convolution files. No need for that in a preamp with a fixed and weak processor. So I have s computer to do the number crunching for DSP. I am not using DSP at the moment but it served me well in the past.

Yep.  All you need is a straight wire with gain and a potentiometer.  Amazing that no one figured this out sooner.

This has been covered here on Audiogon many times before, again; it depends on the system.

No surprise the Benchmark pre elevated your system's performance.    I have had a few DACs with volume and always thought a good preamp was the heart of a great sounding system

Very shortly I will be receiving a new amp,  it has two inputs which will allow me to A/B two sources...  or two preamps or a source direct vs preamp...  I will give direct connection another shot but I think it will still sound better with preamp in the chain.....

^ This will only inform you as to how it works in your system(s).  Not necessarily as a general rule.

 Ideally you’ll have a DAC with extra available bits for volume attenuation, with a voltage output that matches the input sensitivity of your amplifier(s) for full output. Such a combination will allow for full power output capability of the amp(s) and full range of the volume control without the risk of bit stripping from the DAC. Appropriate interconnects are also needed.