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AUDIO FORUMS >> General Discussion and Support >> Ultra preamp (tube questions)
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Message started by Kurt on 03/14/15 at 10:14:06

Title: Ultra preamp (tube questions)
Post by Kurt on 03/14/15 at 10:14:06

I have my system set up for 2 channel and multi-channel (home theatre). I recently bought a set of Martin Logan Ethos and a McIntosh MC452. Most of the listening I do is 2 channel and I like using my powered subwoofer for 2 channel music. I currently have a Nuforce AVP-17 that I use to pass through the analog from an Oppo BDP-105. I'm interested in trying another preamp. I was recently made aware of Decware's Ultra preamp by someone on another forum.
The flexibility of the Ultra sounds very intriguing! I've never owned any tube gear. Has anyone here ever paired a tube preamp with a solid state amplifier? If so, did you like what you heard? I often hear of the 'smooth' nature of tubes. What exactly does that mean? Is it a rolling off of the upper frequencies?

Title: Re: Ultra preamp (tube questions)
Post by Lon on 03/14/15 at 12:41:16

Though I think in some cases there is a roll off of high frequency (vintage tube amps, some new ones modeled after vintage) you won't find this to be the case with Decware amps. You'll find a full-bodied tonal balance with solid imaging and a large sound-field, presented in a non-fatiguing way. This is "smooth" in Decware products.

I have used a tubed preamp in front of a solid state amp, several times with different components. This can indeed be a road to nice sound. Though personally I prefer tubed amplification as well, a tubed preamp can add to the sound of a solid state system. The Ultra will be a very flexible and very revealing tool for a surround system!

Title: Re: Ultra preamp (tube questions)
Post by jsm71 on 03/16/15 at 18:59:19

Kurt, I started with all solid state setup including a McIntosh preamp and amp. I wanted to add a tube preamp to make the sound more organic. It did and I was able to tailor the sound by trying different tubes. I highly recommend putting tubes somewhere in the chain. I was hooked enough to drive the rest of the way to all tubes today with a Cary SLP98P preamp mated to a Decware ZMA amp. I love this combination. The Decware Ultra preamp looks like a very flexible solution if you are juggling multiple channels.

One reality of mixing a tube preamp with a SS amp is that care should be taken with impedance to ensure the frequency curve doesn't roll off audibly at low and high extremes. A general rule of thumb is that the output impedance of the preamp should be at least 10 to 20 times less than the input impedance of the amp. You probably won't have any issue, but Mac amps all have somewhat lower input impedance ratings, which suggests you want to aim at preamps with lower output impedances to compensate. Your MC452 is rated at 22k ohms.

Give Steve a call and talk to him about your Mac amp. He likely is familiar with their specs and can comment on this matching issue. Tube amps, just as a point of comparison, all have input impedances of at least 100k ohms, some as high as 200k ohms. Any preamp will work with a tube amp.

Title: Re: Ultra preamp (tube questions)
Post by Steve Deckert on 03/16/15 at 20:22:19

Hi guys,

The Zen Ultra as well as the CSP3 (our two preamps) both have low enough output impedance and high enough gain to drive any amplifiers down to 10K input impedance so the MAC presents no issues.

Steve