Who has moved to passive, and what'd you move FROM?

Hantra · « **on:** 21 Apr 2005, 02:09 am »

All:

Trying to consider whether I want to go with a passive volume control from a DAC, or get this ultra fabulous preamp I am auditioning right now.

People who's ears I respect more than mine say that passive is the way to go. But I have not heard a passive that wasn't beaten by a GOOD pre. I have heard many systems sound better with a passive, but the passive replaced preamps that were inferior to my ears.

I'd like to know who all has switched to passive and is happy. And what'd you replace?

Thanks,

B

Marbles · « **Reply #1 on:** 21 Apr 2005, 02:24 am »

The Bent replaced a nOrh ACA, Morrisom ELAD, and I demo'd many, many pre's in my system up to $7000.

I will say that the Stan Warren designed Superphon III is an active (buffered line stage with no gain) that has me thinking of going back in that direction if I can get it with an HT bypass and with a motorized volume pot...it uses a DACT so it can be done pretty easily.

Currently there are 5 beta units available for $1500 on Agon...

Red Dragon Audio · « **Reply #2 on:** 21 Apr 2005, 02:44 am »

The trick to getting a "passive preamp" (volume pot, gain control) to work is making sure that you follow a few very key rules:

1. Keep your interconnects as short as possible. If you can't keep them under a meter in length, then don't bother with one....unless your source puts out a healthy 3V plus or something...anyway...

2. Make sure the input impedance of your amp and the output impedance of the "passive preamp" are compatible.

3. Use a high quality stepped attenuator like those from DACT as they are very precise in their control of the volume between channels. Bent also has a very nice design with their multi tapped transformer based volume control.

4. If it is possible, try to integrated the volume control inside of your amplifier. This keeps the signal path after the volume control much shorter and will sound better overall.

5. If you are also able to, choose an amp with a more sensitive input; meaning it only needs 1V- 1.5V RMS to reach its maximum gain. Most amps need around 2V to reach their maximum gain.

I'm sure there are probably other considerations but those are some good guidelines to go by when choosing a "passive preamp".

MGDeWulf · « **Reply #3 on:** 21 Apr 2005, 03:06 am »

Hello Hantra:

My experience has been that the transformer based passive units are superior to the resistance based designs.

I am using the Sonic Euphoria, which uses an autoformer. Bent is also a great unit, but I'm not sure if they are producing units right now. There are others.

I've used many, many active units, including some in the $15,000+ range. And in my estimation, a $1,200 Euphoria is superior. The usual caveats for passives apply, except that due to the way an autoformer works, one can cheat a little regarding interconnect lengths, and the impedance match between passive and power amp is not nearly as critical.

Good listening,
Marty

Lak · « **Reply #4 on:** 21 Apr 2005, 02:50 pm »

I agree with MGDeWulf. I really like my Sonic Euphoria. There are custom options available also.

LordCloud · « **Reply #5 on:** 21 Apr 2005, 03:47 pm »

I am trying to get a passive to replace my tube preamp which sounds great itself. It's been a couple of weeks and my Django hasn't even shipped out yet, but when and if I ever get it I'll let you know what I think.

Jon L · « **Reply #6 on:** 21 Apr 2005, 04:29 pm »

Quote from: MGDeWulf

Hello Hantra:

My experience has been that the transformer based passive units are superior to the resistance based designs.

I am using the Sonic Euphoria, which uses an autoformer. Bent is also a great unit, but I'm not sure if they are producing units right now. There are others.

I've used many, many active units, including some in the $15,000+ range. And in my estimation, a $1,200 Euphoria is superior. The usual caveats for passives apply, except that due to the way an autoformer works, one c ...

Marty, have you used EVS Ultimate "nude" attentuators? Even though it's resistive passive, I prefer it far more than the usual resisitive passive in a box.

I've auditioned a silver TVC passive and SAS Labs 10A (which you know well), but I haven't had a autoformer-based one yet. What characteristic do you find most striking between Sonic Euphoria and something like 10A?

JeffB · « **Reply #7 on:** 21 Apr 2005, 04:46 pm »

Along with all the usual requirements for using a passive working effectively, I have wondered about one more possibility that I haven't really seen mentioned. It seems that they might work better with DACs that don't use op-amps, but something with more current drive. Or does the sources output impedance fully tell the current drive story? Anybody have any thoughts on this?

Tweaker · « **Reply #8 on:** 21 Apr 2005, 04:54 pm »

Years ago I used a Mod Squad Line Drive (still have it, in the closet) and was pretty happy with it until I got the upgrade bug and started auditioning vacuum tube pre's. Ended up with an Anthem Pre-1 which absolutely killed the Line Drive every way imaginable, particularily dynamics. I now have a Marsh P2000 transistor pre amp (which is very untransitory sounding). The Line Drive perhaps is not representative of some of the better passives, which I understand can be quite dynamic when following the guidelines heavystarch laid out. The Audio Advisor carries Marsh,if interested, and has a 30-day money back guarantee. They also have a balanced version and a tube hybrid.

Hantra · « **Reply #9 on:** 21 Apr 2005, 05:42 pm »

Quote from: Tweaker

Years ago I used a Mod Squad Line Drive (still have it, in the closet) and was pretty happy with it until I got the upgrade bug and started auditioning vacuum tube pre's. Ended up with an Anthem Pre-1 which absolutely killed the Line Drive every way imaginable

This is closer to my experience.

I have a McIntosh C2200 that I am auditioning and it's got to be the best piece of gear I have ever brought into my house. It's a big taste of the Nagra PL-P, which is the best I've heard.

Thanks for the info all. . .

srclose · « **Reply #10 on:** 21 Apr 2005, 06:00 pm »

I recently replaced a BAT VK5i and VK60 with the Sonic Euphoria and Dodd Audio 120W monoblocks. The SAS 10A preamp just came in for audition, but I haven't made any comparisons yet. The Sonic Euphoria doesn't seem to suffer from dynamic problems so far, you can still feel a kick in the chest from a bass drum impact.

SRC

Uptown Audio · « **Reply #11 on:** 21 Apr 2005, 07:06 pm »

Hantra,
I agree with your assessment of passive Vs active stages for the most part. I have tried loads of tube, ss, passive, buffered, balanced, SE, you name it and I always return to an active or buffered output linestage. The passive units do offer a more clear sound than cheap active units, but once you hear a few really good active units, the abilities and advantages are too great to ignore. The only issue is cost.
-Bill

zybar · « **Reply #12 on:** 21 Apr 2005, 07:26 pm »

Until I went with active room correction via the TacT RCS 2.2x, I hadn't found an active unit that bettered the BENT NOH passive preamp in my system.

Everytime somebody comes over and listens to "corrected" sound vs. non-corrected in my very well treated room, they always want to leave the correction on...

George

Tbadder1 · « **Reply #13 on:** 21 Apr 2005, 08:18 pm »

My experience with pre-amps is limited, but....here it goes

my $150 Luminous Audio passive beat out Bel Canto, Audio Research, BAT, Signature Sound, Parasound, PS Audio: all of these pre-amps cost between 1500 and 4000, new or used.

Tim Stinson from Luminous matches both your amp and Cd player and speakers to his passive. What comes out of my system has never been clearer and talk about a whomp. I'm very happy. And only tempted by other passives now. (Although as always I respect system synergy and what may be good for me is not for you)

peace, dudes

_scotty_ · « **Reply #14 on:** 21 Apr 2005, 09:15 pm »

I replaced a David Hafler DH 110 with a home brew passive and used it for seven years. I was weaned off of it by a custom non-negative feedback preamp with 7dB of gain from Stan Warren that I used until about 2years
ago when I built a more primitive version of the circuit that Marbles recently heard in the REV III, it hasn't lost a race yet. Obviously for me, passives don't cut it anymore. YMMV Scotty

Tweaker · « **Reply #15 on:** 21 Apr 2005, 09:53 pm »

The Luminous Audio passive looks very interesting, for the price especially.
http://www.luminousaudio.com/axiom.html

gonefishin · « **Reply #16 on:** 22 Apr 2005, 03:41 am »

Before I joined the Bent Audio fan club I owned, and enjoyed, a Joule-Electra tubed pre amp. Before the NOH I had been more than happy with the Joules performance. But the NOH is such a solid performer that I've found it's difficult to beat.

Unfortunately...due to some amplifier changes (higher gain) and having some high E horns...the Bent just doesn't cover enough low range for me with the new amps. The lowest volume setting is a bit too loud for quiet listening. If it wasn't for this...I wouldn't be looking for a new option and wouldn't feel a need. I'm possibly looking into a DEQX-p unit. Who knows. But I'll be sorry to have it out of my system

good luck with your search

dan

Occam · « **Reply #17 on:** 22 Apr 2005, 04:17 am »

Gone,

Have you considered adding a switchable pad to the noh chain? Something to to take 10-20 db of gain out of the chain. If your components are single ended a T-pad, and if balanced a H-pad will do the trick. Both of these allow you to specify both its input and ouput impedances as well as the attenuation.
http://beradio.com/notebook/passive_attenuators/

I'm assuming you are passively bi-amping and simply feeding your amps in parallel., which allows you to calculate the combined input impedance.
As I believe a transformer based attenuator might have a variable input and output impedance, I'd suggest you contact noh or the actual transformer's manufacturer, S&B?, for advice as how best to do this.
As to what extent the addition of resistors would do to your subjective perceptions while listening in 'padded mode', dunno.