Passive Pre-Amp Experiences?

[BayStBroker]

The case for a passive pre-amp that switches and attenuates but does not add gain makes complete sense to me in theory. In practice, it doesn't sound right. But why? The standard practice is for a pre-amp to receive a signal, add gain, and then throttle the signal right away before sending it to the power amp for additional gain. It makes no sense. The signal should be richer and more authentic without a redundant amplification / attenuation loop.

My working hypothesis is that since music is mixed by sound engineers to be played back on typical consumer audio systems that include preamps, the mix sounds wrong on systems that bypass the pre-amp gain stage (using a passive volume control, for instance). On my system, without pre-amp gain, the musical image sounds flat, lacking in energy or vitality.

Can anyone cast further light on this conundrum?

[harri]

It may be power amp input impedance, your cable capasitance. Do your cd/dac has enough voltage/current capability?
You should try TVC-passive (transformer volume control) It should work much better.

[joeinid]

Welcome to the forum harri, thank you for joining.

[Jack]

From my experience the exception to the rule is the W4S STP-SE. No loss of energy or soundstage depth or width.

[audioholic]

This is a very interesting threat. I don't have enough experience to get to conclusions with Passive Pre-Amps, only one: The Music First Audio Reference Preamp. It made a sense to me at the time that by eliminating "unnecessary" circuitry and AC/DC current would obtain a more purer and natural sound. However, no matter what I tried with IC's, PC's, speaker placement, etc. I always returned (in that time) to my Convergent Audio Technology SL1 Legend tube preamp.

More recently I've experimented another approach, following "feature claims" from Digital Gear Manufacturers of driving amps directly from a CD Player or DAC with analog or digital volume control. I think I've tried with very decent components such as Burmester 089, Nagra HD DAC, Berkeley Alpha Reference, and most recently Bricasti M1 Special Edition. The same result to my ears/taste: I always end returning and preferring by a significant margin to connect those digital components to my Beloved Absolare Altius Preamp and or Jeff Rowland Corus. The sound is more organic, controlled, coherent and natural with a much better soundstage, detail, tone, timbre and harmonic textures.

I'm not a technical guy, I never tried to be, so don't have an technical explanation. I would love to hear from some good Audio Engineer or Honest Preamp Designer what is happening here but from the comments I've heard from other audiophile friends, it seems that I'm not the only one with this taste and/or conclusion (so far).

[jadedavid]

I have an Aum Acoustics/Tortuga Audio LDR passive pre. (for sale by the way).The sound is very fast, clean and clear. It also has adjustable output impedance for matching to a power amp. I also have an Audio Horizons tubed pre.
To me the difference between the two could be compared (IMO) to Dynaudio vs Sonus Faber speakers. Where the Sonus is a warmer more emotional speaker, so is the tubed pre. The passive is more like a Dynaaudio, clear & clean but rather uninvolving. Don't get me wrong, both the Dynaudio and the LDR are very good pieces of kit but not my cup of tea.
I like the greater ambiance and warmth that the tubes bring to the table. They just get my toes tapping and connect me closer to the musical event.
Different strokes for different folks.

[Randy Myers]

From my experience the exception to the rule is the W4S STP-SE. No loss of energy or soundstage depth or width.

Jack beat to the punch... The Wyred 4 Sound STP-SE is an amazing design that would be classified as hybrid. It is passive until you get to a certain level where added gain is needed and then it switches to active. From my understanding the level is fairly high where the switch is made. I do not believe I have ever approached the level where the pre-amp switched.

As Jack said, and I agree, the STP-SE is very very open with an incredible sound stage. Very smooth and warm sounding pre-amplifier... one of the best I have ever heard....

[Jim Smith]

IME, they can sound very smooth. In fact, the only real shortcoming has been a lack of dynamics, which was a deal-killer for me.

[nc42acc]

I have a Hattor Audio passive that sounds amazing, rivals many attributes of my REF5SE. Both sound fantastic but different from each other. I think it comes down to do you like strawberry jam or grape jelly.

http://i771.photobucket.com/albums/xx354/mlb3164/8fac092e38ef4799d3326263cd4689c1_zpsoq2n1d8l.jpg

[harri]

Jim
, What kind of passive preamp did you you use. I can imagine the situation of lack of dynamics. I have two systems, both with passive. My second system is with resistors, and it has its shortcomings. but it works between my Dac ( old Cello Reference Dac) and my amp. My main system has MFA TVC customed for me. It has a preamp loop. ( for my old Cello Palette MIV). It has a very low output impedance < 30 ohms usually in my output setting. No lack of dynamics.(OK, I am using Avantgarde Trios with basshorn) It is much better in my system than any acyive I have tried.

Harri

[Tbadder]

I had a Sonic Euphoria for years. No ARC preamp I heard (never lessened to the ref series) are as good. Transparent, attack, wide soundstage, it lacked for nothing. The only reason I moved on was because my system was in desperate need of tubes. You can pick these up cheap

[Jim Smith]

Jim
, What kind of passive preamp did you you use. I can imagine the situation of lack of dynamics. I have two systems, both with passive. My second system is with resistors, and it has its shortcomings. but it works between my Dac ( old Cello Reference Dac) and my amp. My main system has MFA TVC customed for me. It has a preamp loop. ( for my old Cello Palette MIV). It has a very low output impedance < 30 ohms usually in my output setting. No lack of dynamics.(OK, I am using Avantgarde Trios with basshorn) It is much better in my system than any acyive I have tried.

Harri

It was back around 2004 or so.

I think one was Music First, cannot remember the other. I was using Avantgardes, so the slight compression was very noticeable - perhaps a speaker with lesser dynamic contrast might not show it as much. The passives might be better today as well.

[Vapor1]

I don't use pre-amps much of the time, but my reference for clarity, tonal accuracy, and micro-detail is still my inexpensive Placette passive. It has dispatched many a far-more-expensive active pre in it's time, and because of that is likely something I'll never sell.

In years past our sources just didn't output the same amount of current that sources do in general these days. 2.0v outs are common now, so usually one doesn't need more gain to drive their amp to full output.

[KenSea]

I have played around and even built a passive pre before but the problem you will have is the final impedance and having enough gain to driving the front in stage of the power amp. Yes they can do a lot of things really well like being really grain free but in the end you won't be happy. Theres a reason for an active preamp.

Best,
Ken



I don't use pre-amps much of the time, but my reference for clarity, tonal accuracy, and micro-detail is still my inexpensive Placette passive. It has dispatched many a far-more-expensive active pre in it's time, and because of that is likely something I'll never sell.

In years past our sources just didn't output the same amount of current that sources do in general these days. 2.0v outs are common now, so usually one doesn't need more gain to drive their amp to full output.

[Face]

Granted, my sources are a balanced DAC and a phono preamp with plenty of gain(hot rodded Jolida), but I've been using a Wyred 4 Sound STP-SE for years now and it's never been out of passive mode(65+ volume). I've also toyed with Dodd tube based balanced passive preamps and may have come close, but never ran out of volume.

Passives preamps may not be for everyone, but it's foolish to totally dismiss them.

[Dragon_vibe]

Purity Audio, have pre-amps designed to allow you to run them active and passive by a simple switch located on the rear side. I had one for 2 years before it was sold and ran them on both tube pre-amps and solid state. I always preferred the active vs passive. Passive felt more transparent but something always felt missing. Active felt more engaging and did not actually lose much of the transparency. I believe it comes down to how a pre-amp controls the amplifier. Which in turns how the amplifier then controls the speaker. The synergy between each component probably is a more important factor.