Preamp shootout...Predictions on which will be the best?

stehno

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Some amps and preamps have measurable distortion, and some people like that… but Hi Fidelity, by definition, means that the signal does not get distorted.
Hi Fidelity never means zero distortion. That only occurs in a perfect galaxy. Hence, Hi Fidelity should imply fewer distortions.

...

A passive pre really may be great when it is run wide open, but as the volume goes low it suffers.
In my experience, the passive works equally well as the 15 or so active (and a few passive) pre-amps I've owned / auditioned over the years. Except that the passive's volume levels must be raised a bit higher to match an active's volume level to achieve simlar db levels - since the signal is not amplified.

Whether passive or active, everything suffers as the volume is lowered to levels significantly lower than the live performance's perceived volume levels.
 

Holmz

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Hi Fidelity never means zero distortion. That only occurs in a perfect galaxy. Hence, Hi Fidelity should imply fewer distortions.

Let’s not devolve into a discussion on how close to zero fewer, or lower, is.
You get the point.



In my experience, the passive works equally well as the 15 or so active (and a few passive) pre-amps I've owned / auditioned over the years. Except that the passive's volume levels must be raised a bit higher to match an active's volume level to achieve simlar db levels - since the signal is not amplified.

The signal is not generally amplified in a preamp.
Most of the ones I have owned go from -infinity to zero.
The latest one actually has a switch for extra gain, but it is not generally required.
The buffering and impedance matching is normally unity gain.


Whether passive or active, everything suffers as the volume is lowered to levels significantly lower than the live performance's perceived volume levels.

How so?
I can see Signal plus Noise, meaning that with a fixed noise, then we want more signal.
But “suffering” is not the word I would use… sometimes we need the volume to be low.

If the system is run at a high volume then the passive can make sense.
However when it is run at a lower volume, then it is just a plain fact that the output impedance of the passive pre is generally prone to becoming problematic.
That listening volume, then becomes an important consideration to the discussion. <— that is the main point I would like to ensure comes across.
 
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NekoAudio

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I'm also completely unaware of any OPPO product that included a passive volume control in it. I believe their disc players all used the ESS DAC chip's built-in volume control, while some other products like the HA-1 (and maybe the Sonica) used an analog potentiometer but I would not call it a passive volume control because there were active components in the signal path.
 

Atmasphere

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If the OPPO volume attenuation is not passive, this is the first I've heard of such. As I recall, OPPO called it passive as well as a host of others reviewing / evaluating it. I remember reading a 10 or 20 page white paper discussing how OPPO was using unused portions of the 32-bit ESS Sabre DACs for that specific puprose reportedly with zero bit loss.

Not to mention the sonic characteristics of the OPPO's volume attentuator behave much like a passive (significantly lowered volume levels, improved clarity, etc).

Do you have any evidence that the OPPO's volume attenuation is not passive?
Emphasis added.
This is a digital volume control. This means that once the digital signal is converted to analog, the analog signal will be treated by the output buffer (usually an active opamp circuit) of the DAC. This is not a passive control; there is usually gain in the output buffer. As I mentioned earlier, OPPO has had pretty good active volume control systems in their equipment.

So if its has been described as a passive control, its one of two things: Either its not a digital control at all and the paper you read about the 32 bit device was erroneous, or the description of it being passive was erroneous. A passive control is never a digital control IOW.

IOW you read the evidence yourself. I would contest your assertion that the OPPO control 'behaves much like a passive (significantly lowered volume levels, improved clarity, etc)'; in fact its acting like an active line stage in that regard and from the sound of it, doing exactly what I described a good active line stage can do earlier.
 
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I´ve been running a TVC solution since 2K and it takes some consideration reg impedance and source matching
I don´t loose dynamics at lower volumes....
 

Atmasphere

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I´ve been running a TVC solution since 2K and it takes some consideration reg impedance and source matching
I don´t loose dynamics at lower volumes....
If you have done your homework WRT impedance and source matching, TVCs can work quite well. The usual problem with them is that as you change taps, the load needs to change with it so that the device doesn't ring (distort), roll off and doesn't express its inter-winding capacitance as a hump in the frequency response.

That can be tricky since the amplifier is a fixed load and one the manufacturer can't predict. The source impedance is also an unknown. If the source impedance changes, that throws off the correct load impedance, since transformers transform impedance. So when you change the source impedance (which varies from source to source), every load on every tap has to be optimized accordingly!

On that account with all those variables I've never seen a TVC that actually worked. Kudos if you have!
 
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wouldn´t it be better with an impedance matching, nogain buffer then
why amplify a source which can well deliver 5-30v on it´s own, just to strangle it to 3-5volt?
 

Atmasphere

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wouldn´t it be better with an impedance matching, nogain buffer then
why amplify a source which can well deliver 5-30v on it´s own, just to strangle it to 3-5volt?
The problem is digital sources, most of which are built to Redbook standard. That standard calls for the output to be 2 Volts, although some are 3Volts, and that's single-ended. If the digital device has a balanced output, and since most do not support the balanced standard, the output might be double that (if the standard were supported, the output level would be the same).

So you have to ask yourself 'why would they want the level so high that most amplifiers would be overloaded or near full output if connected to this output?'

I don't have a good answer as to what they were thinking, other than they probably weren't. Perhaps they thought that digital was so good that no-one ever would want to listen to any other source (such as a tuner or video...). But that sounds a bit ridiculous- the 'not thinking' explanation is simpler and far more likely IMO.

So you must knock the signal down, unless you have a DAC that somehow does not support that ridiculous spec. If interconnect cables are involved that's where this scenario gets in trouble in high end audio.

I agree a buffer that isolates the load from the volume control is about as simple as you can get without the interconnects getting in trouble. There are far fewer of these devices out there than there should be IMO. I think most people have this idea that 'simpler is better' (which it often is) but in this case its an example of getting too simple to the point its unable to tick all the boxes.
 
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Holmz

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wouldn´t it be better with an impedance matching, nogain buffer then
why amplify a source which can well deliver 5-30v on its own, just to strangle it to 3-5volt?
It is pretty common to strangle it with an active circuit… like an OPamp.
 

DasguteOhr

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Hattor audio have nice conzept, passive preamp (khozmo)+ active tube gain stage/buffer when you need it. You can reduce gain with switches. Sounds pretty good
 

Atmasphere

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It is pretty common to strangle it with an active circuit… like an OPamp.
Opamps can be excellent if used correctly. The newer ones made today have Gain Bandwidth Product values that are quite high, which helps to allow the opamp to have a ruler flat distortion vs frequency characteristic across the audio band- similar to an SET, but of course vastly lower distortion. This works as long as you don't ask too much gain of them (20dB seems typical these days, ask for more and you risk troubles).

Most output buffers of DACs don't need that kind of gain and if they do, the pragmatic designer can simply use a 2nd opamp, maintaining neutrality.

Quite often more gain than that is asked of opamps, in which case the design of the opamp starts having an effect on the way it sounds. So, if modern opamps are used, your comment is more about the skill of the designer rather than the opamps themselves.
 

Holmz

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which doesn´t necessarily means smart :rolleyes:

If it lowers the output impedence to be in a usable range, then it is generally not a stupid Thing to do.

Having something behind a volume knob to maintain some usable output impedance when the volume is low is a way to make a preamp more immune to the loading from the cable that leads away from it.

i was assuming that your reference to “strangling it” was some resistor network…?

Opamps can be excellent if used correctly. The newer ones made today have Gain Bandwidth Product values that are quite high, which helps to allow the opamp to have a ruler flat distortion vs frequency characteristic across the audio band- similar to an SET, but of course vastly lower distortion. This works as long as you don't ask too much gain of them (20dB seems typical these days, ask for more and you risk troubles).

Most output buffers of DACs don't need that kind of gain and if they do, the pragmatic designer can simply use a 2nd opamp, maintaining neutrality.

Quite often more gain than that is asked of opamps, in which case the design of the opamp starts having an effect on the way it sounds. So, if modern opamps are used, your comment is more about the skill of the designer rather than the opamps themselves.

I don’t believe that my analogue equipment has OP amps.
But my comment was more that OP amps have been ubiquitous in a lot of gear since time dot.

but admittedly I do not dive into the internals and look at the guts of my gear.
i have had the covers off on my phono stage, pre amp, and powersupply… but that was to flip dip switches and replace tubes.
However I have not looked inside of the DAC. And if I did, I am not sure I would know what to look for ;)

Hence; I’ll defer to you Ralph.
 
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stehno

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To be clear, you are not running a passive volume control. The OPPO uses an active system. In short we're on the same page.

To answer your last question: sure. FWIW, dynamics comes from the signal not the equipment. If the equipment is messing up, you can lose dynamic impact, but if you gain 'dynamics' its a pretty good bet that distortion is playing a role (this is common with SETs for example).

If I can point something out here- high end audio is not driven by price although many people think it is. Instead its driven by intention. That is why OPPO did so well with their relatively inexpensive products. My guess is they likely priced them according to a formula rather than to what the market will bear and there was someone important in the company who was an audiophile. So answering your first question: maybe.

To answer your 2nd question- since I've run into that a lot, I've not bothered since a passive won't work right unless you put it inside the thing you are driving with it (for example inside an integrated amp).
Sorry for my delayed response. I stand corrected and thanks for clarifying. And my apologies as I was a bit arrogant or at least overly confident about that. Because of the behaviors it’s still hard for me to believe so I reached out to another to confirm your accuracy. And it seems anything I thought I read 8 or 9 years ago is nowhere to be found.

I need to ask this. Might it be possible that the OPPO units just have a lower than standard voltage at the line out? I’ve been using XLR ic’s for the past 20+ years so it’s not like I’ve been bouncing back and forth between single-ended and balanced outputs.

I ask because in my previous post I mentioned the OPPO’s volume attenuator behaving as a passive. As mentioned earlier, in 2014 I’d purchased a pair of 575wpc monoblock Class D amps. However, what I didn’t mention was just 30 days prior to that I’d purchased a 575wpc Class D integrated amp (same mfg’er) that was anything but musical yet dynamic were way over-the-top and including a horrific “jump factor” where my ears were seemingly running up to the soundstage for a note’s initial attack (in my face) and my ears running back to the audience for the ensuring decay. Entirely unmusical and since I had a 30-day satisfaction guarantee, I returned the int. amp for their pair of monoblock amps – same wpc.

I should also mention this is not my first rodeo with Class D amps as I used to sell Nuforce amps and I remembered testing my passive, dedicated, bi-directional filtering line-conditioners with nuforce monoblock amps for their bi-directional digital-like distortions induced by the amps’ high-speed switching modules. Long story short as I contemplated why the 575wpc Class D integrated amp was so overly dynamic and downright nasty sounding I remembered my experiment with the Nuforce amps and shared verses dedicated line conditioners and concluded that the 575wpc Class D int. amp had to be sharing this digital-like noise between both channels and again at the pre-amp causing this high level of unmusicality so I returned the int. amp for a similar pair of Class D 575pwc mono-blocks where each obviously had its own AC inlet. This is why I’d never purchase Class D stereo amps because I can do nothing to prevent this internal sharing of distortions between channels.

Between 2000 and 2014, I’ve owned or auditioned somewhere around 15 – 18 preamps including a couple of passive pre-amps and also owned / auditioned maybe 12 – 15 amps. Upon receiving the 575wpc monoblock amps and switching to the OPPO’s volume attenuator, this was by far my most musical config right outta’ the box.

Anyway, having said that I can now elaborate on my prior statement that the OPPO behaves like a passive pre. Because when I replaced the 575wpc Class D integrated amp with a pair of Class D 575wpc monoblocks (same mfg’er), I was able to install one passive, dedicated, bi-directional filtering line conditioner on each amp. IOW, no more sharing of distortions between L&R channels. And by using the OPPO’s volume attenuator, seemingly no more added distortions at the pre-amp stage and those added distortions being amplified there.

Bottom line is, with the OPPO‘s volume attenuator and monoblock amps, immediately everything recessed entirely back onto the sound stage where it belonged including a note’s initial attacks with my ears firmly planted in the audience where they belong, hence the perceived more natural dynamics. No more in-my-face initial attacks, no more overbearing electronics-induced jump factor, etc, plus the notes were more pristine, delicate, etc. IOW, typical behaviors I’d expect from a passive pre.

I can’t find the specs but for this reason I have believe that since the OPPO volume attenuator is not passive as you say, then I'd have to guess it's producing a lower output voltage at the line outs. Maybe somebody else can confirm that but I can’t seem to locate any such specs for 105d or 205.

Regardless, based on my experience, there seems to be something passive-like about the OPPO that when mated to high-powered amps, makes for a rather musical and dynamic presentation.

Anyway, my apologies for being flat out wrong. But because of these experiences I have to believe something is different at the OPPO… like a lowered voltage at the line outs, less signal amplification, or perhaps something else???
 

Holmz

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can’t find the specs but for this reason I have believe that since the OPPO volume attenuator is not passive as you say, then I'd have to guess it's producing a lower output voltage at the line outs. Maybe somebody else can confirm that but I can’t seem to locate any such specs for 105d or 205

It is producing less voltage if it is attenuating the signal.
it is certainly not “line level”, or the speakers would be PDL. (pretty dxxx loud)
 

stehno

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It is producing less voltage if it is attenuating the signal.
it is certainly not “line level”, or the speakers would be PDL. (pretty dxxx loud)
I was thinking more along the lines of something less that the typical 2v for single-ended or the 4v for balanced at the low-level line outs.

Which reminds me. Another behavior I neglected to mention was before and after volume levels going where with the OPPO's volume attenuator I had to increase volume levels by maybe 20% or so to maintain same preferred db listening levels. And the after's max volume db levels became significantly lowered with the OPPO's volume attenuator than with any typical active pre-amp config I've had. Again, as I recall these too are characteristics typical of a passvie pre.
 

Atmasphere

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Anyway, my apologies for being flat out wrong. But because of these experiences I have to believe something is different at the OPPO… like a lowered voltage at the line outs, less signal amplification, or perhaps something else???
OPPO equipment met the Redbook standards (2V single-ended). What is happening here is simply that they had a good volume control system coupled with a competent line stage.

I've maintained that if you have a good competent line stage that no passive can compete- this is as good an example as any- so good it had you fooled, if you were under the impression that a line stage can't be as musical as a passive control ;) Its no surprise that people were unhappy when OPPO got out of the game. They made very competent equipment at realistic prices so were a good example of what I mean when I say high end audio is driven by intention rather than price.
 
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PYP

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I've maintained that if you have a good competent line stage that no passive can compete-
@Atmasphere Given your experience designing and manufacturing very well-regarded amps/preamps, you are clearly making this statement with a lot of experience. But I'm puzzled by the performance of the digital attenuator in my DAC going straight to the amps (same manufacturer). Together, they produce a very alive, live-like presentation with plenty of dynamics. Since I haven't tried the Mola Mola preamp, I don't have a comparator however. Thoughts?
 

stehno

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OPPO equipment met the Redbook standards (2V single-ended). What is happening here is simply that they had a good volume control system coupled with a competent line stage.
Good to know, thanks.

I've maintained that if you have a good competent line stage that no passive can compete
After 9+ years of preconceived narrative conditioning under my belt it's not so easy for me to say that I just might have to concur. Now. :)

- this is as good an example as any- so good it had you fooled, if you were under the impression that a line stage can't be as musical as a passive control ;)
Bear in mind that it was only since the introduction of the OPPO’s volume attenuator that I thought was AND seemingly behaves as passive AND when combined with my 575wpc that convinced me to steer clear of active pre-amps for the almost 10 years now. And FWIW, all 15 – 18 of my active pre-amps ranging from $600 - $10k at least from a dynamics perspective were all cut pretty much from the same cloth regarding behaviors / sonics. Only the OPPO stood out as different, more recessed, and clearly more musical and with seemingly more natural dynamics.

Its no surprise that people were unhappy when OPPO got out of the game.
Indeed. Back around 2006 -2007 timeframe when I owned and was selling Nuforce Class D amps, Nuforce was helping to promote OPPO onto the scene as I kept hearing rave performance comments about the OPPO’s around that time. Since I owned an Esoteric CDP and was selling Esoteric at that same time, I paid no attention to OPPO as I simply didn’t think a $900 unit could compete with my built-like-a-tank $8400 unit. But hey, we're all guilty of believing preconceived narratives, right?

In fact, I only entertained the OPPO 105d because they had a money-back satisfaction guarantee and I wanted to see what all the OPPO’s hubbub was about. Upon initial install the OPPO oh-so-slightly edged out the Esoteric but performance was near identical. Since the Esoteric CDP was aging a bit and I was no longer selling Esoteric, I chose to stay with the OPPO since by now the only thing the Esoteric unit offered over the OPPO was the bling.

It was only when I engaged the OPPO’s volume attenuation that it significantly surpassed my Esoteric’s performance. And it soared to another musical level again once I stopped using the OPPO’s CD transport and starting using the OPPO’s USB to retrieve my music from a local Solid State Drive – but only after the USB section fully burned in. And for which the Esoteric had no such capability.

I was pleased enough with the OPPO’s performance that I kept the OPPO 105D unit for 9 years and only replaced it with the OPPO 205 last May which was yet another nice musical improvement.

They made very competent equipment at realistic prices so were a good example of what I mean when I say high end audio is driven by intention rather than price.
Indeed they did. But I’d like to offer a minor correction by saying that SOME in high-end audio are driven by intention rather than price. And yes, very sad when OPPO packed their high-end audio bags.

Anyway, thanks for correcting me on this gross oversight.
 
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analogsa

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Bear in mind that it was only since the introduction of the OPPO’s volume attenuator that I thought was AND seemingly behaves as passive AND when combined with my 575wpc that convinced me to steer clear of active pre-amps for the almost 10 years now. And FWIW, all 15 – 18 of my active pre-amps ranging from $600 - $10k at least from a dynamics perspective were all cut pretty much from the same cloth regarding behaviors / sonics. Only the OPPO stood out as different, more recessed, and clearly more musical and with seemingly more natural dynamics.

It is easy to peek under the Oppo's lid and see how little connection to reality this fantasy bears.

Not only is the attenuation not passive, it is also digital, courtesy of the Sabre chip. Downstream there are a bunch of opamps, enough to exceed the signal path length of whatever is inside most active preamps. Looks like a very competent but also very conventional design, the same topology as a myriad of other dacs.

Could it sound better without the addition of an external preamp? Certainly, depending on the particular set of components and listening preference.

Getting a preamp which does not impose an obvious sonic imprint is one of the toughest challenges in audio. Not sure there is even a market for one, just look at those multi tube monstrosities with a $2 attenuator chip inside :cool:
 

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