Solid state preamp grain compared to valves

[anthonyTD]

Martin is not wrong in his explanation of why a simple conventional attenuator'when judged purely on its own merits should be capable of higher accuracy, therefore, higher fidelity, however, that is only relavent until you couple it to the source, and power amp impedances, via some form of cabling, then everything else thats connected to it comes into play.

But don't forget, passives automatically offer 'greater fidelity', because they're measurably more accurate!! [Sorry, Macca]

However, yes, thanks for that. You've offered a reasonable technical explanation for what I can clearly hear, and that's why I've given up now with conventional passives.

Marco.

[Marco]

Martin is not wrong in his explanation of why a simple conventional attenuator'when judged purely on its own merits should be capable of higher accuracy, therefore, higher fidelity, however, that is only relavent until you couple it to the source, and power amp impedances, via some form of cabling, then everything else thats connected to it comes into play.

But don't forget, passives unquestionably offer 'greater fidelity', because they're measurably more accurate!! [Sorry, Macca]

However, yes, thanks for that. You've offered a reasonable technical explanation for what I can clearly hear, and that's why I've given up now with conventional passives.

Marco.

Lol - daftee, you've posted your reply by editing it into my last post (#144)!!

I didn't write that, you did!

Marco.

[Marco]

Anyway, allow me to reply to the post's correct author, lol:

Martin is not wrong in his explanation of why a simple conventional attenuator'when judged purely on its own merits should be capable of higher accuracy, therefore, higher fidelity, however, that is only relavent until you couple it to the source, and power amp impedances, via some form of cabling, then everything else thats connected to it comes into play.

...potentially adversely affecting fidelity, downstream.

Absolutely, the first part is fine, which I completely agree with. It's the latter bit, in bold, which is an indisputable fact, and which potentially changes the behaviour of the passive in question, thus also (potentially) the level of fidelity downstream, which the system is capable of [and which wouldn't be the case with an active design], he was simply failing to grasp

It doesn't matter if a passive is as accurate as a very accurate thing. It's useless on its own, and its behaviour, as discussed, and thus performance, is heavily governed by the stuff it's coupled to, which you've mentioned. So what matters in the end, is what you hear coming out your speakers, by using a passive in your system, not how accurate one is on its own merits.

And if you could measure what was happening there [once it's coupled to a source, etc,] that's the measurement that would ultimately be the most important!

Marco.

[struth]

trying to drop you in the shit

[Marco]

Ok, returning now to LDRs, so Anthony, are you saying what I've outlined here:

Now, when I use an LDR, there are no such issues of 'chasing lost dynamics', or trying to equalise loudness levels, as the sound has all the 'balls', 'guts' and 'drive' of the Croft, but sounds like an LDR, exhibiting the beguiling nature of its style of music-making, not a high-end (extensively modified) valve preamp, which does things a little differently, but equally as valuably. That's why I'd like to have access to both types of presentations, and I'm having a Stereo Coffee LDR built.

...is simply due to an LDR essentially acting as a 'loudness control', due to its non-linearity?

Marco.

[Marco]

trying to drop you in the shit

Aye, these Valley Boys are devious buggers!

Marco.

[Macca]

Anyway, allow me to reply to the post's correct author, lol:



...potentially adversely affecting fidelity, downstream.

Absolutely, the first part is fine, which I completely agree with. It's the latter bit, in bold, which is an indisputable fact, and which potentially changes the behaviour of the passive in question, thus also (potentially) the level of fidelity downstream, which the system is capable of [and which wouldn't be the case with an active design], he was simply failing to grasp

It doesn't matter if a passive is as accurate as a very accurate thing. It's useless on its own, and its behaviour, as discussed, and thus performance, is heavily governed by the stuff it's coupled to, which you've mentioned. So what matters in the end, is what you hear coming out your speakers, by using a passive in your system, not how accurate one is on its own merits.

.

I wasn't failing to grasp anything. You made the unqualified assertion that active pre-amps offer the highest possible fidelity, I pointed out that was not true and that a passive attenuator offered higher fidelity. yes I did not qualify that because I figured that the 'when partnered correctly' bit was self-evident. Clearly not.


Re the 'softness' of the passive pre - I am sort of in agreement here, there can be a hint of softness most evident on rimshots/snare. I have noticed that this can be ameliorated or exaggerated by choice of speaker cable and interconnects. It will also vary depending on the design of the passive. I can get snares to hit me between the eyes with my system, however I prefer a less full-on presentation.

I am not convinced that being hit between the eyes by snares is not actually a colouration. It is hard to tell without talking to the studio engineer. I do suspect that it is not truthful and that it is a hang over from the presentation of the old 'flat earth' systems, IIRC Linn Kans were very good at it due to their massive mid-range hump. Obviously all that is speculative.


The Goldpoint passive you had for a while was IMHO not much cop even after the mods, in the passive pre bake off we had at one of the NEBOs it was comfortably in last place I thought. I don't know what other passive pres you have tried in your system.

[anthonyTD]

Well, if something in the audio replay chain has a non linear action, then somewhere in the audio frequency band, there will be more, or less output at certain frequencies, that could just happen to be right in the most sensitive part of our hearing, or it could be way out at one end, or both, this could indeed account for the reason one would prefer one type of passive attenuator, over another, either way; by its very nature, such an attenuator cannot be classed as high fidelity,even though its affect may be deemed as more pleasing, or more real by the individual listener!

Ok, returning now to LDRs, so Anthony, are you saying what I've outlined here:



...is simply due to an LDR essentially acting as a 'loudness control', due to its non-linearity?

Marco.

[anthonyTD]

I thought I corrected it???

Aye, these Valley Boys are devious buggers!

Marco.

[anthonyTD]

Thats a good way of looking at it Alan.

I have been trying to understand just what causes the difference with passive attenuators, I have heard the effect with a few.
I will put forward this hypothesis, so feel free to discuss.

Frequency response and phase response are inextricably linked, so although we cannot hear very high frequencies we CAN discern small phase differences.
When the frequency response of an amplifier or system is limited there is always a phase shift as the frequency limit is approached.

Now keeping things simple, imagine the output of the passive/active preamp driving the capacitance of the interconnect leads:

With a passive with its associated larger output resistance the hf frequency response is always curtailed, very much in the ultrasonic range (to our ears) in virtually all cases, BUT even though we cannot hear the frequency where the response falls there is always an alteration to the phase response.

With an active preamp with a much lower output resistance there is much more drive to charge/discharge the capacitance of the interconnect leads, so the hf response is affected much less, with the correspondingly smaller effect on the phase response.

So my hypothesis is that the missing bit with the passive approach is phase accuracy.