Dual mono passive Pre amp, single ended (advice)

[Infinitely Baffled]

Deep breath, chaps! I 'm about to demonstrate my ignorance.

This is a thread about passive pre-amps, right? Yet, in the photographs contained in posting #4, the cases are stuffed with components. I thought the whole point about a passive pre-amp was that it didn't employ all the gubbins that go into an active. Certainly, I have built one or two in the past that consisted only of "in" and "out" sockets, a source switch, a potentiometer and some wire. Sounded great to me (quite possibly down to my sense of amazement that it worked at all). So what is the rest of the innards in post #4? Is it all circuitry required to support the LDR technology, or have I totally missed the point about passives?
Cheers. IB.

[British high fidelity]

Lol i will let Chris answer that as its over my head

Sent from my LG-H961N using Tapatalk

[Light Dependant Resistor]

LDrs are as simple as it can get on their signal side, hence you see just connection
to and from the RCa sockets. But on their anode and cathode a different story.

Ideally the anode and cathode relationship is a potential difference, not necessarily directly
grounding the cathode, Some versions of LDr circuits mix signal ground with DC ground
the better ones do everything to avoid this.

Cheers / Chris

[RothwellAudio]

I can't agree with you Andrew, I wasn't appealed to LDR as it's 'off the beaten track' or whatever you were on about. When several pre amps were compared, the LDR sounded better to me plain and simple. I wasn't looking for something 'different or unusual' it was merely a simple case of amp comparisons. I not an easily led numpty banana , where is a banana emoticon when you want one .

No offence intended, and I certainly don't think you're an easily led numpty banana. If you tried out several different pre-amps and you chose the one with the LDR volume control I don't doubt that it was better than the others. However, I do doubt that the LDR volume control was the reason for its superiority.

[Light Dependant Resistor]

No offence intended, and I certainly don't think you're an easily led numpty banana. If you tried out several different pre-amps and you chose the one with the LDR volume control I don't doubt that it was better than the others. However, I do doubt that the LDR volume control was the reason for its superiority.

Cryptic ? How can an LDR be anything other than an LDR ?
Perhaps you mean removing the mechanical wiping and grinding of conventional pots,
and ridding circuits of signal side input switching, all good reasons why.

[walpurgis]

It has been implied that TVC, autotransformer and LDR pre-amps contribute artifacts and distortion. But, users report an improvement or better sound than via active and basic passive pre-amps. Why is this?

Since using a TVC device, I'm convinced that the sound is better than any pre-amp I've tried before, whether pot-passive, stepped attenuator or active type (valve or solid state).

To suggest that the perceived benefits are the result of 'pleasant sounding corruptions' of the signal seems wrong, as I hear greater clarity, neutrality and purity than before. I have not yet tried an LDR unit, but guess users are having similar experiences.

There has to be more to this. I'm thinking that regardless of measurable artifacts and distortions, the three types of pre-amplifier in question offer capabilities that have not yet been quantified properly and that those who rely solely on measurements to judge them are missing something.

[struth]

Thought the tvc i had was very good too. It didnt work well on every set up i tried it on, but most. I am not big on passives tbh in general, and best pres overall ive used bar the tvc have been good actives.

[Clive]

Passives need to be treated with a little bit of care, eg:

- for a potentiometer or switched attenuator the value chosen can influence the tonal balance and well as there being possible interactions with valve phono stages

- if you use a volume control in shunt configuration the value of the shunt resistor will often significantly change tonal balance

- the cables on the output to the power amp can be an issue as can driving modern solidstate power amps and line level subs - which surprisingly often have a 20k input impedance - power and amp sub amp both with a 20k input impedance is bad news.

- TVCs and AVCs suffer some of these issues too

I find TVCs and AVCs to be very neutral sounding and they sound better than plain resistive attenuators at low volumes - this is sometimes put down to transformers preserving current and only attenuating voltage, is this technically correct?

Overall I'd say passives are less likely than active preamps to be an instant ideal match for any particular power amp. Many integrated amps use a passive (simple pot), in this case the manufacturer is able to select the ideal value pot for the amp and the internal cables are very short, so this is a good environment for a passive volume control.

I'm very much in favour of my AVC pre. That said I feel many people want their systems to have a little personality or be tonally matched to their room, this IMO is best done in one place in the system, either with the speakers or preamp. Ear-bleeding high fidelity doesn't suit everyone so a preamp (likely to be active) can be useful in some systems not just for gain purposes but also for adding that "personality".

Just some of my musings......

[Macca]

It has been implied that TVC, autotransformer and LDR pre-amps contribute artifacts and distortion. But, users report an improvement or better sound than via active and basic passive pre-amps. Why is this?

Since using a TVC device, I'm convinced that the sound is better than any pre-amp I've tried before, whether pot-passive, stepped attenuator or active type (valve or solid state).

To suggest that the perceived benefits are the result of 'pleasant sounding corruptions' of the signal seems wrong, as I hear greater clarity, neutrality and purity than before. I have not yet tried an LDR unit, but guess users are having similar experiences.

There has to be more to this. I'm thinking that regardless of measurable artifacts and distortions, the three types of pre-amplification in question offer capabilities that have not yet been quantified properly and that those who rely solely on measurements to judge them are missing something.

I've heard several auto-transformer designs and LDR designs in comparison and none of them sounded identical so I don't think broad comparsions of the sound of these different approaches actually works in practice. Certainly not to the point where you could say that one particular topology was superior. My own opinion is that a quality stepped attenuator sounds the most natural as much as that can be quantified, however there is very little in it.

I have only heard two active pre-amps that I thought were on a par with a good passive (of any type) and they are Marco's modded Croft and Barry's Mark Levinson. Both ruinously expensive bits of kit.

[Light Dependant Resistor]

It has been implied that TVC, autotransformer and LDR pre-amps contribute artifacts and distortion. But, users report an improvement or better sound than via active and basic passive pre-amps. Why is this?

Since using a TVC device, I'm convinced that the sound is better than any pre-amp I've tried before, whether pot-passive, stepped attenuator or active type (valve or solid state).

To suggest that the perceived benefits are the result of 'pleasant sounding corruptions' of the signal seems wrong, as I hear greater clarity, neutrality and purity than before. I have not yet tried an LDR unit, but guess users are having similar experiences.

There has to be more to this. I'm thinking that regardless of measurable artifacts and distortions, the three types of pre-amplifier in question offer capabilities that have not yet been quantified properly and that those who rely solely on measurements to judge them are missing something.

James, Sovereign presently has the LDr loaner unit which I built many years ago. I will arrange with James for its return here to New Zealand- to update its boards, then provide it back so
each one of you can hear what we are hearing - does that sound like a good idea ?