Are LDR pres the ultimate passive?

[Marco]

Sounds like a plan, so let me know!

Marco.

[Barry]

Great write up Jason!

I've always been interested in the idea of LDR controls, if only for their elegance and simplicity. Yet I had niggling doubts concerning the linearity of the LED/LDR devices themselves. Following you review/appraisal it would seem that LDR attenuators do have advantages over a simple resistor stepped attenuator.

What would be nice would be a 'bake off' between the LDR device and a stepped transformer attenuator.

[Figlet108]

I made several LDR pre-amps both for myself and others following the disclosure by Mr Stanscheff of his circuit. There was a long thread on Diyaudio about 3-4 years ago. The one that I use in my system now is the first one I built on a piece of perfboard and cost about £15 including a simple 7805 circuit to power it. I was amazed by the sound then and I still am. I later added a motorised Alps pot as I had a remote board and controller from a previous project. IMO it has a lot of the quality's of a good active pre. I am also amazed that it is still working perfectly (tempting fate here!)

Rob, it's interesting that you have had your LDR for a while and that you still really rate it. The test of time is obviously not something I have experience of yet.
It's also interesting that unlike other pres, you can be confident that adding something like a remote motorised volume control can't (in theroy) effect the signal path in any way, so it's a guiltless option

[Figlet108]

Pity there wasn't a good valve preamp in there to add another interesting and valid facet to the test... If you guys had said you were doing this, I'd have popped down and brought the Croft!

Marco.

Marco, actually Martin and I were thinking about having a listening session over at mine when he comes to collect his Stereo Coffee LDR once I connect it up. Why don't you join us and we can all have a listen to your Croft, the NVA and one or both of the LDRs?

[Figlet108]

Great write up Jason!

I've always been interested in the idea of LDR controls, if only for theor elegance and simplicity. Yet I had niggling doubts concerning the linearity of the LED/LDR devices themselves. Following you review/appraisal it would seem that LDR attenuators do have advantages over a simple resistor stepped attenuator.

What would be nice would be a 'bake off' between the LDR device and a stepped transformer attenuator.

Barry, what I would have liked to happen was for this mass bake off that Macca was trying to organise to go ahead, and for folks to bring their passive pres so that there would be representation from all different types of passives, including transformer based ones.

I know I only have one data point so far, but I suspect that LDRs in general will be better in general as a technology compared to resistor stepped attenuators. I don't think there is anything wrong with the NVA we used, I think it's more the technology that has its limits.
So yes, I'd be interested in taking the next step and comparing with stepped transformer attenuators.

Who has a good one and can we arrange a bake off?

[Marco]

Marco, actually Martin and I were thinking about having a listening session over at mine when he comes to collect his Stereo Coffee LDR once I connect it up. Why don't you join us and we can all have a listen to your Croft, the NVA and one or both of the LDRs?

I'm well up for that - just let us know when you fancy it!

Marco.

[jandl100]

I had a DIY Paradise Eva2 LDR passive pre for quite a while, and yes it was excellent in its way - transparent and well detailed. But it didn't have the drive of a decent active pre, imho, it sounded a just a little bit limp in the systems I used it in. Not a very 'exciting' listen. I kept it as a spare for quite a while, but never really felt the need to reinstate it so sold it on.

One of these ....

[Figlet108]

Absolutely Jerry, and I'm not at all suggesting passives are for everyone.
This isn't really an active vs passive thread.

But for those like me that are firmly determined to build systems around passives, I'd like to find out if any of the passive technologies are generally and fundamentally better than all the others. Or are passives technology-agnostic and it's just down to the individual products?

[Figlet108]

I'm well up for that - just let us know when you fancy it!

Marco.

Yep, I'll PM you both.

[Marco]

Coolio on the forthcoming sesh I'm curious about this statement, though:

But for those like me that are firmly determined to build systems around passives...

Why? For me, that kind of thinking is way too restrictive.

I'd never be "firmly determined to build a system" around ANY specific component, as by doing so I might be missing out on using something else that's better...!

Therefore, my system building methodology has always been to keep an open mind, dismiss nothing out of hand, listen to as much different kit as possible, and be prepared to update my opinion, as to what is considered as 'best', at any time!!

Marco.