Help! Idiots guide to pre-amping needed

[littlest hobo]

Please can someone provide me with a very basic explanation of pre-amping (passive v active) etc. I'm looking cheap as chips end of the market - I hadn't intended going down this route but the ""integrated"" valve amp I bought only seems to behave when attached to a pre-amp.

My budget is around £200 second hand, how do I work out if a passive pre would be suitable for my system?

Thanks

[The Grand Wazoo]

Very basic?
OK - a passive will provide control over volume & (maybe) some switching between sources.
They won't do record players without a separate phono stage.
They don't use power from the mains.
They don't like long cables between them and the power amp.

Many people are initially impressed by what passives have to offer but later realise that an active pre-amp is ultimately more satisfying.

[DSJR]

It's also to do with input sensitivity and impedance I think as well. Transparent active line stages can be done with a couple of modern op-amps these days (although we hairshirt audio-idiots don't approve of them) although for correct impedance matching, it may be best to look for a simple valve line buffer.

For very low cost, a Musical Fidelity X10-D buffer between your source and amp (assuming your amp has a volume control) would be cool for well under £100. The Rock-Grotto component upgrades (especially the valves) do seem to help remove the slightly "thick" quality this unit has in stock form and I rate my tweeked one highly for the job it has to do.

For solid state, there's this - http://spl.info/index.php?id=184&L=1

Not much dearer than the top of your budget and can be used balanced or single ended. Looks nice and will drive properly any reasonable length of signal cables, putting the power amp up near the speakers where it belongs :)




P.S. Old Croft Micro preamps from the early 90's don't come up very often (I wonder why???? :lol:), but the little Micro 25 Basic is lovely, can be tuned with some careful valve rolling and interconnect choice (Klotz AC110 perhaps in this case?) and these do come up second hand for around £250 as owners upgrade to the next level.

[YNWaN]

I don't see how much of what you have written above could be classed as 'very basic' advice Dave (I don't even agree with much of it).

Claire, what do you mean when you write that your integrated valve amp will only 'behave' when driven by a pre-amp? In what way goes it misbehave if a pre-amp is not used (what exactly is the integrated you mention)?

It is quite likely that the valve integrated you have is, essentially, a passive pre-amp connected to a valve power amp and built into a single case. If you have found that you require a pre-amp then the chances are that you need an active pre-amp.

If a pre-amp has a mains lead then it is active and applies gain (volume) to the signal. If it has no power lead it is passive and is just a volume control and a switch - passive pre-amps add no gain, they just reduce the volume from max. My experience of passive pre-amps (other than those that use transformer coupling) is that they reduce dynamic contrast and sound emasculated compared to their active cousins.
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I must be one of the "hairshirt audio-idiots" referred to by Dave because I don't think a transparent pre-amp can be made with "a couple of modern op-amps" (I've not heard one any way) - you can make a very cheap one though and little actual designing is required (Dave, it sounds loke you are repeating Ashley's party line?)

[Ali Tait]

Not always- the Pass B1 is a mains connected passive pre that includes a buffer.

[YNWaN]

Yes, I've heard one of those - didn't like it either; in fact, I thought the system was much improved when it was removed.

[Ali Tait]

I have one, I think it's very good, though mine has been built with silver wire and good components.

[YNWaN]

Yes, the one I heard was similarly constructed (some very fancy components). It sounded clear and lucid, but I thought it lacked dynamism, did odd stuff to the stereo image and, ultimately, wasn't actually that transparent (sorry, but that's as I found in that case)

I also tried some related buffer boards in my own pre-amp and didn't like them either.

[Marco]

Hi Claire,

Let's start at the beginning... Which integrated valve amp is it you've got? And what is it that doesn't work and/or you don't like about the preamp that's built into it at the moment?

I'm struggling to think of any decent standalone preamp for £200 which is going to significantly upgrade what you already have.

In that respect, I suspect that sending your amp to someone like Nick Gorham or Anthony TD (our resident valve amp experts), and giving them the £200 to spend on improving the internal components/layout of your existing amp, may well be the best way foward, in terms of giving you the 'biggest bang for your buck' :)

Marco.

[Ali Tait]

Good advice Marco.

[littlest hobo]

Thanks for the replies...some err more basic than others ;) and apologies for the rude delay in replying, been busy decorating and gardening.
The amp is a Music Angel XD800 mk3. It's away for repairs but they are struggling to replicate the problem - loud crackle on switch off and high-pitched whine in right channel when playing :(. Working fine for the repairer. Meanwhile I'm running the same setup at home with an Amptastic Mini-T or old Rotel D class amp without any probs. Repairer been running it through a pre with no faults but now no faults as integrated either. So think I've sent you all on a red herring.

It's a disappointment after the joy of discovering this site and enjoying the wonders of a little Mini-T £65 amp - but hope to retrieve the less than angelic music angel soon and all sorted.

[YNWaN]

The "loud crackle on switch off and high-pitched whine in right channel when playing" don't sound like issues relating to the lack of a pre-amp - more likely to be old capacitor values drifting, or dry solder joint(s) or dodgy valve (or valve base).

[jandl100]

Oh dear - it does sound like the Music Angel needs some TLC. Intermittent faults can be the hardest to sort out.

If your chosen repairer doesn't manage to sort it out, I'd strongly recommend following Marco's advice and send it to one of the valve gurus on this forum!

Best of luck with it.

But in the meantime you have an excellent amp in the Mini-T. :)

[anthonyTD]

The "loud crackle on switch off and high-pitched whine in right channel when playing" don't sound like issues relating to the lack of a pre-amp - more likely to be old capacitor values drifting, or dry solder joint(s) or dodgy valve (or valve base).
I agree,
power supply caps in these amps are not the best and can produce the kind of issues you describe, also, coupling caps. Solder joints on these amps are another big problem as the ones i have had in have not been good at all.
Anthony,TD...