Passive preamp buzzing?

[Barry]

These are highly rated on the internet for use in audio



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SMA style connectors as shown were designed to handle RF signals up to 18GHz, and were never intended to be used at audio frequencies.

They can of course be used for audio: occupying almost the same space as an RCA connector; have the advantage of being locked (that is, the outer connector is threaded and the connection is made by screwing the plug onto the socket), but the centre conductor is fragile and SMA connectors are not intended for repeated mating and demating.

I know of only one audio equipment manufacturer who used to use these connectors, and has now replaced them with RCAs.

[Firebottle]

Blimey, I've only been away for a day and there's a shedload of posts!

Here is a suggestion Oliver, this will be of interest to many I would think.

To really compare the GP, and possibly add some drive, follow it directly with an active preamp.
I'll bring my KIN around and we can set it with the volume control at maximum so it's straight in to the active line stage.

[Bigman80]

SMA style connectors as shown were designed to handle RF signals up to 18GHz, and were never intended to be used at audio frequencies.

They can of course be used for audio: occupying almost the same space as an RCA connector; have the advantage of being locked (that is, the outer connector is threaded and the connection is made by screwing the plug onto the socket), but the centre conductor is fragile and SMA connectors are not intended for repeated mating and demating.

I know of only one audio equipment manufacturer who used to use these connectors, and has now replaced them with RCAs.

I'm hoping for a long term solution with very little to no disturbances. They could be the answer.

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[Ali Tait]

I think there is an important point being missed here - the Slagles are only 200 dollars!

How much have you spent on the GP Marco?

[walpurgis]

I'm hoping for a long term solution with very little to no disturbances. They could be the answer.

Sounds like 'an answer looking for a problem' Oliver. Decent RCA phono plugs are just fine. Some don't like them, but they work.

Even the metal they are made from is less critical than many suppose. If the conductor cross section and plug/socket contact area is adequate and clean, the plugs will perform just fine.

[Bigman80]

Ok. I suppose it is really.

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[Marco]

Hi John,

I suspect Jez was a) at the pub so didn't reply and b) meaning that balanced connection offers no advantages over single ended in a domestic situation.

Firstly, if you scroll back, you'll see he replied to Ali Tait, at just after 1am, whilst ignoring both my previous post and the one 'popcorning' him.

Therefore, he'd clearly returned from the pub by then, and I consider him ignoring that as rude, because unless he was blind, he'd have at least seen the post above Ali's (184) with the 'popcorn' emoticons, and so could've responded to me, after having done so to Ali...

Secondly, if what you say is correct about balanced connection, then a) that wasn't the point I was making in the first place, and b) it wasn't at all obvious from his response, implying that I was wrong. Wrong about what, exactly? That's the bit we still don't know!

The problem with active preamps is getting a good one at a reasonable price. I can't understand why they are so expensive, the component costs are tiny compared to say an equally priced valve power amp.

Well, if we take my Croft as an example, first of all, large (over-specced), individually, fully-regulated PSUs, for different parts of the circuit, and the bits required to make all that work, aren't cheap. And that's a MAJOR reason why the best active preamps sound how they do. Good PSU arrangements (to minimise, and virtually eradicate noise) are just so vital, IME, to how (active) hi-fi equipment performs.

Secondly, top-quality 'boutique' [I'm not a big fan of that term, but I'll use it here] components also aren't cheap, such as the best stepped attenuators, caps, resistors, etc, all of which can contribute significantly to the sound.

And last, but by no means least, is the ingenuity and effectiveness of the circuit itself, even before any of the above comes into play, and how successfully it succeeds in maintaining the integrity of the input signal. Therefore when you combine all of that, including the labour involved to put it all together, especially if you want to house the finished product in an attractive, tactile looking case, you can see how it all adds up!

Quite simply, it would be commercially impossible to produce a profitable preamplifier, sold through dealers, which ticked all the boxes above, for any less than about £10k. Unless that is, you're someone like Glenn Croft, who doesn't operate on the same margins as other commercial manufacturers, and so sells these types of preamps (to order) for considerably less.

Marco.

[Macca]

Sounds like 'an answer looking for a problem' Oliver. Decent RCA phono plugs are just fine. Some don't like them, but they work.

Even the metal they are made from is less critical than many suppose. If the conductor cross section and plug/socket contact area is adequate and clean, the plugs will perform just fine.

I'm inclined to agree but I have read somewhere that the percentage of an RCA plug body that actually makes contact with the socket is about 1%. Which is concerning if true. I mean it is never going to make a huge difference, but I don't wonder that all these little things add up. I'm of the opinion that if something is sub-optimal but can be made optimal for little expense and effort, then it is worth making it optimal.

[Bigman80]

I think there is an important point being missed here - the Slagles are only 200 dollars!

How much have you spent on the GP Marco?

You're quite right there, Ali. I seem to remember the FS ad quoting £650. It's Probably twice the price if you factor in the pots and casing etc although I suspect the donor unit cost a fair bit judging by the construction.

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[Marco]

I think there is an important point being missed here - the Slagles are only 200 dollars!

How much have you spent on the GP Marco?

Indeed, and of course that has to be considered. The Slagle is a major bargain, and ticks all the important 'SPPV boxes'. Do you know where it was made (in which country)?

The biggest compliment I can pay the Slagle, is that it would've TROUNCED the Goldpoint, in stock form, which was more than double its price!!

Marco.