What difference a pre-amp do?

[Arkless Electronics]

... which is entirely lost if the source(s) feeding it isn't properly buffered and the power amp has unexpectedly low input impedance.

Whilst I can't be bothered right now to list all the circumstances where that would be wrong, or otherwise, one should expect to have to check such things before choosing a suitable pre amp or passive.

 

[Curtis]

I have no issues with people preferring an active pre amp in their system.
What I have an issue with is sheep leading other sheep into what they believe are facts which are in fact complete bollox.

 

[mandryka]

So, how can Naim claim that’s its power amps need a Naim pre to perform properly?

Why don’t you ask them? I mean it looks like a perfectly reasonable question.

 

[James]

Whilst I can't be bothered right now to list all the circumstances where that would be wrong, or otherwise, one should expect to have to check such things before choosing a suitable pre amp or passive.

The point I was trying to make is compatibility matters, because there are no standards for impedance matching. Most modern 2V sources should be able to drive a high input impedance (say 47kohm or more), but all bets are off if an unbuffered source is trying the same thing with 10kohm load. I recall that Naim amps have lowish imput impedance (18kohm?), whereas my classic Pioneer M-22 is 50kohm.

 

[matt j]

No. None of that is possible. Unless it is fitted with a dynamics processor and/or tone controls or has some bizarre form of distortion then you cannot add or remove "drive and energy" or "excitement and engagement". Those are entirely human constructs...

Maybe they're just layman terms for things non technical people hear but are unable to describe in technical terms, that doesn't mean they're not hearing it, just not describing it to your liking.

As another non technical (Hi-Fi wise) layman, I'd describe a lot of passive pres I've heard as 'plenty of volume but no bollocks.'

 

[Sue Pertwee-Tyr]

The point I was trying to make is compatibility matters, because there are no standards for impedance matching. Most modern 2V sources should be able to drive a high input impedance (say 47kohm or more), but all bets are off if an unbuffered source is trying the same thing with 10kohm load. I recall that Naim amps have lowish imput impedance (18kohm?), whereas my classic Pioneer M-22 is 50kohm.

My (Albarry) power amps are quoted as '5K1 Ohms' which is a convention I'm not familar with. Can anybody translate this?

 

[Marchbanks]

5.1k (in the same way that 5R6 is 5.6 ohms.)

 

[Sue Pertwee-Tyr]

Thanks. Perhaps that explains why my experience with passive preamps and direct input from DACs has lacked oomph, then? Surely that does imply that the output stage isn't capable of sufficient current delivery for adequate compatability with the low input impedance of the amp?

 

[Robert]

Thanks. Perhaps that explains why my experience with passive preamps and direct input from DACs has lacked oomph, then? Surely that does imply that the output stage isn't capable of sufficient current delivery for adequate compatability with the low input impedance of the amp?

Absolutely. Also worth remembering that the output stage of many sources is op amp based, and some of those exhibit high distortion when driving lower impedance loads.
With 5K input impedance you would have to match carefully and can expect quite noticeable sonic differences with different partnering equipment.

 

[Arkless Electronics]

Thanks. Perhaps that explains why my experience with passive preamps and direct input from DACs has lacked oomph, then? Surely that does imply that the output stage isn't capable of sufficient current delivery for adequate compatability with the low input impedance of the amp?

No it doesn't. Most DAC's and the majority of other gear will have op amps at the output and most are specified to work into 600R and will have no issues with 5K. It will likely give problems with a lot of valve sources/pre amps and with some gear there could be bass loss due to the output capacitor in the driving source, if present, being rather too small for driving 5K. A Passive should ideally be 10K or so and this means the passive is in itself a lower than average impedance load for whatever is driving it and so the same applies to anything driving the passive. In fact with a 10K passive and 5K power amp then at full volume the source would be driving only 3k3.

 

[Nero]

No it doesn't.

Is this the five-minute argument, or are you paying for the full half-hour?

 

[Sue Pertwee-Tyr]

No it doesn't. Most DAC's and the majority of other gear will have op amps at the output and most are specified to work into 600R and will have no issues with 5K. It will likely give problems with a lot of valve sources/pre amps and with some gear there could be bass loss due to the output capacitor in the driving source, if present, being rather too small for driving 5K. A Passive should ideally be 10K or so and this means the passive is in itself a lower than average impedance load for whatever is driving it and so the same applies to anything driving the passive. In fact with a 10K passive and 5K power amp then at full volume the source would be driving only 3k3.

My CD player has a variable output, so could be used directly into the power amps, but I prefer it through the preamp. The output specs for the player are given as:

Output impedance is 52Ω, maximum load is 600Ω (a 10kΩ load is recommended).

Again, I’m not following how 10kR load is recommended if the maximum load is 600R. Is this just an example of engineering English, or am I missing something? And why would they recommend a 10k load if, as you say, the output shouldn’t care?

 

[Arkless Electronics]

My CD player has a variable output, so could be used directly into the power amps, but I prefer it through the preamp. The output specs for the player are given as:

Output impedance is 52Ω, maximum load is 600Ω (a 10kΩ load is recommended).

Again, I’m not following how 10kR load is recommended if the maximum load is 600R. Is this just an example of engineering English, or am I missing something? And why would they recommend a 10k load if, as you say, the output shouldn’t care?

There may be a capacitor in line and this may limit bass into low impedances. Some will have one and some not and the cap, if present, may or may not be a large enough value to give full bass extension into low impedances. There will probably be a 51R resistor after the op amp for stability reasons and they are likely allowing another Ohm for wiring etc. The op amp alone will have output impedance of something like 0.1R. They may also be just being super conservative in that THD typically would be say 0.0001% into 10K but could rise up to a whopping 0.005% into 600R, possibly due to the op amp coming out of class A at that low an impedance. It will probably be absolutely fine driving 5K.
Insufficient current (and we are usually talking a few mA here) would mean the output voltage would not be sustained and there would be gross distortion of the clipping variety.

 

[Alastair]

I'm putting together a system that consists of:
BlueSound Node 2i
Quad 306
Spendor S3/5

As you can see, I do not have a pre-amplifier, but i can connect the Node to the 306 and control the volume 9n the app.

I have a beresford dac with volume control.
Would it be enough or do I need a dedicated pre?

I’d try both options ie BlueSound direct and then integrating the Beresford.

As a side note. I once had a quad elite cd/pre, power amp and electrostatic speakers. All worked fine using the cd pre but I had an urge to try the standalone analogue elite pre and one popped up second hand for an ok price. Conclusions? It was fine with the cd/pre... Naturally at the time, I’d told myself that adding the analogue pre ‘completed’ the system for the quad experience, using all the amp bus connection thingies. And it was a nice system, that I miss to this day. To me at least, it was a stark reminder of what good sounds can be achieved without massive spend. But the cd pre by itself still made some good noises driving the QSP amp directly and I really can’t be too specific on the differences with the standalone pre in or out....they might be obvious to some, I have to raise a hand say though I am not sure.

 

[GT]

I read on the audiophile man a review of the Topping E30 and Paul Rigby said that the dac is excellent but the pre amp section is not good.
How is that possible?

Doesn't surprise me one bit! Compromise, compromise, compromise...

 

[Sue Pertwee-Tyr]

Thanks @Arkless Electronics

 

[James]

In fact with a 10K passive and 5K power amp then at full volume the source would be driving only 3k3.

I'm no expert, clearly, but that seems an awfully low impedance seen by a source component, not all of which would be comfortable driving. The input impedance of my preamp is a much more sensible 50kohm.

Again, I’m not following how 10kR load is recommended if the maximum load is 600R. Is this just an example of engineering English, or am I missing something? And why would they recommend a 10k load if, as you say, the output shouldn’t care?

600R is a tougher load than 10kR, and will draw 16X more current for the same output voltage.

In general terms, output impedance of the driving component should be as low as possible, and the input impedance of the driven component should be as high as possible.

 

[James]

Insufficient current (and we are usually talking a few mA here) would mean the output voltage would not be sustained and there would be gross distortion of the clipping variety.

In my experience, a lower-powered amplifier doesn't have to be driven to clipping into a difficult loudspeaker to sound a bit meh. I suppose the squashed dynamics is a form of clipping, but not of the variety that the average listener can tell compared to say when the volume dial is maxed out.

 

[Arkless Electronics]

In my experience, a lower-powered amplifier doesn't have to be driven to clipping into a difficult loudspeaker to sound a bit meh. I suppose the squashed dynamics is a form of clipping, but not of the variety that the average listener can tell compared to say when the volume dial is maxed out.

We are talking pre amps not power amps. There are no squashed dynamics.

 

[James]

We are talking pre amps not power amps. There are no squashed dynamics.

I know. But aside from a difference in magnitude, it's a similar quandary between a driving and driven part of the chain. Isn't that one of the reasons for having buffering circuits and why, back in the day, impedance matching was a thing?