Gromit's music centre...

[Gromit]

Lazy git!

Why thank you.

[Filterlab]

My pleasure.

Richard, I'm still a little confused with using an active pre-amp with an NVA power amp. Help me with this:

My DAC has a variable output which I use as a volume control. It goes straight into my Audiolab power amp in the same way as an active pre-amp would. Why would I need to use a passive pre-amp (or the volume pack) between my DAC and an NVA power amp given that the output voltage is variable anyway? Is it just a case of sensitivity and if so would the same result be obtained by reducing the input gain at the computer end?

Not a challenge, just technical questions to which I don't know the answer.

Cheers!

[WikiBoy]

My pleasure.

Richard, I'm still a little confused with using an active pre-amp with an NVA power amp. Help me with this:

My DAC has a variable output which I use as a volume control. It goes straight into my Audiolab power amp in the same way as an active pre-amp would. Why would I need to use a passive pre-amp (or the volume pack) between my DAC and an NVA power amp given that the output voltage is variable anyway? Is it just a case of sensitivity and if so would the same result be obtained by reducing the input gain at the computer end?

Not a challenge, just technical questions to which I don't know the answer.

Cheers!

Synergy, partnership, empathy.

All problems we face in putting a system together is external interface. All problems a designer is faced with is internal interface. 100 times more inportant than what devices are used.

Many many years ago in a little village called Hatley St George in Cambridgeshire, sitting in a freezing barn of a workshop having split up with my first wife as she wanted me to get a job and I just wanted to build hi-fi and make music. I didn't have the op-amps (TDA1034) I needed for a pre and my test unit was out on loan. Well I needed to test a power amp I had just built so I just put the pot in the box. Well I spent the next day just listening to music and bugger the customers Convinced we were all barking up the wrong tree and simplicity was where reality was I then spent time ripping things out until it all blew up then I backed off and put some things back. Basically I have spent the last 20 odd years doing the same thing (apart from 5 years being so pissed off with the industry I couldn't be bothered), so I recon I have some knowledge on the subject.

A power amp designed for use with an active pre is *not* necessarily compatible with a passive pre-amp. It may appear so and may in reality in musical terms actually be so but that is luck. The same is the case visa versa. Having decided passive was the way to go my power amps designs were changed to balance the interface. Things that need changing are 1 some more gain as the pre-gain is no longer there, only attenuation. 2 remove more feedback in the front end. 3 change loading characteristics to cope with a now variable output impedence from the passive.

This last item is the crunch in terms of compatibility as by lowering the input capacitance so as not to get a "tone control" effect as volume is changed you make the input more susceptable to the inherent instability in some active pres. In other words you do not comp it out. Also it lessens the effect of high capacitance interconnects when using a passive (but this is still *very* important). You also increase the input resistance to balance the pot or sa.

So to cut a long story short - a power amp *designed* to work with a passive can be overloaded and driven into instability by *some* active designs. Inversly a normal power amp designed for active pre can be made to sound dull at low volumes by a passive pre. - interface - interface - interface.

So only solution, break that interface or dependence, by putting a pad (electrical) in between. It will diminish certain parameters in a small way, but not as much as not being there would.

As simple as I can make it I am afraid.

[Filterlab]

Ahhh, thanks for that mate, I understand now. In my mind it was only a question of gain and overload, but I guess that's why I'm a consumer and not an engineer.

[Filterlab]

...We are one of the highest profit industries around, for every £10 spent on components and labour you get another £80 as contribution to manufacturing overheads, then about another £20 for marketing overheads, then if using a distributor another £40 for his pocket, then the retailer another (minimum) £150 for his pocket. £10 to £300 - ridiculous. All approx figures....

Obviously your ratios are narrower than that. Assuming the A80 monoblocks were marketed by a mainstream high end manufacturer (if there is such a thing) what would be their approximate retail price?

[WikiBoy]

Obviously your ratios are narrower than that. Assuming the A80 monoblocks were marketed by a mainstream high end manufacturer (if there is such a thing) what would be their approximate retail price?

At least twice the price. Or if Naim three times the price.

[Filterlab]

At least twice the price.

I see, good value then.

Or if Naim three times the price.

[WikiBoy]

At least twice the price. Or if Naim three times the price.

Whoops! sorry Gromit, I have hi-jacked your thread

[WikiBoy]

I see, good value then.

Value is as value does. I am only talking about price structure and mark up. Value is related to what the item does for its customer. If it is crap for him it doesn't matter how cheap it is.

Once again I want to keep this away from me and my products and more a discussion about principle, otherwise this thread just becomes me finding a new way of slurping the trough.

[Filterlab]

Fair enough matey.

Whoops! sorry Gromit, I have hi-jacked your thread

And I think you should send him some flowers for doing so.