Passive Pre beaten at last

[tubehunter]

Hi All,


Well after living and swearing by a Passive pre I've finally built an Active pre that proves me wrong.

I recently moved to using the Quad 405 amplifiers as my Kef 105 require a power rated between 40 to 200 watts, my valve amp was just not powerful enough.

Also there's the issue of the Quads inverting the phase.

I designed a simple SRPP circuit using the 6n6p this inverts the phase and brings some awesome bass and dynamics.
I regretted selling the first prototype to someone here so had to build myself another.
This time I went for the two box approach which is popular with higher end designs, makes sense to separate the noisy AC environment from low level signal one.
I've must say those new Mundorf MCap EVO Oil sound very good.

Anyway some pictures

[Firebottle]

Very nice. Versatile move having built in the Active/Passive switch

Can't quite make it out, is the stepped attenuator on the output of the SRPP stage?
What level of gain do you get?

Alan

[tubehunter]

yes I still wanted to be able to run passive easy to compare.

the stepped ladder pot is on the output to give great signal to noise and to give the dac direct input to grid an easy load.

I don't need gain as the quads are so sensitive.

duncan

[The Barbarian]

Quite a few SRPP Kits on Auction

[Barry]

If you are worried by the phase inversion of the Quad 405, why don't you simply reverse the speaker leads?

[DarrenHW]

Looking good Duncan

I regretted selling the first prototype to someone here so had to build myself another.

You're making me feel bad, glad you've built a replacement.

This time I went for the two box approach which is popular with higher end designs, makes sense to separate the noisy AC environment from low level signal one.

Would you say this made a significant difference?

[tubehunter]

If you are worried by the phase inversion of the Quad 405, why don't you simply reverse the speaker leads?

Hey now that's too easy

I also wanted to explore what an active pre could do partnered with the Quads

[The Barbarian]

Im just puzzled about the Passive beaten at last comment tbh!

[walpurgis]

Im just puzzled about the Passive beaten at last comment tbh!

Yes, I wondered a bit. Most passives I've used (quite a few) have been a bit uninspiring.

[CageyH]

Isn't a passive pre just a bunch of wires and a switch?