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LS50 passive speakers, amplifier

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LS50 passive speakers, amplifier

Postby Trevor Johnson » Sun Nov 29, 2020 8:35 pm

I have followed Phil Ward's excellent reviews and in-depth analyses of speakers, and was struck by his thoughts on passive speakers/crossovers in the latest "Why I Love' column.

There are some great deals on KEF LS50 passive speakers, (not the Mk II Versions) at present) and I am wondering what forum members would recommend for power amps. In fact I think Phil has some passive LS 50s so his thoughts would be very valuable, please!

Nothing vintage, thanks, as I have a few Quad amps which I have rebuilt: 303, 405, etc..

A Bryston 2.5b or 3.0b looks good. Why not an active LS50? Well, Mrs J and I are moving soon and there will be space for some biggish speakers, Spendor or B&W. (I still use my BC1s almost daily). So I will need a very good power amplifier.

A quick note: I have mixed/edited/tracked on headphones since the early 70s and cannot change to doing this with speakers. These speakers are for playback and general, not 'monitor', use.

P.S. I started very young! (early 70s).
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Re: LS50 passive speakers, amplifier

Postby James Perrett » Sun Nov 29, 2020 11:39 pm

Have you got a spare non-working Quad lying around? If so, you could do what I did and remove the insides and fit some Hypex modules. It cost me around £250 for 2 Ucd180 power amp modules and a power supply.

You can also buy complete Hypex based power amps from people like Nord

https://www.nordacoustics.co.uk/product ... -in-silver

This is the bottom of their Hypex range - you can spend more if you want.
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Re: LS50 passive speakers, amplifier

Postby Trevor Johnson » Sat Dec 05, 2020 6:37 pm

Thank you James, and I do apologise for the delay in replying.

My Quad 405 MkI, which I have 'upgraded' to a Mk2.5 is still going well. But I shall look for a non-working 405 to convert to Hypex - a great winter project!

Thanks again.
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Re: LS50 passive speakers, amplifier

Postby James Perrett » Sat Dec 05, 2020 7:38 pm

It doesn't have to be a Quad - although I found I could mount the modules without the need to drill too many more holes. I had also toyed with the idea of buying a really cheap power amp from somewhere (Thomann were selling some at around £60 a while ago), gutting it and then mounting the Hypex modules. However the Quad was suffering from a noisy transformer and one of the amp modules was becoming noisy so I went with repurposing the case and some of the connectors from the Quad but replacing the input connectors with TRS jacks.
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Re: LS50 passive speakers, amplifier

Postby Trevor Johnson » Sat Dec 05, 2020 8:03 pm

I've used Metcase for both audio and RF projects before, great quality, moderately expensive. https://www.metcase.co.uk/en

In fact I have been thinking about building a power amp into a similar Metcase that my Self designed, Elektor published, pre-amplifier, is built into. I think all the Hypex amps are Class D, looking at their website. I have experience of using Class C at RF, though.
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