Croft Polestar III 2 box power amp project

[worrasf]

I recently acquired this Croft Polestar III 2-box power amp.

Having shared some photos with Glenn he tells me that this is a true "one off" unique amplifier built in 2006 as a company development amp.

It is apparently of uber high spec featuring not only a 2-box massive external PSU but also Eichmann speaker posts and doubled up transformers and a copper chassis for the amp section. The flying power leads are a sight to behold.

Glenn reckons it would have sold for around £3K back in the day.

It looks like it was stored in someones' shed for yonks but apart from a thin layer of dust it all looks to be OK. Glenn reckons shouldn't need anything doing to it.

However, it came sans 5965 valve and the main power fuse was missing and the fuse holder head "cheesed" where it had clearly been abused in the past. One of the other fuses was also the wrong spec so I'm not fully confident that it will be a runner

I've managed to repair the fuse holder and have got the correct fuses and a NOS GE 5965 on order so hopefully will be able to test it over the next few days.

Assuming it powers up and doesn't blow my speakers then It will be very interesting to compare with my Croft 7 mono blocks.

More to follow - good or bad

Steve

[The Black Adder]

Very nice find. Never heard that type but I can only think that it would be rather special. But I feel it's rather a different beast than the 7 mono's as it uses a 5965 which is a very different sounding valve than a ECC82/83.

[worrasf]

Glenn says will also take an ECC81,
There's a feedback comment I came across on one of the US valve sites that an RFT 12AT7 sounded more open and less warm than the GE 5965 that the guys Polestar 1 came with so even here there's room for tube rolling


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[The Black Adder]

Wow.. how cool.. a very flexible amp then.

[Firebottle]

It will be very interesting to compare with my Croft 7 mono blocks.

Keep us posted on this, very interested to hear your thoughts

[worrasf]

Wilco - I've also ordered an RFT 12AT7 (ECC81) so assuming I can get it running then I can also experiment with 5965/ECC81


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[DSJR]

Not my expertise, but please check the 12AT7 is a pukka drop-in valve replacement. I seem to remember the heater? current is higher, but obviously Glen will advise as he knows the current ratings of this part of the circuit.

Sorry if it's granny sucking eggs...

[worrasf]

Yep already checked with the maestro - he wanted to see photos of the valve base components and having done so told me will run 5965 and also ECC81


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[worrasf]

Very nice find. Never heard that type but I can only think that it would be rather special. But I feel it's rather a different beast than the 7 mono's as it uses a 5965 which is a very different sounding valve than a ECC82/83.

Forgot to mention earlier that Glenn fitted my 7 mono blocks with JJ ECC99 gold pins not ECC83's

Steve

[worrasf]

So I've now got this up and running - just needed new fuses and a valve. I have to say it sounds utterly stunning. It took about 30 mins to warm up/stabilise before the true character declared itself.

The soundstage is immense and very tightly focussed - bass is hugely deep and tuneful - I had to turn the gain on the REL subwoofer down a notch (I set this up until I can just hear the bass line and then up one notch so it just supports the main speakers).

It is a very dynamic presentation- PRaT are spot on for my taste. The additional power reserves over the 7 monos is evident in the iron grip on the speakers.

Tonal balance is slightly warm of neutral (maybe an ECC81 would change this a tad) - the clocks and bells on dark side have never sounded so clear and vibrant the final 2 "tangs" are awesome.

Compared to the 7's there is perhaps a very slight blurring of steel brush and cymbals which may change with a different valve type but it's of little consequence as the overall sonic picture is just so convincing and enjoyable.

Trawling the web I've not come across any references to a 2-box Polestar- all the images I've seen of the rear panels show series 1 through 3 but mine shows 1234.
Glenn was unsure whether it could be called a Polestar 4 or not.

I can not see me going back to the 7 monos anytime soon after experiencing what this 2006 amp can do so if the Polestar proves reliable they may be looking for a new home.
This has to be the best £350 (plus fuses and valve) bargain ever.

Steve


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