Croft Polestar III 2 box power amp project

[Jimbo]

A can of worms...

I wouldn't recommend valve regulation of a solid state or hybrid power amp under any circumstances! Disaster! I think you mean regulation of the gain stages in the case of the Croft....? A valve regulated supply couldn't supply the sort of current needed by the output stages As to whether regulated or non regulated is better well that could bring forth a range of opinions! Mine is that regulated is definitely better, and can be a lot better, but there is lots of scope for getting it wrong!
As to valve regulator V SS regulator there is simply no contest technically... A good SS regulated supply is better by an order of magnitude or several than a valve one in every respect. To the point that there can be no technical justification for the use of valve regulation under any circumstances! Now as to whether it has any subjective advantages due to some valve magic being imbued to the actual voltage is something that I'm sure could be debated..... I can't see it myself but admit that due to the technical superiority of SS being crushing when it comes to regulators... I've never tried it. Maybe I'm missing out... who knows? It has occurred to me that a valve regulated supply is still better than an unregulated supply and that the obvious reason they are used in valve equipment is to stick to the notion of all valve, "no SS", "no sand" etc for marketing/brand reasons... call me cynical

I did design and build a bench PSU for testing valve prototypes etc in which I used valve regulation purely for its ability to withstand a dogs abuse electrically! Which it did for many years. For powering really sensitive stuff I sometimes had to put a SS regulator in line after the valve one though, which should tell you quite a lot

Thanks for the comprehensive reply Jez, I think I would agree with you regarding SS regulation vs valve. I believe regulation of a valve power amp helps to control the speakers a tad more?

[worrasf]

Well I'm no electronics designer and have zero knowledge - I spend my hard earned dollar on Croft kit because it is superb value - I don't think anyone would accuse Glenn of building "unnecessary" kit simply to increase profits ( have you seen his wreck of a Porsche?)
All I know is the Croft valve head amp had a massive improvement in SQ when he made me a custom external PSU (supports the Arlkless theory for this kit) but so did the 25 when it went to 25RS spec. I can't directly compare a 7 to 7R but I am in no doubt that the SQ of the 2 box Polestar with all the flying leads etc is a significant increase in all areas over the single box 7 mono. I only paid £350 for the Polestar (somewhat less than the £1400 I paid for the 7 monos) so I don't even have to justify it on cost grounds ( ie. I didn't pay £3K and as such I'm absolutely going to like it).

TBH I have little or no interest in the esoterica of circuit design (I wouldn't expect folk to be overly interested in the design parameters of the titanium plates and screws I use to fix their busted faces) I just go by my ears and buy what I find enjoyable at a price I think is fair which was the original aim of my post.


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[Arkless Electronics]

Thanks for the comprehensive reply Jez, I think I would agree with you regarding SS regulation vs valve. I believe regulation of a valve power amp helps to control the speakers a tad more?

I'm not sure if you mean regulation of the main HT supply which powers the output valves and therefore, indirectly, the speakers or, as in the case of the Croft amps, a regulated supply which powers the stages before the output stage, ie the gain stage....

I can say that I once added 3 separate regulated supplies to a friends Leak Stereo 20 in a cost no object upgrade so that all supplies were regulated. Other mods were also carried out. It was one of the best sounding amps I've ever heard. Period. And driving ESL57's definitely the best!

[Arkless Electronics]

Well I'm no electronics designer and have zero knowledge - I spend my hard earned dollar on Croft kit because it is superb value - I don't think anyone would accuse Glenn of building "unnecessary" kit simply to increase profits ( have you seen his wreck of a Porsche?)
All I know is the Croft valve head amp had a massive improvement in SQ when he made me a custom external PSU (supports the Arlkless theory for this kit) but so did the 25 when it went to 25RS spec. I can't directly compare a 7 to 7R but I am in no doubt that the SQ of the 2 box Polestar with all the flying leads etc is a significant increase in all areas over the single box 7 mono. I only paid £350 for the Polestar (somewhat less than the £1400 I paid for the 7 monos) so I don't even have to justify it on cost grounds ( ie. I didn't pay £3K and as such I'm absolutely going to like it).

TBH I have little or no interest in the esoterica of circuit design (I wouldn't expect folk to be overly interested in the design parameters of the titanium plates and screws I use to fix their busted faces) I just go by my ears and buy what I find enjoyable at a price I think is fair which was the original aim of my post.


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All absolutely fine by me of course. Please don't take an overview of pros and cons of 2 box V 1 box etc as personal in any way

[worrasf]

De nada
I've just replaced the 2 main power switches as one was sticking on intermittently. So for the £350 I paid for the amp plus about £35 on fuses/switches/valve/case screws I am the proud owner of a very fine sounding and likely unique power amp.
Even Glenn declared it a good result - praise indeed


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[Macca]

Does sound like you got a huge bargain there. That's what it's all about.

[worrasf]

Thanks - what is so good (and makes projects like this possible) is that Glenn is always happy to give advice and help even at the weekend for a product I didn't even buy from him - Legend


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