GM70 SET

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steve s
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#226

Post by steve s »

ed wrote:
as it was the first time I'd heard the Beymas in a domestic setting......I'm in the process of getting a pair from Blue Aran so I didn't escape completely unscathed.
i didn't think you liked them that much....

i hear quite alot of speakers, and if i heard anything better i would have them, but i somehow dont imagine i will hear anything better. but they highlight whats driving them.. that can be a good thing or a bad thing.

you should be able to get a discount.. mention that i have bought 2 pairs from them and got a discount..
cheers
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Paul Barker
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#227

Post by Paul Barker »

pre65 wrote:
To be honest, the way I did 833a, and having a lot of the parts "in stock" it was not that expensive to build.:wink:
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IslandPink
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#228

Post by IslandPink »

Paul Barker wrote:..... the GK71not that I heard it. Should it survive 600v 11 watts at 2.55% second harmonic distortion is well good.
I think it would laugh in your face at those levels, Paul .

Ed - now you've let yourself in for the problem of how to put something underneath the Beyma that will keep up with it ....

:D
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#229

Post by simon »

Glad I got my coppers before you lot buy them all up! :-)
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#230

Post by simon »

Nick wrote:Personally I think they are every bit as good as vt4c. Maybe not as good as the 211E that Paul has one of, but I don't know. My current 211 is not as good as the 211 I had before, but that was impractical, 76 into 45, both stages shunt regulated. IT to 211 grid, 211 stage 1300v HT choke input, MV rectifiers.
I think this is what really surprised me, the driver is just a choke loaded trioded 12GN7. Nothing exotic at all.
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ed
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#231

Post by ed »

steve s wrote:
i didn't think you liked them that much....
I've had am itch in my wallet ever since I heard the heils..not sure what I've said that made you think I wasn't hooked.....I love them.

I did say a while back that I wouldn't be building another valve amp, so that helped in stopping me ordering some gm70s this afternoon....that and the fact that I've got a box full of sv572s and sv811s. They'd sulk if I fell in love with somebody else.

re the conversation about your 2 regulated power supplies, one for the front end and one for the output...I'm still thinking that having an srpp or aikido on the front end achieves a similar thing.....It's not something I've seen mentioned but I have an interest to find out more.
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Paul Barker
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#232

Post by Paul Barker »

ed wrote: re the conversation about your 2 regulated power supplies, one for the front end and one for the output...I'm still thinking that having an srpp or aikido on the front end achieves a similar thing.....It's not something I've seen mentioned but I have an interest to find out more.
I was also thinking that.

Stick with Aikido I would say.
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Nick
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#233

Post by Nick »

Yep. But remember you need gain as well.
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ed
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#234

Post by ed »

Nick wrote:Yep. But remember you need gain as well.
I'm not sure if that was related to my aikido post.......

if it was you're teasing me...my aikido is exactly in the right area for the way Simon configured his GM70.....

attached the last set of figs when I moved to smps/dc heating....a few anomolies which I'll chase sometime soon...

c'mon, I really don't want to buy into another valve project.....but I am getting curious...sassenfrassincursinclaudehopper
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Nick
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#235

Post by Nick »

Yep I meant the use of the aikido with respect to not using complex supples. Assuming my point about getting the best from it. You are looking at something in the order of 50v rms drive. And so that alone means imho you are looking at a gain closer to 100. That gets harder with the aikido. And you want to like the sound of the driver. Not just swing the volts.
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#236

Post by simon »

I measured the gain of the 12GN7 at 39 using a 1kHz sine wave. The GM70 is biased at 45V so I could perhaps handle a little more gain. An ECC83 would give nearly 50 depending on the second valve in the Aikido, beyond that there's pentode Aikidos?
steve s
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#237

Post by steve s »

ed wrote:
c'mon, I really don't want to buy into another valve project.....but I am getting curious...sassenfrassincursinclaudehopper
I emailed Pieter last night for a quote for some new transformers...

This affliction is a bugger
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pre65
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#238

Post by pre65 »

simon wrote:I measured the gain of the 12GN7 at 39
According to P Millett 39 is what I should be getting on mine (as a triode) with a CCS load.

http://www.pmillett.com/pentodes.htm
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ed
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#239

Post by ed »

weeell...looking at sheet 2 on my attachment(which was the one I was referring to, apologies if that wasn't obvious) I'm getting a gain of 37. Broskie's chart says 39x0.99 for my valve set so thats not too bad.

So that gives me 50+ volts RMS at max input...which admittedly I won't go near, but that would I think be more than adequate for GM70....the more people that question this, the more likely I am to try it...you buggers!

fwiw I first tried 12hg7 with sv572 back in 2007/2008. I can't find the thread in question when I was asking about setting up the pentode but in the end I went with Pete Millets guide. I didn't like it half as much as the aikido...

resistance is futile.......
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#240

Post by simon »

steve s wrote: I emailed Pieter last night for a quote for some new transformers...

This affliction is a bugger
I take back what I said about this being a cheaper hobby than golf.... :-D
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