Has anybody built the Matthew Reidsma Experimental 45? - diyAudio
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Old 22nd January 2004, 12:40 PM   #1
arnoldc is offline arnoldc  Philippines
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Default Has anybody built the Matthew Reidsma Experimental 45?

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has anybody heard one? i wonder why such a simple circuitry did not become popular?
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Old 22nd January 2004, 03:56 PM   #2
qwad is offline qwad  Australia
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pretty obvious if you look at the o/p tube and it's availability / price and the o/p power that can be excpected from one which if my memory serves me right is miniscule even back in the days of sound practices they were a right rare tube to get even used the price was pretty substantial [ if you could find one!] cheers TC
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Old 22nd January 2004, 09:23 PM   #3
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Default interesting circuit

Since the voltage regulator isn't perfect, some positive feedback is applied.
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Old 23rd January 2004, 01:37 AM   #4
arnoldc is offline arnoldc  Philippines
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guess i just have to make one
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Old 23rd January 2004, 03:40 AM   #5
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Default Be interesting.

Would be interesting to see how it sounds. Simple circuit and all.
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Old 23rd January 2004, 06:56 PM   #6
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Default can this be scaled up?

what is the possibility of it being scaled up to say a 300B circuit using parallel VR tubes in the cathode?

any advantages to this versus say a choke or CCS?

Thanks!
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Old 23rd January 2004, 08:41 PM   #7
RS is offline RS  Germany
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Default Re: can this be scaled up?

Quote:
Originally posted by AudioGeek
what is the possibility of it being scaled up to say a 300B circuit using parallel VR tubes in the cathode?
No go! You can use voltage regulators in series, but not in parallel.

Regards

Ralf
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Old 23rd January 2004, 09:04 PM   #8
qwad is offline qwad  Australia
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well if you can find some used 45's at a reasonable price, it is a very simple circuit and using the hammond 125 e op xfrm it may be a nice and simple amp to build BUT I would use the hammond 125 se as being a better choice and by all accounts performs quite well in 2a3 se circuits. cheers TC
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Old 24th January 2004, 12:07 AM   #9
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Default Re: can this be scaled up?

Konnichiwa,

Quote:
Originally posted by AudioGeek
what is the possibility of it being scaled up to say a 300B circuit using parallel VR tubes in the cathode?
Not directly, but by combining a VR Valve AND something like a KT88 you can make a "power shunt regulator that keeps the voltage on the KT88 Anode quite constant. Then apply a choke with an apropriate series resistorto load the driver and bias the output valve, voila, done. But a resistor/capacitor parallel combo in the output cathode will do not really any worse, if the capcitor is high quality or perhaps WE/UP connection is employed.

Sayonara
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Old 25th January 2004, 05:38 PM   #10
marz.tv is offline marz.tv  Sweden
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I like the idea of using VR tubes in cathodes. Does anyone know any other circuits with this approach?
(I have only 2 45's. Ancient used ones. Wouldn't dare risking them in anything experimental ^^ )
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