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Old 12th October 2011, 04:08 PM   #11
kevinkr is offline kevinkr  United States
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Originally Posted by directdriver View Post
What's wrong with using pentode? Have you listened to it or an amp using pentode driving a triode? Didn't the Western Electric 91 use the same thing? If designed right, I don't see any reason to object to it.

Depends a whole lot on the pentode used, some of the more modern high transconductance types are quite good at it, the concern is always going to be the effect of output tube miller capacitance on the HF response.. High transconductance pentodes with modestly sized plate resistors running at high currents should slew well enough at high frequencies and shouldn't have a problem to well beyond 20kHz..
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Old 28th July 2012, 04:15 PM   #12
maximka is offline maximka  Russian Federation
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Tell those who have wills voltage characteristics 717A
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Old 19th August 2013, 08:37 PM   #13
Rewind is offline Rewind  Sweden
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Originally Posted by ThorstenL View Post

I have decided to post the Schematic in another on-line group with pretty complete detail, so also find it here, in context. It is basically 99%, one or two values may be slightly different, but not much.

If you want to copy the Amplifier you do of course need the iron, considering fit/finish, component quality and inclusion of NOS Valves I'd think it's worth giving Yamamoto the business and buying the Kit if you want to build the Amplifier, a Set of Tamura Transformers and a nice case plus the valves will take most of the cost of the kit.... ;-)

Can't really afford a $2400 amp as a student. What should I look for if I want to find similar irons?
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Old 19th August 2013, 08:59 PM   #14
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Check out Lundahl to see what kind of "budget" transformers they recommend.

Lundahl Transformers
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Old 19th August 2013, 09:04 PM   #15
Rewind is offline Rewind  Sweden
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Lundahl - budget?

The thing is I am a noob when it comes to transformers. I see units like "CT" and I have no clue what is going on. What values should the transformers in the Yamamoto A-08 have?
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Old 8th October 2015, 08:08 AM   #16
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Last edited by QSerraTico_Tico; 8th October 2015 at 08:10 AM.
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Old 8th October 2015, 08:21 AM   #17
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Originally Posted by codyzox View Post
I need it also...Can someone post details with original shematic and parts list (also from which manufacturer are parts exactly). It would be a great help, not just for me i think...Big thanks in advance...
Lot of info here:
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Old 9th November 2015, 03:06 AM   #18
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Quick question here: what is the original Tamura output transformer model used in Yamamoto A-08/s? And is there any replacement from Lundahl amorphous core lineup? Thanks.
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