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Power Tx question - Dumb question [message #31157] Fri, 10 June 2005 10:51 Go to next message
colinhester is currently offline  colinhester
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Illuminati (3rd Degree)
I'm looking at an 811 SE schematic (Vacuum Tube Valley, Issue 5, pg. 22) that calls for a 800VCT power transformer. Should I be looking for a 400-0-400 or an 800-0-800 transformer?.....Colin

Re: Power Tx question - Dumb question [message #31158 is a reply to message #31157] Fri, 10 June 2005 12:35 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Jeez; didn't you just build a state of the art tube pre-amp? The 800v is the entire coil, centertapped would indicate 400-0-400; just like Guinevere, 350-0-350. Did you get the 45 schematic from SP?

Re: Power Tx question - Dumb question [message #31159 is a reply to message #31158] Fri, 10 June 2005 13:25 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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Man, ask a simple question......

Which of the variations of the 45 would you consider?.....Colin



Re: Power Tx question - Dumb question [message #31161 is a reply to message #31159] Fri, 10 June 2005 14:50 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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You know I am probably not qualified to answer that; I never really spent serious time with either amp using that tube. You should look at the SP amp though; because as Akhilesh says in his post, the DRD is just a way to try and save on OPT's. And I tend to agree with his point. The SP is more like a normal design and heck; if it is good enough for Gordon Rankin.
There is no free lunch.


Re: Power Tx question - Dumb question [message #31162 is a reply to message #31161] Fri, 10 June 2005 15:15 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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I'm not going DRD. This is a straight 811 SE using a 6EA7 as the driver. There is one cap in the signal path, and the price of the OPTx (Electra Print MT5KB) about made me choke; so, there is no cutting corners to save money. What's killing me right now is finding the 20 (10 per channel) 10mF 660V oil caps for the power supply.

Am I really going to build this? I don't know. I want to get a firm grip on the price before I commit.

I will look over the SP amp more, but the 811 I'm considering is about as dead-nuts simple as you're going to find.

BTW. The 811 amp is listed in VTV issue 5.....Colin

Re: Power Tx question - Dumb question [message #31163 is a reply to message #31162] Fri, 10 June 2005 19:28 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Thanks; I am going to fish that issue out and check up on it. I agree; at this point I am open to suggestions. And you know what? It is nice and relaxing just checking out different schematics and pondering a build.

Re: Power Tx question - Dumb question [message #31164 is a reply to message #31163] Fri, 10 June 2005 20:19 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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I think once you read the article and see the schematic, you'll know why I'm pretty hot on this particular amp. The design is about as simple as one can get and still have a functioning amp. There are four resistors and one cap in the signal section; however, there is a ton of iron and many capacitors in the power supply.

I really wish you would look this over and tell me what you think. It's nothing fancy; it's just the best of 1930s technology......Colin

Re: Power Tx question - Dumb question [message #31165 is a reply to message #31164] Fri, 10 June 2005 20:45 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
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Good stuff. Little late now but tommorrow I'll definately look it over. Whats the rating 10 watts or so?

Re: Power Tx question - Dumb question [message #31166 is a reply to message #31165] Fri, 10 June 2005 22:14 Go to previous messageGo to next message
colinhester is currently offline  colinhester
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It's kind of confusing how the power ratings are stated, but, yes, it should be around 10 watts peak and 7 watts continous.....Colin

Re: Power Tx question - Dumb question [message #31168 is a reply to message #31157] Fri, 10 June 2005 23:18 Go to previous messageGo to previous message
Forty2wo is currently offline  Forty2wo
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Hi Colin.
I am siting on a Pair of new 400-0-400 transformers send me a copy of the schematic or a list of the volts and amps. Maybe I can Help...John

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