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PostPosted: 13 Jul 2010, 18:57 
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I thought some forum member may like to follow my build of a two stage SE 6AS7 amp. At this point it is in layout stage. Next the drilling and spraying of the top plate. The Base is Mirbeu (Asian wood). I'm am happy to listen to suggestions and comments.

See layout and schematic below:
Attachment:
Pinot-Layout_IIss.jpg
Attachment:
6AS7sch.jpg

Updated 6AS7 SET Tube Amplifier Schematic


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PostPosted: 13 Jul 2010, 21:14 
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Hi Mark, can you swap the rectifier tube with the input tube? This will put the rectifier closer to the transformer (and choke) where it will reduce the length of AC wiring in the amp. It will also get the sensitive input tube away from the big power transformer.
Cheers

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PostPosted: 13 Jul 2010, 21:49 
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Gio - they are just the comments I need. I hated that big ugly 5U4 up front now it can sit back, as you suggested, nearer the power bits. It will stand high so it will not even inflict its evil AC on the OPTs. Heat from it will also be above the OPTs. Win-Win-Win situation. Have the day off on me!!

Upfront now has the cute little driver tube and the sexy looking 6AS7-GREAT!! Just what I wanted. I don't even have to remark the top plate just a mental note which tube is where. See updated layout (now three):
Attachment:
PinotLayoutIIIss.jpg
Attachment:
PinotLayoutTopIIIss.jpg


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PostPosted: 13 Jul 2010, 21:57 
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Can I talk you into putting the RCA inputs at the front of the amp right by the input tube? ;) Where is the volume control going to be? - At the front of the amp will be another reason to move the inputs up front. ;)

BTW - what is the OPT load?
Cheers

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PostPosted: 13 Jul 2010, 22:17 
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Brother I hear you loud and clear but I'm going for form over function here. There will be no volume pot so this amp will always need a preamp or attenuator. I want it to look slick and cute something you would have on you audio shelf. Connections at the back.

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PostPosted: 14 Jul 2010, 07:45 
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What is the OPT Load?

And are those GXSE?


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PostPosted: 14 Jul 2010, 16:51 
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rock4016 wrote:
What is the OPT Load?

And are those GXSE?

Yes GXSE and they are 1.7k into 8 ohms. With my 6 ohm speakers should reflect about 1k to the plate of the 6AS7.

The top plate is drilled now. May have to wait a day or two for the preparation and spraying.

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PostPosted: 15 Jul 2010, 08:19 
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I presume you are not going to use the diode bridge in the schematic. Are you going to use a CLC filter? what cap values are you going to use?


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PostPosted: 15 Jul 2010, 15:19 
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Wow, that is going to look really nice! :thumbsup: You know, if you had enough juice from the power supply you could add a second 6AS7, so then you have one per channel meaning you could get more output power. I have 2 new Rogers 6AS7G's and 2 new Sylvania 6AS7G's. If you wanted to go the double route I could send you one of the pairs depending on where you live. ;)

Other wise it still looks pretty darn cool with just one 6AS7G. :)

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PostPosted: 15 Jul 2010, 16:46 
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rock4016 wrote:
I presume you are not going to use the diode bridge in the schematic. Are you going to use a CLC filter? what cap values are you going to use?

Rectification is going to be tube and CLC filtering. With a RC network for the driver tube as well. Because I want to draw about 100mA through each plate I can only use a 5H choke. In the past I have used 10 and 20H chokes but at lower current. I intend to use a motor cap (30uf) then 100uf after the choke. Being Class A I need a real quiet PS.

CrazzyAbtTubes

It was always my intention to only have two audio tubes. I wanted to build it even smaller but this is about a small as I could get it. I did want tube rec. so again real estate became an issue. If I drop the choke and go for diode rec. and design for lower idle current I may get the size down. I will be using Fostex FE208s in the large back loaded horn boxes so any hum will be heard.

Only way to fight hum is with good filtering. Choke filtering I have found the best and I believe it adds to the over-all sound. So I'm limited to how small I can get this baby down. I may do a bread board version with SS rec. and CRC filtering to see just how noisy it would be.

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