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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 16 Aug 2018, 16:21 
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Location: australia
I am concerned about the 450v rating of 47 and 220 uF psu capacitors. I see others use 500 or even 630 v caps here. If not misplaced are there any suggestions for alternatives I could use? I'll check with the local Jaycar as well.

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PostPosted: 16 Aug 2018, 18:24 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
What is your HT?

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PostPosted: 16 Aug 2018, 22:52 
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The seller recommends a transformer with 320v. After rectification I'm not sure what that will come out at.

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PostPosted: 17 Aug 2018, 18:36 
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Attachment:
6sn7-300b pcb amp-august2018.pdf
[attachment=0]6sn7-3
Woodo wrote:
Please refer to updated schematic - comments welcome. Probably a bit rough.
Slight edit


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PostPosted: 19 Aug 2018, 16:38 
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Added hardware to box. Need to figure how to attach filament transformer underneath but it's smaller holes are narrowing choices.


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PostPosted: 01 Sep 2018, 06:08 
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Plodding away connect wires to the road and chassis. One wire not completely obvious where to put is the the centre tap for the 6.3 volt heaters for the 6sn7's. I read that should connect to ground. Should it go to chassis safety ground in my case? Any advice appreciated. Also there are some white/blue wires on the output transformer labelled "screen" which don't have an obvious place to go. Would that be necessary for a UL amplifier? After that I'll work on how to make 5 volts from the 6 volt winding from the little hammond transformer. Have spoken to a guitar amp guy who offered to help check if it's safe to turn it on once ready. Cheers.


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PostPosted: 01 Sep 2018, 20:16 
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Woodo wrote:
The seller recommends a transformer with 320v. After rectification I'm not sure what that will come out at.

not sure how it works but from reading the posts there is about 40 v loss due to the 5u4g but the rectification of the ac give a dc voltage of root 2 multiplied by that. this gives around 390v dc??

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PostPosted: 08 Sep 2018, 03:40 
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updated pic and first time to put valves / tubes in. the 300bs are from china, the newish 5u4 GB came from northern New South Wales from memory, the 5as4 is an AWA model i bought from a guy in Maryborough, Queensland. i bought some used 6sn7 s of ebay from a USA seller. i got another set of 6sn7s but actually are marked 6h8c and look old and well used. I hope they work! i think they are the same as 6sn7 but will check.

I wish I had the knowledge and fortitude to turn it on safely but i will go the safe route and acquire some help to check things over. thanks for the encouragement so far. regards.

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PostPosted: 08 Sep 2018, 04:20 
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pics as promised. there are a few wires i haven’t trimmed yet. the transformer includes 320 v (used here) and 380v wires. 320v was recommended but i see higher voltages are used in other projects on the forum. There are UL wiring too not used.


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PostPosted: 11 Sep 2018, 16:28 
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The recommendations from Matt were followed regarding location of signal ground in the following link.
viewtopic.php?f=9&t=4632&start=50

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