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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #6451  
Old 06-21-2021, 08:37 PM
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straitwire straitwire is offline
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Hey Isaacc7, the screen grid voltage on a Pentode configured FireBottle is regulated so the B+ stays the same regardless of which rectifier tube you use.
The plate voltage on the input tube is also regulated.
The B+ voltage changes on the plate of the output tubes when you change rectifier types.
The tube charts are in a notebook at the shop so I don't have access to them right now.
Can you post a picture of the tube chart you have?
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  #6452  
Old 06-21-2021, 09:02 PM
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straitwire straitwire is offline
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I had to do some checking, the nominal regulated B+ voltage on the screen grids is 260 volts.
And as I mentioned before, this stays the same regardless of which rectifier you use.
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  #6453  
Old 06-21-2021, 09:32 PM
Isaacc7 Isaacc7 is offline
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Quote:
Originally Posted by straitwire View Post
I had to do some checking, the nominal regulated B+ voltage on the screen grids is 260 volts.
And as I mentioned before, this stays the same regardless of which rectifier you use.
Thank you so much! Glad to hear the screen grids are kept at 260, that means the 807 is fine. You say the plate voltage changes on the output tubes as you change rectifiers, is the value consistent or does it vary depending on the output tube? I know just enough about tube amps to be dangerous, sorry if these are stupid questions. I love playing around with different tubes in this amp.

I'm curious about the input tube. If it always gets the same amount of juice which of the recommended tubes are closest to ideal? Don't all three vary by more than just mu?

If I've managed to do this properly this will show the chart that Dennis sent me.

Edit: Can't seem to embed the image. Is there a preferred image poster for this site?

Here's an Imgur address: https://imgur.com/a/ExMul8I



Thanks again!

Last edited by Isaacc7; 06-21-2021 at 11:25 PM.
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  #6454  
Old 06-22-2021, 03:35 PM
FloridaBoy FloridaBoy is offline
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Howdy Straitwire,

I'm considering changing the SoZo caps in my 45/2A3 amp. My questions are what are the values and are all four for the output tubes? I can't see the values without twisting the caps.

Thanks,

Les
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  #6455  
Old 06-22-2021, 05:08 PM
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straitwire straitwire is offline
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Hey FloridaBoy, the coupling cap values tend to be .22 or .47 but depending on the circuit they can be other values.
If your input tube is 8 pin then the plates are pin 2 and 5.
The coupling caps are connected to these pins usually with a wire.
There are only two coupling caps unless Dennis paralleled some.
Post a picture if you can and maybe I can tell you what you have.
But If you twist them a little bit it won't hurt them.
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  #6456  
Old 06-23-2021, 06:17 PM
FloridaBoy FloridaBoy is offline
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They appear to be paralleled. Just changing caps for fine tuning.
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  #6457  
Old 06-23-2021, 06:56 PM
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straitwire straitwire is offline
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Which SoZo caps are you interested in?
The caps I have seen (Blue and Mustard) top out at .1 mfd
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