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45 SE amp
45 SE amp
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Old 1st March 2019, 01:54 PM   #1
Raaf61 is offline Raaf61  Netherlands
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Default 45 SE amp

I am planning to build a 45 se amp .
As I would like to avoid to use Elco's my intention is to use negative bias to avoid the use of a bypass elco as is used with fixed bias at the cathode .
So far so good .

But I allso would like to use ac heating and there I seem to get stuck .
I can't find any suitable diagrams on how to do this .
So It makes me wander if this set-up is possible at all ?

Last edited by Raaf61; 1st March 2019 at 03:21 PM. Reason: typo
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Old 1st March 2019, 02:24 PM   #2
merlin el mago is offline merlin el mago  Europe
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At least make the schematic you want to use it. Driver would you use, etc.
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Old 1st March 2019, 02:39 PM   #3
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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If you want to use no electrolytics, there is a trick consisting in using positive voltage feedback from cathode output to cathode drive, only resistors are needed. Langford Smith´s Radiotron touch this point, and in some other authors
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Old 1st March 2019, 02:51 PM   #4
mbrennwa is offline mbrennwa  Switzerland
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45 SE amp
I was working on a 45-SE a while ago (but the project got stuck due to lack of time). I got the bug from this thread. My last design version is in post 116. The driver is direct coupled to the 45 grid, and there is no electrolytic cap anywhere in the signal. The circuit could be done with film caps everywhere. Maybe this thread + design is useful for you.
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Old 1st March 2019, 03:13 PM   #5
Raaf61 is offline Raaf61  Netherlands
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Sorry people,
I was making a thinking error on how to ever measure the current over a humpot ....

I just have to put a 1 ohm resistor in series to ground


Btw, I don't mind using caps in the signalpath, in fact I was planning to use a coupling cap between the driver (C3M) and the 45
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Old 2nd March 2019, 01:04 PM   #6
Raaf61 is offline Raaf61  Netherlands
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This is what I have in mind
Click the image to open in full size.
C1 & C2 are just an idea, good idea or not ?

Last edited by Raaf61; 2nd March 2019 at 01:18 PM.
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Old 2nd March 2019, 02:35 PM   #7
Nightpuma is offline Nightpuma  Norway
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Look at Thomas Mayers 46 amp. AC heating and no elcos

VinylSavor: Single Ended Amplifier Concept, Part 7
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Old 2nd March 2019, 02:50 PM   #8
mbrennwa is offline mbrennwa  Switzerland
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45 SE amp
Quote:
Originally Posted by Raaf61 View Post
C1 & C2 are just an idea, good idea or not ?
What bias current are you aiming at? You might have to adjust the values in the cathode resistor network.
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Old 2nd March 2019, 02:57 PM   #9
Raaf61 is offline Raaf61  Netherlands
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Yes thank you Nightpuma, I've came across that one.
It definitely looks promising only it has cathode bias.
VinylSavor: Single Ended Amplifier Concept, Part 7

And the placement of those 4 30uF's is a new concept to me.

I just wish my power transformer arrives soon so I can start building

Quote:
Originally Posted by mbrennwa View Post
What bias current are you aiming at? You might have to adjust the values in the cathode resistor network.
According to the data-sheet 39mA @ 300V
I'm going to apply negative bias voltage
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Old 2nd March 2019, 04:29 PM   #10
jazbo8 is offline jazbo8
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