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New project: balanced tube mc phono preamp -
New project: balanced tube mc phono preamp -
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Old 21st October 2018, 08:57 AM   #1
janho12345 is offline janho12345  Germany
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Default New project: balanced tube mc phono preamp -

After completing my last project, ( Building with the Soekris dam1121 and Building with the Soekris dam1121 ) with great help from many of you in this community, I’m starting with a scratch and a design by Broskie.

I want a simple design, without a big part list.

This is Broskies simple balanced phono preamp:
Click the image to open in full size.

That can be found here:
Still More Phono Preamps


My simplistic mind brought to me that it would be just perfect, to use a 1:10 step up as Input transformer 12ax7 as gain tubes, ecc81 as cathode follower and as an output transformer a transformer voltage control, (by sowter with +6 and +12db tab) wich will give up to 1.225V wich is just what my power amp needs.

What do you think?
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Old 21st October 2018, 09:03 AM   #2
reinhard is offline reinhard
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Mc with a 1:10 input trans and only one gain stage?

Think you need a step up as output transformer,

Reinhard
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Old 21st October 2018, 09:19 AM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Where is the grid leak resistor in the first stage?
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Old 21st October 2018, 09:22 AM   #4
reinhard is offline reinhard
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Quote:
Originally Posted by JonSnell Electronic View Post
Where is the grid leak resistor in the first stage?
Grids are floating, see original article.
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Old 21st October 2018, 11:39 AM   #5
janho12345 is offline janho12345  Germany
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Quote:
Originally Posted by reinhard View Post
Mc with a 1:10 input trans and only one gain stage?

Think you need a step up as output transformer,

Reinhard
With an cartridge of 0,5mV

1:10 transformer -> 5mV
Ecc83 gain about 80 -> 400m
Cathode follower gain 0.9 -> 360mV
TVC with gain Tab +12db -> 1,4V

Not too bad is it?
Is the transformer not also getting 2x 360mV?
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Old 21st October 2018, 12:16 PM   #6
reinhard is offline reinhard
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And where are the -20 dB for the RIAA - network?

Reinhard
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Old 21st October 2018, 12:17 PM   #7
janho12345 is offline janho12345  Germany
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And where are the -20 dB for the RIAA - network?

Reinhard
There was my mistake!!!!

What would you suggest?
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Old 21st October 2018, 12:44 PM   #8
reinhard is offline reinhard
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2.nd amplification stage, what else.

Reinhard
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Old 21st October 2018, 12:54 PM   #9
janho12345 is offline janho12345  Germany
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Quote:
Originally Posted by reinhard View Post
2.nd amplification stage, what else.

Reinhard
Lundahls LL1943 is a MC input with 1:16 or 1:32 wouldn’t that cover for the loss of the RIAA?

A second gain stage would mean many many more parts! :/
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Old 21st October 2018, 01:09 PM   #10
reinhard is offline reinhard
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With 1:32 you get 10 dB more, not enough.

Redesign the cathode follers to a second diff-amp.

Reinhard
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