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decky 23rd April 2011 08:18 AM

The PSU version is V2 - that is written on the PCBs - the mains voltage is 240V nominal - usually around 246V. The secondary voltages at the input are 6VAC. This yields with 6V voltage drop across the regulator, which is not a huge thermal load I would imagine. On top of that 2A3 heater should pull only 2.5A at the heater and the LM1084 are rated at 5A. In theory everything should work fine but it is not. Could the valves be out of spec that much to cause this?

ThorstenL 23rd April 2011 11:57 AM

Hi,

Quote:

Originally Posted by decky (Post 2548167)
This yields with 6V voltage drop across the regulator,

It is a bit much, try a 0.33 Ohm / 9W resistor in series with the heater winding.

Ciao T

pieter t 23rd April 2011 12:16 PM

Quote:

Originally Posted by ThorstenL (Post 2423361)
Hi,



Yes, it does. Any true single stage tube circuit inverts polarity...

Ciao T

Really ? :(

ThorstenL 23rd April 2011 01:19 PM

Hi,

Quote:

Originally Posted by pieter t (Post 2548283)
Really ? :(

Yes, really. Same also for transistors and J-Fets.

Ciao T

pieter t 23rd April 2011 01:44 PM

Quote:

Originally Posted by ThorstenL (Post 2548317)
Hi,



Yes, really. Same also for transistors and J-Fets.

Ciao T

And what about grounded grid stages?
And triode cathode followers, are these inverting too? :(

ThorstenL 23rd April 2011 02:18 PM

Hi,

Quote:

Originally Posted by pieter t (Post 2548332)
And what about grounded grid stages? And triode cathode followers, are these inverting too? :(

Ok, Cathode followers do not invert, they also provide no voltage gain.

Grounded grid does not invert, but the very low input impedance makes them essentially unusable in audio, in fact you generally see the grounded grid stage combined with a cathode follower in audio. Of course, now it is no longer single stage AND no longer single ended, it has actually become a differential (Push-Pull) Amplifier (and in the most prominent example with a ton of loop negative feedback added to the mix).

So let me qualify that as:

"All Single Stage Gain circuits invert except grounded Grid/Base/Gate which are uncommon in audio and nearly never used as single stage in audio".

Ciao T

pieter t 23rd April 2011 03:07 PM

Quote:

Originally Posted by ThorstenL (Post 2548356)
Hi,

Ok, Cathode followers do not invert, they also provide no voltage gain.


Ciao T

Right, but your initial statement was not correct.

pieter t 23rd April 2011 03:12 PM

Quote:

Originally Posted by ThorstenL (Post 2548356)
Hi,

Grounded grid does not invert, but the very low input impedance makes them essentially unusable in audio........

Ciao T

Also this is an oversimplification: I remember Remco Stoutjesdijk's excellent tube I/V stage which was a grounded grid stage.
Also check this forum for numerous grounded gate I/V converters (Nelson Pass and others).

ThorstenL 23rd April 2011 04:24 PM

Hi,

Quote:

Originally Posted by pieter t (Post 2548394)
Also this is an oversimplification: I remember Remco Stoutjesdijk's excellent tube I/V stage which was a grounded grid stage.
Also check this forum for numerous grounded gate I/V converters (Nelson Pass and others).

Grounded Grid etc. technically speaking is a current conveyor, not a voltage gain stage (Read it amplifies neither voltage nor current). It can be roped into service as voltage gain stage by applying a current to voltage converter...

Anyway, we are here into semantics.

There are many ways to create gain, including transformers (a transformer loaded cathode follower can produce high voltage gain for example).

Ciao T

pieter t 23rd April 2011 06:31 PM

Quote:

Originally Posted by ThorstenL (Post 2548466)
Hi,

Anyway, we are here into semantics.

Ciao T

Yes, and OT in the meantime.
But IMO it is not good to do incorrect statements on a forum like this where so many gather their knowledge.


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