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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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It is currently 21 Feb 2020, 23:49

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PostPosted: 29 Aug 2019, 05:01 
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Joined: 23 Feb 2017, 02:02
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You can always use any op amp other than INA828 as a diffrential op amp, just that standard ones don't have DC level shifting option


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PostPosted: 18 Feb 2020, 17:09 
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poty wrote:
There is also a simple mod that almost eliminating the need of the 25Ohm pot (use its own CCS for each tube and connect the power tube cathodes together by a small resistor of 10-15Ohm value). The mod also helps with heat problems and allows the usage of lower current devices.



Regarding the use of separate CCS for each tube, will the attached schematics work that way? Is there something to modify?


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PostPosted: 18 Feb 2020, 20:45 
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Joined: 23 Feb 2017, 02:02
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It will not work


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PostPosted: 19 Feb 2020, 01:33 
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Joined: 24 Oct 2010, 07:05
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Yes, all is OK on the schematic. In practice the 10R resistor may be bigger in value, but it works even that way.

ILoveHiFi wrote:
It will not work
Why do you think so?


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PostPosted: 19 Feb 2020, 12:33 
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Joined: 06 Apr 2009, 10:08
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poty wrote:
ILoveHiFi wrote:
It will not work

Why do you think so?
Because by separating the current sources, you are forcing the same amount of current through both halves of the transformer primary even at AC conditions. It is the imbalance in drive between tubes, while maintaining the same TOTAL DC current that allows this topology to function. Once you split the current sinks between the two halves of the primary, there is no AC coupling and the amplifier will not function.

You need to solve for both DC and AC conditions when attempting to modify the topology.

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Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


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PostPosted: 20 Feb 2020, 00:41 
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Joined: 24 Oct 2010, 07:05
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While analysing circuits you should take into account not only an idea jist, but implementation too. There is a common element (namely 10R resistor) which made your assumption wrong.


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