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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Like so???? posted by fatbottle on July 2, 2002 at 06:37:15:
Hi all. Just thought I would stick some of my thoughts in here."a stack of lithium cells may be ideal here"
One thing to watch when using batteries for fixed bias- the operating point is sensitive to line voltage fluctuations. If you are using a transformer to generate the negative bias the amp will be less suseptable to line voltage changes. The bias will increase or decrease along with the line voltage changes.
"You may have problems with the dissipation of the CCS on top of the 6BX7 if the HT is high , also high voltage transistors may have to be used which usually have low Hfe (current gain)"
The PMCCS Bas is using on the second stage is only limited in voltage and power disapation by the choice of pentode used. Doesn't use high voltage transistors.
"Remember that a CCS loaded stage will only be super-linear with an open circuit load . The 813 is a big valve , therefore probably has big capacitance Cin and miller
This is true for "normal" CCS's. The PMCCS has the capability of using the bottom Mosfet as a mu folower. If Bas drives the interstage tranny from the mu output of the PMCCCS he won't have any problems with driving the output tube. With the Ra of the 6BX7 around 1.3K the output Z of the mu folower connection should be less than 100 ohms.
Gary
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Follow Ups
- Re: Like so???? - Gary P 10:44:17 07/02/02 (1)
- Re: Like so???? - fatbottle 15:06:24 07/02/02 (0)
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