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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 29th April 2010, 07:27 PM   #11
rknize is offline rknize  United States
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Originally Posted by tomchr View Post
Do you need a different OPT, though? The effective Rp of two tubes in parallel would be half that of one tube so it would make intuitive sense that the OPT primary impedance needs to be lowered by half as well.
George said:

Originally Posted by tubelab.com View Post
You can tie the plates of both output tubes together through a common OPT, or you can use two OPT's with their secondaries paralleled
If you go with the first option, you need an OPT with a primary impedance of about half of the single-tube case and about twice the power handling capability. It also needs to be able to handle twice the bias current. So a 5k, 10W OPT becomes a 2.5k, 20W OPT.

If you go with the second option, you just use two "normal" OPTs, one for each tube.
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Old 30th April 2010, 04:35 AM   #12
ystkkmkr is offline ystkkmkr  Japan
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Those SE output transformers are very expensive. Choke-loaded parafeed may reduce some cost, which is my plan.

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Old 14th January 2012, 07:27 AM   #13
ystkkmkr is offline ystkkmkr  Japan
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Default update

This PSE project has already been completed.

major modifications

- "pseudo choke input" power supply
- only one 5842 connected to two caps, as suggested by Tubelab
- RC added between B+ and 2SK2700s
- two anode load chokes (60H) per channel
- pp (parafeed) transformer with two separate primary windings (signals merged only on secondary)

I am very happy with the mono PSE amps driving my hybrid ESL speakers. Thank you all for the comments.

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