First 300b Design, Please comment - Page 4

astouffer · 6th February 2010, 06:14 PM

Quote:

Originally Posted by regal

FYI: I've been told by many that the LM317 series regulators aren't quiet enough for DHT supplies, you may be dissapointed.

The LM317 will be fine, especially with the bypass cap across the resistor from adj to ground. There's plenty of people who run DHT tubes from AC supplies without issue. Tubes that are sensitive to filament hum tend to be very high mu transmitting tubes like the 811A. I run 845s on 10vac filaments with a hum balance pot and its only noticeable with your head against the speaker.

tomchr · 30th December 2010, 02:41 AM

SGregory: How goes the project? Did you actually order those Electra-Print transformers? What do you think of them? Which load impedance and bias point did you end up with for the 300B?

I'm considering upgrading to the Electra-Print transformers for my design, hence my question.

~Tom

SGregory · 03:27 AM

Tom,
The project is on hold for the moment. I need to see if I can make a 6c45pi stable outside of its cardboard box first. Have been working on my analog source recently and am about to start a new thread on a Gyrator loaded 12b4a if it sounds as good as it measures. (Not always the case as you know. Am getting 0.01% THD with a -130dB noise floor.)

I have ordered several Electra-Print PT's, Chokes, and OPT's and have never been dissappointed. They are not fancy but are solid and have excellent sound. If you are refereing to the interstage xfmr I am comfortable with Jack's skills and would trust them as well. They are not too expensive unless you go exotic.

tomchr · 30th December 2010, 04:37 AM

I'm currently using Edcor transformers (CXSE25-8-5K) but am not terribly thrilled with them. For low powers, they're good bang for the buck. But the 300B should be capable of delivering over 10 W with 3k load when run close to the max plate dissipation. Some playing with the plate curves and paging around in RDH4 suggests that 10.8 W @ 3.5 % THD should be possible. Of course, that's with an ideal output transformer.

~Tom

tomchr · 30th December 2010, 04:46 AM

0.01 % THD, -130 dBV is nice by the way. Very nice!!

My 6J5 driver runs 0.05 % THD.

~Tom

30th December 2010, 03:24 AM	#33
SGregory Tubie Noobie diyAudio Member Join Date: Apr 2003 Location: Southern Tier NY	Tom, The project is on hold for the moment. I need to see if I can make a 6c45pi stable outside of its cardboard box first. Have been working on my analog source recently and am about to start a new thread on a Gyrator loaded 12b4a if it sounds as good as it measures. (Not always the case as you know. Am getting 0.01% THD with a -130dB noise floor.) I have ordered several Electra-Print PT's, Chokes, and OPT's and have never been dissappointed. They are not fancy but are solid and have excellent sound. If you are refereing to the interstage xfmr I am comfortable with Jack's skills and would trust them as well. They are not too expensive unless you go exotic. __________________ Living Life Doing the Waltz in 4/4 meter. Last edited by SGregory; 30th December 2010 at 03:27 AM.

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30th December 2010, 02:41 AM	#32
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	SGregory: How goes the project? Did you actually order those Electra-Print transformers? What do you think of them? Which load impedance and bias point did you end up with for the 300B? I'm considering upgrading to the Electra-Print transformers for my design, hence my question. ~Tom

30th December 2010, 04:37 AM	#34
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	I'm currently using Edcor transformers (CXSE25-8-5K) but am not terribly thrilled with them. For low powers, they're good bang for the buck. But the 300B should be capable of delivering over 10 W with 3k load when run close to the max plate dissipation. Some playing with the plate curves and paging around in RDH4 suggests that 10.8 W @ 3.5 % THD should be possible. Of course, that's with an ideal output transformer. ~Tom

30th December 2010, 04:46 AM	#35
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	0.01 % THD, -130 dBV is nice by the way. Very nice!! My 6J5 driver runs 0.05 % THD. ~Tom

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