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zxx222 21st August 2012 08:09 AM

Tubelab SE
I have finished SSE more than year ago and am very happy with result despite the fact that it was supposed to be 'pilot' project to see if I noob in electronics like me is able to do anythining like that. It sounds superb through my alpair 10.2 pensils. Success gave me confidence to try another diy projects, as it was joy to make and I would like to thank George for that - it is always pleasant to learn something new.

I have tse board with all necessary parts to populate it, and finally decided to start this project. I plan to use 300b's with hammond 373cz power transformer (325-0-325), target - 380-390V B+. In fact pt output will be 310-0-310 V or 340-0-340 V, depending on how I will connect primaries (240 or 220V with actual voltage input of 230V). I am confident that with 310V on secondaries I will be on safe side, but 340V is already risky as B+ might shoot over 400V - at least during voltages check out without tubes installed in amp.

Reading all threads related with tse check-out, I saw that B- with 300b's usually exceeds -350V. Is it safe to use C7 (100uF 350V) or should I buy cap, able to cope with higher voltages? What about C4-C6? Is 450 V enough or capacitors with higher voltage rating would be better choice in case if I stick with 340V on pt secondaries?

magnetman 22nd September 2012 11:44 AM

I have used a 450v electrolytic cap here, how ever i used a motor run cap 370v AC in parallel and it is happy. I plan to change both C7 and C6 to poly caps though, they sound better im told. we will see about that.


jrenkin 22nd September 2012 12:02 PM

If the voltage rating is 350v DC, use a higher rated cap. If it is 350v AC rated, like most motor run caps, you will be fine.

ranhaber 8th February 2013 06:26 PM


I'm building TSE with :
Psvane 300b with 400V 70mA
Svotek 5AR4
NEC 8542 with 27mA
Edcor OPT CXSE25-8-5K

Does my PT below is a good match fot my desire?

Edcor XPWR002-240 PT 240V, 50/60Hz. line to 720V (360-0-360) at 220mA center tapped, 60V at 800mA, 6.3V at 7A and 5V at 4A.

Does my TSE design and main parts is good?


boywonder 8th February 2013 10:48 PM

Have you read this page?

Your power transformer may be a little much......I think you'll be on the high side of the target voltages for the 300B......

You also won't need the bias tap, and have more 5 & 6.3V current capability than required. This may result in higher than target voltages for the regulator since you will be drawing less current, requiring additional heat sinking to get rid of the heat.

Have you considered the XPWR131-240? That one was custom spec'd by Rknize here for the TubelabSE and works quite well. You should be able get 400V B+ is desired with a proper choice of PS cap values.

The XPWR131-240 also allows the use 45 tubes if you decide that you want to try them in the future....

ranhaber 9th February 2013 12:52 AM

Thanks boywonder,

But i have some basic questions:
1. 300b heaters require 1.2A each, 5AR4 require 2A So the 5V need to have 4.4A min'.
2. 5842 needs 0.3A each for 6.3V
How does it match with the requirment for 6.3V 4A and 5V 2A?

Second question is the PT you suggested has 6.3V and 5V center tapped, how does it handle with it?
(George said no CT for the seconderys)

Thanks for the quick response :-)

rknize 9th February 2013 01:43 AM

TSE powers the 300B filaments with a regulated DC supply off of the 6.3V winding. The 5V is only used for the 5AR4. It's OK if the transformer is CT. You just tie-off and cover the unused tap.

rknize 9th February 2013 01:47 AM

Here are the voltages that you get from the XPWR131. Top readings are "45 mode" and bottom is "300B mode". The yellow meter shows the resulting B+ voltage and the middle meter shows the HT taps that are currently powering it. The meter on the left is attached to the unused HT taps in that scenario.

ranhaber 9th February 2013 08:53 AM

Rknize, every respone i got from you and all the rest make me smile :-)
I can't wait for a replay, like a child :-) lol

1. I fill stupid to ask but what do you mean "You just tie-off..." tie-off what? To where? Which end?
2. Did you use the CXC125-10H-200mA DC choke? If no and i want do use it, how it'll effecet?
3. Can you please send me the parts list you used for your 300b TSE?

Many thanks to you all ! :-D

ranhaber 9th February 2013 12:30 PM


About the 300b filaments-
"The 300B tube requires 5 volts and 1.2 amps for its filament. Some new production "300B tubes" require more filament current." a quote from Even all the datasheets say that,

so why did you said
"TSE powers the 300B filaments with a regulated DC supply off of the 6.3V winding."


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