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Old 1st March 2010, 06:48 PM   #1
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Default Mini tube output stage

I have picked up a Behringer SRC2496 after reading some positive stories online. It sounds horrible stock, but I am planning to build an SRPP output stage using subminiature tubes (6N16). Datasheet here: audio.ring.lt/pdf/6n16b.pdf

Since this is my first tube project, I would like to run the setup by some more experienced people.

SRPP
B+ at 100V
Rk = 333 Ohm
Ra = 16k6 Ohm
R to ground = 300 Ohm

I still have some trouble designing the PSU, esp. wrt to the load resistance of the tube circuit.

Thanks for the help!
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Old 2nd March 2010, 08:33 PM   #2
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Nobody? Maybe I should place in the tube section...
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Old 6th March 2010, 09:55 PM   #3
Tolu is offline Tolu  Germany
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take a look at Lukasz Fikus Lampizator
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Old 6th March 2010, 10:36 PM   #4
kevinkr is offline kevinkr  United States
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Should be in the tube section. SRPP output is non-ideal in a lot of applications, more of a fashion statement really. I have used it extensively and like it, but arguably not suited to general application - you need to design it to drive a well defined load impedance for optimum performance.

Also your proposed plate voltage is probably too low in an SRPP.

Incidentally not all tubes are universally applicable to SRPP application, I've found quite a few that frankly do not work, and also do not assume that you are going to realize a particularly low source impedance depending on the choice of tube. High perveance, high transconductance types seem to work pretty well..

Unless you need gain a CCS loaded cathode follower might be a better choice.

Make sure you can get the 6N16P before you plan extensively.. Some exotic Soviet subminiature types are not always easy to procure.
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Old 7th March 2010, 04:20 AM   #5
Pano is offline Pano  United States
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Moved to "Tubes."
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Old 7th March 2010, 07:48 AM   #6
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Quote:
take a look at Lukasz Fikus Lampizator
Read it, re-read it, and read-it again. Extremely helpful site for a beginner like myself

Quote:
Also your proposed plate voltage is probably too low in an SRPP.
I have a 125VAC transformer lying around, so my PSU (CLC) would give a B+ of 176VDC.
This leaves each tube 88V. If I understand the datasheet of the 6n16 well (audio.ring.lt/pdf/6n16b.pdf), this leaves and operating point of 88V/3.6mA, which is on the -2V line.

I am still a bit puzzled on how to calculate the resistor values in SRPP.
Rk = -2V / 0.0036 = 555 Ohm ?

The R between the top and bottom tube should be the same as Rk?


Quote:
Unless you need gain a CCS loaded cathode follower might be a better choice.
Noted. Let's take this as a first attempt at doing a tube project. The best description on the web seems to be the Lampizator site, so I'd prefer to take this as a starting point and further develop my skills from there.


Thanks

Last edited by studiostevus; 7th March 2010 at 07:51 AM.
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Old 7th March 2010, 08:21 AM   #7
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Quote:
take a look at Lukasz Fikus Lampizator

Read it, re-read it, and read-it again. Extremely helpful site for a beginner like myself
This site contains some sweeping statements that are overly simplistic and, in many cases, wrong or inadequately explained IMHO
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Old 7th March 2010, 02:39 PM   #8
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Allright, so Mr. Lampizator is a bit of a controversial character.

But that still leaves me with my resistor uncertainty ...
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Old 8th March 2010, 12:10 AM   #9
kevinkr is offline kevinkr  United States
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Originally Posted by studiostevus View Post
Allright, so Mr. Lampizator is a bit of a controversial character.

But that still leaves me with my resistor uncertainty ...
Your previous post on the resistor issue was on the right track, I would try 560 ohm resistors in both locations and see how close you get to your target current.. Your supply voltage should be adequate as long as it doesn't fall too far below 80V per triode. Some tweaking of the resistor value up or down is potentially necessary, but if you come within 10% or so of your target current that should be fine.
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Old 9th March 2010, 11:06 AM   #10
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Great, thanks.
I will try this then!
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