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 19th February 2009, 05:03 PM #1 diyAudio Member   Join Date: Aug 2004 Location: Italy chocke anode load, please explain me.. Hi guys, Suppose I have a 6N6P , B+ is 200 Volt, bypassed cathode resistor is 100 ohms, anode resistor is 5,6 K . In this situation , gain is 13,5X ( into 100K) and since Rp is about 1600 ohms, probably output impedance is to say, 1400 ohm. Current is about 20 mA for each section. ( this is my beloved driver stage....:-) ) What happen if I swap the anode resistor with a good 60H choke? Gain? approx Output impedance? approx Perdone my basic questions, but I am a newbie on tubes and I would be learn Very thanks! Cheers, Paolo
 19th February 2009, 05:17 PM #2 diyAudio Member     Join Date: Nov 2004 Location: Back to Italy The anode resistor is dropping 5.6*20=112V, if you replaced that R with a choke your tube would be exposed to a much higher anode voltage. You need to lower it before replacing the R! 60H at 20Hz have an impedance of 2*3.14etc...*20*60=7.5K so you will have a bit more gain. Output impedance won't change, sound should improve (that's my taste). Even better would be a proper CCS. Gianluca
diyAudio Member

Join Date: Aug 2004
Location: Italy
Quote:
 Originally posted by Gluca The anode resistor is dropping 5.6*20=112V, if you replaced that R with a choke your tube would be exposed to a much higher anode voltage. You need to lower it before replacing the R!
Yup, understood, thanks Gianluca! :-)

Quote:
 [i] 60H at 20Hz have an impedance of 2*3.14etc...*20*60=7.5K so you will have a bit more gain. [/B]
Ok, How can I calculate this little "more" ?
No possible go to near the mu of the tube ( 22 about)?

Quote:
 [i] Output impedance won't change, sound should improve (that's my taste). [/B]
oh, what a delusion! :-(

Quote:
 [i] Even better would be a proper CCS. Gianluca [/B]
But this CCS lower the output impedance , am I right?

thanks,
Paolo

 19th February 2009, 06:52 PM #4 diyAudio Member     Join Date: Nov 2004 Location: Back to Italy You can go up to gain=mu using a CCS (that looks like a very-very large resistor). The output impedance can be lowered using the CCS-tube combo as a mu-follower. I believe a schematic can help. My preamp Google "gary pimm" and "walt jung" for some very interesting documents on CCS'. Many many pages have been written here too. OH! I loved 6N6s. One of the best things I soldered was a mufollower made by 6N6+EF184 Ciao Gianluca
 19th February 2009, 07:00 PM #5 diyAudio Member   Join Date: Aug 2004 Location: Italy Thanks Gianluca, Indeed I am more incline to Chocke instead CCS Anyway, back to the "little more" gain question, are we speaking about 1 dB ? Better than nothing ! But this mean that the more the chocke is bigger, the more the gain I will obtain? i also love the 6N6-P : IMO it is awesome "tubey" , very different from to say, a ECC88, 5842, etc . I am really impressed by 6N6-P. I have to thanks this TUBES section for this thing! Cheers, Paolo
diyAudio Member

Join Date: Nov 2004
Location: Back to Italy
Quote:
 Originally posted by inertial Thanks Gianluca, Indeed I am more incline to Chocke instead CCS Anyway, back to the "little more" gain question, are we speaking about 1 dB ? Better than nothing ! But this mean that the more the chocke is bigger, the more the gain I will obtain? Cheers, Paolo

CCS' actually outperform chokes. Keep in mind chokes usually have higher stray capacitance that impairs hi-freq (is that a problem really? we are talking >50kHz), and CCS will give you lower distortion (does it matter? probably not). The bigger the choke the heavier the iron the higher the price the worse the hi-freq behavior. CCS' can offer also a better rejection of PSU's noise. And cost 1/10 of a good choke.

The choke's impedance goes up with frequency, I calculated the value at 20Hz to make sure 60H are enough otherwise low frequencies would be compromised. I believe you won't notice any difference of gain between CCS and chokes (but at low frequency).

OH! I do use chokes as necessary.

Ciao
g

 19th February 2009, 10:44 PM #7 diyAudio Member   Join Date: Dec 2004 Location: Cincinnati, Ohio The advantage of a choke is its energy storage, a CCS must drop whatever volts your planning to swing across it, along with some headroom drop across the CCS parts itself. CCS is a variant of resistive load. Choke vs CCS on the same B+ will involve different operating points, as mentioned. __________________ Be sure your foil hat has a good low impedance ground.
 20th February 2009, 11:47 AM #8 diyAudio Member   Join Date: Aug 2004 Location: Italy Thanks Gianluca and Tweeker Things are more clear for me now Cheers, Paolo

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