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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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20th Feb 2007, 8:54 pm | #61 |
Retired Dormant Member
Join Date: Mar 2005
Location: Braunschweig, Germany
Posts: 208
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Re: making an audio output triode...
Hi Darius,
try it with the PCC88. Filament voltage is appr. 4 V. You would be astonished when you test the PCC88. This was my love child under the triodes in these good old days. Kind regards, Eckhard |
25th Feb 2007, 7:27 pm | #62 |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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triode sound ...
Good evening,
to get a nice triode sound you must make sure that the voltage gain of the triode is very close to the maximum possible gain of the triode called µ (micro). This µ is set by the construction of the valve. It changes a little bit with the plate voltage. This is one importand aspect of the characteristical triode sound. To get the sound you like, try out some triodes. I can not show you the sound in the forum but measuring the change of µ is possible. The driver stage is biased to get full µ at low plate voltage. In the triodelington stage I disconnected the speaker to get full µ. Now it is possible to compare two different constructed ECC82. Valve A is modern construction. Its plate construction is similar to the ECC88. The other one valve B is a well known kind of the ECC82. See pic attached. The propagated µ in the databooks is 17. At low plate voltage the µ of valve A = 17,3 and µ of valve B = 16,7. At high plate voltage µ of valve A = 17,9 ; µ of valve B =14,9. The µ of valve A increases a little bit with the plate voltage. At valve B it decreases. The µ change of valve B goes in a different direction and is stronger. Isn’t it interesting? I don’t want to say which sound I like more. It is yours to try it out! The triodelington amp shown here is constructed to get as much triode sound as possible. Not every triode amp is designed in this aspect. Kind regards, Darius PS: I am not able to upload the updated schematic. |
26th Feb 2007, 12:37 pm | #63 |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: making an audio output triode...
Hi I found something interesting about "triode feedback":
http://www.gem.hi-ho.ne.jp/katsu-san...1_english.html Kind regards, Darius |
26th Feb 2007, 4:14 pm | #64 | |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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STC is not triode/triodelington.
Quote:
Please note this Quote from STC website: "I write that the output voltage will be changed, but of course the feedback is not superconductivity(!), so the output has some output impedance. The value of output impedance is determined by the characteristic of output tetrode. As I already explained, this is 100% voltage feedback, so it is defined by the trans-conductance (gm) of output tetrode, because it defines the open voltage gain. Ip of tetrode/pentode is determined by Vgk and proportional constant 'gm' (transconductance); Ip=gm·Vgk, so Vgk=Ip/gm So, if the load resitance(or impedance) is RL, the open loop voltage of tetrode; Vout=RL·Ip gain of tetrode Av is Vout/Vin. From above two equations; Av=gm·RL And thus, the output impedance Ro is determined by 100% feedback, Ro=RL/(gm·RL) = 1/gm this is just the same as cathode follower." Hm, you don't get the typical triode output graph shown at the beginning of the thread. At the input you need the voltage to current converter. I did not notice this at first look, this thing is very different from the triodelington. The voltage gain is not (much) reduced by the load and the feedback triode works with µ gain. In a real triode amp and the triodelington you must take a load resistance much higher than the load for maximum output. Kind regards, Darius |
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13th Apr 2007, 8:18 am | #65 | |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: triode sound ...
Quote:
Kind regards, Darius |
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