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Old 20th Feb 2007, 7:54 pm   #61
yagosaga
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Default 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
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Old 25th Feb 2007, 6:27 pm   #62
oldeurope
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Default 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 (micro). This 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 is possible.
The driver stage is biased to get full at low plate voltage. In the triodelington stage I disconnected the speaker to get full . 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 in the databooks is 17.
At low plate voltage the of valve A = 17,3 and of valve B = 16,7.
At high plate voltage of valve A = 17,9 ; of valve B =14,9.
The of valve A increases a little bit with the plate voltage. At valve B it decreases. The change of valve B goes in a different direction and is stronger. Isnt it interesting? I dont 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.
Attached Thumbnails
Click image for larger version

Name:	ECC82_A_B.JPG
Views:	94
Size:	50.5 KB
ID:	8435  
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Old 26th Feb 2007, 11:37 am   #63
oldeurope
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Smile 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
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Old 26th Feb 2007, 3:14 pm   #64
oldeurope
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Exclamation STC is not triode/triodelington.

Quote:
Originally Posted by oldeurope View Post
Hi I found something interesting about "triode feedback":
http://www.gem.hi-ho.ne.jp/katsu-san...1_english.html

Kind regards,
Darius

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=gmVgk, so Vgk=Ip/gm
So, if the load resitance(or impedance) is RL, the open loop voltage of tetrode;
Vout=RLIp
gain of tetrode Av is Vout/Vin. From above two equations;
Av=gmRL
And thus, the output impedance Ro is determined by 100% feedback,
Ro=RL/(gmRL) = 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 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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Old 13th Apr 2007, 7:18 am   #65
oldeurope
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Smile Re: triode sound ...

Quote:
Originally Posted by oldeurope View Post
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 (micro). This 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 is possible.
The driver stage is biased to get full at low plate voltage. In the triodelington stage I disconnected the speaker to get full . 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 in the databooks is 17.
At low plate voltage the of valve A = 17,3 and of valve B = 16,7.
At high plate voltage of valve A = 17,9 ; of valve B =14,9.
The of valve A increases a little bit with the plate voltage. At valve B it decreases. The change of valve B goes in a different direction and is stronger. Isnt it interesting? I dont 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.
Update attached.

Kind regards,
Darius
Attached Files
File Type: zip Triodelington_schematic_25.Feb.07.zip (32.4 KB, 186 views)
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