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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

One more 4P1L SE

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#1,221
MikyK said:
Right now I have 45 tube with regular bypass cap and resistor, maybe it will be better with fixed bias, but I dont know.... As a driver I use 6N23P SRPP (same driver as I used with 4P1L dc coupled amp) which is capacitor coupled to the 45. Maybe its the bypass cap or the driver distorting (it must generate twice output voltage now) which is wrong.
Ive got two KC1 telefunken tube (dht with amplification of 30), and I can try it as a driver to drive 4P1L....

And trust me, DC coupled sounded (with 4P1L) really good even with the bypass cathode cap.
but I want to test something really different: using a voltage regulator tube instead of the cathode resistor and cap!
Click to expand...

Would be happy if you could show your 4p1L DC couple schematic.
I have both the 4p1L with filament bias to compare with my DC coupled 45 with ultrapath. They both are good with merits in different materials I fed into them.
 
#1,222
albertli said:
Would be happy if you could show your 4p1L DC couple schematic.
I have both the 4p1L with filament bias to compare with my DC coupled 45 with ultrapath. They both are good with merits in different materials I fed into them.
Click to expand...


Here it is, the voltages are not 100% the same, each DC coupled amp you must tweak individually. I hope you can read the image.
An externally hosted image should be here but it was not working when we last tested it.
 
#1,223
MikyK said:
Here it is, the voltages are not 100% the same, each DC coupled amp you must tweak individually. I hope you can read the image.
imageresize
Click to expand...

Would you kind enough to show it in PDF file. I can't open this file.
Thanks
 
#1,226
albertli said:
Big thanks
Click to expand...
This is the best amp that I have built. Ive played with the current through the driver tubes.
Like 4mA in the schematic: the sound is open, fradgile and very detailed, but not much bass. Instrument separation is very good.
Then I replaced lower resistor with an LED and upper cathode resistor recalculated to have same parametres as the LED. I changed also the dropping resistor from cca 33K to 11K.
The tube has 14mA current or so.
With this configuration it has more drive and the bass is punchier and heavier. But it seems less clean overall. But still pretty good. You must play with the current and to the driver position use double triode which can work at low voltages of 80-100V (with normal bias point and current). ECC88 or 6N23P are pretty suitable for this, but if you will know any other tube which works with these voltages fine, let me know.
 
#1,227
MikyK said:
This is the best amp that I have built. Ive played with the current through the driver tubes.
Like 4mA in the schematic: the sound is open, fradgile and very detailed, but not much bass. Instrument separation is very good.
Then I replaced lower resistor with an LED and upper cathode resistor recalculated to have same parametres as the LED. I changed also the dropping resistor from cca 33K to 11K.
The tube has 14mA current or so.
With this configuration it has more drive and the bass is punchier and heavier. But it seems less clean overall. But still pretty good. You must play with the current and to the driver position use double triode which can work at low voltages of 80-100V (with normal bias point and current). ECC88 or 6N23P are pretty suitable for this, but if you will know any other tube which works with these voltages fine, let me know.
Click to expand...
Sounds good and I am going to check what parts and tubes I have I hand. You make me busy again.
 
#1,228
MikyK said:
This is the best amp that I have built. Ive played with the current through the driver tubes.
Like 4mA in the schematic: the sound is open, fradgile and very detailed, but not much bass. Instrument separation is very good.
Then I replaced lower resistor with an LED and upper cathode resistor recalculated to have same parametres as the LED. I changed also the dropping resistor from cca 33K to 11K.
The tube has 14mA current or so.
With this configuration it has more drive and the bass is punchier and heavier. But it seems less clean overall. But still pretty good. You must play with the current and to the driver position use double triode which can work at low voltages of 80-100V (with normal bias point and current). ECC88 or 6N23P are pretty suitable for this, but if you will know any other tube which works with these voltages fine, let me know.
Click to expand...
Sounds good and I am going to check what parts and tubes I have in hand. You make me busy again.
 
#1,229
Concept:
#26, D3a as gyrator, DC coupled 4P1L SE (5k:8).

The 4P1L PSU is floating, all voltage here (power tube) is reference to this PSU's "ground".

Good 1W in A1 region.

Push 4P1L to A2 theoretically reaches 2W (5%).
 

Attachments

  • #26, D3a as gyrator, DC coupled 4P1L SE 5k.jpg
    #26, D3a as gyrator, DC coupled 4P1L SE 5k.jpg
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#1,238

Attachments

  • 4P1L (triode).JPG
    4P1L (triode).JPG
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  • 4P1L-driver-bias-point.png
    4P1L-driver-bias-point.png
    59.1 KB · Views: 179
  • 4P1Lpinout.jpeg
    4P1Lpinout.jpeg
    91.5 KB · Views: 194
  • 4P1L-SE-Loadline.png
    4P1L-SE-Loadline.png
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