6CJ3 and other dampers are a good way to drop lower voltage.
Use PSUD2 to check that you can get 20V above your target output voltage, to allow for SSHV headroom.
Then again, if you have SSHV, the rectifiers should not have much effect on the sound. Try UF4007 (solid state) diodes, and a little damping resistor (example: 22Ω 7W) in series. You should have enough voltage in this case.
Use PSUD2 to check that you can get 20V above your target output voltage, to allow for SSHV headroom.
Then again, if you have SSHV, the rectifiers should not have much effect on the sound. Try UF4007 (solid state) diodes, and a little damping resistor (example: 22Ω 7W) in series. You should have enough voltage in this case.
Hi Ale,
Your Blog is very interesting, beautiful amps!
One question;
2P29L's max plate dissipation is 1W according to spec sheet. Regarding your article, it seems like your 2P29L is running around 2W, if I do not misunderstand. I'm not a tube guy, so I'm wondering if it's OK biasing the tube like this. Thank you in advance.
Your Blog is very interesting, beautiful amps!
One question;
2P29L's max plate dissipation is 1W according to spec sheet. Regarding your article, it seems like your 2P29L is running around 2W, if I do not misunderstand. I'm not a tube guy, so I'm wondering if it's OK biasing the tube like this. Thank you in advance.
The 2p29p has a plate dissipation of 1W, the 2P29L has a dissipation of 2W according to my data sheets.
2W dissipated by anode plus 07.W dissipated by G2.
And I believe when naked it can dissipate more because aluminium shield reflects heat back. Needs to be tortured to get the real data. ;-)
https://www.istok2.com/scan/222_1.gif
And I believe when naked it can dissipate more because aluminium shield reflects heat back. Needs to be tortured to get the real data. ;-)
https://www.istok2.com/scan/222_1.gif
One more question.
In this schematics, plate voltage is 132V, but why my LTSpice simulation tells me it should be 175V? 132V is for 2.2 ohm cathode resistor.
2P29L DHT Preamp – Bartola Valves
I'm using this model used as a DHT model.
https://i2.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2016/06/2P29L-triode-model.png
The voltage is fine with the following schematics.
https://i0.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2016/06/2P29L-Preamp.png
In this schematics, plate voltage is 132V, but why my LTSpice simulation tells me it should be 175V? 132V is for 2.2 ohm cathode resistor.
2P29L DHT Preamp – Bartola Valves
I'm using this model used as a DHT model.
https://i2.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2016/06/2P29L-triode-model.png
The voltage is fine with the following schematics.
https://i0.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2016/06/2P29L-Preamp.png
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If you use LTSpice model, make sure you get it working right first time. Specially with DHTs in filament bias. If you use a 4 element model (like Dmitry's) then depends on how you place the current source.
Either way the model reflect's in my SPICE simulation the curves I traced with one sample.
I used a different valve on the actual build. I could check again but sadly I reformed the preamp to a 4P1L
Build it yourself and measure it.
Either way the model reflect's in my SPICE simulation the curves I traced with one sample.
I used a different valve on the actual build. I could check again but sadly I reformed the preamp to a 4P1L
Build it yourself and measure it.
Yes it did work exactly the same as the voltage and current on your first schematics. 180V@15mA, 70ohm resistor.
I used a different valve on the actual build. I could check again but sadly I reformed the preamp to a 4P1L
Build it yourself and measure it.
OK, I will try. Thank you for the response.
PS: this tube is very different each other? I mean consistency.
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Just wondering if 2P29L is as consistent as 4P1L. It's military use, so it should be, I guess.
Just wondering if 2P29L is as consistent as 4P1L. It's military use, so it should be, I guess.
Not necessary. I was really surprised when found how consistent 4P1L are.
GU-50 are military tubes also designed by Telefunken, but consistency was Soviet...
Well, I guess it depends on the batch, the year and your expectations...I got really a lot 4p1l like 80pcs from 1959, 50 from the 60s/70s and 20 younger...
The 1959 are by far the strongest when measuring emission, rp, gm etc. the top guys achieve values (measured with calibrated utracer), which no other batch achieve, the middle of the crowd samples are like the top of the 60/70s. I selected about 30 top-performers and matched them.
But what I saw as well is that none of them was performing below 100%. So, they are all good and strong...which is not always the case with russian tubes...had just some drama with 6n6p...
The 1959 are by far the strongest when measuring emission, rp, gm etc. the top guys achieve values (measured with calibrated utracer), which no other batch achieve, the middle of the crowd samples are like the top of the 60/70s. I selected about 30 top-performers and matched them.
But what I saw as well is that none of them was performing below 100%. So, they are all good and strong...which is not always the case with russian tubes...had just some drama with 6n6p...
Hi Ale
I do your last version of 4P1L preamp. It is 99% finished.
After first turn up i had to low bias settings and to low B+ drop resistor value (220R) so on the input of a Gyrator was 280-285V, then i was try to turn up the trimer and measure ...and after a while one chanell was semidefect-defect ...at 4p1l anode i get 67V. After turning trimer VREF voltage goes from 140-170V but nothing happens on Anode voltage. Which part can be damaged. So on IXTP i had D..280V on S and G 67V and after remeasuring also second gyrator died...same failiure ...67V on anode. Now B+ is 300V on D of IXTP , because no current flow trought both regulators and no voltage drop on 470R (earlier 220R) that is on output of raw B+ regulator. Filament reg is ok. i got 7,8 til 8V on the top of 15R resistor depends on active or inactive Anode voltage.
Thank you Davorin
I do your last version of 4P1L preamp. It is 99% finished.
After first turn up i had to low bias settings and to low B+ drop resistor value (220R) so on the input of a Gyrator was 280-285V, then i was try to turn up the trimer and measure ...and after a while one chanell was semidefect-defect ...at 4p1l anode i get 67V. After turning trimer VREF voltage goes from 140-170V but nothing happens on Anode voltage. Which part can be damaged. So on IXTP i had D..280V on S and G 67V and after remeasuring also second gyrator died...same failiure ...67V on anode. Now B+ is 300V on D of IXTP , because no current flow trought both regulators and no voltage drop on 470R (earlier 220R) that is on output of raw B+ regulator. Filament reg is ok. i got 7,8 til 8V on the top of 15R resistor depends on active or inactive Anode voltage.
Thank you Davorin
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Hi Davorin,
It's hard to say whether you've damaged the gyrator or not. without pictures and detailed schematics of what you have actually built is hard to give advice.
First of all, did you follow the basic steps for testing the board before firing it up?
Here is an extract:
• I’d first test the CCS without any load connected to the anode. You can make sure that the voltage can be set by varying P1 and measuring the reference voltage at VREF. If you measure about HT despite turning P1, then there is something wrong with your CCS and likely you have damaged the pair of LND150.
• I’d strongly recommend using a VARIAC to test the PCB or a variable HT supply.
• Use a 10KΩ -22KΩ / 1 W dummy load resistor instead of the valve, don’t avoid this step. Slowly bring the HT up and check the voltage across the dummy resistor. You should be able to adjust P1 to set the right voltage.
• If you accidentally short the anode or the mu output, you will damage the M3 and will short the HT into the output. This can be easily detected when you adjust P1 and you still get HT level regardless of P1 position.
• Once voltage setting at the dummy resistor is achieved, you can replace the dummy resistor with your valve and test again. It should work like a charm!
Whether you have a short somewhere or a defective valve could be the reason. If you get one channel working fine and the other that it doesn't, then I would look at testing the 4P1L valves independently and replace if you find a defective one.
If the gyrator "dies" is likely to produce a short on the cascoded MOSFETs rather than open.
Were you able to vary the output voltage of the gyrator by adjusting the trimmer?
I'd test them with a dummy load first as suggested above. Then I'd check that the CCS (LND150 pair) is operating properly. If not, you need to replace them (unlikely). If you still get the 300V at the output of the gyrator, then you will need to replace the IXTP device and likely the lower FET.
Hope this helps
Ale
It's hard to say whether you've damaged the gyrator or not. without pictures and detailed schematics of what you have actually built is hard to give advice.
First of all, did you follow the basic steps for testing the board before firing it up?
Here is an extract:
• I’d first test the CCS without any load connected to the anode. You can make sure that the voltage can be set by varying P1 and measuring the reference voltage at VREF. If you measure about HT despite turning P1, then there is something wrong with your CCS and likely you have damaged the pair of LND150.
• I’d strongly recommend using a VARIAC to test the PCB or a variable HT supply.
• Use a 10KΩ -22KΩ / 1 W dummy load resistor instead of the valve, don’t avoid this step. Slowly bring the HT up and check the voltage across the dummy resistor. You should be able to adjust P1 to set the right voltage.
• If you accidentally short the anode or the mu output, you will damage the M3 and will short the HT into the output. This can be easily detected when you adjust P1 and you still get HT level regardless of P1 position.
• Once voltage setting at the dummy resistor is achieved, you can replace the dummy resistor with your valve and test again. It should work like a charm!
Whether you have a short somewhere or a defective valve could be the reason. If you get one channel working fine and the other that it doesn't, then I would look at testing the 4P1L valves independently and replace if you find a defective one.
If the gyrator "dies" is likely to produce a short on the cascoded MOSFETs rather than open.
Were you able to vary the output voltage of the gyrator by adjusting the trimmer?
I'd test them with a dummy load first as suggested above. Then I'd check that the CCS (LND150 pair) is operating properly. If not, you need to replace them (unlikely). If you still get the 300V at the output of the gyrator, then you will need to replace the IXTP device and likely the lower FET.
Hope this helps
Ale