How does a 12AU7 perform on low voltage? Also, how does the NP100v12 compare to readily available commercial amp using tubes like 6N3 (SMSL SP100) and 6N1/ECC88 (XDuoo MT-601) or 6J1/5654 (XDuoo MT-602)?
Depends on what you call low volts ?
I did a 12ax7 simulation that ran fine off 12 volts.
Didnt work on a real pcb though.
I found some 12ax7's needed a 470k from grid to 12 volts to work.
I used a mosfet on the output to buffer the valve output.
I have a hybrid amp that works off +/-25 volts OK (B+=50V)
I did a 12ax7 simulation that ran fine off 12 volts.
Didnt work on a real pcb though.
I found some 12ax7's needed a 470k from grid to 12 volts to work.
I used a mosfet on the output to buffer the valve output.
I have a hybrid amp that works off +/-25 volts OK (B+=50V)
Incred,
I don't know the theory but the 12AU7 is just one of those tubes that will run in 50 volt circuits and 300 volt circuits.
Not trying to be nasty, but at some point you just need to build and hear how it sounds to your ears.
Just a tip, no matter what you might read elsewhere (principally eBay sellers), the Russian 6N1p is NOT equivalent to the 6DJ8 family of tubes. Much higher filament current for a start and the other characteristics are way different too. Not a bad tube but nowhere near a 6DJ8/ECC88.
I don't know the theory but the 12AU7 is just one of those tubes that will run in 50 volt circuits and 300 volt circuits.
Not trying to be nasty, but at some point you just need to build and hear how it sounds to your ears.
Just a tip, no matter what you might read elsewhere (principally eBay sellers), the Russian 6N1p is NOT equivalent to the 6DJ8 family of tubes. Much higher filament current for a start and the other characteristics are way different too. Not a bad tube but nowhere near a 6DJ8/ECC88.
I have read somewhere that 12AU7 running at 12v will have higher distortion than 6N3 tubes. Is this true?
I have built the NP100v12 and are looking to upgrade it with nicer parts and a good tube. But I am hesitant on whether or not it will be worth it to upgrade it. Hence, my question to the comparison between the tubes. If the 6DJ8 or 6N3 will sound nicer than a 12AU7 on low voltage (in this case the NP100v12 uses 12v), then I think it would be better for me to save the money that I am planning to use on the upgrade and just buy a 6DJ8 or 6N3 amp.
I have built the NP100v12 and are looking to upgrade it with nicer parts and a good tube. But I am hesitant on whether or not it will be worth it to upgrade it. Hence, my question to the comparison between the tubes. If the 6DJ8 or 6N3 will sound nicer than a 12AU7 on low voltage (in this case the NP100v12 uses 12v), then I think it would be better for me to save the money that I am planning to use on the upgrade and just buy a 6DJ8 or 6N3 amp.
There are so many variables in any amp that a blanket statement that tube X will sound nicer (whatever your definition of that may be) than tube Y doesn't really apply.
I did a lot of 12AU7 rolling 10 or more years ago when I built my first SOHA. Even a Telefunken smooth plate sounded vastly different than a Telefunken ribbed plate.
If you want an amp you can tune by tube rolling, build one for which there are many specimens available from a variety of manufacturers whether they be 6DJ8s, 12AU7s or whatever.
I did a lot of 12AU7 rolling 10 or more years ago when I built my first SOHA. Even a Telefunken smooth plate sounded vastly different than a Telefunken ribbed plate.
If you want an amp you can tune by tube rolling, build one for which there are many specimens available from a variety of manufacturers whether they be 6DJ8s, 12AU7s or whatever.
I haven't built this amp so I can't comment. The power supply, the tube and the output cap will likely have the largest effect on the sound. Beyond that I can't speculate. BTW, as a matter of personal preference I'm not that keen on the 12AU7 when used as a gain tube. But that's just a personal bias you can take with a grain of salt.
S.
S.
Does the output capacitor benefit from bypassing it with a film capacitor (e.g Vishay MKP1837)? I read contradicting answers in diyaudio about electrolytics bypassed by a film capacitor. What do you think?
Also, can you explain to me why the tube doesn't use a grid stopper resistor? I saw many tube design that uses a grid stopper and grid leak resistor.
Also, can you explain to me why the tube doesn't use a grid stopper resistor? I saw many tube design that uses a grid stopper and grid leak resistor.
Cap bypassing falls under the, "season to taste" category. Try it, use it if you like it.
Grid stopper, probably not a bad idea to add one.
S.
Grid stopper, probably not a bad idea to add one.
S.
How do you calculate the grid stopper value? Also, how to calculate the C1 and C3 values? I have so many questions but are hesitant to write in the original forum because it's pretty much a dead thread.
I don't think the value of the grid stopper is all that critical. I've seen it anywhere from 180 ohms to 2k ohms.
To put the cat among the pigeons, don't you already have a low or low-ish voltage hp amp? Why build another? In my experience tubes that can run at high (100 +) voltages often lack "guts" and drive when driven at super-low voltages.
The Valve Wizard
To put the cat among the pigeons, don't you already have a low or low-ish voltage hp amp? Why build another? In my experience tubes that can run at high (100 +) voltages often lack "guts" and drive when driven at super-low voltages.
The Valve Wizard
Also, some people say to use a carbon resistor in the grid leak position. What are your take about this?
I am going for my decision to just upgrade my already built NP-100v12 amp. Since I will be primarily use the amp for planars, I don't think going full tube will be the best choice.
Before I start upgrading it, can this amp drive a planar headphone that are 25ohms 91db/1mw sensitive? Do I need to make some changes to the part values used?