Hi SolderSober.
I had have mine for nearly 3 month now. I'm mostly using mine directly without any PRE Amp. I have a little less gain, but the sound quality is way better.
Mine is based upon Andy's design. I have quite expensive Caps Vcap CuFT and a TDK 2CP-2511 pot, with gyrator Audyn True Copper and my Sowter S9 , 5K.
PSU with Choke and Film Caps it 2 separate boxes.
When I play Rock,Metal,Hiphop with a level of extended bass, The bass is deep clear and completely transparent on my Tannoy HPD-385A 303 liter speakers. It sound different compared to my 'Old 2A3 loftin white' and It serious took me some time to get used to the natural way it sound.
Maybe the 4P1L PSE does sound a 'little polite' when you play Rock music, I don't think it's an issue when you get used to the quality of this amp. Every new CD/LP is a new story on this amp.
I'll suggest you to build the other 'mono' as it's quite difficult to judge the amp on only one channel.
I use 1N5406G diodes, so I suppose I can add more capacitance. I wanted to stay with film caps, hence the low values. This part is easy to play with, will give it some try. Any advice on where to add extra caps (electrolytic I suppose)? Thanks
Another question - what is the consensus on delayed B+ for these tubes, any sense building it in?
I see you have not used Ali's gyrator in your current version of the preamp.
Andy,
Can I have a link for that NP transformers. I would like to try.
Thanks
Albert
Rod,
Sounds like you like this configuration over tube rectified. Would you tell me more about it. I always found the SS rectification sound fast and thin. Might be your approach is a step forward.
Thanks
Albert
Phương Nguyễn <npacoustic@gmail.com> NP Acoustic - NP Hi-End Audio
I love his amorphous core stuff. 3.2K OPT and the smaller plate choke I have, 136H at 15mA. It's really smooth. I doubt if it's expensive - I didn't pay for mine, so can't give you a price.
Even though they have pretty strong control grid, I would not charge coupling caps through chokes & grid currents. Let them charge through grid leak resistors before tubes start conducting.
Ok, I need to admit this went over my head. At the same time I feel it's important
Can you please explain a bit more what you meant here?
I have a problem with the second channel build that may be related. Thanks
When the driver stage loaded on a choke, and coupled with a coupling cap, that choke and the coupling cap form a tuned oscillation tank that causes higher currents through the control grid when powered on than if the driver was loaded on a resistor.
It is a really bad idea to delay B+ in tube amps. It was used in big transmitting tubes with high cathode density, like magnetron oscillators in radars. When filaments were heating up they start oscillating, because it is enough of emission from a small portion of cathode, that gets hotter as the result damaging the tube. That's why B+ was delayed until all cathode emits uniformly. Manufacturers of amps always add some "selling features", no matter do they improve, or harm the amp. Delayed B+ is one of them.
It is a really bad idea to delay B+ in tube amps. It was used in big transmitting tubes with high cathode density, like magnetron oscillators in radars. When filaments were heating up they start oscillating, because it is enough of emission from a small portion of cathode, that gets hotter as the result damaging the tube. That's why B+ was delayed until all cathode emits uniformly. Manufacturers of amps always add some "selling features", no matter do they improve, or harm the amp. Delayed B+ is one of them.
Interesting.
I'm a ardent proponent of delayed +B until I modified my car tube amp and I noted a strong peak current in my 12V bench PSU when the 20 sec delayed +B supply started, far bigger than charging the secondary HV cap. In fact the output tubes are suffering from this. I shortened the delay and now have only 2-3 sec., only for distributing the starting peaks (first peak being the heaters). With tubes cold, the HV PSU current peak are far shorter and smaller. Now the output tubes are happy.
These bench measurements are good here.
Note that HV SMPS inverter supply have low output impedance output so it maintain the HV even with all output tubes with zero g1, so I also added some protection...
Of course, if one uses tube rectification, if using indirectly heated rectifier tubes, will apply gently the voltage to stages so overload are minimal. DH rectifiers will suffer when feeding IDH tubes.
In other amp of mine, a PL509 PP amp (in my main home system), I delayed only the output supply, so even the coupling caps are charged when output receives power.
