costa23 said:
Hi, do you take the output from cathode, anode or grid?
http://www.diyaudio.com/forums/attachment.php?s=&postid=1579557&stamp=1218073742
check out this site
http://www.diyparadise.com/simplepreamp.html
I built this design and added gas regulators to it. Look around the site and you will find the schematic and the power supply. When built as he designed it has ZERO noise. The chokes are an important part in the design and cost very little. I would eliminate the fancy caps and led and build as shown. When you are comfortable with it then dive into a CCS and see if there are any differences to be had.
I believe if you do a search a thread should turn up here.
http://www.diyparadise.com/simplepreamp.html
I built this design and added gas regulators to it. Look around the site and you will find the schematic and the power supply. When built as he designed it has ZERO noise. The chokes are an important part in the design and cost very little. I would eliminate the fancy caps and led and build as shown. When you are comfortable with it then dive into a CCS and see if there are any differences to be had.
I believe if you do a search a thread should turn up here.
costa23 said:
Better in what way? And to whom?
I know what i'd do. Get rid of all the nice and cosy carbon comps and Kiwame resistors. They help produce a pleasant but also very coloured sound. Put some Caddocks in place.
Replace the anode resistor with a choke and experience a really serious improvement.
Replace the diodes with mercury rectifiers or tv dampers. Obviously the entire PS will need redoing then.
Chokes are a very good idea, they bring a nice rich tone.
5687 tends to oscillate so make certain the grid is stoppered and the anode load is straight onto the pin.
I built a version with a CCS load and it sounds a little to detailed for my taste, still the 5687 is an excellent valve.
AC on the filament is fine, though if the 5687 starts oscillating it will tend to pick up hum from the filament. If you experience hum problems don't blame the filament - look for the instability !!
Shoog
5687 tends to oscillate so make certain the grid is stoppered and the anode load is straight onto the pin.
I built a version with a CCS load and it sounds a little to detailed for my taste, still the 5687 is an excellent valve.
AC on the filament is fine, though if the 5687 starts oscillating it will tend to pick up hum from the filament. If you experience hum problems don't blame the filament - look for the instability !!
Shoog
#13
Hello analog_sa
E.g. Hysteresis distortions.
(An air coil has no hysteresis.)
??? See attachment
Yes of course, especially if you have high impedance stages.
Sure, a resistor has less capacitance than a coil and
it doesn't change it's impedance with the frequency.
(You can get resistors that go from DC to UHF and higher.)
One coil, the output transformer, is definitely enough.
Kind regards,
Darius
Hello analog_sa
E.g. Hysteresis distortions.
(An air coil has no hysteresis.)
??? See attachment
Yes of course, especially if you have high impedance stages.
Sure, a resistor has less capacitance than a coil and
it doesn't change it's impedance with the frequency.(You can get resistors that go from DC to UHF and higher.)
One coil, the output transformer, is definitely enough.
Kind regards,
Darius
Attachments
Lemme take a stab.
With a choke, you can actually swing more voltage than is available with a resistor. If I have a 150V B+ serving a 6SN7, the triode can actually swing from 0 to 300V. Approximately, of course; the triode doesn't actually reach 0V, but the principle is there.
With a resistor, the triode can never swing more than 150V, because that's all that's available from B+.
Is this what you mean?
With a choke, you can actually swing more voltage than is available with a resistor. If I have a 150V B+ serving a 6SN7, the triode can actually swing from 0 to 300V. Approximately, of course; the triode doesn't actually reach 0V, but the principle is there.
With a resistor, the triode can never swing more than 150V, because that's all that's available from B+.
Is this what you mean?
not true ...
This is not ok.
You have to compare the stages under same conditiones i.e. same anode voltage.
See example in post #14 :
http://www.diyaudio.com/forums/attachment.php?s=&postid=1580725&stamp=1218205773
zigzagflux said:
This is not ok. You have to compare the stages under same conditiones i.e. same anode voltage.
See example in post #14 :
http://www.diyaudio.com/forums/attachment.php?s=&postid=1580725&stamp=1218205773
oldeurope said:
My current line stage/buffer uses a Hammond 150H choke as a cathode follower load for a 6W6. Triode connected the midband distortion into >50k ohm is less than 0.003% at 1 vrms past 20 kHz, rising to ~0.05% at 20 Hz. Connected true pentode it drops below the ability of my M-Audio Firewire to measure reliably at 24 bit mid-band. It also passes a pretty nice 200 kHz square wave either connection, all easy flaws to live with in a $15 choke.
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