• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6V6 line preamp

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B

barretter

Member
Joined 2003
The gain of a real "anode follower" can be adjusted from maximum gain to unity gain by the ratio of two resistors in the circuit. Please don't use the term "anode follower" to designate a normal grounded cathode amplifier stage : it muddles things up and reduces the number of useable designations just as Bruce Rozenblit has with his misuse of "grounded grid".
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Not inherently drastically so, you can't. Tweaking current will be still about there for gain, only funnier working points. If you want an input Lpad, I don't advise it on transparency grounds, ups source impedance and interaction with Mr. Miller. Go buffer and listen first.
 
T

tubo

Member
Joined 2007
hi salas,

i tried 10k anode resistor and it sounded much better.all of the frequency spectrum opened up especially the bass. the harshness was gone and most of all i now have a usable range on my volume pot. what happened when i made the change?i know that increasing the load lowers THD. do i need to change the cathode resistor value if so what?


happy new year to all,

ivan
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Anything that can give 100mA at 400V without stress will do. So about 340V will be feasible counting the Vdif needs of regs. 45mA is for two channels, but 100mA is good for headroom or in case of shunt reg extra constant current needs.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
tubo said:
hi salas,

i tried 10k anode resistor and it sounded much better.all of the frequency spectrum opened up especially the bass. the harshness was gone and most of all i now have a usable range on my volume pot. what happened when i made the change?i know that increasing the load lowers THD. do i need to change the cathode resistor value if so what?


happy new year to all,

ivan
Click to expand...

In my case 5k was best, had tried 10k too. If your amplifier does not mind higher source impedance, then the THD with 10k is surely less, and you must have lessened the current also. OTOH the gain is supposed to go up? Then you use it as I/V so I don't know. What kind of voltage you got across Rk, and on plate, with how much B+? So to see on the chart. The main idea is to use the 6V6 as a triode line amp, find your best load and operating point in your system, by all means. Which make of 6V6 you got? The buffer arrangement has the less THD of all due to local feedback BTW. Cheers, happy new year.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
No, the filament goes up slowly since its a current source heater, the tube rectifier goes faster but rather slow enough too, compared to ss diodes. Haven't experienced any early wear due to cathode stripping yet. Of course the slower the rectifier tube, the best in that regard.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
I used a 100uF Pana HFZ once locally on the heaters, but I took it out because it was underneath the 5W burning when I went from noval to 6V6. Maybe a 0.1uF MKP for decoupling the cable inductance. But I have no noises in practice.
 
Joshua_G

Joshua_G

Member
Joined 2008
gomeh.com/
Salas, you feed your 6V6 line stage from Maida-like series regulator. Yet, in your "Simplistic Mosfet HV Shunt Regs" thread you say that the Shunt regulator sounds much better than the Maida one, which makes a lot of sense. Usually, when all else is equal, shunt regulators are much better and quieter than series ones. So, wouldn't this 6V6 line stage benefit from Shunt regulator?

I'd rather start the project with one type of regulator and I trust your experience.
 
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