• 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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#141
Comments are that half of them turned more noisy and microphonic after 100 hours of use, but the good ones remain some of the best 6V6s I have ever heard. Especially for their smooth human tone. Not the most ''monitor'' but very beguiling.
 
#143
Updates are that I took out anything CCS from the anode, and the circuit remains with resistors as loads. Constant current or constant voltage proved a non needed additive in this one, in my system, to my ears.
 
#144
Was asked by Tubo to post the buffer unity gain cathode follower way for those who don't want voltage gain. This one is non phase inverting as you know. The previous one with gain is inverting.
 

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#145
hey guys,

im almost ready to build the 6v6 pre.... i was just wondering will the anode loaded 6v6 be ok to be used as a dac output stage? what mods will be needed to achieve it?

i wanted to breadboard the circuit today and i don't have a 5k anode load for the 6v6 will a 5k output tranny work in place of the anode resistor?


this is the tube output stage that i want to replace with the 6v6.


thanks

ivan
 

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#146
I really don't know the outcome, haven't ever used it as I/V. Should work in principle but its for you to experiment. I know they use a small series resistor, but beyond that...

Regarding the anode load, I parallel 2 10 kOhm 5W. A transformer should work too. Just because it drops the output Z to whatever its ratio, up to 10k trafo can be beneficial for THD. When with a resistor load, more than 5k increases the output impedance enough.
 
#147
hi salas,

the 6v6 anode follower as a dac output stage is a success. i deviated some fromn the schematic.
i took out the 1k resistor and put in a 100k resistor from grid to ground and connected the dac positive and negative outputs from their corresponding capacitors directly to the grid and cathode. it still has no maeda regulator and converted the tube power supply to solid state.

what anode choke be suitable to replace the 5k anode resistor.i know that the 6v6 draws a high current.how do i connect a 5k se opt as an anode load. do i just connect the B+ side and the plate side and leave the secondary alone?

you've created a gem...thanks for sharing your knowledge.


thanks

ivan🙂
 
#148
Now you use it with a resistor on anode? What exactly you converted for psu? Is it a regulator?

If you leave the secondary alone there will be no reflected impedance to the primary. You either utilize the secondary for output, or terminate with nominal resistor with lower side grounded and then you got the primary as a choke load, taking output from the anode junction still using a blocking capacitor. In either case you should use as much B+ as the anode voltage you get after the drop for a resistor load.
 
#151
the same as the power supply you posted but with a ss rectifier. everything is cramped in a small chassis. once i finalized the project ill try a tube rectifier and see which one i really like.

ill try the maeda reagulator as soon as i get parts in. do you know if there is a pcb available for the regulator?


is the 100k grid to ground resistor i put in optimal for the circuit?what value does it really need?

thanks

ivan
 
#152
For a 6V6 no more than 220k I would use for avoiding grid current problems. In the 50k-220k region maybe your DAC can find a subjectively good spot? When ready, and anode load, current, B+, are final to you, ask me about a simpler simplistic shunt fixed for it. Much more spacious and natural in the HF than the Maida, more background info even, and far better than passive.
 
#154
Just be lucky so your OPT load experiment will provide enough inductance as a choke so to really do better than the resistor, and for any reg help, I will provide. How do you like it acoustically by now with the resistor by the way? You use K-75 output cap or something NOS USSR like that?
 
#155
i haven't tried the opt as an anode choke yet. i can't touch it as im really enjoying my music right now. im using the kiwame 5k as anode loads and they're my favorite on that position. the output caps im using are russian 2.2uf k73 petp , and russian k75-10y. i really do like the the k75-10 for their more human tone and emotionality. the petps are a bit hi fi sounding which they accentuate the high frequency a bit but they also sound very good, very clean with gobs of detail and tight tuneful bass. i have a .1uf russian teflon but haven't used them as couplers yet.
 
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