6EM7 SET Amplifier

[DAK808]

And I take it you must mean 5.5 cubic foot sub rather than cubic inch?

Yes, my mistake.

I have not held a camera in years but it did happen. It really is not much to look at on a baking pan and no way will I show my bird nest wiring underneath. I admire builders that take the time and effort to make a neat wiring job and show case chassis but I am more after the sound and do not really think I will use it as my main amplifier but that may change. About as cheap as you can build a SET if you can get by with 2 watts.[/QUOTE]

You should not disregard the need for neat wiring. Neat wiring can be helpful in minimizing induced noise into your signal circuit yielding better sound quality. Also AC carrying wires, like the heater circuit should be carefully laid out with any other wiring running at right angles if they need to cross.

 

[MrCurwen]

DAK808:

Good advice on the taking care and twisting AC wires and right angles and all that, completely agreed.

However, I'd just like to add that 'neat' as in "aesthetically pleasing to the eye" is not the same thing as 'neat' in electronic terms.

Shortest route (taking into account the right angles etc) is much better than aesthetically pleasing long routing. The end result might be rather ugly to the eye, but completely ok electrically.

 

[wdecho]

I did twist all AC wires and was careful to cross any wires at 90 degrees. I took the advice of a guy on youtube, Uncle Doug, and suspended my twisted filament wires in the air and dropping down as close as 90 degrees to attache to sockets instead of neatly mounting them to the chassis flat. Uncle Doug appears to work on a lot of tube amps and I am sure that hum is a constant complaint he hears and has to fix. Cannot really say if it made a difference but my amp is dead quite with your ear to my 103 db speakers. Probably just blind first tube build beginners luck. I try to take care to make my build wiring electronically sound but not exactly aesthetically pleasing to the eye. I was really concerned with hum on a tube build as so many have problems.

I received some NOS Sylvania yesterday and installed them. Not a lot of difference than the supposedly lightly used first ones I used but it does seem the treble is better. I am just amazed how musical this amp is. Being raised up on SS and thinking tube amps were old school I was not really expecting to seeing much difference in this amp vs SS. I have a tendency as others to favoring the latest build but after A/B some yesterday it still has a intoxicating effect. I feel like this is a very nice low cost way for any SS guy to try the SET tube sound. I would of course recommend efficient speakers at least in the above 90 db level it being only 2 watts. Tube guys using PP amps may want to try this amp as well to test the SET sound without feedback. I have went from 200 watts per channel amps in the 80's to now 2 watts. Manufacturers are always touting numbers as a selling point with more watts and lower distortion numbers supposedly better. Tube lovers know different. I am very impressed.

 

[crazyfrog]

6SL7 for input

Hi. Can a 1/2 6SL7 be used instead of the 6EM7 (or 6GF7) high mu section in that design? Thanks.

 

[thehoj]

Hi. Can a 1/2 6SL7 be used instead of the 6EM7 (or 6GF7) high mu section in that design? Thanks.

If you're going to do that, why even bother with the 6EM7?... The high mu and low mu sections in one envelope is part of the beauty of this amp.

Also the high mu section of the 6EM7 is already very very similar to a triode from a 6SL7.

 

[crazyfrog]

If you're going to do that, why even bother with the 6EM7?... The high mu and low mu sections in one envelope is part of the beauty of this amp.

Also the high mu section of the 6EM7 is already very very similar to a triode from a 6SL7.

Yes it looks curious to ask. But important tube to tube variations in the gain of the first section has been observed. Also, the 6SL7 option gives more flexibility.