New build EL84 vs 6V6, single vs Push Pull

[GeorgeG]

I am planning a new build. I don't perform live anymore so I don't need volume but it's still all about the tone. I play rock and blues and like tube amp distortion. My current build is a single octal power tube and a JJ KT77 is currently my favorite tube. I like this amp a lot but it is pretty loud when I get the tone I want.  I am looking at lower power and/or a push pull design. Can you guys give me your thoughts on a 6V6 vs EL84 approach and single ended vs push pull. This site has a number of designs around these differences.

I am fascinated with the history of 60's/70's rock where lower power amplifiers (Clapton - Marshall combo, Gibbons - various) were used even if stage persona demanded Marshall stacks (Page - Supro ...) or at least lower power EL84 tubes were used (May).

Thanks,

George
 

[MakerDP]

You should be able to replace that KT77 with a 6V6 with a simple change of the cathode resistor to bias it properly. If you do a variable cathode bias circuit you can swap out the power tube with whatever suits you... 6V6 6L6 5881 KT66 KT77 EL34.

You can find how to do that over at AX84.com in the Core Projects/Building Blocks. Look at the single ended power amp projects.

You can also find some low power push pull designs there but not using a 6V6 or EL84. They use some smaller triodes for low power output, like in the 2W range.

[GeorgeG]

You should be able to replace that KT77 with a 6V6 with a simple change of the cathode resistor to bias it properly. If you do a variable cathode bias circuit you can swap out the power tube with whatever suits you... 6V6 6L6 5881 KT66 KT77 EL34.

You can find how to do that over at AX84.com in the Core Projects/Building Blocks. Look at the single ended power amp projects.

You can also find some low power push pull designs there but not using a 6V6 or EL84. They use some smaller triodes for low power output, like in the 2W range.

Thanks

I am going to try a 6V6 in my current design which does have variable bias.

How does a single ended vs push pull EL 84 sound? How are they different besides volume?

Thanks,

George

[kagliostro]

Despite the fact I love Tube & Tube Amps, I'm not a musician, more a passionate "technician"

so I can't give you an answer about the differences in tone you can expect from a 6V6 vs an EL84 (or 6L6 vs EL34)

but I want to point your attention to this

A 6V6 (6L6) tube has a lower sensitivity (Mu or mA/V or Siemens if you prefer)

so you see a 6V6 having a sensitivity of 4.1mA/V vs an EL84 that has a sensitivity of around 11mA/V (your KT77 has 10.5mA/V)

a higher mA/V value mean the tube require less drive to give the max output power (and compression/distortion)

and this is an important aspect

then, obviously there are other, more tone related, considerations

may be you can find something of your interest here

https://www.premierguitar.com/articles/Everything_You_Ever_Wanted_to_Know_About_Output_Tubes

Ciao

Franco

[frankenxtein]

I use humbucker pickups and own one guitar with single coil pickups so , there might be some difference in end results ........that dirty sound ......  the master volume control in RobRob's 5e3 Deluxe Micro ...... , I've used on SE 6aq5 , el84. mashups of Kalamazoo #1 and the 5e3 preamp.
The 6aq5 used a 500k MV pot alone for the gridstopper and the 6aq5 could just as well be a 6v6.
      The el84 used a 250k MV pot with a 100k resistor in series. I have two versions of the el84 amp. The two el84 amps can get that feedback sound more easily .... no pedals

The PP Deluxe Micro a low volume nasty amp.
https://robrobinette.com/Deluxe_Micro.htm

My version of the Deluxe Micro uses a a 12at7-12bh7-ez81 , a 12ay7 would be a cleaner choice in V1. 12ax7 a bit too dirty. V2 could be 12au7 or 12bh7 I went with the 12bh7 to work with a lower primary impedance output transformer. Got to watch that 6.3v heater draw with the micro amps.

http://el34world.com/Forum/index.php?topic=21486.0#msg231606
http://www.tdpri.com/threads/deluxe-micro-pp-12bh7.706525/

[GeorgeG]

I use humbucker pickups and own one guitar with single coil pickups so , there might be some difference in end results ........that dirty sound ......  the master volume control in RobRob's 5e3 Deluxe Micro ...... , I've used on SE 6aq5 , el84. mashups of Kalamazoo #1 and the 5e3 preamp.
The 6aq5 used a 500k MV pot alone for the gridstopper and the 6aq5 could just as well be a 6v6.
      The el84 used a 250k MV pot with a 100k resistor in series. I have two versions of the el84 amp. The two el84 amps can get that feedback sound more easily .... no pedals

The PP Deluxe Micro a low volume nasty amp.
https://robrobinette.com/Deluxe_Micro.htm




My version of the Deluxe Micro uses a a 12at7-12bh7-ez81 , a 12ay7 would be a cleaner choice in V1. 12ax7 a bit too dirty. V2 could be 12au7 or 12bh7 I went with the 12bh7 to work with a lower primary impedance output transformer. Got to watch that 6.3v heater draw with the micro amps.

http://el34world.com/Forum/index.php?topic=21486.0#msg231606
http://www.tdpri.com/threads/deluxe-micro-pp-12bh7.706525/

Very interesting site, I'll take a closer look and consider one of these micro power amps.


George

[smackoj]

Here is my favorite low power amp. A single ended design using a 6v6 power tube, a 12ax7 and a 5Y3. This is Valco's competitor to the Fender Champ.

[frankenxtein]

Despite the fact I love Tube & Tube Amps, I'm not a musician, more a passionate "technician"

so I can't give you an answer about the differences in tone you can expect from a 6V6 vs an EL84 (or 6L6 vs EL34)

but I want to point your attention to this

A 6V6 (6L6) tube has a lower sensitivity (Mu or mA/V or Siemens if you prefer)

so you see a 6V6 having a sensitivity of 4.1mA/V vs an EL84 that has a sensitivity of around 11mA/V (your KT77 has 10.5mA/V)

a higher mA/V value mean the tube require less drive to give the max output power (and compression/distortion)

and this is an important aspect

then, obviously there are other, more tone related, considerations

may be you can find something of your interest here

https://www.premierguitar.com/articles/Everything_You_Ever_Wanted_to_Know_About_Output_Tubes

Ciao

Franco

Very interesting info , there's quite a difference between those tubes. Thank you Franco

[GeorgeG]

How do find the noise levels in the layouts on the robrobinette.com site that you suggested?