KT66SE

[6B4G]

Hi guys I've built pp amps in the past but never a se, I've looking at the Simple 7 Watt pr/ch
Ultra linear SE "office amp" with shunt feedback at http://www.veiset.net/5WCFBSET/7WPC.html.
I wanted to use the odds and ends I have but I haven't experiences or the expertise to do it.
Would someone be able to help me?
I have a Hammond 300BX 800vct 288ma
two 193J chokes 10H 200ma 82 ohm
and two 193N 3H 500ma 35 ohm
as for the output I've had for a long time now two James 3.5K special order opt's 20Hz-60KHz 100ma 20watt that I picked up on ebay.
I have heaps of caps, resisters etc for the project, I would say my biggest downfall is the ps.
It would be great if anyone else has built one.

Thanks guys.

[soundbrigade]

Seven Watt seems a bit optimistic, but have a look at the Clementinefound elsewhere on this forum. There are versions with 6L6 (KT66) that could work out for you.

[6B4G]

OK I really dint think about that I'll have a look. Thanks

[azazello]

EF184 in penthode mode has too much gain and really You will use a quoter of your input potentiometer.
I'd like to advice You to switch EF184 in troide mode /if You will use 6L6, EL34, KT66 with grid -U about 25 v/ - Disconnect from 2 grid 47 kohm and 2 uF and switch it to plate, and disconnect 220 kohm between both plates. You can connect input potentiometer 10 kohm. You will have about 3-4 W with very clean and audiophil sound.

[Geek]

I'd like to advice You to switch EF184 in troide mode....

Azazello is wise

[kheper]

I'd like to advice You to switch EF184 in troide mode....

Azazello is wise

Ditto. Pentode drive is not recommended.

I have a Hammond 300BX 800vct 288ma
two 193J chokes 10H 200ma 82 ohm
and two 193N 3H 500ma 35 ohm
as for the output I've had for a long time now two James 3.5K special order opt's 20Hz-60KHz 100ma 20watt that I picked up on ebay.

The power transformer in your schematic is a 300-0-300. You have a 400-0-400. For the KT-66 in SE, you may want to run it lower than 400vdc. Your power supply will produce about 540Vdc with a SS FW rectifier. The 193J choke is perfect, however.

You could build a simpler SE amp:
http://diyaudioprojects.com/Tubes/KT88

[TerrySmith]

I see two forms of feedback in the original circuit, global FB from the output to the EF184 cathode and plate to plate FB similar to an RH-84. Is it possible it needs the pentode gain front end?

The 6L6GC is fixed bias, that may account for an extra watt or two.

EDIT - Make that three forms of FB, I missed the 2uf cap from the EF184 screen to cathode.

[azazello]

Little bit more power You will receive connect to cathode EF184 to ground quality capacitor about 500-1000 uF/6-10 v,/ELNA, Nichicon, Black gate, Panasonic..../
Fixed bias is the best mode for 6L6 with the best sound, IMNO.
And You can try disconnect and Global NF and decide how You will listen...with or without. With NF mode is little bit linear, but sound is dry /I prefer without with more fresh sound/.
Good listening!

[6B4G]

Thanks guys for helping, another change, I tested and found that the opt is not 3.5k but 2,5k.
any thoughts.
Also re the B+ will it drop enough by using the 193J?
or will I have to increase the 47R/5W resister?

Cheers

[6B4G]

I've made some changes can you please have a look.

[azazello]

If Your output transformer is 2.5 kohm You must use 6L6 only in triode mode, connecting 2 grid to plate across res 500 ohm. Power will be about 3 W.
You can change both grid resistors 12 kohm for EF184 and 6L6 to 1 kohm.

[kheper]

Thanks guys for helping, another change, I tested and found that the opt is not 3.5k but 2,5k.
any thoughts.

If your transformer has 4ohm taps, putting 8ohm speakers on them will raise the impedance to 5k.

Also re the B+ will it drop enough by using the 193J?
or will I have to increase the 47R/5W resister?

Cheers

To get to 400Vdc, you'll need to increase both the resistor and the wattage values.

In your revised schematic, the screen grid on the EF184 is floating. Strap the screen to the plate with the 47ohm resistor or use the original schematic (no mods).

I think cathode biasing the output tubes may be better (and simpler).

[azazello]

Big mistake! Both plates are shorted. . You must disconnect them!
/Are You from? Greece? You can invite me in Bulgaria and listen my SE2A3, 300B, 4P1L, 6S4S, EL11Telefunken, OTL6AS7.....I will be after 2 weeks and make Your amplifier together/.

[6B4G]

Yes azazello I'm living in Greece, I've been here for just over 6 years. Originally from Australia and I wonder if it was a mistake LOL

[azazello]

Please, disconnect 47 kohm and 2 uF from 2 grid of EF184....and connect grid to plate.