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Heaters wiring help!

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cjkpkg

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Joined 2008
#1
OK...I need some help...I have hit the wall with this and I know it should be simple...

I am having a hard time visualizing the heater schematic for my build - 6N1P - EL84 PP amp.

12.6V heater voltage DC

Does it really matter +/- voltage on pin 4 or 5?

Does this scheme make sense? Is there a better route?

heaters1.jpg
 
#2
It's better to keep the + and - wires twisted together at all times. To keep the required wire gauge down, you could use one twisted pair which goes to the two el84 at the left and then the 6n1p, and a second pair which does the same for the other channel.
 
#3
Why 12.6 V DC? They are all 6.3 volt tubes. You are not building a phono pre amp here, so good layout with AC will give you no hum. I am re-working a 6N2P, EL84 amp laid out as yours is, but with AC heaters. I have no hum. With my latest 6L6 amp with regulated B+ I used AC heaters with absolutely zero hum.

Do you have Morgan Jones "Building Valve Amplifiers"? He goes in to great detail about heater wiring layout, RF decoupling with ceramic caps to chassis ground and lifting the heater voltage reference.

Applying technique here and with the grounding scheme is where you will get low hum.

Cheers,

Chris
 
#4
I am using JB's PS-4 PSU for this...and I have set it up for 12.6VDC.

I would have to wire the 6N1P's in series since they are 6.3V heaters. I guess I could run one wire set to the 6N1P's and another pair to the EL84's.
 
#5
cjkpkg said:
I am using JB's PS-4 PSU for this...and I have set it up for 12.6VDC.

I would have to wire the 6N1P's in series since they are 6.3V heaters. I guess I could run one wire set to the 6N1P's and another pair to the EL84's.
Click to expand...
Hello cjkpg,
This plan sounds good. Also tuck the heater conductors into the corner and tight to the chassis. I also bypass the heaters at the tube socket with a 10 uf electrolytic and small monolithic ceramic capacitor. The PS-4 has regulated H output and should be near quiet to start with.
DT
All just for fun!
 
#9
The use of black for + and red for - is the reverse of engineering convention, but frankly doesn't matter here.. Other than that fine.

Probably ought to float the whole filament supply on a dc bias of 30 - 40V (resistive divider from B+ with a cap from the floating filament bias voltage to ground) make sure there is a low impedance AC path to ground for your filament supply. Or you can use a resistive divider between +/- to ground with a pair of 100 ohm 1W resistors.
 
#12
Picture2-1.png


This is the one I used - the only changes I made were a CCS for the EL84 cathodes using a simple LM317 with a 15ohm resistor that yields 83mA of current. A little hot but the sound is terrific.

Iron is all edcor
tubes are sovtek 6n1p and EH el84s and sovtek 5ar4.
coupling caps are Auricap
the PSU section is a pcb from tubecad.com - the PS-4 which includes a DC heater section.
 
#13
Thanks.

I have built an EL84 PP with almost the same operating point as the your output, but I was using a 7119 as input/driver into a Lundahl 1660S. Sounds excellent, but the pair of Lundahls are quite expensive, so I want to explore the possibility of building an amp without the lundahls.

I like 6n1p, used it on my SE KT88 (Mikael Abdellah's circuit).
 
#14
kevinkr said:
................Probably ought to float the whole filament supply on a dc bias of 30 - 40V (resistive divider from B+ with a cap from the floating filament bias voltage to ground) make sure there is a low impedance AC path to ground for your filament supply. Or you can use a resistive divider between +/- to ground with a pair of 100 ohm 1W resistors.
Click to expand...

But not in this case since the supply is DC, right?
 
#15
I am using the tubecad PS-4 PSU - tube rectified B+ and DC regulated heater supply that is referenced to B+/4. In this case I used 12.6V and wired them all in series.

I went with the Edcor CXPP25-MS-7.6K and currently using the UL taps instead of "triode" mode.

I have been very pleased with the performance of this amp.

Picture1142.jpg
 
#17
I haven't tried triode yet. UL sounds really nice...by the charts probably about 11W with 330V B+.

I have a SimpleSE too. I most recently ran KT88's with the cathodes running about 108mA. Previously they were running about 70mA this made a huge difference. I also tried some SS rectification and had a B+ around 500V.

The PP amp does have more punch but not much.
 
#18
PHP: 
 KT88's with the cathodes running about 108mA

That's really hot. My SSE running a pair of Valve Art KT88, cathode resistor value as Tubelab suggests and will try change the cathode resistor value later. Anyway, good luck on your EL84 P-P new build.
 
#20
The Edcor CXPP25-MS-7.6K. I decided to go with the multiple secondary option because I have both 4 and 8 ohm speakers that are in rotation...they were only a couple bucks more anyways.

I swear when I bought them there was not an 8K option which was why I went 7.6K...although I would rather sacrifice a little power for lower distortion - I dont listen that loudly normally anyway.
 
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