Aikido heaters

[cbutterworth]

I should have posted this in my previous message, but here goes:

I am using 6.3VAC to feed my 6sn7's. The heater power comes from a separate transformer than that used for my B+.

John Broskie's PCB (stereo octal) comes with very good instructions. However, I did find the section on tube heaters to be a little confusing (probably not due to John).

The instructions, in the section on heaters, says that 6.3V can be used if Jumpers 1 and 4 are used. It goes on to say that if the heater shunt caps are either omitted or replaced with 0.01uF ceramics, AC can be used. Anyway, I added caps (maybe I should remove them).

However, on the instructions' schematic, it says that for 6.3V heaters and a 6.3V supply, Jumpers 2, 3, 5, 6 should be used (NOT J1 and J4). I wired Jumpers 2, 3, 5, 6.

Does anyone know what I should do to correctly set-up my 6.3V heaters for a 6.3VAC power supply that is center-tapped to 1/4 B+ as I am suspicious that some hum issues may reside in my current heater configuration???????

Regards,
Charlie

 

[Alain Dupont]

cbutterworth,

There are 2 way's to build the heater circuit of an Aikido

and 6SN7 tubes {heater in 6.3 volts}

in your case:
1)- 6.3 volts either AC or DC
2)- 12.6 volts either AC or DC

1)- in the 6.3 volts and 6SN7 tubes the heaters are wired in parallel or //
2)- in the 12.6 volts and 6SN7 tubes the heaters are wired in Serie

Looking at the schematic in page 5 of the manual...

1)- 6.3 volts ==> Jumpers: 2 ; 3 ; 5 ; 6

2)- 12.6 volts ==> Input tubes: 4
& Output tubes: 1

Final: in AC = No cap's on the heater circuit for AC
in DC caps 7 ; 8 ; 9 ; 10 must be installed...

Charlie, there are no precise specifications for a AC or DC heater circuit,
Only to Twist the 2 vires from the transformer to the board {2 to 3 turns by inch};
and keep them as close to the chassis as possible... if you cross other circuits
do it at a right angle if possible...

>>> Heater center-tapped to 1/4 B+
Prefect here.

Regards.

Alain.

 

[pchw]

Hi Alain,

I ordered both the octal and the 9-pin Aikido PCB's. The octal's heater jumpers instructions make sense, but I am somewhat confused by the 9-pin.

The instructions are essentially the same as the octal except the pin numbers are 4 instead of 7 and 5 instead of 8. So, if I use a 6.3 filament transformer and set the jumper j2, j3, j5, j6, I will be parallel connecting the pin 4 and pin 5 of the tubes. Am I interpreting that right? If so, how would that work on the 12A?7 tubes? For this tube family, I think 12.6V PS connects to pin 4 and 5, and 6.3V connects to pin 4/5 (strapped) and pin 9? Looks like 6.3 PS can only be usd for tubes like 6DJ8 on this board.

Thanks,

Fred

 

[Alain Dupont]

Fred,

Well it's my "Aikido day" ; now for the 9 pin's

1)- 6.3 volts heaters AC or DC
2)- 12.6 volts AC or DC

1)- For the 6.3 volts heaters
Jumpers in: 2 ; 3 ; 5 ; 6

2)- For the 12.6 volts heaters
Input tubes 6.3 volts Jumper in: 4
Input tubes 12.6 volts Jumpers in: 5 ; 6

Output tubes 6.3 volts Jumpers in: 1
Output tubes 12.6 volts Jumpers in: 2 ; 3

Same thing as previous message for
- capacitors in case of DC
- wires
- heater polar to B+

Tubes in the manual:

(outputs) V1, V4 =
6AQ8, 6BQ7, 6BS7, 6DJ8, 6CG7, 6GM8, 6H30, 6FQ7, 6N1P, 6N27P
E80CC, ECC81, ECC82, ECC83, ECC86, ECC88, ECC99
12AT7, 12AU7, 12BH7, 12DJ8, 12FQ7, 5963, 5965,

(inputs) V2, V3 =
6AQ8, 6BQ7, 6BS7, 6DJ8, 6CG7, 6GM8, 6FQ7, 6N1P, 6N27P
5963, 5695, 6072, E80CC, ECC81, ECC82, ECC83, ECC86, ECC88
12AT7, 12AV7, 12AU7, 12AX7, 12BZ7, 12DJ8, 12FQ7, 5751

Be aware that some of these tubes may be wired for 6.3 And 12.6 volts...

So to be more precise, please give me the tubes you want to use
for Input as for Output.

Regards.

Alain.

 

[cbutterworth]

Alain,

Thanks, I did what you suggested, I removed the shunting caps and the hum has diminished, but not completely. It may be that microphonics from the chassis may be having an effect, along with the really cheap 6sn7s. I did read somewhere that some tubes can be more susceptible to hum than others.

Regards,
Charlie

 

[Alain Dupont]

Charlie,

I have a pretty collection of 6SN7 GTB's NOS pair's
from 6SN7GTB's RCA, Dumont, WestingHouse, SOVTEK etc
and 4 * 6SN7 EH

You should try some to get lower microphonics...

I got pretty good results with the Electro Harmonics, and Dumont
for this purpose.

PS: Check for hum from the B+
with a scope, depending on your HV PS design...

And also in the Aikido check for precise resistors on the PS noise cancelling circuit
C4-R15 and R16 depending on your tubes... worth a try!

Regards.

Alain.

 

[pchw]

Hi Alain,

I have quite a few of 12AT7, 12AU7, 12AX7, and 6DJ8 for the 9 pins. I plan to use the "remainings" of either:
1. Eico HFT-90 tuner chasis + PT (210-0-210/50ma and 6.3/2.6A), or
2. Eico HF-12 mono-integrated chasis + PT (280-0-280/70ma and 6.3/3.5A)
There is no CT on the heater's secondary.

If I use all 6DJ8, I believe I can simply use the 6.3V PS jumper setting; however, I am not sure this work if I use any of the 12A*7 for input or output or input/output because this jumper settings effectively wire pin 4 and 5 in parallel. My understanding is that the 12A*7 tubes need 12.6V when wiring the PS to pins 4 and 5. To use 6.3V on these tube family, I will have to strap pins 4 and 5 and wire the PS to pin 4/5 and pin 9. It seems to me that the 6.3V PS jumper settings can't be used for the 12A*7 tubes. I am very much a newbie, so I wonder I miss read something here.

Due to the uncertainty, I am thinking about using a voltage doubler from the 6.3 section which will give me 12VDC. But then I won't be able to use the 6x4 or the EZ81 tube rectifier as they have 6.3V heaters. What a bummer!! Any suggestion?

Thanks,

Fred

 

[tinear9]

Hi Charlie

Hum is tough. There are many causes and "cures". When you reach the point that its no longer fun to wrestle with it, give me a shout and I will come over again and see what we can figure out together. I have plenty of different 6SN7's, rubber standoffs for the power trans (mine has a little buzz also but if it isn't mechanically coupled to the audio circuit this seems to be no problem), and very strong ideas about heater bypasses (do NOT remove the small high quality ceramic caps at the heater pins).

Many have reported success with AC on line amp heaters. I use DC on my Aikido phono/line with good results. That may be the easiest cure but we don't want to give up on your first choice without a good fight, do we. Good luck!