Choke specs for the Crack

[EniGmA1987]

Are you going to put a choke in the power supply or as the plate load for the 12AU7?

If in the power supply the Triad C7-X is often used.

I am still a bit new to electronics and schematics and such, but am I correct in thinking that if the Speedball upgrade was installed, then the place where the plate load choke upgrade would normally go in the stock Crack is no longer correct since the Speedball replaces some of the plate load stuff? If I were to replace some resistors with choke while having the speedball installed which resistors would I be looking at replacing? Seems all the info covered so far is only about the power supply chokes part of that, nothing on the plate load choke idea.

[Grainger49]

Sorry, I can't help you with plate load chokes.

[Paul Birkeland]

We don't recommend plate loading chokes for the 12AU7, and I don't believe this has been done in the Crack.  The Speedball will offer better performance than a pair of plate loading chokes without taking up tons of space or picking up on radiated magnetic fields.  Plate loading chokes would also severely raise the 12AU7 plate voltage without additional modifications.

[Paul Joppa]

Concurring with PB here - a long time ago I made a 6BL7 preamp with switchable plate loads - four different inductances and a C4S. No question about it, more inductance was always better than less, and the C4S easily beat out the highest inductance.

[richmi]

Hello Gang,

I am preparing to install the C-7X choke. Is there any sense in twisting the two wires together or it does not matter?

My choke as a black dot next to one wire. Is there one "IN" and one "OUT"? Must that be considered at the time of connexion?

Thanks.

Richard

[Paul Joppa]

Yes there is some sense to twisting the wires (minimizing the current-loop area.

The choke works by reducing the current fluctuations of the power supply, but it does not of course completely eliminate them. The twisted wires reduce the magnetic hum field generated by the remaining fluctuations.

The most important twisting is the heater power wires, where the fluctuating current is very high - 2.5 amps for the 6080 heater.

The dot usually signifies the start of the winding, standard practice it to use that with the highest AC voltage, i.e. the input of a filter choke. In this application the difference will be very tiny, so don't stress.

[Jimb0]

Just installed mine

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi60.tinypic.com%2F103wduh.jpg&hash=123d87f270cb89c92a4e9c1f558a8ee88af30e04)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi60.tinypic.com%2F30ubp91.jpg&hash=b1f8fc831d7420a5b018c32a0e24dd87299afbc1)

[JamieMcC]

How are you liking it?

I fitted my choke and swapped out the last 220uf electrolytic capacitor with a film equivalent at the same time I liked the results and thought them easily noticeable. But very interested to hear your thoughts on the impact of the choke in combination with the stock electrolytic capacitors.

[richmi]

Thanks PJ for the concise and clear explanation, as usual.

I will twist the wires and connect them according to standard practices even if, as you state, it probably does not really matter in this case.

Richard

[Jimb0]

How are you liking it?

I fitted my choke and swapped out the last 220uf electrolytic capacitor with a film equivalent at the same time I liked the results and thought them easily noticeable. But very interested to hear your thoughts on the impact of the choke in combination with the stock electrolytic capacitors.

I'm not sure whether it's the choke or if I took a break off my headphones for a couple of days (I seem to notice details better when I don't use my headphones so often) but I think there is improved sound stage and clarity in the lows. My ears can be fooling me as it always does so I cannot know that for certain. As for the blacker background I can't really comment on that. I still need to buy a DAC for my desktop it seems because I can still hear a slight hum. I can only hear this hum when the Crack is connected to the PC but on my laptop it is dead silent. It does sound very nice so the choke may have improved the overall sound.

[i luvmusic 2]

Hammond 158M can it be use for the CRACK?Thanks!

[Tom-s]

Yes.

[i luvmusic 2]

Yes.

I just want to make sure,Thanks!

[i luvmusic 2]

Before i go ahead and install the CHOKE  i just want to confirm that this is to replace the 270R 5W under the two caps.Thanks!

[Paul Birkeland]

Either 270 Ohm resistor can be replaced by the choke.

-PB