Dual choke on crack

[JamieMcC]

With a single choke you should be able to use 50-100uf for the last cap in the power supply and still achieve a massive improvement in ripple. If using two chokes the last cap potentially running a psu simulation shows (if I have configured it properly *doubtful*) then 5uf would achieve similar results in reduction of ripple to a single choke and a 100uf cap. What effect sonically this would have I don't have a clue perhaps PJ or PB might comment.

I have used 100uf film cap with a single choke and I couldn't really make out much different between using it and a 200uf film cap that I tried later. You will need to look closely at the dimensions of a 200uf film cap as they are big you will run out of ground clearance very quickly I ended up building a slightly larger enclosure.

Some pics here of the install here

http://bottlehead.com/smf/index.php?topic=5284.msg50967#msg50967

[Paul Joppa]

AS I have said before (though not recently) the last PSU cap is in seroes with the output cap and the power tube - that make up the signal current loop. Thus the effective output capacitance is the series impedance of the output - for example, if both caps are 100uF then the headphone sees a net 50uF. Not a problem for 300-ohm phones. but noticeable bass loss for 30-ohm phones.

[Paul Joppa]

I should have mentioned that the CrackaTwoa has a shunt regulator in place of the last PSU cap, so only one cap is in the signal current loop.

[Tom-s]

Thanks you for the replies. I found that with some dremel work. It would be possible to top mount a pair (could save 2-3mm on each side of each choke). Will do a temporary setup first. And if i like the sound, the look and if there's no magnetic interference i make it permanent. (For now i'm waiting on the parts to arrive).
This leaves me with much more space under the hood.

Of the guys with 2 chokes. It didn't influence the sound in any negative way?

Still in doubt about that magnetic interference Grainger mentioned earlier.

[Paul Joppa]

If the chokes are mounted as on the SEX amp, they will be in a null from the power transformer field and there should be no magnetic interference. Make sure they are centered fore-and-aft; even 1/4 inch makes an easily measured difference.

Feed the leads through a rubber grommet-lined hole between choke and power transformer, that way they are pretty inaccessible, improving the safety. There's not much room for that hole, so measure carefully!

[fullheadofnothing]

According to the datasheet, the C7-X has the same dimensions as a PC-3.

Attached is a picture of a PC-3 on a Crack chassis. Where are you planning to put the power switch and power inlet...?

[Paul Joppa]

My mistake - earlier I said 2.00 inches wide; it's actually 1.75". Lam stack is 1.00" but the bobbin flanges are 0.375" each side. I have corrected my earlier post - sorry for the error!

In either case, the planned location can work as long as the outer flange extends past the aluminum chassis pate.

[fullheadofnothing]

The data sheet says 2" wide, including the bobbin. Mounting holes are 2.812" apart (full flange width 3.312"). You could squeeze it in the space, but you couldn't align the centers.

[Paul Joppa]

The data sheet says 2" wide, including the bobbin. Mounting holes are 2.812" apart (full flange width 3.312"). You could squeeze it in the space, but you couldn't align the centers.

<sigh> yeah, you're right. I did not allow for an extra margin in bobbin sizing. The one behind my head on the shelf is the old style, layer wound without bobbin - my caliper says 1.874" wide.

It looks to me like you could fit it on the input jack side but would have to move the power switch and IEC socket on the other side.

[Tom-s]

So it would be possible if both were perfectly aligned with the PS exactly in between.
This wasn't my planning. I hoped to be fine with both sticking out an inch on the front of the PSU.
So in the end, it's not going to work without moving the on/off and IEC socket.

Edit; So i'm probably just moving to a toggle switch that mounts behind the PS.
I can cut off the mounting part off the choke that comes in front of the power inlet. And that side is then mounted from underneath using the hole left by the current switch.

[drewh1]

Curious what film caps you guys recommend for this application.  A mundorf won't fit in my crack because I already have two and and a choke stuffed in there.

[Tom-s]

There's a lot of info on this topic. I've searched extensively before i asked my current question.
I'm planning on Ansar film cap because a 220uf is only 60d * 82mmL (and is custom, so lower capacitance lowers the diameter).

Found confirmation that probably going bigger = better; http://bottlehead.com/smf/index.php?topic=6131.msg59443#msg59443
A big topic on the subject : http://bottlehead.com/smf/index.php?topic=4659.msg43999#msg43999
Also found film cap suggestions: http://bottlehead.com/smf/index.php?topic=7554.msg72765#msg72765
About bypassing caps in de PS: http://bottlehead.com/smf/index.php?topic=6247.msg60830#msg60830
How about using 2 caps vs 3 caps: http://bottlehead.com/smf/index.php?topic=3516.msg31144#msg31144
And more on the subject: http://bottlehead.com/smf/index.php?topic=1762.msg13041#msg13041

[drewh1]

Thanks