I think pin 1 connects to the metal ring around the base. I would certainly ground it if you can, and certainly don't connect it to the plate!
6sn7, 6j5, 76's?
- Thread starter ALL212
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ALL212
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After thinking this over a bit I think I'm going to stick with the 6sn7 in the pre spot and leave the 6080 alone.
I can use adapters to go back to 12AU7's and also another adapter to go to 6J5's. Could even be adapters for 76's.
What I've found is that all but 1 of my headphones are 300 ohm. And the odd one is 30 ohm or less so we're not going to talk about him.
I've read on this forum about increasing the last power supply cap - maybe doubling it - so that the coupling caps can be much smaller than 100uf? Maybe down around 50 uf? That would assist in the budgeting aspect of putting film caps in that spot.
Is there an optimal value in the last power supply cap and the output caps for tuning the Crack to 300 ohm cans?
At this time I've got a choke here so power supply will probably be CRCLC. I previously found a post with a chart showing the 3db roll offs with different loads and output caps but of course, I can't find it today.
I have purchased the Speedball but I'm planning on leaving it out on this build until I've had plenty of listening time. I've not done that before and I'm curious so it might even stay out.
I also stole this from a 2013 post - still applies?
"Now, if you're going to decrease the output coupling cap, you can increase the 2.49K loading resistors a bit. If you're going to have about half the capacitance, then let's push those up to 4.7K resistors, which gives you a 530 Ohm load (yay!). This gets you down to 60uF, though I suspect anything from the mid 50uF-70uF range is going to work well."
So...short version. Is there an optimal power supply and loading resistor setup for 300 ohm cans that involve lessening the size of the output caps so that I can save some room and possibly put in higher grade boutique caps?
I can use adapters to go back to 12AU7's and also another adapter to go to 6J5's. Could even be adapters for 76's.
What I've found is that all but 1 of my headphones are 300 ohm. And the odd one is 30 ohm or less so we're not going to talk about him.
I've read on this forum about increasing the last power supply cap - maybe doubling it - so that the coupling caps can be much smaller than 100uf? Maybe down around 50 uf? That would assist in the budgeting aspect of putting film caps in that spot.
Is there an optimal value in the last power supply cap and the output caps for tuning the Crack to 300 ohm cans?
At this time I've got a choke here so power supply will probably be CRCLC. I previously found a post with a chart showing the 3db roll offs with different loads and output caps but of course, I can't find it today.
I have purchased the Speedball but I'm planning on leaving it out on this build until I've had plenty of listening time. I've not done that before and I'm curious so it might even stay out.
I also stole this from a 2013 post - still applies?
"Now, if you're going to decrease the output coupling cap, you can increase the 2.49K loading resistors a bit. If you're going to have about half the capacitance, then let's push those up to 4.7K resistors, which gives you a 530 Ohm load (yay!). This gets you down to 60uF, though I suspect anything from the mid 50uF-70uF range is going to work well."
So...short version. Is there an optimal power supply and loading resistor setup for 300 ohm cans that involve lessening the size of the output caps so that I can save some room and possibly put in higher grade boutique caps?
It certainly wouldn't hurt to put a 470uF 250v power supply cap in as the last cap.
The Crack-a-two-a will accommodate just about any 100uF film caps you'd like to use without any space constraints.
The Crack-a-two-a will accommodate just about any 100uF film caps you'd like to use without any space constraints.
70uF should be OK on the 300 ohm cans.
