You could use it in a CLC supply for this 50w Single-Ended BAF2015 Schade Enabled or the SIT variation.
Yes, for a low loss high current filter choke they could be used (up to 28A as far as I remember).
I also disassembled the PSU for the MoFo's and the filter chokes used are more appropriate for such use I think. They are dual chokes (on same core) so I can couple them serial or parallel depending if I want up to 2 or 4 A current.
It may be good to have some iron on the shelf
Attachments
Short of solving my puzzle, adding a step up transformer on the frond end w/ DC 490R on the MoFo side is a viable work-around.
Even looking at the schematic, I have no idea what could be causing the problem.
Even looking at the schematic, I have no idea what could be causing the problem.
Hi all, I'm assembling the parts for a MoFo.I read the complete thread yesterday (made my eyes ache) but two questions if I may.
1) My PCB has provision for R6, which I won't need. Do I need to put a wire link in its place.
2) My microwave transformers have a DCR of 2.2 ohms, what power supply voltage would be suitable ? I was thinking 22v-24v and trying to bias up at 2.0 - 2.5A.
1) My PCB has provision for R6, which I won't need. Do I need to put a wire link in its place.
2) My microwave transformers have a DCR of 2.2 ohms, what power supply voltage would be suitable ? I was thinking 22v-24v and trying to bias up at 2.0 - 2.5A.
Raising the input impedance?
I have a buffer pre that swings 1V and wants to see a minimum 10k load. I want to get the voltage gain from an autoformer. I'll need a 12x voltage step-up to swing a 24v supply on a Big MoFo. That's 144x impedance factor, which will bring the MoFo's 50k input impedance way too low.
Can I raise the input impedance by increasing R1 and the bias network values?
My math says I'll need 3MOhms - quite a change.
Will this kill the magic?
I have a buffer pre that swings 1V and wants to see a minimum 10k load. I want to get the voltage gain from an autoformer. I'll need a 12x voltage step-up to swing a 24v supply on a Big MoFo. That's 144x impedance factor, which will bring the MoFo's 50k input impedance way too low.
Can I raise the input impedance by increasing R1 and the bias network values?
My math says I'll need 3MOhms - quite a change.
Will this kill the magic?
> Can I raise the input impedance by increasing R1
Yes; but you can not wind a wideband audio transformer for 1Meg impedance.
10k is more practical. 1:12^2 levered makes 70 Ohm input.
This wants a "power" amplifier. 32 milliWatts on paper but better have 1/10th Watt on hand. Yes, could be one of the DSL/headphone chips.
Also a 1:12 step-up misses most of the benefit of an AutoTransformer.
Yes; but you can not wind a wideband audio transformer for 1Meg impedance.
10k is more practical. 1:12^2 levered makes 70 Ohm input.
This wants a "power" amplifier. 32 milliWatts on paper but better have 1/10th Watt on hand. Yes, could be one of the DSL/headphone chips.
Also a 1:12 step-up misses most of the benefit of an AutoTransformer.
PRR, thanks for the response. I'm still wrapping my head around how best to use audio transformers.
I guess I'm not clear on the distinction between the impedance rating of a transformer (such as 10K/600 or 10K/150) vs. what the driving stage will 'see' of the driven stage. I thought a listed 10k impedance can drive anything from 100k up.
Where are you getting the power figures you mention?
'a 1:12 step-up misses most of the benefit...' - I don't know what you're referring to here. Can you explain?
Otherwise, you don't see any problem with such a large increase to the resistance values on the front of the MoFo?
Thanks again.
I guess I'm not clear on the distinction between the impedance rating of a transformer (such as 10K/600 or 10K/150) vs. what the driving stage will 'see' of the driven stage. I thought a listed 10k impedance can drive anything from 100k up.
Where are you getting the power figures you mention?
'a 1:12 step-up misses most of the benefit...' - I don't know what you're referring to here. Can you explain?
Otherwise, you don't see any problem with such a large increase to the resistance values on the front of the MoFo?
Thanks again.
If your DAC or 'phones output cannot drive this impedance/capacitante level (capacitance, due to MoFo input capacitance multiplied by the turns ratio, and transformer own self capacitances), you can build a Mini Mofo for impedance buffering, for example, like something with IRF610 at 100mA bias and 10V power supply, and can use a small choke capable to 100mA DC biasing, and drives the trafo with this buffer.
This is one only example
Various buffering suggestions are mentioned on this pages; pick one that you like more
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Only across the RCA line outs... The headphone jack doesn’t. Get/make a cable to run it from the jack. Also report back with how loud the ACP+ runs the MoFo with the volume wide open.
6L6, Thanks for pointing this out on the ACP+ thread. I am currently running it off the HP jack with a transformer. I ran it with out somewhere along the way. Given that I then added a trafo, I can confidently say about the volume with out: it wasn't loud enough Low/moderate listening level w/ 81dB speakers.
DIYBras,
I am VERY interested in any and all details about a Mini MoFo you have to share. Have you built one?
I proposed exactly this last year, but it wasn't well received. The notion was suggested again a few months later, but the conversation didn't get in to details.
What inductance will the Mini's choke need to cover 20Hz? Do I still want to keep DC resistance down near 1v?
Would it be possible to use the transformer's primary to load the Mini's mosftet in place of the choke? Seems like this would eliminate the output cap along with the choke.
In principle, I could of course buy some parts and start tinkering. But given my inexperience, that sounds like a recipe to end up with something that either sounds bad our doesn't make any sound at all
Low/moderate listening level w/ 81dB speakers.DIYBras,
I am VERY interested in any and all details about a Mini MoFo you have to share. Have you built one?
I proposed exactly this last year, but it wasn't well received. The notion was suggested again a few months later, but the conversation didn't get in to details.
What inductance will the Mini's choke need to cover 20Hz? Do I still want to keep DC resistance down near 1v?
Would it be possible to use the transformer's primary to load the Mini's mosftet in place of the choke? Seems like this would eliminate the output cap along with the choke.
In principle, I could of course buy some parts and start tinkering. But given my inexperience, that sounds like a recipe to end up with something that either sounds bad our doesn't make any sound at all
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stevenrotterdam - can you explain what a 'difficult' transformer means?
6L6 - I'm using an Edcor XSM10K/150, 1:8.2.
I'm using it as a transformer, not an autoformer. I'm using the center tap on the low/primary side. This give a DC resistance of 30R which is what the ACP+ is designed around. It also doubles the turns ratio to 1:16.4 for ample voltage swing. I'm currently running a 20V brick supply at a cautiously low bias. I haven't tried opening the volume all the way up yet.
When I first wired it up I ran the primary between the RCA signal and ground pins, and the secondary between the MoFo input leads. This produced an audible hum. Connecting all the grounds together fixed it. I've build this on a wooden board w/ a plastic plate to mount the terminals, so no chassis ground. I was expecting to be able to have full isolation via the trafo with the initial connections. Apparently I still don't quite understand transformer isolation.
This is my second SE class A amp. The first one was an ACA. So I don't have a ton of listening experience with this topology. That said - this sounds amazing More detail than I've ever heard out of my little Classix II speakers, and occasional sound stage out past them to either side.
6L6 - I'm using an Edcor XSM10K/150, 1:8.2.
I'm using it as a transformer, not an autoformer. I'm using the center tap on the low/primary side. This give a DC resistance of 30R which is what the ACP+ is designed around. It also doubles the turns ratio to 1:16.4 for ample voltage swing. I'm currently running a 20V brick supply at a cautiously low bias. I haven't tried opening the volume all the way up yet.
When I first wired it up I ran the primary between the RCA signal and ground pins, and the secondary between the MoFo input leads. This produced an audible hum. Connecting all the grounds together fixed it. I've build this on a wooden board w/ a plastic plate to mount the terminals, so no chassis ground. I was expecting to be able to have full isolation via the trafo with the initial connections. Apparently I still don't quite understand transformer isolation.
This is my second SE class A amp. The first one was an ACA. So I don't have a ton of listening experience with this topology. That said - this sounds amazing
More detail than I've ever heard out of my little Classix II speakers, and occasional sound stage out past them to either side.For a transformer to be used as the choke load it needs to be airgapped to handle the DC current, and I am sort of sure that the dcor isn't.
So a custom transformer is probably needed, something like small SE- tube amp OPT.
I dont directly see if the same millihenries are needed, or that it should be more to keep in proportion with the smaller current. Also with a step-up above 5 things like capacitances and frequency range might become a problem.
So a custom transformer is probably needed, something like small SE- tube amp OPT.
I dont directly see if the same millihenries are needed, or that it should be more to keep in proportion with the smaller current. Also with a step-up above 5 things like capacitances and frequency range might become a problem.