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Joined 2002
I have been researching and really haven't found a answer to my question about isolation tranny's for my Mono blocks im working on.. I was thinking about taking 2 x 1kva toroidals getting them made from plitron or victoria magnetics 110ac in 110ac out.. to isolate the wall ac between the amplifiers.. Humm is it worth it.. What about a ac line stabilizer.. i see them all over.. there not cheap either..
I'm look'n forward.....
to get to work tomorrow. Hell, we got a bunch of chokes like ringcores
EI cores, big guys down in the basement waiting for the junkyard.
Better go down there and get some before it is too late.
I'm also the lucky guy to have 100s of the top of the line Nch FETs
from IR, IXYS, APT you name it. Even components not in full production yet.
I think I'll go working this very sunday night.....
Intresting project / Mattias
to get to work tomorrow. Hell, we got a bunch of chokes like ringcores
EI cores, big guys down in the basement waiting for the junkyard.
Better go down there and get some before it is too late.
I'm also the lucky guy to have 100s of the top of the line Nch FETs
from IR, IXYS, APT you name it. Even components not in full production yet.
I think I'll go working this very sunday night.....
Intresting project / Mattias
Wow, that´s one h*ll of a transformer!
I´m sure it will eat fuses for breakfast
56 VAC equals to about 75 VDC which is a bit high for this kind of amplifiers. If you can find suitable chokes you can dumb a lot of voltage (without excessive heat) in a choke input filter.
Theoretically it would be nice but you would have to find or wind a pair of chokes that are up to it.
I´m sure it will eat fuses for breakfast
56 VAC equals to about 75 VDC which is a bit high for this kind of amplifiers. If you can find suitable chokes you can dumb a lot of voltage (without excessive heat) in a choke input filter.
Theoretically it would be nice but you would have to find or wind a pair of chokes that are up to it.
Amp still goes
The 53kg class A is still going. It's been a full 3 years now. I don't listen to it a whole lot myself but every morning after I leave for work the missus puts it on full blast for about an hour while she does stuff around the house. I rarely have something for this long - usually I pull it apart again to make something else from the parts.
The 53kg class A is still going. It's been a full 3 years now. I don't listen to it a whole lot myself but every morning after I leave for work the missus puts it on full blast for about an hour while she does stuff around the house. I rarely have something for this long - usually I pull it apart again to make something else from the parts.
I recently decided to build a MkII version of my choke loaded amp.
This time I´ll build monoblocks based on those old C-core chokes, 1 or 2 IRFP260 and a couple of surplus 24V 3,6A stabilized linear PSU´s.
I´m aiming for 20-25W per channel, a little lower than before due to the lower rail voltage. 20W should be more than enough and the heat problem will be a bit more managable.
This time I´ll also put some more effort in building a good VAS, probably some high gm low Rp triode feeding a pair of Lundahl LL1621 interstage transformers.
This time I´ll build monoblocks based on those old C-core chokes, 1 or 2 IRFP260 and a couple of surplus 24V 3,6A stabilized linear PSU´s.
I´m aiming for 20-25W per channel, a little lower than before due to the lower rail voltage. 20W should be more than enough and the heat problem will be a bit more managable.
This time I´ll also put some more effort in building a good VAS, probably some high gm low Rp triode feeding a pair of Lundahl LL1621 interstage transformers.
Amp cct.
In the first year or so the amp cct changed back and forth a little. Things like different feedback configurations, different kinds of drain loads on the voltage amplifier, bootstrapping etc etc. Anyway, here is what I finally settled on - remarkably like what I started out with actually. It has been *absolutely* reliable and the only shortcoming is that if you turn it off for 1 or 2 seconds then straight back on again, the bias servo amplifier goes full on... Not good. But she's pretty chunky so I just turn it off quick and wait for a minute till everything discharges properly.
Anyway, enough blabbing. Here's the cct. Nothing exciting to look at but after all this time I still can't hear any deficiencies in it.
In the first year or so the amp cct changed back and forth a little. Things like different feedback configurations, different kinds of drain loads on the voltage amplifier, bootstrapping etc etc. Anyway, here is what I finally settled on - remarkably like what I started out with actually.
It has been *absolutely* reliable and the only shortcoming is that if you turn it off for 1 or 2 seconds then straight back on again, the bias servo amplifier goes full on... Not good. But she's pretty chunky so I just turn it off quick and wait for a minute till everything discharges properly.Anyway, enough blabbing. Here's the cct. Nothing exciting to look at but after all this time I still can't hear any deficiencies in it.
Attachments
i've been reading this thread, and recently opened a big wall-wart in the hopes of making a nice small filament transformer, rewound with nice wire. the problem is, it's soaked with varnish. is there a nice, hopefully not too poisonous fluid that I could hang the little core in to dislodge the BOBBIN and let me take apart the laminations?
Re: Amp cct.
It is really cool!
May be couple of diodes between input legs of OpAmp will help a bit?
Circlotron said:In the first year or so the amp cct changed back and forth a little. Things like different feedback configurations, different kinds of drain loads on the voltage amplifier, bootstrapping etc etc. Anyway, here is what I finally settled on - remarkably like what I started out with actually.
Anyway, enough blabbing. Here's the cct. Nothing exciting to look at but after all this time I still can't hear any deficiencies in it.
It is really cool!
May be couple of diodes between input legs of OpAmp will help a bit?
Hi Tyimo
Interesting set of figures.
Here are the ones from my number cruncher:
turns 409
core pattern 120 (Imperial) EI150 (US)
assume M6/0.35 grade, square stack
B=0.6T (needs to be lower than Bmax for AC+DC operation)
gap 2.5 mm (big gap)
wire around 1.37 mm dia.
THink this is a big choke, maybe would be expensive. Possibly better to run lower resistance (bigger still) if you directly couple the speaker across it. Or use large capacitor, but then may get strange LF oscillations?
Don't guarantee results. Sorry, haven't even sanity checked. I'd be interested in how close the results are if you ever try this.
cheers
John
Interesting set of figures.
Here are the ones from my number cruncher:
turns 409
core pattern 120 (Imperial) EI150 (US)
assume M6/0.35 grade, square stack
B=0.6T (needs to be lower than Bmax for AC+DC operation)
gap 2.5 mm (big gap)
wire around 1.37 mm dia.
THink this is a big choke, maybe would be expensive. Possibly better to run lower resistance (bigger still) if you directly couple the speaker across it. Or use large capacitor, but then may get strange LF oscillations?
Don't guarantee results. Sorry, haven't even sanity checked. I'd be interested in how close the results are if you ever try this.
cheers
John
this just in: i've taken apart two largish wall-wart-sized transformers, one dry and one having soaked for a day in acetone. the one with acetone, aside from the deadly fumes, came apart MUCH more easily than the dry one, and the varnish seemed to have been dissolved somewhat. unfortunately i used a razor to separate the laminations and sometimes scratched the iron - is this a problem? p.s. where can i find out the max. current for various thicknesses of wire?
Hi John!
Thanks for the help!
I am not sure what does it mean "120 Imperial"?
I know the EI150: I could use from 50/50 to 50/100 bobbins.
The 2.5mm gap is realy big!
Circlotron made his chokes from Microwave owen transformators and he used very little gaps and offcourse less turns.
Could you calculate the choke with my datas?
Greets:
Tyimo
Thanks for the help!
I am not sure what does it mean "120 Imperial"?
I know the EI150: I could use from 50/50 to 50/100 bobbins.
The 2.5mm gap is realy big!
Circlotron made his chokes from Microwave owen transformators and he used very little gaps and offcourse less turns.
Could you calculate the choke with my datas?
Greets:
Tyimo
Hi Tyimo
Just need to confirm your iron
is the centre section 40 x 50 mm
you mentioned EI120
normally this refers to US sizes (core length in inches) but the nearest I have in tables is EI125 (which has centre width 1.25 inches)
If you can let me know the centre core dimensions (height of stack x width across centre core) and the outside dimensions (iron width and depth overall, excluding any frame/mounting) I can have a go.
Cheers
John
Just need to confirm your iron
is the centre section 40 x 50 mm
you mentioned EI120
normally this refers to US sizes (core length in inches) but the nearest I have in tables is EI125 (which has centre width 1.25 inches)
If you can let me know the centre core dimensions (height of stack x width across centre core) and the outside dimensions (iron width and depth overall, excluding any frame/mounting) I can have a go.
Cheers
John
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