12 gauge is around 2 mm, 14Ga ~ 1.6mm, 16 ~ 1.3mm
Mills: 81- 64-51
(teflon silver stranded is grand, and you can buy surplus everywhere for next to nothin, even by the foot)
Mills: 81- 64-51
(teflon silver stranded is grand, and you can buy surplus everywhere for next to nothin, even by the foot)
Ok, so If I edit those pads to 90mil, then they should be ok?
I assume the only board you're worried about is the output board, as the others need little current in comparison. Changing the others would be a pain as it would mean that for those that want to use terminal blocks for connections, the holes would be way too big.
I assume the only board you're worried about is the output board, as the others need little current in comparison. Changing the others would be a pain as it would mean that for those that want to use terminal blocks for connections, the holes would be way too big.
The best thing to do is just go to Jan's site www.deltaaidio.com and get all the info you need right off his site. Everything is there including the board mods that have to be done.
Al,
You might wanna download Jan's files off his site and see what size holes he used. I hate phoenix connectors. They are the shurest route to blown speakers when used on DC connections!
Mark
Al,
You might wanna download Jan's files off his site and see what size holes he used. I hate phoenix connectors. They are the shurest route to blown speakers when used on DC connections!
Mark
Transformer
Franco,
You will need two secondaries of ~26v AC each, with current of approx 2A per channel.
So 4A total for your pair, this is approx 220va. Adding a safety margin of 100% would suggest 450-500va would be a good starting point.
It seems Krell used 400va per channel, about 300% overrated.
Stuart
Franco,
You will need two secondaries of ~26v AC each, with current of approx 2A per channel.
So 4A total for your pair, this is approx 220va. Adding a safety margin of 100% would suggest 450-500va would be a good starting point.
It seems Krell used 400va per channel, about 300% overrated.
Stuart
Re: Transformer
Hi Stuart,
I purchased a 30-0-30 500vA tranny for this amp. Is this going to be a problem for me?
Also, This may have been answered but what, if any, advantages are there to Al's design over Jan's design aside for the couple of corrections that needed to be made to the original?
Thanks, Terry
Stuart Easson said:
Hi Stuart,
I purchased a 30-0-30 500vA tranny for this amp. Is this going to be a problem for me?
Also, This may have been answered but what, if any, advantages are there to Al's design over Jan's design aside for the couple of corrections that needed to be made to the original?
Thanks, Terry
problems?
Terry,
The transformer you have sounds fine to me, by the time it is rectified, and then loaded by the amp the output voltage will be in the correct range. The limiting factor will be how hot you intend to run everything. I always start the idle current at the minimum then dial it in to about half what I think the heatsinks will allow, then over the course of a day I slowly increase it until I get to the 'specified' current or reach a temp at the limit of what I'm comfortable with.
Keep track of the transformer at the same time, chances are it will get warm, it shouldn't get smoking hot. The manufacturer will have a specification for the maximum temp. Some parts include a thermal fuse, if fitted this will be the absolute max, also some of the fuse things are non-resettable, so no hot accidents...
You have a little more voltage than you need, but you also have more current than you need, so you will probably get a little higher peak power, and depending on your heatsinks, you may end up with more (or less) class A than the spec'ced 50watts.
Stuart
Terry,
The transformer you have sounds fine to me, by the time it is rectified, and then loaded by the amp the output voltage will be in the correct range. The limiting factor will be how hot you intend to run everything. I always start the idle current at the minimum then dial it in to about half what I think the heatsinks will allow, then over the course of a day I slowly increase it until I get to the 'specified' current or reach a temp at the limit of what I'm comfortable with.
Keep track of the transformer at the same time, chances are it will get warm, it shouldn't get smoking hot. The manufacturer will have a specification for the maximum temp. Some parts include a thermal fuse, if fitted this will be the absolute max, also some of the fuse things are non-resettable, so no hot accidents...
You have a little more voltage than you need, but you also have more current than you need, so you will probably get a little higher peak power, and depending on your heatsinks, you may end up with more (or less) class A than the spec'ced 50watts.
Stuart
advantages...
Bearing in mind that I have only used Jans board so far...after assembling 5 channels I've not found any issues, so I don't think the differences are going to be critical. I didn't even cut the tracks, simply used trimmers that had legs long enough that they could be tweaked to fit the footprint.
If you use the original board, you could end up with a few unused spaces, eg on the big krell I mount the drivers on the main heatsinks, so the end of my board is largely empty, no limiters, no drivers, no resistors for the drivers etc.
I think the second board was a good way to take care of a few minor details and offer the result to those that missed on the first round.
HTH
Stuart
Bearing in mind that I have only used Jans board so far...after assembling 5 channels I've not found any issues, so I don't think the differences are going to be critical. I didn't even cut the tracks, simply used trimmers that had legs long enough that they could be tweaked to fit the footprint.
If you use the original board, you could end up with a few unused spaces, eg on the big krell I mount the drivers on the main heatsinks, so the end of my board is largely empty, no limiters, no drivers, no resistors for the drivers etc.
I think the second board was a good way to take care of a few minor details and offer the result to those that missed on the first round.
HTH
Stuart
Re: advantages...
Thanks Stuart,
I have the original boards and plan to use 3 pair TO-3 outputs
per channel on a Hafler P500 heatsink with a fan. These heatsinks seem fine for the Hafler but I'm not sure if it will hang with Class A. Also, how important is it to have the driver transistors on the same heatsink as the outputs? That might be a little tough to accomplish with these heatsinks.
Thanks, Terry
Stuart Easson said:
Thanks Stuart,
I have the original boards and plan to use 3 pair TO-3 outputs
per channel on a Hafler P500 heatsink with a fan. These heatsinks seem fine for the Hafler but I'm not sure if it will hang with Class A. Also, how important is it to have the driver transistors on the same heatsink as the outputs? That might be a little tough to accomplish with these heatsinks.
Thanks, Terry
drivers...
Terry,
Mounting the drivers on the main heatsink is accomplished the same way with either board, by using flying wires. Running a few 3 wire braids to the main heatsink is easy...
The drivers being seperate is no problem at all, put the VBE transistors with them on a piece of AL just the right size so it's temp is a little hotter (5c) than the main sink...since the dissipation in the drivers tracks the outputs, they will keep the VBE transistor at the correct temp...the driver heatsinks being at a temp close but hotter than the main sink is not critical either, but is a nice touch, the smaller sink will react much quicker than the main sink, so the biasing will actually work better...
Stuart
Terry,
Mounting the drivers on the main heatsink is accomplished the same way with either board, by using flying wires. Running a few 3 wire braids to the main heatsink is easy...
The drivers being seperate is no problem at all, put the VBE transistors with them on a piece of AL just the right size so it's temp is a little hotter (5c) than the main sink...since the dissipation in the drivers tracks the outputs, they will keep the VBE transistor at the correct temp...the driver heatsinks being at a temp close but hotter than the main sink is not critical either, but is a nice touch, the smaller sink will react much quicker than the main sink, so the biasing will actually work better...
Stuart
Here is where I am- big output stage (4 MJ's per rail/ 8 per channel) will be fan cooled, with a 120 mm 70cfm fan above the heat sinks blowing air out the top.
The heat sinks are LIVE, each section is + or - 42V. It looks impossible to mount the xistors without having these live as the TO-3 holes are tapped and threaded already. Either way this surplus heat sink looks to have been intended to have each section live and insulated from the other. See the insulating strips and the tube around the long bolts? I have taken great great care to keep everything well insulated and the case will be inaccessible to the normal user. I hate to have live heatsinks but I guess that's what you get with the parts on hand.
An externally hosted image should be here but it was not working when we last tested it.
and case drilled and ready to start wiring things up. All boards are constructed. You see the dual 700VA Xformers that are to be used for this.
An externally hosted image should be here but it was not working when we last tested it.
I'm going to have questions soon, when things start blowing up on me.
live heatsinks
If you can make it work you will get better thermal performance, though you will still need thermal paste under the cases...dry metal to metal is not always a good thermal connection without scrupulous attention to smoothness and polishing etc.
If you decide to 'deaden' your heatsinks...
There are nylon collars you can use to keep the bolts from touching the to3 cases. These plus a small solder tab to make the connection to the collector and you are in business. Of course the mica washers make the thermal connection less good, and you have to reassemble everything...
Stuart
If you can make it work you will get better thermal performance, though you will still need thermal paste under the cases...dry metal to metal is not always a good thermal connection without scrupulous attention to smoothness and polishing etc.
If you decide to 'deaden' your heatsinks...
There are nylon collars you can use to keep the bolts from touching the to3 cases. These plus a small solder tab to make the connection to the collector and you are in business. Of course the mica washers make the thermal connection less good, and you have to reassemble everything...
Stuart
I've got the "nylon collars" which are also known as shoulder washers. They can't be used because they insulate the screw from the output device and thus there is no place to connect to the collector.
The screw is threaded into the heat sink, so if you want to connect to the screw, you have to have live heat sinks or else bore out the nice threaded holes. I've thought about this a lot, if you don't bore out a hole you cant do it without having live sinks.
Good point about the thermal paste, actually there is thermal paste under the output devices as you can see from a close look at the pics.
The screw is threaded into the heat sink, so if you want to connect to the screw, you have to have live heat sinks or else bore out the nice threaded holes. I've thought about this a lot, if you don't bore out a hole you cant do it without having live sinks.
Good point about the thermal paste, actually there is thermal paste under the output devices as you can see from a close look at the pics.
Terry sayd:
"Also, This may have been answered but what, if any, advantages are there to Al's design over Jan's design aside for the couple of corrections that needed to be made to the original?
Thanks, Terry"
Thew further this tread goes, the more i asked myself the same question. The boards from Jan are good and looks even better than the 2e generation boards (imo).
Maybey not nice to say, but thats what i feel about it.
Its too late for it now, but I think too (see earyer post from another reader) that a new tread for the 2e generation board (hundreds posts earlyer) was a good idee. Its a form of Hyjacking.
If nylon collars get too hot, the design of the PCB is not good i.m.o.
Excuse my bad language and excuse my comments.
"Also, This may have been answered but what, if any, advantages are there to Al's design over Jan's design aside for the couple of corrections that needed to be made to the original?
Thanks, Terry"
Thew further this tread goes, the more i asked myself the same question. The boards from Jan are good and looks even better than the 2e generation boards (imo).
Maybey not nice to say, but thats what i feel about it.
Its too late for it now, but I think too (see earyer post from another reader) that a new tread for the 2e generation board (hundreds posts earlyer) was a good idee. Its a form of Hyjacking.
If nylon collars get too hot, the design of the PCB is not good i.m.o.
Excuse my bad language and excuse my comments.
used 'em differently...
The solder tabs of which I spoke go under the nylon collar, but on the transistor, so the collector wire comes from on top, then typically through a convenient hole drilled in the heatsink...
The tabs are not the 'usual' ones, in that they have to have a larger diameter hole, and be a little longer...
HTH
Stuart
PS I have even seen wires soldered directly to the TO3 case...
The solder tabs of which I spoke go under the nylon collar, but on the transistor, so the collector wire comes from on top, then typically through a convenient hole drilled in the heatsink...
The tabs are not the 'usual' ones, in that they have to have a larger diameter hole, and be a little longer...
HTH
Stuart
PS I have even seen wires soldered directly to the TO3 case...
sinks
If I could solder directly onto the TO-3 case, that would be the easiest way. But I'm not sure that its possible for me and my little iron to do that.
Stuart, got a link to those fancy tabs?
If I could solder directly onto the TO-3 case, that would be the easiest way. But I'm not sure that its possible for me and my little iron to do that.
Stuart, got a link to those fancy tabs?
Nope, sorry...
prolly best I can do is take a picture and get you dimensions...
I picked 'em up at the local electronics store, not Radio Shack, we are lucky enough to have the real thing a couple of miles away...
You can prolly find them at any good hardware store, though I haven't tried, just take along one of your shoulder washers to get a good fit...
Stuart
prolly best I can do is take a picture and get you dimensions...
I picked 'em up at the local electronics store, not Radio Shack, we are lucky enough to have the real thing a couple of miles away...
You can prolly find them at any good hardware store, though I haven't tried, just take along one of your shoulder washers to get a good fit...
Stuart