Magura said:
Dear Morten,
i know the weather on your side in Danmark is lovely and overhere it is stinkin wet.
However, it is the bolting i would like to find an elegant solution for.
(on the other hand, i may pretend to go fan and con Santa Pass out of a fan controller for my kilowatt Krill 50's)
Probably we don't need to make the boards exactly fit the existing brackets, the HAfler has lots of room inside. but maybe we could have two holes on one side to fit the HAfler and two on the other to fit the Adcom.
We need to know abit more about the Adcom. It seems that the power supplys would be quite similar if they put out similar power.
I don't know how the boards are laid out though 'cause I don't have one. MAybe somone who does could tell us.
About the TO-3's,
Can we use the existing mosfets? Should we?, or will it sound lots better with modern ones? Sure it would be more in keeping with the E-Z build spirit to use To-3's , but probably not that difficult to use the plastic ones....
Nelson, if you end up doing a follow up article on this retrofit subject I suspect you will find keeping my amp to be a good idea.
I might get some labor out of you yet!!
For that reason, someone that has either an early Hafler, or Adcom GFA 555 model would certainly help by opening them up and taking some photos of the general interior, and measuring the size of the boards and mounting holes.
Mark
We need to know abit more about the Adcom. It seems that the power supplys would be quite similar if they put out similar power.
I don't know how the boards are laid out though 'cause I don't have one. MAybe somone who does could tell us.
About the TO-3's,
Can we use the existing mosfets? Should we?, or will it sound lots better with modern ones? Sure it would be more in keeping with the E-Z build spirit to use To-3's , but probably not that difficult to use the plastic ones....
Nelson, if you end up doing a follow up article on this retrofit subject I suspect you will find keeping my amp to be a good idea.
I might get some labor out of you yet!!
For that reason, someone that has either an early Hafler, or Adcom GFA 555 model would certainly help by opening them up and taking some photos of the general interior, and measuring the size of the boards and mounting holes.
Mark
PA asked
If it turns out these goals are in conflict, then perhaps we can do 2 different boards, but I suspect that we can devise a board that is small, nice looking, and also is easily installed in the amps mentioned in this thread. Thanks to your comment, I realized that the new boards don't have to be the exact size of the old amps boards. It would be nice however if they could be easily mounted to the existing amp hardware, and that's part of the fun- making a board that does all these things well
When we get to the group buy stage, we can create a wiki page and possibly another thread just about the boards..
If it turns out these goals are in conflict, then perhaps we can do 2 different boards, but I suspect that we can devise a board that is small, nice looking, and also is easily installed in the amps mentioned in this thread. Thanks to your comment, I realized that the new boards don't have to be the exact size of the old amps boards. It would be nice however if they could be easily mounted to the existing amp hardware, and that's part of the fun- making a board that does all these things well
When we get to the group buy stage, we can create a wiki page and possibly another thread just about the boards..
Sorry guys, I truly didn't mean to perpetrate my first major threadjack!
Variac,
I can address some questions you had.
On my mini-a (in a Hafler chassis) I am using nice small BrianGT boards mounted on a standoff board (that I am using to provide some local capacitance). It has worked out nicely. It is very similar in concept to BrianGT's Hafler to Leach conversion as seen in his gallery. So, I think that small "universal" boards are great.
I started out with to220 packages in the little Aleph, but switched over to to3 (today). To3's are cool.
Oh yeah, I noticed you (Variac) live in SF. If you are interested, I am willing to bring the mini-a up from San Jose for a listen. Same offer is of course extended to NP. I can check with the wife about having company here if you are up for a drive.
regards,
PSz.
Variac,
I can address some questions you had.
On my mini-a (in a Hafler chassis) I am using nice small BrianGT boards mounted on a standoff board (that I am using to provide some local capacitance). It has worked out nicely. It is very similar in concept to BrianGT's Hafler to Leach conversion as seen in his gallery. So, I think that small "universal" boards are great.
I started out with to220 packages in the little Aleph, but switched over to to3 (today). To3's are cool.
Oh yeah, I noticed you (Variac) live in SF. If you are interested, I am willing to bring the mini-a up from San Jose for a listen. Same offer is of course extended to NP. I can check with the wife about having company here if you are up for a drive.
regards,
PSz.
Various items:
--I'm not sure that the Hafler has as much open space as you're thinking. It would be a good idea to go ahead and use their mounting scheme for the PCBs. Besides, with the boards right there at the outputs, you'll be keeping the signal path short.
--The PCBs fasten to the heatsinks with three small screws. While that spacing is fixed, there is sufficient play in the overall scheme of things to increase the board size should that be deemed necessary.
--Use of the existing MOSFETs should not be assumed. After all, to the extent that an amp is dead, it's not unlikely that one or more of the output devices are kaput, and there aren't any more of those devices being made. Yes, there are some available on ebay, but I wouldn't want to base a circuit on NOS solid state parts any more than I would base a tube design on an obsolete, rare tube that is only available at horrendous cost.
--Just because the heatsink is drilled for TO-3 cases doesn't mean that you can't use one of the mounting holes to attach a TO-247. Living in a...shall we say, technically challenged corner of the nation, I frequently need to reuse old heatsinks due to scarcity of big new ones. (Why do you think I went to water cooling for the Aleph 2s? Couldn't source enough heat sink. Necessity is a mother...) Anyway, the point is that other semiconductor case styles are not necessarily ruled out. Don't make Nelson part with his cache of TO-3 parts unless it's absolutely, positively necessary. He makes a living off those things and could very well need them for service of older amps later on.
--An LC filter is a good idea, but it will take a nice balance between current draw and inductance to make it pan out.
--The Achilles heel of the old Haflers was the power switch. They would arc and either weld themselves open or closed. The original switch was--I think--10A. Later parts were 15A and more reliable. New switches are available without having to go the ebay route. I'll try to remember to dredge up the part number when I get home. If my home PC will consent to boot (no guarantees, there) I will try to get that posted later.
--They used .005uF ceramic discs for spark suppression on the power switches. I would suggest .01uF. Again, think reliability.
--I have no experience with the Adcom amps.
--Somebody prompt me to take up this list again later as I've got to move on. There are a dozen little things that need attending to in order to make the thing more reliable. Power supply caps, for instance.
Grey
...Oh, another thing about output devices...some folks will inevitably want to build the circuit from scratch. Don't make them go out and track down old parts.
--I'm not sure that the Hafler has as much open space as you're thinking. It would be a good idea to go ahead and use their mounting scheme for the PCBs. Besides, with the boards right there at the outputs, you'll be keeping the signal path short.
--The PCBs fasten to the heatsinks with three small screws. While that spacing is fixed, there is sufficient play in the overall scheme of things to increase the board size should that be deemed necessary.
--Use of the existing MOSFETs should not be assumed. After all, to the extent that an amp is dead, it's not unlikely that one or more of the output devices are kaput, and there aren't any more of those devices being made. Yes, there are some available on ebay, but I wouldn't want to base a circuit on NOS solid state parts any more than I would base a tube design on an obsolete, rare tube that is only available at horrendous cost.
--Just because the heatsink is drilled for TO-3 cases doesn't mean that you can't use one of the mounting holes to attach a TO-247. Living in a...shall we say, technically challenged corner of the nation, I frequently need to reuse old heatsinks due to scarcity of big new ones. (Why do you think I went to water cooling for the Aleph 2s? Couldn't source enough heat sink. Necessity is a mother...) Anyway, the point is that other semiconductor case styles are not necessarily ruled out. Don't make Nelson part with his cache of TO-3 parts unless it's absolutely, positively necessary. He makes a living off those things and could very well need them for service of older amps later on.
--An LC filter is a good idea, but it will take a nice balance between current draw and inductance to make it pan out.
--The Achilles heel of the old Haflers was the power switch. They would arc and either weld themselves open or closed. The original switch was--I think--10A. Later parts were 15A and more reliable. New switches are available without having to go the ebay route. I'll try to remember to dredge up the part number when I get home. If my home PC will consent to boot (no guarantees, there) I will try to get that posted later.
--They used .005uF ceramic discs for spark suppression on the power switches. I would suggest .01uF. Again, think reliability.
--I have no experience with the Adcom amps.
--Somebody prompt me to take up this list again later as I've got to move on. There are a dozen little things that need attending to in order to make the thing more reliable. Power supply caps, for instance.
Grey
...Oh, another thing about output devices...some folks will inevitably want to build the circuit from scratch. Don't make them go out and track down old parts.
I'm 99% sure they are +- 80v rails on the 555. There is a small single 'front end' board at the inputs. The outputs are mounted on 4 boards right at the sinks. The 555mk2 is very similar. This one is sold so I can't measure anything. The inside of one of these things is vaguely similar to the trunk of a '77 caddy
.Attachments
I wouldn't call it a threadjack- more like a good idea.
I have an idea for using a fan with the things, at least this should work for the Hafler:
Drill (3) 3/8" holes between each of the fins. Use a fence made of a board clamped to a drill press table to get all of the holes of a row aligned horizontally.
So basically you drill a hole through the heatsink between each fin at three diffferent points. Then pressurize the interior with a fan on the top or bottom exterior or interior as would fit( interior is best of course)
Air would first cool the interior, then escape between the fins , cooling them..
A bit of work, but with a drill press shouldn't be too hard.
What about the caps? The 10uF caps i assume we wanna use polyprops and we need to deside which footprint to use. Evox-Rifa and Wima has these with a pitch of 37.5mm. Of course axial type exotic can be used.
The 22000uF cap at the output is also a matter of decision. We can use a snap-in type, then people could choose whatever manufacturer they like as the footprint is the same.
The pitch for the resistors needs to be chosen too. I've been using a 10mm pitch now and when i looked at the datasheets for Vishay/Dale resistors they need a pitch of 12mm.
Any toughts?
/Kari
The 22000uF cap at the output is also a matter of decision. We can use a snap-in type, then people could choose whatever manufacturer they like as the footprint is the same.
The pitch for the resistors needs to be chosen too. I've been using a 10mm pitch now and when i looked at the datasheets for Vishay/Dale resistors they need a pitch of 12mm.
Any toughts?
/Kari
Variac said:
I have both, and I guess I'll open them up and see what we've
got. I'm assuming that we will be able to work it up without too
much trouble.
I don't think the existing devices will do the job, being
complementary. Is there an existing source for TO-3's out there?
It would be nice to use the same holes. If not, I will have to
consider parting with a few.
My hopes for this project is that in a few years when you open up a Hafler or Adcom of these vintages, you will be surprised if it hasn't been converted. OK that's ambitious, but I want to make it really easy and CHEAP to do this conversion. This is why I wanted to keep the transformer, capacitors, bridge, transistors, etc.
OK,
-We need two bridges right? so that's new parts.
- The existing transistors don't work, so we need new ones also.
I believe that we should assume that most people will use the TO 247 case because, even if we discover some TO-3's or Nelson supplies some, future modders might not have this option. We should explain the options.Certainly TO3's would be cool...
-the existing power supply caps will be generally overdue for a change, but mine are original and still seem to work.
Of course many people will upgrade the transformer and other things.
As far as the question about watts output, The original HAfler was 110 per channel. The modded class A will be about 10? nelson?
Anyone with an answer to using the new amp in class AB for output closer to the original? I suspect Nelson will say that Class A is essential for superior sound, but am interested if he thinks that is true.. Maybe a future experiment?
OK,
-We need two bridges right? so that's new parts.
- The existing transistors don't work, so we need new ones also.
I believe that we should assume that most people will use the TO 247 case because, even if we discover some TO-3's or Nelson supplies some, future modders might not have this option. We should explain the options.Certainly TO3's would be cool...
-the existing power supply caps will be generally overdue for a change, but mine are original and still seem to work.
Of course many people will upgrade the transformer and other things.
As far as the question about watts output, The original HAfler was 110 per channel. The modded class A will be about 10? nelson?
Anyone with an answer to using the new amp in class AB for output closer to the original? I suspect Nelson will say that Class A is essential for superior sound, but am interested if he thinks that is true.. Maybe a future experiment?
Variac said:
I agree with Variac in most things-even if I don't have my DH200 anymore to convert-most interesting upgrade , ungrade ,Passade or whatever will be with keeping 2Sj and 2Sk in place,along with xformer . those are most expensive parts and changing anything of mentioned in my oppinion put big question on original idea about passifying Hafler DH200 .
in this verry moment-something like Citation (mosfet complementary version) come to my mind- if necessary with CLC or LC correction in PS
about PCB- with any actual schematic or version or size we end-it's smart to make final PCB exactly same in size and holes as origigi DH200-even if that means that on every side of PCB you have 15mm of empty space
Well, its important to remember that this is supposed to work with Adcom also. One more constraint that makes this a challenge.
I envision a board with say a single hole in one corner, with a second mounting hole at two different distances, the way we do to accomodate different sized capacitors or resistors on a board.
If the Adcom uses one board for both channels, then we can make a big one to fit the Adcom have it scored down the middle to allow it to be broken in two for use in the Hafler. the way Brian GT did his chip amp boards.
Yes, this board is going to be fiendishly clever!! Especially if the Master of Layout Kari does his magic, with input from others...including Nelson..
To sum up:
The transformer, power caps, bridge, case, heatsinks, cord and terminals will be used. Maybe power switch. (EDIT: See post below)
New Output devices: If there is a group parts buy maybe we can get them in the existing TO-3 factor, but TO-247 really wouldn't be a problem...
New Fan (maybe using my method) prob needed in order to get:
20 watts/ch of tasty class A
Now, even though I want this to be easy and cheap, I'll bet a lot of people end up upgrading most of the existing parts once they hear it -they'll want more!!! BUT the cheap approach allows the upgrades to be done over a period of time.....
I envision a board with say a single hole in one corner, with a second mounting hole at two different distances, the way we do to accomodate different sized capacitors or resistors on a board.
If the Adcom uses one board for both channels, then we can make a big one to fit the Adcom have it scored down the middle to allow it to be broken in two for use in the Hafler. the way Brian GT did his chip amp boards.
Yes, this board is going to be fiendishly clever!! Especially if the Master of Layout Kari does his magic, with input from others...including Nelson..
To sum up:
The transformer, power caps, bridge, case, heatsinks, cord and terminals will be used. Maybe power switch. (EDIT: See post below)
New Output devices: If there is a group parts buy maybe we can get them in the existing TO-3 factor, but TO-247 really wouldn't be a problem...
New Fan (maybe using my method) prob needed in order to get:
20 watts/ch of tasty class A
Now, even though I want this to be easy and cheap, I'll bet a lot of people end up upgrading most of the existing parts once they hear it -they'll want more!!! BUT the cheap approach allows the upgrades to be done over a period of time.....
Power switch for Hafler:
Mouser part# 691-LTA201TRB/125N
I believe they are $3.80 ea. but I'm quoting from memory and may be off a bit in one direction or another. At any rate, they're not unreasonably expensive.
It'll save you from having to rework the chassis or contrive some Rube Goldberg oddity to switch the power on and off.
Grey
Mouser part# 691-LTA201TRB/125N
I believe they are $3.80 ea. but I'm quoting from memory and may be off a bit in one direction or another. At any rate, they're not unreasonably expensive.
It'll save you from having to rework the chassis or contrive some Rube Goldberg oddity to switch the power on and off.
Grey
Nelson,
How important is matching the mosfets?
Kari, Can't we use 12 pitch and if you want to use 10 then just bend the leads a bit longer?
I need general input here:
Would using Solen 10 uF be acceptable as a median sized cap pitch?
I know some don't think of them as THAT great, but they seem to be available everywhere. I'll check the price and size, but we need feedback.
EDIT: OK the Solen is 26x38 and costs about $4 ea. in the US. The Rifi and Wima are the same length. How do people feel about that? Maybe someone can check the prices on the ones Kari mentions.
Kari could have various holes for a few different caps as in the BOSOZ. Its possible that there might be interference issues with such a big cap on the board but I think it will be OK as long as we don't use film/foil.
Do all the 10 uf caps have to be poly? or just the ones at the input and output or what?
P.S. PSz of course I want to hear your amp. I will be setting up a listening session in about a month. Maybe you can make it. I'll keep you informed
How important is matching the mosfets?
Kari, Can't we use 12 pitch and if you want to use 10 then just bend the leads a bit longer?
I need general input here:
Would using Solen 10 uF be acceptable as a median sized cap pitch?
I know some don't think of them as THAT great, but they seem to be available everywhere. I'll check the price and size, but we need feedback.
EDIT: OK the Solen is 26x38 and costs about $4 ea. in the US. The Rifi and Wima are the same length. How do people feel about that? Maybe someone can check the prices on the ones Kari mentions.
Kari could have various holes for a few different caps as in the BOSOZ. Its possible that there might be interference issues with such a big cap on the board but I think it will be OK as long as we don't use film/foil.
Do all the 10 uf caps have to be poly? or just the ones at the input and output or what?
P.S. PSz of course I want to hear your amp. I will be setting up a listening session in about a month. Maybe you can make it. I'll keep you informed
Variac said:
Ok by me.
Variac said:
The Evox-Rifa 10uF in sweden is ~5.40USD. Datasheet is here:
Yep, we could have several footprints on the board. We just need to decide which ones. I also think that we don't want to have footprints for like 10 different types, right?Variac said:
Atleast the input and output. Dunno really about the one on the positive supply.Variac said:
/Kari
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