My modded DH-200
Thanks
In fact,
Added:
4 small pcbs added on the Hafler PC-6 pcb (for each channel)
2 voltage regulator pcbs for the front end (one per channel)
2 pcb for switch off thump removal (one per channel)
100uf Electrolytic caps close to mosfets drain (in parrallel with actual 100nf bypass)
Better type Input caps in parralel with existing one.
Added 100nf in parralel with actual electrolytic 470uf feedback cap
0.11 ohms source resistors on mosfets
1 uf Speed-up cap on drive resistor of mosfet
Changes:
4 x 14000 uf (with discharge resistors) from orignal 2 x 10000 uf
2 x 35A diode bridges in place of the original 1 diode bridge
Power Grounding like Musical Concept suggests
msb64 said:
Thanks
In fact,
Added:
4 small pcbs added on the Hafler PC-6 pcb (for each channel)
2 voltage regulator pcbs for the front end (one per channel)
2 pcb for switch off thump removal (one per channel)
100uf Electrolytic caps close to mosfets drain (in parrallel with actual 100nf bypass)
Better type Input caps in parralel with existing one.
Added 100nf in parralel with actual electrolytic 470uf feedback cap
0.11 ohms source resistors on mosfets
1 uf Speed-up cap on drive resistor of mosfet
Changes:
4 x 14000 uf (with discharge resistors) from orignal 2 x 10000 uf
2 x 35A diode bridges in place of the original 1 diode bridge
Power Grounding like Musical Concept suggests
Do you think that dual power supplies are worth trying out?
The Musical Concepts toroids and similar make it fairly easy to setup.
I am thinking of splitting the chassis and sectioning in another few inches for added internal space, for large caps, toroids etc.
It would be fairly easy to do with the correct gauge of sheet metal and a mig. The chassis is simple enough to just bend up another base and top too, but you would have to add on some end tabs for the heat sinks and securing the top.
Just putting together my check list now
The Musical Concepts toroids and similar make it fairly easy to setup.
I am thinking of splitting the chassis and sectioning in another few inches for added internal space, for large caps, toroids etc.
It would be fairly easy to do with the correct gauge of sheet metal and a mig. The chassis is simple enough to just bend up another base and top too, but you would have to add on some end tabs for the heat sinks and securing the top.
Just putting together my check list now
msb64 said:
I can not really tell because I did not make good comparison test by myself at the time. I do no have this amp anymore since I gave it to my friend who likes this amp so much... I do know that he had previously my other modded DH-200 with 2 x 30000 uf single bridge and when he tried this one with 4 x 14000 uf and 2 bridges he said there was more bass.
The original Hafler transfo with single ground tap does not allow to go fully double mono.
Keep us posted on your mod project with some pictures when available.
I will be sure to post some pics when I get something substantial.
It just came to mind that it would be cool to fabricate a heavier aluminum top to help dissipate some of the heat too. I would have to get help on that one though, as I am currently not setup for welding aluminum.
I have to hurry up and get going on these projects, because once the snow starts to melt and the car season approaches, it is hard to find the time to work on the indoor stuff. Winter is definitely the best time for that. Not to mention that funds usually get diverted to the never ending search for more HP too
It just came to mind that it would be cool to fabricate a heavier aluminum top to help dissipate some of the heat too. I would have to get help on that one though, as I am currently not setup for welding aluminum.
I have to hurry up and get going on these projects, because once the snow starts to melt and the car season approaches, it is hard to find the time to work on the indoor stuff. Winter is definitely the best time for that. Not to mention that funds usually get diverted to the never ending search for more HP too
Okay, I'm in.
DH-200s. I guess I'm ready to start working on these. Over the summer I knocked out 3 Ampzilla rebuilds, 2 SonofA rebuilds and I just finished a GFA-555 and a complete rebuild on a Phase Linear 700 II. I feel like working on something more simple now.
I have 2 defective DH-200s that I can basically do whatever with. One just fails to proceed and the other has been modded to death, mostly by the addition of soldering iron burns and the removal of critical insulation. I have a batch of semis on order and I could just restore them to original condition, but I feel like doing something more interesting with them.
One suggestion was monoblocks, incorporating one driver card/chassis. As described, the N-devices would be on one heat sink and the P-devices would be on the other, allowing more output devices, higher bias current & other changes.
I have a question about that scheme. Since the heat sinks are far apart, it would appear to require long leads to the gates of at least one set of outputs. Is this what was intended? Is it safe?
Thx.
DH-200s. I guess I'm ready to start working on these. Over the summer I knocked out 3 Ampzilla rebuilds, 2 SonofA rebuilds and I just finished a GFA-555 and a complete rebuild on a Phase Linear 700 II. I feel like working on something more simple now.
I have 2 defective DH-200s that I can basically do whatever with. One just fails to proceed and the other has been modded to death, mostly by the addition of soldering iron burns and the removal of critical insulation. I have a batch of semis on order and I could just restore them to original condition, but I feel like doing something more interesting with them.
One suggestion was monoblocks, incorporating one driver card/chassis. As described, the N-devices would be on one heat sink and the P-devices would be on the other, allowing more output devices, higher bias current & other changes.
I have a question about that scheme. Since the heat sinks are far apart, it would appear to require long leads to the gates of at least one set of outputs. Is this what was intended? Is it safe?
Thx.
Sorry to Over-reply myself but I can't get Edit to work.
My priority would be improving current delivery into low Z loads. My main speakers for now are Linn Isobarik DMS. They seem to like MOSFETS better than BJTs. The Z goes below 4 ohms in significant places and they're in a very dead 900sf ( ~ 80 m sq) room. Power is needed but not kilowatts. I'm thinking that a lightly modded pair of these Haflers might be just the thing, and would be cheap to do.
Stuff I'll do for sure:
0) replace defective components.
0.5) test and match all xstrs
1) correct the grounding.
2) upgrade all electrolytic capacitors, within reason
3) take a look at the film bypass options & adopt those that seem practical
4) retrofit circuit on input for DC balance.
5) incorporate into my PC-19 boards improvements that were added to later versions.
6) add IEC sockets for power cords ( safety issue. I've badly broken a bone in my foot tripping over a line cord while carrying an amp and I eliminate them whenever I can)
7) new speaker terminals
8) new input jacks
Stuff I'll consider:
0) separate PSU for the driver boards.
1) better rectifier
2) low speed ext. fans
3) relocating speaker fuses inboard
4) upgraded power switches
5) passive inrush current limiter
Stuff I probably won't do:
0) New driver boards
1) Significant circuit topology changes
2) boutique parts
3) relay-type soft start
Not even considering:
0) bridged configuration
1) returning to stock
2) preserve resale value
3) WAF
4) listening to every possible modification and 'voicing' by ear.
My priority would be improving current delivery into low Z loads. My main speakers for now are Linn Isobarik DMS. They seem to like MOSFETS better than BJTs. The Z goes below 4 ohms in significant places and they're in a very dead 900sf ( ~ 80 m sq) room. Power is needed but not kilowatts. I'm thinking that a lightly modded pair of these Haflers might be just the thing, and would be cheap to do.
Stuff I'll do for sure:
0) replace defective components.
0.5) test and match all xstrs
1) correct the grounding.
2) upgrade all electrolytic capacitors, within reason
3) take a look at the film bypass options & adopt those that seem practical
4) retrofit circuit on input for DC balance.
5) incorporate into my PC-19 boards improvements that were added to later versions.
6) add IEC sockets for power cords ( safety issue. I've badly broken a bone in my foot tripping over a line cord while carrying an amp and I eliminate them whenever I can)
7) new speaker terminals
8) new input jacks
Stuff I'll consider:
0) separate PSU for the driver boards.
1) better rectifier
2) low speed ext. fans
3) relocating speaker fuses inboard
4) upgraded power switches
5) passive inrush current limiter
Stuff I probably won't do:
0) New driver boards
1) Significant circuit topology changes
2) boutique parts
3) relay-type soft start
Not even considering:
0) bridged configuration
1) returning to stock
2) preserve resale value
3) WAF
4) listening to every possible modification and 'voicing' by ear.
Practicality of separating N and P MOSFETS to opposite ends of chassis
So my question would be if a DH-200 was converted to a mono amp as described in an earlier post, with a single driver card would it be practical to separate the P and N MOSFETS to opposite heat sinks, distributing the heat equally?
The problem it seems to me would be long leads to the Gates of one or both sets of outputs. Possible issues:
1) lead inductance
2) stray signal pickup.
Are these significant considerations?
So my question would be if a DH-200 was converted to a mono amp as described in an earlier post, with a single driver card would it be practical to separate the P and N MOSFETS to opposite heat sinks, distributing the heat equally?
The problem it seems to me would be long leads to the Gates of one or both sets of outputs. Possible issues:
1) lead inductance
2) stray signal pickup.
Are these significant considerations?
Re: comments
Thanks for your reply. I suppose matching should take care of the DC offset initially. I noticed that later versions of the PC19 board incorporated a DC offset adjustment pot. This leads me to believe that there might be a need for it due to heat, aging, etc.
One way to avoid having long gate leads on one side would be to place the one driver board centrally. This would require moving the rectifier and filter caps out of the way. I can do that because I have some very small 15,000uf @ 80VDC caps that I plan to use.
I'll have to do some measuring, but I think the leads to the gates could be gotten down to under 5" on both sides.
I'd like to use both heat sinks so I can drive a total of 6 MOSFETS and have plenty of cooling.
I'll get one of the DH-200 chassis on the bench today. My order from Mouser came today, including most of the semis for this project.
Right now the bench is occupied again by an Ampzilla Ib that has already spent too much time there. I'm tired of fooling with its meter illumination circuits to keep them working so I ripped it all out and installed LEDs behind the meters, with a dedicated power supply. That'll fix it once and for all.
pidigi said:
Thanks for your reply. I suppose matching should take care of the DC offset initially. I noticed that later versions of the PC19 board incorporated a DC offset adjustment pot. This leads me to believe that there might be a need for it due to heat, aging, etc.
One way to avoid having long gate leads on one side would be to place the one driver board centrally. This would require moving the rectifier and filter caps out of the way. I can do that because I have some very small 15,000uf @ 80VDC caps that I plan to use.
I'll have to do some measuring, but I think the leads to the gates could be gotten down to under 5" on both sides.
I'd like to use both heat sinks so I can drive a total of 6 MOSFETS and have plenty of cooling.
I'll get one of the DH-200 chassis on the bench today. My order from Mouser came today, including most of the semis for this project.
Right now the bench is occupied again by an Ampzilla Ib that has already spent too much time there. I'm tired of fooling with its meter illumination circuits to keep them working so I ripped it all out and installed LEDs behind the meters, with a dedicated power supply. That'll fix it once and for all.
Re: Re: comments
Let us know about the results,
Ciao
Paolo
Transistor matching also takes care of some distortion in the input stage. The balancing circuit will hide this problem.BAUHAUSLER said:
Mosfets are high input impedance devices, as you already know. I don't see very well this long gate connections.
I've put 6 mosfets (obviuosly matched) directly soldered on the PCB, not the 2SJ49/2SK134 but their TO3P equivalent 2SJ162/2SK1058, and I'm planning to use a board on every heatsink. You said that you are going to install external low speed fans anyhow, so I wouldn't care about temperature rise.
Let us know about the results,
Ciao
Paolo
Re: Re: Re: comments
I see. So if I understand you correctly:
1) keep all outputs on one heat sink so that Gate leads stay short
2) use a fan if necessary to shed heat
3) use matched input transistors to achieve DC balance and reduce distortion.
Sounds like a good plan. I also have the TO3P outputs on order so fitting 6 of them them on the heatsink will just require a little drilling and tapping.
I got my 3440 and 5415 transistors from Mouser yesterday. I ordered 15 of each, specifying units from ST. A quick check of them on an HFE meter showed nearly all are 63 +/- 3 for both the NPNs and PNPs with 2 or 3 outliers around 70. This is exceptionally close for a batch of randomly chosen devices.
That reminds me I need to hunt some nice heat sinks for them.
The project is on hold pending delivery of more parts...
pidigi said:
I see. So if I understand you correctly:
1) keep all outputs on one heat sink so that Gate leads stay short
2) use a fan if necessary to shed heat
3) use matched input transistors to achieve DC balance and reduce distortion.
Sounds like a good plan. I also have the TO3P outputs on order so fitting 6 of them them on the heatsink will just require a little drilling and tapping.
I got my 3440 and 5415 transistors from Mouser yesterday. I ordered 15 of each, specifying units from ST. A quick check of them on an HFE meter showed nearly all are 63 +/- 3 for both the NPNs and PNPs with 2 or 3 outliers around 70. This is exceptionally close for a batch of randomly chosen devices.
That reminds me I need to hunt some nice heat sinks for them.
The project is on hold pending delivery of more parts...
Hafler DH200 update and some other related material here that may be of interest to some.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1701561#post1701561
http://www.diyaudio.com/forums/showthread.php?s=&postid=1701561#post1701561
Dick West said:
Okay. That's better. Some kinda backwards-typing keyboard gremlin.
I don't know yet. I downloaded some circuits for simple testers to match power MOSFETS. I assume I'll just mod one of the rigs that I use to match power BJTs and it will be like that except less thermal drift hassles. I'll lash something up when the MOSFETS arrive and start fooling around. I ordered the Renesas 1058 and 162 devices.
I've read through this thread from the beginning through about page 18, skimming the parts about 'why does my fuse blow' and similar. I'm yanking out relevant chunks into a Word doc so I can take a hilighter to it later.
I'm intrigued by the schemes for regulating the supplies to the 'board'. There seems to be a lot to be gained from a very little bit of circuitry. Since my application - driving low Z speakers - will cause a lot of signal-correlated main supply droop I think regulated board supplies belong in my bag of tricks. Since I won't be using all of the amp's available voltage swing I'll first experiment with regulating the raw rails to the boards.
If experiments show that the available drive signal is compromised by having only +/- 50V or so on the driver boards, then I'll go with an enhanced supply scheme, bucking the raw AC up with a 12VAC winding on each end, rectifying and regulating down the resulting higher voltage. Gotta try the easy way first.
BAUHAUSLER said:
I had 2 modded DH-200 with regulated 52 volts for the front end supply with no problem at all even at amp saturation which gives about 110Wrms(8 ohms) instead of 130Wrms for the original 60 Volts supply. With low Z speaker the DH-200 will saturate because of current starving and not because of voltage...
Good luck
fab said:
That's exactly what I needed to know. I dug up the carton of 12v transformers just in case but I guess I won't need them. Simple is better as long as it achieves the goal
Later this week I'll take a couple of my heat sinks and modify them for best placement of the TO3P outputs. This just involves planning out best placement, milling the areas flat on a Bridgeport and drilling and tapping mounting holes. Tedious and messy but probably necessary when mounting 6 devices where there were 4. While I'm there I might as well mill out some nice blanking panels for the end of the chassis where I'm removing one heat sink.
It's my understanding that large values of PSU capacitance primarily benefits the driver board, and that regulating the driver supplies eliminates the need to beef up the PSU caps. I'm prepared to increase the caps if it will make a difference, but will it be worthwhile after the driver regs are added?
Another question: How much current per rail does one driver board draw? I haven't got a running one to measure.
Some 15-18 years ago there was an Audio Amateur article in which the author described how he regulated his DH-220 front ends. He used a Triad transformer that supplied ±85VDC which was then regulated down to around 65 VDC using an LM371. The controlling terminal was floating in a stack of zeners. Pretty straight forward circuit with 460mF cap on one side and around 1000 uF cap on the other. The entire thing was black boxed outboard with an umbilical to feed the PCBs inside the case.
It is instructive to note that the XL-280 has booster windings on its transformer to supply the PCBs with ~70 VDC. The extra voltage to the PCBs provides a few more watts of power. However I should I imagine that using a separate transformer for the PCB power supply would better decouple it from output power variations caused by heavy musical transients.
I match my MOSFETs using an original Hafler MOSFET checker. If you pay postage both ways I will match your devices for you and grade them 1 through 7, just as in the Hafler amps.
It is instructive to note that the XL-280 has booster windings on its transformer to supply the PCBs with ~70 VDC. The extra voltage to the PCBs provides a few more watts of power. However I should I imagine that using a separate transformer for the PCB power supply would better decouple it from output power variations caused by heavy musical transients.
I match my MOSFETs using an original Hafler MOSFET checker. If you pay postage both ways I will match your devices for you and grade them 1 through 7, just as in the Hafler amps.
