Car engine likeness...
It is funny you said that, several friends have said the same thing...
In simplifying the layout and wiring, re-positioned the binding posts,
which look like dual AMG exhausts.
[for me]
As a car buff, the car analogies fit... I see and think the same things.
Attached image, is an older build, of my first modified DH500,
for perspective...
~ BIG BLOCKS FOR SURE ~
It is funny you said that, several friends have said the same thing...
In simplifying the layout and wiring, re-positioned the binding posts,
which look like dual AMG exhausts.
[for me]
As a car buff, the car analogies fit... I see and think the same things.
Attached image, is an older build, of my first modified DH500,
for perspective...
~ BIG BLOCKS FOR SURE ~
Attachments
Last edited:
How I spend my time in retirement...
That is for sure. I struggle saying, I enjoy building as much or maybe even more than simply listening.
Those are 1000va toroids. The "conventional" reworked Hafler 500 / 600 are dual stacked 625va., (same value as single stock iron core transformer) are the largest which will fit inside the chassis. I wanted to 'double' that size.
A couple of amp builds down the road, I will try / build with 2 of the "smaller" 625va toroids, but wanted to try the Mundorf MLytic HC first.
That is for sure. I struggle saying, I enjoy building as much or maybe even more than simply listening.
Those are 1000va toroids. The "conventional" reworked Hafler 500 / 600 are dual stacked 625va., (same value as single stock iron core transformer) are the largest which will fit inside the chassis. I wanted to 'double' that size.
A couple of amp builds down the road, I will try / build with 2 of the "smaller" 625va toroids, but wanted to try the Mundorf MLytic HC first.
@Ozark HiFi Doctor-
Your MONDO PS’s are crazy large with 1000va toroidals and 156,000uf (4x39k) per side. That’s 312,000uf total capacitance. How do you start those puppies up without throwing the breaker or causing some serious dimming in the neighborhood?
I agree with you about the power supply being the heart of an amp. I recently replaced the two 39,000uf power capacitors in my DH500 with a Musical Concepts PS500 board with 8 Mundorf 15,000uf M-Lytic AG caps increasing the total power capacitance from 78,000uf to 120,000uf. The board is dual mono and CRC topology and specifically designed for the DH500 so fits like a glove in the chassis. Nice improvement in the bass and dynamics. I had installed a diyAudio soft start board a while back that limits the large inrush current. I still have the original Hafler 675va transformer. My next mod will probably be changing that out with two 600va Toroidy transformers which will give me true dual mono PS.
I wanted to ask you about the Exicon MOSFETs. How much improvement, if any, is there changing out the original Hitachi MOSFETs that are working fine to the Exicons?
Your MONDO PS’s are crazy large with 1000va toroidals and 156,000uf (4x39k) per side. That’s 312,000uf total capacitance. How do you start those puppies up without throwing the breaker or causing some serious dimming in the neighborhood?
I agree with you about the power supply being the heart of an amp. I recently replaced the two 39,000uf power capacitors in my DH500 with a Musical Concepts PS500 board with 8 Mundorf 15,000uf M-Lytic AG caps increasing the total power capacitance from 78,000uf to 120,000uf. The board is dual mono and CRC topology and specifically designed for the DH500 so fits like a glove in the chassis. Nice improvement in the bass and dynamics. I had installed a diyAudio soft start board a while back that limits the large inrush current. I still have the original Hafler 675va transformer. My next mod will probably be changing that out with two 600va Toroidy transformers which will give me true dual mono PS.
I wanted to ask you about the Exicon MOSFETs. How much improvement, if any, is there changing out the original Hitachi MOSFETs that are working fine to the Exicons?
Proof of concept / test chassis(s)
At this point these are more concept amp / power supplies, overbuilt beyond "conventional" modifications... to see if the bigger supplies were even warranted [it is] I essentially wanted to 'use all of the same parts' to keep consistent in my escalating comparisons. I have had considerable conversations in P/S development with John Hillig, he is aware of and honestly influencing ...contributing greatly... related to my builds. Fankly, I am working (sharing with him) aspects of things outside of his direct product offerings, which [understandably] must all reside inside the chassis.
**In the spirit of transparency, I have known John for nearly 40 years, consider him a personal friend. I owe him a great deal, as mentor over many years, 10s of thousands of dollars spent with him. He has been immensely supportive to my unending pursuit of refinement.
Another aspect that is important to me, is keeping things simple, uncluttered. I wanted a very clean chassis in the wiring and layout. At present, I am using 2 thermistors on the primaries (as shown) I am considering a timer based soft start down the road... but for now am focusing all budget and build attention to that which make an audible difference ~ and ~ for now [continuity] keeping all things the same across multiple chassis being built and tested. To eliminate variables, all chassis are using the exact same parts, built the same, even down to the wire.
Quite frankly, in a couple of months of use, these MONDO CLC have only been power cycled 3 or 4 times... That said, when I do power these up, I get a slight dimming of my lights and a 2 volt line drop on my AC, while in use... (I live in a country farm house, loose electrical codes and questionable wiring) At present, I have not got them on dedicated AC circuits (in time, another project) I am thinking about dedicated 240v 30 amp / drop(s) for my amps. I am making do
will admit to struggles, tearing into sheet rock. My music room is right above my AC panel, 10 feet from the AC drop... an awesome thing.
For Note: I do have a Musical Concepts PS500 and the 8 Mundorfs, like you. I just have not gotten around to building then into (one of) the empty 500 chassis, that I have been using on the CLC, but that is my long term plan. (in time). I am pleased to hear that you like this set-up ~ I "expect" the same ~
I have nearly 150 of the Exicon MOSFETS (TO3, TO247 and TO264) I AM SUPER IMPRESSED WITH THE EXICONS!!! It is the next level in refinement. I would like to put them in all 11 Hafler amps that I own, but am reserving them for my own amp design and builds. I am beginning to believe that (like with vacuum tubes) 30-40 year old vintage Hitachi MOSFETS are showing their age, questioning that "their tolerances" are slipping. *A whole other topic for another thread.
YOU ARE IN FOR A HUGE SURPRISE GOING DUAL MONO!!! (image 2) is the first DH 500, I modified in 2012... I only listened to - tested it it for 6 hours before tearing it apart. It was a big disappointment. (Image 3) was the eventual path. (Image 4) like everything, I am building in multiples and doing close comparisons along the way. Stock supply is ~ grossly lacking ~ unable to render the true capabilities of the DH500 power module.
At this point these are more concept amp / power supplies, overbuilt beyond "conventional" modifications... to see if the bigger supplies were even warranted [it is] I essentially wanted to 'use all of the same parts' to keep consistent in my escalating comparisons. I have had considerable conversations in P/S development with John Hillig, he is aware of and honestly influencing ...contributing greatly... related to my builds. Fankly, I am working (sharing with him) aspects of things outside of his direct product offerings, which [understandably] must all reside inside the chassis.
**In the spirit of transparency, I have known John for nearly 40 years, consider him a personal friend. I owe him a great deal, as mentor over many years, 10s of thousands of dollars spent with him. He has been immensely supportive to my unending pursuit of refinement.
Another aspect that is important to me, is keeping things simple, uncluttered. I wanted a very clean chassis in the wiring and layout. At present, I am using 2 thermistors on the primaries (as shown) I am considering a timer based soft start down the road... but for now am focusing all budget and build attention to that which make an audible difference ~ and ~ for now [continuity] keeping all things the same across multiple chassis being built and tested. To eliminate variables, all chassis are using the exact same parts, built the same, even down to the wire.
Quite frankly, in a couple of months of use, these MONDO CLC have only been power cycled 3 or 4 times... That said, when I do power these up, I get a slight dimming of my lights and a 2 volt line drop on my AC, while in use... (I live in a country farm house, loose electrical codes and questionable wiring) At present, I have not got them on dedicated AC circuits (in time, another project) I am thinking about dedicated 240v 30 amp / drop(s) for my amps. I am making do
will admit to struggles, tearing into sheet rock. My music room is right above my AC panel, 10 feet from the AC drop... an awesome thing.For Note: I do have a Musical Concepts PS500 and the 8 Mundorfs, like you. I just have not gotten around to building then into (one of) the empty 500 chassis, that I have been using on the CLC, but that is my long term plan. (in time). I am pleased to hear that you like this set-up ~ I "expect" the same ~
I have nearly 150 of the Exicon MOSFETS (TO3, TO247 and TO264) I AM SUPER IMPRESSED WITH THE EXICONS!!! It is the next level in refinement. I would like to put them in all 11 Hafler amps that I own, but am reserving them for my own amp design and builds. I am beginning to believe that (like with vacuum tubes) 30-40 year old vintage Hitachi MOSFETS are showing their age, questioning that "their tolerances" are slipping. *A whole other topic for another thread.
YOU ARE IN FOR A HUGE SURPRISE GOING DUAL MONO!!! (image 2) is the first DH 500, I modified in 2012... I only listened to - tested it it for 6 hours before tearing it apart. It was a big disappointment. (Image 3) was the eventual path. (Image 4) like everything, I am building in multiples and doing close comparisons along the way. Stock supply is ~ grossly lacking ~ unable to render the true capabilities of the DH500 power module.
Attachments
I wanted to try the dual mono with my DH-500 a while back, as I had acquired an extra Hafler transformer for that. Never got to it and wasn’t looking forward to the idea of the packaging required to fit it into the original chassis.
It is surprising how these amps respond to power supply mods.
The original transformers make for great line isolation when configured back to back however, if you wind up with an extra pair.
It is surprising how these amps respond to power supply mods.
The original transformers make for great line isolation when configured back to back however, if you wind up with an extra pair.
@Ozark HiFi Doctor-
Thanks for the info on the Exicon MOSFETs. I’m convinced to give them a try. From the Profusion site, it seems the ECF10N20 / ECF10P20 are the direct replacements for the Hitachi MOSFETs. What is the advantages of the double die ECF20N20 / ECF20P20 considering the heat dissipation limitations with the DH500 heat sink power module? The bias current cannot be set any higher than say 400ma without the fan cycling on high speed. Is that enough bias to take advantage of the higher power output of the double die MOSFETs?
Yes, I too have known John Hillig for almost 40 years (not as a friend but a customer). I purchased my first Musical Concepts Hafler upgrade kit in 1981 when I modified my first DH500 that I built from kit. I sold that in the mid 80’s and downsized to a DH220. That I modified with all the Musical Concepts stuff including converting to dual mono PS. That was in the days (way before the MC PAxx boards) where MC upgraded the Hafler PC19 boards. I also built a preamp in the mid 80s from the Musical Concepts MC1 board. They still offer that board today although it is now the MC3 version.
I took a hiatus from audio electronics for 20 years to raise a family. Now that the kids are grown and off on their own, I have more free time and slowly getting back into audio. I remember the muscle of my first DH500 so I purchased another one a couple years ago which I’ve been upgrading. Instead of purchasing the Musical Concepts PA6 or PA7 boards, I’ve built the Cordell DH220C boards which I’m using in the DH500 and very pleased. BYI, I still have the MC1 preamp board which I’ve recapped and use as a phono stage.
Thanks for the info on the Exicon MOSFETs. I’m convinced to give them a try. From the Profusion site, it seems the ECF10N20 / ECF10P20 are the direct replacements for the Hitachi MOSFETs. What is the advantages of the double die ECF20N20 / ECF20P20 considering the heat dissipation limitations with the DH500 heat sink power module? The bias current cannot be set any higher than say 400ma without the fan cycling on high speed. Is that enough bias to take advantage of the higher power output of the double die MOSFETs?
Yes, I too have known John Hillig for almost 40 years (not as a friend but a customer). I purchased my first Musical Concepts Hafler upgrade kit in 1981 when I modified my first DH500 that I built from kit. I sold that in the mid 80’s and downsized to a DH220. That I modified with all the Musical Concepts stuff including converting to dual mono PS. That was in the days (way before the MC PAxx boards) where MC upgraded the Hafler PC19 boards. I also built a preamp in the mid 80s from the Musical Concepts MC1 board. They still offer that board today although it is now the MC3 version.
I took a hiatus from audio electronics for 20 years to raise a family. Now that the kids are grown and off on their own, I have more free time and slowly getting back into audio. I remember the muscle of my first DH500 so I purchased another one a couple years ago which I’ve been upgrading. Instead of purchasing the Musical Concepts PA6 or PA7 boards, I’ve built the Cordell DH220C boards which I’m using in the DH500 and very pleased. BYI, I still have the MC1 preamp board which I’ve recapped and use as a phono stage.
Vintage Musical Concepts
Think of it more that ECF10N20 / ECF10P20 (lower voltage) 200 series amp parts and the ECF20N20 / ECF20P20 are the (higher voltage) 500/600 series parts. I have written Profusion several times, asking what is the ideal B+ range is for either part. They never responded (life in CV1984 era) most customer service sucks...
I have been seeing my 500/600 amps "parked on" the high fan speed, they rarely "see' the low speed, even at idle. I have biased the Exicons the same as the Hitachi's, (550-600ma) and I am happy. They sound fine.
I am using (only one) 300 ohm resistor in series and jumper around it in heavy listening. Two of my 500s have stuck temperature switches, stuck on high and one is stuck on low. **In the future, I am going to mount a switch to jumper around the resister
I did many Musical Concepts PC19 (board level) mods for customers, before the MC PCxxx board offerings (image as shown). I took my ~1986 built 220 amp compared it to my old Mark Levinson No. 336, before I sold it. The MC220 held its own, it was very impressive.
As you mention it ...sitting in a box... I still have a Musical Concepts MC1 Teflon, with Teflon PCB and coupling caps. I need to re-cap it, but am concerned about lifting traces, that may "not want to stick" in the process. I compared it to my roommates ARC SP10 and an SP11 (in the day) it held its own... was much quieter.
Think of it more that ECF10N20 / ECF10P20 (lower voltage) 200 series amp parts and the ECF20N20 / ECF20P20 are the (higher voltage) 500/600 series parts. I have written Profusion several times, asking what is the ideal B+ range is for either part. They never responded (life in CV1984 era) most customer service sucks...
I have been seeing my 500/600 amps "parked on" the high fan speed, they rarely "see' the low speed, even at idle. I have biased the Exicons the same as the Hitachi's, (550-600ma) and I am happy. They sound fine.
I am using (only one) 300 ohm resistor in series and jumper around it in heavy listening. Two of my 500s have stuck temperature switches, stuck on high and one is stuck on low. **In the future, I am going to mount a switch to jumper around the resister
I did many Musical Concepts PC19 (board level) mods for customers, before the MC PCxxx board offerings (image as shown). I took my ~1986 built 220 amp compared it to my old Mark Levinson No. 336, before I sold it. The MC220 held its own, it was very impressive.
As you mention it ...sitting in a box... I still have a Musical Concepts MC1 Teflon, with Teflon PCB and coupling caps. I need to re-cap it, but am concerned about lifting traces, that may "not want to stick" in the process. I compared it to my roommates ARC SP10 and an SP11 (in the day) it held its own... was much quieter.
Attachments
Agreed!
I have compared these Hafler based amps to all kinds of amps, and yes it is amazing how well they respond to power supply refinements.
I have compared these Hafler based amps to all kinds of amps, and yes it is amazing how well they respond to power supply refinements.
@Ozark HiFi Doctor-
Just for clarity, the specs show both the ECF10N20 / ECF10P20 and double die ECF20N20 / ECF20P20 are rated for the same 200V (+/- 100V). So, the ECF10N20 / ECF10P20 are good to use in the DH500 with the 90V rail voltage. Using the double die Exicon’s are enticing but I’m still concerned with the limited bias current in the DH500. It’s stated in Bob Cordell’s book (section 14.10) that each MOSFET output pair is biased at 200mA for low crossover distortion. It’s also stated in Bob’s DH220C design document that this healthy 200mA bias, beside reducing crossover distortion, extends the “class-A” region. With three output pairs per side for the DH500, that results in a targeted bias of 600mA. That’s already a challenge in the DH500 and as you mentioned requires the higher fan speed. Using double die Exicon’s equates to 6 output pairs per side and doubles the bias current to 1200mA which is not achievable in the DH500. Hopefully Bob can weigh in on this and discuss the impact on crossover distortion and performance at the lower bias. Thanks.
Just for clarity, the specs show both the ECF10N20 / ECF10P20 and double die ECF20N20 / ECF20P20 are rated for the same 200V (+/- 100V). So, the ECF10N20 / ECF10P20 are good to use in the DH500 with the 90V rail voltage. Using the double die Exicon’s are enticing but I’m still concerned with the limited bias current in the DH500. It’s stated in Bob Cordell’s book (section 14.10) that each MOSFET output pair is biased at 200mA for low crossover distortion. It’s also stated in Bob’s DH220C design document that this healthy 200mA bias, beside reducing crossover distortion, extends the “class-A” region. With three output pairs per side for the DH500, that results in a targeted bias of 600mA. That’s already a challenge in the DH500 and as you mentioned requires the higher fan speed. Using double die Exicon’s equates to 6 output pairs per side and doubles the bias current to 1200mA which is not achievable in the DH500. Hopefully Bob can weigh in on this and discuss the impact on crossover distortion and performance at the lower bias. Thanks.
@Felixx-
From your earlier posts, you’re using a standard heat sink (not a Hafler DH500). You will need to make sure your heat sink is sized generously to dissipate the heat from running that high a bias. The other issue is the OPS board and if it can reliably handle the higher current to support the double die MOSFETs. Maybe Rick S. can comment on that. You and danieljw have similar configurations (3 pair of double die Exicons per side) per the earlier posts. Danieljw mentioned in Post 36 that he is only running 400mA bias. I don’t know why he is targeting such low bias (that works out to only 67mA per pair…400/6 pair). Possibly danieljw is limited on heat dissipation with the size heat sink being used.
From your earlier posts, you’re using a standard heat sink (not a Hafler DH500). You will need to make sure your heat sink is sized generously to dissipate the heat from running that high a bias. The other issue is the OPS board and if it can reliably handle the higher current to support the double die MOSFETs. Maybe Rick S. can comment on that. You and danieljw have similar configurations (3 pair of double die Exicons per side) per the earlier posts. Danieljw mentioned in Post 36 that he is only running 400mA bias. I don’t know why he is targeting such low bias (that works out to only 67mA per pair…400/6 pair). Possibly danieljw is limited on heat dissipation with the size heat sink being used.
Hi Guys,
I have bumped the bias to 600mA now (200mA per pair) that I know everything is working properly.
With three pairs I achieved approximately 500W into 8 Ohm and approximately 794W into 4 Ohm.
In regards to the temperature I have a 350 x 150 x 50 mm heatsink and it is warm to hot when idling. Under full power sine it becomes too hot to touch for more than a second. This is just a test heatsink.
If you plan to use this amp at these sorts of powers longer term the 0.1 OHm 5 watt (bias measurement shunt resistor) may need to be 10W or 15W to cope.
Hope this helps.
-Dan
I have bumped the bias to 600mA now (200mA per pair) that I know everything is working properly.
With three pairs I achieved approximately 500W into 8 Ohm and approximately 794W into 4 Ohm.
In regards to the temperature I have a 350 x 150 x 50 mm heatsink and it is warm to hot when idling. Under full power sine it becomes too hot to touch for more than a second. This is just a test heatsink.
If you plan to use this amp at these sorts of powers longer term the 0.1 OHm 5 watt (bias measurement shunt resistor) may need to be 10W or 15W to cope.
Hope this helps.
-Dan
Hi Mark. Mike (aka - Ozark Hifi Doctor) has a number of posts in the Hafler DH-200/220 Mods thread where he has covered the good results of using the Musical Concepts PA7 boards in various Hafler amps. Another option to consider is the Bob Cordell DH220C boards in your Hafler DH500. I’ve had good results using the DH220C boards in my DH500 (see my post earlier in this thread). It’s more work since you populate the boards yourself but at roughly half the cost of the MC PA7 boards. Thanks, Bill.
I am familiar with these PA7 boards
If you like the PA3? you will "relate to" the consistent family sound.
I still own 2 pairs of PA4 boards [used the past 8-9 years]
PA7 started my most recent amp building frenzy... lols.
I own 6 pairs of PA7 boards, have used them on 220, 230, 280, 500 and 600 [output stages] with my own beefy power supplies. The circuit is .s.o.l.i.d., very stable in all amp configurations... it also drives the dual die Exicons very well, seamlessly.
In the current builds... these MC PA7/MOSFET based amps GET OUT OF THE WAY OF THE MUSIC, it seems more of a matter of ...what they are not doing... than "what they are doing", they are so neutral.
*Recently re-worked XL600 / with PA7 driver cards, in the foreground.
Exicon equipped 500 heat sink, driven by PA7 boards
and mono CLC power supplies (for testing)
I LOVE the PA7 driving BIG output stages (the 500-600 series)
such musical richness and delicacy ~ small amp character ~
power, slam and effortless ease ~ big amp endless drive ~
Best Mike,
in the
Ozarks
If you like the PA3? you will "relate to" the consistent family sound.
I still own 2 pairs of PA4 boards [used the past 8-9 years]
PA7 started my most recent amp building frenzy... lols.
I own 6 pairs of PA7 boards, have used them on 220, 230, 280, 500 and 600 [output stages] with my own beefy power supplies. The circuit is .s.o.l.i.d., very stable in all amp configurations... it also drives the dual die Exicons very well, seamlessly.
In the current builds... these MC PA7/MOSFET based amps GET OUT OF THE WAY OF THE MUSIC, it seems more of a matter of ...what they are not doing... than "what they are doing", they are so neutral.
*Recently re-worked XL600 / with PA7 driver cards, in the foreground.
Exicon equipped 500 heat sink, driven by PA7 boards
and mono CLC power supplies (for testing)
I LOVE the PA7 driving BIG output stages (the 500-600 series)
such musical richness and delicacy ~ small amp character ~
power, slam and effortless ease ~ big amp endless drive ~
Best Mike,
in the
Ozarks
Attachments
Bob Cordell DH220C boards
Thanks for mentions of cost structure... I have wondered.
I do hope to "get around to" building / hearing DH220C
...one day... in one of my amps...
**I "still have" (4) ICEpower 500A modules
and a set of (2) Hypex UCD400wHRX
to try in my CLC power supplies...
"too many" projects / ideas of
long term study / interest.
Thanks for mentions of cost structure... I have wondered.
I do hope to "get around to" building / hearing DH220C
...one day... in one of my amps...
**I "still have" (4) ICEpower 500A modules
and a set of (2) Hypex UCD400wHRX
to try in my CLC power supplies...
"too many" projects / ideas of
long term study / interest.