just curious if any of you hafler owners saw bob cordell's talk on hafler mods from BA2016 (available on youtube)?
Any thoughts or are any of you working on it in your secret labs?
mlloyd1
I could not find this info...
Any more clues....
Fab
searched at youtube for bob cordell burning amp 2016:
https://www.youtube.com/watch?v=V7-27fDgqco&t=1300s
mlloyd1
https://www.youtube.com/watch?v=V7-27fDgqco&t=1300s
mlloyd1
Bob Cordell ba2016
The design presented by Mr. Cordell reminds me of Borbely jfet differential complementary input stage in his latest amplifiers. No surprise here to use this topology in this amp chassis since Erno Borbely is the designer of the DH-200...
Although the magic here appears to be the use of perfectly matched jfet.
However, according to datsheet the IDss of the dual jfet device seems to have a wide spread....which means operation point that could vary a lot for the jfet input....
400ma bias is probably the maximum you can get from the dh200 heatsink to not exceed 50 deg C....
I wonder if someone will layout a pcb according to this Cordell presented design..
Fab
The design presented by Mr. Cordell reminds me of Borbely jfet differential complementary input stage in his latest amplifiers. No surprise here to use this topology in this amp chassis since Erno Borbely is the designer of the DH-200...
Although the magic here appears to be the use of perfectly matched jfet.
However, according to datsheet the IDss of the dual jfet device seems to have a wide spread....which means operation point that could vary a lot for the jfet input....
400ma bias is probably the maximum you can get from the dh200 heatsink to not exceed 50 deg C....
I wonder if someone will layout a pcb according to this Cordell presented design..
Fab
In Mr. Cordel's talk he mentioned the importance of that large cap in the front end. He also disused using a non polar electrolytic there. I did this once in a Pass A40 but I made it from 2 regular electrolytics connected back to back and then applied a small biasing voltage to the center this redused distortion even more.
Has anyone measured the thermal resistance of the Dh200 heatsinks ?
Has anyone measured the thermal resistance of the Dh200 heatsinks ?
In the 2003 test report done by C.Bateman? he reported that back to back polarised electrolytic produced quite low distortion of the signal when used as a filter for that frequency.
He further reported that biasing the junction between the capacitors made the distortion higher, when used as a filter.
He also reported that using back to back bi-polar electrolytics (without bias to midpoint) produced less distortion than the unbiased back to back polarised electrolytics when both were used as filters.
But, to measure any distortions the author had to use these capacitors as filters. The signal across the capacitor had to be made large to enable distortion to be measured !
In our AC coupling/DC blocking use of capacitors the capacitor value is chosen so that all the audio signal is passing and the filtering effect only occurs at many octaves below the wanted passband.
In this non filtering situation there is no measurable harmonic distortion from the electrolytic AC coupling capacitors. Because there is no signal voltage across the capacitor and thus no signal to distort.
However, there are reports that other parameters of capacitors may add some form of unwanted audio. Some have pointed to D.A. and/or D.F. as a likely culprit.
https://en.wikipedia.org/wiki/Dielectric_absorption
https://en.wikipedia.org/wiki/Dissipation_factor
Hafler DH-220 Mod Kits from Musical Concepts
Hi there!
I built a DH-220 from a kit (way) back in January 1983; and a Hafler DH-110 kit in December 1983. Both the amplifier and pre-amp still seem to work OK, but (following retirement) I've wondered if it is worth 'upgrading' them; for example by installing one of the kits that can be purchased (or installed) from the "Musical Concepts" company; or whether there are other reasonable modifications that I could install to improve sonic performance. Or is it better to just 'recycle' the Hafler kits and purchase a new amplifier and pre-amp?
Any comments/suggestions would be appreciated.
RSVP,
David Plummer
bellevue, WA
Hi there!
I built a DH-220 from a kit (way) back in January 1983; and a Hafler DH-110 kit in December 1983. Both the amplifier and pre-amp still seem to work OK, but (following retirement) I've wondered if it is worth 'upgrading' them; for example by installing one of the kits that can be purchased (or installed) from the "Musical Concepts" company; or whether there are other reasonable modifications that I could install to improve sonic performance. Or is it better to just 'recycle' the Hafler kits and purchase a new amplifier and pre-amp?
Any comments/suggestions would be appreciated.
RSVP,
David Plummer
bellevue, WA
I use polypropylene input cap instead of electrolytic ones.
I have not calculated the thermal resistance of the heatsink but I know by trials that to not exceed 50c when ambient is about 20c then limit dissipation to about 50w max.
Getting back to use new dual jfets from linear systems from Mr Cordell suggestion , has somenie been able to get them and how... from the site it seems to suggest that you need to represent a company and request a quote to know the price and no clue on availability....
Fab
As Bob C. proved the old hafler amps are great test beds for testing out your designs.
Trendsetter Electronics - Electronic Components Distributor
Trendsetter Electronics - Electronic Components Distributor
The new design uses lsk489 and its p-ch complement lsj689, to form the i/p stage and create the push-pull vas(voltage amp stage). I assume he used the old Hitachi o/p devices and did not use the newer semelab parts.
Bob's specific Hafler upgraded design, I believe will be in his new book, coming out, I assume in 2017. There is a thread about the book, Bob C. participates so can answer all your ?'s
I doubt that Bob C. will be offering blank pcbs for sale, so that will be up to someone else, who knows, have ask or wait and see. I though he stated that he built it up on a protoboard, so anyone can do it if the information is available.
The parts come in a metal can, more expense and harder to get. I assume Bob used the metal can, since he has ties with this mfg and got samples. If I was to do a pcb I would do it in smt and have a dual footprint for the jfets. Execution is up to the designer's goals.
Trendsetter Electronics - Electronic Components Distributor
Trendsetter Electronics - Electronic Components Distributor
The new design uses lsk489 and its p-ch complement lsj689, to form the i/p stage and create the push-pull vas(voltage amp stage). I assume he used the old Hitachi o/p devices and did not use the newer semelab parts.
Bob's specific Hafler upgraded design, I believe will be in his new book, coming out, I assume in 2017. There is a thread about the book, Bob C. participates so can answer all your ?'s
I doubt that Bob C. will be offering blank pcbs for sale, so that will be up to someone else, who knows, have ask or wait and see. I though he stated that he built it up on a protoboard, so anyone can do it if the information is available.
The parts come in a metal can, more expense and harder to get. I assume Bob used the metal can, since he has ties with this mfg and got samples. If I was to do a pcb I would do it in smt and have a dual footprint for the jfets. Execution is up to the designer's goals.
Last edited:
I do not know why but yesterday when I checked I did not found theses parts on this site....maybe too much wine....
They are not that expensive for such a part.
Thanks for the link !
I could have a pcb layout done with the dual jfet circuit but I prefer the double die semelab which is easier to mount close to the pcb than the to-3 package.... however with the DH-200 heatsink it is not so easy to have the to3p Semelab on the pcb..
Dual footprint for the jfet is indeed a good idea.
Fab
They are not that expensive for such a part.
Thanks for the link !
I could have a pcb layout done with the dual jfet circuit but I prefer the double die semelab which is easier to mount close to the pcb than the to-3 package.... however with the DH-200 heatsink it is not so easy to have the to3p Semelab on the pcb..
Dual footprint for the jfet is indeed a good idea.
Fab
Last edited:
yeah enough wine will do that to your mind.
agree I do not like the long leads to the mosfets, but I believe that Bob C. got it to work, I do not know the details of the construction.
I am using the alf16n(p)16W in a old Sansui G-7500 that was upgraded with a pioneer sx-1050 p/s and opc lme49830 wire amp pcb. It sounds great, only blasted it once or twice. I measured its performance, got the 120W out of it, 620/650ns rise/fall time was impressive, not sure if any bjt's can go that fast.
agree I do not like the long leads to the mosfets, but I believe that Bob C. got it to work, I do not know the details of the construction.
I am using the alf16n(p)16W in a old Sansui G-7500 that was upgraded with a pioneer sx-1050 p/s and opc lme49830 wire amp pcb. It sounds great, only blasted it once or twice. I measured its performance, got the 120W out of it, 620/650ns rise/fall time was impressive, not sure if any bjt's can go that fast.
Attachments
yeah, certainly does not look like a hafler in any way and a bit of an off topic discussion.
I had to put in a different HS to make it work. I had a sx-1250 trans to try out, but that was not going to work because it was too big and I could not get enough HS in the chassis.
I guess you also noticed it is still running on the orig ecaps. I have a bit of faint hum, isolated to the pre-amp section. I put inpre-out/power-in jumpers on the back, so I can isolate the gain stages.
Hopefully in 2017 I can recap and eliminate the faint hum. Not sure if it was there to begin with, since the unit smoked its orig transf and main pcb.
Good luck with your hafler mods everyone.
I had to put in a different HS to make it work. I had a sx-1250 trans to try out, but that was not going to work because it was too big and I could not get enough HS in the chassis.
I guess you also noticed it is still running on the orig ecaps. I have a bit of faint hum, isolated to the pre-amp section. I put inpre-out/power-in jumpers on the back, so I can isolate the gain stages.
Hopefully in 2017 I can recap and eliminate the faint hum. Not sure if it was there to begin with, since the unit smoked its orig transf and main pcb.
Good luck with your hafler mods everyone.
Hi David
I think the Hafler equipment, particularly the amps are well worth restoring.
I taken several approaches myself, including the old Pooge article mods, freshening up DH200 and DH220 amps with new components, modding some with improvements discussed earlier in this thread such as improved star grounding, inrush protection, larger main caps, polypropylene caps, metal film resistors, torroid transformers etc. and even purchasing a complete upgrade kit.
The freshening up route and modding requires you to track down all the components you need, where as a kit offers the convenience of including most of what you need in quality components.
The Musical Concepts kits are nice, but decided to go with one of these kits myself:
HAFLER DH220 HIGH END AUDIOPHILE UPGRADE KIT TOSHIBA JFET CASCODE TOPOLOGY | eBay
It is easy to build, includes all the required board components and the redesigned board is smaller than the oem boards which adds extra space inside the chassis which is nice.
I did my own variation of it with 2 chassis and putting it together in a monoblock configuration, and to date are my favorite amps.
That being said, if you have the time skim through the earlier posts and it should give you enough information to figure out what you might want to do, or at least be able to ask specific questions on various improvements.
For the Hafler preamp, I did get my hands on a DH101, but only did a part for part component replacement/upgrade with quality components such as electrolytics & metal film resistors, and then carefully redressed any wiring that needed to be improved on.
The end result was a no frills preamp that was quiet, sounds good and was easy to work on.
I think the Hafler equipment, particularly the amps are well worth restoring.
I taken several approaches myself, including the old Pooge article mods, freshening up DH200 and DH220 amps with new components, modding some with improvements discussed earlier in this thread such as improved star grounding, inrush protection, larger main caps, polypropylene caps, metal film resistors, torroid transformers etc. and even purchasing a complete upgrade kit.
The freshening up route and modding requires you to track down all the components you need, where as a kit offers the convenience of including most of what you need in quality components.
The Musical Concepts kits are nice, but decided to go with one of these kits myself:
HAFLER DH220 HIGH END AUDIOPHILE UPGRADE KIT TOSHIBA JFET CASCODE TOPOLOGY | eBay
It is easy to build, includes all the required board components and the redesigned board is smaller than the oem boards which adds extra space inside the chassis which is nice.
I did my own variation of it with 2 chassis and putting it together in a monoblock configuration, and to date are my favorite amps.
That being said, if you have the time skim through the earlier posts and it should give you enough information to figure out what you might want to do, or at least be able to ask specific questions on various improvements.
For the Hafler preamp, I did get my hands on a DH101, but only did a part for part component replacement/upgrade with quality components such as electrolytics & metal film resistors, and then carefully redressed any wiring that needed to be improved on.
The end result was a no frills preamp that was quiet, sounds good and was easy to work on.
Hi rsavas,
Yes, I noticed the original capacitors. They run so hot that I typically replace the caps and the pass transistors. Most of the Pioneer LV regulator PCBs run upside down under the chassis and are pretty baked by now. They knew better.
Love to hear about your amp after you have a chance to work on it some more.
-Chris
Yes, I noticed the original capacitors. They run so hot that I typically replace the caps and the pass transistors. Most of the Pioneer LV regulator PCBs run upside down under the chassis and are pretty baked by now. They knew better.
Love to hear about your amp after you have a chance to work on it some more.
-Chris
I have had an original DH-220 on the bench for awhile and decided to add a steel mesh compartment (and feet!) under the base to fit separate supplies for each channel off the same transformer - large diameter caps (B41550 Epcos), simple C-Multiplier (& heatsinks) discrete diodes, power inlet, filters, etc - toying with the idea of upgrading components but don't think it's really necessary