Yes, I currently have 470 and 220 ohm values for the N and P channel gate resistors in my DH500. With the addition of the 33pF caps on the gate to drain for each the N channel MOSFETs, I was wondering if this would allow reducing the N channel gate resistors while maintaining stability. I’m also in the process of changing out the MOSFETs to single die Exicons. The listed input capacitances for these are 500 and 700pF for the N and P channels, respectively. Based on this, reducing the N channel gates to 330 ohm would result in roughly the same high frequency pole as the 220 ohm P channel.
Hi Bill,
Thanks, I am very happy with the performance at the moment,.
Currently I am using 220 Ohm for the P channels and 470 Ohm for the N channels. (Dual die Exicon ECW20N20-S/ECW20P20-S)
-Dan
Hi danieljw
Don’t forget that double die mosfet has twice the input capacitance so 470 ohms for double die is equivalent to 940 ohms for single die device.
Thanks for posting your project.
From what I see the original DH-200 schematics provides good ideas for variations and sure Bob has done a good job with the new design DH-200/220C.
Dual die a Exicon is my preferred choice of output mosfet in most of my designs.
Fab
Don’t forget that double die mosfet has twice the input capacitance so 470 ohms for double die is equivalent to 940 ohms for single die device.
Thanks for posting your project.
From what I see the original DH-200 schematics provides good ideas for variations and sure Bob has done a good job with the new design DH-200/220C.
Dual die a Exicon is my preferred choice of output mosfet in most of my designs.
Fab
Hi danieljw
Don’t forget that double die mosfet has twice the input capacitance so 470 ohms for double die is equivalent to 940 ohms for single die device.
Thanks for posting your project.
From what I see the original DH-200 schematics provides good ideas for variations and sure Bob has done a good job with the new design DH-200/220C.
Dual die a Exicon is my preferred choice of output mosfet in most of my designs.
Fab
Hi Fab,
I recall that the ECW20N20 has 16pF Crss whilst the ECW10N20 has 10pF Crss.
Bob has indeed done a good job with the DH20/220C.
I am becoming a fan of the dual die Laterals also, if you add 33pF across gate to drain on the N channel(s), N and P become a closer Crss value to each other.
-Dan.
FYI
Bob Cordell’s DH-220C design has been put to print in the July Audio Xpress magazine. It is in two parts, first part is some history and a description of op. part two will be on the build. I have to thank Bob for giving me the opportunity to work with him to make this design available to the DIY audio community
Jan Didden also inspired us to write the article and helped in the editing
Also want to thank AX for giving us the opportunity and lets not forget all the constructors for their excellent builds and feedback.
The more I reflect the more folks need praise and appreciation, LIS and Profusion for providing us with samples to work with.
Cheers
Rick
Bob Cordell’s DH-220C design has been put to print in the July Audio Xpress magazine. It is in two parts, first part is some history and a description of op. part two will be on the build. I have to thank Bob for giving me the opportunity to work with him to make this design available to the DIY audio community
Jan Didden also inspired us to write the article and helped in the editing
Also want to thank AX for giving us the opportunity and lets not forget all the constructors for their excellent builds and feedback.
The more I reflect the more folks need praise and appreciation, LIS and Profusion for providing us with samples to work with.
Cheers
Rick
Last edited:
Rick, it has been a great pleasure working with you on this project, and your expertise was truly key to making this project a reality and to making it available to many DIYers. I also concur in the thanks you give to those who have helped us. The aX folks did a great job in putting together the article. aX is a great publication in the tradition of Audio Amateur in which Ed Dell (RIP) would be proud. I encourage all DIYers to subscribe. The editions have gotten better and better with every issue, and Jan has been a big part of making that happen.
Cheers,
Bob
I was a subscriber to AA, Glass Audio, and then AudioXpress until Mr. Dell passed away and the publication was sold to a European group. I stuck with the AudioXpress for a few more years but gave up the publication when the DIY articles disappeared and it turned into mostly reviews of equipment and tutorials which were nowhere near the kind of lucidity and depth provided by Walter Jung and Nelson Pass. To tell the truth, I was frustrated and angry at the end.
Are you telling us that it is once again at the level of quality during the Ed Dell years? If so, then I would readily subscribe.
Are you telling us that it is once again at the level of quality during the Ed Dell years? If so, then I would readily subscribe.
Good thing I have 6 DH 220Cs and a Perreaux version of the DH 500 C already under way.
Invest now, the price of used Haflers are on their way up.
Would you use the same front end topology for a line stage preamp with a pair of TO220s output ?
And many thanks to Bob and Rick for all the hard work.
Invest now, the price of used Haflers are on their way up.
Would you use the same front end topology for a line stage preamp with a pair of TO220s output ?
And many thanks to Bob and Rick for all the hard work.
Last edited:
Indeed, over the last years AX has been going back to the format from the times of Ed Dell. More tech/diy articles, less 'commercial' articles. The realities of the economic situation means they cannot do completely without ads and commercial reviews, but diyaudio becomes a larger part of it with each issue.
For an impression: audioXpress The Leading Global Audio Development & Design Magazine | audioXpress
For me the great advantage is that AX articles are vetted for technical correctness. That doesn't mean there are never errors, but you will not be presented with wacky and downright wrong stuff that permeated the 'net. That is important especially when you are going into an area where your own expertise is small or non-existent.
You'll recognize many names from diyaudio!
Jan
Last edited:
One day I plan on doing a re-layout of DH-200C to better fit a DIYAudio chassis. Probably a new OPS too since the inductor, zobels are better put on the OPS imo.
Doing it in mixed smt/tht opposed to all tht would be an advantage to some, that might not otherwise want to solder smt nor tht by hand.
Anyone knows who soldered up a DH-220C that it takes a fair amount of time to stuff, solder, test.
Right now I have my yam T-85 tuner running thru a stepped attenuator straight into the dh-200. I do not need more gain, since I do not blast it anymore, all I need to add is, source switching, for more source i/p's, (rca jacks, reed relays, switches) and two log taper pots, for att'n and balance, rev up the drill press for another day
Doing it in mixed smt/tht opposed to all tht would be an advantage to some, that might not otherwise want to solder smt nor tht by hand.
Anyone knows who soldered up a DH-220C that it takes a fair amount of time to stuff, solder, test.
Right now I have my yam T-85 tuner running thru a stepped attenuator straight into the dh-200. I do not need more gain, since I do not blast it anymore, all I need to add is, source switching, for more source i/p's, (rca jacks, reed relays, switches) and two log taper pots, for att'n and balance, rev up the drill press for another day
Last edited:
Hi Rick,
I would argue that you need a buffer after the volume control to deal with cable capacitance and sometimes non-linear input impedance. Yes, it will work without the buffer, but depending on the specifics, it may not be delivering the sound quality you think you are getting.
-Chris
I would argue that you need a buffer after the volume control to deal with cable capacitance and sometimes non-linear input impedance. Yes, it will work without the buffer, but depending on the specifics, it may not be delivering the sound quality you think you are getting.
-Chris
Bob & Rick;
Congratulations on the article; I'm looking forward to receiving my issue.
With such good chemistry and the success of this article, might you guys be encouraged to take a similar stab at an updated design/article/PCB for Bob's nice 50W MOSFET amp with the error correcting output stage from long ago?
(Sorry, I had to ask!)
Congratulations on the article; I'm looking forward to receiving my issue.
With such good chemistry and the success of this article, might you guys be encouraged to take a similar stab at an updated design/article/PCB for Bob's nice 50W MOSFET amp with the error correcting output stage from long ago?
(Sorry, I had to ask!)