It’s alive!!!!
New Exicon outputs are in, bias set without a problem, dim bulb test passed, and played music through expendable speakers.
I AM THRILLED.
It sounds great, so far. I will try it out in the main rig tomorrow. I will also replace the AFE tall caps once the appropriate ones arrive.
Thanks to Bob and Rick for their generosity with this design and patience with circuit dullards like myself.
This is "music to my ears". It's wonderful to hear that someone else has been successful with one's design.
Cheers,
Bob
I’ve been listening to the completed amp for about 8 hours now. It’s just great. I think it provides considerably more “fullness” of the source material than what I have become accustomed to with the admittedly great Aiyima TP2351 amp (with OPA1656). I think this must be what people call bass authority, or speaker control. There is no apparent lack of detail, either.
I’m throwing a whole heap of subjective bias into this assessment, yet I don’t care. This is my first significant amp build and I am enthralled with it. My dog appreciates the high bias for class A operation.
I do not want to stop listening to music. That is what this is all about.
Thanks for your comments and keep on listening to great music. Music takes me to another place. And thank you for being an early adopter of this design.
Your observations seem to be in line with some others' as well. We don't always know what makes a particular amplifier sound the way it does or why it sounds better than others. But it is fun to speculate.
My sense is that in this amplifier it is a good combination of the JFET front end, the BJT middle, and the lateral MOSFET output. The lateral's ability to be biased hotter without creating more switching distortion from GM doubling, and basically the more-the-better preference of laterals in regard to bias may be a factor. The resulting large class A region and relatively smooth transition to class AB certainly can't hurt. The use of a DC servo may also have a role in better LF response.
This, of course, is all speculation colored by my design style preferences and biases. The fact that the amplifier tests so well down to 2-ohm loads may also have something to do with its seeming authority in driving loudspeakers, but I have never tested a stock Hafler down to 2 ohms, so I don't know that it is not just as good in that department.
Thanks again for sharing your experience with us.
Cheers,
Bob
It is certainly very fun to play with different speakers to see how an amplifier performs with different drivers, alignments, etc.
My normal main speakers are the great EL70 Microtowers designed by Planet10 and superbly built by Evan Cotler. I have an ApexJr Mylar tweeter highcrossed on the back for a little extrtra sparkle.
I brought up my venerable Zilch Econowave design speakers from the basement setup to see how a more classic type design would work. I built those speakers with a 10” peerless woofer and Selenium D220ti compression driver in sealed, formerly-JBL-L56 cabinets.
I can’t decide which I like better.
Totally different philosophies, pluses, and minuses to each. The Econowaves are definitely more in-your-face for detail and clarity at the opposite ends of the hearing spectrum. The Microtowers are more engaging in overall balance with fullrange drivers and transmission line low end. The DH-220C is sublime with both sets.
I don’t have room in the living room for the Econowaves, so I’ll just have to build another amp for them in the basement. They already do well with an all-original Hitachi HMA-6500, but I need more projects for the pandemic!
My normal main speakers are the great EL70 Microtowers designed by Planet10 and superbly built by Evan Cotler. I have an ApexJr Mylar tweeter highcrossed on the back for a little extrtra sparkle.
I brought up my venerable Zilch Econowave design speakers from the basement setup to see how a more classic type design would work. I built those speakers with a 10” peerless woofer and Selenium D220ti compression driver in sealed, formerly-JBL-L56 cabinets.
I can’t decide which I like better.
Totally different philosophies, pluses, and minuses to each. The Econowaves are definitely more in-your-face for detail and clarity at the opposite ends of the hearing spectrum. The Microtowers are more engaging in overall balance with fullrange drivers and transmission line low end. The DH-220C is sublime with both sets.I don’t have room in the living room for the Econowaves, so I’ll just have to build another amp for them in the basement. They already do well with an all-original Hitachi HMA-6500, but I need more projects for the pandemic!
Attachments
More projects, huh? Bob is a great guy and his designs are solid. Glad to see how much fun you are having. This is indeed what this hobby is all about. Now for a suggestion: how about a nice 6SN7 tube preamp to drive Bob's design? Gives you that tube sound + the solid bass of the new Hafler 220's.
Something like this: JE Labs Linestage | D a r k L a n t e r n
Can be built with 6sn7's (76 not needed) and point-2-point wiring. Fun project!
And the low part count enables you to play with more expensive capacitor options.
Good luck.
Something like this: JE Labs Linestage | D a r k L a n t e r n
Can be built with 6sn7's (76 not needed) and point-2-point wiring. Fun project!
And the low part count enables you to play with more expensive capacitor options.
Good luck.
If your are going to the expense of a tube pre, I was thinking that one could just use a couple of DH-220C AFE’s as your line stage. A preamp and amp with no caps in the signal path That is if you need the extra gain. In many cases as with a CD, all you need is a variable attenuator.
Another thought was to mod my Dh-200 to add a selector and a attenuator.
That is if you need the extra gain. In many cases as with a CD, all you need is a variable attenuator.Another thought was to mod my Dh-200 to add a selector and a attenuator.
I really like using my Topping E30 DAC for volume attenuation. I only have 2 digital sources: Logitech Squeezebox and a Roku for TV. I definitely don’t need any more gain than the DH-220C and like keeping the signal chain simple.
I already have a class d project in mind for a warm-weather amp/second system and have a speaker project looming. Maybe tubes or class a solid state will be a future amp project.
I already have a class d project in mind for a warm-weather amp/second system and have a speaker project looming. Maybe tubes or class a solid state will be a future amp project.
The diodes seem to measure good with the diode check; all measuring around .58 each. Q1 and Q2 seem to test good with the diode check in-circuit.
All of the transistors seem to test fine in-circuit with the diode check, which I know doesn't mean they're 100% good. I guess I'll make my way through testing the caps for shorts/opens. I'll bring home an ESR meter from work but that may not be the most useful if this is a DC biasing issue. It'll let me see how those electrolytics are doing.
I can make some more annotations to the schematic and post them. Thanks for the help.
I can make some more annotations to the schematic and post them. Thanks for the help.
alive
The dead board lives! Thanks to rsavas and other forum members who have helped point me in the right direction.
It was indeed a single faulty component causing the bias issue. R4 which is supposed to be 47k was open. It had no physically obvious signs that it was faulty. I've worked in electronics for quite awhile and all the resistors I've ever measured as open were obvious.
Thanks again.
The dead board lives! Thanks to rsavas and other forum members who have helped point me in the right direction.
It was indeed a single faulty component causing the bias issue. R4 which is supposed to be 47k was open. It had no physically obvious signs that it was faulty. I've worked in electronics for quite awhile and all the resistors I've ever measured as open were obvious.
Thanks again.
Attachments
Does anyone where Darcy Staggs, the one that published the original DH-220 mod in TAA 4/93 might be?
Didn't find it on FB. There's one Darcy E. Staggs in Google, aged 80, which might be around right how old he might be.
I would love to discuss the regulator he suggested, because when I opened a thread here on this forum on high-voltage low current regulators for power amps, and I started with using the 3X7 that Darcy did use, a big no-no came as a warning not to use that regulator in that way. That it would be easy for it to malfunction and blow the DH-220.
Using the LM317 with higher voltages
In that thread you will be able to find other discrete regulators that were suggested to me, all of them safe to use and involving no damage risk. All of them were simulated in LTSpice, and I got to quite interesting conclusions and compromises. They could be used on the Hafler too.
Didn't find it on FB. There's one Darcy E. Staggs in Google, aged 80, which might be around right how old he might be.
I would love to discuss the regulator he suggested, because when I opened a thread here on this forum on high-voltage low current regulators for power amps, and I started with using the 3X7 that Darcy did use, a big no-no came as a warning not to use that regulator in that way. That it would be easy for it to malfunction and blow the DH-220.
Using the LM317 with higher voltages
In that thread you will be able to find other discrete regulators that were suggested to me, all of them safe to use and involving no damage risk. All of them were simulated in LTSpice, and I got to quite interesting conclusions and compromises. They could be used on the Hafler too.
It’s alive!!!!
Thanks to Bob and Rick for their generosity with this design and patience with circuit dullards like myself.
Congratulations, I just ordered the 4-board set to resuscitate another DH-200C. I look forward to sharing progress, asking questions, and poring over the many ideas on this thread.
Six.
Experience with Exicon MOSFETs
1) Anyone here have .direct experience. using the Exicon MOSFETS. I signed up for an account and am about to place my first order. The P channel and N channel devices [according to Profusion] are supplied in matched sets...
2) I am curious how close P and N channels are to each other. Which will influence the quantities that I order. I am also undecided on the TO3 ~vs~ TO247 devices. I will likely buy a mix of both... Price is also a minor factor... re-dressing leads, not that big a factor, in the scheme of things.
3) It has been said by a most viable source that the TO3s 'can be' more micro-phonic? than the TO247 devices. At the time I owned (his 'old') Levinson No. 336 sample, with TO247 bipolar power transistors (that were shared by 334, 335 and 336) The earlier No. 331, 332, 333 all had TO3 devices... A conversation with a close lifelong friend, (then a Madrigal employee) shared this with me. *As a background qualifier to my comment / viewpoint.
4) I also thought that I had read (here?) the TO3 may have improved heat transfer properties... Their direct plug / play prospect is appealing...
Any insight and help is appreciated...
@anatech, @Bob Cordell... Can either of you weight in on the prospect and topic?
1) Anyone here have .direct experience. using the Exicon MOSFETS. I signed up for an account and am about to place my first order. The P channel and N channel devices [according to Profusion] are supplied in matched sets...
2) I am curious how close P and N channels are to each other. Which will influence the quantities that I order. I am also undecided on the TO3 ~vs~ TO247 devices. I will likely buy a mix of both... Price is also a minor factor... re-dressing leads, not that big a factor, in the scheme of things.
3) It has been said by a most viable source that the TO3s 'can be' more micro-phonic? than the TO247 devices. At the time I owned (his 'old') Levinson No. 336 sample, with TO247 bipolar power transistors (that were shared by 334, 335 and 336) The earlier No. 331, 332, 333 all had TO3 devices... A conversation with a close lifelong friend, (then a Madrigal employee) shared this with me. *As a background qualifier to my comment / viewpoint.
4) I also thought that I had read (here?) the TO3 may have improved heat transfer properties... Their direct plug / play prospect is appealing...
Any insight and help is appreciated...
@anatech, @Bob Cordell... Can either of you weight in on the prospect and topic?
Exicon lateral mosfet
Hi Ozark
I have been using Exicon Mosfet for years in my USSA3 and 5 amps and the USSA5 have been built many times by members on this forum. My FSSA amps also use the same Exicon mosfet. I have used them also in the Goldmund Telos clone. I have always used the TO-264 double die version because you get 2 transistors perfectly matched in the same package. If you need more then a pair then you can buy the part with -S suffix thus they are from the same VGS grade range. Since they are limited numbers of manufacturing batches they usually all come from the same batch for the same channel when you order them. You can contact Profusion for special orders too. As for the TO-3 version i would use them mostly If you have the heatsink suitable for them. I use ceramic pad with to-264 with small amount of grease and get good heat transfer. In my class A amps they run steady 1.4A per transistor package.
Fab
Hi Ozark
I have been using Exicon Mosfet for years in my USSA3 and 5 amps and the USSA5 have been built many times by members on this forum. My FSSA amps also use the same Exicon mosfet. I have used them also in the Goldmund Telos clone. I have always used the TO-264 double die version because you get 2 transistors perfectly matched in the same package. If you need more then a pair then you can buy the part with -S suffix thus they are from the same VGS grade range. Since they are limited numbers of manufacturing batches they usually all come from the same batch for the same channel when you order them. You can contact Profusion for special orders too. As for the TO-3 version i would use them mostly If you have the heatsink suitable for them. I use ceramic pad with to-264 with small amount of grease and get good heat transfer. In my class A amps they run steady 1.4A per transistor package.
Fab
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In the process of placing my order
No I did not hit BUY yet... The "s" versions *as stated* on their website
are matched. I plan to measure them anyway... for peace of mind.
I will specify *as you say* upon ordering...
TY for input.
No I did not hit BUY yet... The "s" versions *as stated* on their website
are matched. I plan to measure them anyway... for peace of mind.
I will specify *as you say* upon ordering...
TY for input.
Excellent Fab! Thank you.
Hey Fab... great input... the point you make on the TO264 is quite appealing,
really registers with me. I am now rethinking my order...
Frankly, I am ready to abandon the Hafler chassis (I own 10 different amps)
they have become Franken'amps... with trials and modeling.
They are clean, sensibly built... just too cramped.
I have (2) 500 and (1) 600 chassis. Do the "dual" TO3 or TO264 devices
require or are they optimized to operate on higher voltages only?
[I am assuming so] Or will they work on the ~67 volt rail?
for experimenting...
~ Having used the Exicons, would you even use the Hitachi MOSFETs
[if available] or do you prefer the sound of the Exicons over them???
A close friend thinks I that will like the Exicons much better...
I have ordered a few 58v / 1000va toroids, and I am planning to use...
have the parts on have to build a [multiple] C/L/C supplies.
Hey Fab... great input... the point you make on the TO264 is quite appealing,
really registers with me. I am now rethinking my order...
Frankly, I am ready to abandon the Hafler chassis (I own 10 different amps)
they have become Franken'amps... with trials and modeling.
They are clean, sensibly built... just too cramped.
I have (2) 500 and (1) 600 chassis. Do the "dual" TO3 or TO264 devices
require or are they optimized to operate on higher voltages only?
[I am assuming so] Or will they work on the ~67 volt rail?
for experimenting...
~ Having used the Exicons, would you even use the Hitachi MOSFETs
[if available] or do you prefer the sound of the Exicons over them???
A close friend thinks I that will like the Exicons much better...
I have ordered a few 58v / 1000va toroids, and I am planning to use...
have the parts on have to build a [multiple] C/L/C supplies.