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Hafler DH-200/220 Mods
Hafler DH-200/220 Mods
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Old 15th March 2019, 06:26 PM   #1511
gbowling is offline gbowling  United States
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It's in his presentation file which can be found here.

https://www.diyaudio.com/forums/atta...6_dh220c-1-pdf

And there is a youtube of the full presentation here.

YouTube


gabo
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Old 15th March 2019, 06:28 PM   #1512
rsavas is offline rsavas  Canada
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AuroraB,

I am working off the slide set of the presentation material that is publicly available from Bob Cordell. There is a link a few threads back. It includes the complete design, enough for me to do up the design. Bob made up one channel in proto form, see pics. Bob is including the design in more detail in the new book.

Ray,
That is great information, Chris should take note as well :-) cascode IPS for the best amps, hands down
Do want to pay for the extra performance, is it worth it, will you notice?


Cheers
Rick

Last edited by rsavas; 15th March 2019 at 06:48 PM.
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Old 15th March 2019, 08:07 PM   #1513
mlloyd1 is online now mlloyd1  United States
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Hafler DH-200/220 Mods
yes, he retired a while ago and shut down his audio site.
but most of it is still available via the waybackmachine site.

mlloyd1

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Originally Posted by stevebogus View Post
I am happy to be wrong about this.

The Borbelyaudio website became inactive nearly ten years ago and I had assumed far too much.
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Old 15th March 2019, 08:39 PM   #1514
rsavas is offline rsavas  Canada
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The EB-SA2 is a mind-blowing mega-amplifier, achieving literally twice the sonic power and control of the legendary EB-SA1. It begins with a dual-differential input stage studded with the finest J-FET transistors available – transistors specifically designed for audio applications. This is brilliantly integrated with a MOS-FET pre-driver stage, MOS-FET driver stage and fully balanced Lateral MOS-FET output stage – featuring 24-each closely matched devices per channel.
Price: $34,995

And I think I am going over board with an exotic design
studded jfets, marketing hype.
What do you think, Linear Systems or Interfet jfet devices?
lateral mosfets from who?
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Old 15th March 2019, 09:16 PM   #1515
Endsurg is offline Endsurg
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Default Bi amping with two different models

I have a Hafler dh200 and a dh500 amplifier. Can I biamp with both?
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Old 17th March 2019, 05:42 PM   #1516
msb64 is offline msb64  Canada
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Bi-amping with 2 different models or even brands for that matter should not be an issue.
I put my most powerful amp on the bass drivers, and my best sounding amp on the mid/high drivers.
If your DH200 and DH500 are still vintage & original, you should consider at least recapping them though, as the electrolytics are well past their prime.
Also with the Haflers, many of them were built as kits and it wouldn't hurt to have them checked over by a pro technician.
I have seen some pretty scary builds myself, some I would not even test fire as is for risk of possibly damaging some hard to replace components.
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Old 17th March 2019, 05:48 PM   #1517
msb64 is offline msb64  Canada
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Gabo, not sure if you are aware or not, but Qu-aco seller Ed Fantasia has a significant history with Dynaco and Hafler.
From his auction details:
"Being intrigued with audio since 1973 has given much insight on the topic of amplification and proper design practice. My interest in audio continues to be both my hobby and my passion. Employment at both Dynaco as a technician and Hafler Co. as a project engineer was not only enjoyable but allowed me to work and converse with some very accomplished audio engineers."
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Old 17th March 2019, 07:22 PM   #1518
fab is online now fab  Canada
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Hafler DH-200/220 Mods
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Originally Posted by msb64 View Post
Bi-amping with 2 different models or even brands for that matter should not be an issue....
Provided that both amps have the same gain of course. Fortunately, the dh200 and 500 have both about the same gain. More precisely, the only difference in gain comes form the input divider resistors circuit. 2k/22k ohm for dh-200 and 1k8/47k ohms for dh-500. So about 4% more gain for the dh-500 which is relatively small. Added to that is the output impedance of the circuit feeding the amplifiers which will change a bit this value too.
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Old 17th March 2019, 10:35 PM   #1519
gp4Jesus is offline gp4Jesus  United States
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Quote:
Originally Posted by msb64 View Post
Bi-amping with 2 different models or even brands for that matter should not be an issue.
yup. Further, your EXO should allow adjustment to balance bass to upper frequencies.
Quote:
Originally Posted by msb64 View Post
I put my most powerful amp on the bass drivers, and my best sounding amp on the mid/high drivers.
yup. I allowed the damping factor to decide - 1000 into 8 ohms for woofers.
Quote:
Originally Posted by msb64 View Post
If your DH200 and DH500 are still vintage & original, you should consider at least recapping them though, as the electrolytics are well past their prime.
yup
Quote:
Originally Posted by msb64 View Post
...and it wouldn't hurt to have them checked over by a pro technician.
yup
Quote:
Originally Posted by msb64 View Post
I have seen some pretty scary builds myself, some I would not even test fire as is for risk of possibly damaging some hard to replace components.
see above.
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Old 18th March 2019, 03:23 AM   #1520
anatech is offline anatech  Canada
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Hafler DH-200/220 Mods
Hi Rick, all,
My comments are always in general unless I refer specifically to a shop, designer or famous hack artist. That last bit was thrown in as humour least someone take offense.

My long experience is that many mods done that change the schematic to any great degree are often done by people who really don't understand how to design something. Typically prickly individuals who don't take to questions too kindly. I'm sure you know the type.

Rick, I did not look at your posted schematic as I'm really under the gun at the moment as far as time is concerned. I only commented that I would like to see you work sometime. That is hardly a negative comment.

Best, Chris
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