I found the Hafler DH220 schematic online. I copied it and attached it.
I'm referencing Papa's FE board, since it has +C and -C connections, which I think I need for the Hafler. (Guessing the ZM FE board would be adaptable also, but I don't see the obvious connection points.) I've written in red, where I think the connections from the DH220 would connect with Papa's FE.
I'd appreciate it if someone would check my connections and let me know if I am on the right track. Thanks.
I'm referencing Papa's FE board, since it has +C and -C connections, which I think I need for the Hafler. (Guessing the ZM FE board would be adaptable also, but I don't see the obvious connection points.) I've written in red, where I think the connections from the DH220 would connect with Papa's FE.
I'd appreciate it if someone would check my connections and let me know if I am on the right track. Thanks.
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easier is to dissmantle everything but mosfets on heatsinks and abandon all Hafler nomenclature, than the other way
anyway, if it's easier for you to think that way. here it is
observe NFB edit
edit:replaced pic, had error with NFB, now good
anyway, if it's easier for you to think that way. here it is
observe NFB edit
edit:replaced pic, had error with NFB, now good
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It is a good idea to briefly remove the power Mosfets from your DH-220, clean off the dried thermal paste, apply fresh thermal paste to the mica and Mosfet case and re-install the devices. Hopefully it goes without saying that the old 10,000 uF power caps also need to be replaced. There is plenty of room inside the chassis for two sets of 18,000 uF, 80V electrolytics in their place.
This is excellent advice. ZM and TA, you guys are great. Good luck to wg45! I look forward to seeing your Passified Hafler!
Thanks, ZM. It's clear now from your posted schematic. I'll build the boards, try it out and post some pics here. Let's see if we can get one old Hafler off the rack in the garage and back in service.
TA- the amp has fairly recent filter caps. I'll check them to make sure they're still within spec. I'll update the Hitachii? with some new thermal paste, too.
Thanks to all for the support!
O Mighty Not So Dodo, would you be able to give similar advice for the attached schematic? I have two of these amps. One got banged up in shipping (back panel damage) and is begging for extensive tweaking. I’m assuming somewhere in the highlighted section in the attached are the points for stasis FE…
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No rush. At your convenience. Thank you!
I am not intending to keep +-80vdc. I have a +-67VDC smps I want to swap in for the massive transformer and filter caps.
I am not intending to keep +-80vdc. I have a +-67VDC smps I want to swap in for the massive transformer and filter caps.
okidoki
there must be somewhere some talk about FE for higher voltages
can you find it (this is just 1150 posts in thread, anyway)?
there must be somewhere some talk about FE for higher voltages
can you find it (this is just 1150 posts in thread, anyway)?
I was aiming for 67V rails for this OS.
looks like there are recommendations for different ZTXs around posts 488+
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/post-6462835
…and 506+
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/post-6463812
looks like there are recommendations for different ZTXs around posts 488+
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/post-6462835
…and 506+
https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/post-6463812
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Thought I would post a bit of an update as it has been awhile.
Things have happened. I bought a different amp, two in fact; a pair of Quad II monoblocks. Serviced them sympathetically, refreshed the valves. I've had them in the system for about a month, including 10 days of isolation with COVID in my hifi room. Pro tip: buy a sofa bed for your hifi room. "No, I'll isolate on the sofa bed. Yes, I'll be okay in there, with my hifi!". Genius.
Anyhow, I like the Quads. With ESL57s they are quite special. But I had noticed a bit of a high bass "bloom" through a room resonance. Tried to notch it out with DSP, but could never get rid of it without upsetting the sound. Long story short, last weekend I swapped the Stasis back in, having double checked the bias, temps and offsets. The Stasis is one hell of an amp, so clear and clean, just love it. It edges the KSA50 out, but then it does things differently to the Krell and I'm afraid the F5T is off to be sold, sorry.
Conclusion: You all must build this amp. 😊
PS: I have been having a look at the optical bias Stasis schematics, I can't figure out where the connection to Stasis Collector goes.
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I have been slow to build a new fanged MOSFET amp since I pumped up the power supply on my SA/1 amps.
It IS clean and clear, so no motivation to move beyond it. Maybe one of these days but hard to imagine a better sounding amp.
Which makes me wonder how much better would a new pair of XA200.8 sound? Would my aging ears hear the difference? 🙂
It IS clean and clear, so no motivation to move beyond it. Maybe one of these days but hard to imagine a better sounding amp.
Which makes me wonder how much better would a new pair of XA200.8 sound? Would my aging ears hear the difference? 🙂
XA200.8 vs. SA/1 ?
I believe Pa did learn something useful, in between these two amps
in short - you can expect more of everything with XA200.8, while sounding sweeter
in those days, even Treshold didn't care much about THD Spectra, as they did for overall THD level
I believe Pa did learn something useful, in between these two amps
in short - you can expect more of everything with XA200.8, while sounding sweeter
in those days, even Treshold didn't care much about THD Spectra, as they did for overall THD level
When I make my own PCBs for this and other projects in the threads, I wonder if there are any written/unwritten etiqutte concerning honoring the origin of the design? I suppose I don't put the designers name on it, as they havent't approved my layout... Sure you all know this, but I don't - yet! (And, yes, I am having them produced i China.) Thank for any help!
🙂 morten
🙂 morten
These days I have PCBs turned in China but I still have the original silk screen for laying down resist on the PCBs before etching.
I have the bias so for up on my SA/1 that the THD Spectra is probably just 2nd and 3rd harmonics, but then it took a big power supply and heat sinks to run 8 amps of bias current into the 40 output transistors. 🙂
I have the bias so for up on my SA/1 that the THD Spectra is probably just 2nd and 3rd harmonics, but then it took a big power supply and heat sinks to run 8 amps of bias current into the 40 output transistors. 🙂