Ha, you told in post #95 - 500 VA Donuts
so, I'm Dodo, not you
if you have multitap primary (2 x 115V connected in parallel), then use one NTC per primary
if not, increase fuse to 5A slow Blow
if that doesn't help, look in M. Johnson's thread (him not being happy with CL60)
or just go for active iteration - string of more CL60, bypassed with relay after 10 secs
so, I'm Dodo, not you
if you have multitap primary (2 x 115V connected in parallel), then use one NTC per primary
if not, increase fuse to 5A slow Blow
if that doesn't help, look in M. Johnson's thread (him not being happy with CL60)
or just go for active iteration - string of more CL60, bypassed with relay after 10 secs
ZM - some details.
Amp has been cooking for over an hour with Swiss and Swedish metal and hard rock playing into the test speakers: Megaton Sword and Hallas. It is sounding fantastic on the bench, by the way!!! Beautiful!!!
Temperatures:
Room: 19C
Top of chassis: 31C
Donut: 36C
Top of heatsink 51C
Aim thermal gun at outside of heatsink around location of SIT: 55C
I currently have have one pair of fuses feeding both donuts. Easy enough to install additional fuse holders. I'll order them today.
Mains power goes like this: switch, fuses (line + neutral), then split to 2 sets of mains wires. Each pair goes to a little CL-60 & AC Cap PCB, then to donut. The CL-60 board has 1 NTC per primary winding like F5 PSU drawing.
First things first I'll add additional fuse holders. I have new and improved CL60 PCB's in fab in china now, and I expect I'll have them in a week. I could try CL30's. I put those in my friend's F5 V3 Turbo's.
I tested with my MegaBlock humbuster tester. Left channel is dead quiet with transformer in any position. Right channel noise raises and lowers when I rotate the donut. I may flip the right donut to see what happens.
Maybe later tonight I can get the REW / Focusrite and play with bias settings / H2 levels. Or maybe I try it in the horn rig "as-is" to start...
Somewhere between here and US port of entry are some Chicklet caps i was going to try... I wonder when they will arrive. US Mail has been brutally slow lately. Yesterday I received a Christmas card that had spent 2 months in transit. New Hampshire to Ohio.... Crazy.
Amp has been cooking for over an hour with Swiss and Swedish metal and hard rock playing into the test speakers: Megaton Sword and Hallas. It is sounding fantastic on the bench, by the way!!! Beautiful!!!
Temperatures:
Room: 19C
Top of chassis: 31C
Donut: 36C
Top of heatsink 51C
Aim thermal gun at outside of heatsink around location of SIT: 55C
I currently have have one pair of fuses feeding both donuts. Easy enough to install additional fuse holders. I'll order them today.
Mains power goes like this: switch, fuses (line + neutral), then split to 2 sets of mains wires. Each pair goes to a little CL-60 & AC Cap PCB, then to donut. The CL-60 board has 1 NTC per primary winding like F5 PSU drawing.
First things first I'll add additional fuse holders. I have new and improved CL60 PCB's in fab in china now, and I expect I'll have them in a week. I could try CL30's. I put those in my friend's F5 V3 Turbo's.
I tested with my MegaBlock humbuster tester. Left channel is dead quiet with transformer in any position. Right channel noise raises and lowers when I rotate the donut. I may flip the right donut to see what happens.
Maybe later tonight I can get the REW / Focusrite and play with bias settings / H2 levels. Or maybe I try it in the horn rig "as-is" to start...
Somewhere between here and US port of entry are some Chicklet caps i was going to try... I wonder when they will arrive. US Mail has been brutally slow lately. Yesterday I received a Christmas card that had spent 2 months in transit. New Hampshire to Ohio.... Crazy.
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And now some pix.
Attachments
just give separate fuses to each Donut and you're good ...... be it pair or just one (in Europe, most of countries are not having oriented mains (neither plug nor wall thingie) and most gadgets having fuse are having it just in one line ; dunno, it is more logical to have both neutral and live fused, but logic is not what real life is)
in that case, one CL60 per Donut would do the work, no need to change
edit: tnx for thermal figures
in Summer, you'll be good with nice Babysitter, having two lazy 12cm fans
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After long cooking session I checked Iq and drain voltage for adjustment. One channel IQ check is great. 2A3/460mv. Other channel I adjust at 458, 459, click click click. Leave it alone? Or should I drop in a different value at R1 on mu board? 8k? 7k5?
damn
I'm so old that I can't differentiate 459 and 460mV
what's percentage ?
0.21%
(besides fact that you can't blindly trust to anyone, writing anything on the web, so why 460 should be carved in the stone? just back-down other channel to 459mV)
I'm so old that I can't differentiate 459 and 460mV
what's percentage ?
0.21%
(besides fact that you can't blindly trust to anyone, writing anything on the web, so why 460 should be carved in the stone? just back-down other channel to 459mV)
I haven’t gotten into playing with operating points. It is 2.3A the max? As it stands I can’t go higher. Or is the magic in playing with drain voltage?
2A3 is pretty much what group of source resistors at Mu mosfet are allowing
feel free to fire up THD Spectra measuring rig and xperiment until you find better combo of Iq and output node voltage (still keep it sorta middish of rail), which your ears prefer
that combo ( which you get with schm values) is pretty much best I could find, with that rail
for lesser overall THD , I'm certain only way is different approach, more complicated
lhquam last amp is nice example
all in all , sound-wise this is nice (and achievable!) approximation of Papa's SIT-2, just tad less wakoo than SIT-1, with some watts to spare
what next I'll cook with Tokins, time will show ...... not to mention quite possible future PL amp with these, which should represent one hell of fun to decipher
feel free to fire up THD Spectra measuring rig and xperiment until you find better combo of Iq and output node voltage (still keep it sorta middish of rail), which your ears prefer
that combo ( which you get with schm values) is pretty much best I could find, with that rail
for lesser overall THD , I'm certain only way is different approach, more complicated
lhquam last amp is nice example
all in all , sound-wise this is nice (and achievable!) approximation of Papa's SIT-2, just tad less wakoo than SIT-1, with some watts to spare
what next I'll cook with Tokins, time will show ...... not to mention quite possible future PL amp with these, which should represent one hell of fun to decipher
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Wow! Thanks for the detailed explanation ZM!!
I’ll stick with 2A3 (or 2A295!!) and play with voltages only.
Next SB I build will be for my friend. Boards are ready to go, so now I need to give him psu BOM and agree on chassis. I think he will go for monoblocs. 4U/300 looks like the chassis to use.
I’ll stick with 2A3 (or 2A295!!) and play with voltages only.
Next SB I build will be for my friend. Boards are ready to go, so now I need to give him psu BOM and agree on chassis. I think he will go for monoblocs. 4U/300 looks like the chassis to use.
I have been experimenting with the bias of the buffer and have found that increasing the bias to just 22mA gives a nice improvement to the bass. This improvement is in clarity and definition. I was amazed that so little a change would be noticeable and went back and forth many times. I ran it up to 25mA and down to 18mA the lower end the bass lost definition but bloomed more.
Best of all, these are easy changes, you just need to feel free to experiment a little.
🙂
Best of all, these are easy changes, you just need to feel free to experiment a little.
🙂
Fuses installed. Front LEDs installed. Donuts rotated and played with wires for low noise floor. Yellow chicklet caps installed. Sounds beautiful on the test bench! Tomorrow I’ll look at distortion profile and give a run in the horn rig.
Attachments
having 5 of blue ones in bypass position, I can't see why installing chicklet one, too
though, if green is broader, I'm not arguing 🙂
though, if green is broader, I'm not arguing 🙂
Classic...
I'm re-reading the this thread and the original SB thread to take notes on distortion graphs from ZM and Ben. This will give me some guidelines for when I play with REW and setting voltage.
Buried in the thread is ZM's original recommended donut sizes. Later in the thread is the discussion of overkill donuts. I missed the original recommendation, and went with overkill. Oops. A few bucks extra and extra weight. I'll have my buddy buy 300VA for his monoblocks, not the 2x500VA donuts I bought.
ZM - I didn't realize the blue 1.0uF caps are so similar to the yellow ones. Since the yellow ones were the last parts ordered for my SissySIT, and they came highly recommended for that amp, I figured it would be good to repeat a bit of the secret sauce here.
I'm re-reading the this thread and the original SB thread to take notes on distortion graphs from ZM and Ben. This will give me some guidelines for when I play with REW and setting voltage.
Buried in the thread is ZM's original recommended donut sizes. Later in the thread is the discussion of overkill donuts. I missed the original recommendation, and went with overkill. Oops. A few bucks extra and extra weight. I'll have my buddy buy 300VA for his monoblocks, not the 2x500VA donuts I bought.
ZM - I didn't realize the blue 1.0uF caps are so similar to the yellow ones. Since the yellow ones were the last parts ordered for my SissySIT, and they came highly recommended for that amp, I figured it would be good to repeat a bit of the secret sauce here.
blue ones are Polycarbonats (Philips MKC)
those yellow ones you bought are same, I believe
nothing wrong with 500VA Donuts, if you ask me
those yellow ones you bought are same, I believe
nothing wrong with 500VA Donuts, if you ask me
