-remove plastic drek ; easy if you heat it shortly with heat gun , set to mid temp
-usually it's needed to cut solder connection on upper side of lug with cutters (pliers) so you can squeeze wire properly - each half independently
-solder it properly
-place heatshrink tube of appropriate color and dress it with heatgun
-that's proper connection
no issues I can predict
except if you want to call your deliberate playing with output parts xconductance - an issue
Good.
I like to tinker uninhibited.
This is a green light.
The bbq has free beer. Hahahahahaha
The sissy sure likes to creep up. I thought it was set at 1.8A @ 52*C and in 3 hours 2.1A @ 56*C. The Laser gun is sure helpful for ”sissysiting”, is this a thing now? 
I have no clue on why R18 value was wrong. I was supposed to order the proper value resistor with 7805 and then after 6 month delay things went sideways like Wiley on a rocket.
Sound is very pleasing with Jensen, very detailed with wonderful tone and presentation. Thankyou ZenMod, Papa, DiyAudio crew.
It’s a keeper!
Now that Sissy is giving M2 a break, I might have to rebuild it with X boards for more sound options.
I have no clue on why R18 value was wrong. I was supposed to order the proper value resistor with 7805 and then after 6 month delay things went sideways like Wiley on a rocket.
Sound is very pleasing with Jensen, very detailed with wonderful tone and presentation. Thankyou ZenMod, Papa, DiyAudio crew.
It’s a keeper!
Now that Sissy is giving M2 a break, I might have to rebuild it with X boards for more sound options.
I thought I was alone in this process! Grab eye with old heavy needlenose, hold in flame of gas stove (in my case) scrape off plastic bit. crush and solder covering with shrink wrap.
And I just thought I was OCD here...
Russellc
It would seem to me that you might have a situation where you have constant voltages at the gates of the mosfets and one or both of the hall sensors aren't operating correctly.
If both channels have the same mosfets, then both channels should behave the same.
Please don't tell me you bought your mosfets off ebay.
It wouldn't hurt to check every resistor value and every soldered joint on the board.
Last edited:
As some sissy builds are on my to-do list, I was looking for the solution to this Iq creep. Solution could be to put some NTC resistor in parallel with R15. Something like:
NTCASCWE3 Vishay NTC Thermistors | Mouser
Probably R15 at 1.2 K + 4.7 K NTC
NTCASCWE3 Vishay NTC Thermistors | Mouser
Probably R15 at 1.2 K + 4.7 K NTC
Thermistors might just be bandaiding a problem that shouldn't be there in the first place.
If you need thermistors then it kind of defeats the purpose of having the hall sensor in the first place.
I would work my butt off to find the root cause of the problem and fix it.
It's a shame to have to resort to thermistors. I don't even use them on devices like those specified here with constant voltage bias circuits.
If you need thermistors then it kind of defeats the purpose of having the hall sensor in the first place.
I would work my butt off to find the root cause of the problem and fix it.
It's a shame to have to resort to thermistors. I don't even use them on devices like those specified here with constant voltage bias circuits.
Last edited:
I have the upward creep of Iq in my SissySIT as well. I have traced it to two sources:
- temperature: as the temperature of the heatsinks and therefore the devices rises, the Iq creeps up. I have a 5U/400 case with its high thermal mass, and therefore the temperature-related "upcreep" of Iq continues for a few hours, and eventually levels out.
- Rails voltage: At my house, the wall AC voltage is rather variable (220-230V), and often rises in the evening. Rails voltage varies accordingly with wall AC voltage in ... Iq in the SissySIT is strongly dependent on rails voltage, and so also rises with rising rails.
Because the DC offset is dependent on Iq, I have tried to set my SissySIT to zero DC output offset at some intermediate rails voltage (DC offset zeroed for about 225V wall voltage in my case). That way, it usually only varies between -/+ 50 mV in the course of an evening.
The opto bias scheme has a harder time in keeping the bias current constant than, for example, in the M2 - this is because of the combination of an enhancement and a depletion device in the SissySIT, where the Delta Vgs (between N and P device) vs. Iq varies much less than in the case of N and P both enhancement devices, where the Vgs's nicely spread apart with rising Iq.
I've talked with Zen Mod about this at this year's BAF, and the solution we came up with at that time was to just bias the SissySIT more conservatively, so that it levels out where you want it to be.
I have tracked the total current draw of my SissySIT with an energy meter. The total draw for the amp levels out at around 230W, usually. (the label on the Y-axis is not correct - it should be W). Amp is not in constant use at the moment; the next time I open the amp, I will adjust bias down some more.
Regards, Claas
- temperature: as the temperature of the heatsinks and therefore the devices rises, the Iq creeps up. I have a 5U/400 case with its high thermal mass, and therefore the temperature-related "upcreep" of Iq continues for a few hours, and eventually levels out.
- Rails voltage: At my house, the wall AC voltage is rather variable (220-230V), and often rises in the evening. Rails voltage varies accordingly with wall AC voltage in ... Iq in the SissySIT is strongly dependent on rails voltage, and so also rises with rising rails.
Because the DC offset is dependent on Iq, I have tried to set my SissySIT to zero DC output offset at some intermediate rails voltage (DC offset zeroed for about 225V wall voltage in my case). That way, it usually only varies between -/+ 50 mV in the course of an evening.
The opto bias scheme has a harder time in keeping the bias current constant than, for example, in the M2 - this is because of the combination of an enhancement and a depletion device in the SissySIT, where the Delta Vgs (between N and P device) vs. Iq varies much less than in the case of N and P both enhancement devices, where the Vgs's nicely spread apart with rising Iq.
I've talked with Zen Mod about this at this year's BAF, and the solution we came up with at that time was to just bias the SissySIT more conservatively, so that it levels out where you want it to be
. I have tracked the total current draw of my SissySIT with an energy meter. The total draw for the amp levels out at around 230W, usually. (the label on the Y-axis is not correct - it should be W). Amp is not in constant use at the moment; the next time I open the amp, I will adjust bias down some more.
Regards, Claas
