Hi,
I’m not at home until couple couple of days. I can give you dimension a little later.
Here you go Reima! Translate to inches if you will.
Dimensions, interior:
H=190mm
W=240mm
D=360mm
Sadly my other channel is burnt cause broken regulator 🙁
Dimensions, interior:
H=190mm
W=240mm
D=360mm
Sadly my other channel is burnt cause broken regulator 🙁
SissySIT Left Channel
Finally received my Cinemag transformers.
Mounted everything on heatsinks, checked for no continuity between heatsinks and Drain of SITs and MOSFETs. OK
Left:
2SK180 SIT VGS -4.04 at 2 amps. (I know this one is iffy)
MOSFET IRF9240 VGS -4.66 at 2 amps.
Right:
2SK180 SIT VGS 3.83 at 2 amps.
MOSFET IRF9240 VGS -4.63 at 2 amps.
1000 VA Transformer has 4 windings for +/- Right and Left.
Hooked up the Left channel only, right channel power supply is hanging in the breeze.
Right channel has own cap bank located under Left cap bank.
AMP is plugged into Variac, turning to only to 30 VAC, rails at +/- 7 VDC, 0.06 across 0.1 ohm resistor in CRC power supply. See photo
2.663 volts on output :-( bad)
Checked gate on SIT -.557
Checked gate on MOSFET -.806
So being the fearless Amp builder, I went to full tilt 120 volts for 30 seconds at a time.
At full 120 VAC, +/- 27 VDC rails, .271 across 0.1 ohm CRC resistor.
1.9 volts on output :-( still bad)
Checked gate on SIT -2.18
Checked gate on MOSFET -2.69
If I turn P1L, Voltage across CRC 0.1 ohm resistor goes up.
Turning P2L I was able to set offset to zero and checking gates: See photo
0.002 volts at output
Checked gate on SIT -4.27
Checked gate on MOSFET -4.63
Now I have 0.290 across 0.1 ohm CRC resistor.
What is a mother to do?
How can I reduce current when P1L is at minimum.
Is this problem because of not enough Vgs voltage difference between SIT and MOSFET? 0.36 VDC difference.
Looking forward to your help.
Rush
Finally received my Cinemag transformers.
Mounted everything on heatsinks, checked for no continuity between heatsinks and Drain of SITs and MOSFETs. OK
Left:
2SK180 SIT VGS -4.04 at 2 amps. (I know this one is iffy)
MOSFET IRF9240 VGS -4.66 at 2 amps.
Right:
2SK180 SIT VGS 3.83 at 2 amps.
MOSFET IRF9240 VGS -4.63 at 2 amps.
1000 VA Transformer has 4 windings for +/- Right and Left.
Hooked up the Left channel only, right channel power supply is hanging in the breeze.
Right channel has own cap bank located under Left cap bank.
AMP is plugged into Variac, turning to only to 30 VAC, rails at +/- 7 VDC, 0.06 across 0.1 ohm resistor in CRC power supply. See photo
2.663 volts on output :-( bad)
Checked gate on SIT -.557
Checked gate on MOSFET -.806
So being the fearless Amp builder, I went to full tilt 120 volts for 30 seconds at a time.
At full 120 VAC, +/- 27 VDC rails, .271 across 0.1 ohm CRC resistor.
1.9 volts on output :-( still bad)
Checked gate on SIT -2.18
Checked gate on MOSFET -2.69
If I turn P1L, Voltage across CRC 0.1 ohm resistor goes up.
Turning P2L I was able to set offset to zero and checking gates: See photo
0.002 volts at output
Checked gate on SIT -4.27
Checked gate on MOSFET -4.63
Now I have 0.290 across 0.1 ohm CRC resistor.
What is a mother to do?
How can I reduce current when P1L is at minimum.
Is this problem because of not enough Vgs voltage difference between SIT and MOSFET? 0.36 VDC difference.
Looking forward to your help.
Rush
Attachments
oh boy , 27Vdc rail is tricky detail
what's happening when you dial Variac down , to have 22V5dc rails ?
what's happening when you dial Variac down , to have 22V5dc rails ?
Thanks ZM,
Turned the rails down to 22.5 +/- VDC
Had to reset P2L (it was 0.6 VDC at lower rails). I was able to set offset to zero and checking gates: See photo
0.003 volts at output
Checked gate on SIT -4.20
Checked gate on MOSFET -4.55
Now I have 0.199 across 0.1 ohm CRC resistor.
Still turning P1L increases current.
Rush
Attachments
1A99 is good figure
problems you faced are there as combination of highish SIT Ugs and high rails
luckily , you also have mosfets with highish Ugs
now , you "only" need to find a way to have rails in range I prescribed , if not because of fact that everything is optimized there , then to keep mosfet dissipation in still sane range
I can't see any other way than to change Donut , for one having 18Vac secondaries
edit: now you clearly see what is what's called "resistive nature of SIT" ........ so changing rails voltage is resulting in huge differences in Iq with fixed Ugs ..... and what's really tricky is still having enough of voltage window for optocoupler
problems you faced are there as combination of highish SIT Ugs and high rails
luckily , you also have mosfets with highish Ugs
now , you "only" need to find a way to have rails in range I prescribed , if not because of fact that everything is optimized there , then to keep mosfet dissipation in still sane range
I can't see any other way than to change Donut , for one having 18Vac secondaries
edit: now you clearly see what is what's called "resistive nature of SIT" ........ so changing rails voltage is resulting in huge differences in Iq with fixed Ugs ..... and what's really tricky is still having enough of voltage window for optocoupler
Last edited:
With babysitter, sure! 🙂
More work, but now I will have "special" regulated SissySIT, not so sissy anymore!
Rush
Boyz
I'm digging through emails and PMs , catching up with packing etc.
Gimme few days and will reply to everyone
Besides - Summer time ...... if I already have no time to chill , trying to do things in chillin' tempo
I'm digging through emails and PMs , catching up with packing etc.
Gimme few days and will reply to everyone
Besides - Summer time ...... if I already have no time to chill , trying to do things in chillin' tempo
ZM<
Or I could double up on MOSFETs, with small source resistors, like 0.2 ohm?
I happen to have two matching pairs: 4.66/4.65
If I have enough heatsink, and I think I do, which would be better?
Running 2.7 amps at 27 VDC, double MOSFETs or Cap-multiplier at 22.5 VDC and 2 amps?
Rush
I would go for Cap multi
Sissy is more like Ferrari than John Deer , better to keep it that way
Sissy is more like Ferrari than John Deer , better to keep it that way
ZM,
I did go with the cap-multiplier, one for each channel. Thing is, that now that both channels are pulling juice, the raw supply rails are 25 VDC, not 27 VDC. I could have gone without Cap-multi after all.
The Cap-multiplier is dropping 4.5 VDC, so I am running 20.5 or so VDC per channel. I had to use the P1 to move the current draw up to 1.8 amps.
Having some offset drift with cover on takes about 3 hours before the offset settles down to +/- 0.010 VDC. Thats after I chase it every hour resetting it.
Rush
PS, pictures are of the Baby Sister, my repurposed case and the amp with Cap-multipliers installed.
Attachments
Soooo... How does it sound?
I have been burning in the amp for about 15 hours total.
Had a "golden ear" friend over on Friday Night to listen to the new amp.
He and I agreed, overall better than my F5 with Toshiba outputs. It has a very well defined detail, with precise imaging. Great tonal balance.
I am using Nelson's design Korg preamp set to lowest distortion setting.
My speakers are Magenapan 1.6QR with Peter Gunn's crossover design. Very carefully placed in my 10.5 foot wide by 14.5 foot long room with 10 foot high ceiling.
I have a near sitting position about 5.5 feet in front of the speakers, which are 3.5 feet off front wall, 1.5 feet from side walls. This position works well. I have plenty of power for these 86 DB speakers.
I am very impressed, Thank you ZM.
I may have to order another set of boards to bi-amp the maggies!
Rush
I have been burning in the amp for about 15 hours total.
Had a "golden ear" friend over on Friday Night to listen to the new amp.
He and I agreed, overall better than my F5 with Toshiba outputs. It has a very well defined detail, with precise imaging. Great tonal balance.
I am using Nelson's design Korg preamp set to lowest distortion setting.
My speakers are Magenapan 1.6QR with Peter Gunn's crossover design. Very carefully placed in my 10.5 foot wide by 14.5 foot long room with 10 foot high ceiling.
I have a near sitting position about 5.5 feet in front of the speakers, which are 3.5 feet off front wall, 1.5 feet from side walls. This position works well. I have plenty of power for these 86 DB speakers.
I am very impressed, Thank you ZM.
I may have to order another set of boards to bi-amp the maggies!
Rush
