The SIT3X folded-cascode FE has resistor values for 44V rails. What rail voltages do you have with the Burning amp? Some resistor values would change for different rail voltages.
Have you tried the BA3-FE described in http://www.firstwatt.com/pdf/art_ba_3.pdf? I attempted to adapt it to the SIT3X but couldn't get low enough output impedance to handle the Tokin 2SK182ES. I suppose I could have added the source follower stage to the BA3-FE like I did with the folded-cascode FE.
This SIT3X has much more output power than I need: THD<.5% at 50W and the unit weights > 50 pounds, mosly due the the transformer and heatsinks.
I would like design a simpler SIT3X which would have the power supply and heatsink requirements of typical FirstWatt amps. Unfortunately, the design requires a lower capacitance (and lower power) SIT, such as Papa's the unobtanium SemiSouth SIT-1.
I would like design a simpler SIT3X which would have the power supply and heatsink requirements of typical FirstWatt amps. Unfortunately, the design requires a lower capacitance (and lower power) SIT, such as Papa's the unobtanium SemiSouth SIT-1.
Yes, got the boards, installed all the goodies, then smoked the outputs applying reverse voltage by accident when testing on the bench.
Haven't gotten around to fixing it and started reading this, saw that you weren't thrilled with that FE and so here we are.
Rush
Can this design from Broskie be a lower powered option ?
See past half page chapter "Depletion-Mode MOSFETs"
The output stage is set at +-20vdc
the input stage is +-40vdc, but that could easily be done with a voltage doubler since the input stage requires only a few ma.
What is your target temp of heatsink? Due to its larger size, I guess θj-c of Tokin is much lower than the other FETs, while I have not seen any official data.
The output FET bias current is approx 1.8A with 45V rails. I am using a pair of Noctua NF-F12 fans which run at 1500RPM at full voltage. With 100R resistors in series with the fans I am seeing heatsink temperatures around 40C. I could probably switch to using NF-S12A ULN 800 RPM fans and keep the temperature below 50C.
I am about 200 miles south of Portland, near Roseburg Oregon. That is a significant distance from the north end of Seattle.
That's what I was expecting. About a six hour drive.
Back in the late 80s, I had a long commute down to Tigard – once a week for six weeks in a row to work on a custom gate array project. The company I was with at the time was too small to afford the high end workstations and software to finish the job locally. I know the road between Portland and Seattle quite well. I also lived in Corvallis for a few years before eventually relocating to the Seattle area. I still drive down to Santa Cruz every year for Xmas, so time on the road is just another form of meditation.
Back in the late 80s, I had a long commute down to Tigard – once a week for six weeks in a row to work on a custom gate array project. The company I was with at the time was too small to afford the high end workstations and software to finish the job locally. I know the road between Portland and Seattle quite well. I also lived in Corvallis for a few years before eventually relocating to the Seattle area. I still drive down to Santa Cruz every year for Xmas, so time on the road is just another form of meditation.
Those fans should be virtually silent. 🙂
Well, I think I also will target 50C, thank you.
Here is an image showing the fans in my 2SK182ES based mu-follower build (similar to a SIT-2). The SIT3X uses the same scheme. The heatsinks are HeatSinkUSA 10.080" Wide x 7" long 10.080" Wide Extruded Aluminum Heatsink - HeatsinkUSA.
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I did not mention it previously, but the SIT3X should drive about 100W into a 4R load with <1%THD and no waveform clipping.
After two days of listening to the SIT3X and occasional A/B comparisons to my ZD25 I can find no faults with the SIT3X. My components:
- FLAC music files.
- Behringer DEQ2494 run digital in and out, essentially flat equalization.
- Buffalo III-SE DAC
- SIT3X / ZD25 with remote switch.
- Kairos speakers http://meniscus.lightningbasehosted.com/wp-content/uploads/2016/02/Kairos-Write-up.pdf
