Since I had the signal generator and oscilloscope hooked up, I also did a sine frequency sweep. Again the yellow trace was the signal generator and the blue was the amplifier output.
The base line was set at 1kHz where a 4.01Vrms input signal resulted in a 3.68Vrms output signal into 8 Ohm.
10 Hz: input= 4.00Vrms, output= 3.55Vrms, 10Hz/1kHz= 3.55Vrms/3.68Vrms= -0.31dB
20 kHz input= 4.01Vrms, output= 3.60Vrms, 20kHz/1kHz= 3.60Vrms/3.68Vrms= -0.19dB
100kHz input= 3.99Vrms, output= 3.54Vrms, 100kHz/1kHz= 3.54Vrms/3.68Vrms= -0.34dB
200kHz input= 4.00Vrms, output= 3.39Vrms, 200kHz/1kHz= 3.39Vrms/3.68Vrms= -0.71dB
500kHz input= 4.00Vrms, output= 2.87Vrms, 500kHz/1kHz= 2.87Vrms/3.68Vrms= -2.16dB
The base line was set at 1kHz where a 4.01Vrms input signal resulted in a 3.68Vrms output signal into 8 Ohm.
10 Hz: input= 4.00Vrms, output= 3.55Vrms, 10Hz/1kHz= 3.55Vrms/3.68Vrms= -0.31dB
20 kHz input= 4.01Vrms, output= 3.60Vrms, 20kHz/1kHz= 3.60Vrms/3.68Vrms= -0.19dB
100kHz input= 3.99Vrms, output= 3.54Vrms, 100kHz/1kHz= 3.54Vrms/3.68Vrms= -0.34dB
200kHz input= 4.00Vrms, output= 3.39Vrms, 200kHz/1kHz= 3.39Vrms/3.68Vrms= -0.71dB
500kHz input= 4.00Vrms, output= 2.87Vrms, 500kHz/1kHz= 2.87Vrms/3.68Vrms= -2.16dB
Hi Ben Mah,
what are these areas near the SIT drain connection and the GND connection, and what are they for?
Are these holes to reduce heat dissipation when soldering to GND?
😕 Thanks
what are these areas near the SIT drain connection and the GND connection, and what are they for?
Are these holes to reduce heat dissipation when soldering to GND?
😕 Thanks
Those are vias which are plated through holes to the ground plane on the bottom side of the board. There is also a copper fill surrounding the vias at the top side of the board. The intent was to provide a good connection of the ground wires to the ground plane.
Aah, now I get it.
The cables are soldered from above after the circuit board is installed.
I'm still learning more.
The cables are soldered from above after the circuit board is installed.
I'm still learning more.
The wires can be connected from the top or bottom - it does not matter.
Typically when there is a pad connected to a copper pour (ground plane in this case), the pad is connected intermittently to the copper pour with copper "spokes". That is to minimize the heatsink action of the copper pour so that the pad may be easily heated to soldering temperature. The down side is that the pad has less electrical connection to the copper pour. So surrounding the topside pad with copper and vias to the bottom ground plane beefs up electrical connection to the ground plane.
Some progress has been made on the left channel. The power supply has been converted to V-, and I have received the left channel pcb.
I wanted separate left and right channel pcbs, and the left channel pcb is essentially a mirror image of the right channel with only minor changes. In the past I had given a lot of thought and also done internet searches trying to find a way to easily mirror the pcb, but without success. So I manually laid out the foot prints and traces in a mirror image. However this time I finally saw the light. After only a short time pondering the issue, I realized that all I had to do was go into the properties of the footprints, traces, added text, etc. and change the layer from "front" to "back" and vice versa. It still took a bit of work but it was easy work.
Pictures of progress and left channel pcb:
Typically when there is a pad connected to a copper pour (ground plane in this case), the pad is connected intermittently to the copper pour with copper "spokes". That is to minimize the heatsink action of the copper pour so that the pad may be easily heated to soldering temperature. The down side is that the pad has less electrical connection to the copper pour. So surrounding the topside pad with copper and vias to the bottom ground plane beefs up electrical connection to the ground plane.
Some progress has been made on the left channel. The power supply has been converted to V-, and I have received the left channel pcb.
I wanted separate left and right channel pcbs, and the left channel pcb is essentially a mirror image of the right channel with only minor changes. In the past I had given a lot of thought and also done internet searches trying to find a way to easily mirror the pcb, but without success. So I manually laid out the foot prints and traces in a mirror image. However this time I finally saw the light. After only a short time pondering the issue, I realized that all I had to do was go into the properties of the footprints, traces, added text, etc. and change the layer from "front" to "back" and vice versa. It still took a bit of work but it was easy work.
Pictures of progress and left channel pcb:
Is there any difference essentially between Ben Mah's version and triode_al's version in post # 329 of the First Watt SIT5 thread pasted here for ready reference? Thanks all.
If you compare the two schematics you can see that there are many differences.
From my perspective Nelson gave us a peek into his SIT-5 and gave us a new look at the output stage of a SIT follower amplifier. Being an avid but amateur diyer I decided to explore the output stage concept by trial and error. This is a hobby for me so time spent is irrelevant. Many hours have been spent reading forum posts, doing LTSpice simulations, putting together pcbs using KiCad, building the amp, testing the amp, etc.
Since there is no detailed information about the SIT-5 circuit, the goal was not to exactly replicate it. I just wanted to have a functional output stage in the style of the SIT-5 output stage, and also to have the output stage measure and sound good. The Tokin SITs are great audio devices and they can be made to sound good in many, many ways. So even in the style of the SIT-5, there are many combinations of components and component values that will probably work wonderfully. My version is just one of the many. The output stage is simple enough that different operating points (power supply voltage, Vds, and Iq) can be explored, and different combinations of the source and mosfet output resistors can also be explored.
So much fun can be had. DIY is not just soldering parts to boards and assembling the amplifier. 🤓
From my perspective Nelson gave us a peek into his SIT-5 and gave us a new look at the output stage of a SIT follower amplifier. Being an avid but amateur diyer I decided to explore the output stage concept by trial and error. This is a hobby for me so time spent is irrelevant. Many hours have been spent reading forum posts, doing LTSpice simulations, putting together pcbs using KiCad, building the amp, testing the amp, etc.
Since there is no detailed information about the SIT-5 circuit, the goal was not to exactly replicate it. I just wanted to have a functional output stage in the style of the SIT-5 output stage, and also to have the output stage measure and sound good. The Tokin SITs are great audio devices and they can be made to sound good in many, many ways. So even in the style of the SIT-5, there are many combinations of components and component values that will probably work wonderfully. My version is just one of the many. The output stage is simple enough that different operating points (power supply voltage, Vds, and Iq) can be explored, and different combinations of the source and mosfet output resistors can also be explored.
So much fun can be had. DIY is not just soldering parts to boards and assembling the amplifier. 🤓
Thank you for your detailed and hearty response Ben Mah. I have a pair of Tokin THF51-S SITs and Heatsinks which can handle your 47 volt supply version. I am very interested. But I was equally interested earlier in Zen Mod's SissySIT.
Let me see where the heart leads. Thanks a ton again.
Let me see where the heart leads. Thanks a ton again.
khoasonphong, Have you built your SIT-5 topology amp yet? Any listening impressions? I am curious as to your choice of resistors at the SIT-mosfet sources and mosfet output.
The left channel is done and both channels are now playing. I am running 1 Ohm source and 1.5 Ohm at mosfet output and I am enjoying the sound. I was listening to my choke loaded 2SK180 single ended follower before putting this new amp into the system and the sound of the new amp is very similar. It has the Tokin SIT follower sound with clear highs and the impression of realism. Perhaps this new amp has a touch more, so I am not complaining - very happy so far. 🤓
I haven't finished it yet Ben, Here is my practice: I plan not put C6 in the first time. I will series a sense resistor 0.1R for each capacitor to get AC voltage value. The start point when H3 get dominant (~8W) , R10 will be change to get for H2 back.
I think this way to study how NP set contribute Mosfet value.
I think this way to study how NP set contribute Mosfet value.
We are all wondering and guessing.
The combination that I have chosen measures well and I have no complaints about the sound. In fact I am quite happy with the sound so I will leave it alone and enjoy the music. 🤓
The combination that I have chosen measures well and I have no complaints about the sound. In fact I am quite happy with the sound so I will leave it alone and enjoy the music. 🤓
yah think build measure listen and... repeat 😏 .
Can I know your opinion about CCS - SIT Amp , why don't have many commercial amplifier build simple that like L'Amp ? I though it good also, simplest, ... . I have 4 choke 193V , but I may do all to get answers.
Can I know your opinion about CCS - SIT Amp , why don't have many commercial amplifier build simple that like L'Amp ? I though it good also, simplest, ... . I have 4 choke 193V , but I may do all to get answers.
There are First Watt CCS amplifiers that are CCS loaded.
Other manufacturers may not build CCS amplifiers since they are inefficient, both in power and cost. Single ended and Class A are low power, consume a large amount of power, and dissipate a large amount of heat. So high cost to build commercially for a small amount of power output. For the diyer, cost is less of an issue.
I have a pair of 193V choke loaded SIT (2SK180) follower monoblock amplifiers. They sound very good. They are in the seasonal amplifier rotation.
Other manufacturers may not build CCS amplifiers since they are inefficient, both in power and cost. Single ended and Class A are low power, consume a large amount of power, and dissipate a large amount of heat. So high cost to build commercially for a small amount of power output. For the diyer, cost is less of an issue.
I have a pair of 193V choke loaded SIT (2SK180) follower monoblock amplifiers. They sound very good. They are in the seasonal amplifier rotation.
Ben Mah, you wrote this - "
It has the Tokin SIT follower sound with clear highs and the impression of realism. Perhaps this new amp has a touch more, so I am not complaining - very happy so far."
Have your initial impressions been consolidated on continued listening and burn in of your implementation of the SIT-5? Thanks.
It has the Tokin SIT follower sound with clear highs and the impression of realism. Perhaps this new amp has a touch more, so I am not complaining - very happy so far."
Have your initial impressions been consolidated on continued listening and burn in of your implementation of the SIT-5? Thanks.
Yes.
My impressiions have not changed. I am very happy with the sound.
If you would like to build this and listen for yourself, Gerber files are free for the asking.
My impressiions have not changed. I am very happy with the sound.
If you would like to build this and listen for yourself, Gerber files are free for the asking.
Are you saying you are using four 193Vs in each amplifier? I would assume in series parallel? I have long wondered how this works. Do I understand this correctly?
I would love to know.
Thanks,