Thanks again mike567. Would not be the first time a project stalls because I am obsessing over something that in the big picture does not matter much. I will move on and finish up the box.
I ended up taking out the soft start board for now, turns out it does have an issue that needs to be fixed. I replaced it with a CL-90 so I could give the SSE a try in the living room before stripping it down to finish the chassis. I set it up in triode mode with no feedback. Listened to it for about 4 hours. Very enjoyable. It does have something special and I think in many ways it matches my speakers well. However I must not be much of an audiophile because I did not find it lacking in volume nor in it's ability to handle my music. Sounded good playing Billie Holiday, sounded good playing Kraftwerk, sounded good playing the Cramps and everything else across the spectrum.
So now time to take it apart and finish up the chassis.
So now time to take it apart and finish up the chassis.
Looking at the wiring diagrams again I think the answer is high voltage is going through the UL switch but not the CFB switch. Correct?
Grounding question. I will have 2 RCA inputs going to a switch, then to volume pot, then split into two, one to the PCB and another wired as a subwoofer out. Looking at the wiring diagrams on the Tubelab site a ground is taken off the RCA input going into the volume control. Do I need to worry about grounding the output RCA?
One other question. Is it worthwhile to put a CL-60 current limiter between the RCA input and ground? I see these used in other amps as a "ground lifter" to help reduce hum but still provide for grounding the inputs.
One other question. Is it worthwhile to put a CL-60 current limiter between the RCA input and ground? I see these used in other amps as a "ground lifter" to help reduce hum but still provide for grounding the inputs.
Listened to the SSE for over 12hrs yesterday. No smoke only music so I think everything is ok. Sound is wonderful, hard to believe my little speakers are sounding that good. Also no issues with volume in triode mode. Since I don't have the pot installed yet I am using the software volume control in my streamer. With it at 30% my wife said she could hear it when she pulled up to the house at night. Right now I have the volume set at 2% for background music during the day.
Tried a different DAC and streamer same result. Why I notice it when playing flac and not anything else I can't say but that is when I hear the buzz. Sounds like a 120Hz buzz. I have one input, speaker out, toroid, soft start board grounding to the post that connects the pcb back left corner. One thing I was going to change is I have the inlet grounding to the soft start board then to the post. Pic in the previous post you can see where everything is being grounded.
I tried another type of grounding scheme. This time I attached the inlet ground to chassis then everything else to a star ground attached to a CL60 to the chassis ground. Please see the drawing attached. 1 is the original 2 is the star ground with CL60. Are both these valid, would one be preferred?
I still get hum but I am now thinking it is not the SSE. As a comparison I hooked up the same DAC straight to my current amp, a Mod86 rather than through a pre. Same buzz using the software volume control. I then hooked it back as normal and turned the pre volume to max then again used the software volume, same buzz.
I still get hum but I am now thinking it is not the SSE. As a comparison I hooked up the same DAC straight to my current amp, a Mod86 rather than through a pre. Same buzz using the software volume control. I then hooked it back as normal and turned the pre volume to max then again used the software volume, same buzz.
Attachments
Is it possible your FLAC files are corrupted? Have you tried converting one of the FLAC files to another format?
I have not tried it but I will, good idea thanks. This has all been a learning experience for me.
Overall update. After getting some advice on how to properly ground the amp using a CL-60 between the signal ground and chassis ground I now have it setup so IEC and soft start ground to a single point on the chassis, the toroidal, speaker out, and pcb ground together and attach to the chassis ground point through the CL-60.
I have also added a 10k Alps volume pot and a source selector switch.
If I plug in the amp and turn the volume all the way up with nothing plugged in it is silent. If I plug in my sources and turn the volume all the way up I hear some hum through the speakers, if I turn it down to listening levels I only hear the faintest of hum. Honestly if I wasn't so focused on it I don't know if I would notice and am not sure if it is worse than it was with my other amp.
Found that there is a bug in the software volume control in the streamer software I am using. If I turn off the software volume control then no more distortion playing FLAC files. Looks like I will need to wait for the next update for a fix. Good news is with that disabled I don't hear any distortion/buzz/hum coming from the speakers with my ear right up next to them.
The only noise now related to the SSE is the toroidal. If I put my ear right up next to it I can hear a buzz. It is quiet enough that if the toroidal was in a chassis I don't think I could hear it. I have heard this sound before but then it seemed to go away so I may try some different outlets and see if that helps.
The only noise now related to the SSE is the toroidal. If I put my ear right up next to it I can hear a buzz. It is quiet enough that if the toroidal was in a chassis I don't think I could hear it. I have heard this sound before but then it seemed to go away so I may try some different outlets and see if that helps.
I have a Hammond made Allied transformer in my SSE that buzzed. The buzz was rather low in the mornings and loudest in late afternoon, and also was worse in the summer than in winter. The loudness of the transformer buzz seemed to correlate with typical Florida power demand.
I measured the THD on our power lines (don't try this unless you are sure of what you are doing) and found that it was in the 3% range when the transformer was quietest, and 6 to 9% when the transformer was loudest. Signs of obvious transformer saturation could be seen on the scope during evening cooking, TV watching, air conditioner still at 95% duty cycle time.
If you are in a high population density location, you may have a similar issue. The typical US house has a 240 volt CT transformer feeding it along with several other houses (9 in our Florida location). Once inside the house, about half the outlets are fed from one side of the CT, with the other half on the other side of the CT. 240 volt appliances like the stove, AC, and water heater get the whole 240 volt winding.
One half of the pole transformer may have slightly less THD than the other, but if the transformer is hitting saturation, all outlets will be affected.
There are many sources of local noise and distortion pollution on the power lines. This will raise the noise environment in the home, but rarely causes transformer buzz since most of this noise is high frequency. The worst offenders here are CFL and LED light bulbs, computers, and flat screen TV sets. The crud emitted by these things fun from the 15 KHz region well into the tens of MHz. I have seen a drop in THD measurements on an amp I'm bench testing of a few tenths of a percent just by turning all the lights off in the house. many modern "smart TV" sets emit crud even when turned off. I have to unplug the 10 year old Sony that is upstairs to kill the spur that it makes in the 146 MHz ham radio band.
This describes my house almost exactly. High density area, all CFL or LED lights, AC, multiple computers, a flat screen TV right next to the amp etc. In fact the buzzing of the ceiling lights is louder than the toroidal buzzing. I often turn them off when listening to music at lower volume. We are also in peak power usage season here including warnings to reduce usage last week from the power company.
Quiet afternoon in the neighborhood, moderate temps and I don't hear any A/C units running. Went around and turned off everything in the home. Hit the power button on the SSE and no toroidal buzzing. Supports the hypothesis that it is noise on the power lines caused by some appliance or load.
At this point the amp is quiet. With my ear as close to the speaker as I can get no buzz or hum. With my ear as close to the amp as I can get no buzz or hum.
Time to take it out of the system and finish up the aesthetics.
At this point the amp is quiet. With my ear as close to the speaker as I can get no buzz or hum. With my ear as close to the amp as I can get no buzz or hum.
Time to take it out of the system and finish up the aesthetics.
Finished up the SSE, at least for now. Guess I am officially a tube amp owner now. What a fun journey! Big thanks to George for sharing his design and wisdom and everyone else on here for the help. Now to listen to some music.
