today after work i had a chance to listen the amp some more. The hum is getting better by itself, now i can hear it only with my ear to the speaker and my speakers are rated at 103dB/1W. I adjusted the HT ripple pot, in my case there is no audible difference when adjusting from one end to the other end of the pot range. I think i will leave the amp alone for a while and see what happens since the hum seems to get better with some burn in. Not sure what is the explanation for this but I take it since it goes in the right direction.
This amp has more definition and detail than the amp i am replacing (Chinese version of a push-pull vacuum tubes). For sure I am quite happy with the outcome.
This amp has more definition and detail than the amp i am replacing (Chinese version of a push-pull vacuum tubes). For sure I am quite happy with the outcome.
Sometimes it takes a few hours for power supply capacitors to be fully formed after sitting on the shelf. I have also experienced hum that quickly dies away with more listening.
I think the Toroid shields could go to the chassis connection (not the star ground if it is lifted). They are just there for safety, and that is the surest route to guarantee the fuse will blow in the case of an issue.
I think the Toroid shields could go to the chassis connection (not the star ground if it is lifted). They are just there for safety, and that is the surest route to guarantee the fuse will blow in the case of an issue.
Just use the search function and you will find enough information!
https://www.diyaudio.com/community/search/1554145/?q=STU9HN65M2&o=relevance
https://www.diyaudio.com/community/search/1554145/?q=STU9HN65M2&o=relevance
I was able to finish completely the amp and now I am enjoying listening to it.
I but back the original values for R206, R207. 1K makes the start up hum last longer, 100R make the hum at the power up last just few seconds.
R323, R423 initially had them at 33K, i put them back at 22K. I am not absolutely sure but I think 33K made the bass a bit more strong, if this makes sense.
I but back the original values for R206, R207. 1K makes the start up hum last longer, 100R make the hum at the power up last just few seconds.
R323, R423 initially had them at 33K, i put them back at 22K. I am not absolutely sure but I think 33K made the bass a bit more strong, if this makes sense.
That black box is isolation transformer splitter I use to feed my subwoofer, this is a temporary solution until I build my line amp which has a subwoofer line out.
The case link I got from @tbaashus.
aliexpress supplier Search for W430 H80 D330
You will find 2 versions, one with screws visible at the top and one slightly more expensive with the screws hidden.
Be aware the AL sides is very thick and the regular length RCA thread is too short.
The case link I got from @tbaashus.
aliexpress supplier Search for W430 H80 D330
You will find 2 versions, one with screws visible at the top and one slightly more expensive with the screws hidden.
Be aware the AL sides is very thick and the regular length RCA thread is too short.
Another nice case on aliexpress is W380 H89 D320
I used this case for another Yamamoto DAC project and it is a very nice case, it is brushed AL not anodized.
i need some advice. I am still having a noticeable hum, it is mostly 60Hz. The hum dinger pot doesnt seem to do anything. Granted my speakers are rated at 103dB which can make the hum more noticeable, I am not planning to change these speakers, I put way to much work in those, they are Klipsch Belle replica.
Perhaps changing the grounding scheme, At this time I have the output transformer output lead 0 connected to the speaker ground post and to the GNDA on the connector on the PCB
I am thinking of connecting the speaker ground post to the AC ground and not to the GNDA, would be this a good idea? I have a cheaper Chinese amp which has this ground scheme.
For input I use a coaxial cable, should I change it to twisted pair of solid wire?
Perhaps changing the grounding scheme, At this time I have the output transformer output lead 0 connected to the speaker ground post and to the GNDA on the connector on the PCB
I am thinking of connecting the speaker ground post to the AC ground and not to the GNDA, would be this a good idea? I have a cheaper Chinese amp which has this ground scheme.
For input I use a coaxial cable, should I change it to twisted pair of solid wire?
Perhaps it’s not heater-related hum. I never adjusted mine from the factory-set centre position… Couldn’t hear any 100/120Hz hum through the speakers.
On grounding - there is a single Earth -> Chassis connection and a single Chassis -> Audio Ground connection. The intent is to avoid ground loops. Are you sure the speaker posts and RCA connector posts are properly isolated from the chassis? As you describe, you have it right - I don’t think any alternative would improve anything. It’s electrically equivalent, I think, apart from the ground loop breaker that would be inserted between speaker return and the rest of the circuit - which is not what you want.
Are you sure it isn’t mechanical hum? Perhaps the PT isn’t tightened down?
