That "general purpose" capacitor has a rating of 1A ripple current, but no ESR is specified.
That is a questionable part. The hum appears to have a period of about 10mS (100HZ).
It's either a poor filter capacitor, or the wiring is causing a ground loop (or both).
Do you have a schematic of this exact board and circuit?
That is a questionable part. The hum appears to have a period of about 10mS (100HZ).
It's either a poor filter capacitor, or the wiring is causing a ground loop (or both).
Do you have a schematic of this exact board and circuit?
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Recommended cap-substitute?
The board are Tubelab SSE, tubelab forum, SSE mentioned in the topic.
The board are Tubelab SSE, tubelab forum, SSE mentioned in the topic.
We don't know for sure if that's the source of the hum problem, but if you have 25mV-50mV on the secondary,
that will be audible.
You should have about 2.5V p-p ripple on the first B+ capacitor just after the rectifier,
and much less ripple on the second capacitor (after the series resistor).
If these ripple voltages are about right, I would instead look for a ground loop or a bad connection.
that will be audible.
You should have about 2.5V p-p ripple on the first B+ capacitor just after the rectifier,
and much less ripple on the second capacitor (after the series resistor).
If these ripple voltages are about right, I would instead look for a ground loop or a bad connection.
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The scope picture looks like a sine, not cap ripple -
but this may be just due to rect tube and CRC flter.
but this may be just due to rect tube and CRC flter.
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That's the waveform on the OT secondary winding. With ground loops.
it could look like anything.
it could look like anything.
Bad connection, bad tube, bad part, etc. There's always something.
Is the hum still there if you short the amplifier's audio inputs?
Is the hum still there if you short the amplifier's audio inputs?
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I asked to check with shorted input as you suggested and then at different pot positions.
However I do not think this will change the 100 Hz issue.
However I do not think this will change the 100 Hz issue.
Sorry, different timezones. Had to sleep.
A lot of good guessing, time to be constructive. Two tracks, how do I conclude or dispose the following theories?
Ground loop
- There are very few ground connections to the PCB. Primary, input signal and OPT/Speakers. Last thing I did before sleep was to disconnect incoming signal leads. No change. Removed ground from OPT/Speakers, No change.
- Is it safe to shorten the secondaries of the OPT?
- Still on my To Do are ground the transformer casings.
DC rectifying
- I will try to make an voltage splitter (100k/10k) and measure the B+ ripple, my Oscilloscope has a max rating of 50V.
- If C1/C2 are insufficient/wrong type/ specs. What type of capacitor should I replace them with. Is Is it better to replace or ad more capacitance?
A lot of good guessing, time to be constructive. Two tracks, how do I conclude or dispose the following theories?
Ground loop
- There are very few ground connections to the PCB. Primary, input signal and OPT/Speakers. Last thing I did before sleep was to disconnect incoming signal leads. No change. Removed ground from OPT/Speakers, No change.
- Is it safe to shorten the secondaries of the OPT?
- Still on my To Do are ground the transformer casings.
DC rectifying
- I will try to make an voltage splitter (100k/10k) and measure the B+ ripple, my Oscilloscope has a max rating of 50V.
- If C1/C2 are insufficient/wrong type/ specs. What type of capacitor should I replace them with. Is Is it better to replace or ad more capacitance?
Schematic is here : http://www.tubelab.com/images/AssemblyManualSimpleSE/Simple_SE_Amp_Sch_11-08.jpg
(we had no schematic so far).
Does the hum change (amplitude, waveform) if you short the rectifier switch connector ?
(we had no schematic so far).
Does the hum change (amplitude, waveform) if you short the rectifier switch connector ?
Pull out the 12AT7 tube. If you still have hum, it is coming from the power supply.
If that's the case try adding more capacitance in parallel with C2. Do not increase C1 as it makes life hard on the rectifier tube.
If that's the case try adding more capacitance in parallel with C2. Do not increase C1 as it makes life hard on the rectifier tube.
Thanks George
The power supply has been my main suspect from the beginning.
Pulled out the 12AT7, same humm. Plugged it in and added capacitors as the Optional Aux Cap drawn on the schematics.
Have to admit, it's a ugly setup, and dangerous as it is ground and B+(-R1 voltage dropp) in the open air. Could not find any 450V+ capacitors so I had to put them I series with 2pc 150kOhms resistors to distrobute the voltage.
Started small with 33uF, measured the ripple on OPT-sec and added more capacitors in steps until I ran out of them.
Result. Reducing ripple from 16mV to 8mV by adding 100uF. Still to much, the humm can be heard through the speakers but I'm closer than yesterday.
Have to order a capacitors better suited for the task, will this do the job? However, 100uF did not do the job, I guess I need a lot more than 100uF and thet can not be good for anything than the vendor.
Mundorf MLytic HV Power Cap · 2 axiale Wire 47 uF ±20%,
Also decided to order a choke, something from Hammond 193-series. Have looked at 193D, 193H and 193J. Any preferences? They cost about the same. It will be easier for fit a 193H in the casing.
The power supply has been my main suspect from the beginning.
Pulled out the 12AT7, same humm. Plugged it in and added capacitors as the Optional Aux Cap drawn on the schematics.
Have to admit, it's a ugly setup, and dangerous as it is ground and B+(-R1 voltage dropp) in the open air. Could not find any 450V+ capacitors so I had to put them I series with 2pc 150kOhms resistors to distrobute the voltage.
Started small with 33uF, measured the ripple on OPT-sec and added more capacitors in steps until I ran out of them.
Result. Reducing ripple from 16mV to 8mV by adding 100uF. Still to much, the humm can be heard through the speakers but I'm closer than yesterday.
Have to order a capacitors better suited for the task, will this do the job? However, 100uF did not do the job, I guess I need a lot more than 100uF and thet can not be good for anything than the vendor.
Mundorf MLytic HV Power Cap · 2 axiale Wire 47 uF ±20%,
Also decided to order a choke, something from Hammond 193-series. Have looked at 193D, 193H and 193J. Any preferences? They cost about the same. It will be easier for fit a 193H in the casing.
Attachments
Looking at that schematic, I don't like it's design at all.
But then again, I'm not fond of single-ended amps.
That's why push-pull designs can cancel hum issues easily, and provide the dynamic range for better high fidelity operation.
Don't get me wrong, I like simple, but there is a limit.
To each, their own. I see a lot of popular designs here, and elsewhere on the internet. I am not fond of many of them, but I don't post that opinion in the designers own forum.
I released the TSE design over 15 years ago and asked forum users what they wanted next. The response was overwhelmingly "something simpler" and something "build, plug, and play" without adjustments. That led to the SSE (Simple Single Ended) and SPP (Simple Push Pull) amp designs.
Of the amp boards that I sell, the SSE has been by far the most popular, and the SPP the least popular, so many do not share your opinion.
About 900 boards have been sold in 15 years.
In the first few years it was called the by the name that results when you use the word Simple followed by the common abbreviation for Single Ended. The board became so popular on the internet that I was served with legal papers requiring me to change the name and "never use it in print" again. It seems that there was a home theater product with a very similar name that was neither Simple or SE, but so may SSE builders were showing off their new SSE builds on the web that searching for their product brought up dozens of pictures of tube amps posted by proud SSE builders.
For me are the SSE the solution of a long living Dream. To build a Tube-amplifier!
It started 20-years ago, as a student could I not even afford the powersupply. But to read and try to understand how a tube-amp works are for free, the problem was only that the more I read the more I understood that there are easier to fail than to make a success. I'm no electrician, my field are material science. I do know the basics as Ohms law etc, not more.
I'm the proof that a Tubelab SSE can be build by anyone who knows how to read, order parts from a published list and use solder iron together with basic tools. I played it for hours today with a big smile while I was cleaning the house and doing all the boaring stuff as sorting cloth etc that has to be done.
My amp are at this state not perfect, the humms annoy me. However am I confident that this forum will guide me to an acceptable level. There are some final tweaks to be done....
A big thanks to George for your dedication to Tubelab and to all people in this forum trying help me.
It started 20-years ago, as a student could I not even afford the powersupply. But to read and try to understand how a tube-amp works are for free, the problem was only that the more I read the more I understood that there are easier to fail than to make a success. I'm no electrician, my field are material science. I do know the basics as Ohms law etc, not more.
I'm the proof that a Tubelab SSE can be build by anyone who knows how to read, order parts from a published list and use solder iron together with basic tools. I played it for hours today with a big smile while I was cleaning the house and doing all the boaring stuff as sorting cloth etc that has to be done.
My amp are at this state not perfect, the humms annoy me. However am I confident that this forum will guide me to an acceptable level. There are some final tweaks to be done....
A big thanks to George for your dedication to Tubelab and to all people in this forum trying help me.
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