I read in the Tubelab TSE power supply Design:
Provisions are made for an external bypass capacitor from the B+ side of the output transformer to the output tube filament (ground). An oil cap or a Solen Fast Cap may improve the sound.
Why is it a god idea and what size/value ought the bypass capacitor to have?
I hope fore some response. I have tried to find info. about this question in the forum, but "no cigar"
I am uncertain what to do, so thanks for the help!
Michael 🙂
Provisions are made for an external bypass capacitor from the B+ side of the output transformer to the output tube filament (ground). An oil cap or a Solen Fast Cap may improve the sound.
Why is it a god idea and what size/value ought the bypass capacitor to have?
I hope fore some response. I have tried to find info. about this question in the forum, but "no cigar"
I am uncertain what to do, so thanks for the help!
Michael 🙂
Did you see this section from the Tubelab site?
Its almost at the bottom of this page:
Tubes and Applications | Tubelab
Modifications to Improve the Sound
The board is designed to be built using a capacitor input filter with a choke or a resistor in between the two capacitors. If a choke is desired it may be connected in place of R4. This is a HIGHLY recommended modification. Many early users found that a choke was needed when using high efficiency speakers. I have since added a choke to my amplifiers, and found improved bass and dynamics even though I had no hum. People have asked " what kind of choke do I use?" I use the Triad C-14X because it has 150 ohms of DC resistance. It is UGLY, so you will want to hide it under the chassis. If you need a better looking choke, use one that has nearly 150 ohms of resistance, and has the same or higher current rating as the power transformer. The Hammond 193J will work, but you will gain a few volts of B+ because it is only 82 ohms. Remove R4 and connect the choke wires in its place.
The second most common modification is to add a supplemental power supply capacitor. Most users have added a motor RUN (not start) capacitor in parallel with C5. You want a non polarized polypropylene capacitor with a low ESR characteristic. There are capacitors made for this purpose such as the Solen "fast cap". This improves the transient response and reduces hum. I added a large 100 uF, 370 volt AC polypropylene motor RUN cap to my 300B amp, and added a smaller 20 uF polypropylene 400 volt DC ASC leaded capacitor to my Lexan universal amp. They did make noticeable improvements. This is a recommended modification. Leave C5 in place, and run wires to the supplemental capacitor, connecting it in parallel with C5.
A choke input (LCRC or LCLC) filter can be implemented by cutting the PC board runner between the 5AR4 and C4 and wiring an external choke in between these two points. The second choke (if desired) is connected in place of R4. I have not noticed any benefit from this modification however it may be useful to lower the supply voltage in some cases.
FWIW, I bought a couple of ASC 30uf oil filled caps that I need to add to my amp. Going to add them in when I box it up in a chassis.
Its almost at the bottom of this page:
Tubes and Applications | Tubelab
Modifications to Improve the Sound
The board is designed to be built using a capacitor input filter with a choke or a resistor in between the two capacitors. If a choke is desired it may be connected in place of R4. This is a HIGHLY recommended modification. Many early users found that a choke was needed when using high efficiency speakers. I have since added a choke to my amplifiers, and found improved bass and dynamics even though I had no hum. People have asked " what kind of choke do I use?" I use the Triad C-14X because it has 150 ohms of DC resistance. It is UGLY, so you will want to hide it under the chassis. If you need a better looking choke, use one that has nearly 150 ohms of resistance, and has the same or higher current rating as the power transformer. The Hammond 193J will work, but you will gain a few volts of B+ because it is only 82 ohms. Remove R4 and connect the choke wires in its place.
The second most common modification is to add a supplemental power supply capacitor. Most users have added a motor RUN (not start) capacitor in parallel with C5. You want a non polarized polypropylene capacitor with a low ESR characteristic. There are capacitors made for this purpose such as the Solen "fast cap". This improves the transient response and reduces hum. I added a large 100 uF, 370 volt AC polypropylene motor RUN cap to my 300B amp, and added a smaller 20 uF polypropylene 400 volt DC ASC leaded capacitor to my Lexan universal amp. They did make noticeable improvements. This is a recommended modification. Leave C5 in place, and run wires to the supplemental capacitor, connecting it in parallel with C5.
A choke input (LCRC or LCLC) filter can be implemented by cutting the PC board runner between the 5AR4 and C4 and wiring an external choke in between these two points. The second choke (if desired) is connected in place of R4. I have not noticed any benefit from this modification however it may be useful to lower the supply voltage in some cases.
FWIW, I bought a couple of ASC 30uf oil filled caps that I need to add to my amp. Going to add them in when I box it up in a chassis.
Having the lowest possible AC source impedance across the entire audio frequency range from the power supply generally helps the sound quality in a SE amplifier. As we discovered in the SSE amps, often pure electrolytics can exhibit some less than perfect response at the frequency extremes, so bypassing them with a capacitor having different characteristics can be an improvement.
A polypropylene capacitor will usually preform better as a bypass capacitor in the higher audio frequency range, while the electrolytic does a better job at bulk energy storage. Both together often work better than either alone.
I put a 20 uF 400 volt poly cap across the last electrolytic in my TSE and it did remove that last bit of hum I had when I took my amp to visit some 106 dB Lowther based horns. I used 30 uF because it was the biggest cap I could fit inside my tiny amp chassis.
Use a polypropylene cap of any uF rating up to about 100 uF. The voltage rating must be higher than your B+. There are dozens of audiophile grade expensive capacitors, but common motor RUN (not START) caps are typically very good for not a lot of money......that's what I typically use.
Note that motor RUN caps like found in AC compressor and fan motor applications are usually poly caps that were designed to CONTINUOUSLY operate DIRECTLY from the AC line (mains) and therefore pass considerable AC current with low loss. That is what you WANT. They are typically rated for AC voltage, and anything above 370 VAC is good for a TSE. They are not polarized and can be connected either way. They are almost always housed in an aluminum can.
Motor START caps are non-polarized electrolytics rated for temporary connection to the line when a motor starts up. It is then switched off line by a cenrtifugal switch. They are NOT capable of continuous duty, will not improve your sound, and may fail in a spectacular fashion if used. These are usually in black plastic. Unscrupulous EBAY sellers often call them motor run caps. You do NOT want one in your amp.
A polypropylene capacitor will usually preform better as a bypass capacitor in the higher audio frequency range, while the electrolytic does a better job at bulk energy storage. Both together often work better than either alone.
I put a 20 uF 400 volt poly cap across the last electrolytic in my TSE and it did remove that last bit of hum I had when I took my amp to visit some 106 dB Lowther based horns. I used 30 uF because it was the biggest cap I could fit inside my tiny amp chassis.
Use a polypropylene cap of any uF rating up to about 100 uF. The voltage rating must be higher than your B+. There are dozens of audiophile grade expensive capacitors, but common motor RUN (not START) caps are typically very good for not a lot of money......that's what I typically use.
Note that motor RUN caps like found in AC compressor and fan motor applications are usually poly caps that were designed to CONTINUOUSLY operate DIRECTLY from the AC line (mains) and therefore pass considerable AC current with low loss. That is what you WANT. They are typically rated for AC voltage, and anything above 370 VAC is good for a TSE. They are not polarized and can be connected either way. They are almost always housed in an aluminum can.
Motor START caps are non-polarized electrolytics rated for temporary connection to the line when a motor starts up. It is then switched off line by a cenrtifugal switch. They are NOT capable of continuous duty, will not improve your sound, and may fail in a spectacular fashion if used. These are usually in black plastic. Unscrupulous EBAY sellers often call them motor run caps. You do NOT want one in your amp.
Randytsuch
Yes I see it on the site. In the section. Designs-Tubelab SE
Power Supply Design
The on board power supply uses FRED diodes for the bias (negative) voltages. This allows fast startup of the bias supply. The plate (positive) voltages are tube rectified. A 5AR4 is recommended because of it's slow warm up characteristics. This allows all of the amplifier tubes time to warm up before the plate voltage is applied. The plate supply can be choke or capacitor input. There is room for a large power supply cap if you want one (to the left of the volume control), although it doesn't seem to make much difference. Provisions are made for an external bypass capacitor from the B+ side of the output transformer to the output tube filament (ground). An oil cap or a Solen Fast Cap may improve the sound. My new amps use ASC motor RUN caps for the supplemental cap (100 uF 370 VAC). All filaments run on DC, there is no audible hum. There is a voltage regulator to assure that the DHT's receive the correct filament voltage with very low ripple. If it seems that considerable time was spent on the power supply, you are right. The power supply is an integral part of the signal path in an SE amp.
George
Is it better or the same, to place The capacitor between the B+ by the output transformer and the output tube filment Ground as across the C5 ?
Is it best to place a capacitor both Places ?
I think you mean the C5 when you say the last electrolytic in you`r TSE is it right.
Michael
Yes I see it on the site. In the section. Designs-Tubelab SE
Power Supply Design
The on board power supply uses FRED diodes for the bias (negative) voltages. This allows fast startup of the bias supply. The plate (positive) voltages are tube rectified. A 5AR4 is recommended because of it's slow warm up characteristics. This allows all of the amplifier tubes time to warm up before the plate voltage is applied. The plate supply can be choke or capacitor input. There is room for a large power supply cap if you want one (to the left of the volume control), although it doesn't seem to make much difference. Provisions are made for an external bypass capacitor from the B+ side of the output transformer to the output tube filament (ground). An oil cap or a Solen Fast Cap may improve the sound. My new amps use ASC motor RUN caps for the supplemental cap (100 uF 370 VAC). All filaments run on DC, there is no audible hum. There is a voltage regulator to assure that the DHT's receive the correct filament voltage with very low ripple. If it seems that considerable time was spent on the power supply, you are right. The power supply is an integral part of the signal path in an SE amp.
George
Is it better or the same, to place The capacitor between the B+ by the output transformer and the output tube filment Ground as across the C5 ?
Is it best to place a capacitor both Places ?
I think you mean the C5 when you say the last electrolytic in you`r TSE is it right.
Michael
Thank you for the response. I write this thread because I have a hum problem/challenge on my TSE. I have placed a 100uf 370V motorrun cap parallel across with C5, but have still a hum tone in my speaker. (my SSE is total quiet)
My choke (in sted of R4) is a Hammond 158M and is placed under a 3mm aluminium plate/sheet inside the enclosure. My power transformer Hammond 370EX is on the Top side of the sheet out of the enclosure.
Are there other things I could do to reduce the hum? I am uncertain what to do, so i hope for help. Thanks!
Michael
My choke (in sted of R4) is a Hammond 158M and is placed under a 3mm aluminium plate/sheet inside the enclosure. My power transformer Hammond 370EX is on the Top side of the sheet out of the enclosure.
Are there other things I could do to reduce the hum? I am uncertain what to do, so i hope for help. Thanks!
Michael
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I use my TSE as a headphone amp, so as you can imagine any hum is not good.
This week, I reworked my TSE to change the CLC to a CLCLC filter on B+ by adding another inductor and a 47uf cap. I used two Triad C-14X for the inductors. If you have the space, its pretty straightforward to add the 2nd inductor and cap.
Connected the two inductors, and then the two loose ends go to the R4 holes. The additional cap low goes to ground, high goes to the point the two inductors are tied together at. The new cap is just floating in the air right now, I'll probably glue it down when I install everything in its case.
Based on PSUD and my listening to it, it is quieter after adding this change.
No idea if others have tried this.
This week, I reworked my TSE to change the CLC to a CLCLC filter on B+ by adding another inductor and a 47uf cap. I used two Triad C-14X for the inductors. If you have the space, its pretty straightforward to add the 2nd inductor and cap.
Connected the two inductors, and then the two loose ends go to the R4 holes. The additional cap low goes to ground, high goes to the point the two inductors are tied together at. The new cap is just floating in the air right now, I'll probably glue it down when I install everything in its case.
Based on PSUD and my listening to it, it is quieter after adding this change.
No idea if others have tried this.
When I get around to building mine I’m planning on choke input (LCLC) with the triad in the second place and the motor run bypass cap. I haven’t modeled it yet on PSUD so I have no idea what specs I’ll need for the first choke, though I do plan on getting the “Edcor TSE” power transformer and want to run 45 power tubes.
OK thank you for the reply. It is very interesting design.(I am learning) 2xC-14x in series connection.+ another bypass cap between them. What about the B+ level, have it make a change or is it still the same? I think the impedance raise (2x 150 ohm) perhaps could do a difference.
It is just a simpel change as you mention it, so I will try it out and see what happens.
Brinkmann - Good luck with your build!
It is just a simpel change as you mention it, so I will try it out and see what happens.
Brinkmann - Good luck with your build!
In my setup, adding another LC dropped B+ about 10V. I'm going to make the first cap a little larger to adjust for the drop in B+, but 10V is not much anyway. My bias is at 25mA per channel.
Brinkman
When I ran a LCLC filter in PSUD, voltage drops a lot having the inductor first. I would need a higher voltage from my power tranny to run this filter.
Randy
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