Still a nice build, I like this "raw look" 
I'm actually wondering you came out with one such 600VA transformer and still have manageable heat of it, for me the heater transformer alone is getting quite warm (at around 41˚C) for the hand when touched during operation and class-A is again loading the anode voltage generating part of the transformer to 90% approx also when idle.
Looking at the Antek, this serves both left and right sides for you with anode voltage, small and large tube heating, everything actually.
Maybe you can answer my question above regarding the "deep minus" potential-shifts of some heatings onto HT3 and HT4.
Mine is a little different:
My struggle is: if I need to shift 6C33C common (1-PSU) heater voltage base-potentials onto HT3 and HT4 which are on 2 separate anode voltage circuits
1. can I do it at all ?
2. if yes, I assume there's no difference if I use HT3 and HT4 of the left side anode voltage circuitry OR the right sides's circuit.
3. if I can't do it, would it make sense to use the 2 anode-voltage transformers in parallel and be okay with 1 bigger anode-voltage PSU ? (1 full-rect. bridge and everything behind that, feeding both Lelf and Right audio circuit so there are only 1 common HT3 and HT4 points for left and right side tubes).
I'm actually wondering you came out with one such 600VA transformer and still have manageable heat of it, for me the heater transformer alone is getting quite warm (at around 41˚C) for the hand when touched during operation and class-A is again loading the anode voltage generating part of the transformer to 90% approx also when idle.Looking at the Antek, this serves both left and right sides for you with anode voltage, small and large tube heating, everything actually.
Maybe you can answer my question above regarding the "deep minus" potential-shifts of some heatings onto HT3 and HT4.
Mine is a little different:
- for audio (anode voltage), 2 separate transformers (and diode bridges etc.) are used. Like a fully separated 2-monoblock design.
- for heating of the big tubes, 1 common transformer is used, feeding both left and right-side 6C33C-s.
My struggle is: if I need to shift 6C33C common (1-PSU) heater voltage base-potentials onto HT3 and HT4 which are on 2 separate anode voltage circuits
1. can I do it at all ?
2. if yes, I assume there's no difference if I use HT3 and HT4 of the left side anode voltage circuitry OR the right sides's circuit.
3. if I can't do it, would it make sense to use the 2 anode-voltage transformers in parallel and be okay with 1 bigger anode-voltage PSU ? (1 full-rect. bridge and everything behind that, feeding both Lelf and Right audio circuit so there are only 1 common HT3 and HT4 points for left and right side tubes).
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Vortex if you want to make the LEFT and RIGHT channel separated like 2 independent mono blocks you must separate everything, you must build 2 PSU, with 2 transformer etc., even the ground should be separated and insulated from the chassis, that involve insulate the input plug and speakers post also, in this way you have 2 mono block in the same enclosure.
In my opinion do not try to make one HT3 and HT4 common for the 2 channels while the PSU are separated, the only thing that can be common are the heaters, I hope can help....
In my opinion do not try to make one HT3 and HT4 common for the 2 channels while the PSU are separated, the only thing that can be common are the heaters, I hope can help....
Hi, I plan this exactly, 2 monoblocks in 1 chassis, fully separated PSU-s (2 transformers) available. RCA and XLR inputs isolated from chassis, speaker terminals too.
1 common heater transformer for all 4 6C33C tubes.
Ground bus (a thick copper wire) is common however, at least I began to route it with careful bendings alongside the inner wall already.
Why do you think it's needed to have separated too if - at the end of the day - both side's ground will be connected (via this ground bus) to the IEC AC inlet's ground pin anyway ?
I thought about star topology too (same from electrical point of view) but the ground bus helped me out in my previous design and here's also one example of it done well.
Just asking out of curiosity, ground loop won't be existing still (I hope), but since both sides's ground sooner or later connect to the IEC AC inlet's ground - hence, common ground - this common ground isn't really needed to be separated and 1 ground bus can be used for both sides I think. Everything on the schematics what is marked with a connection towards ground, can be connected to this ground bus I assume. Speaker terminal minus too, as I see.
(Speaker minus could be chassis itself as well, since chassis is also grounded at the IEC AC inlet, but I get your point, isolate it from chassis and connect speaker minus to internal ground bus to avoid loops, right?)
What you suggest would tell me (regarding ground) that 2 separate amps with 2 separate ground buses are 'floating' from ground point of view compared to eachother, while being at the same time on the same normal ground potential due to IEC AC inlet ground connection for both. So why separating then the ground between the 2 sides, despite having a monoblock-like topology ?
Maybe I'm missing something Really asking, I'm not the big electrician here.
1 common heater transformer for all 4 6C33C tubes.
Ground bus (a thick copper wire) is common however, at least I began to route it with careful bendings alongside the inner wall already.
Why do you think it's needed to have separated too if - at the end of the day - both side's ground will be connected (via this ground bus) to the IEC AC inlet's ground pin anyway ?
I thought about star topology too (same from electrical point of view) but the ground bus helped me out in my previous design and here's also one example of it done well.
Just asking out of curiosity, ground loop won't be existing still (I hope), but since both sides's ground sooner or later connect to the IEC AC inlet's ground - hence, common ground - this common ground isn't really needed to be separated and 1 ground bus can be used for both sides I think. Everything on the schematics what is marked with a connection towards ground, can be connected to this ground bus I assume. Speaker terminal minus too, as I see.
(Speaker minus could be chassis itself as well, since chassis is also grounded at the IEC AC inlet, but I get your point, isolate it from chassis and connect speaker minus to internal ground bus to avoid loops, right?)
What you suggest would tell me (regarding ground) that 2 separate amps with 2 separate ground buses are 'floating' from ground point of view compared to eachother, while being at the same time on the same normal ground potential due to IEC AC inlet ground connection for both. So why separating then the ground between the 2 sides, despite having a monoblock-like topology ?
Maybe I'm missing something
Really asking, I'm not the big electrician here.
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Okay, this is where I am right now. 2 separate PSU-s, 1 common heater transformer.
Looking at the original schematics, V5's heating shall be connected to HT4 (-150).
Due to common heater transformer, I have 2x V5 tubes heated by the same transformer, it's a parallel connection from the transformer taps.
So, Left side V5 is heated from the very same transformer like Right side's V5.
HT4 is available at PSU side. Either left or right.
To which side's HT4 connection would you connect the common heating of the two V5 tubes ?
(If doable at all).Same for V2-V3, heater is a small transformer, but common for both sides, so 4 small tubes' heating shall be connected to HT3 (-450V) but I also have 2 HT3 connections due to separate PSU parts. Left and right.
To which PSU's HT3 shall I connect the common heating of V2-V3 tubes ?
(If doable at all, again).
So at the moment I see 3 way outs:
1. fine so, choose for the common heaters whichever side's HT3 and HT4 points.
2. don't do point 1, instead do following: give up separate PSU idea and connect the 2 PSU transformers parallel, build 1 PSU after it for both sides and use that for both audio circuits. Heater potential issue is solved then, there will be only 1 common HT3 and HT4 point for both sides.
3. don't do point 2, separate heating of left and right side too with an additional heater transformer identical with the existing one, so the full-monoblock setup is then also valid for the heating circuits itself, each side's heating is ran from its own heater transformer and connected to its own HT3 and HT4. -> additional money and a second chassis probably due to space issues then. Which is a viable option but not the best one due to cost and time.
So I'd strive for 1 or 2, if possible from electrical point of view.
1. fine so, choose for the common heaters whichever side's HT3 and HT4 points.
2. don't do point 1, instead do following: give up separate PSU idea and connect the 2 PSU transformers parallel, build 1 PSU after it for both sides and use that for both audio circuits. Heater potential issue is solved then, there will be only 1 common HT3 and HT4 point for both sides.
3. don't do point 2, separate heating of left and right side too with an additional heater transformer identical with the existing one, so the full-monoblock setup is then also valid for the heating circuits itself, each side's heating is ran from its own heater transformer and connected to its own HT3 and HT4. -> additional money and a second chassis
probably due to space issues then. Which is a viable option but not the best one due to cost and time. So I'd strive for 1 or 2, if possible from electrical point of view.
Hi Vortex!
Correct! Keep the two ground buses separated from each other and also from chassis. The one and only touchpoint should be the ground pin of the input potentiometer. The PE from power cord connects to the chassis and chassis connects to the ground bus through the same touchpoint in the input (star connection point) but not directly but through connected in parallel resistor (10-20 ohms) and two diodes in opposite directions (1N4007 for example). Why? It keeps the Eddy currents away from chassis and avoids the signal path not running by chassis. Eddy current is also called Foucault current. And keep all input and output sockets isolated from chassis.
Correct! Keep the two ground buses separated from each other and also from chassis. The one and only touchpoint should be the ground pin of the input potentiometer. The PE from power cord connects to the chassis and chassis connects to the ground bus through the same touchpoint in the input (star connection point) but not directly but through connected in parallel resistor (10-20 ohms) and two diodes in opposite directions (1N4007 for example). Why? It keeps the Eddy currents away from chassis and avoids the signal path not running by chassis. Eddy current is also called Foucault current. And keep all input and output sockets isolated from chassis.
One day I will build the Tim Mellow 6C33C OTL design and I've been slowly accruing the parts over the years.
In the meantime, I don't know if anyone is interested in, or even has experience of, the attached variant of the Mellow OTL using Russian sub-minitiaure tubes. To view, unzip the file and click on the 'trioeamp2013' html file and it should open in your browser. The original website doesn't seem to be avaailable anymore so I'm glad I grabbed a copy.
In the meantime, I don't know if anyone is interested in, or even has experience of, the attached variant of the Mellow OTL using Russian sub-minitiaure tubes. To view, unzip the file and click on the 'trioeamp2013' html file and it should open in your browser. The original website doesn't seem to be avaailable anymore so I'm glad I grabbed a copy.
Wow nice, thank you.
So just to make sure I understood correctly:
- Power cord arrives into the chassis via 3-pole IEC connector
- chassis can right here be connected to PE (or not yet?)
- isolated PE cable runs within chassis to stereo input pot's GND legs (this will be the star point)
- chassis is connected to this star ground point via aforementioned extra passive elements
- the 2 ground buses for L/R sides also connect here (and can be seen actually as 1 ground bus )
I assume I do NOT connect chassis yet to incoming PE at the IEC terminal's inner side but let the PE isolated cable run inside to the pot and this is the only point where chassis is connected to PE, right ?
Answer to first section of Your question:
Answer to the second section is:
This means the chassis and system ground are "separated" or the system ground is a bit "elevated" with regard to chassis, causing the best and shortest path for signal to move. Not through the chassis material and bolts or around who knows which corner. Hope the explanation was´nt too complicated
- Power cord arrives into the chassis via 3-pole IEC connector - YES
- chassis can right here be connected to PE (or not yet?) - YES
Answer to the second section is:
- isolated PE cable runs within chassis to stereo input pot's GND legs (but is not connected to these directly!)
- chassis is connected to this star ground point via aforementioned extra passive elements
- the 2 ground buses for L/R sides also connect here (and can be seen actually as 1 ground bus - CORRECT!
This means the chassis and system ground are "separated" or the system ground is a bit "elevated" with regard to chassis, causing the best and shortest path for signal to move. Not through the chassis material and bolts or around who knows which corner. Hope the explanation was´nt too complicated
Hi Vortex,Nice build, you also chose the Winged C-s instead of EF86s (same, I know). Same sockets, same elevation method like in my case
Cool
Mine isn't assembled yet, in progress.
other day of testing so I got the temperatures after 1 hour of continuous operating:
- 6C33C tube 66 centigrade
- chassis surface around the 6C33C 42 centigrade
- main transformer 42 centigrade, little bit higher 48 centigrade where is closer to the 6C33C
- room temperature with air-con 27 centigrade.
Now it's clear, thank you A LOT ! I'll make it accordingly.Answer to first section of Your question:
- Power cord arrives into the chassis via 3-pole IEC connector - YES
- chassis can right here be connected to PE (or not yet?) - YES
Answer to the second section is:
- isolated PE cable runs within chassis to stereo input pot's GND legs (but is not connected to these directly!)
- chassis is connected to this star ground point via aforementioned extra passive elements
- the 2 ground buses for L/R sides also connect here (and can be seen actually as 1 ground bus - CORRECT!
This means the chassis and system ground are "separated" or the system ground is a bit "elevated" with regard to chassis, causing the best and shortest path for signal to move. Not through the chassis material and bolts or around who knows which corner. Hope the explanation was´nt too complicated
Hi kissabout2002,
thank you for confirming these data. Mine will have no fan so all natural airflow.. front-bottom of chassis has cutouts, just like the bottom-back, so I hope for some effective airflow here.
Sockets are elevated very much the way you did so there some air can flow out.
We'll see if this setup is manageable. If not, I still have place for 2x 80mm fans, however need to cut the aluminum chassis (CNC machined again) then.
thank you for confirming these data. Mine will have no fan so all natural airflow.. front-bottom of chassis has cutouts, just like the bottom-back, so I hope for some effective airflow here.
Sockets are elevated very much the way you did so there some air can flow out.
We'll see if this setup is manageable. If not, I still have place for 2x 80mm fans, however need to cut the aluminum chassis (CNC machined again) then.
Any further comments on my previous questions ?
Which HT3 and HT4 points to pick for the potential-shifted heaters ?
So, I have the minus-potential HT3 (-430V) and HT4 (-150V) points twice: Left side amp PSU and Right side amp PSU.
The original schematics tells us to connect V2+V3 heater potentials to HT3 and V5 to HT4.
Okay, but which HT3 and which HT4 ? Left or right ?
Again: common heater transformers (1 for ALL small tubes + 1 for ALL 6C33C tubes) and separate PSU circuits like in a monoblock design.
Transformers have 2 secondaries: 1 for GND potential and 1 for the shifted potential heaters.
Would it smoke if I connected all V2+V3's heating (4 tubes!) to let's say left channel PSU's HT3 for the potential shift, and connect V5 tubes (2 tubes!) of left and right side to the right side PSU's HT4 ?
Which HT3 and HT4 points to pick for the potential-shifted heaters ?
- I have 1 heater transformer for ALL 6C33C tubes (with 2x 12V secondaries, one intended to be on GND potential, the other on HT4 -150V).
- I have 2 separate transformers for the amp part itself, so multiply original article's PSU by 2.
So, I have the minus-potential HT3 (-430V) and HT4 (-150V) points twice: Left side amp PSU and Right side amp PSU.
The original schematics tells us to connect V2+V3 heater potentials to HT3 and V5 to HT4.
Okay, but which HT3 and which HT4 ? Left or right ?
Again: common heater transformers (1 for ALL small tubes + 1 for ALL 6C33C tubes) and separate PSU circuits like in a monoblock design.
Transformers have 2 secondaries: 1 for GND potential and 1 for the shifted potential heaters.
Would it smoke if I connected all V2+V3's heating (4 tubes!) to let's say left channel PSU's HT3 for the potential shift, and connect V5 tubes (2 tubes!) of left and right side to the right side PSU's HT4 ?
Downloaded and unzipped- But could not locate schematic file of above reference... just a lineage of discussion- maybe I'm doing something wrong- idk
Possible that you could post that single unzipped file here, please?
Hi Vortex,Any further comments on my previous questions ?
Which HT3 and HT4 points to pick for the potential-shifted heaters ?
- I have 1 heater transformer for ALL 6C33C tubes (with 2x 12V secondaries, one intended to be on GND potential, the other on HT4 -150V).
- I have 2 separate transformers for the amp part itself, so multiply original article's PSU by 2.
So, I have the minus-potential HT3 (-430V) and HT4 (-150V) points twice: Left side amp PSU and Right side amp PSU.
The original schematics tells us to connect V2+V3 heater potentials to HT3 and V5 to HT4.
Okay, but which HT3 and which HT4 ? Left or right ?
Again: common heater transformers (1 for ALL small tubes + 1 for ALL 6C33C tubes) and separate PSU circuits like in a monoblock design.
Transformers have 2 secondaries: 1 for GND potential and 1 for the shifted potential heaters.
Would it smoke if I connected all V2+V3's heating (4 tubes!) to let's say left channel PSU's HT3 for the potential shift, and connect V5 tubes (2 tubes!) of left and right side to the right side PSU's HT4 ?
well due to the fact that you have two separate PSU you can then choose to use HT3 and HT4 from the right or left PSU, I do not see any problem but of course the ground bus must be one.
I connect the the 4 V2+V3's heater together no problem, they have just 200mA so for the 4 in parallel 6.3v 1A secondary will be enough
When the PSU's are done test without tubes that all tension are correct
Thank you VF for this, I also did it, by the way I remember you built this amp inside a stone ball right? Very beautiful , still working good ? all the best
Acky
The zip file contains a website that I downloaded before it went extinct so it isn't a single file. When you unzip (unzip to 'RussianSubMin') you should have a file that contains the html file 'triodeamp2013' and a sub-folder 'triodeamp2013_files', as per the attached screengrab. Open the html file in your browser and it should display as a website, which includes the schematic and information about the sub-miniature tubes, as per the second screengrab. The sub-folder contains a file with the schematic but because it is intended for the website presentation is all but impossible to read, you could probably address that but I didn't bother as the website works for me.
Incidentally, the most recent Ares Audio version of the Mellow amp looks interesting, apart from the eight 6C33Cs everything is implemented on a single high quality PCB.
https://www.aresaudio.com/ares_v4.php
https://www.aresaudio.com/ares_v4.php