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Where should I connect ground reference for heater supply?

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My DIY system has one board for anode supply, one for the left channel single-triode line stage and one for the right channel. Each board has its own ground, then the grounds of the two line stage boards are connected to the ground of the anode supply board. I use AC for triode heaters. As the 6.3V secondaries (one for each triode) have a center tap, I think to connect those taps to ground. I wonder whether I should connect the center tap to the local ground of each line stage board, or to the common ground on the anode supply board (which is the closest to the transformer).
Any opinion would be much appreciated.

Paul
 
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Power supply grounds power and filaments should be connected to system or star grounds isolated from chassis, ground loops will induce into chassis and permeate into tubes and resistors, seprate ground for amp system and seprate for chassis, connect bypass cap .47 mf from system ground to chassis this way you wont have to lift the ground from the plug because your preamp is picking up hum from the chassis. common mistake people make is the rca jacks, they drill the chassis and mount right to it, they sould not ground to chassis, they should ground to system ground, have to isolate rca from the chassis. Get them already mounted on the bakelite strip and mount into square hole cut in chassis and ground to system ground. When i started building amp 30 years ago made the mistake and always broke the ground prong off until I got zapped from a transformer that had a internal short to ground....now I never have a hum issue since I have done this...remeber nothing ground to the chassis except for the 3rd prong, and add the bypass cap from ur system ground buss to the chassis for radio noise and stray hum from the power transformer...... get a copy of Radiotrons Designers handbook 4th edition awesome book for tubes, read 8 times already...http://headfonz.rutgers.edu/RDH4/ Radiotrons 4th edition in pdf from Rutgers university...can download as pdf too. good luck and build safe.
 
I have an additional question...

The russian 6C33C-B has a double filament, either supplied in parallel with 6.3V~ or serial with 12.6V~. Is it a good idea to connect pin 2 and 6 to 12.6V~ and pin 1 and 7 to ground? Or ist it better to connect pin 1 with pin 7 (floating) and connect a resistor from pin 2 to ground and a second resistor from pin 6 to ground?

The datasheet of the 6C33C-V can be found here:
http://www.jogis-roehrenbude.de/Russian/6C33C/6C33C-B-6S33S-VExtendedDatasheetMB.pdf
 
Thank you all for answering.
If I understood well, gianxdiy'a advice is to connect center taps to the anode supply ground, while trobbins suggests to connect them to the local grounds. Great dilemma...

My preamplifier has a transformer coupled output and RCA jacks are insulated from the chassis. Is it safe to directly connect the ground of the amps to the anode supply ground?
 
psaitz,
depending on the voltage you use will determine how to wire the filaments, 12.6v series the filaments -connect 2 and 6 together and put your 12 volts on 1 and 7. If you choose 6.3v, connect 2 and 6 together then connect 1 and 7 together and apply the 6 volts to 1 and 2 or 6 and 7, if you filament supply has a center tap that would be grounded to chassis. If it doesnt I highly suggest a 100 ohm potentimeter around 3 to 5 watt rating and make sure wirewound type, ground the center or wiper to chassis ground and the other 2 connections would connect to each of the filament connections where the power is supplied to tubes. this gives you the option to balance or dimish and hum induced through heater leakage or imbalance that will induce hum into the tube and eventually makes its way into the signal causing hum into your speakers.
try to get big enough filament transformer to handle all the tubes, mulitble transformers with different voltages have different loads and can inject eddy currents into nearby weaker or smaller loaded transformers, most of the time the center taps work and the pot, so if you use more than one filament transformer turn the iron laminations oppisite each other. dont let the iron of the transformers be next to each other. build safe...john

Sandor,
using coupling transformers is tough, you need to keep away from power transformers and choke due to hum and loaded choke produce a heavy magnetic field that can permiate the coupling transformer and induce hum.
depending on the transformer some have center taps that can be grounded to the amp ground not the power supply ground or chassis. power supply center taps from the transformers should be the only thing grounded to chassis, amp and powersupply, (Capacitor grounds), should have a seprate ground completely isolated from the chassis. 99% of the time if you follow this method you amp will be hum free the other 1 percent is usually input wires to close to power supply or ac feeder lines to transformers, rca gorunds always ground to amp ground not chassis, if it is hum will develop from the amp or a ground loop from a external circuit like the preamp or cd player...if you have hum with the open loop, (with rca of amp connected to nothing), usually a leaky filament or gassy tube, if its the filament simple remedy is a bypass cap from chassis ground to amp ground to bleed off stray ac from filament to ground instead of into signal of tube. always connect the grounding prong of wall plug to chassis...build safe...john
 
Ground wiring schematic

Please find attached the ground wiring schematic according to what I understood of your suggestions.
Please confirm that the schema is the right one.
Thank you.

Paul
 

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Sandor, your schematic leave much to the imagination, what kind of rectification are you using? What are you filtering sizes, are you using chokes or resistors? I sent you a link for the radiotrons designers handbook 4th edition earlier in the thread. This is the bible to tube amplification...I can help you but you need to be more specific in you drawing, component wise. As for your preamp anode supplies going back to the main power supply I dont get that, to me it looks like a huge loop and mixing voltages, feeding through other transformer or filter networks will be a disadvantage to the sound quality and raise the impedance the tubes see, plus your output stage will be pulling from input anode supply dragging down the voltage of the input causing higher distortion.
I had mentioned a r/c network from one powersupply, thats the way you should go...give me more info about the powersupply and I will gladly help you along the way. Dont know if you have visio or cad but this is how you should draw it. I think I have a older version of Visio before microst ripped it apart, its a full version and about 33meg, dont know if I can attach will probably have to zip it... you can download to your docs and run right from the visio32 icon. I will try and post as zip later. Cant break file down to load to site, email me and I will try to attach to your email. Soundude@gmail.com, Build safe...john
An externally hosted image should be here but it was not working when we last tested it.
 
I attached the schematic of the power supply.
The two gain stages are balanced line stages, not power amps. They are very simple, a push-pull of two triodes. Input signal is directly fed into grids. Anodes are connected to an output transformer. Anode supply is connected to the center tap of the output transformer.
How should I connect anode supply from the supply board to the gain stage boards?
Is it correct to connect heater center taps directly to the chassis?

Thanks a lot for your support.
Paul
 

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Paul, sorry I thought you said push pull you were refering to power amplifier...if you look at the power supply I posted you will see a resistor coupled or paralled with a bypass but for what you want you need to ground the chassis with the green wire from plug and isolate the amp ground from the chassis, couple chassis and amp ground with bypass cap. this keeps the chassis ground off the amp ground, it will prevent ground loops from connecting equiptment. What I did with mine is add a switch to short the bypass which will connect the amp ground to the chassis ground, when doing A/V you might get hum or 60hz lines in / from the video, thats why I put the switch in, also if you have a voltage regulated dc on your preamp tube filaments you want it to float, just use the bypass cap to bleed stray ac to chassis.
Secondary center taps of filament and power transformer should be connected to amp ground not chassis.
Since you are using a interstage transformer, the outputs are isolated from the enite circuit so you might have to ground the rca ground to the amp ground, especially if you have feedback implied..do you have polarity dots on the transformer schematic so you know the phasing is right?
Are you implementing feedback in this preamp? If your polarity or phasing is reversed with feedback you will get parasitic oscillation at the outputs as soon as you connect the ground or connect your amplifier.
I personally dont like transformers that early in the stage, even transformers in the phono stage...to acceptical to rf and hum from power lines and power transformers.
Well only one way to learn, from mistakes, use a crappy amp and speakers just in case. Dont worry I did the same thing when I built my first amp...what a horrible noise it was. Just need to reverse tubes primaries of transformer.
 
Go back a few posts, I put a link in one of my posts for Radiotrons 4th edition, headfonz at rutgers university has it posted in PDF so you can save by chapter.
There is a entire section on transformer and power supplies for preamp and power amp...there ia a ton of excellent info in that book, I ran off 4 copies so theres one every where I am, work, home, car, and inlaws house!!!!
 
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