Where should I connect ground reference for heater supply?

Sandor · 08:53 PM

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

gianxdiy · 7th February 2012, 08:55 PM

Connecting to local ground and those to ground = Loops
Connect every ground using a wire for each one to anode ground.
Let us know...

trobbins · 7th February 2012, 10:50 PM

My suggestion would be to take the heater CT for each triode (if it is a separate heater winding just for the one triode) to the star ground of that triode's channel board. The heater is electrically isolated, but parasitic hum/noise current can flow, and so should be confined to that local cathode circuit loop.

Ciao, Tim

Soundude · 8th February 2012, 01:54 AM

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.

trobbins · 8th February 2012, 05:07 AM

Soundude, I'm not sure if many would recommend not making a galvanic connection from amp system ground to chassis, and only using just a capacitor connection between system ground to chassis. I think that is what you are recommending?

oshifis · 8th February 2012, 11:03 AM

I think it is against safety. If there is short from B+ to chassis, you won't notice it, until you touch the RCA ground...

Soundude · 8th February 2012, 02:09 PM

Sorry absolutly rite, worded wrong, power supply grounds are star grounded to chassis but amp grounds are Isolated, then a bypass cap from system ground to chassis ground.. to leak of stray ac.
sorry for that...

psaitz · 8th February 2012, 04:06 PM

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/Russ...atasheetMB.pdf

Sandor · 9th February 2012, 09:40 PM

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?

Soundude · 9th February 2012, 11:12 PM

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

7th February 2012, 08:50 PM	#1
Sandor diyAudio Member Join Date: Mar 2004 Location: Milan	Where should I connect ground reference for heater supply? 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 Last edited by Sandor; 7th February 2012 at 08:53 PM. Reason: typo

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7th February 2012, 08:55 PM	#2
gianxdiy diyAudio Member Join Date: Jan 2009 Location: Pescara	Connecting to local ground and those to ground = Loops Connect every ground using a wire for each one to anode ground. Let us know...

7th February 2012, 10:50 PM	#3
trobbins diyAudio Member Join Date: Feb 2009 Location: Melbourne, Oz	My suggestion would be to take the heater CT for each triode (if it is a separate heater winding just for the one triode) to the star ground of that triode's channel board. The heater is electrically isolated, but parasitic hum/noise current can flow, and so should be confined to that local cathode circuit loop. Ciao, Tim

8th February 2012, 01:54 AM	#4
Soundude diyAudio Member Join Date: Jan 2010	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.

8th February 2012, 05:07 AM	#5
trobbins diyAudio Member Join Date: Feb 2009 Location: Melbourne, Oz	Soundude, I'm not sure if many would recommend not making a galvanic connection from amp system ground to chassis, and only using just a capacitor connection between system ground to chassis. I think that is what you are recommending?

8th February 2012, 11:03 AM	#6
oshifis diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	I think it is against safety. If there is short from B+ to chassis, you won't notice it, until you touch the RCA ground...

8th February 2012, 02:09 PM	#7
Soundude diyAudio Member Join Date: Jan 2010	Sorry absolutly rite, worded wrong, power supply grounds are star grounded to chassis but amp grounds are Isolated, then a bypass cap from system ground to chassis ground.. to leak of stray ac. sorry for that...

8th February 2012, 04:06 PM	#8
psaitz diyAudio Member Join Date: Jan 2008 Location: Vienna	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/Russ...atasheetMB.pdf

9th February 2012, 09:40 PM	#9
Sandor diyAudio Member Join Date: Mar 2004 Location: Milan	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?

9th February 2012, 11:12 PM	#10
Soundude diyAudio Member Join Date: Jan 2010	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