26 preamp problem

NickC · 5th February 2006, 10:28 AM

I made a preamp actually a 26 preamp.
However when i hooked it up it buzzes not hum(50hz or 100hz). How do i get
rid of this buzzing. ITs rather annoying. Sound is good though.

Preamp is like this.
Separate power supply feeding 300V and 0 V and battery supplying 6.3 volts and 0 volts. THis feeds into the 26 preamp.
THe preamp has a ccs and another ccs feeding gas diodes. Like gary pimm stuff
Grounding is done at incoming rca input single point.
The output is a mufollower feeding a C-core preampoutput trans. This is grounded to rca input too.

I have not twisted the fillament wires yet and shield it as well as the B+ wires. WOuld this help?
ANy suggestion to how remove the buzzes?

Cheers
Nicholas

jamesjung21 · 5th February 2006, 11:17 AM

Just to remind you that 26 requires 1.5V not 6.3V

Please don't tell me that you tortured a globe

Original Burnedfingers · 5th February 2006, 11:19 AM

Quote:

Just to remind you that 26 requires 1.5V not 6.3V

Too much heater and you hear a ting and the bas***d is gone.

I'm sure he knows it

Its just a typo

Original Burnedfingers · 5th February 2006, 11:24 AM

Check out my thread. There is some good information there even if no one bothered to address the original question. Kevin was good enough to supply information on his #26 tube line stage which has prompted me to bid on a set of used high dollar UTC HA 133 transformers that I will never get.

Check out this thread.....Aikido using a #26 tube?

NickC · 5th February 2006, 12:04 PM

It was used with a ccs.
I grounded one end of the fillament. That help to lower the buzz. But the buzz come and goes and so is the intensity. From time to time the buzz goes tolerable to loud.

Thanks

arnoldc · 5th February 2006, 10:25 PM

if you haven't yet- www.vt52.com

kevinkr · 12th February 2006, 08:23 PM

Do you have grid stopper resistors on the 26? (1K works fine right at the grid pin) The erratic buzzing noises you seem to be describing are often a symptom of oscillation. Also check the CCS's to make sure that they are not oscillating.

I have used the 26 in a number of designs and it is quite prone to pick up external fields due to the large surface area of the plate and the relatively high rp.. I shield mine with shields I made out of fairly thin brass sheet formed into a circle and soldered together, this slides onto the envelope of the tube and grounds to the chassis.

andyjevans · 13th February 2006, 01:12 PM

I have not twisted the fillament wires yet and shield it as well as the B+ wires. WOuld this help?>

YES - you must do that. I found that out with my 26 preamp. Big difference.

5th February 2006, 10:28 AM	#1
NickC diyAudio Member Join Date: Dec 2001 Location: Earth	26 preamp problem I made a preamp actually a 26 preamp. However when i hooked it up it buzzes not hum(50hz or 100hz). How do i get rid of this buzzing. ITs rather annoying. Sound is good though. Preamp is like this. Separate power supply feeding 300V and 0 V and battery supplying 6.3 volts and 0 volts. THis feeds into the 26 preamp. THe preamp has a ccs and another ccs feeding gas diodes. Like gary pimm stuff Grounding is done at incoming rca input single point. The output is a mufollower feeding a C-core preampoutput trans. This is grounded to rca input too. I have not twisted the fillament wires yet and shield it as well as the B+ wires. WOuld this help? ANy suggestion to how remove the buzzes? Cheers Nicholas

12th February 2006, 08:23 PM	#7
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Do you have grid stopper resistors on the 26? (1K works fine right at the grid pin) The erratic buzzing noises you seem to be describing are often a symptom of oscillation. Also check the CCS's to make sure that they are not oscillating. I have used the 26 in a number of designs and it is quite prone to pick up external fields due to the large surface area of the plate and the relatively high rp.. I shield mine with shields I made out of fairly thin brass sheet formed into a circle and soldered together, this slides onto the envelope of the tube and grounds to the chassis. __________________ www.kta-hifi.net

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5th February 2006, 11:17 AM	#2
jamesjung21 diyAudio Member Join Date: Dec 2003 Location: New Zealand	Just to remind you that 26 requires 1.5V not 6.3V Please don't tell me that you tortured a globe

5th February 2006, 11:19 AM	#3
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Quote: Just to remind you that 26 requires 1.5V not 6.3V Too much heater and you hear a ting and the bas***d is gone. I'm sure he knows it Its just a typo

5th February 2006, 11:24 AM	#4
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Check out my thread. There is some good information there even if no one bothered to address the original question. Kevin was good enough to supply information on his #26 tube line stage which has prompted me to bid on a set of used high dollar UTC HA 133 transformers that I will never get. Check out this thread.....Aikido using a #26 tube?

5th February 2006, 12:04 PM	#5
NickC diyAudio Member Join Date: Dec 2001 Location: Earth	It was used with a ccs. I grounded one end of the fillament. That help to lower the buzz. But the buzz come and goes and so is the intensity. From time to time the buzz goes tolerable to loud. Thanks

5th February 2006, 10:25 PM	#6
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	if you haven't yet- www.vt52.com

13th February 2006, 01:12 PM	#8
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	I have not twisted the fillament wires yet and shield it as well as the B+ wires. WOuld this help?> YES - you must do that. I found that out with my 26 preamp. Big difference.

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