Stereo Tube Amplifier

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Weslee Kinsler 270,225 3 15
The circuit is simple, yet is capable of excellent performance. I designed it specifically for use as an amplifier for the digital sound card in my computer. Audio input can be from any two-channel line level device such as a television, CD player, or VCR. It is of the tube type, using only 5 tubes total with no more than about 45 Watts power consumption from the outlet. It uses 3 types of tube 1 5Y3 GT vacuum rectifier, 2 6SF5 GT high-mu triodes, and 2 6K6 power beam amplifiers. These are all full-size octal type tubes which are commonly available today for between $3-5 each.


Schematic for tube amp


Total Qty.
R1, R10, R1362.2Meg Pot
R22470K 1/2W Resistor
R321 Meg 1/2W Resistor
R42220K 1/2W Resistor
R52330 Ohm 2W Resistor
R62220K 1/2W Resistor
R722.2Meg 1/2W Resistor
R821Meg 1/2W Resistor
R91720 Ohm 20W Resistor
R11233K 1/2W Resistor
R12222K 1/2W Resistor
C1, C940.005uF 400V Capacitor
C220.05uF 600V Capacitor
C3220uF 25V Electrolytic Capacitor
C420.01uF 400V Capacitor
C52200uuF 400V Ceramic Disc Capacitor
C6, C7215uF 450V Capacitor
C8215uF 400V Capacitor
T11117V Primary, 350VCT Secondary, 6.3V Secondary, 6.3V Secondary
T227600 Ohm Primary, 4 or 8 Ohm Secondary
SW11SPST Switch
SP1, SP2212" or smaller, 4 or 8 ohm speakers
MISC15 tube sockets, 2 RCA jacks, PC board or chassis, wire, knobs, etc.


  1. Email Weslee Kinsler with questions, comments, etc.
  2. The 6V6 GT tube may be substituted for the 6K6 to lower power requirements.
  3. C8 is for radio interference suppression and may be omitted.
  4. The 5Y3 GT tube should be mounted in a vertical position and be well ventilated. The 6K6 and 6SF5 tubes can be mounted in any position.
  5. Controls should have an audio taper.
  6. The power supply portion of this unit may be used for anything requiring 290-320v DC up to about 3 amps.
  7. The author has provided a link to an updated version of this circuit. The newer revision contains parts changes based on the author's tinkering and experience with the circuit over the past few years.

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Stereo Tube Amplifier
Thursday, June 09, 2011 2:10:53 AM
"The power supply portion of this unit may be used for anything requiring 290-320v DC up to about 3 amps." Big mistake here: The 5Y3 is rated at 125mA. 3A will have the plates glowing red and shorting out in no time to say nothing of the power transformer.
Stereo Tube Amplifier
Thursday, June 09, 2011 2:07:40 AM
Here's an obvious mistake: Where's the grid return resistors for the 6SF5's? The grids will float at an indeterminate voltage. What should have been done of course is to place C1 at the input to the volume control instead. Secondly, gain is needlessly being lost with R2. R3 is unnecessary. Pin 3 of the 6SF5 has 120V?? I think you mean pin 5. The resistor values around the volume control are higher than need be and will only contribute to noise. For an amp like this, use a 500K pot. The values of resistors around the loudness control are very strange.
Stereo Tube Amplifier
Wednesday, January 20, 2010 2:16:35 PM
I want to modify the power supply so it can be used for 220 - 240 vac like that we use in Europe.
Stereo Tube Amplifier
Friday, September 18, 2009 2:20:06 PM
does it works at 50 Hz of voltage input?
Stereo Tube Amplifier T1
Thursday, July 09, 2009 11:50:48 PM
if I can't find the T1 you specified, can i use two transformers for the primary. IE: 0ne 117V Primary, 350VCT Secondary and, One 117V Primary, 6.3V Secondary. Also what is the wattage output of this amp
Stereo Tube Amplifier
Wednesday, October 08, 2008 1:18:28 PM
i can replace the tube 5Y3GT by placing two 1N4007 1kv diodes or some else 8w diodes for this amp to save some W to the circuit to heat that tube?
Stereo Tube Amplifier
Friday, July 25, 2008 5:51:39 PM
hey everybody where can i get parts antique electronic supplu or what I do not have much money so I need cheap parts not bad parts but not expensive parts....
Stereo Tube Amplifier
Sunday, December 02, 2007 6:47:16 AM
Plaese Use 0.1mf ok
Stereo Tube Amplifier
Sunday, November 04, 2007 1:36:51 AM
can u explain how the tube connected???? i like your project...i need to understand more.. can u explain to me....
Stereo Tube Amplifier
Wednesday, August 15, 2007 11:08:02 AM
Transformer T1 is specified as having two 6.3V secondaries, but shouldn't the secondary connected to the 5Y3 rectifier be 5 volts? Also, "C8" is shown in two places and has a value of 15uF@400V. 15uF seems like an extraordinarily high value for these capacitors, which are sometimes used for line-noise suppression (and not a recommended method, because they usually just add more noise contamination to the ground). More usual values for these capacitors are 0.001uF high-voltage (1KV) ceramic disc types, but I recommend that you leave them out if there is no line noise problem to begin with. Also, put a suitable fuse before S1 for fire protection, notate the schematic so that the right side of the plug is "N" for neutral, and include a three-prong plug with a earth safety ground tied to the chassis. The combination of no ground along with the presence of either or both C8s may cause an immediate lethal shock hazard.
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