Hi, SemperFi! Very interesting! You are really from Wake Island? According Wikipedia page it looks like Heaven on the earth!
Totally agree.
To a teeSome nights I end up searching the forum instead of sitting down with the soldering iron. I guess we all need some breaks though, so no sweat
Hi, SemperFi! You are really from Wake Island? According Wikipedia page it looks like Heaven on the earth!
QUOTE]
Hehe, nope. Fortunately! I've been there during a transit to Asia, and the bar offers $1 Heinekens
neonthecat
Thank You too! I am happy that you have enjoyed visiting the site.
I tried to make the site user friendly, such comments as your confirmed that it was succeeded.
Hi,
The Hammond 302AX model. It has two 2.5v windings, one each 6.3v and 5v.
Very useful for 2A3 amps.
THD measurements
Hi, Friends
Also a few words about new measurements.
For THD (total harmonic distortion) measurements I have used Digital USB Oscilloscope. It's very easy to use and is not picky about the computer resources, so as not to depend on the parameters of the audio card.
Its software include a spectral analyzer. Four Fast Fourier Transform (FFT) windows (Rectangular, Hamming, Hanning, and Blackman-Harris) are available to match an analyzed signal here. I have choosed the Blackman-Harris window, because it is better for periodic signals.
Test Conditions:
Input = CD (2V RMS), adjusted for 1 W output.
Test frequency = 1 kHz.
As a result I got (see attachments for details):
• 1.8% with 8 Ohm dummy load
• 2.5% with with Klipsch RF-15 speaker
Most significant term is 2rd harmonic (1.73% with dummy load and 2.43% with speaker), but 2nd harmonic is almost inaudible, since it is a full octave higher than the original musical spectra and is musically consonant. Odd harmonics (3rd, 5th, 6th, 7th and 9th) are very dissonant and ugly sounding, but fortunately they are small.
For further information please visit:
http://www.levelfive-audio.com/measurements.htm#thd
Screenshots with details (also THD for max undistorted output) are attached below.
Hi, Friends
Also a few words about new measurements.
For THD (total harmonic distortion) measurements I have used Digital USB Oscilloscope. It's very easy to use and is not picky about the computer resources, so as not to depend on the parameters of the audio card.
Its software include a spectral analyzer. Four Fast Fourier Transform (FFT) windows (Rectangular, Hamming, Hanning, and Blackman-Harris) are available to match an analyzed signal here. I have choosed the Blackman-Harris window, because it is better for periodic signals.
Test Conditions:
Input = CD (2V RMS), adjusted for 1 W output.
Test frequency = 1 kHz.
As a result I got (see attachments for details):
• 1.8% with 8 Ohm dummy load
• 2.5% with with Klipsch RF-15 speaker
Most significant term is 2rd harmonic (1.73% with dummy load and 2.43% with speaker), but 2nd harmonic is almost inaudible, since it is a full octave higher than the original musical spectra and is musically consonant. Odd harmonics (3rd, 5th, 6th, 7th and 9th) are very dissonant and ugly sounding, but fortunately they are small.
For further information please visit:
http://www.levelfive-audio.com/measurements.htm#thd
Screenshots with details (also THD for max undistorted output) are attached below.
Attachments
My experience exactly, and also to my chagrin. I no longer do this..
There are rare squares/cable ties however that can be bolted to the chassis and these should be ok provided the nylon does not get too hot.
Rare?
I have used standard Mouser position, available for ordering:
ABMS-A-C Panduit Cable Mounting & Accessories
Rare?
I have used standard Mouser position, available for ordering:
ABMS-A-C Panduit Cable Mounting & Accessories
Not rare, but obviously I am too lazy to bolt them down, and I did find that this type can loosen up as the double sided adhesive tape rots over time.. I had a bunch that are quite similar but do not have the screw hole in them.. Next time I will get some from Mouser..
Regarding the purpose of R6, I am more interested in what effects R6 has on the function of the SRPP circuit.
I see several possible effects;
Increased gain
Increased Power Supply Rejection Ratio
Decreased current through the circuit
Decreased voltage across the triodes in the envelope
Reduced output impedance
Effectively raises the plate resistance of the top triode
I am not convinced about the equalizing of AC voltage in triodes. Much of that depends on the connected load impedance.
R6 will have much the same effect as raising the value of the plate resistor in a grounded cathode.
There seems to be a lack of consensus about the function of the SRPP amplifier or should we say a lack of understanding. Levelfive you have it all dialed and adjusted. I need more words to understand.
The Panduits will not sink the ship.
DT
All Just for fun!
I see several possible effects;
Increased gain
Increased Power Supply Rejection Ratio
Decreased current through the circuit
Decreased voltage across the triodes in the envelope
Reduced output impedance
Effectively raises the plate resistance of the top triode
I am not convinced about the equalizing of AC voltage in triodes. Much of that depends on the connected load impedance.
R6 will have much the same effect as raising the value of the plate resistor in a grounded cathode.
There seems to be a lack of consensus about the function of the SRPP amplifier or should we say a lack of understanding. Levelfive you have it all dialed and adjusted. I need more words to understand.
The Panduits will not sink the ship.
DT
All Just for fun!
The purpose of R6.
Hello All,
Since I helped stir the pot I am back to share what I found out regarding the purpose of R6. The value of R6 can be adjusted under test or calculated if you know the mu, rp and gm of the tube at its bias point. The goal is to optimize the symmetry of the push pull nature of the SRPP circuit. Another way to put it is to maximize the AC voltage and current swing of the circuit. Move the value of R6 from this optimized condition will degrade the performance of the circuit. Not to mention PSRR, output impedance and all those other things.
DT
All Just For Fun!
Hello All,
Since I helped stir the pot I am back to share what I found out regarding the purpose of R6. The value of R6 can be adjusted under test or calculated if you know the mu, rp and gm of the tube at its bias point. The goal is to optimize the symmetry of the push pull nature of the SRPP circuit. Another way to put it is to maximize the AC voltage and current swing of the circuit. Move the value of R6 from this optimized condition will degrade the performance of the circuit. Not to mention PSRR, output impedance and all those other things.
DT
All Just For Fun!
Hi, Akita!
I have used Digital USB Oscilloscope. The oscilloscope is supplied with its own software winoscill (can run under Wine ver.1.1.42 in Linux). Its software includes a spectral analyzer tool. Four Fast Fourier Transform (FFT) windows (Rectangular, Hamming, Hanning, and Blackman-Harris) are available to match an analyzed signal here.
This choice was optimal for me, but there are many alternatives (and many devices), for example see the following thread: USB Oscilloscope
Regards, Konstantin
Level Five Schematic Revision
Hi, Friends!
After one year of listening the Level Five amplifier I decided to play around with the operating point of output tubes over again. As my colleague J.C. Morrison said: «Run your triodes hot!». So I tried to increase the idle current through the 2a3 tube.
The only thing that needs changed in the circuit it is the power supply and the bias. The biasing resistor R8 was reduced to 500 Ohm, and R2 resistor to 51 Ohm. These changes set the plate voltage at about 231V with the idle current 75mA. The 2A3C plate dissipates about 17.3 Watt, but this is ok for Shuguang 2A3C monoplates.
The rectifier tube in the power supply has to be replaced. I advise 5AR4 (5V4GA as alternative, see Upgrades page) instead 5U4GB. Its forward drop is less than a 5U4GB and so have a higher output. Warm-up time is about 30 seconds which is greater than the warm-up time of the 2A3s.
Also I replaced the Audio Note AN-160 choke (10H@125mA) by a Lundahl LL1673 (10H@200mA). This replacement gave me the desired headroom for idle current draw, that protects the choke from the saturating.
Measurements showed that the linearity of the output stage has improved more than twice! As a result I got:
For further information please visit:
http://www.levelfive-audio.com/upgrades.htm#revision-a
Screenshots with details (also THD for max undistorted output) and revisited schematic are attached below.
Warm Regards, Konstantin.
Hi, Friends!
After one year of listening the Level Five amplifier I decided to play around with the operating point of output tubes over again. As my colleague J.C. Morrison said: «Run your triodes hot!». So I tried to increase the idle current through the 2a3 tube.
The only thing that needs changed in the circuit it is the power supply and the bias. The biasing resistor R8 was reduced to 500 Ohm, and R2 resistor to 51 Ohm. These changes set the plate voltage at about 231V with the idle current 75mA. The 2A3C plate dissipates about 17.3 Watt, but this is ok for Shuguang 2A3C monoplates.
The rectifier tube in the power supply has to be replaced. I advise 5AR4 (5V4GA as alternative, see Upgrades page) instead 5U4GB. Its forward drop is less than a 5U4GB and so have a higher output. Warm-up time is about 30 seconds which is greater than the warm-up time of the 2A3s.
Also I replaced the Audio Note AN-160 choke (10H@125mA) by a Lundahl LL1673 (10H@200mA). This replacement gave me the desired headroom for idle current draw, that protects the choke from the saturating.
Measurements showed that the linearity of the output stage has improved more than twice! As a result I got:
- 0.7% with 8 Ohm dummy load
- 1.1% with with Klipsch RF-15 speaker
For further information please visit:
http://www.levelfive-audio.com/upgrades.htm#revision-a
Screenshots with details (also THD for max undistorted output) and revisited schematic are attached below.
Warm Regards, Konstantin.
Attachments
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