I curve traced some JJ KT77 tubes and was impressed with the curves. Much better than the old data sheets.
I can't find my JJ KT77 triode curves at the moment, but they look just like these:
https://www.audiomatica.com/tubes/kt77.htm
UL mode curves there too. The KT77 definitely has better triode curves than the EL34. Have seen it commented on.
JJ datasheet: https://frank.pocnet.net/sheets/163/k/KT77.pdf
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UH-OH !! Warning! Warning!
Apparently the cheap Antec OT idea is --NOT-- working well in the Citation II clone thread. Only 21 Watts output using KT88 tubes.
The last time someone used an Antec OT here for a project, they only got 7 KHz bandwidth. Antec says on their website they have a NEW winding technique and show a frequency plot going past 20 KHz. Apparently the LF end has been sacrificed to get the HF end now. Not enough turns and/or not enough core area. We will have to await some xfmr testing to see what has transpired. And re-checking of the B+ and primary Z calculations used for the Amp, maybe an error there. Until someone gets a standard working Edcor / Hammond or similar OT to work at full power with the Citation II clone, I would not call this clone idea to be successful yet. Too bad. At least the HF stability for the global N FDBK seems to have been demonstrated, but then maybe not for an average working OT with more adequate turns.
Apparently the cheap Antec OT idea is --NOT-- working well in the Citation II clone thread. Only 21 Watts output using KT88 tubes.
The last time someone used an Antec OT here for a project, they only got 7 KHz bandwidth. Antec says on their website they have a NEW winding technique and show a frequency plot going past 20 KHz. Apparently the LF end has been sacrificed to get the HF end now. Not enough turns and/or not enough core area. We will have to await some xfmr testing to see what has transpired. And re-checking of the B+ and primary Z calculations used for the Amp, maybe an error there. Until someone gets a standard working Edcor / Hammond or similar OT to work at full power with the Citation II clone, I would not call this clone idea to be successful yet. Too bad. At least the HF stability for the global N FDBK seems to have been demonstrated, but then maybe not for an average working OT with more adequate turns.
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Designing and Building an amplifier that actually meets its specifications, is Both an Art and a Science.
The three oscilloscope manufacturers that built clones of Tektronix oscilloscopes (they built them at the request of the US government, who "promised to provide patent protection" for the 3 companies) . . . those oscilloscope clones never met the Tektronix specifications.
A real Citation II has one specification that we all would like to avoid . . . It causes Hernias.
The three oscilloscope manufacturers that built clones of Tektronix oscilloscopes (they built them at the request of the US government, who "promised to provide patent protection" for the 3 companies) . . . those oscilloscope clones never met the Tektronix specifications.
A real Citation II has one specification that we all would like to avoid . . . It causes Hernias.
Hi all,
Apologies for jumping into this thread, but just to recap what is the favoured circuit from the original question of what amp to build
Apologies for jumping into this thread, but just to recap what is the favoured circuit from the original question of what amp to build
gt6hudson,
Good Question!
Is your amplifier selection criteria exactly the same as the original poster.
Please re-read Post # 1 to verify that it is.
There are so many good amplifiers, but they have widely different capabilities.
What speakers will they drive?
Simple amp or Complex amp?
Teaching opportunity?
Push Pull?
Output Power; high power, medium power, or low power that has Finesse? (Example: a push pull 45 amplifier versus a push pull KT88 amplifier)
Please tell us about the rest of the audio equipment you will use with the amplifier.
That might get us started in a more focused direction.
Good Question!
Is your amplifier selection criteria exactly the same as the original poster.
Please re-read Post # 1 to verify that it is.
There are so many good amplifiers, but they have widely different capabilities.
What speakers will they drive?
Simple amp or Complex amp?
Teaching opportunity?
Push Pull?
Output Power; high power, medium power, or low power that has Finesse? (Example: a push pull 45 amplifier versus a push pull KT88 amplifier)
Please tell us about the rest of the audio equipment you will use with the amplifier.
That might get us started in a more focused direction.
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Hi 6A3sUMMER,
My criteria are on the same lines as the original post, my system is probably a little more budget. My background is also Electrical/Electronic Engineering, having studied Electrical/Electronics and then control systems at university back in the 90s...
My system is as 'wife' and cost friendly as possible, I'm trying to balance savings to retire with my need to build projects..
Speakers are a Bowers & Wilkins 607's stand mounted
I currently run a Audion Edison 60 with EL34B's and E88CC's with improved smoothing caps. I also run a LM3886, I use a ESP tone control pre amp for either power amps.
My other projects are mainly guitar amps and 100's of effects pedals.....
Complexity wise, I'm happy either way with a simpler design probably using a smaller component count and push pull. I'm not looking to power or supper finesse as I'm not ready to spend big time on speakers yet.... they will be my retirement present to myself....
I know my starting point probably should be to invest in speakers.....
My criteria are on the same lines as the original post, my system is probably a little more budget. My background is also Electrical/Electronic Engineering, having studied Electrical/Electronics and then control systems at university back in the 90s...
My system is as 'wife' and cost friendly as possible, I'm trying to balance savings to retire with my need to build projects..
Speakers are a Bowers & Wilkins 607's stand mounted
I currently run a Audion Edison 60 with EL34B's and E88CC's with improved smoothing caps. I also run a LM3886, I use a ESP tone control pre amp for either power amps.
My other projects are mainly guitar amps and 100's of effects pedals.....
Complexity wise, I'm happy either way with a simpler design probably using a smaller component count and push pull. I'm not looking to power or supper finesse as I'm not ready to spend big time on speakers yet.... they will be my retirement present to myself....
I know my starting point probably should be to invest in speakers.....
gt6hudson,
Those B&W 607 are good speakers.
Although they are nominally rated at 8 Ohms, they, like most B&W speakers, do have much lower minimum impedance versus their specification.
If you take a DMM, and measure the DCR across the speaker 5 way binding posts, I would guess you get somewhere between 3 Ohms to 5.5 Ohms.
Take care to check the DMM reading with tightly contacting shorted leads, and then with tight connections to the 5 way binding posts.
Please let me know the DCR reading you get.
From 20Hz to 35Hz, and a range between 150 and 350Hz, the minimum impedance will be Equal to the DCR. Very typical.
Try connecting the speakers to the 4 Ohm tap. Listen. Fun!
WAF . . . Wife Acceptance Factor. It is really not a bad thing, my wife used to keep me steady and straight ahead; but I had good stereo setups then.
Now, having been divorced for 40 years, my systems are whatever I feel I can afford, and however I like to set them up.
My ProAc 2000 Signature Tablettes (with my crossover modification) sit out about 30% into the room dimension. Few reflections, more direct sound.
I use a JBL 12 inch powered subwoofer for low bass. My Marantz CD player with XLR balanced outputs goes to my Balanced 5881 PP mono-blocks.
I have never heard better sound from any of my systems over the decades.
My excuse for purchasing the ProAcs (half true, but half lust), was to use the loudspeakers to develop the best sounding tube amps that I could.
Have fun designing, developing, building, and listening!
Those B&W 607 are good speakers.
Although they are nominally rated at 8 Ohms, they, like most B&W speakers, do have much lower minimum impedance versus their specification.
If you take a DMM, and measure the DCR across the speaker 5 way binding posts, I would guess you get somewhere between 3 Ohms to 5.5 Ohms.
Take care to check the DMM reading with tightly contacting shorted leads, and then with tight connections to the 5 way binding posts.
Please let me know the DCR reading you get.
From 20Hz to 35Hz, and a range between 150 and 350Hz, the minimum impedance will be Equal to the DCR. Very typical.
Try connecting the speakers to the 4 Ohm tap. Listen. Fun!
WAF . . . Wife Acceptance Factor. It is really not a bad thing, my wife used to keep me steady and straight ahead; but I had good stereo setups then.
Now, having been divorced for 40 years, my systems are whatever I feel I can afford, and however I like to set them up.
My ProAc 2000 Signature Tablettes (with my crossover modification) sit out about 30% into the room dimension. Few reflections, more direct sound.
I use a JBL 12 inch powered subwoofer for low bass. My Marantz CD player with XLR balanced outputs goes to my Balanced 5881 PP mono-blocks.
I have never heard better sound from any of my systems over the decades.
My excuse for purchasing the ProAcs (half true, but half lust), was to use the loudspeakers to develop the best sounding tube amps that I could.
Have fun designing, developing, building, and listening!
Hi 6A3sUMMER,
Apologies for my late reply, I had to find a little bit of spare time, today is a Bank Holiday for me so I set to to determine the impedance (Z) for my B&W speaker.
As I did'nt want to separate the drivers from the cross over etc, my readings are all from the binding posts with the links inplace linking the mid range driver to the tweeter .
DCR is the purely resistive value as speaks have a inductance I've measured and calculated the impedance 1st with a resistor in series measuring the voltage across the resistor and across the speaker through a frequency sweep 0Hz upto 400Hz. this allowed be to determine the current and then the impedance.
Just to play around a little further I then used REW software to run a frequency sweep to again calculate impedance.
I've determined that the free space resonance (Fs) where the voice coil is vibrating with maximum peak to peak amplitude is 30Hz and 80Hz
I've included my excel plot of the dynamic profile as well as the REW results , I've not gone on to calculate the Thiele Small measurements as I think I would need to disconnect the cross overs.
I know this thread is'nt a speaker discussion but if I've got my calculations correct I would be interested in people thoughts and is there a optimum Push Pull amp for these speakers...
Apologies for my late reply, I had to find a little bit of spare time, today is a Bank Holiday for me so I set to to determine the impedance (Z) for my B&W speaker.
As I did'nt want to separate the drivers from the cross over etc, my readings are all from the binding posts with the links inplace linking the mid range driver to the tweeter .
DCR is the purely resistive value as speaks have a inductance I've measured and calculated the impedance 1st with a resistor in series measuring the voltage across the resistor and across the speaker through a frequency sweep 0Hz upto 400Hz. this allowed be to determine the current and then the impedance.
Just to play around a little further I then used REW software to run a frequency sweep to again calculate impedance.
I've determined that the free space resonance (Fs) where the voice coil is vibrating with maximum peak to peak amplitude is 30Hz and 80Hz
I've included my excel plot of the dynamic profile as well as the REW results , I've not gone on to calculate the Thiele Small measurements as I think I would need to disconnect the cross overs.
I know this thread is'nt a speaker discussion but if I've got my calculations correct I would be interested in people thoughts and is there a optimum Push Pull amp for these speakers...
gt6hudson,
No, I am not suggesting that anyone open the loudspeaker enclosure,
and even for an open baffle enclosure, I am not suggesting the disconnecting of the drivers from the crossover.
Measuring the DCR of the loudspeaker input terminals is the 2nd easiest test of likely minimum impedance that a loudspeaker might present to the amplifier.
The easiest test of a loudspeaker impedance, is to diligently search for a review of the loudspeaker that includes a graph of the impedance test.
When I had access to the $50,000 Rohde & Schwarz vector network analyzer, the $10,000 precision cal kit, and the DC return loss bridge, it was so easy to test the impedance from 10Hz to way beyond audio frequencies, if I wanted to test that high.
Now I manually test loudspeaker's impedance, much more labor intensive.
But I always start with DCR of the terminals on the back of the enclosure.
Generally, at all the frequencies where the current and voltage are in phase, the impedance is Either at a Maximum, Or at a Minimum.
That makes it easy to find most of the likely suspects, just roll the signal generator frequency slowly to find those impedance points.
No, I am not suggesting that anyone open the loudspeaker enclosure,
and even for an open baffle enclosure, I am not suggesting the disconnecting of the drivers from the crossover.
Measuring the DCR of the loudspeaker input terminals is the 2nd easiest test of likely minimum impedance that a loudspeaker might present to the amplifier.
The easiest test of a loudspeaker impedance, is to diligently search for a review of the loudspeaker that includes a graph of the impedance test.
When I had access to the $50,000 Rohde & Schwarz vector network analyzer, the $10,000 precision cal kit, and the DC return loss bridge, it was so easy to test the impedance from 10Hz to way beyond audio frequencies, if I wanted to test that high.
Now I manually test loudspeaker's impedance, much more labor intensive.
But I always start with DCR of the terminals on the back of the enclosure.
Generally, at all the frequencies where the current and voltage are in phase, the impedance is Either at a Maximum, Or at a Minimum.
That makes it easy to find most of the likely suspects, just roll the signal generator frequency slowly to find those impedance points.