thank you! Because of your useful sharing for those who are new to assembling amps like us, wish you good health and look forward to receiving more useful shares from you, dear!
Very good presentation! I agree with you totally that the 1K signal is a good frequency to test OTs. It is a happy medium between the log rhythmic, scale of frequency impedance, vs., the output voltage stability of the signal generator. Hopefully, folks understand your choice in using 1vpp measurement step, to make the turns-ratio math extremely easy to do. :)
You test your output transformers the exact same way I do. Made more sense to me to put a higher frequency tone into it than using 60Hz. I will run my generator to sweep from 20Hz-10Khz just to see how much Db drops with higher frequency. I mainly deal with guitar amp parts so the aren’t none for high fidelity. Nice video. Like the Tek scope. I have an early digital 2430A and a nice old 485. Also have the Rigol DS 1054z which is great for all the readout options it has with a FFT function. Have an old 20Mhz two channel that came with the NRI home study course I did in 1992. I love repairing old test gear too so I have acquired a ridiculous amount of scopes and meters. Not Mr. Carlsons Lab crazy but might if I had the room. I guess I need to start doing repair videos. Used to put up guitar playing videos but the copyright nonsense stopped me 10 years ago. Still have a lot still up but nothing in a long time. Still love playing but really love working on tube gear. Keep up the great work.
The analog discovery 2 with the audio analyzer suite is a fun kit to play with and gives a quick snapshot of what an amp is doing across a wide range of operating conditions. It's not lab quality for sure, but I think it fine for use with tube amps :) And yeah, you should make some test gear repair videos! I fear at some point this old tek scope is gonna need an overhaul.
@@SkunkieDesignsElectronicsHi, I have a big problem and I don't understand what happen. I am fixing an exotic amplifier, this amp use one 845 output tube in single ended configuration. Company refuse to sales a new one OT. I have one amplifier in good working condition and the other one have the OT in shortcircuit. The thing is the next, good transformer read 500 Kohms in the primary, bad one 200 ohms. How is posible 500 kohms in the primary? Second mistery, I test the OT with 3 difefent multimeters, one is a Fluke 28ii reading 500 kohms. Using an analog multimeter OT reads 250 Kohms Using an analog multimeter with fet input reading is 300 Kohms. Any help will be appreciate. I want to adapt another OT but I don't know how to choice a right option. Sorry for my english. Best Regards.
The way I think about impedance is that it is frequency dependent. That's why the impedance noted on a speaker is a nominal impedance across a range of frequencies.
Yup. Like many things, it's a complex subject and a deep rabbit hole. I find for myself it's best to grasp a basic understanding and then expand it as needed. Some of the super complex stuff, for a tube amp in audio use, just makes it all very confusing and people just throw up their hands. :)
I'm not planning to use it in any of my builds, at least not for now. I think there are better places to spend money, at least in my system. Like using silver connection wire, just go with 18ga solid copper and IMHO that's plenty low loss.
Help needed! How do I match impedance of inverter16v AC output SOURCE to 16vAC isolation transformer primary, that I have to hand WIND, for 4 ohms load of 32v AC 6 amps secondary ? Do I use the ohms of primary 16v + 12 amps division or the resistance .06 ohms of inverter output contacts terminals at 20khz frequency? Voltage and turns ratio same as 1:2. The online formula for inductance value of turns requires reactance value in ohms , at the frequency of source.
Enjoyed your video. I've been dealing with a friend's 1939 Recording King amp, that has an OT with no markings of any kind on it, and trying to determine if its correct for this PP cathode biased amp running two 6L6GC's. He's using an 8 ohm speaker. I'm a bit of a novice, but I have some experience with tube amps. I have determined that this OT has a voltage ratio of 48;1 and thus and Impedence Ratio of about 2300:1. The plate to cathode voltage is 369 VDC, and using a Eurotubes single tube adapter, one tube has a PC of 51.6ma and the other tube is 57.6ma. The cathode resistor is 229 ohms, and its voltage drop is 25.82 VDC. So, if I"m correct, an 8 ohm speaker would result in a reflective impedence value of about 18,400 ohms. I have no idea what the Wattage of this OT is. 18.4K seems awfully high, and I don't know if it's too high for these tubes, or if there is such a thing a being "too high". The tube spec sheet I think shows Effective Load Resistance Plate-to-Plate of 6600 ohms. So that's a big spread. Thoughts? Can an OT harm the tubes or the speaker, or does it just affect the sound? Thanks for your help.
Where were you measuring? From anode to anode or center to anode? Honestly I haven't measured a PP transformer before. 1/2 of what you calculated sounds closer to what it probably is anode to anode.
I removed the output tubes and of course unplugged the amp, then I injected 1 VAC on the two secondary Output leads coming from the OT that connect to the speaker (no speaker was connected), and then I read the AC Voltage on the Blue and Brown leads on the Primary of the OT that are coming from the Plates of the 6L6's. That showed 48 VAC, so a 48:1 voltage ratio. Then squared that number and multiplied it by 8 ohms to get the Impedence ratio. of 18.4K ohms.
OK looking at this I think what is going on is this amp was designed for a 4 ohm speaker. Then you get 9K a-a which sounds more reasonable for a 6L6GC. Running 8 ohms speakers on this will just have a good bit lower power/SPL. Also if the amp is pentode or triode strapped could change the required a-a loading. I'm far from an expert on PP amps...
very good clip to help understand more about output transformer. Request how to calculate Load impedance for each tube. For Example why type 45 use 5K OPT? Why 2P29L use 4.6K on 32 ohms Headphone? Thank you in advance.
I think a lot comes down to recommendations and listening to people you trust. For example, a 300B is listed as working with a 3.5K OT, several people have said they believe a 5K sounds better and has less distortion, that unless you need every watt of power, go with a slightly higher Z OT. None of these tubes are new designs, learn from other people's mistakes :)
@@SkunkieDesignsElectronics Thank you very much. Yes 5K less distortion over 3K. However the point is any simple calculation to know which OPT to be a load line for tube?
hi skunky thanks for the video :) now i just have to figure out how to measure my output transformers i have 1 lead tied to the plate of a 6bm8 on the primary and 4 leads on the secondary 2 wire for speaker one ground and a yellow wire going to a 50uf 200v can cap in the power supply section im deconstruting a philips console picked a tricky one to learn off of :)
hi, your method works if you know the leads on the transformer but if you dont know what color lead is 4,8,or 16 ohm on the secondary youre in trouble ,we know that the black lead is the ground lead ,but brown ,yellow and green which is 4,8 or 16 ohms
You cam make a pretty accurate determination measuring with a simple ohm meter. 4 ohm will have less resistance than the 8 or the 16 due to the fewer windings the 4 ohm will have. Same with figuring out which is the screen tap.
hi i know i dont find impedance with multimetere ,I inject a 10vac with my variac and measure the voltage to the secondary ex. if i obtain .6 v secondary so 10/,6 =16.6 square i got 275.5 and if i multiply this by 8 ohm =2024 ohms primary but this way dont tell me if i must multiply by 4,8,or 16 ohms this tell me only on the transformation report.@@SkunkieDesignsElectronics
What I don't understand is, if the impedance on the load side is reflected to the input side, how can we measure accurately without having matched source and load impedances connected?
Because we aren't "measuring" the impedance (z) directly. We are measuring the turns ratio of the transformer, then calculating the input side impedance from the known 8ohm impedance load. Directly measuring would require an Impedance Analyzer or an LCR, and yes, if you were directly measuring it you would need the load attached. But I believe the measuring will not work well on SE OPT, since to get the proper inductance it has to be measured with the proper DC current going through. I also think things like the inductance come into play? I've read people getting odd reading with some LCR type meters, this method is simple and is accurate. I think too, this exercise helps folks understand what is happening, the difference between impedance and resistance, and can be done with tools I own :)
voltage ratio equals the turns ratio. impedance ratio is that ratio squared. impedance seen by the output tube is output impedance times the impedance ratio. easy peasy
Just subscribe. Curious to know what is the impedance between 4 to 8 ohm taps, and 2 to 4 ohm, 2 to 8 ohms. I am a physics graduate with life long hobby in hifi electronics, now 67 years old vintage, yet never learned this William Lee Singapore
The impedance on an output transformer is based on reflecting the impedance of the load. The idea would be a 4 ohm load on the 4 ohm tap would via the turns ration reflect a specific impedance on the primary.
Love the straightforward, no BS simplified approach. Thank you!
Thanks for the class, the world needs more people like you. Greetings.
thank you! Because of your useful sharing for those who are new to assembling amps like us, wish you good health and look forward to receiving more useful shares from you, dear!
You're welcome :)
good video. very helpful. my cerwin vega speakers are 6 ohm and I just try both 4 and 8 ohm taps to pick which one sounds best to me.
Very good presentation! I agree with you totally that the 1K signal is a good frequency to test OTs. It is a happy medium between the log rhythmic, scale of frequency impedance, vs., the output voltage stability of the signal generator. Hopefully, folks understand your choice in using 1vpp measurement step, to make the turns-ratio math extremely easy to do. :)
You test your output transformers the exact same way I do. Made more sense to me to put a higher frequency tone into it than using 60Hz. I will run my generator to sweep from 20Hz-10Khz just to see how much Db drops with higher frequency. I mainly deal with guitar amp parts so the aren’t none for high fidelity. Nice video. Like the Tek scope. I have an early digital 2430A and a nice old 485. Also have the Rigol DS 1054z which is great for all the readout options it has with a FFT function. Have an old 20Mhz two channel that came with the NRI home study course I did in 1992. I love repairing old test gear too so I have acquired a ridiculous amount of scopes and meters. Not Mr. Carlsons Lab crazy but might if I had the room. I guess I need to start doing repair videos. Used to put up guitar playing videos but the copyright nonsense stopped me 10 years ago. Still have a lot still up but nothing in a long time. Still love playing but really love working on tube gear. Keep up the great work.
The analog discovery 2 with the audio analyzer suite is a fun kit to play with and gives a quick snapshot of what an amp is doing across a wide range of operating conditions. It's not lab quality for sure, but I think it fine for use with tube amps :) And yeah, you should make some test gear repair videos! I fear at some point this old tek scope is gonna need an overhaul.
@@SkunkieDesignsElectronicsHi, I have a big problem and I don't understand what happen.
I am fixing an exotic amplifier, this amp use one 845 output tube in single ended configuration.
Company refuse to sales a new one OT.
I have one amplifier in good working condition and the other one have the OT in shortcircuit.
The thing is the next, good transformer read 500 Kohms in the primary, bad one 200 ohms.
How is posible 500 kohms in the primary?
Second mistery, I test the OT with 3 difefent multimeters, one is a Fluke 28ii reading 500 kohms.
Using an analog multimeter OT reads 250 Kohms
Using an analog multimeter with fet input reading is 300 Kohms.
Any help will be appreciate.
I want to adapt another OT but I don't know how to choice a right option.
Sorry for my english.
Best Regards.
Thank you so much. Very clear and very well explain.
Glad it was helpful!
Gracias por tu enseñanza!!!
The way I think about impedance is that it is frequency dependent. That's why the impedance noted on a speaker is a nominal impedance across a range of frequencies.
Yup. Like many things, it's a complex subject and a deep rabbit hole. I find for myself it's best to grasp a basic understanding and then expand it as needed. Some of the super complex stuff, for a tube amp in audio use, just makes it all very confusing and people just throw up their hands. :)
@@SkunkieDesignsElectronics Yes, it's confusing, but that's what makes it so interesting to me. The challenge : )
Cute way to explain reflected impedance concept. Another video about damping factor could be "symmetrical".... 🖖
Great suggestion!
Have just liked this video because of the presentation of the woman 🥂🥂🥂🥂
Hi Skunky 😁
What are your thoughts on silver and where to use it in components for the best results?
I'm not planning to use it in any of my builds, at least not for now. I think there are better places to spend money, at least in my system. Like using silver connection wire, just go with 18ga solid copper and IMHO that's plenty low loss.
Thanks so much, very helpful and interesting:)
Help needed! How do I match impedance of inverter16v AC output SOURCE
to 16vAC isolation transformer primary, that I have to hand WIND, for 4
ohms load of 32v AC 6 amps secondary ? Do I use the ohms of primary 16v +
12 amps division or the resistance .06 ohms of inverter output contacts
terminals at 20khz frequency? Voltage and turns ratio same as 1:2. The
online formula for inductance value of turns requires reactance value in
ohms , at the frequency of source.
Sorry but honestly I have no idea. Try some folks at www.diyaudio.com/
Enjoyed your video. I've been dealing with a friend's 1939 Recording King amp, that has an OT with no markings of any kind on it, and trying to determine if its correct for this PP cathode biased amp running two 6L6GC's. He's using an 8 ohm speaker. I'm a bit of a novice, but I have some experience with tube amps. I have determined that this OT has a voltage ratio of 48;1 and thus and Impedence Ratio of about 2300:1. The plate to cathode voltage is 369 VDC, and using a Eurotubes single tube adapter, one tube has a PC of 51.6ma and the other tube is 57.6ma. The cathode resistor is 229 ohms, and its voltage drop is 25.82 VDC. So, if I"m correct, an 8 ohm speaker would result in a reflective impedence value of about 18,400 ohms. I have no idea what the Wattage of this OT is. 18.4K seems awfully high, and I don't know if it's too high for these tubes, or if there is such a thing a being "too high". The tube spec sheet I think shows Effective Load Resistance Plate-to-Plate of 6600 ohms. So that's a big spread. Thoughts? Can an OT harm the tubes or the speaker, or does it just affect the sound? Thanks for your help.
Sounds like your math or measuring may be off? I would just get it working and if it sounds good, call it a day :)
What part of my math or measuring do you think is off? 48 x 48 = 2304 x 8 = 18,432 or 18.4K ohms. That would help. Thanks.
Where were you measuring? From anode to anode or center to anode? Honestly I haven't measured a PP transformer before. 1/2 of what you calculated sounds closer to what it probably is anode to anode.
I removed the output tubes and of course unplugged the amp, then I injected 1 VAC on the two secondary Output leads coming from the OT that connect to the speaker (no speaker was connected), and then I read the AC Voltage on the Blue and Brown leads on the Primary of the OT that are coming from the Plates of the 6L6's. That showed 48 VAC, so a 48:1 voltage ratio. Then squared that number and multiplied it by 8 ohms to get the Impedence ratio. of 18.4K ohms.
OK looking at this I think what is going on is this amp was designed for a 4 ohm speaker. Then you get 9K a-a which sounds more reasonable for a 6L6GC. Running 8 ohms speakers on this will just have a good bit lower power/SPL. Also if the amp is pentode or triode strapped could change the required a-a loading. I'm far from an expert on PP amps...
Fantastic, Thank You!
Thanks for the video!
You're welcome!
very good clip to help understand more about output transformer. Request how to calculate Load impedance for each tube. For Example why type 45 use 5K OPT? Why 2P29L use 4.6K on 32 ohms Headphone? Thank you in advance.
I think a lot comes down to recommendations and listening to people you trust. For example, a 300B is listed as working with a 3.5K OT, several people have said they believe a 5K sounds better and has less distortion, that unless you need every watt of power, go with a slightly higher Z OT.
None of these tubes are new designs, learn from other people's mistakes :)
@@SkunkieDesignsElectronics Thank you very much. Yes 5K less distortion over 3K. However the point is any simple calculation to know which OPT to be a load line for tube?
hi skunky thanks for the video :) now i just have to figure out how to measure my output transformers i have 1 lead tied to the plate of a 6bm8 on the primary and 4 leads on the secondary 2 wire for speaker one ground and a yellow wire going to a 50uf 200v can cap in the power supply section im deconstruting a philips console picked a tricky one to learn off of :)
never mind i think i got it I'm just wondering if the windings are different in the type i have ?
Is it single ended or push pull? Do you have a link to the schematic?
@@SkunkieDesignsElectronics no i don't i made a schematic
it has a 6ca4 rectifier tube and one 6bm8 per channel so I'm guessing it single ended
ill try to send it to your main site
@@SkunkieDesignsElectronics i
hi, your method works if you know the leads on the transformer but if you dont know what color lead is 4,8,or 16 ohm on the secondary youre in trouble ,we know that the black lead is the ground lead ,but brown ,yellow and green which is 4,8 or 16 ohms
You cam make a pretty accurate determination measuring with a simple ohm meter. 4 ohm will have less resistance than the 8 or the 16 due to the fewer windings the 4 ohm will have. Same with figuring out which is the screen tap.
hi i know i dont find impedance with multimetere ,I inject a 10vac with my variac and measure the voltage to the secondary ex. if i obtain .6 v secondary so 10/,6 =16.6 square i got 275.5 and if i multiply this by 8 ohm =2024 ohms primary but this way dont tell me if i must multiply by 4,8,or 16 ohms this tell me only on the transformation report.@@SkunkieDesignsElectronics
Hi, i'm not good in english, but i need to measure solid state amp. Please make tutorial. Thank's
th-cam.com/video/vZdL6jmCJvE/w-d-xo.html
Thanks great explanation…i just need to buy a signal generator!!
example. my single ended 45 amplifier.delivers
Most speakers dip lower. It's usually best to er on the side of higher impedance if it's an option, the only downside is a little less power.
What I don't understand is, if the impedance on the load side is reflected to the input side, how can we measure accurately without having matched source and load impedances connected?
Because we aren't "measuring" the impedance (z) directly. We are measuring the turns ratio of the transformer, then calculating the input side impedance from the known 8ohm impedance load.
Directly measuring would require an Impedance Analyzer or an LCR, and yes, if you were directly measuring it you would need the load attached. But I believe the measuring will not work well on SE OPT, since to get the proper inductance it has to be measured with the proper DC current going through. I also think things like the inductance come into play? I've read people getting odd reading with some LCR type meters, this method is simple and is accurate.
I think too, this exercise helps folks understand what is happening, the difference between impedance and resistance, and can be done with tools I own :)
@@SkunkieDesignsElectronics OK, I see. Thanks for the explanation.
most keen
I want 40w output transformer data for El 84 tube amplifier so please help me
You shouldn't need a 40W for an EL84 based amp. 25W is still overkill.
voltage ratio equals the turns ratio. impedance ratio is that ratio squared. impedance seen by the output tube is output impedance times the impedance ratio. easy peasy
Well there is no real "output impedance", the transformer reflects the load impedance (speaker impedance) to the tube via the transformer turns ratio.
@@SkunkieDesignsElectronics yes
Show your signal gen.
I did a whole video on this, here is where I go over the scope and signal generator I use.
th-cam.com/video/rVpawaYzUus/w-d-xo.html
Just subscribe.
Curious to know what is the impedance between 4 to 8 ohm taps, and 2 to 4 ohm, 2 to 8 ohms.
I am a physics graduate with life long hobby in hifi electronics, now 67 years old vintage, yet never learned this
William Lee Singapore
The impedance on an output transformer is based on reflecting the impedance of the load. The idea would be a 4 ohm load on the 4 ohm tap would via the turns ration reflect a specific impedance on the primary.
@@SkunkieDesignsElectronics
Yes indeed tks, just curious is between 4 ohm to 8 ohm taps is 2 ohm. And if 2 ohm taps to 8 ohm is 4 ohm
No the impedance difference would be 4 ohms. going from 4 to 8. You can't measure it with an ohm meter.
@@SkunkieDesignsElectronics oh ok, so we cud still take the diff as 4 ohm against 8 ohm tap. Tks a lot for the advice !
Impedance takes a while to get your head around. I took a whole semester on it lol
Yeah it does, I feel like I just have a little grasp of it. :)
1v ac in test,,,, volume contrl is at max huh
The volume control isn't in the test loop.
First! :D
Yes you are!