OPT is Output Transformer; OutPut Transformer
Want a relatively simple tube amplifier that Might work at first power-up?
Use an OPT.
Want a relatively difficult tube amplifier that might Not work at first power-up?
Build an OTL amplifier (Output Transformer Less).
Unless you are an excellent builder, use an excellent design, and know all the hints and kinks that are special case about OTL amplifiers,
you will have difficulties.
Other's Mileage May Vary.
Just my opinions.
Want a relatively simple tube amplifier that Might work at first power-up?
Use an OPT.
Want a relatively difficult tube amplifier that might Not work at first power-up?
Build an OTL amplifier (Output Transformer Less).
Unless you are an excellent builder, use an excellent design, and know all the hints and kinks that are special case about OTL amplifiers,
you will have difficulties.
Other's Mileage May Vary.
Just my opinions.
I am sticking with the original design which calls for an output transformer of:
25W, SE OPT - 5K with 43% screen tap
And power transformer of either:
110/120v primary and 760v w/ CT (360-0-360) at 180mA, 5v at 3 amps and 6,3v at 4 amps secondary
110/120v and 760v w/ CT (380-0-380) at 200mA, 5v at 3 amps and 6,3v at 4 amps secondary.
Ever heard of Pacific Audio?
Which I do appreciate! 🙂
If your speakers are 97dB/W-M, then...
1W - 97dB 1M away from the speaker
2W - 100dB
4W - 103dB
8W - 106dB
Etc...
Every doubling of power is an additional 3dB spl.
For reference, OSHA states that at 90dB one could be exposed for up to up to 8 hrs per day.
97dB is loud, 106 is way loud, 115 is considered the "threshold of pain".
8W into a set of 96dB/W-M speakers in a moderate sized living room make it difficult to carry on a conversation.
1W - 97dB 1M away from the speaker
2W - 100dB
4W - 103dB
8W - 106dB
Etc...
Every doubling of power is an additional 3dB spl.
For reference, OSHA states that at 90dB one could be exposed for up to up to 8 hrs per day.
97dB is loud, 106 is way loud, 115 is considered the "threshold of pain".
8W into a set of 96dB/W-M speakers in a moderate sized living room make it difficult to carry on a conversation.
If your main-woofer mid-range speaker is 97 dB sensitivity
And your tweeter is 87 dB to 89 dB sensitivity, then . . .
You probably need to:
Either Bi-Amp to make up for the 8 to 10 dB difference in Main to Tweeter sensitivity;
Or use a tweeter that is as sensitive or more sensitive as the Main speaker.
You can resistively pad down a tweeter sensitivity, but it is not a good idea to have to resistivly pad down a Main woofer-mid range speaker (and padding the Main speaker is a real waste of power (generally there is more music power at low frequencies versus very high frequencies).
There are lots of compression driver tweeters with horn loading that are more than 97 dB sensitive.
Oh, darn, those tweeters high frequencies roll off before 20kHz . . . Does anybody care about that unless they are younger than 25 years old.
Have you had your hearing tested lately? Good luck?
How much musical harmonics are there at 20kHz, unless it is from clipping the amplifier?
If you need more than 10 watts for a 97dB sensitive speaker, you might want to have your hearing checked (or you just want Saint Saens Organ Symphony to rattle the walls and floor). Your horn loaded Main speakers are not going to properly reproduce the 6Hz Canon Shot on Telarc's definitive recording of the 1812 overture.
Just my opinions
I am curious about the speaker system you are getting.
Can you give a link or two?
And your tweeter is 87 dB to 89 dB sensitivity, then . . .
You probably need to:
Either Bi-Amp to make up for the 8 to 10 dB difference in Main to Tweeter sensitivity;
Or use a tweeter that is as sensitive or more sensitive as the Main speaker.
You can resistively pad down a tweeter sensitivity, but it is not a good idea to have to resistivly pad down a Main woofer-mid range speaker (and padding the Main speaker is a real waste of power (generally there is more music power at low frequencies versus very high frequencies).
There are lots of compression driver tweeters with horn loading that are more than 97 dB sensitive.
Oh, darn, those tweeters high frequencies roll off before 20kHz . . . Does anybody care about that unless they are younger than 25 years old.
Have you had your hearing tested lately? Good luck?
How much musical harmonics are there at 20kHz, unless it is from clipping the amplifier?
If you need more than 10 watts for a 97dB sensitive speaker, you might want to have your hearing checked (or you just want Saint Saens Organ Symphony to rattle the walls and floor). Your horn loaded Main speakers are not going to properly reproduce the 6Hz Canon Shot on Telarc's definitive recording of the 1812 overture.
Just my opinions
I am curious about the speaker system you are getting.
Can you give a link or two?
TheGimp,
You said:
"For reference, OSHA states that at 90dB one could be exposed for up to up to 8 hrs per day."
Suppose that is an industrial work area with 90dB noise that is concentrated to a narrow band of frequencies (many industrial noises are that way).
That will allow the workers to keep on working, but soon there will be a few cilia fibers in the inner ear that are destroyed.
Cilia can Not be repaired, replaced, or healed!
Not my ears!
Trust and Verify.
Just my opinions, and just my useless right ear!
You said:
"For reference, OSHA states that at 90dB one could be exposed for up to up to 8 hrs per day."
Suppose that is an industrial work area with 90dB noise that is concentrated to a narrow band of frequencies (many industrial noises are that way).
That will allow the workers to keep on working, but soon there will be a few cilia fibers in the inner ear that are destroyed.
Cilia can Not be repaired, replaced, or healed!
Not my ears!
Trust and Verify.
Just my opinions, and just my useless right ear!
🤯 😳
Yet another example of not everything on the internet is correct. Big duh moment for me. Clearly I been led astray and wasted a couple days of research (well, not like can do much else, this influenza has made me really weak). So the better option be the 300 watt speakers?
Why then did half volume of a 75 watt amplifier blow 20 watt speakers?
Here I been thinking the watts needed to be increased for the replacement speakers and if understanding correctly, instead need to come down.
Or 4 watt mono blocks?
8 watts is a 300B, hmmm... 🤔
By the way, Opa lost most of his hearing as a aircraft engineer in the early days of the jet age, so was ingrained in me how important hearing protection and not listening to loud levels. I didn't know how high the frequency test would go and now last few days been having weird hearing and occasional tinnitus (had it since I was about 12) in the right ear (my messed up one, family used Q tips including me, until damaged my ear, lost all hearing, then one day mostly came back, high pitch noises hurt far sooner than the left).
For your information only, this was discussed earlier, here is how the divider which folds the horn acts as a baffle that @AllenB had me generate.
His response to this was:
The plan which is unfolding is to use an active crossover, which then means bi-amping if recalling correctly.
Bi-amping also has the advantage of more adjustments and maybe even coloring (though desire is to be closer to neutral than warm, certainly not cool).
🤣 I really needed a good laugh, thank you. I am not laughing at you, the mental and auditory pictures it produces.
See, you two saved me from wasting money on unnessisary watts, good reason to go at a slow pace.
Which I really appreciate! 🙂
Appreciate the interest. 🙂 Here are the links:
https://www.diyaudio.com/community/threads/stereolithos-build-bib-for-full-bass.395109/
https://www.diyaudio.com/community/threads/can-someone-please-model-these-speakers.395169/
Totally agree! About two weeks ago replaced the hearing protection lost in the move. Instead of just buying anything, I bought the ones with the most protection.
OPT: OutPut Transformer. The most critical part determining the tube amplifiers performance.
Scavenging can work for power transformers - an old TV or other elecrronic instrument can provde a transformer that would otherwise cost more than $100. Also chassis and other parts if you're not too picky about appearance. More recent products can yield fuseholders, switches, other parts. I previously worked for two electronics manufacturers - when a project got canceled, excess parts got trashed - I have several lifetime's supply of resistors and capacitors. Vacuum tube public address amps were once cheap, but they're in demand as instrument amps. Still turn up occasionally at thrift shops.
KT-88s aren't cheap, but the circuit is relatively simple and can provide 10 watts or so single-ended.
Scavenging can work for power transformers - an old TV or other elecrronic instrument can provde a transformer that would otherwise cost more than $100. Also chassis and other parts if you're not too picky about appearance. More recent products can yield fuseholders, switches, other parts. I previously worked for two electronics manufacturers - when a project got canceled, excess parts got trashed - I have several lifetime's supply of resistors and capacitors. Vacuum tube public address amps were once cheap, but they're in demand as instrument amps. Still turn up occasionally at thrift shops.
KT-88s aren't cheap, but the circuit is relatively simple and can provide 10 watts or so single-ended.
I was thinking a different scavenging... Great point, though how do you know if getting anything useable?
I am more about function over form. I have even considered seeing if the amps fit a gutted Magnavox cabinet my Opa turned into a bookcase for Oma. I doubt any turntable could be fitted back in. Yes, the plywood back Opa attached have to be removed and replaced with pegboard for ventilation, I am aware how hot tubes run. Speaking of which.
I been doing a lot of research and found multiple sources which say the Kt-88 can be replaced by a EL-34 or EL-84. Turns out the EL tubes are European and absolutely love the sound of the Telefunken tubes in my consoles. Looking into the sound difference, it describes the American sound versus the British/European, I now have words to describe my preference for the latter. Plus, what is the point of the KT-88 if sounds like SS? Even better, they cost less.
As I understand, eight to 10 watts is about right for the system.
As for SET and triode PP, have read a couple sources saying the latter is more dynamic, is this correct?
kt
kt 88 is out of the league now , being beaten by chip amp and class d amp ,, still life now is 6v6 , el84 and dht
Definitely not EL84's. In a conservatively biased single ended amp you can certainly run the octal tubes listed in the video.
Check out George's SSE: http://tubelab.com/designs/tubelab-sse/
jeff
What about auto biasing?
What is conservatively biased?
That doesn't explain the why, does it?
After my response, I of course did a little digging and found this, now I understand (highlights already present):
Is this a dynamic amplifier?
Sometimes is pays to go backwards to go forwards. There are some great primers for tube technology on the web, or fork out for a book, many here swear by Morgan Jones 'Building Valve Amplifiers'.
Lenard Audio Institute - Valve Amps
There are so many degrees of freedom with tube types, topologies, budgets, presentations, you are not going to be able to make an informed decision unless you know the pros and cons of them all.
My way in to the hobby was researching for a PCB kit where I had the freedom to source my own components, and the parts were not exotic or overly expensive. I discovered the Tubelab SPP (very well supported on this site), used inexpensive Toroidy transformers, matched set of Russian 6P14P-EV tubes, and got to understand the important points of construction and a particular topology.
Lenard Audio Institute - Valve Amps
There are so many degrees of freedom with tube types, topologies, budgets, presentations, you are not going to be able to make an informed decision unless you know the pros and cons of them all.
My way in to the hobby was researching for a PCB kit where I had the freedom to source my own components, and the parts were not exotic or overly expensive. I discovered the Tubelab SPP (very well supported on this site), used inexpensive Toroidy transformers, matched set of Russian 6P14P-EV tubes, and got to understand the important points of construction and a particular topology.
You'll go mad & end up running around in circles till you disappear up your pipe trying to research audio online without any hands on practical experience if your not careful : ) In my experience as regards home audio if you want high power, loads of watts, you can't beat a decent transistor PA power amp, like a Crown, QSC or Skytec. Check out some of the vintage TOA PA amps, quite a few have an OPT in them as well as several IP modules.
To get into valve amp if you look on Ebay for OPT's you'll probably find quite a few low power SE OPT's pulled out of radiograms and the like that don't cost much. There are quite a few proven 3-5w SE designs floating about, I'd recommend building something like that as a first amp. Together with a home built active Xover such as the ones on Rod Elliot's site it's possible to build a bi/triamp set up for not much dosh..
Hope that helps, Andy.
To get into valve amp if you look on Ebay for OPT's you'll probably find quite a few low power SE OPT's pulled out of radiograms and the like that don't cost much. There are quite a few proven 3-5w SE designs floating about, I'd recommend building something like that as a first amp. Together with a home built active Xover such as the ones on Rod Elliot's site it's possible to build a bi/triamp set up for not much dosh..
Hope that helps, Andy.
Analogies:
KT150 . . . Transmission for a 1500 Horsepower dragster, it has to work for 6 seconds
KT88 . . . . Transmission for a 500 Horsepower sports car
EL34 . . . . Transmission for a 300 Horsepower family sedan
EL84 . . . . Transmission for a 120 Horsepower gas saver city cruiser
All those tubes, cars, and all those transmissions, work extremely well when used at the limits they were designed for.
The tubes sound great, and the cars get you to where you are going (well, the dragster is lucky to finish the 1/4 mile).
Many amplifiers use the output tubes at 50% to 100% of their maximum power capabilities.
Some guitar amplifiers use the output tubes at 150% of their maximum power capabilities.
You can use the KT88 in a circuit that is designed for an EL84 (with some adjustment of part values;
And Caution: the KT88 filament is 1.6A, the EL84 0.75A, add another 6.3V filament transformer).
You can Not use the EL84 in a circuit that is designed for optimum KT88 performance.
Some amplifiers are designed to work with anything from an EL84 to a KT88 (different sockets).
Plug and Play.
But those amplifiers will not have optimum performance; for most of those tubes, or even for all of those tubes.
The only way to make an audio amplifier with a single EL84 put out 10 Watts is to use the EL84 in switch-mode of a Class D amplifier.
Note: the output powers in Post # 36 is for Push Pull.
Those tubes will not even get 1/2 of that power in single ended (at least not without being at clipping levels).
Have building and listenting!
Do not believe everything you find on the Web; not even all of my posts!
KT150 . . . Transmission for a 1500 Horsepower dragster, it has to work for 6 seconds
KT88 . . . . Transmission for a 500 Horsepower sports car
EL34 . . . . Transmission for a 300 Horsepower family sedan
EL84 . . . . Transmission for a 120 Horsepower gas saver city cruiser
All those tubes, cars, and all those transmissions, work extremely well when used at the limits they were designed for.
The tubes sound great, and the cars get you to where you are going (well, the dragster is lucky to finish the 1/4 mile).
Many amplifiers use the output tubes at 50% to 100% of their maximum power capabilities.
Some guitar amplifiers use the output tubes at 150% of their maximum power capabilities.
You can use the KT88 in a circuit that is designed for an EL84 (with some adjustment of part values;
And Caution: the KT88 filament is 1.6A, the EL84 0.75A, add another 6.3V filament transformer).
You can Not use the EL84 in a circuit that is designed for optimum KT88 performance.
Some amplifiers are designed to work with anything from an EL84 to a KT88 (different sockets).
Plug and Play.
But those amplifiers will not have optimum performance; for most of those tubes, or even for all of those tubes.
The only way to make an audio amplifier with a single EL84 put out 10 Watts is to use the EL84 in switch-mode of a Class D amplifier.
Note: the output powers in Post # 36 is for Push Pull.
Those tubes will not even get 1/2 of that power in single ended (at least not without being at clipping levels).
Have building and listenting!
Do not believe everything you find on the Web; not even all of my posts!
Last edited:
overtheairbroadcast:
"I have built the Simple SE and ran it through Cornwalls[...] [...]I liked it for jazz, pushing the tuner though it, and instrumental music[...] It may not do as well as a PP would for fast and heavier music like full orchestra or hard American rock and roll[...]"
w5jag:
"Push pull amplifiers also have significantly less distortion than single ended amplifiers."
Tubelab_com:
"I had a SPP with EL84's built "by the book" it made about 18 WPC. I liked it for cranking vintage rock as loud as it would go without distorting. I also made a hot-rodded version that got almost 30 WPC. It got louder when I cranked up some 70's and 80's rock, but that seemed to be the only time I used it."
It kind of does, in regards to amplifiers. I started out designing speakers for a 75 watt SS clueless what that meant (bought the unit not because of output wattage, rather the sound specifications) and now heading down the path of building amplification for these high quality, high efficiency speakers.
Thank you for this, sometimes I don't know what I need to know. 😉 Ha. I been reading through it, sometimes his atheistic preaching (to put politely) is at times distracting, so not sure could handle his book, prefer folks to get right to the point, I love efficiency. And I have over 2000, trying to downsize so room for a partner in my life.
Exactly! That is why I have repeated my question multiple times at the seeming cost of getting ignored, has not been back and answered the question. Oh well, I found the answer both searching the internet and searching the forum (thought maybe because seeming to recommend the SE I was not understanding correctly about the PP).
Additionally, I am trying to find at least a mid level amplifier and stick with it (sans iron) so not endlessly doing research and nothing gets built. If it works for dynamic music, strong and clean bass, plus good midrange, das ist alles. This so far seems to be Tubelab's (George's) SPP converted to mono blocks by Skunkie; schematic has not been published though the build series has been done (and she did a fantastic job).
Neat, appreciate sharing. I have realized point to point give an additional cost savings and freedom, plus better quality. The thing now is choosing a design and then finding parts.
"I have built the Simple SE and ran it through Cornwalls[...] [...]I liked it for jazz, pushing the tuner though it, and instrumental music[...] It may not do as well as a PP would for fast and heavier music like full orchestra or hard American rock and roll[...]"
w5jag:
"Push pull amplifiers also have significantly less distortion than single ended amplifiers."
Tubelab_com:
"I had a SPP with EL84's built "by the book" it made about 18 WPC. I liked it for cranking vintage rock as loud as it would go without distorting. I also made a hot-rodded version that got almost 30 WPC. It got louder when I cranked up some 70's and 80's rock, but that seemed to be the only time I used it."
It kind of does, in regards to amplifiers. I started out designing speakers for a 75 watt SS clueless what that meant (bought the unit not because of output wattage, rather the sound specifications) and now heading down the path of building amplification for these high quality, high efficiency speakers.
Thank you for this, sometimes I don't know what I need to know. 😉 Ha. I been reading through it, sometimes his atheistic preaching (to put politely) is at times distracting, so not sure could handle his book, prefer folks to get right to the point, I love efficiency. And I have over 2000, trying to downsize so room for a partner in my life.
Exactly! That is why I have repeated my question multiple times at the seeming cost of getting ignored, has not been back and answered the question. Oh well, I found the answer both searching the internet and searching the forum (thought maybe because seeming to recommend the SE I was not understanding correctly about the PP).
Additionally, I am trying to find at least a mid level amplifier and stick with it (sans iron) so not endlessly doing research and nothing gets built. If it works for dynamic music, strong and clean bass, plus good midrange, das ist alles. This so far seems to be Tubelab's (George's) SPP converted to mono blocks by Skunkie; schematic has not been published though the build series has been done (and she did a fantastic job).
Neat, appreciate sharing. I have realized point to point give an additional cost savings and freedom, plus better quality. The thing now is choosing a design and then finding parts.