Not necessarily. Its just that you, and many other people, have never heard a SS system that rivals or surpasses tubes. We had a visitor here recently who could hardly believe there wasn't one tube in the system. He has good ears and is a smart and pretty talented designer, but he just never experienced what he described in this case as, "...finding out what is attainable."
When did the value of the feedback resistor go from 10kΩ to 12kΩ?
So you had no schematic, no specifications, and no design experience? Consider I am also mentally challenged.
Oh? We don't need an OPT? How then does the sound signal get fed into the drivers? Puzzling then why it and a feedback loop are then shown on the schematic.
Either we need the OPT specification (or please help me select a Sowter transformer: https://www.sowter.co.uk/acatalog/E_A_Sowter_Ltd_PUSH_PULL_OUTPUT_14-p1.html) or the updated schematic so I can finish soldering.
To be clear, if I mean an integrated, I will say so. In this case, I am meaning monoblocks not driven by a pre amplifier, instead connect to the input (ex. a phonograph amplifier or receiver).
I forget which tube it is, so much gain they were using it without pre amplifiers, maybe the KT66. This is why I asked a long while back about this, never did get an answer (seems my question was not clear). And as said many times before, not everything read here is fact, like those folks happy with PP without feedback loops.
Would this be just the value of R7 or all the resisters sans R16?
I don't see how the attached is after the calculator, since discusses theory only, getting us no closer to determining the value of R16.
Thank you. 🙂
This is on op amplifiers, not PP amplifiers, so how does it apply?
I am confused. I am saying tubes usually lack dampening, not SS (which can get into the thousands, ex. 4000DPF).
To achieve a SS that has texture and a little warmth (we are not talking a sound that is destroying the sound) costs far in excess of affordable, then it does not really exist, not obtainable except the wealthy.
For me, paying north of four figures for one hifi component is not good stewardship or a simple life, however, this is individual, clearly folks do as there is a market. Even paying $50 for long underwear that last six months to a year is something I am not willing to do, the fabric costs less and can sew my own (and adjust the design so doesn't wear out so quickly).
Of course could be misunderstanding and this SS is four figures or better, less.
Oh and to be clear, I have a SS that does surpass tubes, by a lot, however, I bought it used. Trouble is it is 75 watts, enough to make your eardrums bleed. It blew me away and changed my mind about SS.
Thank you @huggygood ! 🙂
Is this it? https://www.hificollective.co.uk/catalog/TX-OP-200-1-IE-PP-F.html
Is this it? https://www.hificollective.co.uk/catalog/TX-OP-200-1-IE-PP-F.html
On the contrary, the value of R16 depends on various factors. One of them is stability of the feedback loop, which can be tricky with transformers and capacitor-coupled tube stages. Low frequency and or high frequency instability are the first concern. If you don't like control theory, there is an historically earlier and perhaps more intuitive way: Bode plots. This will also lead to an understanding of frequency poles and zeros.
https://lpsa.swarthmore.edu/Bode/Bode.html
https://en.wikipedia.org/wiki/Bode_plot
People often find it easier to start understanding feedback in the context of opamps. Operational Amplifiers were originally invented for analog computing and related types of applications. Their circuit function is primarily defined by the components around them, including negative, and sometimes positive, feedback.
One the basic ideas of what feedback does, how it works, how it can turn an amplifier into an oscillator, etc., then that basic understanding can be applied to tubes as well.
Thank you for the links, it is appreciated. 😀
I don't remember seeing control theory, though feeling really icky last couple days, especially today. So I can't say I like it or not. I think if had to describe it, would say my preference be for application rather than theory. I am a tactile learner, a little bit of written, and forget verbal (university classes were lots of fun...).
Seems I have yet again misunderstood. I thought if the OPT became a known entity, we no longer had to be concerned about R16, is this not true?
Ah! Okay, now I am tracking. Well, I honestly lost motivation when the OPT became a known value. However, if R16 is still an issue, will have to delve into what resistance counts (didn't get an answer to this question, certainly don't expect it).
I think I am understanding. At least enough to know oscillation is undesirable and detrimental.
"...if the OPT became a known entity, we no longer had to be concerned about R16..."
No. The OPT is in the FB loop. R16 connects to the transformer output is why. R16 also has a capacitor in parallel with it. Together they form an important time constant of the system. If you change one then you may have to change the other. As I am trying to explain, things are not so simple such that one component has one effect in a circuit. Its not like that, but it takes some time and some study to start to understand.
Don't know how far you got in math, how much you remember, how good you were at it, etc. Whatever it is that describes you present comfort level helps to get some sense of how to present sometimes complex ideas to you. The more we can identify a strong starting point, the faster we can make useful progress in answering your questions, and or maybe make some progress in getting you to ask closer to the right questions for whatever it is you really want to know.
No. The OPT is in the FB loop. R16 connects to the transformer output is why. R16 also has a capacitor in parallel with it. Together they form an important time constant of the system. If you change one then you may have to change the other. As I am trying to explain, things are not so simple such that one component has one effect in a circuit. Its not like that, but it takes some time and some study to start to understand.
Don't know how far you got in math, how much you remember, how good you were at it, etc. Whatever it is that describes you present comfort level helps to get some sense of how to present sometimes complex ideas to you. The more we can identify a strong starting point, the faster we can make useful progress in answering your questions, and or maybe make some progress in getting you to ask closer to the right questions for whatever it is you really want to know.
Sorry I am not clear. Maybe try this:
OPT unknown => R16 value becomes unknown => feedback amount becomes unknown => amplifier becomes unbuildable
OPT known => R16 relationship restored => feedback loop returns to as designed => no oscillations => amplifier becomes buildable
Are these two understandings correct?
Maybe got missed earlier, this is the transformer specified in the PDF @huggygood provided: https://www.hificollective.co.uk/catalog/TX-OP-200-1-IE-PP-F.html.
I got all the way through pre calculus. Calculus was taught by a Iranian who tried to get help with English from the class (Farsi sounds interesting) and the weekly homework packet was literally a half inch thick; more than half the class dropped out by the second week. Add to it I was failing to see the application. As we have seen, I apparently don't remember algebra well, probably could refresh myself if needed.
Last time I used mathematics was structures classes in about eight years ago and have forgotten how to do the structural calculations. Now just use an online calculator to get an approximation. Yep, being lazy.
Oh and I did okay in mechanical physics, though was tough passing electromagnetism physics, again, hard seeing the application to architecture.
By the way, my IQ is only 113.
This is a very misleading statement that requires additional context to quantify, but is usually only the case when the feedback has been implemented poorly.
Just realized the resister values are missing, can anyone provide R1 (150kΩ?), R2 (390Ω?), R4, and R8, please?
If you have an old Windows (XP, 7 32bit) PC, then I recommend Glassware Audios tube amp design apps and also check out his kits.
As a tube beginner I found Tube Cad and SE Amp Cad very informative as you can play about with the component value and tube types and view the results.
https://glass-ware.stores.yahoo.net/
https://glass-ware.stores.yahoo.net/adsoffromgla.html
https://glass-ware.stores.yahoo.net/tubjourcomso.html
As a tube beginner I found Tube Cad and SE Amp Cad very informative as you can play about with the component value and tube types and view the results.
https://glass-ware.stores.yahoo.net/
https://glass-ware.stores.yahoo.net/adsoffromgla.html
https://glass-ware.stores.yahoo.net/tubjourcomso.html
This statement is not correct. You build the amp with the OPTs you have on hand and optimise the value by listening. In many cases people prefer the sound with different amounts of feedback, depending on what they listen to, how they listen and the design of the amplifier. The reason why you are struggling to get a definitive reply from anyone for this question is that the answer is 'it depends'.
Best to pick something straightforward and get on with it.
Another option: Look out for an old tube reel-to-reel tape recorder or console stereo and harvest the transformers, tubes and hardware, Build just the amp point to point if that is your preferred option. For next to no outlay you get to build something useful, and get comfortable with the fundamentals. Depending on your location you might even find a benefactor close by who would donate a candidate. If you were in Sweden I would have an old Tandberg 74 you could look at (ECL86 SE).
There are lots of different levels of competency in this hobby, and we all just want to help you get started with a concrete build of your own.
Regarding transformers, here are some equivalent circuit models of transformers:
As can be seen, they contain several resistors, capacitors, and inductors. Those things necessarily affect frequency response and phase response of a signal passing through a transformer.
If you read about Bode Plots, you will find that there are a number of frequency poles and zeros associated with a transformer. Thus when a transformer is inside a feedback loop, the loop has to be frequency compensated considering the particular transformer design in order for the loop to stable and not oscillate.
Also as I said before, changing R16 would have various effects. The effect we may want to consider first is the effect on loop stability if we don't want to risk making an oscillator. Then we can consider the other things that change when we change a feedback loop.
As can be seen, they contain several resistors, capacitors, and inductors. Those things necessarily affect frequency response and phase response of a signal passing through a transformer.
If you read about Bode Plots, you will find that there are a number of frequency poles and zeros associated with a transformer. Thus when a transformer is inside a feedback loop, the loop has to be frequency compensated considering the particular transformer design in order for the loop to stable and not oscillate.
Also as I said before, changing R16 would have various effects. The effect we may want to consider first is the effect on loop stability if we don't want to risk making an oscillator. Then we can consider the other things that change when we change a feedback loop.
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There is giving the starving man the fish or the fishing rod. Then there is giving the starving man that Japanese fish that has to be prepared just right or it poisons you. Give the guy a break!
He asked, "what is a frequency pole?" He also complained that other people wouldn't answer his questions. He wants to know what happens if R16 is changed. He is inquisitive, and sometimes asks questions that don't have simple answers. If he wants baby food answers he can ask for that. If he wants to chew on a steak instead that's his choice too.
Adriel, could I recommend a book or two to that might help you? Merlin Blencowe's books have been mentioned already, but to be specific I think the one below could be a good introduction to some of the key concepts and personally I find Merlin's explanations to be clear and easy to follow. This is a preamp book, but many of the fundamental principles are relevant to you.
Designing High-Fidelity Valve Preamps, Merlin Blencowe, ISBN: 0956154530
The following is also very good, and covers power amps, but it has a lot of detail on a lot of areas and so could be overwhelming if you're just starting out.
Valve Amplifiers, Morgan Jones, ISBN: 0080966403
Designing High-Fidelity Valve Preamps, Merlin Blencowe, ISBN: 0956154530
The following is also very good, and covers power amps, but it has a lot of detail on a lot of areas and so could be overwhelming if you're just starting out.
Valve Amplifiers, Morgan Jones, ISBN: 0080966403