Spec, I did only the following modifications:
- Changed the 2 4.7nF for 2 47uF capacitors
- Added a BC337 between the collectors of both VAS transistors
- added a 1k resistor between 1015 collector and BC337 base
- added a 1k pot between 1815 collector and BC337 base
- added a 100uf cap across the BC337 collector and emitter
I believe that is all that is included in the schematic I posted on reply#71, am I mistaken?
Do I need to short the input to measure the current?
I see! So you are talking about this circuit (attached)
Ill make all the changes.
What should be the voltage ratings of the 100uf caps?
I see! So you are talking about this circuit (attached)
Ill make all the changes.
What should be the voltage ratings of the 100uf caps?
I see! So you are talking about this circuit (attached)
Ill make all the changes.
Hey Spec,
I did not have the BC556 on hand, I just ordered some. As soon as they get here Ill make the changes
All that said, I'll repeat my earlier recommendation - you won't find a better book on the subject than Self's.
All that said, I'll repeat my earlier recommendation - you won't find a better book on the subject than Self's.
Bob Cordell's book might be better but they are both excellent.
Hey Mark,
Keep in mind that Im a noobie at all this (electronics).
So the amplifier's resistors type would have no impact on the sound?
I cant talk at all about the impact a very specific part of the design of an amplifier, what I can do is this:
As a musician that has been for 20 years listening to a very specific recording, one can get extremely familiar with the particulars of how it sounds and be able to perceive very small nuances. How scientifically small? I dont know. It was initially a song that I really liked nowadays I use it just to test speakers and amps. But I sometimes can hear the difference from the same model of amp/speaker if they are in the same room and position.
Look, most engineers would laugh (as they have done to me) at you if you say that if you wanted to buy a guitar amp, and had all the money in the world, a tube one would be brought home.
They know it has more THD than solid state but the sound at the end is what matters. I get that it must be frustrating to listen to the enormous amount of bullshit that surrounds this subject but is the example you gave on the link measurable? Correct me if Im wrong but if you wanted to see if a pot at the beginning of the chain affected the frequency response wouldnt that be easy to measure?
The resistor types can have some effect, but usually only very little and the loudspeaker will have a much larger effect as it's resistance is made of copper. So at the very high end (not this circuit) things like self heating of some resistors (e.g. the gain setting ones) can have a little effect and cause distortion. Another possible effect could be noise from some resistors that seen an sizable DC bias. However a good circuit often avoids this problem by not having a DC bias at noise critical resistors. Without a bias the noise of a carbon resistor is not higher than an expensive metal foil resistor. So there is quite some audio-foolery going on.
Similar with capacitors - usually no need to absolutely have PP caps in an audio circuit. The cheaper polyster caps add some small phase shift - but this is more like equivalent to having the speaker moved a fraction of a millimeter. It a common misunderstanding to think that dielectric absorption would cause distortion - it's a linear effect and only gives a minor effect on phase and amplitude, usually no harmonics.
It may be a little overreacting, but if one sees specs for PP caps in an amplifier, expect over-specified parts.
As a musician that has been for 20 years listening to a very specific recording, one can get extremely familiar with the particulars of how it sounds and be able to perceive very small nuances. How scientifically small? I dont know. It was initially a song that I really liked nowadays I use it just to test speakers and amps. But I sometimes can hear the difference from the same model of amp/speaker if they are in the same room and position.
Look, most engineers would laugh (as they have done to me) at you if you say that if you wanted to buy a guitar amp, and had all the money in the world, a tube one would be brought home.
They know it has more THD than solid state but the sound at the end is what matters. I get that it must be frustrating to listen to the enormous amount of bullshit that surrounds this subject but is the example you gave on the link measurable? Correct me if Im wrong but if you wanted to see if a pot at the beginning of the chain affected the frequency response wouldn't that be easy to measure?
The day I told him that most good guitar amps take tubes, he FLIPPED and had a crazy argument with me... I still remembers his face when I said That, the whole.family was there and silence was all one could hear.
But for you to have a laugh... after years playing tube amps, having intense pain from carrying that huge thing around and spending way more than reasonable, the last 5 years or so of my career was playing a small solid state. It is literally called Jazz Amp. A single 12' speaker with a kickass sound that was carried back and forth on the subway. Nowadays it is a major decoration piece in my living room.
The day I told him that most good guitar amps take tubes, he FLIPPED and had a crazy argument with me... I still remembers his face when I said That, the whole.family was there and silence was all one could hear.maybe he had no problem with tube or solid state. his issue i guess that you play guitarBut for you to have a laugh... after years playing tube amps, having intense pain from carrying that huge thing around and spending way more than reasonable, the last 5 years or so of my career was playing a small solid state. It is literally called Jazz Amp. A single 12' speaker with a kickass sound that was carried back and forth on the subway. Nowadays it is a major decoration piece in my living room.so have you give a thought what you have gained throughout all those years? other than temporal joyness. your ex-g's dad gave his life to give peace to the community... cheers.
Sigh.
Why does nearly every thread involving audio turn in to an argument about audiophoolery?
Who are the right and wrong engineers to ask? Just because the person you asked about something, violently disagreed with you, it doesn't mean their view is invalid. The advantages of forums such as this, over asking a friend, relative colleague etc. is, one can ask a lot of engineers and gather a consensus on a matter, not just take one person's word for it. Also remember this is a technical discussion and no one should feel offended, if they're contradicted.
There's a lot of the usual nonsense here about using passives and capacitors to avoid noise and distortion and speaker cables. There's nothing special about polypropylene, over polyester capacitors. I bet no one will be able to tell the difference, if subject to a blind test. Metal film resistors are less noisy, than carbon film, but it's wrong to say the latter shall be used everywhere in the audio amplifier, where there are plenty of parts of the circuit where it won't make any difference, i.e. the resistors used to bias the zeners diodes. It's amusing when a circuit mandates high end capacitors and metal film resistors, then uses carbon potentiometers, especially with a DC bias. In this case, the circuit has non-polarised capacitor, (220µF) carrying an AC signal, with no DC bias, which will distort the signal more than any polyester capacitor. Polarised capacitors act as poor diodes, (the electrolytic capacitor is derived from the electrolytic rectifier) and need a DC bias to avoid rectifying, thus distorting the signal. As far as resistors are concerned: I'd be more concerned about the type of resistor used for the 0R22 on the output stage, which could cause problems with oscillation if it's very inductive i,.e. wire wound, on a ferrous former.
It is simply untrue that amplifiers can't be measured and characterised. This is a common audiophool myth. In reality, everything which can be heard and more, can be accurately measured and characterised. Measuring equipment is well over an order of magnitude better than the human ear at picking up distortion. The problem is it's important to measure the right thing and plenty of the traditional tests used to characterise amplifiers don't. For example, pure sinewaves, which in no way resemble music or speech, are often used to obtain THD figures. The video linked to by Mark Hennessy demonstrates this perfectly and is well worth watching.
As far as the thermionic vs solid state is debate is concerned. It's true that both amplifier topologies have different characteristics, yet paradoxically can be made to sound exactly the same: please read on, I'm not trolling, its true! It's possible to make a thermionic and a solid state amplifier with imperceptible amounts of distortion, when played below the clipping threshold, at which point they'll both be audibly transparent i.e. sound the same. The difference is a thermionic amplifier will have a nicer sounding distortion, than a solid state model, when over-driven and this effect is often desirable in a guitar amplifier, where the distortion is part of the sound and hi-fidelity is not a requirement.
Over 40 years ago a double blind test was done on three amplifier designs: one thermionic and two solid state, with golden eared audiophiles and they couldn't tell the difference. Of course both of the amplifiers were designed for minimal distortion and weren't driven into clipping, but the test was for hi-fi, not a guitar amplifier.
[url]http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1978/Valves%20versus%20Transistors%20DCD.pdf[/url]
As far as hi-fi is concerned, it's fairly easy to make an amplifier an imperceptible level of distortion. In reality speakers and room acoustics are the dominant factor, not the amplifier. It's possible that a high end hi-fi system will sound the same as a TV, if they're both connected to the same speakers and played at a low enough level to avoid clipping.
This goes back to the requirements of the original poster. Is this amplifier going to be used for hi-fi, where the distortion should be minimal or a guitar, where a certain type of distortion is required? With the appropriate modifications, there's no reason why this circuit can't give a reasonable faithful reproduction of the source, but if you want a guitar amplifier, with nice distortion, then look elsewhere.
The engineer´s point was clear, he thought that tubes in a amp made no sense. Even after I told him that the distortion they add is why they are still used. I dont know if he view was invalid or not. I simply stated a fact: if guitar players like some distortion in their sound, they will most likely look for an amp with tubes if they can afford it. The forum is a great place to learn! No wonder I cant keep myself from reading the posts!
I have nothing but gratitude for you guys!
If the whole point of using a tube amp is so you can have the characteristic sound of their distortion, how can you say that it is possible to make a solid state sound just like a tube amp?
They are made with low wattage on purpose so they will start to distort even at moderate volume. What we are looking for is exactly that light distortion it adds to the sound. If you say your solid state amp sounds just like a tube amp except when distortion starts to happen, isnt that the same as saying that your car does exact the same thing as an airplane except flying?
The engineer´s point was clear, he thought that tubes in a amp made no sense. Even after I told him that the distortion they add is why they are still used. I dont know if he view was invalid or not. I simply stated a fact: if guitar players like some distortion in their sound, they will most likely look for an amp with tubes if they can afford it. The forum is a great place to learn! No wonder I cant keep myself from reading the posts!
I have nothing but gratitude for you guys!
If the whole point of using a tube amp is so you can have the characteristic sound of their distortion, how can you say that it is possible to make a solid state sound just like a tube amp?
They are made with low wattage on purpose so they will start to distort even at moderate volume. What we are looking for is exactly that light distortion it adds to the sound. If you say your solid state amp sounds just like a tube amp except when distortion starts to happen, isnt that the same as saying that your car does exact the same thing as an airplane except flying?Yes, I do understand that the whole point of a tube amplifier is the distortion. Perhaps the person who you spoke to doesn't get this or believes the extra cost doesn't justifies it. In any case he's entitled to his point of view.
To answer your question. You're talking about a guitar amplifier, which will be driven into distortion, where as the paper I linked to is about hi-fi, which has totally different requirements to a guitar amplifier. A high amplifier should never be driven into distortion. The results of the experiment are that for hi-fi, both solid state and thermionic amplifiers give equally good sound quality, so there's no point in selecting one over the other, based on how they sound. The solid state designs are just cheaper and more reliable but people may like the way thermionic tubes look and the idea of having something old. For a guitar amplifier, a tube amp is a totally different beast to a solid state amp and there are good reasons to choose it, for the way it sounds.
The budget got thinner and tube amps were no longer an option, by buying the solid state I had to make a compromise. It does not have the sound I want but it saves me from ending up in the hospital after a small tour.
The budget got thinner and tube amps were no longer an option, by buying the solid state I had to make a compromise. It does not have the sound I want but it saves me from ending up in the hospital after a small tour.so i guess you dont need this thread. your heavily distorted amp originally should give you the better (or whitier) sound you required, no? i agree with earlier commenter that good engineer should listen to their clients. so maybe another thread on how to purposely introduce distortion out of solid state to get tube's quality sound?