Correcting misinformation
Sy, I am sorry for going overboard. This is my last post concerning this subject.
You: "You state DHT's cannot sound good (compared to even a basic KT88 Amp) and the only good sounding speakers are low efficiency Cone/Dome Speakers and Ribbons? And the best amplifiers in the world are made by you?"
Me now: I never said a DHT amp couldn't be as good or better than a "basic KT88 amp". An outright distortion of my position.
Where did I say the best amps in the world are made by me? Again an outright distortion.
I stated at the CES and The Show that the 300b amps were trounced.
I did not say ONLY LOW efficiency cone/dome speakers and ribbons are the best? Again total distortion.
By the way, I have also heard electrostats, which are low efficiency speakers, with amps that sounded great.
I mentioned I heard some Ribbons and air motion transformers that solidly beat the horns I heard at the CES show. You agreed with your post even mentioning speaker types?
You page 4: " And we both know that you do not get 15 - 20V RMS from a 6922."
Me: I can get 20vrms from a 6922 tube, and with room to spare.
So I am a liar again?
You: "I merely state that the common 6922 tends to have fairly high distortion and comparably (compared to other triodes) higher levels of upper harmonics.
If you have 6922's that do not behave like most 6922 Valves then I would argue they should not be called 6922 (as they would have different anode curves) and secondly I would like to see an explicit statement of the Valve Type, Conditions and Results that can be verified independently."
Really. Here is your own statement of record. "Yet you Driver valves that actually are quite non-linear and have quite high levels of upper harmonics."
Me now: So you made that comment up out of the air without proper testing. Now you say the number should be different?
Well, 300bs, 6550/HT88, or EL34 shouldn't be called that because of different distortion characteristics?
Well, telefunken's 12ax7s also have different distortion characteristics over the years, seemingly each year produced, and Sovtek, EI etc all have different distortion characteristics. Should we change their numbers?
You: "Okay, one last time, did you, in the context of discussing Single Ended Amplifier circuits state that you are:
"getting 0.05% total distortion from All the previous stages (no cancelling distortion stages allowed) at max drive for full output of a 300b amp? (I include my preamp and non output stages of my amps.)"
Me: I apologized, and you copied my apology that I should have mentioned it was in PP circuit a page or two ago. Interesting you keep bringing it up.
Me: Yes, but you also used a transformer didn't you. Two stages I see.
You: Hmmm. A transformer is a "stage"? Then so is a coupling capacitor. And a resistor."
A tranny is much different than a cap or resistor. A transformer can also have gain of its own while a cap and resistor doesn't. A tranny has frequency response problems and the best caps and resistors can go to very very high ground and low too for that matter, much lower than a transformer unless you wish to compromise high frequency response.
So maybe we can used several trannies, or one high gain tranny, and not typical gain stages, of course an output stage, and call it a one stage amp? Let's stick with traditional concepts.
"Me: Try Audia. I think the one I heard went to 600hz.
You: "There does not seem to be a company called "Audia", at least I cannot find them. Maybe you are talking about Radia Linesource drivers? They are not ribbons." So you haven't heard of them. Who cares.
"But even with 500Hz admitted as possible, we are sill 2 Octaves plus from your 100Hz figures and barely 1 Octave from my 1KHz and then practical conerns actually tend to illustrate my 1KHz figure as ROUGH GUIDE to the lowest point."
You are the one who wanted the information and I provided it. Big deal.
Compensation is getting something of value, in this case getting something and not having to pay for it like the rest of us do, or even reduced prices.
Manufacturers like me have to let others know we are manufacturers. Don't you think all reviewers also owe us by letting us know if one is receiving things for free/cheaper prices without being asked?
Hopefully I have corrected your unfair and insulting comments.
Sy, I am sorry for going overboard. This is my last post concerning this subject.
You: "You state DHT's cannot sound good (compared to even a basic KT88 Amp) and the only good sounding speakers are low efficiency Cone/Dome Speakers and Ribbons? And the best amplifiers in the world are made by you?"
Me now: I never said a DHT amp couldn't be as good or better than a "basic KT88 amp". An outright distortion of my position.
Where did I say the best amps in the world are made by me? Again an outright distortion.
I stated at the CES and The Show that the 300b amps were trounced.
I did not say ONLY LOW efficiency cone/dome speakers and ribbons are the best? Again total distortion.
By the way, I have also heard electrostats, which are low efficiency speakers, with amps that sounded great.
I mentioned I heard some Ribbons and air motion transformers that solidly beat the horns I heard at the CES show. You agreed with your post even mentioning speaker types?
You page 4: " And we both know that you do not get 15 - 20V RMS from a 6922."
Me: I can get 20vrms from a 6922 tube, and with room to spare.
So I am a liar again?
You: "I merely state that the common 6922 tends to have fairly high distortion and comparably (compared to other triodes) higher levels of upper harmonics.
If you have 6922's that do not behave like most 6922 Valves then I would argue they should not be called 6922 (as they would have different anode curves) and secondly I would like to see an explicit statement of the Valve Type, Conditions and Results that can be verified independently."
Really. Here is your own statement of record. "Yet you Driver valves that actually are quite non-linear and have quite high levels of upper harmonics."
Me now: So you made that comment up out of the air without proper testing. Now you say the number should be different?
Well, 300bs, 6550/HT88, or EL34 shouldn't be called that because of different distortion characteristics?
Well, telefunken's 12ax7s also have different distortion characteristics over the years, seemingly each year produced, and Sovtek, EI etc all have different distortion characteristics. Should we change their numbers?
You: "Okay, one last time, did you, in the context of discussing Single Ended Amplifier circuits state that you are:
"getting 0.05% total distortion from All the previous stages (no cancelling distortion stages allowed) at max drive for full output of a 300b amp? (I include my preamp and non output stages of my amps.)"
Me: I apologized, and you copied my apology that I should have mentioned it was in PP circuit a page or two ago. Interesting you keep bringing it up.
Me: Yes, but you also used a transformer didn't you. Two stages I see.
You: Hmmm. A transformer is a "stage"? Then so is a coupling capacitor. And a resistor."
A tranny is much different than a cap or resistor. A transformer can also have gain of its own while a cap and resistor doesn't. A tranny has frequency response problems and the best caps and resistors can go to very very high ground and low too for that matter, much lower than a transformer unless you wish to compromise high frequency response.
So maybe we can used several trannies, or one high gain tranny, and not typical gain stages, of course an output stage, and call it a one stage amp? Let's stick with traditional concepts.
"Me: Try Audia. I think the one I heard went to 600hz.
You: "There does not seem to be a company called "Audia", at least I cannot find them. Maybe you are talking about Radia Linesource drivers? They are not ribbons." So you haven't heard of them. Who cares.
"But even with 500Hz admitted as possible, we are sill 2 Octaves plus from your 100Hz figures and barely 1 Octave from my 1KHz and then practical conerns actually tend to illustrate my 1KHz figure as ROUGH GUIDE to the lowest point."
You are the one who wanted the information and I provided it. Big deal.
Compensation is getting something of value, in this case getting something and not having to pay for it like the rest of us do, or even reduced prices.
Manufacturers like me have to let others know we are manufacturers. Don't you think all reviewers also owe us by letting us know if one is receiving things for free/cheaper prices without being asked?
Hopefully I have corrected your unfair and insulting comments.
Before getting on with my reply, I would like to reiterate what SY said. Stop arguing about the merits and flaws of horns vs dynamic speakers, please. That's not what Ralf was wondering about, and we should take that debate elsewhere.
Originally posted by SY
I don't have the patience for the book-length call-and-response, so if you'll forgive me, I'll just hit the two highlights.
OK. I'm sorry if my posts are too long. Just thought to be a bit verbose, since he was asking about information.
I use the two in conjunction. I've become convinced that the virtues of galvanic isolation outweigh the disadvantages of running the signal through an additional magnetic circuit. I'm less convinced that voltage step up with the transformer is as easy of a call.
Voltage step-up or step-down is just another tool in the box. For a high-capacitance valve, such as the 6C45P or 6N30P, you may want to step it down to improve frequency response. For spud amps, you may want to step it up. But, yes, galvanic isolation is the main advantage I'm looking for with transformers, too. Balancing is just a side benefit. But getting both at once is prefferable to a phase splitter, IMHO.
Ralf: You seem to have some consensus that an input transformer would be good for you. 😉
What happens for any particular speaker in the bass as you put a series resistor of 8 ohms or so in series with it is something easy to accurately simulate.
I was not talking about 8 ohms. As I pointed out, I'm not even getting into a debate on outrageous impedances, and 8 ohms certainly figures as such.
The amount of series resistance that is acceptable depends entirely on the loudspeaker. For example, if the crossover already has a significent DC resistance in series with a driver, the effect of output impedance on that driver will be swamped. If the driver Qms >> Qes, you need a low impedance to control it.
More precisely, as we all know, the total Q of the driver is the Qms in parallell with the Qes. The Qms does not change at all, as long as you do not change the mass loading of the driver. The Qes changes with whatever you put in series with the driver. When you know the output impedance, the impedance of the crossover, and the Qes of the driver itself, you can find the resulting Qes, and recalculate the Qts based on that. In some cases, you will find that the difference is very limited. Smaller drivers usually have lower Qms values, so midrange and tweeter response is not affected that much.
Yes, series resistance can affect the crossover points, and hence frequency response of the system, but only to a limited extent. At about 1 ohm Zout, the impact of Zout is smaller than the component tolerances of many speakers. The real relevance of (non-monstrous) output impedance, is in damping the driver resonances. And you quite simply cannot make a blanket statement about that; it depends on the Qms to Qes ratio.
Ralf: If you go for something with a low damping factor, be sure to look for speakers whose drivers (especially the woofers) have low Qms values, that is, that are mass controlled. Higher damping factor does make the choice of speaker less critical, though. At a very reasonable price, and excellent value for money, the Usher M-700 (4 ohm) uses mass controlled drivers. About USD 1K per pair, and they easily perform to about 3 times that.
One may like this effect in the bass or the midrange, and I won't argue the merits of my design goals versus someone else's, but it's clearly an effect, it's not accuracy.
I prefer a sensible damping factor, of course. I was just pointing out that it's not black/white.
Originally posted by DVDHack
Guys, this thread is about helping me and others in deciding which is the better set of tubes to build an amplifier with not about one upmanship of your respective skilss, knowledge and opinion.
Is this in reference to the horns/dynamic debate, or to the debates about valves and topologies? If the latter, I apologize. Just trying to shed light on many sides of the issue.
Originally posted by SY
I don't have the patience for the book-length call-and-response, so if you'll forgive me, I'll just hit the two highlights.
OK. I'm sorry if my posts are too long. Just thought to be a bit verbose, since he was asking about information.
I use the two in conjunction. I've become convinced that the virtues of galvanic isolation outweigh the disadvantages of running the signal through an additional magnetic circuit. I'm less convinced that voltage step up with the transformer is as easy of a call.
Voltage step-up or step-down is just another tool in the box. For a high-capacitance valve, such as the 6C45P or 6N30P, you may want to step it down to improve frequency response. For spud amps, you may want to step it up. But, yes, galvanic isolation is the main advantage I'm looking for with transformers, too. Balancing is just a side benefit. But getting both at once is prefferable to a phase splitter, IMHO.
Ralf: You seem to have some consensus that an input transformer would be good for you. 😉
What happens for any particular speaker in the bass as you put a series resistor of 8 ohms or so in series with it is something easy to accurately simulate.
I was not talking about 8 ohms. As I pointed out, I'm not even getting into a debate on outrageous impedances, and 8 ohms certainly figures as such.The amount of series resistance that is acceptable depends entirely on the loudspeaker. For example, if the crossover already has a significent DC resistance in series with a driver, the effect of output impedance on that driver will be swamped. If the driver Qms >> Qes, you need a low impedance to control it.
More precisely, as we all know, the total Q of the driver is the Qms in parallell with the Qes. The Qms does not change at all, as long as you do not change the mass loading of the driver. The Qes changes with whatever you put in series with the driver. When you know the output impedance, the impedance of the crossover, and the Qes of the driver itself, you can find the resulting Qes, and recalculate the Qts based on that. In some cases, you will find that the difference is very limited. Smaller drivers usually have lower Qms values, so midrange and tweeter response is not affected that much.
Yes, series resistance can affect the crossover points, and hence frequency response of the system, but only to a limited extent. At about 1 ohm Zout, the impact of Zout is smaller than the component tolerances of many speakers. The real relevance of (non-monstrous) output impedance, is in damping the driver resonances. And you quite simply cannot make a blanket statement about that; it depends on the Qms to Qes ratio.
Ralf: If you go for something with a low damping factor, be sure to look for speakers whose drivers (especially the woofers) have low Qms values, that is, that are mass controlled. Higher damping factor does make the choice of speaker less critical, though. At a very reasonable price, and excellent value for money, the Usher M-700 (4 ohm) uses mass controlled drivers. About USD 1K per pair, and they easily perform to about 3 times that.
One may like this effect in the bass or the midrange, and I won't argue the merits of my design goals versus someone else's, but it's clearly an effect, it's not accuracy.
I prefer a sensible damping factor, of course. I was just pointing out that it's not black/white.
Originally posted by DVDHack
Guys, this thread is about helping me and others in deciding which is the better set of tubes to build an amplifier with not about one upmanship of your respective skilss, knowledge and opinion.
Is this in reference to the horns/dynamic debate, or to the debates about valves and topologies? If the latter, I apologize. Just trying to shed light on many sides of the issue.
As far as input transformers go, is a passive preamp utilising a transformer adequate in its place. I was considering a passive volume using a ladder resistor network and switch.
Konnichiwa,
I have previously done extensive comparisons. The result is that I have been using a transformer based (S&B TX-102) passive linestage ever since, after comparing a 10K discrete true ladder attenuator with holco resistors in critical positions to Sowter and S&B Transformers. Nor am I alone in this view, but detractors exist.
Sayonara
DVDHack said:
I have previously done extensive comparisons. The result is that I have been using a transformer based (S&B TX-102) passive linestage ever since, after comparing a 10K discrete true ladder attenuator with holco resistors in critical positions to Sowter and S&B Transformers. Nor am I alone in this view, but detractors exist.
Sayonara
Please don't misunderstand; everyone has different preferences and styles. It's purely my own inability to type and lack of attention span in play, not a general comment that your posts are "too long." Lots of other people (KYW and Steve Eddy, for example) revel in the long, long call-and-response.
I have two small problems here; first, even one ohm can cause a significant modification in frequency response in many (most) common speakers. I ran a quick calculation on the impedance curves of a Snell speaker that I measured a few weeks ago, and putting an ohm in series with the resistance of my cables caused a midrange variation of a dB. Earthshaking change, no. Audible, yes. Using the low feedback P-P amp I have here, the variation drops to something less than half a dB (still more than I'd like, to be honest, but I don't have superconducting cables, either).
Second small problem: for SE amps, 8 ohm source Z is not exactly outrageous. In fact, I think it's the norm for SE. The only way I see to get it significantly lower is to use a tube with a really low Rp, normally a BIG power triode, then throw away even more efficiency by using a higher-than-optimum (from a power-transfer critereon) plate load. I can make a 300B SE amp with a watt max power give me a low source Z, but that's kind of ridiculous.
Now, I cheerfully admit that my experience with SE is undoubtedly much less than yours, so if you've got some examples of lowish source Z SE amps and how it's done, I'd really like to know about it.
EDIT: I looked up the source Z of a few commercial SET amps. A couple of them DID have source Zs of 1-1.5 ohms at midband; they all used feedback, and had source Zs rising to much higher levels at the top two octaves. So, it can be done. Most seemed to be in the 2-8 ohm range, and all of the zero-feedback ones were at the high end of this.
Konnichiwa,
Hmmm. I did look at that (and tested it). The variation from the Source Impedance of a NORMAL SET Amp will bu around a decade than that from your room, lest you listen in an anechonic chamber, using "normal" speakers.
It actually IS aoutrageous. If you get 8 Ohm output impedance you are using the 32 Ohm tap (not that there is usally). Simple math for maximum power delivery vs. distortion will show you an optimum at a load Z that is between 2 - 4 Times the valves anode impedance, usually a factor of 3 is common. So a Valve like the 300B with 700 Ohm Anode impedance is loaded with 2k3 (this is classic WE) or more load impedance.
Translated to a nominal 8 ohm Tap this is 8/3=2.7 Ohm plus around 0.1R secondary winding resistance and 50R transformed down primary DCR, adding around 0.3 Ohm for a usual 3 Ohm Output Impedance. Often modern 300B Amp's actually trade a little power for lower distortion using 3 - 5K Output Transformers, further reducing the Output Impedance compared to an 8 ohm load, with the 5K Transformers often seen in Japan and favoured by me you get around 1.3 Ohm Output impedance.
See above. The NORM for SE Amp's bred for max power tends to be 3 ohm Output Impedance, those targeted at low distortion at around 20% lower power will be between 1 to 1.5 Ohm. mIf you see much higher output impedances you see signs of either ****-poor output transformers or bad (read high distortion) design.
Sayonara
SY said:
Hmmm. I did look at that (and tested it). The variation from the Source Impedance of a NORMAL SET Amp will bu around a decade than that from your room, lest you listen in an anechonic chamber, using "normal" speakers.
SY said:
It actually IS aoutrageous. If you get 8 Ohm output impedance you are using the 32 Ohm tap (not that there is usally). Simple math for maximum power delivery vs. distortion will show you an optimum at a load Z that is between 2 - 4 Times the valves anode impedance, usually a factor of 3 is common. So a Valve like the 300B with 700 Ohm Anode impedance is loaded with 2k3 (this is classic WE) or more load impedance.
Translated to a nominal 8 ohm Tap this is 8/3=2.7 Ohm plus around 0.1R secondary winding resistance and 50R transformed down primary DCR, adding around 0.3 Ohm for a usual 3 Ohm Output Impedance. Often modern 300B Amp's actually trade a little power for lower distortion using 3 - 5K Output Transformers, further reducing the Output Impedance compared to an 8 ohm load, with the 5K Transformers often seen in Japan and favoured by me you get around 1.3 Ohm Output impedance.
SY said:
See above. The NORM for SE Amp's bred for max power tends to be 3 ohm Output Impedance, those targeted at low distortion at around 20% lower power will be between 1 to 1.5 Ohm. mIf you see much higher output impedances you see signs of either ****-poor output transformers or bad (read high distortion) design.
Sayonara
Well, tell Cary that they're using ****-poor o/p transformers.
So, in your 300B example, the source Z looks like about 3 ohms. That's pretty significant.
Bringing in room acoustics is something of a red herring, as you know. Else how come I (and presumably you) can reliably detect frequency response errors of less than half a dB in blind tests? My room is assuredly not an anechoic chamber.
So, in your 300B example, the source Z looks like about 3 ohms. That's pretty significant.
Bringing in room acoustics is something of a red herring, as you know. Else how come I (and presumably you) can reliably detect frequency response errors of less than half a dB in blind tests? My room is assuredly not an anechoic chamber.
Konnichiwa,
The one Cary 300B Amp I tested (used in activating a PMC Studio Monitor on the treble) had around 3 Ohm output Impedance, but arguably we used the 8 Ohm driver on the 4 ohm tap to reflect 5K Primary impedance, which gave clearer sound. Obviously LF control or Crossover Impedances where not an issue here.
In a "competent" design that aims at the best sound as opposed impressive looking (for 300B Valves anyway) poweroutput it will be lower, around halve that.
Depends. Often larger shifts in tonal balance are attained by moving a speaker a few inch and or changing toe in angles a few degrees than are caused by 3 Ohm source impedance.
So if we optimise Speaker/Amplifier in the room we can often compensate the tonal shift due to increased source impedance. Indeed, the increased Q in the low frequencies allows thge speakers to be pulled away from walls, giving at times better soundscaping, the midrange increase caused by a crossover design that is not impedance compensated (bad practice anyway) can often be compensated by shifting the listening point slightly off axis, where many typhical 2 Way speakers show a lack in output. Hence my point about room interactions.
In my view Room/Speaker/Amplifier form a complete system and must be viewed as one system, not three individual ones if we desire realistic reproduction. Failing to do so leads to "High End" speakers inapropriate to virtually any real room, amplifiers inapropriate to most speakers and so on. Stop thinking "interchangable boxes" and start thinking "system" if you desire high performance audio (not you specifically Sy, but any reader who believes in that "boxes" paradigm).
Sayonara
SY said:
The one Cary 300B Amp I tested (used in activating a PMC Studio Monitor on the treble) had around 3 Ohm output Impedance, but arguably we used the 8 Ohm driver on the 4 ohm tap to reflect 5K Primary impedance, which gave clearer sound. Obviously LF control or Crossover Impedances where not an issue here.
SY said:
In a "competent" design that aims at the best sound as opposed impressive looking (for 300B Valves anyway) poweroutput it will be lower, around halve that.
SY said:
Depends. Often larger shifts in tonal balance are attained by moving a speaker a few inch and or changing toe in angles a few degrees than are caused by 3 Ohm source impedance.
So if we optimise Speaker/Amplifier in the room we can often compensate the tonal shift due to increased source impedance. Indeed, the increased Q in the low frequencies allows thge speakers to be pulled away from walls, giving at times better soundscaping, the midrange increase caused by a crossover design that is not impedance compensated (bad practice anyway) can often be compensated by shifting the listening point slightly off axis, where many typhical 2 Way speakers show a lack in output. Hence my point about room interactions.
In my view Room/Speaker/Amplifier form a complete system and must be viewed as one system, not three individual ones if we desire realistic reproduction. Failing to do so leads to "High End" speakers inapropriate to virtually any real room, amplifiers inapropriate to most speakers and so on. Stop thinking "interchangable boxes" and start thinking "system" if you desire high performance audio (not you specifically Sy, but any reader who believes in that "boxes" paradigm).
Sayonara
Well, I don't want to get sidetracked into all the things that can affect frequency response, nor the desirability of design-as-system (in which we have a great deal of agreement).
Factually, the source Zs you're quoting will cause (with ordinary speakers) audible shifts in frequency response. At 3 ohms, QUITE audible. It may be helpful in some specific situations (and a simple passive EQ in front of an efficient amp will do the same thing more reliably and stably), but given the design brief here, I'm not optimistic.
Amp-as-fixed-equalizer is not a generally good thing.
Factually, the source Zs you're quoting will cause (with ordinary speakers) audible shifts in frequency response. At 3 ohms, QUITE audible. It may be helpful in some specific situations (and a simple passive EQ in front of an efficient amp will do the same thing more reliably and stably), but given the design brief here, I'm not optimistic.
Amp-as-fixed-equalizer is not a generally good thing.
Konnichiwa,
To give some perspective, in the late 1930's the German State Radio implemented a new studio monitor, generally known as the Eckmiller. This was a 12" Coaxial driver with Tweeter and woofer voicecoil sharing the same magent circuit 9and airgap, a 2" Voicecoil for both and a special phaseplug for the tweeter that rovided a performance similar to a 1" Dome tweeter by eliminating the cancellation from the large diameter dome. The 12" Cone unit had a system of damping build into the basket that ensured a non-reactive nature of the LF System. The Speaker had a series crossover, 2nd order and was inetnded for use in "infinite baffle" systems.
It provided a sourceimpedance independent frequency response covering around 50Hz to 12...15KHz with good flatness, excellent impulse behaviour, a very even and controlled dispersion pattern and excellent efficency. Now this was possible in the late 1930's, or in other words 65 Years ago. It is appaling to see just how badly the "State of the art" in speakers has been dropping ever since.
Just because most commercial speakers must be classed as complete failures where competent design is concerend does not make such practices "a good thing", it merely makes it a COMMON thing. I would not employ a SE Valve amp with COMMON speakers, as they are commonly incable of high fidelity reproduction ANYWAY, so what's the problem?
I do not recommend using a 300B SE Amp with a pair of LS 3/5 or indeed most "modern" speakers. Using a speaker actually designed to work under domestic conditions and offering "high fidelity" makes all your objections naturally disapper, as such a speaker will not show drastic shifts in tonality with varying source impedance in the regions within which a common DHT SE Amplifier will operate.
So, your criticsm of SE Amplifiers is similar to that which may be levelled at a Ferrari Testarossa attached to agricultural plow. It will perform poorely, simply it is inaproppriatly applied. If you want to drag a plow, get a tractor, not a Ferrari.
It brings me back to the point of system vs. seperate boxes and indeed my point about speakers with positron. A competently engineered speaker will allow any amplifier to perform well, by minimising distortion, compression and room interactions. Such a speaker will work well with a 500W RMS monster amp and a 5W SE Amp....
Sayonara
SY said:
To give some perspective, in the late 1930's the German State Radio implemented a new studio monitor, generally known as the Eckmiller. This was a 12" Coaxial driver with Tweeter and woofer voicecoil sharing the same magent circuit 9and airgap, a 2" Voicecoil for both and a special phaseplug for the tweeter that rovided a performance similar to a 1" Dome tweeter by eliminating the cancellation from the large diameter dome. The 12" Cone unit had a system of damping build into the basket that ensured a non-reactive nature of the LF System. The Speaker had a series crossover, 2nd order and was inetnded for use in "infinite baffle" systems.
It provided a sourceimpedance independent frequency response covering around 50Hz to 12...15KHz with good flatness, excellent impulse behaviour, a very even and controlled dispersion pattern and excellent efficency. Now this was possible in the late 1930's, or in other words 65 Years ago. It is appaling to see just how badly the "State of the art" in speakers has been dropping ever since.
Just because most commercial speakers must be classed as complete failures where competent design is concerend does not make such practices "a good thing", it merely makes it a COMMON thing. I would not employ a SE Valve amp with COMMON speakers, as they are commonly incable of high fidelity reproduction ANYWAY, so what's the problem?
I do not recommend using a 300B SE Amp with a pair of LS 3/5 or indeed most "modern" speakers. Using a speaker actually designed to work under domestic conditions and offering "high fidelity" makes all your objections naturally disapper, as such a speaker will not show drastic shifts in tonality with varying source impedance in the regions within which a common DHT SE Amplifier will operate.
So, your criticsm of SE Amplifiers is similar to that which may be levelled at a Ferrari Testarossa attached to agricultural plow. It will perform poorely, simply it is inaproppriatly applied. If you want to drag a plow, get a tractor, not a Ferrari.
It brings me back to the point of system vs. seperate boxes and indeed my point about speakers with positron. A competently engineered speaker will allow any amplifier to perform well, by minimising distortion, compression and room interactions. Such a speaker will work well with a 500W RMS monster amp and a 5W SE Amp....
Sayonara
I used a high-end Snell speaker's curve as my basis of comparison. I daresay that Kevin Voecks designed the speaker for home use. You can consider him an incompetent designer, if you like. To my flannel ears, the speaker sounded pretty darn good.
Konnichiwa,
How is the impulse fidelity, power compression, distortion and LF Loading (LF Impulse fidelity AND impedance)?
That may be so. I know some people to whome Lowthers in bass Reflex Boxes sound pretty darn good. Does that make them speakers capable of high fidelity?
May I suggest that these are build like most others simply because as commercial products they compete in the same market for the same custormers?
Sayonara
SY said:
How is the impulse fidelity, power compression, distortion and LF Loading (LF Impulse fidelity AND impedance)?
SY said:
That may be so. I know some people to whome Lowthers in bass Reflex Boxes sound pretty darn good. Does that make them speakers capable of high fidelity?
May I suggest that these are build like most others simply because as commercial products they compete in the same market for the same custormers?
Sayonara
Ralph, my views on SE amps parallel those of Angel. I happened to login today and noticed a whole lot of very interesting discussions. I quote from one of my previous discussions in this forum.
"By the way, 300B curves look linear in print. However, let us for a moment think about the load line that you have drawn on a set of curves. We all know that a loudspeaker impedance changes with frequency and that your output transformer has a 20:1 turns ratio. Now let us think about what happens in real time when music is played. As the impedance of the speaker changes, the load reflected back to the primary and thus to the 300B is magnified in proportion - square of the
turns ratio. In other words, the load line rotates up and down swinging from the operating point. In other words, there is no perfectly linear device available to us in real time. We just have to cop it on the chin as we forgive ourselves for all of our inconsistencies. There is a way to minimise this and that is by selecting a tube that has low internal resistance. There is no win win situation here, only better compromises."
I am in Melbourne, Australia. Where are you located? Most welcome to have a free chat.
Regards,
Mohan
"By the way, 300B curves look linear in print. However, let us for a moment think about the load line that you have drawn on a set of curves. We all know that a loudspeaker impedance changes with frequency and that your output transformer has a 20:1 turns ratio. Now let us think about what happens in real time when music is played. As the impedance of the speaker changes, the load reflected back to the primary and thus to the 300B is magnified in proportion - square of the
turns ratio. In other words, the load line rotates up and down swinging from the operating point. In other words, there is no perfectly linear device available to us in real time. We just have to cop it on the chin as we forgive ourselves for all of our inconsistencies. There is a way to minimise this and that is by selecting a tube that has low internal resistance. There is no win win situation here, only better compromises."
I am in Melbourne, Australia. Where are you located? Most welcome to have a free chat.
Regards,
Mohan
Has anyone got an opinion on the Walton Audio Amplifier?
http://indigo.ie/~walton/300bmk2.html
There is a more detailed section for his first version
http://indigo.ie/~walton/300b.html
It still appears to me that the 300B is the simplest to build at this stage.
http://indigo.ie/~walton/300bmk2.html
There is a more detailed section for his first version
http://indigo.ie/~walton/300b.html
It still appears to me that the 300B is the simplest to build at this stage.
I actually met Derek Walton at the Dublin hi-fi show where he had rented space to showcase his amplifiers more though in the spirit of offering his services for hand-made amps to interested parties but not really as a business venture.I had a chance to talk to him because I am also intersted in building a 300b and we spoke on the phone in order to arrange a further meeting.Very nice and enthusiastic person.However he has completely dropped out of sight in the last few months and all my efforts to contact him have had no result.
His website is great for anyone wishing to build a 300b and quite detailed and simple.
The only caveat seems to me that some experts recommend a good two stage driver for the 300b while he has adopted only a 6sn7 driver approach.
Another good site is the Plitron site where there are a couple of good articles reprinted on a stereo 300b set and a push-pull version with the seemingly excellent plitron trafos.
I would also appreciate the opinion of the "experts" here on what in their humble opinion is the best 300b circuit including the question on tube or silicon rectification , choke vs transistor regulation , grid bias regulation etc.
His website is great for anyone wishing to build a 300b and quite detailed and simple.
The only caveat seems to me that some experts recommend a good two stage driver for the 300b while he has adopted only a 6sn7 driver approach.
Another good site is the Plitron site where there are a couple of good articles reprinted on a stereo 300b set and a push-pull version with the seemingly excellent plitron trafos.
I would also appreciate the opinion of the "experts" here on what in their humble opinion is the best 300b circuit including the question on tube or silicon rectification , choke vs transistor regulation , grid bias regulation etc.
protos said:
I'm no expert, but as has often been stated on this forum, there is no *best* 🙂 circuit or design; its more a matter of taste. Also, you have to address what your goals are, your budget, your abilities, and where are you willing to compromise.
Having said that though
and with the necessary disclaimers, I will offer the following:I would never recommend a 6SN7 as driver for a 300B.
I would recommend a 6V6 (triode strapped) or other pentode, or other triode as driver.
I would not recommend a two stage approach. "Everything should be made as simple as possible, but not simpler." Alot of people view the two stage amp as the simple and purer approach to designing. Afterall, less parts, less wire, shorter circuit path, what could be more perfect. For me, that viewpoint is flawed in the sense that you are now asking a smaller number of parts to do multiple duties. Which then creates complex interactions which then limits the number of available driver choices down to a few high gain tubes (like 6c45pi). And these tubes, if they aren't rare and expensive NOS, are current production russian which have their own idioyncrasies in terms of their application. So why invite unecessary headaches? And on top of that, a two stage amp in most cases requires you to have an active preamp. Which is basically the third stage which you dropped from the front of the amp because you wanted to *KISS*.
Therefore, for me a three stage approach is best; it allows you the freedom of choice in terms of tubes and topographies. And the use of a passive volume control like a TVC or autoformer which hands down beats all active preamps, period.
An unbypassed 1/2 6SN7 loaded with a 68K-100K resistor makes a darn good voltage amplifier as input tube. A triode-strapped pentode loaded with a choke in series with a resistor would make a decent driver. Cap coupling between stages. If you're game and are cathode self-biasing then direct coupling might be a choice to consider.
Keep the power supply for the output stage separate from the power supply for the input/driver stages. Basically, build two full supplies, complete with CLCLC filtering for each B+. The needs of the output tubes are different than the needs of the input/drivers. Separating the supplies allows each tube to be properly loaded. And while you're at it, and since at this point who cares about costs
use fixed bias on both the drivers and output tubes. Thereby eliminating the big cathode resistors and electrolytic bypass caps; and since you have left the 6SN7 unbypased, you have just eliminated a number of parts which if left in would add nasty colorations the sonic signature of the amp. AND thereby also eliminating the need for matched pairs anywhere in the amp. Afterall, *matched pairs* of tubes is the biggest myth in tube audio. AND thereby, giving you complete control of the op of each tube.Use hybrid rectification, combining tube and silicon rectifiers. Hexfreds or the recently introduced high voltage Schottkys. Better controlled bass response.
Use separate filament supplies for each DHT or shared supply for IDHTs. Use separate filament transformers. DC heated. RCLC filtering.
And finally, keep the power supply on a separate chassis than the circuit components. Connect with a properly shielded umbilical. Keep the last LC or RC section of each PS on the amp chassis. Place the last cap of the DC filament supply right at the filament tabs of the tube sockets. Star ground.
And one more thing, use high quality parts throughout. Especially iron.
Basically, I've just described to you my amp. And since its my first DIY amp, and also a scratch build, and when I started the amp, I knew nothing about electronics, much less amp building or design, I make no claim to being an expert. But, now after 2.5 years of working on this amp, I do have a little experience. So take my humble suggestions FW their W. 😉
Here is a pic:
An externally hosted image should be here but it was not working when we last tested it.
Well....
Actually it is a matter of whether one wants to outboard the first stage or not; with an additional selector switch.
True, one would need an IC, but then you don't have to contend with signal interaction through the power supply. It is frequency related, bass and then highs the most vunurable. Really messes with the sonics. I prefer the separation and although it costs much more, the sound is better.
Steve
SAS Audio
Actually it is a matter of whether one wants to outboard the first stage or not; with an additional selector switch.
True, one would need an IC, but then you don't have to contend with signal interaction through the power supply. It is frequency related, bass and then highs the most vunurable. Really messes with the sonics. I prefer the separation and although it costs much more, the sound is better.
Steve
SAS Audio
Konnichiwa,
Well, the subject is complex. First a few notes on gain. If you use the russian 6S45 or any of the following - EC8010, EC8020, WE 417A, WE 437A or triode wired Pentodes like E810F/7788 / E280F / E180F/6688 / E55L et al you can have a driverstahe that can drive the 300B at normal Operating Points (350V60...80mA) to full power with around 0.9 - 1.3V, so with a normal CD Player your systemn is in essence gainmatched with a unity gain Preamp (passive or active), meaning the Amplifier will never receive an input signal that is over around 6db above it's clipping point with the volume full up.
A TVC makes an excellent choice in this case. Daisychaning a pair of 6SN7 Halves or the like not only produces a lot of distortion prior to the outputstage with a lot of upper harmonics, in addition it will also drive the 300B to clipping with around 0.25 - 0.4V RMS, meaning between 8 - 12db attenuation will be always needed.
So you gain nothing by using a dual stage driver, but you loose transparencey and tonality, plus you are ging to be further away from the best sounding range of the TVC (contrary to common misconception the TVC is best turned all the way up!!!) should you use one.
So, unless you need to accomodate very low output sources having more than one driverstage gives no benefit.
The best solution to maximising the performance of such an amplifier IMHO is to use directcoupling with one of the possible variations of the DRD/Monkey/FreeLunch/Stacked Supplies approach, in all cases using a Anode load choke (Tangoe TC160-15 or suitable items from Stevens & Billington, Electraprint or Magnequest).
My gut feeling favours a "stacked supplies free lunch" with a seperate valve rectified supply for the driver and a suitable RL series combo to provide the bias for the Output Valve. In this case you need a suitable interlock that can be conveniently be applied from a Relais that will power up the HT for the output stage once the driver valve draws enough current to bias the output stage.
As for rectification, it is possible to make solid state rectifiers sound very close to Valve ones, but it takes a lot of effort and is poorely documented. The valve rectifier serves two sides for good sound. On one hand it's soft turnon and lack of rectifier noise are hard to match with solid state and secondly, the fairly high power AC heater of the rectifier provides a steady load for the Mains transformer, thus damping the tendency of the transformer to oscillate when current pulses from the rectification of the HT or Heater Voltage try excite the parasitic resonances.
Ideally you use a LCLC or CLCLC Filter with a small first C to bring the supply as close to a choke input supply as possible, with LCLC supplies you can eliminate for all practical purposes any +B supply related noise, so you get an inherently "quiet" rectification and a very clean supply even when using Film or Oil Capacitors (highly recommended).
So an option would be a 350V supply using a WE 274A/B or 5R4GY (or 5AR4/GZ34) in LCLC for the 300B. Add to this a supply with around 250V +B for the driverstage, rectified for example with a 6X5, WE420A or EZ80 and CLCLC filtering. Driver valve of choice would be E55L or E810F or WE 437A, for my taste....
If this is combined with a suitable LC filtered DC supply for the 300B Heaters you would be very close to "edge of art", assuming of course high performance Transformers, chokes etc.
If you have multiple taps on the +B for the Output Valve (maybe including more Current and Voltage for the "super 300B's" and maybe something like a Tango XE20S as Output Transformer plus a pot to adjust the Bias (in series with the anode load choke) and selectable Heater Voltages (2.5V AC, 4V/5V/6.3V/7.5V DC) you can use a wide range of output valves (if you make easily exchanged socket plates even european oddballs), de facto making the amplifier "universal" and making sure you can run whatever valves you get hold of....
Of course, such an Amp would be quite a monster in size and weight, fitted with 2 pcs Mains Transformer, 5 pcs substantial size input/filter chokes, 4 - 5 pcs large Film or Oil PSU Capacitors plus output transformer and anode load choke. And it will be a layout nightmare if you want to avoid magnetic coupling. Of course monoblock chassis with Bronze, Brass or Copper top plate and wooden frame.
Well, it would make for a stonking Amp and yes, it would cost an arm and a leg if you build this kind of design consequently enough, BUT I'm pretty confident it will require a Badge with the incription "Beware - Kicks Butt", despite giving only 1.5 Watt when fitted with a #45!
So, anyway, that's my take for "the best 300B Amp I can come up with if money, space and time are infinite".
Sayonara
protos said:
Well, the subject is complex. First a few notes on gain. If you use the russian 6S45 or any of the following - EC8010, EC8020, WE 417A, WE 437A or triode wired Pentodes like E810F/7788 / E280F / E180F/6688 / E55L et al you can have a driverstahe that can drive the 300B at normal Operating Points (350V60...80mA) to full power with around 0.9 - 1.3V, so with a normal CD Player your systemn is in essence gainmatched with a unity gain Preamp (passive or active), meaning the Amplifier will never receive an input signal that is over around 6db above it's clipping point with the volume full up.
A TVC makes an excellent choice in this case. Daisychaning a pair of 6SN7 Halves or the like not only produces a lot of distortion prior to the outputstage with a lot of upper harmonics, in addition it will also drive the 300B to clipping with around 0.25 - 0.4V RMS, meaning between 8 - 12db attenuation will be always needed.
So you gain nothing by using a dual stage driver, but you loose transparencey and tonality, plus you are ging to be further away from the best sounding range of the TVC (contrary to common misconception the TVC is best turned all the way up!!!) should you use one.
So, unless you need to accomodate very low output sources having more than one driverstage gives no benefit.
The best solution to maximising the performance of such an amplifier IMHO is to use directcoupling with one of the possible variations of the DRD/Monkey/FreeLunch/Stacked Supplies approach, in all cases using a Anode load choke (Tangoe TC160-15 or suitable items from Stevens & Billington, Electraprint or Magnequest).
My gut feeling favours a "stacked supplies free lunch" with a seperate valve rectified supply for the driver and a suitable RL series combo to provide the bias for the Output Valve. In this case you need a suitable interlock that can be conveniently be applied from a Relais that will power up the HT for the output stage once the driver valve draws enough current to bias the output stage.
As for rectification, it is possible to make solid state rectifiers sound very close to Valve ones, but it takes a lot of effort and is poorely documented. The valve rectifier serves two sides for good sound. On one hand it's soft turnon and lack of rectifier noise are hard to match with solid state and secondly, the fairly high power AC heater of the rectifier provides a steady load for the Mains transformer, thus damping the tendency of the transformer to oscillate when current pulses from the rectification of the HT or Heater Voltage try excite the parasitic resonances.
Ideally you use a LCLC or CLCLC Filter with a small first C to bring the supply as close to a choke input supply as possible, with LCLC supplies you can eliminate for all practical purposes any +B supply related noise, so you get an inherently "quiet" rectification and a very clean supply even when using Film or Oil Capacitors (highly recommended).
So an option would be a 350V supply using a WE 274A/B or 5R4GY (or 5AR4/GZ34) in LCLC for the 300B. Add to this a supply with around 250V +B for the driverstage, rectified for example with a 6X5, WE420A or EZ80 and CLCLC filtering. Driver valve of choice would be E55L or E810F or WE 437A, for my taste....
If this is combined with a suitable LC filtered DC supply for the 300B Heaters you would be very close to "edge of art", assuming of course high performance Transformers, chokes etc.
If you have multiple taps on the +B for the Output Valve (maybe including more Current and Voltage for the "super 300B's" and maybe something like a Tango XE20S as Output Transformer plus a pot to adjust the Bias (in series with the anode load choke) and selectable Heater Voltages (2.5V AC, 4V/5V/6.3V/7.5V DC) you can use a wide range of output valves (if you make easily exchanged socket plates even european oddballs), de facto making the amplifier "universal" and making sure you can run whatever valves you get hold of....
Of course, such an Amp would be quite a monster in size and weight, fitted with 2 pcs Mains Transformer, 5 pcs substantial size input/filter chokes, 4 - 5 pcs large Film or Oil PSU Capacitors plus output transformer and anode load choke. And it will be a layout nightmare if you want to avoid magnetic coupling. Of course monoblock chassis with Bronze, Brass or Copper top plate and wooden frame.
Well, it would make for a stonking Amp and yes, it would cost an arm and a leg if you build this kind of design consequently enough, BUT I'm pretty confident it will require a Badge with the incription "Beware - Kicks Butt", despite giving only 1.5 Watt when fitted with a #45!
So, anyway, that's my take for "the best 300B Amp I can come up with if money, space and time are infinite".
Sayonara
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