Topic: tube vs. ss rectified preamp

[JojoD818]

hi Tony,

the points on your post are absolutely correct, "electrically speaking". it has been proven decades ago that ss rectification is far more efficient than tubes but why does everybody keep on going back to tubes? maybe because people like what they hear, right?

try to consider this also... an amp with tube rectification is being fed such a signal that it approaches clipping, what happens to the psu? it sags... therefore instead of a clipped signal what we have is a squashed signal, more of a soft clipping as they say.

now consider the same amp with an ss rectified psu with such efficiency (that all ss rectifiers proudly have) and feed the same magnitude of signal that it is forced into clipping, now due to the ss rectifiers efficiency, the psu can cope and maintain current versus voltage thereby forcing the amp into hard clipping.

my ears will gladly take soft clipping any day rather than hard clipping on a sunday.

i'm not an expert on these, in fact I also consider myself a newbie too. 

cheers,
JojoD

[ATJr.]

Hi 2ny, isn't it ideally for DC Power Supply it should be flat line (oscilloscope test) same with batteries? But for audio application (referring to tube Amplifiers)  I'm curious why capacitors rating  are too low? Isn't it by having bigger value capacitors (let say 10Kuf up) would reduce ripple factor?

well it depends on the resolution of your scope! and when loaded, all the more ripple shows up. elecrtos are smaller for tube circuits because of the currents and impedances involved are much to higher for tubes than for ss. however, let no one prevent you from using higher valued electros in your diy projects, cost will be your limit, plus the law on diminishing returns applies!

frank's ultimate tube preamp uses largish caps and even bigger traffo rated 300va in a monoblock where actual power consumption will not be more than 30watts! diy gives the designer more freedom to choose, he is not constrained with costs.

[ATJr.]

now consider the same amp with an ss rectified psu with such efficiency (that all ss rectifiers proudly have) and feed the same magnitude of signal that it is forced into clipping, now due to the ss rectifiers efficiency, the psu can cope and maintain current versus voltage thereby forcing the amp into hard clipping.

i am not sure i understand exactly what you mean, but for a tube rectified amp, replacing it with ss rects would mean that power otherwise lost in the tube rectifiers is now available for the amp,some 15watts at least! that is why operating point changes as what arnoldc stated in his post:

what you heard in sonic difference is the change in operating point, you increased the B+

btw, clipping is a function of input signal! all amps can be driven into clipping due to the fact that its psu does not posses infinite power! as with all amps be they tube or ss, if we want to avoid clipping, then we should not feed the amp signals that it can not handle! sure thing, tubes clips gracefully than ss!

i compared tube and ss rectifiers on two counts, efficiency and transformer untilization! there is no arguing if you like the sound of tube rectified amps or vice versa, after all it is your ears that matters.

with today's ever increasing cost of meralco power, looking at them from the perspective of efficiency makes sense, at least to me!

more on the traffo side:

since tube rects are almost always fed from a center-tapped winding, there is always that unbalanced coil resistance/impedance because there is an inner and an outer winding! this condition creates a magnetising effect due to that fact that half of the time, a half segment is doing nothing, ie., not conducting current. this explains in part why tube rectified traffos run very hot!
that is why i make my traffos with biffiliar secondary windings, these way, both halves are of equal resistance!

[JojoD818]

what I'm saying is that tube rectification offers some compression therefore providing soft clipping rather than hard clipping because the psu sags with higher input signal. i beleive ss rectification in all it's efficiency will try and maintain supply voltage, and with all things being equal, an ss rectified amp will surely be clipping while a tube rectified amp compresses the signal and thereby squashes the corners of clipping.

all amps can be driven into clipping true, and my experiments shows that (again all things being equal) an ss rectified amp goes into clipping sooner than a tube rectified amp.

loosing power due to tube rectification can be seen as bad engineering but it offers something an ss rectifier cannot. besides the designer should take into account all this losses and would automatically adjust for allowance. for the issue of meralco bills... that is another story. Besides, it's the heaters that requires/consumes a lot of energy.

again, i don't mean to say that tubes are better than ss rectifiers, electrically, my gut is telling me that tubes are no match to ss when it comes to efficiency, but who listens to efficiency?

[ATJr.]

compression

ahh, the technique used by audio recording engineers to record as much material unto tapes and vynils!
the power supply, either tubed or ss is supplying dc to amp circuits, since they have internal resistances, they will sag when loaded, this is what we call "regulation" a 0% regulation power supply will have zero internal resistance, such psu is not invented yet!

compression and clipping happens in the amps, not in the psu!

the clipping point in any amp is not determined by either tube or ss rectification alone! it is the function of the input signal and the stiffness of the psu! it is very hard to generalise and say that ss rectified amp goes into clippping sooner than tube rectified one! we have to see the topology and investigate!

but then again, in the area of subjectivity, there are no arguments! just all plain ears!

in that case i say no more!

[odyopayl]

well it depends on the resolution of your scope! and when loaded, all the more ripple shows up. elecrtos are smaller for tube circuits because of the currents and impedances involved are much to higher for tubes than for ss. however, let no one prevent you from using higher valued electros in your diy projects, cost will be your limit, plus the law on diminishing returns applies!

frank's ultimate tube preamp uses largish caps and even bigger traffo rated 300va in a monoblock where actual power consumption will not be more than 30watts! diy gives the designer more freedom to choose, he is not constrained with costs.

Thanks 2ny.

[JojoD818]

ahh, the technique used by audio recording engineers to record as much material unto tapes and vynils!
the power supply, either tubed or ss is supplying dc to amp circuits, since they have internal resistances, they will sag when loaded, this is what we call "regulation" a 0% regulation power supply will have zero internal resistance, such psu is not invented yet!

i know, but ss amp circuits tends to distort too with varying supply due to PSRR but that is already known, besides ripple increases when load increases but you already know that. incidently, tube psu also has higher psu impedance than ss psu.

compression and clipping happens in the amps, not in the psu!

of course they don't, what I'm saying is that tube amps with tube rectifiers tend to compress clipping while the same amp with ss rectification tends to have more power that the amp has hard clipping with the same amount of input signal.

the clipping point in any amp is not determined by either tube or ss rectification alone! it is the function of the input signal and the stiffness of the psu! it is very hard to say that ss rectified amp goes into clippping sooner than tube rectified one! we have to see the topology and investigate!

you said it... clipping is a function of the stiffness of the psu, therefore if ss rectifiers are such efficient devices then they must resist sag under load right?

if you have 2 completely identical tube amps, one uses ss and the other uses tube rectification and is subjected to the same magnitude of input signal with the same load, which one clips sooner?

but then again, in the area of subjectivity, there are no arguments! just all plain ears!

master Tony, I believe we are in agreement that electronics (or electrical characteristic) is not in the area of subjectivity rather an exact science, something that can be repeated over and over provided that all other things are maintained equal. correct?

in that case i say no more!

c'mon, this is a healthy discussion, i mean no disrespect. this way we both learn from one another and from others.

regards

[eXg]

allow me with a little diversion....

i saw this "metal tube rectifiier"... actually it's not a tube but a SS rect trying to operate as tube rect.  unfortunately, can't remember where i saw them being peddled.  they are drop in replacements of, say 5u4g tube...

are these good? i mean do they behave as SS or tube rects?

[ATJr.]

allow me with a little diversion....

i saw this "metal tube rectifiier"... actually it's not a tube but a SS rect trying to operate as tube rect.  unfortunately, can't remember where i saw them being peddled.  they are drop in replacements of, say 5u4g tube...

are these good? i mean do they behave as SS or tube rects?

tube rects is tube rects, but with that drop in replacement, expect a few watts more of output! here is what happens when you insert that ss rect, about 15watts of filament power eaten by the 5U4 tube from the poer traffo before is now available!

but if i were you i would not just drop them in without some minor circuit modifications, like cutting one side of the 5volt 5U4 heater supply and taping it to be safe! another ould be the incorporating of a standby switch aside from the main switch to give the filaments ample time to heat up before turning on the B+, a switch to the traffo center tap to ground is all that is needed.

[JojoD818]

sir 2ny,

mas magiging malakas ba yun output kapag na-convert to ss rectifier yun amp na tube rectified? yun 15 watts available power sa transformer yun 3A X 5V yun diba?

eXg,

si iceman muntik na bumili nyan for his ST70, di ko lang sure kung natuloy.

[ATJr.]

mas magiging malakas ba yun output kapag na-convert to ss rectifier yun amp na tube rectified? yun 15 watts available power sa transformer yun 3A X 5V yun diba?

yes, the physical construction of the power traffo is such that, voltage, current, and winding resistances are fixed. the implication of this is that there is a fixed output that is available. now changing from a tube rect to an ss rect. obviously will provide for a greater output simply because of the intrinsic effficiency of the ss diode! this is known as early as before you were even born!

i cited the heater loss for a 5U4 which is 5volts@3amps, you can add another 10watts for the plate loss!

[JojoD818]

so your answer is back to efficiency. i thought there was something else.

[ATJr.]

if you notice, i try to put figures in my posts to make my points clearer, as Lord Kelvin would put it, "If you can not reduce into numbers the things that you say, then your knowledge of the subject must be of the meager kind"

[JojoD818]

the observations on my posts came from real world experiments, I didn't read them in a book. in an electronics standpoint, the use of ss rectifiers on tube amps can be justified for their efficiency and cost. but do you like the sound a tube amp with ss rectifiers on board? if you do, then that's good for you.

putting numbers to prove that tube rectifiers are meager compared to ss rectifiers doesn't justify their use if the sonics and overall character of an amp goes to the recycle bin. but that's just me... or is it just me? it's funny really, but in reality, people care less about watts lost or watts used... all they care about is how their gear sounds.

and they don't even know how to reduce or deduce into numbers what they say, words like clarity, imaging, soundstage and many more. this could only mean that they have a meager knowledge of what they are saying.

have a nice weekend

[ATJr.]

the observations on my posts came from real world experiments, I didn't read them in a book.

all the more reason to find out from books what you have observed! there is nothing new under the tube sun! tube is a matured technology, there is nothing you can obverve on your own that has not been observed before! nothing you ever make that hasn'st been made before! we do not worship originality for originality's sake! whe do not have to reinvent the wheel every time!

there is no shame in learning from others, guys like thorstein, prr, sy, fedgrove and others are excellent teachers, just like john curl, nelson pass and others, 

there is no shame in being a copycat! look at what japan is today,  they used to send their engineers overseas on plant tours just to learn as much from machineries they come to see on such tours!

and they don't even know how to reduce or deduce into numbers what they say, words like clarity, imaging, soundstage and many more. this could only mean that they have a meager knowledge of what they are saying.

that would fall into what we call subjectivity, pag ganyan ang usapan, wa na ko say!

[JojoD818]

we all know that, even ss has it's share of history. that's why your lecture on ss efficiency is not new likewise. what's real is that while you are so amazed about ss efficiency and the watts and power that comes with it, new production tube amps still comes with tube rectifiers and for what? why can't they entirely eliminate vacuum state in the psu?

who says anything about shame? even Frank suggests tube regulators in his ultimate preamp right? or did he also suggest a tube rectifier? alas, the names you mentioned are highly regarded in the field of electronics, much like yourself.

a word on subjectivity, i try not to cinvince myself as to what my peers like, if it sounds good, then i like it. i don't care what they say but i don't stick it to them - i keep it to myself.

enough with history, so what's it gonna be? let our ears decide or our computation and understanding of how efficient is the psu? 

[ATJr.]

why can't they entirely eliminate vacuum state in the psu?

because the amp business is all about business! for as long as there are consumers who can be convinced or led to believe  that tube rects sound better than ss rectified ones, there will always be amps using tube rects. if a costumer asks me to put in a tube rect, why shouldn't i?

and i say it does not make any difference, a tube amp is only as good as the sum of its parts and the iron in the output transformer! tubes operating points can be tweaked, but output traffos are fixed items that once installed, that is it.

when someone tells me that tube rectified amps sound better than ss rectified one, i make sure that he is not somebody selling tube rects or amps with tube rects!LOLZ

[JojoD818]

i built the same tube amp with both tube and ss rectifiers (with some mods on the ss to provide the same operating point of course), the difference in power is of course to the ss rectifier as it easily compensates for voltage sags in dynamic passages but the sonic difference of the tube rectifier is very noticieable and is more favoreable when listening for longer periods. but it is undeniable that ss rectifiers can wallop a lot of punch when listening to rock music. however, big band music is more realistic in tube rectifiers even with the amp suffering from voltage sag with loud passages.

alas, i agree with the business is business issue, but it is a bit a stupid reason for a manufacturer to put a tube rectifier just to increase their revenues.  and on the issue of irons, 100% agree on the importance of irons. my friend said that it is sometimes better to use surplus irons from old trannies because of higher quality irons used rather than buy the per kilo ones. this is bothering since a lot of current production tube amps use new materials for their transformers.

that's the reason why i scoured for a pair of old, busted A470 trannies used in the ST70 for my tube amp trannies. i hope the quality of irons available locally become better. 

[ATJr.]

hey jojo,
i do not see any tube rects on the 807 set amp TONO Personal, don't you think arnoldc and company agrees with me?

[s2kov]

even frank's ultimate preamp uses ss rectifier!

[ATJr.]

even frank's ultimate preamp uses ss rectifier!

and a 300va traffo to boot, talk about overkill?

i asked fedgrove about the possibility of using ss regulated supply in lieu of tube regs, and he raised no qualms about it at all!

[AMXTube]

If I may add my experience with SS rectifiers sirs: SS rectifiers produce high frequency noise as it swirches on and the can affect high frequency response. As observed a possible increase in sibilance. But this is easy to remedy by bypassing the the rectifiers with small capacitors, that should reduce the high frequency switching noise. To further simulate the operation of a rectifier tube you may want to put in series a small resistor to your ss rectifier which will simulate the voltage drop. As you current demand increases the voltage drop will increase and therefore decrease the output voltage.

[JojoD818]

hey jojo,
i do not see any tube rects on the 807 set amp TONO Personal, don't you think arnoldc and company agrees with me?

to put it bluntly, I don't care even if the whole WS team agrees with you sir, it won't change my findings. 

[JojoD818]

If I may add my experience with SS rectifiers sirs: SS rectifiers produce high frequency noise as it swirches on and the can affect high frequency response. As observed a possible increase in sibilance. But this is easy to remedy by bypassing the the rectifiers with small capacitors, that should reduce the high frequency switching noise. To further simulate the operation of a rectifier tube you may want to put in series a small resistor to your ss rectifier which will simulate the voltage drop. As you current demand increases the voltage drop will increase and therefore decrease the output voltage.

excellent remedy there sir, not only it simulates tube rectifiers, it also increases the overall supply impedance.

thanks for the input.

[JojoD818]

even frank's ultimate preamp uses ss rectifier!

I'm not stopping you from using ss rectifiers! Even the Foreplay uses it I know.

It's your project not mine so use whatever you like, besides, I'm talking of amps and your talking about preamps.

 

[JojoD818]

and a 300va traffo to boot, talk about overkill?

i asked fedgrove about the possibility of using ss regulated supply in lieu of tube regs, and he raised no qualms about it at all!

go for it, the Conrad Johnson series of preamps uses MJE340 (which I know you have lot's of  ) as series pass regulators.

oh, even the Basie MK2 that uses tube rectifers have ss regulators. 

[s2kov]

hehehe! mukhang naligaw ako, akala ko kc nasa "tube vs. ss rectified preamp" thread ako!


joke, joke, joke......

I'm not stopping you from using ss rectifiers! Even the Foreplay uses it I know.

It's your project not mine so use whatever you like, besides, I'm talking of amps and your talking about preamps.

 

[ATJr.]

SS rectifiers produce high frequency noise as it switches on and the can affect high frequency response.

this will be in the form of high frequency hissing sounds coming out from the tweeters! indication that filtering needs to be improved, however depends on the level. snubbers are helpful here!

[JojoD818]

hehehe! mukhang naligaw ako, akala ko kc nasa "tube vs. ss rectified preamp" thread ako!


joke, joke, joke......

pre di ka nagiisa, pati ako naliligaw din ng thread minsan. 

[ATJr.]

there is a nice post by fedgrove at diyaudio, post no46:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=12042&perpage=10&highlight=&pagenumber=5

and about rectifier diodes:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12539&perpage=10&pagenumber=1

what do you think?