All of this makes complete sense to me, and I think most would agree. I was questioning whether someone could truly say that a NOS GE 5U4 sounds "amazing, detailed, fluid, blah, blah blah" compared to a NOS Sylvania 5U4, for example. (Both probably made by Mullard in the same factory).
My new SET amp will have a SS rectification option so I will soon learn about the difference in sound between SS and tube rectification.
That's a relief. I thought I was starting to lose it.
Thanks for your patience (same to the rest of you)!
Part of the story -- more importantly, the impedance of a vacuum tube rectifier isn't quite linear.
Semiconductor rectifiers -- have junction capacitance which is inversely related to applied voltage and impedance which is a function of temperature.
Tube rectifiers have their place. IMHO they belong in guitar/bass amps, and museums. Oh they made some excellent vacuum diodes. Look at the 6D22S for instance. Still... You don't need to light up a SS diode. Let SS do what it's good at, and use tubes for that they are good at! Just saying 😀
In an instrument amp, they cause compression I believe. They become PART of the instrument along with the guitar, the player, and the amp stages. Distortion is purposeful.
In hi-fi it's quite the opposite, right? You want you "amp" to "make the input signal bigger" and not add or remove anything...
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When the B+ caps were **** in my 1968 Hammond H182 organ in 2010, bass sounded like ****. The amount of electrons available to the output tubes could not sustain a wave through a whole 30 millisec at the draw the 7591's were demanding.
New 100 mf B+, it will rattle the chandelier with pure sine wave (flute) bass.
Since the allowable load capacitance on a given rectifier tube is not much compared to the demand of a pair of 7591, 6L6, 6CA7, (40-100 uf) then the sag of the rectifier tube may very well be audible in the bass notes. Different shaped tops have different sounds, with squared off tops being a bit clarinet like, to use a pipe organ term. Round sine tops are "flute".
The trouble with SS rectification is not the current supplied, it is the RF riding on top of the waveform from the sharp cutoff. In this case schottky and fast recovery rectifiers are worse than plain old first generation silicon rectifier diodes. Fast recovery diodes are for TV circuits, not audio IMHO. .01 uf ceramic snubbers across the bridge help a lot, too. Output tubes can pick up all this buzzy RF, since they are inherently very fast response devices.
See this thread about rectifier buzz: DC heater noise
New 100 mf B+, it will rattle the chandelier with pure sine wave (flute) bass.
Since the allowable load capacitance on a given rectifier tube is not much compared to the demand of a pair of 7591, 6L6, 6CA7, (40-100 uf) then the sag of the rectifier tube may very well be audible in the bass notes. Different shaped tops have different sounds, with squared off tops being a bit clarinet like, to use a pipe organ term. Round sine tops are "flute".
The trouble with SS rectification is not the current supplied, it is the RF riding on top of the waveform from the sharp cutoff. In this case schottky and fast recovery rectifiers are worse than plain old first generation silicon rectifier diodes. Fast recovery diodes are for TV circuits, not audio IMHO. .01 uf ceramic snubbers across the bridge help a lot, too. Output tubes can pick up all this buzzy RF, since they are inherently very fast response devices.
See this thread about rectifier buzz: DC heater noise
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The "wire with gain" idea. I've seen it said a million times and I get the point, for sure.
On the other hand, I have read just as many times that a bit of 2nd harmonic can create a truly enjoyable listening experience.
I need to find this out for myself. At this point I know I like the sound of my EL34 PP (SS rectified) better than the solid state amplifier options that I have. I'll refrain from using meaningless language to try to say why. I just do.
With the SET I am building, I want to push the envelope of "tube sound" and really get a feel for what I do (and do not) like about it.
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Thanks for your reply! An interesting quote from that link: "Note that sag effectively only occurs in class AB amplifier output stages. A true class A amplifier has no sag because the current draw at full power is the same as the current draw at idle. However, most class A amplifiers aren't biased exactly at the midpoint of the range, and will tend to clip asymmetrically, especially when going into grid clamp on the output tubes, so there will be an offset current component, but it will be much smaller than in a class AB output stage."
I am pretty sure the SET I am building (Tubelab SSE) is class A (most SETs are, right?) so perhaps rectifier sag is not going to be a big issue in my amp? I suspect the clipping issue is moot because I am not going to drive my SET into clipping (the way a guitarist might push a guitar amp).
Wrong.
I use Si diodes to bring up the main choke input filtered anode supply, which has a shunt regulator wired across it, that gives a totally steady 300V feed for the AF amp.
Up comes the stable 630V HT, with a stable initial load, so that when the g2 circuit comes up it drops to a steady 525V.
The supply that feeds the screen grids and drivers uses a valve rectifier, C-L-C because the load doesn't change, and the supply is stable.
This brings it all up nice and gently.
When tested under full loads, (80W) the supply still DID still dip very strongly, because the greatest sag in a high power amplifier COMES FROM THE MAINS TRANSFORMER!
Forget this nonsense about valve rectifiers, if you have a proper supply they have NO effect on sound at all. 🙄
Kodabmx i agree . These russian tubes is damper diodes used in TV sets,better for HV rectification,about 1000v,very good for use in big SE amplifiers who uses transmitting tubes,or HF tube linears. SS rectifiers is not so good in HV,it is unstable ,and needs soft start circuit,for tubes protection. I see SS rectifiers to bang like a gun in a diy HF linear!
My amps are 55yrs old and have Si rectifiers since the beginning.
They deliver up to 675V DC.
Never ever seen one go wrong, and they were 24/24 365 service units.
My 70 yr old amps are now fitted with Si diodes for the (anode) main rail.
Perfectly trouble free.
Then you need a larger transformer IMHO. My monoblocs drop 5V from silent to full power (112W, triode connected) and they use a Delon doubler. The PS transformers are each 572VA.
Agreed if you have a properly built supply there SHOULD be no difference (I said this near the beginning of this thread) in the sound, but a large difference on your wallet, and your chassis real-estate.
I hope not. I mean, there is much mentioned here about the supply being set up right. All considered, you can't just swap rectifiers and expect a fair result.
twice we set up a three way system in an audio show in a local downtown hotel, twice we attempted to use tube power amps, and twice we ended up using ss amps for the lows,
if you want "speed" go with a ss amp for the woofer...
if you want "speed" go with a ss amp for the woofer...
...or use a woofer/speaker better suited to the amp you were trying to use...
Hourses for courses really. But yes, pretty much all commercial speakers these days are designed to be run by low ouput impedance amplifiers which limits your amplifier choices but it also allows the speakers themselves to be made smaller.
I don't think a valve rectifier will have a special sound. But I believe the key is the different resistance of the valve, which will make a difference in the B+ voltage and will truly have an influence on the performance of an amplifier. Maybe this is the reason why different rectifying valves will have different sounds.
FWIW, "El Cheapo" uses an 'AL5 in the low current B- supply. It was a cost conscious, highly convenient, simple, choice for obtaining a slower starting rail. I definitely did not want 12AT7/ECC81 grids going positive, with respect to the corresponding cathodes.
I will not incorporate a "high" current rail that employs vacuum rectification in 1 of my designs. The 60 mA. 117Z6 setup for use in preamps is my limit and it's not exactly "mainstream". High PIV Schottky diodes are every bit as quiet as their vacuum counterparts and don't incur a substantial forward drop penalty. I have a 14Y4 that will (eventually) be part of a low current negative rail, as that's an "easy/peasy", inexpensive, way to slow rise down. My prejudices run towards avoiding SS things that might introduce digital noise into a setup.
If different specimens of the same tube rectifier type truly sound different, you can be certain that they exhibit different forward drops. There simply is no other explanation consistent with the Laws of Physics. Said natural laws don't change because somebody is "peddling snake oil".
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Your "speed" obviously requires copies amounts of LSD to make it happen. 😀
My own amplifier gives perfectly linear response down to 8Hz and literally apartment shaking bass,which your woofers obviously are incapable of.
The amplifier is a modified industrial valve unit.
You can't make generalisations about anything if you are doing it all wrong in the first place.
Don't worry those units already have large transformers (the ones on the 200W amps are by far and away the largest I have ever seen on any commercial amps), but I very much doubt your "112w triodes" would be a match for them, as they are AB2 class amps, and the guitar version of them knocks out over 50v on peaks into 16 ohms.
There's a very real difference between claims about stuff, and what it's able to deliver fully cranked for 30 mins...