Andy,
The step up from 1N4007 to UF4007 is substantial and well worth the cost differential. The 1N part is very noisy and (IMO) should not be used in HIFI equipment, either hollow or solid state. OTOH, the UF part is darned quiet on its own and it can snubbed into near silence.
Diminishing returns has set in in the case of the 5 A./1200 PIV Schottky. For supplies in that part's range, I suggest a "cockeyed bridge" that uses snubbed UF4007 stacks on the ends of the rectifier winding and a single Schottky on the CT.
Infineon makes 600 PIV/3 A. Schottkys that are reasonably priced. A 4 diode bridge from those parts is quite affordable and "noiseless".
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All,
Distinct warnings from Cree against stacking high PIV Schottky diodes are fairly well known. Stacking the parts seems to lead to cascading failures. Don't do it!
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Who said everything? I just said that sensitivity to rectifiers will vary with capacitance, according to the laws of physics. To the extent that you can hear the PSU, there is something wrong with the PSU and/or the amplifier. This is simply because the job of the PSU is to deliver DC at a low source impedance. If it does anything else it shouldn't!
I thought someone would mention this. It comes back to the purpose of driving. Is it to get safely and reliably from A to B? If so, a little road feel may help the driver be aware of poor surfaces so he can drive accordingly. If the driving itself is the purpose of driving, then lots of road feel may enhance the experience. However, this is then using the vehicle not as a mode of transport but as apparatus for an experience - an expensive, dangerous type of fairground ride? Motoring magazines and journalists seem to prefer the latter, and pour scorn on those who simply want to travel. Audio is not much different!
IME no amount of regulation seems to be able to hide the signature of a rectifier. Probably because regulators don't regulate so well in the MHz region. Passive filtering may be more successful but requires extreme attention and nice measurement equipment. Oversimplifications as seen in your post are just dandy for mid-fi but really out of place for more serious audio. The suggested stacking of Shottky diodes in order to achieve higher PIV is plain humorous.
It is fortunate then that most of us don't hear too well "in the MHz region"!
I realise that intermodulation allows us to 'hear' things which our ears can't detect. This emphasises the importance of individual amplifier stages being reasonably linear, as stray RF does not necessarily take the same path through the circuit as our intended audio signals.
I realise that intermodulation allows us to 'hear' things which our ears can't detect. This emphasises the importance of individual amplifier stages being reasonably linear, as stray RF does not necessarily take the same path through the circuit as our intended audio signals.
This is an interesting thread.
I'm not sure why no one mentioned ripple and which method is best used to reduce this from the power supply output. After all isn't that where the noise would be coming from, be it tube rectified or SS??
Two paths to the same goal here. Good clean harmonic free DC output.
Tube rectified power supplies use filter caps, resistors and a choke to eliminate/reduce ripple, where as solid state power supplies use filter caps, bridge rectifier (diodes), resistors and voltage regulators.
If you can hear anything from the power supply, wouldn't that be RIPPLE frequency in the form of 2nd, 3rd etc. order harmonics? As an example: if you had ripple in a TV power supply you could see it in the form of wavy picture..
So to summarize my thought here, since the goal is good clean DC output from an AC line, proper use and design of either SS or tubed PSU should both "sound" the same and that would be a transparent sound. If the listener can hear differences, wouldn't that be and indicator the design needs to be looked at further, be it SS OR tube designed?
I'm talking AUDIO here not guitar gear, I know that some guitar players like sag etc from the amp to give it a specific sound.
Cheers,
Bob
I'm not sure why no one mentioned ripple and which method is best used to reduce this from the power supply output. After all isn't that where the noise would be coming from, be it tube rectified or SS??
Two paths to the same goal here. Good clean harmonic free DC output.
Tube rectified power supplies use filter caps, resistors and a choke to eliminate/reduce ripple, where as solid state power supplies use filter caps, bridge rectifier (diodes), resistors and voltage regulators.
If you can hear anything from the power supply, wouldn't that be RIPPLE frequency in the form of 2nd, 3rd etc. order harmonics? As an example: if you had ripple in a TV power supply you could see it in the form of wavy picture..
So to summarize my thought here, since the goal is good clean DC output from an AC line, proper use and design of either SS or tubed PSU should both "sound" the same and that would be a transparent sound. If the listener can hear differences, wouldn't that be and indicator the design needs to be looked at further, be it SS OR tube designed?
I'm talking AUDIO here not guitar gear, I know that some guitar players like sag etc from the amp to give it a specific sound.
Cheers,
Bob
Ripple is not the whole story, although until that is right it is not worth getting too excited about second-order effects.
Rectifier switching can induce interference into adjacent circuits, especially when people wire their PSU as though it only handled DC. If the underneath of your amp looks very tidy, with straight wires and right angle corners, then it is likely to have huge loops sending and receiving interference. With normal SS rectifiers your PSU is handling RF (due to charge storage) so it should be wired like an RF circuit. This is less of a problem with better SS or valve rectifiers but there will still be fast transients.
Rectifier switching can induce interference into adjacent circuits, especially when people wire their PSU as though it only handled DC. If the underneath of your amp looks very tidy, with straight wires and right angle corners, then it is likely to have huge loops sending and receiving interference. With normal SS rectifiers your PSU is handling RF (due to charge storage) so it should be wired like an RF circuit. This is less of a problem with better SS or valve rectifiers but there will still be fast transients.
My 2 cents
A tube rectified supply will have higher impedance than a SS rectified supply, especially at bass frequencies. A tube rectifier can't be filtered with large capacitors to store energy for fast transients and as a result there will be coloration of the sound due to the voltage sag. If you doubt that you need to get out your scope and check the stability of your B+ when the power amp is asked reproduce loud passages with fast transients and heavy bass. Measure the B+ at rest and measure the B+ with the amp at full power. If your voltage is the same PLEASE POST YOUR DESIGN - I WILL USE IT!!!
If you don't wish to properly construct a SS rectified supply that won't induce noise into your amp (entirely possible if you follow proper design and construction practices) and you find the sound of a sagging B+ and the distortion and coloration that it induces (desirable in guitar amps but not hi-fi) preferable to a low impedance SS supply then use a tube rectifier for that "vintage, colored, loose bass" sound reminiscent of old tube amps.
A tube rectified supply will have higher impedance than a SS rectified supply, especially at bass frequencies. A tube rectifier can't be filtered with large capacitors to store energy for fast transients and as a result there will be coloration of the sound due to the voltage sag. If you doubt that you need to get out your scope and check the stability of your B+ when the power amp is asked reproduce loud passages with fast transients and heavy bass. Measure the B+ at rest and measure the B+ with the amp at full power. If your voltage is the same PLEASE POST YOUR DESIGN - I WILL USE IT!!!
If you don't wish to properly construct a SS rectified supply that won't induce noise into your amp (entirely possible if you follow proper design and construction practices) and you find the sound of a sagging B+ and the distortion and coloration that it induces (desirable in guitar amps but not hi-fi) preferable to a low impedance SS supply then use a tube rectifier for that "vintage, colored, loose bass" sound reminiscent of old tube amps.
I must assume that you are not including properly designed class A single-ended all-tube amplifiers in this statement.
This generalisation about tube and SS power supplies is just an outdated stereotype. No reason why a tube PS cannot be followed by active regulators - in fact i believe this to be an excellent approach. Nothing also prevents the use of chokes in SS supplies and there are good commercial examples for that as well. Ripple filtering is trivial and simple textbook engineering can guarantee good results. Talking of ripple harmonics, do you mean harmonics present in the incoming AC? Don't see how the type of rectifier would matter.
In order not to complicate the discussion with potential sag issues and class B PS harmonics is it not better to discuss preamp supplies? And not limit ourselves to stereotypes?
That seems to sum it up nicely!
When all is said and done, it's surely not about VT verses SS, but about suitability for purpose.
Why can't a tube rectified circuit be filtered with large capacitances? Some "magic" about SS I have not heard of?
There are current limitations with any rectifier, using a paralleled set of 5U4GB's should give a properly designed tube amp plenty of current and capacitance.
SAG is a term coming from the guitar amp world, we are talking about an amp with like 8 or 16 uF in the power supply, amps with 750uF, or more in the PS are regularly built for HiFi.
Yes i agree about not complicating this thread. Since you quoted me in your post, were you suggesting I was stereotyping in MY post?
There are good designs that use both types of rectification. I've got preamps/amps that sound great with both. My favorite sounding unit has 5R4GY rectifiers, 2nd is a stock PAS2 preamp (which shouldn't sound as good as it does). I've got some BIG speakers (read big woofers dip to 28 Hz), and I don't experience any sag. Probably because I would need to turn the amp up pretty loud before I would experience sag in the low frequency range. Sag is another issue altogether. I'm sure it's been talked about here and elsewhere many times. I know it comes from the PS rectifier running out of gas, but not all tube rectifiers exhibit that trait at normal or even moderate listening level. Again, it goes back to design IMHO.
Cheers,
Bob
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