solid state rectification VS tube rectification design opps.

Been playing around DIYing guitars amps with my buddy. Anyway been tinkering with tube and solid state rectifers and have noticed that I prefer the sound of the solid state more in our configuration. been switching between solid state rectification and a rectifier tube. The rectifier tube in the equation at the moment is a 5y3 and the output tube in the equation is a 6v6. So this is more of a design talk on tubes vs solid state rectifiers. I like the sound of solid state rectifiers in the amp we are diying. Not an end all be all cause we thinking of including a rectifier tube if we were to ever sell them that way people could switch them if they wanted to. so guys sonicly which do you prefer? I noticed the solid state had a tighter sound to it VS the tube which seemed to be a lil sloppy. mainly in the lower end. opinions?

Solid state in a single V6 is cool because you extract a bit more power via the higher voltage due to less foward drop in the 5y3.

I depends on the style of music, some rustic types might like the sag and compression of the 5y3, where-as the crunch monster rivet heads will demand the quicker attack envelope of the 1N4007's.

You can make an octal plug with solid stae inside to plug into the 5y3 socket. These have been around for years now. Just make sure your filter caps can handle the extra 20 or so volts in dc increase.

Because a single ended amp (or any true class-A amp) has constant current draw, the sag effect provided by large drop rectifier tubes like the 5Y3 doesn't happen, there's just a constant voltage drop.

Thus, I haven't found that a tube rect adds any sonic character to a single ended amp, but the 5Y3 is a handy solution if you want to drop the B+ 20V - 50V.

Jon

I haven't really come across a tube rectifier that I've liked yet, but I also haven't been very methodical about it either. Sloppy is a good description. A tube rectifier is a good marketing gimmick though, with buzz words like "bluesy sag", "all tube", "vintage design", "class A rectification" (OK, maybe that last one is pushing it a little....) :wink:

Is this something that you might bring to market? I like the idea of swapable tube/silicon. That way uninitiated players that think they should like a tube rectifier better can still be happy with the sound when they turn the little switch back to "solid-state". Sell them on the idea of a tube rectifier, keep them on the reality of a silicon one. And maybe you shouldn't label it "solid-state". Instead label it "plexi-style rectification" :wink:

-Chris

Interesting point Vibrolax, I just learned something :thumb:

Single ended - constant current draw? Not the way I play. I ain't that old yet.
Maybe in a home stereo with 300B's but guitar amp? No way.
You can hear the difference between solid and glass, might be subtle, but it's there.

If you want to have both solid state and tube rectifier, just put in solid state and use a series power resitor to emulate the 5y3 sag. That way you don't have to light any heaters.

The Mullard GZ 34 is a nice sounding rectifier.

That thing about constant current draw is a common misconception; I think it arose from a misunderstanding of the fact that a class-A amplifier s at max dissipation at ZERO signal. Anyway, measure the plate current of your amp while cranking guitar through it and you'll see for yourself. The current actually drops as the output tube grid swings negative and the tube is driven closer to cutoff.

PRR had a nice discussion of the various ways of class A a while back---I don't know what the thread was offhand.

The essence of class A is that the active device(s) never has its (their) current(s) go to zero through the entire trajectory of the signal swing. It says nothing more as to what the details of that trajectory are.

A single N-type active device with a single-supply current source (limiter) load, from the positive rail, will perforce have constant power supply loading. Complementary devices in sandland can be set up so that neither turns off completely at either extreme of signal swing, but their power input terminal currents can change a bunch.

If our objective is to minimize power supply load current fluctuations, there are ways to do this. If instead we are more interested in constant active device dissipation there are other means to that end. Both are versions (albeit unusual ones) of class A.

> A single N-type active device with a single-supply current source (limiter) load, from the positive rail, will perforce have constant power supply loading.

Well, yeah, but... who does that? (Except a few hi-fi nuts.)

A one-6V6 gitar amp will have a choke (transformer) load. Over a single audio cycle, current is conserved. But over the duration of a gitar note, current can change about as much as it wants to.

In very-linear use, power output far below clipping, no stupid/clever tricks, the 6V6/choke current will be constant.

Just below clipping (large current swing), and without feedback (gitar amps often minimize or omit NFB) the current will rise due to plate rectification. The 6V6 is not dead linear, the up swings are bigger than the down swings.

Just above clipping, THD is still not over 5%-10% so this may be the "book condition". However the grid is peeking over grid-current threshold, rectifying, and (assuming R-C input coupling) knocking itself negative. Plate current falls. This could be where a one-6V6 shows "sustain" (it is acting as a not-very-very-dirty Limiter) so it may be routine gitar tone.

Up to "gross" distortion, the current variations are like 5%-10%, so supply "sag" resistance has only a small effect. IMHO the glass rectifier fad is more about push-pull amps which have 20%-100% current variation from small to large output, not the one-6V6 and kin.

With adequate NFB, current is (nearly) constant up to clipping, not even those 5%-10% shifts.

Far into gross distortion, current is dropping because we have exceeded the tube's current passing ability. Output level will not rise just because the plate voltage rises. It may rise because G2 voltage rises which increases the tube's current limit. But it would have to rise a lot to have any audible effect. Such effect is probably opposite to what we want (though who knows?). And since we often need R-C decoupling of G2 to control buzz, there is a time constant that may fight the music.

I think hollow rectifiers are an obsolete abomination. I think the last time I left one in an amp, it was a series-string radio converted to an amp and I needed the rectifier drop.... no, in fact I remember wiring-up a mess of 2W 47Ω resistors to bypass the rectifier heater and feed the 50C5 and 12AV5 heaters. I hate hollow rectifiers. I think they are bad. They are an utter waste of heat. I know they fail more than most tubes. I think rectifier design was a hasty afterthought: most tube rectifiers are pretty bad performers compared to other late-1950s tubes. I think any "good" they can do is mostly imaginary, and anyway you can probably get the same effect some better way.

I tend to agree it (hollow-state rectification) is something of an abberation---but sometimes I think some bottleheads must get into altered states and practically climb right down into the innards of their equipment, there to be revolted by anything not echt-hollow :green: After I think these thngs I usually realize it's time to have a lie-down.

Years ago Bascom King reviewed a Jadis big class A tube power amp for the Abso!ute Sound, and opined that although he didn't know why, somehow tube-rectified power supplies in power amps such as the one under review sounded better. This particular review was unusual for that mag because it actually dared to describe some measurements...

I tried to strike up a conversation with him about this when he was manning the Infinity room at CES, but he was in no mood, mostly due to a splitting headache from the exposure to high levels of audio for hours. Or, it could have been me.

At a related issue, the re-issue LA2A compressor has the original, nice-lightening neon bulb stabilizer inside - unconnected to all but the powersullpy - but hidden under a piece of heatshrink is the Zener that actually does the voltage stabilizing service for the meter.. :razz:

Jakob E.

it's the high output impedance that 'makes' the sound (if we're not talking guitar amps), i think. i like to use valve rectifiers for some projects. they work really well with SE stuff. i don't like high speed diodes, they create more junk than good, schottkys likewise

i reuse lotsa old powertransformers and they're usually made for valve recitifers anyway. it's true that a lot of old ones fail

A single 6V6 "Champ" style circuit tends to magnify small sonic nuances more than some of your other amps. Maybe it's because the power is so low, 3 to 5 watts, that you can actually hear after five minutes of playing it. Everything from the player, to the guitar, to the amp to the speakers is all part of a system. Small changes in the amplifier can sometimes bring all these ingredients together.

You can tailor the power supply to the amplifier - take a Fender Twin Reverb vs a Fender Super Reverb. The Twin has solid state rectifiers. The Super has a 5U5GT. The Twin has 2 - 12 inch spks, the Super 4 - 10's. The Twin speaker cabinet will not be as boomy as the Super. Solid state rectifiers will tighten up the bass. Just what you need to bring it up to the Super. The Super needs bass reduction due to the speaker cabinet. The 5U4 is perfect for this. It will take away some of the bottom end punch.

So the best thing to do is tweak whatever you have to suit your playing style. It does not take long to change stuff in an amp that has about 12 components. Or you could just copy the classic 5F1 Champ circuit which has the better of the feedback loops and stick a 5V4 rectifier in there, which will give you something in between solid and tube rectifier sound.

[quote author="CJ"]
You can make an octal plug with solid stae inside to plug into the 5y3 socket. [/quote]

Already ahead of you there. WE first played with a fender solid state plug which was enclosed in goop and plastic. reversed engineered already. But really didn't need to it's only a few diodes. Thinking to either put a switch in the front to switch between the 2 or just include a 5y3 and allow for switching buy removing the solid state. :twisted:
The circuit is based off of a nice supro combo amp we got to play with. thanks peter :thumb: Anyway

[quote author="Emperor-TK"]Is this something that you might bring to market?
-Chris[/quote]
Well maybe? it's a cool idea but still need tweeking. maybe a marketable item but gotta finish and diy a good looking proto type. Dammit we too busy just playing around with the ugly prototype we got that fook it's taking us for ever.

A tweak that might give you more of a difference would be to build a neg bias supply for the output tube and switch between self bias and fixed bias.

This might be heard more than the subtle tube vs solid rectifier. Give it a try. Just put in a reverse diode on one of the B+ red sec wires with appropriate dropping resistors and filters and connect it to the grid ala Twin Reverb style.

There can be quite a bit of neg feedback with an un bypassed cathode resistor on the V6.

Don't forget to consider what happens to a power transformer when all of a sudden you take a load off of it by disconnecting the anticipated 5 volt 2 amp 5Y3 heater. Less core saturation and heat. Might change the waveform going into the rectifiers (big deal) or it might not heat up the chassis and output transformer to the tempeture you like after an amp gets played for an hour. But now we are really getting into the audiophool zone, but if your really into this stuff......

[quote author="bcarso"]Years ago Bascom King reviewed a Jadis big class A tube power amp for the Abso!ute Sound, and opined that although he didn't know why, somehow tube-rectified power supplies in power amps such as the one under review sounded better. This particular review was unusual for that mag because it actually dared to describe some measurements...[/quote]

Well, for one thing, tube rectifiers generate a lot less RFI crud to radiate through the amplifier, and the ripple contains a lot fewer high harmonics to leak out.

As for single-ended class-A being constant-current...naah. Put a current probe into one and look. What's more-or-less constant current is a push-pull class-A tube circuit.

Peace,
Paul

[quote author="pstamler"][quote author="bcarso"]Years ago Bascom King reviewed a Jadis big class A tube power amp for the Abso!ute Sound, and opined that although he didn't know why, somehow tube-rectified power supplies in power amps such as the one under review sounded better. This particular review was unusual for that mag because it actually dared to describe some measurements...[/quote]

Well, for one thing, tube rectifiers generate a lot less RFI crud to radiate through the amplifier, and the ripple contains a lot fewer high harmonics to leak out.
...snip...


Peace,
Paul[/quote]

Another thing is that the sand state rectifiers allow really big current pulses to flow on the a.c. peaks, compared to hollow state. These have a tendency to saturate the transformer cores, which then radiate even if they are toroids. A series resistor will tame this at the cost of efficiency, or you can just make sure all pickup loops in the circuit (and surrounding equipment!) are small. Sometimes that is tough.

When silicon diodes are bypassed with reverse recovery spike snubbers the energy involved can be tamed to some extent. But at the same time the snubber allows more coupling of other line noise across the diode---and the diodes aren't usually very low C to begin with. All of this can be accomodated but it gets complex.

I couldn't find any interelectrode capacitances tabulated for the 5U4 etc. but they are probably pretty small, certainly compared to a solid state diode of comparable current capability.