Solid state to tube rectifier?

[EWBrown]

First thing is to see if the "paper tube" (replacement) rectifier plugs into a socket (probably an octal socket). If this is the case, then check the wiring to see which socket pins are used (typically it is 2, 4, 6 and 8, 2 and 8 being filament, 4 and 6 being the anodes DC power is taken from pin 8. Some tubes use 1, 3, 5, 7 or another arrangement. Also, sometimes, unused tube socket pins are used as "tie points" so this can be confusing or decieving whe4n trying to "reverse-engineer" the circuit

Typical tube rectifiers would be 5U4, 5Y3 or 5AR4. Depends on the power output and B+ voltage.

should be a good start...

/ed B in NH

[erichayes]

Hi All,

To add to what Ed suggested, Dave, look to see if there are yellow leads going from the power transformer to pins 2 and 8, and red ones going to 4 and 6. If they are, and the amp uses 6V6s, 6BQ5s, 6AQ5s or some other low power output tubes, the rectifier is probably a 5Y3. If it uses 6L6s or a quartet of the above, either a 5U4 or (preferably) a 5AR4 could be used.

If the socket has either transformer leads or leads from one of the output (usually) tubes going to pins 2 and 7, the rectifier would be either a 6X5 or a 6AX5. In this case, the red transformer leads would go to pins 3 and 5.

If you have yellows going to 2 and 8, and reds going to 3 and 5, you need a 5Y4 or 5Z4, and your amp was designed by someone with a really peculiar sense of humor.

[dhuebert]

Please would someone explain why anyone would want a tube rectifier?

Let me explain: When I was prototyping the Hammertone Sixpac featured here, I built it with two switches, one to change from cathode bias to fixed bias and one to change from tube rectifier to solid state rectifier. With solid state and fixed bias the amp made 20 watts RMS @ 1KHz into 10 ohms. With solid state and cathode bias it made about 14 watts. With tube rectification and fixed bias it made about 11 watts and finally with tube rectification and cathode bias it made about 8 watts. I gave the prototype to the customer to play during a gig ( a tube amp on two pieces of 1x6 pine makes a striking image for the audience). I started him out with the 8 watt version and explained the function of the switches. By the end of the set he was playing the 20 watt version and absolutely pumped by the sound he was getting.

The conclusion: alot of power is wasted through the tube rectifier with no advantage gained in sound quality.

I did a little experiment to see how much power was being dissipated by the 5Y3, I measured B+ and the current at idle and again just at the start of clipping and worked the formula r=dV/dI and came up with 600 ohms of AC resistance. BTW, if someone has a better method I would like to hear it. After discussion with local gurus, I substituted a 150 ohm sag resistor in series with the UF4007s and built the amp that way. (just under 20 watts) To say the customer was happy would be a gross understatement.

Having said all that, please can we have a lively and informative discussion on the subject on tubes versus solid state rectifiers?

Don

PS tube rectifiers make even less sense to me for Hi-Fi applications.

[Blackburn Audio]

The main reason people use them (Tube Rectifiers) is because they like the compression effect they get when the amp is cranked up. They are less effecient and kind of a pain since it requires a filament tap from the power transformers and room to mount the tube but for some people this is a worthwhile trade off. You will get less power out because the B+ will be lower due to the voltage drop across the rectifier tube, but this lower voltage also lets the amp overdrive easier. Its not for everyone though, some prefer the tighter sound of the solid state rectifier and appreciate the higher power output. Personally I think its alot easier to just use a big wirewound resistor, as dhuebert said, to get the sagging effect. Just make sure you use a high enough wattage.


-Matt at Triodeelectronics.com

[erichayes]

Hi All,

Don, I couldn't agree with you more on the hi fi end of things. The whole idea of hi fi is to reproduce an original sound recording as faithfully as possible, and it just plain can't be done with tube rectifiers. Theoretically, it can't be done with solid state rectifiers either, since we're still changing AC into pulsating DC--albeit more efficiently--and then filtering out the pulsations as best we can. I've been tempted for years to get 46 12 volt 6 amp gel cells so I'd have a 600 volt source of pure DC (nitpickers, a "12 volt" lead-acid battery at ½ capacity charge will be at 13.2 VDC). As a designer and (don't quit yer day job) manufacturer of hi fi amplifiers, my paradigm is an absolutely transparent reproduction system, from signal source to speakers.

Phone's ringing, so I'll get back to the yin of this topic in a bit.

[erichayes]

Okay, the yang's been discussed, now for the yin--the creation of music electronically.

I used to be a musician, but my weapon of choice was a Mason and Hamlin Concert Grand piano. That pretty much recuses me from judging the foibles and idiosyncrasies of electric guitarists, et al, so all I can do is listen to their railings on likes and dislikes as far as sound is concerned.

As I've mentioned in other threads, I've worked with musicians who could give a rat's ass about how a tube works, or what torture it can be subjected to in order to get "That Sound, man". That's why I don't argue with a harp player, when he says "That Sound, man" occurs when we stuff a 5Y3 into his Bassman's rectifier socket, and a 6L6 and 6V6 into the output tube sockets. Or with a jazz guitarist who swears by his Princeton that's running with 1N4007s.

As Matt mentioned, there's a certain amount of compression that can be obtained from tube rectifiers, especially when they're undersized (5Y3 subbed for a 5AR4, f'rinstance) and pushed hard. God knows there are stomp boxes out there that can emulate this performance quantitively, and even give more range to the effect. But there are players who want the real deal, whether it's a Super Reverb's analog tank, a Fender Rhodes' eerie phase-shift tremolo, or the walking-on-crushed-glass sound of an old Marshall.

[WA4SWJ]

Eric,

That eerie phase shift tremolo from the Fender Rhodes electric piano you mention can be heard on Donald Fagen's latest fairly popular song "The H Gang" on his "Morph the Cat" album. Good album but that Fender Rhodes sounds awesome in that song. Of course there is some pretty cool guitar playing too!

Happy Holidays to all!

Regards,

[EWBrown]

The tube rectifiers give that slow turn-on warmup, and avoids the cathode stripping gremlins, and at least for a good sounding lead guitar, some sag can be a good thing, gives nice breakup and distortion, which of course, are a really bad thing for hi-fi audio :o

www.eurotubes.com have some good info re guitamps on their site.

/ed B in NH