# Solid State Rectifiers in Tube Amps ??



## JohnyO (May 31, 2009)

I was looking at tube amps on the Guitar Center website last night, and notice that a lot of the cheaper tube amps from Fender and other builders have solid state rectifiers. I have a couple of questions. What does the rectifier do, and does a solid state rectifier take away from the tube sound or does it not matter.

Thanks


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## Gene Machine (Sep 22, 2007)

*it depends*

forgive the long winded answer, but hey, you asked....

The rectifier is the device that helps convert AC power to DC power.

step 1) is turn a +/- signal from AC sine wave into a +/+ signal (think of camel humps). Then step 2) a big-ass capacitor filters out the huge ripple and turns it into DC.

A tube rectifier only allows current to flow one way. it heats up the cathode until electrons are ready to jump off. But they only jump one way, thus controlling the polarity of the output.

In solid state, the same thing is achieved with a diode, a special material made out of electrically inert material (called substrate) embedded with material that conducts. Thus the name semi-conductor. it is designed to let current flow one direction. 


So what! right? Well the end result is a tube rectifier "sags" a bit when you play it hard, because the current that is drawn by the amplifier tubes and the speaker decrease the amount that the rectifier can produce to the rest of the amp. this sag adds to the dynamics of a tube amp. But, tube rectifiers don't last forever, and need to be changed.

diode solid state rectifiers don't have any noticeable sag. This is not necessarily a bad thing depending on the dynamics your looking for. plus they will likely last forever. 

I personally don't have any issue with diodes. love em. the signal path does not go through them, they are only used to provide clean DC to the tubes.

How does this affect you? Go try some and see what you like. my guess is you wouldn't be able to tell either way. Except when you have extra $$ in your pocket from not having to change your tube rectifier...

G.


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## vds5000 (Apr 14, 2008)

There's a difference in tone, but it's not that big of a deal. When I had my Mesa Lonestar, I had the switch set to SS Rectification. When I had my BadCat, same thing - I had it switched to SS.

A SS rectifier won't 'take away' from a tube amp's tone. A good tube amp will sound like a good tube amp regardless of the rectifier. My BadCat sounded phenomenal with the recitifer switched to SS. The Lonestar sounded great too.


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## parkhead (Aug 14, 2009)

that was mostly Right... like 98% 

for some people it is almost impossible to tell the difference, but in fact if you are a blues player or a Metal player you will spot it right away. 

The Metal player will say the Tube rectified amp is slow and does not track his palm muting 

The blues player will say the SS diodes are too fast and don't allow the amp to bloom properly...

In other words the solid state rectifed amp reacts faster and has a different low end response...

Once again in 80% of situations most players cannot tell the difference 

a good designer can make a solid state rectified amp sound like the tube rectifier but can't pull the current from tube for a "metal amp" 

even a blues player might prefer a solid state rectifier on a big stage with a loud drummer, hence those switches on higher end amps 

p


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## zontar (Oct 25, 2007)

Hey, BB King & Albert King spent a lot of time playing all solid state amps--and they sounded great.

A sold state rectifier is fine, in my books, but then I own & use a Roland JC-60.


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## jcayer (Mar 25, 2007)

Welcome to _subjectivism land_... kkjuw


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## Wild Bill (May 3, 2006)

vds5000 said:


> There's a difference in tone, but it's not that big of a deal. When I had my Mesa Lonestar, I had the switch set to SS Rectification. When I had my BadCat, same thing - I had it switched to SS.
> 
> A SS rectifier won't 'take away' from a tube amp's tone. A good tube amp will sound like a good tube amp regardless of the rectifier. My BadCat sounded phenomenal with the recitifer switched to SS. The Lonestar sounded great too.


You have to crank an amp to really notice the differences between a tube and a solid state rectifier. The 'sag' of a tube rectifier is caused by a voltage drop. A tube rectifier will lose some 10's of volts just by doing its rectifying job. However, as you crank the amp and draw more power that voltage drop will increase a lot more.

This means that as the amp really gets honkin' it will have a lower plate voltage to the output tubes. This has the effect of 'sag', or compression on the signal. It lowers the peaks of the signal, or the dynamic range. It can sound like it's smoothing out or 'fighting' fast volume changes, like with fast and strong picking.

So as Mr. Parkhead pointed out, for blues there's nothing like the vintage sound of a tube rectifier but for metal, particularly fast leads, most would prefer solid state rectifiers.

Solid state rectifiers have a 'mice nuts' voltage drop that doesn't change from low to high volumes.

Amps mostly changed to solid state rectifiers in the early 60's for just one reason - they're much cheaper! No tube, no socket, no extra space to mount them...those parts cost dollars and SS diodes cost pennies.

Solid state rectifiers will also handle much larger values of filter caps without blowing, which means an even tighter sound.

Different tube rectifiers have different voltage drops from low to high power levels. The 5AR4 has the least, which makes it 'tight' enough to sound very much like a solid state rectifier. The 5U4 has MUCH more sag, if that's what you like!

One thing to be careful with is that there have been a lot of solid state replacements for tube rectifiers over the years that will just plug into the tube socket. Only the Weber 'Copper Cap' is absolutely safe when doing this. The reason is that voltage drop. If you have an amp designed to have a certain plate voltage with a tube rectifier and then you use one of those SS replacements with no voltage drop then you can end up with that plate voltage rising by 20-40 volts or more. Considering that guitar tube amps tended to have plate voltages high and pushing the envelope to get more power it may then be too high for the voltage ratings of the filter caps. At the very least, the voltage should be checked afterwards and most important, the bias should be re-adjusted.

The Copper Cap has a built-in voltage drop to look the same as a tube rectifier.

Just .02:smile:

:food-smiley-004:


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## Wild Bill (May 3, 2006)

zontar said:


> Hey, BB King & Albert King spent a lot of time playing all solid state amps--and they sounded great.
> 
> A sold state rectifier is fine, in my books, but then I own & use a Roland JC-60.


Of course! Those guys had an ultra clean tone!

Transistors have always been great for low distortion applications. They just tend to sound harsh and fuzzy when they are asked to distort. Most folks prefer the warm thickness of tube amp distortion.

You CAN get some good distortion sounds from transistors but it's not easy and has taken a lot of skull sweat for designers over the years. While they may be good distortion sounds they can never sound exactly like a good tube amp, just 'sorta close'. For some guys that's enough. Me, I wanna hear humbuckers plugged straight into a 50 watt vintage Marshall tube head, with British sounding speakers! Kick in the bridge pickup and dig hard into thick strings right on top of the pickup!

I've never heard a solid state amp make that gorgeous snarl!:bow:

:food-smiley-004:


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## nonreverb (Sep 19, 2006)

Ah, the great debate. Let's start with a little history shall we? The tube rectifier is a throwback to a time when there were no solid state diodes. It was the only way to rectify AC voltage. Fast forward a few years and the advent of silicon diodes. The first "guitar" amps to get them were the high power ones. Interestingly , high power amps really start when silicon diodes become available.(ie the 80 watt Tweed Twin). This was due to the fact that the available tube rectifiers cannot handle high wattage applications. The ones that could were too expensive and required costly circuit designes. Silicon diodes where a cheap and reliable way to solve the problem.
The three main types used today are the 5U4, 5AR4(GZ34) and 5Y3. The 5AR4 is probably the most desirable today as it has less sag and lower voltage drop across it. The 5U4 is the one most associated with tube sag. It has a slower reactance and a larger voltage drop across it. The 5Y3 is used in low power amps.
What tube rectifiers really do is drop significant voltage across them. Ever hear a tube rectified amp with a solid state rectifier in it? That's an audible difference. 
Yes, there are those that swear by them and in some limited cases, tube sag is present but really it's dependent on the tube type and the amp design. I seriously doubt that a Deluxe Reverb has much tube sag...it's only 22 watts!
Honestly, I don't think many people could tell tube sag if they heard it. Much of the "mystique is what people have been told.
However, it's a personal thing and the lower voltage and sag condition that tube rectifiers bring are part of the classic sound we're all looking for.


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## keeperofthegood (Apr 30, 2008)

9kkhhd amazingly, everyone here has missed on the "other white meat" of rectifier history: Metal Rectifiers. Some people seem to think they are the cat's meow! I do not know if they were used in guitar amps or not, I do think there is an audiophile market that likes them as I have seen some rather insane pricing on these. MOST people are of the opinion that these should be replaced on-sight with silicon. They age poor, and the Selenium ones are toxic when they poof (not to mention really stinky). They are usually hollow, so with some artistry you can slide a 1N400X inside them, and make them "look like" they are in use (a bit of crazy glue is needed) and for looks I love them, they are very "Jetsons" looking http://en.wikipedia.org/wiki/The_Jetsons

Selenium and Copper Oxide rectifiers came before and during the days of tube rectifiers, and like the Cat's Whisker are solid state devices long before Silicon became the well known "solid state".

http://en.wikipedia.org/wiki/Metal_rectifier

AS to the OP on this, I was reading a really interesting site the other week, worth the read I think:

http://www.freewebs.co.uk/valvewizard/fullwave.html
http://www.freewebs.co.uk/valvewizard/bridge.html

The use of mixed silicon and tube to achieve both power and sag is an interesting mix. It is also interesting that tubes can be paralleled easy-peasy, and put in series with silicon, and silicon can be put in series or parallel too without much trouble at all, but there is very very little information on putting tubes in series. I only found one forum discussion on using tube diodes for cathode bypass and another article that said the method of bypass chosen on the cathode result's in no measurable change in function of the tube in circuit.


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## ThePass (Aug 10, 2007)

I'm not sure if my ears are that sensitive to hear the minute diff in SS and tube rectifers....different pickups, woods, tubes (EL's vs. 6L6 say) sure....but they are the obvious ones.


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## keeperofthegood (Apr 30, 2008)

ThePass said:


> I'm not sure if my ears are that sensitive to hear the minute diff in SS and tube rectifers....different pickups, woods, tubes (EL's vs. 6L6 say) sure....but they are the obvious ones.


See, this is where I would plan with a hybrid as I posted. The SS would handle anything in an amp, their PIV start at 400 volts and go up fast for no cost increase. So, switch in a good high loss tube that sags easy and you got effect without compromising function. That should open the door up to using a wider variety than the standard few tubes used as diodes.


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## vds5000 (Apr 14, 2008)

nonreverb said:


> ... Much of the "mystique is what people have been told....


This statement alone is something many folks should consider when discussing most of the obscenely high-priced gear out there - and I'm specifically talking about $5digit+ vintage pieces ... but that's another thread.


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## Wild Bill (May 3, 2006)

keeperofthegood said:


> See, this is where I would plan with a hybrid as I posted. The SS would handle anything in an amp, their PIV start at 400 volts and go up fast for no cost increase. So, switch in a good high loss tube that sags easy and you got effect without compromising function. That should open the door up to using a wider variety than the standard few tubes used as diodes.


Mesa beat you to it years ago with the Dual Rectifier!:smile:

:food-smiley-004:


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## mhammer (Nov 30, 2007)

From time to time, I'll switch some of the more critical components in my little tweed Princeton, just to see if it makes a difference. It normally uses a 6V6 tube, and I've swapped it out for a 6L6 on occasion. I've also swapped out the 5Y3 for a SS rectifier that I bought from Hy Bloom, our local legend here in Ottawa. The SS rectifier does give a little more kick to the sound, but it's not something I leave in all the time. I generally switch back to the 5Y3.


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## JohnyO (May 31, 2009)

Wow, thanks for the replies guys. Look like I'm entering into a whole new world. It's all very interesting and I will definitely need to do more reading about all this stuff. My problem is I start getting into all of the this stuff and it takes away from practice time, and I need all of the practice I can get.


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## greco (Jul 15, 2007)

JohnyO said:


> ......My problem is I start getting into all of the this stuff and it takes away from practice time........


^^^^^^^^^^^^^^^^^^^^^^^
This should be the motto of the forum. 

At least you can gain some comfort in that you are not alone with this problem...in fact, you are in excellent company.

Cheers

Dave


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## ThePass (Aug 10, 2007)

keeperofthegood said:


> See, this is where I would plan with a hybrid as I posted. The SS would handle anything in an amp, their PIV start at 400 volts and go up fast for no cost increase. So, switch in a good high loss tube that sags easy and you got effect without compromising function. That should open the door up to using a wider variety than the standard few tubes used as diodes.


I used to play thru an old Marshall 3203 Hybrid head ~ it rocked....wish (like old my old gear) I still had it.


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## zontar (Oct 25, 2007)

Wild Bill said:


> Of course! Those guys had an ultra clean tone!
> 
> Transistors have always been great for low distortion applications. They just tend to sound harsh and fuzzy when they are asked to distort. Most folks prefer the warm thickness of tube amp distortion.
> 
> ...


Well, as pointed out already--it is subjective.

I like solid state and I like tube, and I like the mix of the two.
The best sounding amp I ever played was a legend--one of the first hybrids--and the tone on those is perfect for me.

But I'll stick with my mostly solid state amps--I do have a Garnet stencil bass amp, with tubes--and it works for guitar.

But these days I mostly play blues or clean chords strumming--so a Roland does nicely.

A solid state rectifier is no big deal.


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