Purpose of 2 or more rectifiers in an amp

[harryjmic]

Why would need 2 rectifiers in a amp, I would think once it went through one rectifier there would be no reason to have more then one. Thoughts?

[dankayaker]

To increase the weight !
Actually I have no idea but would like to know also.

[Roccaforte Amps]

Originally Posted by harryjmic

Why would need 2 rectifiers in a amp, I would think once it went through one rectifier there would be no reason to have more then one. Thoughts?

In some designs you have one rectifier in the high voltage supply,
and you have another in the bias supply.
Some amplifiers even have one in the heater supply.
These three are separate supply circuits.
You can't get DC without a rectifier.

So, in turn I guess you could call a 100watt plexi a dual rectifier.

[quinnamps]

Not sure if smoothing DC has anything to do with it. Rectifiers turn (rectify) AC into pulsing DC, then the filter caps smooth out the ripple. Multiple rectifier I would think wouldn't do anything besides be able to provide more current.
I think for instance in the dual rectifier the purpose is to be able to provide more current and keep thing tighter so that the amp can do hard metal type sounds and not get too loose and flubby.
Well that is my take on it anyway.
Other reasons might be a backup. If you use a solid state and tube rectifier it can be set up so that if the tube fails you can still get through the gig.
I am sure there are other design considerations and applications too but these are all I can think of.
For RS it seems the only reason to do it is to put another false patent under his belt.

[quinnamps]

HA! Doug you rock! Dual rectified indeed!

[Roccaforte Amps]

Originally Posted by quinnamps

Not sure if smoothing DC has anything to do with it. Rectifiers turn (rectify) AC into pulsing DC, then the filter caps smooth out the ripple. Multiple rectifier I would think wouldn't do anything besides be able to provide more current.
I think for instance in the dual rectifier the purpose is to be able to provide more current and keep thing tighter so that the amp can do hard metal type sounds and not get too loose and flubby.
Well that is my take on it anyway. (snip).

In our guitar amplifiers,
if you take a fullwave solid state rectified power supply and add another rectifer to the supply the only thing you're increasing is the power handling of the rectifier circuit, not tone, current, or voltage.
SS rectifiers are allready low impedance, and have a very little voltage drop. They can't supply anymore current or voltage then they're being supplied by the power transformer.

Rectifier tubes are a different story,they have a voltage drop across them due to their plate impedances. By adding another tube in parallel,
or even adding SS rectifiers in circuit to lower the impedance, you raise the supply voltage and current. Keep in mind that you're not boosting anything, you're just reducing the voltage/current loss due to tube rectification by adding another rectifier. note: (this transformer must be able to support the added tube's current draw.)

It's funny, I saw a schematic years ago by one of the first guys
to offer amp mod kits. He showed putting a rectifier in series with the preamp power supply. It was a fender twin rvrb, what you did was install the diode on the filter board by lifting one end of the 4.7K resistor, and putting between its end and the filter. Why? I wrote him several times,
but he never responded......

There's no reason to worry about rectifiers.
Worry about how the amp sounds,
we're talking about the speaker-to ear connections!

[John Phillips]

Originally Posted by harryjmic

Why would need 2 rectifiers in a amp, I would think once it went through one rectifier there would be no reason to have more then one. Thoughts?

If you mean two rectifier tubes, it's simply because one won't handle enough current - the tubes are in parallel, not series... exactly the same as running two pair of output tubes in parallel to produce higher power. It's nothing to do with running through more than one producing a 'smoother' DC supply - no rectifier can do that, that's the job of the filter caps and choke.

If you mean having more than one type (solid-state and tube) it's to give different tone/responses, of different amounts of headroom.

Mesa is a good example and has used all three types:

The Dual Rectifier model uses two rectifier tubes, because it's a 100W amp and a typical rectifier tube can only supply enough current for about 50W at normal tube plate voltages. (The Triple Rectifier uses three, because it's a 150W amp.)

The Dual and Triple Rectifiers also have switchable tube and solid-state rectifiers, as do several models with only a single rectifier tube (eg Maverick, Lone Star - but not the Single Rectifier, which has only solid-state).

The Blue Angel uses a tube rectifier for the power tubes, but solid-state for the preamp - this is to given the preamp more headroom and ensure that it stays clean while the power tubes distort.


Like Doug said, all fixed-bias amps have a separate rectifier for the bias supply too. AFAIK, they're all solid-state.

I can think of a possible reason to put an extra diode in series with the supply to the preamp - for the same reason as the Blue Angel; it will stop the charge stored in the preamp filter caps going back up the chain into the power stage if the power supply is stressed so heavily that the voltage on the power stage caps falls below that on the PI supply; this will keep the preamp cleaner and make sure that only power stage distortion occurs. I have no idea whether it's even possible to push a Twin Reverb hard enough for this to happen though...

[Roccaforte Amps]

Originally Posted by John Phillips

If you mean two rectifier tubes, it's simply because one won't handle enough current - the tubes are in parallel, not series... exactly the same as running two pair of output tubes in parallel to produce higher power. It's nothing to do with running through more than one producing a 'smoother' DC supply - no rectifier can do that, that's the job of the filter caps and choke.

If you mean having more than one type (solid-state and tube) it's to give different tone/responses, of different amounts of headroom.

Mesa is a good example and has used all three types:

The Dual Rectifier model uses two rectifier tubes, because it's a 100W amp and a typical rectifier tube can only supply enough current for about 50W at normal tube plate voltages. (The Triple Rectifier uses three, because it's a 150W amp.)

The Dual and Triple Rectifiers also have switchable tube and solid-state rectifiers, as do several models with only a single rectifier tube (eg Maverick, Lone Star - but not the Single Rectifier, which has only solid-state).

The Blue Angel uses a tube rectifier for the power tubes, but solid-state for the preamp - this is to given the preamp more headroom and ensure that it stays clean while the power tubes distort.


Like Doug said, all fixed-bias amps have a separate rectifier for the bias supply too. AFAIK, they're all solid-state.

My new Jenelle80/100 has 5 rectifer circuits.
Not sure what I'm supposed to call that??? LOL

[wichita]

What is a rectum fryer?

[John Phillips]

Originally Posted by Roccaforte Amps

My new Jenelle80/100 has 5 rectifer circuits.
Not sure what I'm supposed to call that??? LOL

A Quintuple Rectifier, of course! Get one (two?) up on Mesa and patent it before Randall Smith does .

[Roccaforte Amps]

Originally Posted by John Phillips

A Quintuple Rectifier, of course! Get one (two?) up on Mesa and patent it before Randall Smith does .

I'm sure he's already got that one.

[Crewchief]

Originally Posted by Roccaforte Amps

So, in turn I guess you could call a 100watt plexi a dual rectifier.

You bite your tongue and burn in hell for that blasphemy!!!!!

[nuno81291]

Originally Posted by Crewchief

You bite your tongue and burn in hell for that blasphemy!!!!!

+ 1

[Roccaforte Amps]

Originally Posted by Crewchief

You bite your tongue and burn in hell for that blasphemy!!!!!

but its twu

[harryjmic]

Thanks for the info guys, I thought it had a lot to do with higher power and was pretty sure that caps took care of the extra dc ripple but now we all know.

So if a tweed (low powered) twin uses 2 rectifiers and only puts out about 45 watts what is the purpose of the extra tube? I would think you would have adequate current capacity in the tube, so maybe it's a safety of some sort but if that is the case I would think they would have done that with the Bassman as well. The only thing I can think of is the Bassman went from the mercury type rectifier to the GZ34 so maybe this is the reason.