Solid State Rectifier in Tube Amp?

[baconmpanada]

I looked into this ad:

http://www.vintageguitars.org.uk/fender72p54.php

but it says solid state rectifier, what does it really mean?

[okcrum]

It means the main power supply rectifier is not a tube. That means the plate voltage on the output tubes will be stiffer (less variable).

[baconmpanada]

Originally Posted by okcrum

It means the main power supply rectifier is not a tube. That means the plate voltage on the output tubes will be stiffer (less variable).

does it mean that the bass signal is still processed by tubes? This is still a tube amp in the truest sense correct?

[fu22ba55]

Originally Posted by baconmpanada

does it mean that the bass signal is still processed by tubes? This is still a tube amp in the truest sense correct?

It's a tube amp all right.

The pro techs will chime in here shortly, but most tube amps are solid-state rectified. I know for a fact some Sunn 2000S's were tube rectified, and some were SS rectified. (Still with power tubes in the output stage.) The SS rectified ones are a bit louder.

It's not a hybird like you see today. (tube pre, SS power amp). It has a tube power amp.

Many tube amps used tube rectifiers in the 60's... so they mentioned the SS rectifier in the '72 catalog since that was a big deal at that time.

I imagine most "all-tube" amps these days still have SS rectifiers.

(Someone please correct me if I'm wrong. I often am.)

[jimbilly]

As I understand it, the 'rectifier' converts AC to DC, and a tube rectifier supplies DC with a little softer edge to your tone. SS rectifiers are more common in tube amps designed after, oh, '65 or so. Yes, it's still a real all tube amp with a SS rectifier.

[mongo2]

Originally Posted by jimbilly

As I understand it, the 'rectifier' converts AC to DC, and a tube rectifier supplies DC with a little softer edge to your tone. SS rectifiers are more common in tube amps designed after, oh, '65 or so. Yes, it's still a real all tube amp with a SS rectifier.

The rectifier only converts the negative half of the AC sine wave to positive. It's then filtered heavily with capacitors to convert it to DC with some ripple.

IIRC, tube rectifiers are known to "sag" (lower voltage) under heavier loads which then effects the B+ voltage (which is connected to the plates of all the tubes in the audio path) and changing the amp's response. The power required to reproduce low frequencies can cause it to happen easier, especially for bass. Solid state rectifiers don't generally sag, but there are some that are modified to mimic the sag characteristic of tube rectifiers.

[okcrum]

Originally Posted by fu22ba55

It's a tube amp all right.

The pro techs will chime in here shortly, but most tube amps are solid-state rectified. I know for a fact some Sunn 2000S's were tube rectified, and some were SS rectified. (Still with power tubes in the output stage.) The SS rectified ones are a bit louder.

It's not a hybird like you see today. (tube pre, SS power amp). It has a tube power amp.

Many tube amps used tube rectifiers in the 60's... so they mentioned the SS rectifier in the '72 catalog since that was a big deal at that time.

I imagine most "all-tube" amps these days still have SS rectifiers.

(Someone please correct me if I'm wrong. I often am.)

I thought they already had.

The SS rectifier was a selling point because, as you say, they were a bit louder. The plate voltage was a bit higher than with tube rectifiers if you used the same power transformer, typically 30-50 volts higher.

Some dual or triple rectifier (mostly guitar) amps these days still use both types, as the sound changes a bit from the tube rectifier voltage drop & sag with load current.

The short of it for the OP is, yes, it's a tube amp.

[thumpbass1]

Actually having diodes do the work of the rectifier stage, instead of a tube can be a good thing for us bass players. A lot of the top tube tone, cork sniffers, say that solid state rectifiers can tighten up the bottom end and deliver a little bit quicker response in terms of capacitor recovery, etc, etc, aka the sag effect, that may or not be a good thing depending on the personal tone tastes of the individual musician. It's usually guitar players that like the effect of sag, while others don't care one way or the other. SS rectifiers been around for decades now, and used in many great tube guitar and bass amps. These days it's more of a matter of what amp designers choose to do for tone tweaking when they put a tube rectifier stage in an amp as okrum and others have pointed out in the above posts.

[billfitzmaurice]

Originally Posted by thumpbass1

Actually having diodes do the work of the rectifier stage, instead of a tube can be a good thing for us bass players. A lot of the top tube tone, cork sniffers, say that solid state rectifiers can tighten up the bottom end and deliver a little bit quicker response in terms of capacitor recovery, aka the sag effect, that may or not be a good thing depending on the personal tone tastes of the individual musician. It's usually guitar players that like the effect of sag, while others don't care one way or the other. SS rectifiers been around for decades now, and used in many great tube guitar and bass amps.

That sums it pretty well. Fender switched to SS diodes in the mid 60s because they were at that time half the cost of 5Y3GT rectifier tubes; today they're 1/100th.

[KramerBassFan]

Originally Posted by billfitzmaurice

That sums it pretty well. Fender switched to SS diodes in the mid 60s because they were at that time half the cost of 5Y3GT rectifier tubes; today they're 1/100th.

Not to mention they require much less support structure, last longer, and don't really "sag" like a tube does.

There aren't really any bass amps over 100w that have tube rectifiers, and i can't think of very many Currently built tube ones that have them, unless its a copy of our old Flip Top friend...

[okcrum]

Originally Posted by billfitzmaurice

That sums it pretty well. Fender switched to SS diodes in the mid 60s because they were at that time half the cost of 5Y3GT rectifier tubes; today they're 1/100th.

Plus, by the mid 1960s we could actually mass produce reliable SS rectifiers with the required working voltage.