converting to all tube

[JimmyM]

Yes, the SVT has always had a SS rectifier. And thanks for the claramicashun about the voltage vs wattage, Edwin. I still stand by my premise that a tube rec for an SVT would be very large and impractical, though, otherwise someone else would have done it if not Ampeg. Now the B-15...tube rec all the way for that one! Flirted with the idea of a SS rec on it, but nah.

 

[edbass]

I'm sorry for getting away from the original post. And once again, the nobody ever wins "tube vs ss" debate. YAWN!

Many new production all tube amps have solid state rectifiers instead of tube rectifiers. Thus, cancelling the claim to be an all tube amp. My Mesa 400+ had a solid state rectifier. (I'm gonna say it loud and proud. I hated that amp! Thank God I sold it!)

Please don't ask me why newer all tube amps don't have a tube rectifier. I don't even know what a rectifier is. But beware, if one buys an all tube amp because they want that all tube sound, a solid state rectifier might be in the amp making it a non-all tube amp.

Purist insist on a tube rectifier!

I would be inclined to buy a vintage all tube bass amp instead of a new one for that reason.

Buyer beware! Many vintage tube bass amps will need to be "gone over" by a qualified amp tech. Those old oil filled capacitors leak after about 20 years and need to be replaced. The amp will have to be "spec out" to make sure it's up to par to original standards.

Resistors, transformers, tube sockets all need to be check out.

Yes...........the joys of tube amp ownership! But when they are running right, it's a beautiful thing.

Most vintage tube amps have only bass, mid and treble reduction only. No boost! Well, usually there's a bass boast switch (mud) and a treble boost switch. Some of those vintage amps only have bass and treble cut controls. So, if your wanting that so called, Hi Fi sound, you'll need a bass with active eq preamp. Using a passive bass will be limited with tweaked sound.

I'm not saying ss is better or tubes are better. That's up to the bassist! I do get soooo tired of TB Preachers saying that tubes are better.

Whatever!

As has been pointed out, rectifiers aren't in the signal path; the signal coming from your bass/guitar never passes through the rectifier on its way to your speakers and ultimately to your ears.
Its part of the wall plug AC delivery circuit that powers the amplifier stages, kind of like the PT, the AC cord or the fuse is.

However tube rectifiers and SS rectifiers can effect the tone by the way they deliver the power to the circuit.

Tube rectifiers can under deliver current in high draw situations causing a reduced headroom effect often called "browning"; similar to the effect that a Variac can cause when you intentionally starve the circuit of current.
A mild thickening distortion generally associated with guitar players rather than bass players, often credited to Edward VanHalen's Variac induced "brown sound".
Not horrible sounding on bass, but generally bass players are searching for more rather than less headroom.

I have several bass amps with tube rectifiers, several with SS diodes, and some that I've switched to SS from tube rectification.
As I said before. I generally like "clean", and rarely push my amps to a level that would cause the vacuum tube rectifiers to noticeably "brown" the amps, but even at low levels a SS rectifier has a "stiffer" response; stronger, tighter bass, and to my ears are overall more dynamic than the tube recs.

One plus for the tube rectifier (IMO) is that when you hit the "on" switch they ramp up the power gradually as they attain operating temperature as opposed to the SS diodes, which blast the circuit (filter caps) with full power the instant you hit the switch.


I don't think the tube types actually say they are "better" as much as they say they like them better.
As has been covered, not everyone has the wherewithal (fiscal and/or physical) required to gig tube rigs, but those who do often seem to lean towards the "real deal*".

Also, some players just can't hear the difference.
It would make no sense for that huge percentage of the TB community to spend thousands on a nice 150 lb. tube rig when they can buy a waist high stack of Asian manufactured transistor gear for $250 at Guitar Center, a stack that only weighs 50 lbs. or so that they can "one trip" to the family truckster after their semiannual gig.

Finally, there are some transistor rigs that sound pretty ef'n good IMO.
Even so, to a tube junkie they are a compromise, and to most serious players (tube or transistor) "compromise" isn't a viable option.

Playing what you like and playing what makes sense for your situation are often mutually exclusive.




*I’ll even stop referring to tube rigs as “the real deal” when someone can cite an example of a tube amp whose manufactures touts as being “transistor like” in its tonal quality.
Plenty of transistor amps claiming their tubyness though, hence… “The Real Deal” moniker.

 

[edwinhurwitz]

Yes, the SVT has always had a SS rectifier. And thanks for the claramicashun about the voltage vs wattage, Edwin. I still stand by my premise that a tube rec for an SVT would be very large and impractical, though, otherwise someone else would have done it if not Ampeg. Now the B-15...tube rec all the way for that one! Flirted with the idea of a SS rec on it, but nah.

Well, I was hoping that I was writing in a fashion from which people would infer that a tube rectifier in the SVT would be counter to the goals of the amp. What they wanted was a big powerful amp that would have a relatively stiff low end and a tube rectifier would subvert that. If they wanted the voltage sag, I'm sure they could have managed a tube rectifier, but bassists would complain about a soggy low end. A 5AU4 would probably provide enough voltage at a comfortable current and there are others with higher capabilities. I'm not an amp designer, just someone with enough knowledge to be dangerous, but I think it was a performance decision, not an arbitrary one due to lack of parts. However, it is true that a solid state rectifier is cheaper and easier to deal with than a tube rectifier.

Also, remember that the SVT was designed during the transition to transistors in general. You could get an "obsolete" Neumann U47 for $50 as people were abandoning the old technology for the "newer and better" transistors.

I love tubes and getting my hands dirty with solder. I have a Mercury Magnetics output transformer (bigger low end and multiple output impedances) waiting to go into my '67 Showman that I've done a bunch of updates to. It sounds amazing.

 

[edbass]

Yes, the SVT has always had a SS rectifier. And thanks for the claramicashun about the voltage vs wattage, Edwin. I still stand by my premise that a tube rec for an SVT would be very large and impractical, though, otherwise someone else would have done it if not Ampeg. Now the B-15...tube rec all the way for that one! Flirted with the idea of a SS rec on it, but nah.

It wouldn't be an issue to tube rectify an SVT, and you don't need a big one, a couple 6L6 sized GZ34's would likely get the job done.
I think the reason that it isn't done is that it would change the character of the big beast. It would soften up the SVT's strong back, change it's "attitude".

Same can be said for the B15, but the other way around. Also, the tube rectifier is likely why you still occasionally see 50 year old fliptops with the original factory caps in them.
I had my 70's B15 gone through a couple of years ago, with orders to replace anything that even hinted at being "questionable" and it came back to me with the original filter caps. I called the tech and he said "they test fine, wait until you see them bulging or hear the amp weakening" so I did, and they are still in there.


Sorry about the toe stepping Edwin!

 

[edwinhurwitz]

No problem!

 

[JimmyM]

You two Eds make some righteous points.

 

[Slough Feg Bass]

I'd love to get an old Bassman, but replace the power stage with a higher output tube circuit. I don't really know how to do that, but I'd love to give it a try. Like instead of the 2x6L6's, I'd like to put a power stage that has maybe 4 x 6550's.

I have dreams.

 

[BassmanPaul]

You can use a tube rectifier in an amp up to 50W or so. Some 100W amps use a pair of rectifier tubes in parallel to handle the load. voltage ratings aside, you'd need six tubes for an SVT. None of the usual crop of tubes would be able to deal with the high voltage required for an SVT. If a tube failed, the ones in parallel will try to take up the load leading to a cascade failure of the entire rectifier bank.

I see no advantage for tube rectification for an SVT. Guitar players like the "sag" that they introduce in their tube amps. For bass, not so much.

 

[Oobly]

To the OP: Just get yourself a bunch of Ampeg B15N's. Use as many as needed for volume..... May need a custom stand for them 'cos you should stack them vertically for best dispersion...

The B15N comes closest to "the sound I hear in my head" out of any amps I have heard. Don't hate me for this, Jimmy, but even an SVT doesn't do it for me.... well, maybe using the second channel and tweaking around a bit gets close enough.

 

[edwinhurwitz]

I'd love to get an old Bassman, but replace the power stage with a higher output tube circuit. I don't really know how to do that, but I'd love to give it a try. Like instead of the 2x6L6's, I'd like to put a power stage that has maybe 4 x 6550's.

I have dreams.

I think this would be a problem. The power requirements of even two 6550s would outstrip the abilities of the power supply. You might be able to get away with it with a Showman, but at this point, it might be best to simply get one of the kits that are out there and build it from scratch. It's better to operate a design close to its original intention than mod something so that you're trying to get it to do something that is way beyond its original scope.

But it doesn't hurt to dream!

 

[SactoBass]

I like tube better in every way. Nothing compares to it

But I never enjoy playing as much as when I have a great tube amp to plug into

The above two sentences sum it up rather nicely, I'd say.

 

[JimmyM]

To the OP: Just get yourself a bunch of Ampeg B15N's. Use as many as needed for volume..... May need a custom stand for them 'cos you should stack them vertically for best dispersion...

The B15N comes closest to "the sound I hear in my head" out of any amps I have heard. Don't hate me for this, Jimmy, but even an SVT doesn't do it for me.... well, maybe using the second channel and tweaking around a bit gets close enough.

I can get my sound out of either so it's all good to me. But unfortunately, I do have to hate you now.

 

[bassman blue]

Do I have to come into every single tube thread and straighten people out?



OK, so here's the deal...if you like solid state or hybrid, great. If you like tube, great. I've played all of it and own all of it and use all of it. But I like tube better in every way. Nothing compares to it, and while SS has gotten much better at mimicking tube sound over the last 5-6 years, it still ain't tubes. And I'll take a blind test playing them any time and I will be able to tell the difference 100% of the time. Modelers and such can sound like recordings of a tube amp, but stand in front of them and it's a whole different story.

And if you love tubes, you really don't care all that much about the schlep under ordinary circumstances. Takes a little longer to set up, maybe you'll do a little bit of deadlifting in the process...for someone with an injury or condition that prevents it, that's cool, but for me it's no big deal unless stairs or long walks are involved. And even if there's a long walk, I have a dolly so still not that much of a deal.

Now I've never had an audience walk out on us because I show up to gigs sometimes with a Micro VR or a BA110, but while the Micro VR is a fantastic little $300 amp, it's a $300 amp, and it's mostly an issue of schlep when I use it, and occasional laziness But I never enjoy playing as much as when I have a great tube amp to plug into, and the bigger the cab rig, the better. It will not make or break you as a player...if you make a mistake on a tube amp, it still sounds like a mistake...but it'll be an awesome sounding mistake!

haha.... right on! i agree 100%.