Replacing a tube rectifier for a solid state

[denton57]

I think I want to do this for my B25. I am just not used to the sag, and would love a little more power/headroom. What should I go with? Weber copper or tubedepot's version? Is there a difference between these two except the price?

Also, anyone put 6550's in their B25?

 

[coreyfyfe]

There's also this one:

Invalid Link Removed

looks the same as the tubedepot without their sticker and markup.

http://www.tubedepot.com/tdssr.html

I don't know much about them though, so I can't really say which one is going to give you the best results. Just that you can find it cheaper.

 

[bebop1]

I have been told, by an experienced tube repairer, that the 5AR4 tube rectifier (used in my B15N) is very close to the solid state rectifiers in spec. and that I would not likely notice a difference between the tube and SS rectifiers in sound, output or sag. Other tube rectifiers do, in contrast, sag considerably and are prizesd by some guitards.

Of course the SS versions are so cheap (<$25) that they may be worth the experiment and are always a good backup to have.

 

[BassmanPaul]

If you replace a tube rectifier in a vintage amp you may well run into cap problems due to the increased high voltage. A lot of these amps were designed when mains voltages were 115V. today in many areas it's running closer to 125V. Thus your B+ is already higher and you could take the working voltage in the amp over the ratings of the caps.

This amp IIRC runs 6L6GC. These have a heater rating of 0.9A. The 6550 draws 1.5-1.6A each or close to double that of the 6L6. Power transformer will run hotter leading to a shorter lifespan. Putting the SS rectifier in will offset this draw somewhat but it's still not something I would do.

Paul

 

[chicago_mike]

Not to mention the impedance mismatch of the output transformer.

If your amp hasnt had a cap job in a while then replacin the caps mjight help, also nowadays you can get higher rated caps that woiuld take the increase of the B+. Strange that we say B+ when there is no more a b or c battery.

 

[beans-on-toast]

Most solid state replacement modules are encased diodes mounted on an octal socket. These units are good because in addition to providing SS rectification (which is good for bass), there is less current draw on the transformer heater circuit because the 5AR4's heater is not drawing power. For a 5AR4, this is typically savings of 1.9A @ 5 V = 9.5 Watts.

The advantage of the Weber product, is that it has a thermistor build in to reduce the current inrush. The slow turn on that the thermistor provides is not as slow as that of a 5AR4 tube, but it is still good to have.

Weber makes two products to replace the 5AR4, one with build in sag (WZ34) and one without (WS1). The WZ34 has voltage dropping resistors built in to emulate the drop of a 5AR4, thus no extra voltage in the amp. The WS1 is best if you want to avoid sag. I use both, the WS1 is in a B15N.

 

[denton57]

Most solid state replacement modules are encased diodes mounted on an octal socket. These units are good because in addition to providing SS rectification (which is good for bass), there is less current draw on the transformer heater circuit because the 5AR4's heater is not drawing power. For a 5AR4, this is typically savings of 1.9A @ 5 V = 9.5 Watts.

The advantage of the Weber product, is that it has a thermistor build in to reduce the current inrush. The slow turn on that the thermistor provides is not as slow as that of a 5AR4 tube, but it is still good to have.

Weber makes two products to replace the 5AR4, one with build in sag (WZ34) and one without (WS1). The WZ34 has voltage dropping resistors built in to emulate the drop of a 5AR4, thus no extra voltage in the amp. The WS1 is best if you want to avoid sag. I use both, the WS1 is in a B15N.

So the WZ34 would be just like a tube with no added voltage, but with the same sag? The WS1 would eliminate sag, boost output, but also increase voltages?

 

[beans-on-toast]

So the WZ34 would be just like a tube with no added voltage, but with the same sag? The WS1 would eliminate sag, boost output, but also increase voltages?

More of less, yes.

There is a voltage drop across a 5AR4. The drop varies according to the manufacturer. NOS tubes tend to drop less voltage than the new ones. When you replace the tube with the diode module, that drop reduces to the drop across the diodes, 1.4V. The voltage drop across the WZ34 is 17 volts. The WS1 is the same unit without the dropping resistors so the drop is 1.4V. Details are here: [Invalid or Expired Link Removed].

They also sell a kit, SS rectifier tall. You can use the resistor you want to attain any desired drop. Here is the schematic. Note that this kit does not include the thermistor. I believe that they use a CL-90 in the copper cap. Link Removed
Link Removed
Invalid Link Removed

 

[denton57]

Thanks beans. So if I wanted something similar to a v4b, I should go with the ws1 right? Since the v4b is ss rect?

 

[beans-on-toast]

Thanks beans. So if I wanted something similar to a v4b, I should go with the ws1 right? Since the v4b is ss rect?

Oh, I see where you're going now.

Yes, WS1, but I would try both and see which one your amp likes the best. BUT....

A solid state rectifier will stiffen up your power supply a bit and reduce distortion when pushed. It might give you some of the additional headroom that you are looking for. When the amp sags, it distorts, thus less headroom. I don't believe that this is going to turn your B25 into a mini V4B though.

The V4B has a beefier power supply. It also puts out double the power. Assuming your power transformer and capacitors can take it, changing to 6550's is only going to give you a little more headroom but the difference will be subtle. The problem is, the V4B has a bigger transformer which means more reserve power, and larger capacitors to hold that reserve. This, coupled with other factors, translates into a deeper, fuller sounding bass with more headroom. The B25 power supply could be redesigned but this would involve major changes.

The B25 is a really nice amp. A SS rectifier will help a little with the sag. As a first step, it makes sense to try converting and see.

 

[mongo2]

I think I want to do this for my B25. I am just not used to the sag, and would love a little more power/headroom. What should I go with? Weber copper or tubedepot's version? Is there a difference between these two except the price?

IME replacing the tube for a SS rectifier in my B-25 didn't increase the headroom or power all that much, it just helped with the sag a bit. I used the Weber without the dropping circuit.

 

[denton57]

Awesome. I'll order the ws1 and check it out. Mongo, are you running the original caps or newer ones?

 

[JimmyM]

Well good luck to you with it, but there's no way I'd buy a tube amp and try to make it sound more like a SS amp Then again, I use an SVT which has SS rectification, so I guess I can't talk. But I have no interest in replacing the rec tube in my B-15.

 

[denton57]

Well good luck to you with it, but there's no way I'd buy a tube amp and try to make it sound more like a SS amp Then again, I use an SVT which has SS rectification, so I guess I can't talk. But I have no interest in replacing the rec tube in my B-15.

I hear ya, but after I listened to a recent gig recording, it seemed like I was slow or something. Very warm, yes..but I guess I am just used to my old SVT. The V4 is also SS rectified. I have no problem trying to model those.

My amp may have some tired tubes and caps too. They're original. I'm hearing some popping and cracking sometimes and some static. Still sounds good, but I want it at top condition of course. Also needs a 3 prong power cord!

 

[bebop1]

Well good luck to you with it, but there's no way I'd buy a tube amp and try to make it sound more like a SS amp Then again, I use an SVT which has SS rectification, so I guess I can't talk. But I have no interest in replacing the rec tube in my B-15.

The rectifier tube just converts AC to DC power for the tubes. A SS rectifier doesn't effect the tone at all and is not in the tone creating part of an amp. It might give you a bit more power output (increase available power to the power tubes) and possibly give you a bit faster attack feel (like in the SVT). I might give it a shot in my '65 B15N, especially the Weber version which we are being told might be easier on the caps.

BTW JimmyM, I am loving the tone of the Micro-VR head. It's just a tad underpowered for loud stages, but it can crank pretty good @ 4 ohms through my two Markbass 112 cabs. It also sounds just as spendid as a preamp through my LMII and two 112 Markbass cabs when I need big volume..

 

[JimmyM]

bebop, don't you start with the Micro VR stack! I have never lusted after an amp strictly on looks but I want one of those really bad based strictly on looks

 

[mongo2]

Awesome. I'll order the ws1 and check it out. Mongo, are you running the original caps or newer ones?

Original caps.

 

[bebop1]

bebop, don't you start with the Micro VR stack! I have never lusted after an amp strictly on looks but I want one of those really bad based strictly on looks

Sometimes it is just healthy to capitulate to those lesser, baser, vain desires! And actually in this case, it's a satisfying piece of kit. I am pleasantly surprised by its capabilities but it, of course, won't replace anyone's main rig.

 

[BassmanPaul]

The rectifier tube just converts AC to DC power for the tubes. A SS rectifier doesn't effect the tone at all and is not in the tone creating part of an amp. It might give you a bit more power output (increase available power to the power tubes) and possibly give you a bit faster attack feel (like in the SVT). I might give it a shot in my '65 B15N, especially the Weber version which we are being told might be easier on the caps.

Sorry, i disagree. The power supply does have an impact on how an amplifier sounds and feels. Using s SS rectifier "stiffens" the supply and provides a bit higher B+. Just remember that the original caps have aged and become more sensitive to over voltages. I'm not just talking filter caps here but coupling caps too. In my B15 the coupling caps are 400V working. The B+ level is over 500V at the main filter. When you swap to SS rectification ALL the coupling caps are going to get virtually the full off load B+ voltage until the heaters warm enough to pass current. The caps feeding the output stage have things a little harder as they terminate to the negative bias supply of around 50V. That means that while the heaters warm, the 400V caps have about 550V across them. They will eventually fail and most likely short. That will destabilize the output stage causing it to run away and possibly take out the output transformer. Stuff like this can and does happen and you have to be aware of the pitfalls in ANY modification of a tube amp.

Paul

 

[WalterBush]

The rectifier tube just converts AC to DC power for the tubes. A SS rectifier doesn't effect the tone at all and is not in the tone creating part of an amp. It might give you a bit more power output (increase available power to the power tubes) and possibly give you a bit faster attack feel (like in the SVT).

Granted, not a bass amp, but switching out the 5AR4 on my Seymour Duncan convertible for the Groove Tubes SS equivialent resulted in a vastly different tone, feel, and earlier onset of distortion than the tube rectififier.

I can't say whether it damaged the caps at all or not, though. They were on their last legs by the time I got the amp in the first place...right now it's down until I get it recapped. I'd definitely get your amp tech's advice before switching; it may be that beefing up a few caps here and there takes care of any problems before they start.