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Post subject: SS Rectifier
Posted: Thu Oct 22, 2015 7:08 pm
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I'm hunting for a new tube amp. There are lots of choices as you know. A few of my candidates say they use SS Rectifiers. I wonder if someone could clue me in on why this is good or bad. A lot of the product descriptions don't mention the rectifier at all, so I wonder how prevalent the SS rectifier is.
All of the amps on my list are high quality hand wired, American made. Thanks.

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Post subject: Re: SS Rectifier
Posted: Thu Oct 22, 2015 8:02 pm
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Solid-state rectifiers run cooler, provide a more stable source of high voltage, and eliminate one possible issue of tube failure. The trade-off is, that more stable HV source will never deliver the characteristic "tube sag" under high-volume situations that many vintage tube amps are noted for.

Arjay

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Post subject: Re: SS Rectifier
Posted: Thu Oct 22, 2015 8:50 pm
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Thanks Arjay, that helps. So not all good or all bad, but since I'm going for a lower wattage amp that I'll be able to crank with a band, I would probably want a tube rectifier, I'm guessing. That removes two of my four top contenders.

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Post subject: Re: SS Rectifier
Posted: Thu Oct 22, 2015 10:23 pm
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Up until about ten years ago I preferred solid-state rectifiers simply because it eliminated one potential tube-failure issue. But when I started collecting and restoring the old Fenders I grew to appreciate the sonic vibe of a tube-rectified platform. I still regard the diodes to be a superior method of rectification from a technical aspect but I don't think my vintage Fender combos (Princeton Reverb, Deluxe Reverb, Pro, Vibroverb, etc) would sound quite the same without a GZ34 or 5U4GB supplying the DC voltage.

That said, if you find a tasty-sounding diode-rectified amp, don't let the lack of a rectifier tube disqualify it from consideration.

Arjay

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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 2:12 am
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Tube or SS rectifier , both are good .


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 6:06 am
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Retroverbial wrote:
Up until about ten years ago I preferred solid-state rectifiers simply because it eliminated one potential tube-failure issue. But when I started collecting and restoring the old Fenders I grew to appreciate the sonic vibe of a tube-rectified platform. I still regard the diodes to be a superior method of rectification from a technical aspect but I don't think my vintage Fender combos (Princeton Reverb, Deluxe Reverb, Pro, Vibroverb, etc) would sound quite the same without a GZ34 or 5U4GB supplying the DC voltage.

Arjay


100% ! :)


In general, my experience with tube rectifiers are they sound better in amps of 5 to 40 watt range, than similar wattage amps with solid-state diodes. Above 40 watts, solid-state rectification gives more stable voltage and current (for those higher wattage amps), than tube rectifiers.

A well thought-out power supply setup (main filter caps, pi-resistors, and choke values) is more critical in a tube rectified amp. Staying within the tube's guidelines is important --- not only for tone and sag character --- but also for healthy long-life of the rectifier.

Unfortunately, I haven't found any modern day rectifier that can match the quality of vintage NOS ones. Esp 5U4GB, 5Y3GT, and 5AR4 (GZ34). Which are about 99% of the tube rectifiers used in most guitar amps of 5 to 40 watts.

There are plenty of good NOS or near-NOS 5Y3GT and 5U4GB tubes available. And considering, they will last years in a well-maintained amp, a couple two or three is all you really need. As for the GZ34, I recommend placing solid-state diodes in series with the anode plates. This will help prevent damage to the rest of the amp, if the GZ34 arcs-over and shorts, during use. A problem with some modern day made GZ34 tubes. NOS GZ34 and US made 5AR4 tube are very $$$. Thanks, to their use in both guitar and hi-fi amps.

Diagram of solid-state inline diodes, in tube amplifier. This example is a GZ34 in a Dynaco ST-70. An amp that is notoriously hard on the GZ34. Really, this amp should use vintage, healthy tubes.

Image


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 8:13 am
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Thanks a lot guys. I've never gotten this far into the makings of the amps. One of my top choices is an amp made by a one man operation called Soul Tramp. His 40w Serenity uses diode rectifier and large Mercury transformers. I was trying to stay in the 25 to 30w size, but his amp keeps hanging with the best of them. Plus he answers emails, which is an anomaly among the boutique builders. I'm going to have to make a spreadsheet to keep track of all this info. Making a smart amp decision is kind of like work.

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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 8:40 am
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Seems like a real promising design with a lot of usable features.

For those interested, here's a link......

http://www.soultrampamps.com/?page_id=62

Arjay

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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 9:02 am
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Looks like a nice amp. I guess he means solid-state diode rectification. Which, considering a GZ34 (5AR4) would prolly be needed for this amp, solid-state is a much more reliable way to go. As long as you can somehow emulate the sag of a tube rectifier. Although, the GZ34 has the least sag of most tube rectifiers.

EL34 driven amps have a great tone. A bit "browner" midrange than a good 6L6GC. Some of these amps have the ability to use either the EL34 or 6L6GC. Which maybe a nice feature.

Those Merc Mags are HUGE! This amp will surely have great bass. Big tone. My guess is similar to a Bandmaster head unit. Or the great Marshall Model 1987 Lead.

Good luck with the amp! Keep us posted.


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 9:29 am
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The only thing that has kept me from ordering the Serenity is there are a few other heads that are smaller, lighter and cathode bias, so I could swap 6L6's for the EL34's if I wanted. The Serenity is fixed bias. Since I plan on carrying the amp to rehearsal, small and light is on my radar. But I have no doubt the Serenity is a great amp, plus it's not overly large. I may still end up with it. There's lots of amps out there right now. It seems like I discover a new candidate every day. The problem is so many of them don't give full product descriptions, like Soul Tramp does, and I don't want to guess at what I'm paying for. I'm trying not to let cost be the deciding factor but a few of the amps that don't give full descriptions are twice the cost of the Serenity.

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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 9:45 am
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Rectifier tube sag is important in two areas.
In a vintage amp with relatively small filter capacitors and a tube rectifier, as the current goes up during a loud note, the rectifier voltage goes down. It lowers the plate voltage at high volume levels before clipping. This adds a slightly compressive effect that tends to round off the peak of a note just before the amp breaks up.
The second effect is to thin the overdriven power stage tone to a higher pitch.
When the power tubes are driven into overdrive, it creates the clipped square wave common to metal tone. The wave shape of the clipped portion affects the overdrive tone.
At initial overdrive levels, the square wave is relatively flat on top. Pushing the drive further will run the tube out of power sooner and the wave shape on top will not stay flat for the entire cycle. It sags down on the trailing edge as you push it harder.
This results in a sine wave on top of the leading edge of the square wave. While it is the same frequency as the fundamental wave, its wavelength is much shorter, so it sounds like a strong upper even harmonic, like adding an eee to your OOO
The tone of sag you generate is heavily dependent on consistent drive levels to acheive an even "sag" tone. A low gain amp driven hard is easier to maintain overdrive levels
Sag can be created in a number of ways. Any place you can starve the power supply can create sag. So small filter caps in the PS, A low capacity tube rectifier, or even switching in a power resistor on the B+ can create sag conditions.
Sag is mostly useful, howeever, only at maximum overdriven power levels. So it's unlikely to be used in a SS amp, whose clipping characteristics aren't usually musical.


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 9:56 am
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"So I could swap 6L6's for the EL34's ."

Only if the amp is designed for the swap. It needs a bias adjustment. And the sockets for the EL34 cannot have the suppressor grid (pin 1) connected to any voltage. Most Marshall amps have the suppressor connected to ground --- so it's ok to sub in a 6L6GC, which has no internal connections to the pin 1. You'd need to contact the builder, to be sure of this.


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 10:53 am
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BMW2002Ti wrote:
"So I could swap 6L6's for the EL34's ."

Only if the amp is designed for the swap. It needs a bias adjustment. And the sockets for the EL34 cannot have the suppressor grid (pin 1) connected to any voltage. Most Marshall amps have the suppressor connected to ground --- so it's ok to sub in a 6L6GC, which has no internal connections to the pin 1. You'd need to contact the builder, to be sure of this.

Thanks, another good piece of info. A couple of the amps I'm looking at have a switch on the chassis for going between 6L6 and EL34's. I was assuming that if the amp was cathode bias, it could use both of those tubes, but that's not necessarily the case. But if one is cathode bias and comes with EL34's, than 6L6's could probably be swapped in, as long as a bias setting is done?

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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 12:45 pm
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Nice amp . Why don't you go for a Fender blackface or silverface amps , real vintage not reissue ? Head or combo . For the same money or less you would have a great amp .

No need to be all original ,it will cost less


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Post subject: Re: SS Rectifier
Posted: Fri Oct 23, 2015 12:46 pm
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If the output is set to cathode-biased, Class "A" --- the 6L6GC and EL34 are prolly interchangeable. AS LONG AS the amp does not utilize the suppressor grid in it's circuit (pin 1 is active).


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