Tube or Solid State Rectifier?

[paulcampo]

I have a late 60's Sunn Solarus coming next week, and was informed it has the tube rectifier as opposed to the solid state. I was curious if anyone has experimented with rectifier tubes and found some good ones. I know the old Amperex and Mullard GZ34(5AR4) with 'DD' getters is a good one to get, but I dont know if I can afford one these days...any new production ones yielding good tone? I've heard about the Weber 'Copper Cap' solid state replacement to give a type type rectifier sag....anyone actually using this and could give a little feedback?
Thanks!
Paul -http://www.myspace.com/paulcampo

[Soundmasterg]

The rectifier tube's function is to convert AC to DC. It doesn't impact the tone directly as there is no signal passing through it. How efficient the rectifier is does impact the experience of playing the amp because it controls how much sag the power supply of the amp does when you hit it with large signal demands like when you are playing loud and hit a big power chord for instance.

If you had a Mullard/Amperex/JJ/EH GZ34 and subbed them in and out of the amp, resetting the bias each time because you have to, you might notice a 5% difference in the feel of the amp from one to the other, but it could also be due to the difference in the bias each time you do it, as it isn't an exact science. The new JJ GZ34 is a very good tube and is cheap. I'd go with it if I needed one. BTW, rectifier tubes last a long time.

I'm using a WZ34 Weber Copper Cap in my 1970 200S that I restored/modified. I use that amp for bass and the Copper Cap retains some of the tube voltage drop and sag, but it is a bit tighter than the actual tube. It is a good midle of the road option between a tube rectifier and a solid state rectifier, and the biggest nenefit in the Sunns is that it keeps the B+ voltages down a bit as they are 560v and up usually. I tried one in my Vox AC30 briefly when the original chinese GZ34 went south and I had to replace it. It sounded just as good as the JJ, but I ended up going with a NOS Amperex GZ34 that I had laying around as I like the sag better with it. I keep the Copper Cap around as a backup for my AC30 since it will almost never go bad. THey're cheap too, so I'd say get one and try it, but make sure to rebias the amp when changing to different rectifiers.

Greg

[paulcampo]

Hey thanks Greg...I actually like a tighter bass response as I typically play Marshalls in a 'clean mode' and they have that tight bass sound...I'm going to try to find a 'DD' getter amperex brown base GZ34, but I think I'll pickup a copper cap too...I noticed in addition to the WZ34, there is the WBR, WFW that also appear to be for GZ34...are these for different GZ34 applications or totally different? I noticed they all draw 225ma...so I'm not sure as I'm really just a guitar player who knows a little about tubes...I dont really understand the electrical ramifcations of subbing tubes...thanks again!
Paul

[Soundmasterg]

I'd email Ted and ask him what those others do. He's very quick to respond and has the best customer service in the business. Anytime you change the rectifier, whether you use a GZ34, a Copper Cap, or solid state diodes, you have to reset the bias. The rectifier converts AC into DC, but each is more or less efficient at that job than others, and will give you different DC voltages in your amp, which will of couse affect the bias voltage too. If you don't readjust the bias to a correct level in the amp when you change from one rectifier to another, you run the risk of your power tubes self-destructing.

Greg

[paulcampo]

Hey Greg, thanks very much for the info....this is something I was not aware of with rectifier tubes, and you probably just saved me money down the line somewhere... So you are playing bass through a 200S and went with using a copper cap, after trying the Amperex GZ34. Those copper caps must sound pretty good. What would you say the big difference was between the two? Which Amperex GZ34 tube do you have? They made a few different ones, and beware that some tubes while saying one company brand may actually be another company's make. Like many of the RCA 6550 tubes are actually rebranded Tung Sol. Some of the Amperex GZ34 out there are actually Mullard. Does the Amperex GZ34 you use have the metal or brown base? Single halo or 'DD' getters? I'd rather not spend the big money on an NOS rectifier. I used to do tube consultations for guitar players in California, and the rectifier seems to have a substanicial difference on the tone using some tubes, but not all. I recall the Amperex GZ34 with 'DD' getters and a brown base sounding the best. I hear the metal base is the absolute best sounding,but I've personally never tried one due to the price. I did hear that a rectifier tube while usually outlast all of your tubes in the amp, so I would consider the price if that is the case.
Thanks Greg

[Soundmasterg]

The rectifier tube doesn't affect the tone directly by itself since the signal isn't going through it. That said, it affects the tone by how well or poorly it converts AC to DC in the amp, and this is realized mainly as a feel difference when you play the amp up in volume where its clipping.

With bass playing, you usually want a tight response and a clean or slightly dirty sound that responds quickly, so a lot of sag from a tube rectifier isn't really the best thing in a bass amp. It sounded ok with the Amperex GZ34, but it sounded better with the Copper Cap. The main reason I went with the Copper Cap instead of a couple solid state diodes like the 1N4007 is that they don't emulate the voltage drop like the Copper Cap does. With solid state diodes, the plate voltage was around 580v, and with the Copper Cap it was around 560v which Worked better with the cap setup I had in the amp. If you're using the stock cap setup, anything over 525v is above the rated max voltage on the caps and isn't a good idea, so almost all of these old Sunns need to have the power supply setup modified and every little reduction with the voltage helps.

My Vox AC30 sounds pretty good with the Copper Cap in it, and sounded fine with the Chinese GZ34 that blew after 10 years, but with the Amperex it was overall just richer sounding. Since that amp is cathode biased, that could just be due to how the power tubes are now biased with the different rectifier in place. The Amperex that I used was the only one I had, which has the DD getters and brown base. I got it from my grandpa after he passed. He was a ham radio guy and had a lot of cool stuff.

If I was using an amp for guitar, I'd want a tube rectifier in it, or a Copper Cap as they sound great too, but I wouldn't spend the extra cash on a NOS rectifier unless the current quality production dries up as the JJ is just fine. Rectifier tubes last a long time as long as they don't get mechanically jarred often.

[paulcampo]

Thanks for the info Greg....I was just talking with Ted at Weber on the Copper Cap rectifier and there is only the one you mentioned. The others are for other 'non tube' applications. The amp is coming tommorrow as they tried to deliver it today but I was out at the time! I also managed to score an NOS/NIB Amperex 'DD' getter 'X' code GZ34...Yes! I think between the two I'll find the sound I'm looking for. I also play bass for recordings, so maybe I'll end up switching off....so do you know anything about the 12AT7 mod in lieu of the 6AN8 Conrad was talking about? It sounds very interesting and I was wondering just exactly how it 'maximizes performance' and what the 'sonic effect' would be...so how old is your VOX? I wish I had an old Vox amp!

[Soundmasterg]

Just make sure to re-bias the power tubes any time you change the rectifier.

Regarding Conrad's suggested mod, I can guess what he's talking about and even have an idea of the circuit arrangement, but unless you know how to work on amps yourself you wouldn't really understand. I have a hunch Conrad is taking the Fender driver from the Blackface Fender amps and subbing it into the Sunns, but you would have to ask him to know for sure what he has in mind. It would require a new socket hole to be made in the chassis, and a lot of rewiring and changing of some parts to make it work. It might sound better too but you almost have to try it to see.

My Vox is a 1993 Korg reissue that was made in England in the Marshall factory. Its an exact clone of the originals with the exception of a couple things like a PCB instead of the original wiring setup, an addition of larger air vents, and the addition of a standby switch. You'll find that the Korg reissues as they are known command about the same money as they were knew....~$1700 or so with the Celestion Blue speakers. They're a great sounding amp.

[paulcampo]

That sounds like a great amp to have! What type of EL84 tubes are you running? I like those Telefunkens but they are pretty hard to find in good condition today...Well I got my Sunn Solarus today and its really awesome! A lot of great clean tones as well as some pretty good dirt when you turn it up. It came with a solid state rectifier insert plug made by Diodes Inc. Are these all basically going to have a similar sound or is the Copper Cap really the one to have? Also the tremolo doesnt work but I'm thinking you NEED to have the footswitch to operate it...any ideas on making a footswitch for it? Its two RCA inputs, L and R.....thanks to all who have helped me with my questions...I'm proud to own such a great sounding under rated amp!
Paul

[rick.heil]

RCA footswitch is pretty simple - you can grab any regular 1/4" footswitch and get adapters from pretty much anywhere to make it RCA. Its a normal, simple footswitch - contacting the pair triggers the circuit to switch the effect.  I'm not sure which "side" (left or right) triggers the trem vs. the reverb, you could play around with it, or if you need the pedal.  If you're curious, take an RCA pigtail with a SPST soldered on the end of it and experiment.


Alternatively, if you wanted the official Sunn pedal, troll eBay for a while, they pop up occasionally.

[Soundmasterg]

The advantage of the Copper Cap in your amp as compared to the solid state plug is that it will emulate some of the sag of the tube rectifier, and it will lower the voltages in the amp a bit. If the can cap is still in there, then the lower voltages is a very good thing as it is running at voltages higher than what the cap is rated for with today's wall voltages. THe sag will make things a bit more touch responsive and a little less aggressive. For a guitar amp, I prefer tube rectifiers usually, and for bass, I prefer solid state. The Copper Cap is osmewhere in between the two for feel and sound. They're only $22 or something like that so get one and try it. I like them myself.

My AC30 came new with NOS GE EL84's, and when they wore out I put in EI EL84's. I prefer the GE's but the EI's sound and work great too. I have a quad of GE'sthat I use for recording purposes, and usually I run the EI's. I have 3 more quds of EI's that are pre-Balkan war stock, so I'm good for awhile. I wouldn't mind getting some Valvo EL84's, but money is the issue at the moment. Any AC30 that is close to the vintage spec with the Celestion Blue speakers will sound awesome. Tlefunken EL84's are nice, but not my favorite. Their 12AX7's are really nice and balanced too, but I prefer using them in hifi to guitar amps. I can tell you I'll never get rid of this AC30 unless I build myself a couple and they're better. I've compared it to a 1964 AC30 that a friend had, and where his was a 10 on the sound, mine was easily an 8.5, and for the price difference, (About $2000), we would both choose mine every day.

greg

[paulcampo]

Thanks for all the copper cap info...I'm going to pick on up as soon as I can. I like the massive clean headroom of the amp(6550s) as it will make a great blues amp; especially when you turn it up a little. I really like the 6550 tube sound the best. I also have a Sundown combo with 6550 tubes and its a great amp too.6550 seem to have the most headroom besdies that of a 'true' KT88... and btw, if you see one of these super rare Sundown amps get it! I would never sell it as its very unique. All this said, my main amps are Marshall JCM 800s with 6550s...haha...
I heard the Vox reissiues were excellent too...the thing is the price though. Hence my Sunn amp purchase...a good amp under 1000 bucks these days is hard to find let alone 500....I cant believe more people dont know about old Sunn amps...especially blues players. I've played in lots of old school 'Chess' blues bands and think this amp has the goods for most clubs though small clubs it might be too clean depending on the player. ...so a good find on EL84 for your Vox might be the old Amperex halo or D getter EL84. Look for the 'Made in Holland' on all kinds of tubes from Zenith to Hammond. You can still get em pretty cheap if you look. The trick is to know what you are looking at. A great way to get expensive Mullard EL84 tubes cheap(Very nice) is to look for G.E 6BQ5 tubes that say 'made in great britian' and dont have the GE etch code in the glass. I know what you mean about Telefunken EL84s. They are nice, but I think the very best I've heard yet are the early Mullard EL84 with D getters...pretty hard to find as they just didnt make alot of these...

[Soundmasterg]

Personally I think the 6550/KT88 is a little hard sounding for guitar use, but each to his own. For blues playing, unless you'r eplaying insanely loud and like clean sounds, or are using pedals or an attenuator, then in my experience the vintage Sunn stuff is too loud for most gigs. At the jam I go to every week (and Conrad sometimes makes it to) the guys down there use stuff like Deluxe Reverbs, or Conrad's new and very nice Blues Jammer. Pretty much stuff under 30 watts or so, and they're plently loud on 5 and are nice and gritty and overdriven.

The Vox stuff is great, and is pretty much the only way you can get that sound, but it is expensive. My amp was $1700 new, but its held it's value and is worth right around there now too. and I've had 14 years of solid use. I love all the Amperex stuff I've heard and am always on the lookout for good stuff. I get a lot of used pulls locally that are still good, and luck across some deals for new stuff from time to time. I haven't been lucky enough to find any new Mullard El84's yet, but I have five NOS Mullard 12AX7's that are in the original boxes. I'll just hold onto them for awhile longer...they're already worth way more than the $5 I paid for the lot, but they'll keep going up and up. They sound good, but the EI 12AX7's, when you find a good one, sound just as good if not better. They don't last as long of course, but thats ok when they're $5 each.

[paulcampo]

Yeah I understand your feelings on that Greg...I would agree with you on 6550 tone if it wernt for my stockpile of old USA Tung Sols. Theres NOTHING thats even close in tone that I've heard from the new stuff out there. Nothing has the warmth that the old T.S 6550 had. Sveltlana is the best I've heard. I own a pair of the reissue Tung sols as I was hoping for something closer in tone to the original than what they really are. They are just O.k to me. For me, I like the Svelts as they are closer to the old T.S sound. All that said, the 6550 tube is the hardest to drive to natural distortion with its massive 'headroom tone'.You do need to turn the amp up a little or drive the front end with a preamp as what I currently do. I think my new Sunn will be a killer blues amp! I  used to play in a 'Chess' blues band (a lot of Little Walter material) and that 50s-60s Chicago stuff is pretty clean; not the SRV blues tones.Yet I can drive the Sunn to warmth and its not to ungodly loud...I think! haha...When I get the tube Rec it will be even easier. The main thing I like about the 6550 is the wide dynamic range you get due to the headroom. I never liked the EL34 tube much for the very reason it seems to lack dynamic range due to its early breakup. While they drive to breakup easily and earlier, the thing you trade off is the dynamic range.I have owned the very best EL34s with the exception of metal base Amperex, and while the old ones do sound good, I still like the 6550 dynamic headroom more than the EL34 midrange 'honk'....To hear classic examples of the 6550 tube amp in action, just put on any Hendrix, Deep Purple and live Led Zep...granted all very loud bands...haha...I believe Jimi was also using the 6550 equppied Sunn amp for a while as well...but I do understand why some would not like the way the 6550 play...definitely not the EL84 chime, but it does have worthy tones worth digging into....but I think to be fair you should make sure to at least try to get an old pair of Tung Sol 6550 and hear what a good 6550 sounds like...they really seemed like they were the best 6550 made and no new 6550 has the warmth they did; thats the one thing all the new 6550s lack....of course at today's prices for old Tung Sol 6550s, its more pracitical to go with buying a small cottage in Maine...instead of a life supply of Tung Sol 6550...but who said musicians were practical!