Rectifier Bias Mod!!!

The new rectifier's going to the amp shop in Chicago next weekend for a bias trim pot installed in place of one of the 4 ohm speaker jacks. I can't wait, after that it really will be my ultimate amplifier. Super excited, and I'll keep posted what it does to the overall sound of the amp. I'm also waiting on some SED =C= 6L6's coming in the mail from Doug's, that's equally as awesome!! :mrgreen:

how much fpr the tubes?

konstantine RK said:

how much fpr the tubes?

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They are about $130

you'll be amazed after installing that bias pot. i installed one on my roadster and it opened up the full potential of my amp.

good luck and enjoy yours when it's ready.

Fluff, you're close....120 and some change from Doug's Tubes, he's really a good one to get tubes from. SED's cost a bit more than others, but boy do they sound sweet. If cheaper tubes are wanted, JJ 6L6's are what I go for.

The amp went into the shop today, I talked it over with the tech and we decided on drilling a new hole in the chassis for the trim pot, so I can keep everything and still get the pot reachable on the outside of the amp. Nick at Dr. Fretgood in Chicago designs and builds his own amps, so this is gonna turn out great. He's a great guy to talk with.

Well, Nick @ Dr. Fretgood in Chicago finished my amp ahead of schedule and I picked it up today. The bias mod is awesome, the best way to describe what it did to the Dual Rec would be to say that it "filled it out." It became louder, and the sound just "mixes" great, if that makes sense. The harmonics are richer, and the amp has no sterile sound left at all. It warmed it up a great deal. I found it does not sound the best to me at 70 percent dissipation like the Soldano did. If I put it there, I don't like it. It's best @ 55-60 percent dissipation. I can understand why Mesa does not put one of these in stock, but they should. Makes such a big difference. It was installed just above the loop switch jack on the back and is an external shaft. Once set it's "locked" stationary with a dab of hot glue, which is easily removed to adjust the pot and is strong enough to keep it put once adjusted. I really favor this over the internal pot of the Soldano. With that amp I had to take the chassis out of the headshell and turn it upside down. This amp, I leave it all together. Very easy to do. I just use the same bias probe and technique I used with my Soldano, nothing different. I would recommend this to any rectifier user, it makes a great amplifier even better. :mrgreen:

Hey there...
Got my Dual Rectifier back today, it had to be checked for malfunctions before I go up in flames. The Tech also decided to do a built-in Biss-Poti. He also pushed the Bias a Bit up, for the new JJ6L6 were running cold a bit. Now the Recto is a Killer...definitly!

Removing the slave out jack would have been better than drilling holes. Now you're stuck with an amp that's noticeably modded. The slave out jack is a better choice since most users don't even use it, and it's easily replaceable.


Personally, I wouldn't go for a tech who advocates irreversible mods. Modded amps are much harder to sell than stock ones.

mikey383 said:

Removing the slave out jack would have been better than drilling holes. Now you're stuck with an amp that's noticeably modded. The slave out jack is a better choice since most users don't even use it, and it's easily replaceable.


Personally, I wouldn't go for a tech who advocates irreversible mods. Modded amps are much harder to sell than stock ones.

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Whew! Good thing it's my amp and not yours. That way you don't have to worry about it. :wink: So don't.

Wow. Way to be a dick with your 24 posts. Rock on with your bad self, ninja.

I'll make sure to reserve my advice for other members of the forum from now on

mikey383 said:

Wow. Way to be a dick with your 24 posts. Rock on with your bad self, ninja.

I'll make sure to reserve my advice for other members of the forum from now on

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Well, I'm not a ninja, although that would be really cool if I was. Also, it must mean because you have over 1000 posts you must be resident expert around here. And because I have 24 I'm an idiot. My apologies.

Let's go over some things, shall we?
1. Removing the slave out jack would have been better than drilling holes. Your opinion.
2. Now you're stuck with an amp that's noticeably modded. And?
3. The slave out jack is a better choice. Your opinion.
4. It's easily replaceble. Fact.
5. I wouldn't go for a tech that advocates irreversible mods. I would.
6. Modded amps are much harder to sell than stock ones. How did you know I was gonna sell
my amp? That's right you didn't because I'm not.

Check things and you will find that you are the one who broke into my thread and bashed the mod I did to my amp and thought their way was the only way. Who's the dick? I am an adult and I'm going to assume you are too so maybe we can move on.

For being an adult, you sure act like a butthurt little boy. This isn't HC or UG, so don't start coming in here acting like an asshat. If you're going to get all butthurt over someone's opinion and/or advice, then maybe you should go back to HC or UG or where ever it was that you came from, or just stay off the computer all together.

Since you already had mentioned that you were having it installed in place of one of the 4 ohm jacks, obviously you didn't want something invasive, but your tech talked you into it anyway.

I'll make sure to stay out of your threads from now on, don't worry. And with the way you're behaving, don't be surprised if everyone else does too

To end the "I'm the big, smart guy" run and return the thread to the amp stuff, I just want to add that Mesa's fixed bias system definitely wins for being the more practical.

BUT - any amp can benefit from a bias adjustment, it's like a "necessary evil" if you want to "trim" the amp to your likings. I think it makes more of a difference than tube brands, for example (if the change is not-so-subtle), but it can also destroy an aspect of your amp - you'd end up with a killer drive and would be left with a shitty clean tone, so there is a lot of room for error.

I have 2 questions (hope this doesn't become a thread-jack):
1. What are the the "normal" milivolt values for a healthy dissipation percentage for 6L6s (about 40-45mV per tube, from what I read)? I'll be helping my badmate bias his 6L6 amp after he retubes it and I don't want to screw it up by yanking the bias too high/low.

2. OP - how did it affect your clean tone/clean headroom? I found that higher bias made my JVM's clean a bit darker...

mikey383 said:

I'll make sure to stay out of your threads from now on, don't worry.

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Ok, thanks!

Jackie said:

To end the "I'm the big, smart guy" run and return the thread to the amp stuff, I just want to add that Mesa's fixed bias system definitely wins for being the more practical.

BUT - any amp can benefit from a bias adjustment, it's like a "necessary evil" if you want to "trim" the amp to your likings. I think it makes more of a difference than tube brands, for example (if the change is not-so-subtle), but it can also destroy an aspect of your amp - you'd end up with a killer drive and would be left with a sh!t clean tone, so there is a lot of room for error.

I have 2 questions (hope this doesn't become a thread-jack):
1. What are the the "normal" milivolt values for a healthy dissipation percentage for 6L6s (about 40-45mV per tube, from what I read)? I'll be helping my badmate bias his 6L6 amp after he retubes it and I don't want to screw it up by yanking the bias too high/low.

2. OP - how did it affect your clean tone/clean headroom? I found that higher bias made my JVM's clean a bit darker...

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Hey Jackie...I measure my bias in Milliamps with a bias probe that plugs into my multi-meter. I use either JJ6L6GC or SED=C= 6L6's, which are both 30 watt tubes. This is their max plate dissipation. To get a tube to come out of crossover distortion, usually around the 70% mark is where they need to be, but your ears will tell you for sure. In my Soldano I had them right at 70%. With this daul rec I find I like them around 60% or so. You can use your ears as long as you run the numbers and check that you're not getting too close to max dissipation. The hotter you run them, the faster they'll wear out also, so just keep that in mind. I had a pair of tubes I ran really hot once last about 6 months. What milliamps equals what percentage depends on your plate voltage, you'll use this in your calculation. Eurotubes has a great video to watch that explains biasing in it's entirety. "Average readings I would say would be somewhere between 36-44 milliamps, depending on plate voltage.

As for the clean channel, I wouldn't say it made it darker as much as I'd say it warmed it up and made it more open, or round. The Soldano I had gave the exact same result depending on where I ran the bias. This dual has a great clean channel and that was one of the deciding factors of getting it. I have no experience with older rectos, but I know this one is great.

xxFIXXEDxx said:

mikey383 said:

I'll make sure to stay out of your threads from now on, don't worry.

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Ok, thanks!

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after modding have you tried any other tubes? i replaced mine with SED C made a huge difference.

[/quote]after modding have you tried any other tubes? i replaced mine with SED C made a huge difference.[/quote]

I've always been on the fence between JJ6L6's and SED =C= 6L6's.....with the SED's having the slightest edge over ther JJ's for me. After going back and forth with this new dual rec, I've found that with this amp I like the JJ's more, especially using my Les Paul. The SED's match well using my Explorer, but the JJ's in this amp are just unreal with the Les Paul, and that's my #1. I don't have much liking for the stock 6L6's that came in the amp, they're in the drawer for backups to the backups.

@xxFIXXEDxx

dude, calm the **** down. this is a place for fellow boogie users to converse and share opinions on gear. he never said the fact that you have 24 posts makes you a noob, he just doesnt want random flamers coming on the board acting like they own the place, when he clearly been here longer. there was nothing even remotely provocative or aggressive in his post. he was voicing his opinion on the thread topic, and you acted like an immature 12 year old trying to pick a fight. get over yourself.

rocknroll9225 said:

@xxFIXXEDxx

dude, calm the f%&# down. this is a place for fellow boogie users to converse and share opinions on gear. he never said the fact that you have 24 posts makes you a noob, he just doesnt want random flamers coming on the board acting like they own the place, when he clearly been here longer. there was nothing even remotely provocative or aggressive in his post. he was voicing his opinion on the thread topic, and you acted like an immature 12 year old trying to pick a fight. get over yourself.

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OK mom! :shock: Thanks! Gotta love the interwebz.....this is starting to get funny. Back on topic, the Dual is really making me smile!! This bias mod is great.