Asking for the truth. 6v6gt amp run EL-34 , 6l6GC , 6V6GT

[fxer1982]

Can a tube amp run EL-34 , 6L6GC , 6V6GT tubes, if so how much needs to be done to the circuit for this to run them. yes i get that fact of setting up the tube bias for each to run...please chime in if there is a lot if extra wiring these were built to run 7408, 6V6 family of tubes. Thank You for any replies..

 

[vinylkid58]

Really depends on the amp. What is it and can you post a schematic?

jeff

 

[gadget73]

if it was specifically designed for the heater current it might work, but an amp designed for a 6V6 is not going to be happy about running the other types.

6V6 needs 0.45 amps to light
6L6 needs 0.9 amps
EL34 needs 1.5 amps

so EL34 tubes will need 3X the heater current just to light, 6L6 need double the current to light.

6V6 tends to run around 300 volts and into about a 10K load. The other tubes generally run more voltage and a lower load. They will work at lower voltages and a higher load but they won't make any more power than a 6V6 did, and may make even less. Kind of a waste really.

Drive signal may be an issue, both an EL34 and a 6L6 will need more voltage to the grid in order to hit full power even at lower voltage

TL;DR, I'll go with probably not.

 

[Al Casey]

Can a tube amp run EL-34 , 6L6GC , 6V6GT tubes, if so how much needs to be done to the circuit for this to run them. yes i get that fact of setting up the tube bias for each to run...please chime in if there is a lot if extra wiring these were built to run 7408, 6V6 family of tubes. Thank You for any replies..

Is it a guitar amp or a hifi amp?
It can be done if you add a transformer to heat the big bottles, or redesign the power transformer but it is not worth the trouble. The 6V6 is a nice sounding tube.

 

[kward]

Even if you work through the filament current issues, drive requirements and the feedback circuit causes other issues. To tune the feedback on an amp with any one of those three output tube types will deoptimize it for the other two tube types using the same feedback circuit. That is unless the feedback is setup on some sort of a switch that allows the correct feedback tuning to be applied for each tube type.

The only way I can really see this working if feedback is used, is to design the frontend of the amp with drive requirements for the most difficult to drive of the three tube types and use feedback that doesn't include the output stage.

So in other words, no this probably won't work well and I'd say is not a good idea since the design would be a compromise and not be optimized for two of the three output tube types.

 

[gadget73]

So in other words, no this probably won't work well and I'd say is not a good idea since the design would be a compromise and not be optimized for two of the three output tube types.

this has always been my thoughts about amps that claim to be able to run a bunch of very different tube types.

 

[Lavane]

I built a PP guitar amp kit for my son thats designed primarily to use 6L6 types.
But, it can he biased to use 6V6's, 6L6's, 5881's, EL34's and even KT-88's and 6550's. The amp only produces 25 watts max with any of those tubes. However the amp is optimized for 6L6's. We tried all those tube types expect KT-88's. It does sound best with the 5881's 6P3S-E's, and 6L6GC's. My VTA ST-70 can use 6L6GC's in a pinch. I wouldn't use them in that amp for very long though. It was designed to use EL34's, 6CA7's, and KT-77's. But I did try some KT-88's, and didn't think they sounded right in that amp. I guess KT-66's can be used also.
The big problem I see is that any given amp is optimized for a particular power tube. Even if the B+ voltage can support a wide range of tubes and the power transformer can handle any additional current that may be needed for certain tubes, and the amp has fixed bias so it can be adjusted for all those tubes, the amp probably won't sound quite right using tubes it wasn't designed to use.

 

[Mr Boochie]

So in other words, no this probably won't work well and I'd say is not a good idea since the design would be a compromise and not be optimized for two of the three output tube types.

I look at these multi-output tube option amps as mostly an advertising gimmick. I never liked them, as they always compromise the final sound.

You want a nice 6V6GT amp — buy one. If you want a 6L6GC or EL34, buy one made for those tubes. Simple, right?

Call me a rock-headed purist!

You know, a well-made 6V6GT amp can sound just as loud and bass-impressive as a moderately priced 6L6GC amp. So, if the amp isn't producing enough power, changing the tubes isn't the answer. There's more to an amp than the output tubes.

 

[TriodeLuvr]

One other aspect to this is that the heater supply would need to be regulated DC. Otherwise, a transformer that provides the correct voltage for a quad of, say, EL34 will likely produce excessively high voltage with 6V6. Transformers are rated for output voltage at a specific load, and the voltage will vary when more or less current is drawn.

Jack

 

[Musictubes]

This topic has come up multiple times. There are basically two camps, either they are imperfect wastes of time or they are a fun way to change the sound of your system. I am firmly in the latter camp.

I have two amps made specifically for rolling different kinds of tubes. Both allow manipulation of b+ to account for tubes as different as 6f6 to kt88. The first amp I got was a Dennis Had Inspire KT88 Firebottle. It is a single ended pentode amp with a regulated screen supply as well as a regulated b+ for the dual triode driver. You can adjust the b+ for the output tubes by using different rectifiers. Use a 5y3 for something like a 6v6 and a 5ar4 or solid state diode for the bigger output tubes. I usually have some sort of 6l6-oid in there (currently a pair of 6ar6) and I use a 5u4gt. I think the maximum b+ you can get with this sort of setup is shy of 350v so you’ll never get the power out of the likes of el34 or kt88 that you could otherwise. Single ended amps aren’t really good for high power in any case IMO.

My other amp is a custom differential push pull that was built for me. No sane person would ever sell an amp like this to the general public but I’m very happy that this madman met a crazy Amp Designer/builder. It uses solid state rectification via a Maidia 21st century regulator. There is a pot allowing me to adjust the b+ between 250v-400v. It is manual bias with individual adjustments for each output tube. In addition I have banana jacks on the back that allow me to use external supplies for the heaters so I can take advantage of all of the cheaper, odd voltage tubes especially for the driver tubes. It uses Monolithic Magnetics 8k output transformers which allow both triode and ultra linear operation.

I am not privy to the feedback mechanisms used in each amp. I’m pretty sure Dennis Had is just a wizard. Single ended pentode operation is tricky in any case but he has made an amazing machine. I am seriously considering getting his parallel SEP version that uses oa3 and the like for regulation duties.

I have never understood why people are hung up on “optimizing” tube amps. Optimizing for what? Max power, lowest distortion, perfect square waves, lowest output impedance? Why are you messing with tube amps at all if those are the kinds of things you’re looking for? The only reason to use tube amps at all is because you like how they sound despite not being optimal amplifiers.

And this is where amps made specifically for rolling tubes shine. What happens when you buy an ST-70 or a Mac and your system sounds worse than before? You’d have to change an entire component of the system to rectify it. Worse still, what if you wanted your system to sound different for different kinds of music? Commence pearl clutching and mumbling that there is only one true way for a stereo system to be enjoyed… Never mind that there are loads of “optimized” amps that sound very different driving different speakers. Which optimized sound do you prefer? Conrad Johnson, Audio Research, Quad, McIntosh? It is so much easier to have one amp you can get different sounds out of.

Most importantly it is just fun to play with different tubes. It is a different way of enjoying the equipment. It is akin to cooking really. It is all done to taste. Tune rolling is an active way to interact with your system. If you like the idea of that then amps made for rolling will give you a lot of enjoyment.

 

[Mr Boochie]

Most importantly it is just fun to play with different tubes. It is a different way of enjoying the equipment. It is akin to cooking really. It is all done to taste. Tune rolling is an active way to interact with your system. If you like the idea of that then amps made for rolling will give you a lot of enjoyment.

Fun constantly changing things around is one thing. Optimizing for a set circuit is another.

Two schools of engineering philosophy. And as we know by now, both exist. Neither is really better than the other.

Right?

 

[gadget73]

Neither is really better than the other.

Just ask anyone, and they'll tell you one is better. the trick is nobody is going to agree on which.

 

[TriodeLuvr]

The only reason to use tube amps at all is because you like how they sound despite not being optimal amplifiers.

Maybe you should read the room before making a statement like that. I use tube amplification because it is consistently more transparent and nuanced than solid state. I have owned and heard some very fine SS gear over the last five decades - Hafler, Crown, Levinson, GAS, Luxman, etc., etc. - but nothing ever quite equaled the all-tube system I'm using now. Seriously, if you want to disparage tube gear with claims that optimization is meaningless or unimportant, you might be in the wrong forum.

Jack

 

[Mr Boochie]

Just ask anyone, and they'll tell you one is better. the trick is nobody is going to agree on which.

After years, I've come to one conclusion. Hobbyists of all kinds can be the hardest rock heads.

Within 5 seconds of talking or reading a post, you can tell which ones are best left alone. They are always right, in their own mind.

 

[Mr Boochie]

Maybe you should read the room before making a statement like that. I use tube amplification because it is consistently more transparent and nuanced than solid state. I have owned and heard some very fine SS gear over the last five decades - Hafler, Crown, Levinson, GAS, Luxman, etc., etc. - but nothing ever quite equaled the all-tube system I'm using now. Seriously, if you want to disparage tube gear with claims that optimization is meaningless or unimportant, you might be in the wrong forum.

Jack

Yes — Dissing tubes in a Tube thread could be considered trolling. Maybe...

To me, it's like posting how bad Ford engines are on a Ford Truck website.

 

[Musictubes]

Fun constantly changing things around is one thing. Optimizing for a set circuit is another.

Two schools of engineering philosophy. And as we know by now, both exist. Neither is really better than the other.

Right?

Right. I was trying to get across that tube rolling was a different way of enjoying your system. Different people like tube amps for different reasons. The usual attitude here in response to the original question came very quickly, Amps made for tube rolling aren’t worth bothering with because you can’t optimize them. My post was to stick up for how I enjoy the hobby and make sure that if they like the idea they aren’t dissuaded by nay sayers.

You can enjoy your tube amps any way you want! Have fun, if you’re not enjoying it your doing it wrong

 

[kward]

I was trying to get across that tube rolling was a different way of enjoying your system.

Point taken. It's definitely a preference thing as to what a person enjoys. Tube rolling can be fun, exploring how different tubes sound in the same circuit. Speaking from my own experience, many years ago I explored power tube rolling. I built several amps that allowed power tube types to be swapped. When tube rolling with that amp, I just didn't get that much satisfaction out of it, since the tube type the amp was optimized for sounded a whole lot better than the tube type the amp was not optimized for.

That being said, I do tube roll all the time, I just limit it to the same family of tubes by different manufactures or date codes, etc. Yesterday in fact I was tube rolling a pair of new production Tung Sol 6SN7s against a pair of old stock RCA 6SN7s. I was surprised how decent the new production 6SN7s sound!

 

[Musictubes]

Maybe you should read the room before making a statement like that. I use tube amplification because it is consistently more transparent and nuanced than solid state. I have owned and heard some very fine SS gear over the last five decades - Hafler, Crown, Levinson, GAS, Luxman, etc., etc. - but nothing ever quite equaled the all-tube system I'm using now. Seriously, if you want to disparage tube gear with claims that optimization is meaningless or unimportant, you might be in the wrong forum.

Jack

Did you read the rest of my post? I clearly love tube amplifiers. I stand by my point that traditional amplifier optimization is a kind of silly stance to take when dealing with tube amplifiers. Now if you are going to optimize around sound quality I can get behind that. Amplifiers that allow you to roll different kinds of tubes is one way to do that.

My first job out of college in the mid 90s was selling hi-Fi gear. Sold a ton of Denon, Parasound, Rotel, McIntosh amps. The dealer, Sound Approach in Newport News, had been a McIntosh dealer for a very long time. McIntosh had recently been sold to Clarion, or its holding company or whatever and a bunch of folks decided to leave when that happened. Several engineers from McIntosh formed Gordon J. Gow Technologies as a tribute to the man and what he strived for. Joe and another guy I can’t remember the name of used to be sent out by McIntosh to dealers to do amp clinics. You would bring your amp in and they would measure it to see how it actually performed compared to its specs. All brands were welcomed, the McIntosh folks knew that their amps would perform as they should and they would always have some to compare to what the customers brought in. It was good, nerdy fun with the occasional blown amp. When you put your car on a dyno you gotta be prepared for blown engines after all. My boss was friends with those guys and was selling products from their new company and so agreed to do an amp clinic like old times for him.

Anyway, my grail amp at the time was an MC 240. A customer of mine had one and I thought it was the most amazing thing ever. I asked these former McIntosh engineers and they rolled their eyes so hard they might pop out. Both of them made it very clear that all of the engineers there were very happy to ditch tubes and encouraged all of their tube customers to “upgrade” to solid state offerings. They told me that they did the best they could with tube technologies but were only ever to make the amps they wanted once solid state devices became really good. I kept my mouth shut since I was well aware of what then current Macs were like. I demoed them all time in people’s houses time and I would have taken the old, obsolete MC 240 every time. The only word I can think of to describe how those guys felt about tube amps, and their proponents, is contempt. At best they thought tube lovers were misguided, they leaned more towards them being stupid. I can’t help but see McIntosh’s reintroduction of tube amps a few decades later cynically…

This is what I’m talking about when I talk about optimization vs. tube amps. “Serious” audio engineers dumped tubes as soon as they could. I am all for amps optimized for how they sound as opposed to raw technical performance. Tube rolling amps will never be technically optimized but they can sound amazing. That was what I was trying to get across.

 

[Musictubes]

Point taken. It's definitely a preference thing as to what a person enjoys. Tube rolling can be fun, exploring how different tubes sound in the same circuit. Speaking from my own experience, many years ago I explored power tube rolling. I built several amps that allowed power tube types to be swapped. When tube rolling with that amp, I just didn't get that much satisfaction out of it, since the tube type the amp was optimized for sounded a whole lot better than the tube type the amp was not optimized for.

That being said, I do tube roll all the time, I just limit it to the same family of tubes by different manufactures or date codes, etc. Yesterday in fact I was tube rolling a pair of new production Tung Sol 6SN7s against a pair of old stock RCA 6SN7s. I was surprised how decent the new production 6SN7s sound!

I keep hearing that some of the new Chinese 6sn7 sound pretty good but I can’t get over their price! 12sn7 and even 7n7 are still much better priced. I just got a handful of Brimar 13d1 for $10 a piece from a dealer. Those are 25v *sn7 tubes, the equivalent Brimar 6sn7 (13d2) will be north of 1k if you can find them at all. I’m afraid I’m not a big fan of the current Tung Sol 6sn7 but I wasn’t a huge fan of the RCA either lol. I’m a sucker for early Sylvanias and British 6sn7s.

 

[mcgjohn]

That is a pretty wide range of octal output tubes to use in the same amp. If you download the tube datasheets for each tube mentioned and compare them, you'll find the B+ for the larger output tubes will greatly exceed the max B+ for a 6V6 or similar. If the amp claims to be able to run all these tubes, either the B+ has been lowered significantly or there may be a switch to make the change. If lowered significantly then a 6550 or KT88 will provide reduced power output and may not be operating in an optimum range.