Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rake on May 09, 2018, 07:26:22 am
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I know there's more opinions in the world than there is buttholes when it comes to what tubes sound best
but, in my personal opinion a pair of overdriven 6V6's is the fat cat's backside. (again just my opinion)
So, here's the actual question. Is there a suitable OT to run a quartet of 6V6's?
I've seen quartets of 6L6's, EL34's, EL84's and 6550's but never the 6V6's.
Was just wondering if there was iron made to match up with them.
Thanks in Advance!
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A push/pull OT made for a pair of 6L6s should be fine for a quad of 6V6s.
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at 300V, 4X 6V6 will draw 120 mA = 2500 OHM primary impedance
at 450V, 2 X 6L6 will draw 84 mA = 4900 OHM primary impedance
I would use a 2 X 6L6 tranny but I would double the speaker load to match the impedance. (8 ohm speaker hooked up to the 4 ohm tap ).
Colas
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Rake, you need to state a more complete design concept.
* Do you want PP or SE?
* Do you want lo plate voltage, say 250VDC, for earlier & smoother breakup; do you want to stay in Class A?
* Do you want hi plate voltage, say 360VDC or more, for more headroom & power output?
These choices will determine the primary impedance of the OT (which can be "played with" as Colas says on the secondary side). It will also determine the OT's current draw requirements. Do you want to under-spec the OT for early saturation, or not?
You need to spec-out the OT. If off-the-shelf is not suitable to your desires, Edcor can build you one.
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If it is push pull, I would use 2 Output Transformers. Actually this is my favorite amplifier configuration. You can use Deluxe Reverb OT's and get either 22 or 44 watts. If you put a loop in each, you can use one side with modualtion and the other side dry or out of phase FM modulation and create a beautiful real vibrato. I have attached a very nice one. Some of the components can be jfets, this is simply an old design. Now this is a real vibrato, not even like a Magnatone where some AM is present. Love the stereo Magnatone, not dissing it at all.
This soulds like a Doppler FM modulation, very leslie like.
Peronally, even a Deluxe is often too much to turn up to 6 at 22 wattts, so truthfully my design has Cathodyne PI, but does have a 12Ax7 after which have gain pots on the cathode to determine how much signal I want on the Output Tubes. Each side is 8K to 4 ohm, 15 watt Output Transfromers. One side I added 9 pin for either 4 6V6 or 2 6v6 and 2 El84. Cathode bias all the way. I use a Edcor 275-0-275 HT with 320ma, 6.3 4 amp, 5v at 3 amp. A little overkill on the amperage, but as they say, you can never be too thin or have too many amps. :laugh: I forget which rectifier I am using, but I can assure you the circuit doesn't load down much.
I did not use build in reverb since I now have a plate unit I prefer over spring. The reason I choose the gain up after the PI is to avoid overloading the preamp and getting a Tweed Deluxe or Princeton flabby tone and the Output Iron I used is large to be considered 15 watts, but it passes bass very well.
I have added a EF86 for a glassy type tone. You may think of this as an overdrive, but it is not clipping prior to the PI. There is not really any preamp distortion, I focused on a the strongest signal without clipping in the preamp. 10 db boost will distort the preamp, but I can still get a beautiful clean and add the slighest amount of modualtion for a very full tone. 3 inputs, one for humbuckers, one for Single coils and a third for hot Pups. This is to provide the same touch sensitivity, well sort of.
I have a 2, 12 cab I have been testing speakers for this i a cabinet I build from old reclaimed pine. One side has a old Greenback and the other has an old JBL. I build these cabs with a center board like old Bassman cabs, except I make them 2" deeper and bottom port. Not important. Just throwing out ideas.
I have not put this into a chassis yet as I am still working on the Vibrato I have posted here. I am wanting to build it on its own PCB, the Vibrato I mean. Need to reduce the size.
On full bore, I prefer all 6v6, but since I have yet to use it live, I do not know how well it works, but Currently I use a AC15 with EF86 for my dry and overdrive pedals and I used AC15 values on the EF86, but recently I made the Matchless setup switchable. I prefer the Vox values, but the Matchless values make the EF86 feel firm. This one drives a Celestion Blue. My second amp is Modded Princeton with 2 10's from an old Super Reverb, CTS horseshoe I believe these are called. I have been using Wet and Dry setups since 1983 and for me in a live situation this is by FAR the best. Complete tone and volume control and easy to get it to overdrive if you want.
Neither of these amps will make much over 10 clean watts and have no master volumes. If 20 total watts is not enough, simply shoot for Deluxe Reverb voltages or somewhere in-between.
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Ed, that's great stuff, but I suspect it's not what Rake wants to do. He didn't ask what you or I would do, but rather how to implement what he wants to do. Heck, if he asked what I would do: that would be to replace 6V6's with 6L6's. But that's beside the point, and the opposite of his desire.
Rake wants to build a 4X 6V6 amp and wants to know what OT to use. The quick & simple response has been provided by sluckey & Colas. But there are finer points if Rake wants to consider them which will effect tone: PP vs SE; voltage level & current handling. I'm trying to draw Rake out to discover more precisely what he wants to accomplish.
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Rake wants to build a 4X 6V6 amp and wants to know what OT to use.
He never indicated that. In fact he has never seen a 4x6v6 amp. I think he is simply curious so he asked a wide open general question.
The answer to his actual question is "yes". :icon_biggrin:
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Sluckey is right. It was more curiosity than anything else.
That said I always liked the "sound" of a Fender Deluxe over
Fender's 6L6 big brothers.
Just thinking what a Double Deluxe would sound like?
Ooh ooh, ooh ooh ooh, MORE POWER! :l2: :laugh: :icon_biggrin:
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Ed, that's great stuff, but I suspect it's not what Rake wants to do. He didn't ask what you or I would do, but rather how to implement what he wants to do. Heck, if he asked what I would do: that would be to replace 6V6's with 6L6's. But that's beside the point, and the opposite of his desire.
Rake wants to build a 4X 6V6 amp and wants to know what OT to use. The quick & simple response has been provided by sluckey & Colas. But there are finer points if Rake wants to consider them which will effect tone: PP vs SE; voltage level & current handling. I'm trying to draw Rake out to discover more precisely what he wants to accomplish.
True!
My overall point is there are many different ways. Desired clean wattage determined by either Push Pull, Single Ended and current and voltage. I believe I mentioned these factors.
What I misunderstood with Rake's question, is he prefers 6V6 tubes distorting, wanted to know if there was a Transformer for 4 them. I believe this could really get deep since no specific transformer is "made" for a Quad 6v6 amp, but the truth is no transformer is made specifically for 4 6550, however the vendor may suggest this. Well, unless you order them to build amps like Fender did. I would think you have ordered a specific winding, I know I do.
So the correct response is Rake, what would you like to build?
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Rake wants to build a 4X 6V6 amp and wants to know what OT to use.
He never indicated that. In fact he has never seen a 4x6v6 amp. I think he is simply curious so he asked a wide open general question.
The answer to his actual question is "yes". :icon_biggrin:
When Rake asked: "So, here's the actual question. Is there a suitable OT to run a quartet of 6V6's?" I took him to be asking a question about an actual build. Another fair inference gone awry!
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Rake wants to build a 4X 6V6 amp and wants to know what OT to use.
He never indicated that. In fact he has never seen a 4x6v6 amp. I think he is simply curious so he asked a wide open general question.
The answer to his actual question is "yes". :icon_biggrin:
When Rake asked: "So, here's the actual question. Is there a suitable OT to run a quartet of 6V6's?" I took him to be asking a question about an actual build. Another fair inference gone awry!
sorry Bro, it was just a question in general. Don't get me wrong, a "Double-Deluxe"
would be a great medium sized club amp!
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No problem! I think Toxophilite has a couple of threads on that general topic
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My 2cents would be to keep it simple - the sweet spot for a quad of 6V6's is 3.4-4K primary impedance with a 50W+ power rating.
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My 2cents would be to keep it simple - the sweet spot for a quad of 6V6's is 3.4-4K primary impedance with a 50W+ power rating.
Hey, that sounds like a good choice for a pair of 6L6s too. :wink:
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+1 on 6L6's - unless you've already got a chassis drilled for a quad I'd definitely go with a pair of 25-35W bottles - or upgrade your trannies and build a 100W monster!
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For me swapping 6L6's into a 6V6 amp (with some necessary circuit changes and maybe even a cooling fan!) makes the amp sound more robust. So I hotrodded my SF VibroChamp & SF Princeton (since sold) with 6L6's.
Anyway I can see the allure of a quad or more of smaller bottle power tubes. You get more SPL with less signal amplitude. Less signal amplitude means the signal retains its sine wave shape. That translates to less odd order & more even order harmonics -- for clean tone as well as for overdrive. That's a subjective tonal preference. YMMV.
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My 2cents would be to keep it simple - the sweet spot for a quad of 6V6's is 3.4-4K primary impedance with a 50W+ power rating.
Hey, that sounds like a good choice for a pair of 6L6s too. :wink:
I just couldn't let this go.
Guys, he's starting to fulfill his destiny as a troll. I think we need to add a sarcasm font.
dennyg, see: Reply #1
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Just thinking what a Double Deluxe would sound like?
Hold the cheese please...
https://www.tedweber.com/media/kits/5e3x2_schem.jpg
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Google made me read this:
http://www.vintageguitar.com/26793/jim-kelley-facs-reverb/
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I have an amp that is cathode biased and can run a quartet of 6v6’s, a pair of 6L6’s or even a pair of 6v6’s depending on which tube sockets are plugged into.
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65 amplifier co makes a 4 tube 6v6. Tone King, Carr and Divided by 13 and Jim Kelley make a 4, 6V6 amp. To me, there is a benefit in a 4 or even 6 tube push pull output as the seem to have more girth, the problem with 4 of most tubes is you cannot get them in the sweet sopt unless you are playing a huge place. Very huge or a Frat Party.
I am not a fan of preamp distortion, especially a 12AX7. 6V6GT, I do like as these are large enough to compress and sustain and not get fizz, but still have clean, poping clanging highs. I first built a 4, 6v6 and used a old Drake transformer from a 50 watt Marshall. 3.3k, multitap and ran the voltages up to about 420vdc on plates. Darn loud, too loud.
So I either had to screw with the tone by a VVR, master volume. Then the 2 OT idea came and cathode bias and running in class A. Now I simply have an amp that plays in push pull in just about any wattage you prefer, but nothing over 44 watts I woud think. The new Magnatone Twilighter is designed this way. It is a Double Deluxe with Stereo Maggie Vibrato.