6Ak6/6G6 info

[bigdaddy]

These tubes (6AK6/6G6)seem to be the gateway to making an amp that sounds like the bigger brothers. But they have to see NO more than 180v on both plates and screens. OK now were the heck am I going to get a PT that has that kind of voltages? Hammond has something close but can I knock down the extra voltage without really just ruining the sound? Does anybody know were I can get a power transformer that will give me about 200 volts? And have a tap for the heaters. I checked Edcor also and like Hammond they have something close but questionable.

Does anybody have experience with these tubes?

Someone made an amp using these tubes and ran the voltage off the end of the rail for the power tubes, after the preamp tubes. It got the voltage down, I never heard of this and that sounds like a bad idea.

But I really think this might be the way to go. Just a simple BF champ type amp but running one of these tubes. Or a pair in parallel.

I'm still going to work with the 12A_7 and possibly 6SN7 tubes but these seem to be the next step down from the 6V6 (12-14 watts)then the 6K6(8 watts) then it's the 6G6(3? watts max Plate dis.). The 6AK7 is the same as the 6G6 but fits into a mini 7 pin socket like the 6AV6 or 6AT6 preamp tubes which I have had good results with. I can see a SE amp with 2 6AV6's into a 6AK6.

[harryk]

  Hi Daddy! I am just preparing a bed room level tube amp with a pair of 6AK6 tubes. To my mind critical things are screen and plate dissipation which are some 2,7 W for plates and some 0,75 W for the screens. I am aiming to use a PT with 230 V windings, but will use a VVR to reduce maximum plate and screen voltage. You can use VVR also for that purpose + to reduce output power the same time. Shoot me a PM and your email address and I send you schematics of it. I wil have a modified marshallish preamp with rail voltage somewhere 300 V. Harry 

[zendragon63]

I don't know why I am up this late tonight man.   I kinda like the 6G6 and the 6AK6 and have build several small amps that I use for train gigs and for church. Still can get surprisingly loud depending on the speaker. Just a thought: a 150-0-150 with a half wave gets you to 210 and the tubes will bring it down around 200 and it runs pretty well for me that way. I have even run both tubes at 230V+ and they sound (IMHO) nothing short of that fantastic, strained, on-the-edge driven sound--but I wouldn't guarantee the service life. I also have run the power rail ass backwards and though it works, you may find what you suspect: that it doesn't sound 'right' since the preamp stages need some reasonable supply filtering or it is noiser than you might want to tolerate. YMMV though; hell I am still in tube amp grade school. Going via traditional rail, having only 120 or less on the preamp plates takes out of the BF zone but being that you have a ton of Champ experience and you tune it up, it might be just peachy.

Final thought for the evening/morning is to add up your filament draw and hope that a smaller PT can deliver it. (I always forget to run that number). I am interested in what others have found with the low power builds so I hope they chime in. Good luck on your project. Regards,

dennis

[Shrapnel]

BigDaddy,

Also, don't forget, if you can get the specs for a transformer they don't have listed, you can ask them directly. IF they don't have a design for one, they'll make one, as long as you pay a little extra, but once that's done, the design no longer has an extra fee on future purchases. (i.e. 120V pri, 5v@3A, 150v@120mA-DC 6.3VCT @ 3A, or whatever you need.) Edcor is also made in the USA. (New Mexico)

[ edit: company name spelling error, was Edcore, and IS now and should have been Edcor. ]

[bigdaddy]

I find that transformers made today are over built and exceed their specs. That's what drives me crazy, Hammond trannys always have more voltage, like their heater voltage is always 7+v not 6.3v. The trick is going to be keeping the preamp tubes at the correct plate voltage yet get 180v to the 6AK6 tubes. A permanent VVR might be the way.

I think Edcor has something for like $20 that might do the trick. Hammonds are more expensive but I have made some great sounding amps with them. Mercury Magnetics are wound from gold and platinum with diamond dust inside........ .......so forget anything from them.

I thought my amp days were over, but here we go again......this is tuff for me to do it kills my back, but I have no choice. I see some amps that might fit the bill but I am not paying $700 for a 2 watt amp!!!! The $179 for the Killer Ant was annoyingly overpriced. There's nothing in it and the lack of an adjustable tone stack kills it for me. I can get some descent tones from certain guitars but there's just no adjustments. the problem with the Ant is they don't drive the power section to save life on it and get all the distortion from preamp saturation. Once I build some things and get an idea it's going to be rebuilt the right way.

[HotBluePlates]

But they have to see NO more than 180v on both plates and screens. OK now were the heck am I going to get a PT that has that kind of voltages?

An isolation transformer, perhaps. 120v * 1.414 = ~170v. You simply use a bridge rectifier, a PT with 120:120, and a stiff cap-filter after the rectifier. Yeah, you need a filament transformer, but those can be found fairly cheaply.

The PT in question would have no center-tap on the secondary, which is why a bridge would be needed.

By the way, all of Hammond's transformers assume 115v on the primary. That's why their secondary voltages are often high.

[DummyLoad]

hammond 262Fx series - up to 140mA DC. as HBP says use w/ FWB recto. may or may not work... the fil winding looks pretty weak - or do as suggested - EDCOR custom or iso tranny with a seperate fil tranny.

btw, i'm sure you're aware that 6AK6 is good for up to 300V on plates; 250V g2 - perhaps something along the lines of the hammond 261M6 w/ FW tube recto would get you around 240V - likely something workable there for 1-2W output - i assume that's what your looking for...

another tube to look at is the 6CW5. it's another lower voltage tube. in P-P w/ 250V they can make 25W - not bad for a pair of T6.5 9 pin bottles. w/ 170V in SE you can make ~~5W. i built a variation of the SE plan on my breadboard a while back, fed w/ 6AU6 preamps - sounded nice for a smaller metal amp, but not what i was looking for. perhaps a single 5879/6267 would have been the ticket to paradise... :-\

http://frank.pocnet.net/sheets/093/6/6CW5.pdf

[bigdaddy]

I think I figured it out...

I'm going to run a simple BF Champ type amp that I have built already many times with variations. But I am going to use VVR to bring down the voltage for the 6AK6 power tube. it will be a fixed voltage, i won't be using the VVR in it's variable power scaling mode.

I think that simplifies the whole thing, Not having to do much other than install the VVR and new power tube/socket and figure out what's best in terms of filtering and driving the power tube. What I have driving a 6V6/6L6 might be too much. No need for a new or custom PT. if this works I can just modifiy the 20 or so amps I already built or some of them. Some will get a 6K6GT which is pretty loud and some might get a 12A_7/6SN7 tube......I will have to experiment with designs like the Firefly, 4-4-0 and some others I have come up with including a tweed Harvard but with different power tubes and maybe a Pentode for a preamp tube instead of the 6AT7.

[jojokeo]

Bdaddy, in my little "firecracker" amp, I can substitute a 12au7 for lowest output, 12bh7 for better tone w/ about a 1/2watt to 1watt of additional power, and a JJ ECC99 for the most power. Then you can experiment w/ all of the 12a_7s in the preamp stages. You could have enough options to occupy yourself w/ for weeks?
There's plenty of gain in that little amp and it's easy to add a tone stack of your choice if you really wanted. If you ever decide on this one, email me for a few suggestions which may save you some troubles.

As for small cheap trannies have you ever considered a torroid coil? This will get you what you need for a small set up w/ 6ak6s but for something like the Firefly better use the hammond 190-0-190 for tube substitions and get a 20k output tranny too. - http://www.antekinc.com/details.php?p=18

Here's a quick & easy p2p schem using that torroid for the PT to give you a few more possibilities. It has a more "normal" OT to use that the Firefly doesn't. I've come up w/ a number of various tubes to use in small powered amps but it comes down to availability & practicality too.

[bigdaddy]

Thanks JoJo.....

It's like so much information and I am trying to process everything. This is the time I fretted, not knowing the math.... .

I have been researching the 6AK6 and I think it's best operating voltage considering the amp designs would be in the 250 range not 180. So I think I have some tranny's I can use.

My isolation room worked GREAT!!!!!!! It's the closet in my bedroom. I used Styrofoam insulation 2 inches thick all around. and I made a huge 5 foot board to go in front since I had removed the door. The board has a mat on one side with mahogany strips 1 inch thick on the other, over the strips I put 3 pillows. It worked like a charm, it killed all the sound leakage but left me with a sound reminiscent of it's natural tone and punch. I just have to try some of my louder little Champs amps.

[jojokeo]

That design was just to show you about using the torroid is all and at 11 bucks for a PT that isn't too bad. There's many tubes you can use. I found some small Hammond PTs that would work for $20 @ 120v - $30 @ 250v last night depending on what your HT needs to be. LOL, gotta pay for that higher voltage.
Sounds like you have a big closet or no clothes? 
Glad things are working out for ya.

[bigdaddy]

I don't need clothes. I only go out to go to the doctor. I can't wear regular pants, the waist hits the nerves in my spine and the pain is unexplainable. So all I wear are tee shirts and jogging shorts or pants. I'm homebound because of spinal issues. I had to go to renew my license today, lucky for me they took me ahead of everybody because I use a walker. I would have never made it waiting on the lines.