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64.12.116.16
hey-Hey!!!,
I am contemplating a small amp for the kitchen. Likely speakers will be something comparable to a Minimus 7. No need for lots of power, and size and simplicity are quite important. PP topology. Nutsy unuseable tubes. No linestage. Signal from small CD player.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
I been wanting to make this amp for a while. PPP 6AQ5 triode connected for about 5-6 watts out or quite low distortion 3-4 watts out. Use a E80CC as cathodyne splitter with other section as preamp in direct coupled configuration. I found on the internet a test that resulted in the E80CC producing lower distortion than 6SN7s. Amperex E80CC is warmer, Tungsram E80CC are more neutral and crystal clear. Both are so good, my mood & desired music makes the choice of the better tube that day.
No one has perform a comparison of the best sounding 6AQ5s either in the archives. Seeing that 6AQ5 are plentiful & rather inexpensive, tube rolling will not be a budget killer either.
Then, change the E80CC to twin tail splitter & add one section per channel of your favorite preamp tube. The load of PPP triode connected 6AQ5 grids are a factor as you knpw.
Couldn't pass this up:
A 6922 will do 1.5 watts in P-P class B1. See the Philips E88CC data sheet. CD player drive into a step-up phase splitting transformer (or autoformer/CT choke) should not need any driver at all. 10K output transformer readily available.
one tube PP...
I need to build a tiny amp for the bedside table... and as easy a a 6em7 would be, I just want to do something a little more off the beaten path... I wish I had one of those old Speed tubes (295?) that is a 56 internally direct coupled to a 45.. one big beautiful globe.... that would be a no-brainer.. :^)
maybe a 35t spud? power supply just kills you, though... but... I might be able to hide the PS under the table... hmmmm.. I kinda like this idea...
Peace,
Me
hey-Hey!!!,
Make sure you use 35R rectifiers in order to keep the tube inventory down.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
-----10K output transformer readily available.
Yes they are...'bout $150 each for a real nice one...:)
While the 6DJ8 amp sounds neat, I think I'll put that one in the 'maybe' pile for now. In that same vein, a trioded, high-gm pentode could also be pressed into service.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
That sounds like fun! Could you still call it a spud?
How about the 2E30 with your usual e-linear pentode driver ? It's a 7 pin DH beam tetrode , similar to a 6AQ5 . The only caveat is that it has a fast heating filament , from my experience these tend to lose emission a lot faster than usual . The things are cheap and available , may be worth a try and if no good , stuff in some A2134 , N78 or 6AQ5 instead ;)
My other suggestion would be push pull 6AH4 but I know you're really into triodes
Al
Push-pull compactron tubes, you can have 2 bottles per channel. Or something more mundane, like 6BM8. Maybe a PP 6AQ5 variant (el cheapo variant?) would fit on a small footprint.
Dearest Doug, Please build this and then convince me that the $1500
in parts I spent to build Amity's would have been better spent on
bl*tt*r ac*d and Greatful Dead tickets.
The UTC A-12 only has a 500V Hipot test; not sufficient for line isolation :-(
Just break the ground connection at the input and output transformers then it is safe. Since it has no feedback loop the OPT does not need to have a secondary ground.
See Tom's post below. I looked too fast and didn't see that the AC plug was three wire with the safety ground only tied to the IPT and OPT
or is that anathema for some reason I don't understand...?
all the best,
mrh
The chassis, input, and output are isolated from the power line, and chassis is at safety ground. The input and output transformers SHOULD provide adequate insulation, though I think I'd hipot test it ( > 1000V line-chassis) before I call it safe...
hey-Hey!!!,
Now if we could only do away wid the chokes...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
6BX7 with CT'd choke phase inverter using driver du jour to meet your gain needs, barely, without much need for attenuation, so perhaps a 6J5 or similar.
P
hey-Hey!!!,
I think something between 3 and 10W will do just fine for this amp. If power is easy, having more of it is no liability.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Build a Machine. It's a ridiculously simple circuit. You will not get any better sound no matter what. You want it compact, build it in one of Chung's boxes.
Aloha,
Poinz
AudioTropic
Poinz, please take no offense at this response; take it with the greatest respect...if I wanted a Machine I'd just buy one. I'd rather make something with a tube compliment that is at biggest risk of extinction due to lack of application. IME such tubes are able to eclipse the performance of the usual audio suspects when their strengths are played to.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
The 6GK5 isn't unusual enough for ya? Use 6Y6, or one of the other similar-to-6V6-EL84 orphans for outputs. Isn't there one with two top caps? Watch kittie backflip through the window!
P
hey-Hey!!!,
That 6GK5 is a neat one. Matter of fact, if I didn't have some very nice Russian 6S3 I'd probably pony up and buy a few pairs offa you. The ones like 33GY7 give me a very nice set of parallel rectifiers and a triode-able pentode to work with.
cheers,
Dogulas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Doug,
Comparative unknowns in the 6V6 family include the 14C5 and 12AB5. Brimar made 6CH6/EL821s should not be especially costly. With a greater sensitivity than either the EL84 or 6V6, you should get enough gain to drive EL821s with 6J6s that are buffered by ZVN0845A source followers.
That's pretty cheap tubes and pretty cheap "sand". ;> D
Eli D.
hey-Hey!!!,
One of the more interesting ideas is an E-Linear, cascode sand amp. No heater power...little, and most importantly pentode-constant gate capacitance. I have some sublime 5k a-a outputs to use...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Hi Douglas,
Instead of concentrating on the tubes etc, why not do something quite different and concentrate on the container. I have this vision of an old Ford roadster with tubes as the headlights and the steering wheel as the volume control.
Of course, I could suggest that you go completely over to the dark side and do an SE amp, but your kitchen would then need to be exorcised, if not the whole house.
By the way, I still have the stone your son gave me in my car. It goes with me everywhere.
ray
I am unaware of the Maximus 7 efficiency, but the simple 12AX7 driving a pentode connected 6BQ5 in SE outperforms any PP small wattage amp I ever heard. Brimar 12AX7, 2x Sylvania 6BQ5 black plate & a Mullard EZ81. I like 350 volts plate, 260 volts screen and -9 volts cathode bias.
you know much more than I do but what about a PP 12B4A? It would be cute?
Maybe you could get away with PSE and a fet follower instead of an output transformer. It is, after all, a kitchen amp, and not having to shell out for OT's would be nice.
A PP amp with 6EM7's or 13EM7's - 10K/8 ohm PP transformer.
I am guessing about 3 watts (RMS) TRIODE power.
my fault below. I took your message the wrong way.
hey-Hey!!!,
I was considering something like that...
33GY7 with its pentode section triode-strapped, its damper diodes for rectifiers and a LTP 6S3Pi for the input stage. Does its job open loop too.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Would you make a bridge with the 4 diodes, or put pairs of them in parallel?
hey-Hey!!!,
They'd go in parallel. No sense getting nutty, and the heater-cathode rating isn't the same in both directions.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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