Discussion in 'Building the Classics' started by RickyLee, Jan 15, 2018.
There is a difference to the sound of each.
Yeah, was thinking about something along the lines of having something to do to keep busy and maybe a bit of income for when I retire as well.
I will keep you guys posted. I am thinking I am going to go with that Classic Tone for now. Might have to wait till end of month to put my order in for the transformers.
Sounds good. What model output transformer is that and what power tube(s)?
russian 6p1p 10w musical power supply on ebay , it has a marshall jcm 800 style pre amp circuit. I have not played it in a a while .
I also have a epiphone valve jr that I modified , it's pretty good but those little 5w amps are fairly loud in a small room.
Not trying to highjack the thread...but i thought I'd share and see If anyone has objections. ..and offering a place to start. .
Since my moost current rig is a floor based 2203 preamp that i run into whatever power amp/speaker available, i could use a small power amp for home playing...and as stated earlier. .now i need to know...
Here is a tiny poweramp i drew up. Fixed bias. Fender reverb transformer. Adjustable nfb, a watt or two. 12ax7 input, 12at7 output tube.
Elevated ground for output cathodes, for easy bias arrangement
What do you think?
Looks interesting! I've never used dual triodes as output tubes before so I don't know much about such circuits.
I was originally thinking a Champ like circuit (6V6) but with fixed bias. Pleximaster has been working on something like this and he put a switch in the circuit so he can switch between fixed and cathode bias. Take a look:
I have no experience with those low watt triode power stages. But it looks interesting for sure. I have two output xfmrs on this project I am messing with now. The small OT is running two EL84's push pull cathode bias. I might just have to try out your circuit later on this one . . . .
Cool. Please note thought that most leds are specified. Max 30mA of somewhere near that. So two 12at7 is about the limit of what they can take, using it as elevated ground.
If you use a more powerful tube, you'll need something else, and probably higher voltage drop..
I have to add something with regards to single ended amps:
One of my favorite amp is Fargen mini plex. It's a 12W SE amp with dual el34.
I've really want to try build something with that kind of stage. I've been constantly thinking of this since you started this thread
Thank you for that
The output Transmformer is a Musical Power Supply
OT10SE USA on eBay. USA made.
This is good for the 6P1P russian tube in the schematic.
5K primairy for a parrallel 12AT7 @ 300V?
If it is dual El34 they are running Parralell I believe. From a guy on his page dvnator chasing tone.com
Power transformer for a 120V, 60Hz. line to 290V at 250mA and 6.3V (3.15-0-3.15) at 4A center tapped
EL34 has a good current draw hence 250mA
Did you get that B+ up to 680 Volts yet?
Edcor is cool, because they will build you anything just about.
My next project will be a Circlotron, which I always wanted to try for guitar amps.
(the primary of the OT is cathode driven) The CT of the OT primary is ground.
And I will need the special transformer, which I think Edcor will wind.
Did you know that a Circlotron requires 5 separate power supplies?
That's where you get an Edcor PT built.
Never heard of the Circlotron. What type of sound do you get out of that power amp compared to a Marshall 2204 type?
Was your question of me getting 680V B+ a typo? Was wondering what you were referring to there?
I have not ordered my transformers yet. I am messing with a project that was a Princeton Reverb type circuit that I converted to a 2204 preamp into a cathodyne phase inverter. I am using 56K/56K for the plate and cathode on that cothodyne PI. Not too impressed with it at his point.
Well. My test build is coming together. Not pretty in any way. Just a lot of reused parts. And not safe outside my mancave.. .underfiltered.so Some hum and a little intermodulation. But it works..have to wait a few hours to see how it distorts. .that's after all why i did this. .only change from schematic above is the LEDs are replaced with a string of 6 1n4841. They are good for 500mA. But only drops~0.7volt. B+ is 280 volt. Bias set to -3 volt against cathode for 10mA/ side. From darasheet curves. Will check with oscilloscope when i get a chance
ok, danfrank was right...fixed bias makes single ended behave and sound much more like push/pull. at least the one above. ...I guess I have to call it "BigBoy"
NFB at halfway, clipping start occuring at 200mV input.
i changed the bias to just four 1N4148( it gave 2,96volt) and grid resistor straight to ground.
being just a power amp, the sound is rather flat and boring, pushed with boss GE7, with the mids scoped, gave a very convincing fender amp type sound. I'm sure I can use it for home practice with my floor preamp. I did forget to measure output power, but I'm guessing around 0,5watt. run into overdrive, it was plenty loud for a small mancave but still tollerable for the family watching TV upstairs..my Marshall 1watt DSL is louder...fun little experiment/project...now what...
A circlotron (not cyclotron) has never been tried with a guitar amp. (as far as I know)
We don't know the results.
But what we are doing here, is to develop a new signature sound, which is a departure from what everybody else is doing.
680 volts is what I imagined for a single ended amp, that is loud enough to go head to head with a push pull amp.
Single ended is much less efficient compared to push pull. Probably: less than 1/2 as efficient.
you think of wattage as being a measuring stick that determines "how loud" and amplifier is...
But what I have said many times is: that's not an effective way to judge loudness.
It's more of: what speakers?
It's more of: what distortion?
It's more of: compression?
It's more of: power supply voltage.
that really makes an amp loud(er).
There are or were OTL's but I do not know of any used for musical amplification. You usually have to have a shit load of output tubes to get the output impedance low.
$20+ at 8, 12 or 16 tubes is expensive especially if you burn them up regularly.
200mV signal was going into the input of the power amp? Would be equivalent to having 200mV audio signal going into the 22nF cap of a Marshall phase splitter input? The 22nF cap between tone stack and phase splitter? That is not much signal at all. My bridge humbucker hits peaks of well over 500mV.
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