Well, took a little more than an hour, but its up and running. Listening to Turbonegro at severely loud level! It sounds great
I cant find the ECC86 so had to use 6922. Running it at anode voltage of 18volts Hilarious, but it works. With an ecc86 this can be promising.
It is extremely 2nd harmonic, but the higher orders are less than 40dB, not bad considering the low voltage and simple circuit.
Ps. at this low voltage the 6922 draws grid current so it must be AC coupled.
I cant find the ECC86 so had to use 6922. Running it at anode voltage of 18volts Hilarious, but it works. With an ecc86 this can be promising.It is extremely 2nd harmonic, but the higher orders are less than 40dB, not bad considering the low voltage and simple circuit.
Ps. at this low voltage the 6922 draws grid current so it must be AC coupled.
Attachments
Wow!
The analisys seem ok, but as you said, with an ecc86 the resuslts must be better, as, unlike what is common saying, the ecc86 is not a low voltage ecc88 (just look at the curves for it), but a real space-charge triode.
Can't wait to get the electronics store with it's doors open tomorrow
BTW, what PSu do you recommend? Is the 100Hz hum audible?
Good hollyday
The analisys seem ok, but as you said, with an ecc86 the resuslts must be better, as, unlike what is common saying, the ecc86 is not a low voltage ecc88 (just look at the curves for it), but a real space-charge triode.
Can't wait to get the electronics store with it's doors open tomorrow
BTW, what PSu do you recommend? Is the 100Hz hum audible?
Good hollyday
Yes the psu hum is audible in this hastily built amp. See the fft picture and you clearly see the psu harmonics. The PSU has to handle the constant current draw of this classA circuit, but since we're talking a rather low power amp it wont have to be in the kVA range. You need minimum 75VA per channel but expect some sag at that rating. The larger the more stiff the supply but no need to go overboard. I used a 300VA 18VAC tranny and 24000microfarads (which ripple wise isnt enough without active filtering or tricks like injecting some psu noise into the circuit to cancel it out). But I dont mind the noise since I always listen to music loud You could always try and filter the supply to the tube a little better than what I did last nite. The MOSFET draws an amp or so and its supply is hard to get ripple free.
You could always try and filter the supply to the tube a little better than what I did last nite. The MOSFET draws an amp or so and its supply is hard to get ripple free.I think i found it...
When i was shoping for the components (though i only managed to get 39R 17W resistors to parallel for the source) i saw a nice universal notebook SMPSU rated at 24V/3A, or any other lower voltage at 3,5A for 35€.
Doesn't seem bad, at least it's probably cheaper than buying 3A diodes, a transformers and the full stock of electrolytics (or 2 12V car batteries )
When i was shoping for the components (though i only managed to get 39R 17W resistors to parallel for the source) i saw a nice universal notebook SMPSU rated at 24V/3A, or any other lower voltage at 3,5A for 35€.
Doesn't seem bad, at least it's probably cheaper than buying 3A diodes, a transformers and the full stock of electrolytics (or 2 12V car batteries
)
If you replace the source resistor with a 100mH DC choke you will increase the maximum efficiency from 25% to 50% and also be able to swing the load below ground. I have a 40+40W Class A amp that uses a single 27.7 volt rail with 3.5 amps current per channel and it goes very well. Many of the old timers here have seen it a million times by now, but I hope you can find something useful in it. Here is the development story --> Click
)You won't believe it, but...it's still sitting on the work bench, half completed 
All it needs is to solder the valve base in place ,and put the volume pot (i don't know why, but to me, soldering the vol pot is the most tedious job in every amp for me!)
But i've been thinking about it for a couple of days now, and will probably finish it this week (i hope).
Sorry if i didn't get it, but what do you mean with this phrase?
And yes, i'm a real simpleton, getting worse by the day...(really)
All it needs is to solder the valve base in place ,and put the volume pot (i don't know why, but to me, soldering the vol pot is the most tedious job in every amp for me!)But i've been thinking about it for a couple of days now, and will probably finish it this week (i hope).
Sorry if i didn't get it, but what do you mean with this phrase?
And yes, i'm a real simpleton, getting worse by the day...(really)
I mean
There are MOSFET Power transistors
and NON-mos
and it is almost impossible to build 1 T power amp
without using MOSFET
At least input impedance will not be as low
(same as saying: it takes more current to drive the input of a BJT Bipolar,
than it takes to drive a MOSFET with same power output)
this is maybe one reason Nelson Pass
later went for MOSFETs in almost all his amplifiers
Tubes like to drive a bit higher impedances.
There is a limit to how much output current
valves would like to handle.
There are MOSFET Power transistors
and NON-mos
and it is almost impossible to build 1 T power amp
without using MOSFET
At least input impedance will not be as low
(same as saying: it takes more current to drive the input of a BJT Bipolar,
than it takes to drive a MOSFET with same power output)
this is maybe one reason Nelson Pass
later went for MOSFETs in almost all his amplifiers
Tubes like to drive a bit higher impedances.
There is a limit to how much output current
valves would like to handle.
A link to photos
Here are the photos of the finished amp. Listening impressions later this week.
Link:
http://www.diyaudio.com/forums/showthread.php?postid=998866#post998866
Here are the photos of the finished amp. Listening impressions later this week.
Link:
http://www.diyaudio.com/forums/showthread.php?postid=998866#post998866
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