I decided to open this discussion 'cause I saw some strange/interessant schematics in "elettronica flash", an italian magazine.
The "valvolozzo" is a SE amp with torroid output transformers, by Diego Barone.
He uses normal torroids(220V-12V 100VA for EL34 and 8ohm, 220V-9V 100VA for 4ohm) and a cap and a choke for eliminate DC.
ECC82 as driver, with a configuration which introduce a distortion so that can be added with the final distortion to attenuate it.
The power tube is EL34.
There is also a mosfet for 3 pouprose:
1)filtering better the supply
2)driving EL34 with low impedance
3)force the ECC82 to work in a load exclusively made by R7-R8
The schematic:
You can see a distortion of 2% in the graphics of his web page:
Barone
What do you think about? 😀
The "valvolozzo" is a SE amp with torroid output transformers, by Diego Barone.
He uses normal torroids(220V-12V 100VA for EL34 and 8ohm, 220V-9V 100VA for 4ohm) and a cap and a choke for eliminate DC.
ECC82 as driver, with a configuration which introduce a distortion so that can be added with the final distortion to attenuate it.
The power tube is EL34.
There is also a mosfet for 3 pouprose:
1)filtering better the supply
2)driving EL34 with low impedance
3)force the ECC82 to work in a load exclusively made by R7-R8
The schematic:
An externally hosted image should be here but it was not working when we last tested it.
You can see a distortion of 2% in the graphics of his web page:
Barone
What do you think about? 😀
Sorry I can't read Italian. I believe you can use any AC power transformer as the output matching transformer. The problem is whether it has flat and wide frequency response.
Johnny
Johnny
Konnichiwa,
Well, the Amplifier is pretty generic parallel feed. The use of mall toroidal mains transformers as parallel feed outputs or PP Outputs is hardly new, these transformers clearly are a compromise solution and regardless of nominal power level (core) only suitable for low powers. Thypically a 1:4 to 1:8 derating is neccesary for audio service, so a 230V RMS primary really should not be pushed past 75-115V AC for audio service.
Also, for a parallel feed output transformers mains torroids often have rather low inductance, leading to a very large required coupling capacitor. Further, the anode load choke chosen is rather too low in value for good LF performance.
The frontend is a Kimmel mu Follower, but with the addition of a load on the lower valve to make it distort more than neccesary. This cancels some 2nd harmonic of the output stage and increases the 3rd harmonic level, thus making the amplifier measure better, but sound subjectively actually more distorted than without cancellation.
This kind of thing is nice for experiments in cheap audio, but ultimatly the quality available is limited. So by all means build one if it must be cheap to make more than anything else.
Sayonara
TheGatesOfFate said:
Well, the Amplifier is pretty generic parallel feed. The use of mall toroidal mains transformers as parallel feed outputs or PP Outputs is hardly new, these transformers clearly are a compromise solution and regardless of nominal power level (core) only suitable for low powers. Thypically a 1:4 to 1:8 derating is neccesary for audio service, so a 230V RMS primary really should not be pushed past 75-115V AC for audio service.
Also, for a parallel feed output transformers mains torroids often have rather low inductance, leading to a very large required coupling capacitor. Further, the anode load choke chosen is rather too low in value for good LF performance.
The frontend is a Kimmel mu Follower, but with the addition of a load on the lower valve to make it distort more than neccesary. This cancels some 2nd harmonic of the output stage and increases the 3rd harmonic level, thus making the amplifier measure better, but sound subjectively actually more distorted than without cancellation.
This kind of thing is nice for experiments in cheap audio, but ultimatly the quality available is limited. So by all means build one if it must be cheap to make more than anything else.
Sayonara
JOKE?????Re: Re: The "Valvolozzo" - SE amp with torroids
Yes I know,
Barone in his web-site tells about a cheap amp for cheap experiments...
Also the other projects are in strange philosophy.
The "ibrid" with IGBT:
or the 2A3 SE with mosfet(and 1% thd):
and many suggestions for plasma tweeter.
😉
Kuei Yang Wang said:
Yes I know,
Barone in his web-site tells about a cheap amp for cheap experiments...
Also the other projects are in strange philosophy.
The "ibrid" with IGBT:
An externally hosted image should be here but it was not working when we last tested it.
or the 2A3 SE with mosfet(and 1% thd):
An externally hosted image should be here but it was not working when we last tested it.
and many suggestions for plasma tweeter.
😉
I used one in a parafeed preamp, and it was surprisingly good. When I went to push-pull, it lacked sufficient inductance. I still use one as phase splitter at the input, and it seems to work fine.
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