waltube said:
Indeed it is!
So folks, show us your "Italian Job" amplifier at the Bottom Audio happening/contest that will be held in Monterubbiano (Fermo) May the 1st 2009.
Details here:
http://www.diyaudio.com/forums/showthread.php?threadid=132910
We're open to people from any continent, of course. All will like the place for sure. Walter, Andrea make me a call or drop me a message.
Meet You there.
This evening the first test using the GM70 Graphite like diode in the configuration of the attached image.
Tested on my 845 two stage ampl.
1000v without the GM70
940v with the GM70 like diode
Until now I don't see problems.
I remember this:
http://www.audiodesignguide.com/Cla...S_solutions.png
Anode and Grid connected to solid state diodes.
Tested on my 845 two stage ampl.
1000v without the GM70
940v with the GM70 like diode
Until now I don't see problems.
I remember this:
http://www.audiodesignguide.com/Cla...S_solutions.png
Anode and Grid connected to solid state diodes.
Attachments
Hi,
I post some graphics from tests I made time ago with NC20interstage trafo.
This mainly to show the great problem is possible to mee mainly at low frequencies.
I suggest , if someone would to use stuff similar to that, to implement a good test set to trim the best technical solution in function of anode current.
The NC20 has rdc of 430 ohm (primary and secondary).
1) With a 6BX7, one section, common anode,Vdc=330 Vdc I got:
3% ad 1KHz
Ia=20mA 130Vrms out
Ia=30mA 140Vrms out
Ia=40ma 145Vrms out
This just to show the different Vout respect to Ia.
But I f I move to low frequencies:
Vin 5V
20Hz
Ia=20mA Vout=40V thd 1,9%
Ia=30mA Vout=40V thd 12%
same Vin but 1KHz:
Ia=20mA Vout=41v thd 1%
Ia=30mA Vout=43V thd 1%
Again:
- http://www.multitask.it/845/1403-20hz-20mA-5vin.jpg
this is a spectrum for Ia=20mA and 5 Vin, 20 Hz
- http://www.multitask.it/845/1403-20hz-30mA-5vin.jpg
same as above but Ia=30mA
-http://www.multitask.it/845/1403-1Khz-20mA-5vin-nc20.jpg
this is 1Khz Ia=20mA, good.
- http://www.multitask.it/845/1403-1Khz-50mA-nc20.jpg
Ia=50mA, the result is also good
Different schematic, a 6BX7 in totem with 630 vdc, Ia=14mA, the results are:
Vout p-p=342 V p-p con 3% equal to 120 Vrms (with a load of 10 Kohm; Rout=500ohm; G= about 8
The results are non so bad.
Test with 6H30 and NC20.
Va=250 Vdc, Ia=15mA
1 KHz
Vout=185Vrms con Vin=12.5 Vrms G=14.8
thd=3%
20 Hz
Vout= 155 Vms con Vin=11 Vrms
thd=3%
(1 Khz thd=1,1%)
- Va=250Vdc Ia=15mA
1KHz Vout=40 Vrms thd=0,3%
20Hz Vout=40Vrms thd=0,8%
Good.
- http://www.multitask.it/845/1903-6H30-1KHz-40Vout-15mA.jpg
6H30 with NC20 at Ia=15mA and Vout=40 Vrms
-http://www.multitask.it/845/1903-6H30-20Hz-40Vout-15mA.jpg
same as above but at 20 hz.
I hope this can help.
Ciao
Walter
I post some graphics from tests I made time ago with NC20interstage trafo.
This mainly to show the great problem is possible to mee mainly at low frequencies.
I suggest , if someone would to use stuff similar to that, to implement a good test set to trim the best technical solution in function of anode current.
The NC20 has rdc of 430 ohm (primary and secondary).
1) With a 6BX7, one section, common anode,Vdc=330 Vdc I got:
3% ad 1KHz
Ia=20mA 130Vrms out
Ia=30mA 140Vrms out
Ia=40ma 145Vrms out
This just to show the different Vout respect to Ia.
But I f I move to low frequencies:
Vin 5V
20Hz
Ia=20mA Vout=40V thd 1,9%
Ia=30mA Vout=40V thd 12%
same Vin but 1KHz:
Ia=20mA Vout=41v thd 1%
Ia=30mA Vout=43V thd 1%
Again:
- http://www.multitask.it/845/1403-20hz-20mA-5vin.jpg
this is a spectrum for Ia=20mA and 5 Vin, 20 Hz
- http://www.multitask.it/845/1403-20hz-30mA-5vin.jpg
same as above but Ia=30mA
-http://www.multitask.it/845/1403-1Khz-20mA-5vin-nc20.jpg
this is 1Khz Ia=20mA, good.
- http://www.multitask.it/845/1403-1Khz-50mA-nc20.jpg
Ia=50mA, the result is also good
Different schematic, a 6BX7 in totem with 630 vdc, Ia=14mA, the results are:
Vout p-p=342 V p-p con 3% equal to 120 Vrms (with a load of 10 Kohm; Rout=500ohm; G= about 8
The results are non so bad.
Test with 6H30 and NC20.
Va=250 Vdc, Ia=15mA
1 KHz
Vout=185Vrms con Vin=12.5 Vrms G=14.8
thd=3%
20 Hz
Vout= 155 Vms con Vin=11 Vrms
thd=3%
(1 Khz thd=1,1%)
- Va=250Vdc Ia=15mA
1KHz Vout=40 Vrms thd=0,3%
20Hz Vout=40Vrms thd=0,8%
Good.
- http://www.multitask.it/845/1903-6H30-1KHz-40Vout-15mA.jpg
6H30 with NC20 at Ia=15mA and Vout=40 Vrms
-http://www.multitask.it/845/1903-6H30-20Hz-40Vout-15mA.jpg
same as above but at 20 hz.
I hope this can help.
Ciao
Walter
audiodesign said:
mmmh... why not using an "hybrid bridge" (SS diodes on one half of the bridge + 2 VT diodes on the other half) instead?
AFAICT, that should give better results (e.g. less rectification noise), though at the price of one more VT.
Since I'm here, another question: why "wasting" a triode to do the job of a diode instead of just using a plain VT diode? I'd bet the Russians had some plain VT diode similar to a "diode strapped GM70" among their vast VT production...
ahem... broken link. Could you fix it, please? Tnx.
This evening the first test using the 6D22S like diode in the configuration as previous PS design with GM70.
1000v without the 6D22S
972v with the 6D22S like diode without output resistors
Until now I don't see problems, probably I will add an output resistor to reduce current peaks
Why use 2 tubes instead of 1 ?
1000v without the 6D22S
972v with the 6D22S like diode without output resistors
Until now I don't see problems, probably I will add an output resistor to reduce current peaks
Why use 2 tubes instead of 1 ?
mmmh... maybe.
I'm not sure about the switching noise of the SS diodes, particularly in the 3rd circuit.
IMVHO, "by heart" (educated guess) I would say that (at least noise-wise) the "=" signs should be in fact "~=" (almost equal), with the 3rd circuit being quite less similar to the first than the 2nd.
Hint: during switching transients, SS diodes are not so much "one-way" devices... they may have quite a bit of stored charge... if each SS diode is connected to a VT one (2nd circuit), the VT diodes should prevent any "strange" fast switching transient within the bridge. Obviously the same will not hold true if you have a full SS bridge before a VT used as a "dynamic resistor" of sort... (though adding small caps and/or snubbers you may effectively clean it up).
BTW: for sure, if you want to get close to a (fully) VT rectifier, you'll want to use only Shottky barrier type SS diodes in either the 2nd or the 3rd circuit...
new info again
http://www.audiodesignguide.com/Claudio845/GM70amp.html
soon the complete listen test
http://www.audiodesignguide.com/Claudio845/GM70amp.html
soon the complete listen test
This last saturday Mr. Bartolucci was in my house.
We hava compared the sound of the all Tango solution to the all Bartolucci set in the GM70 amplifier.
All the persons present have considered the Bartolucci result better than Tango.
We have also compared the sound of the my 2 stage GM70 to the amplifier used by Bartolucci in the last Hi-end meeting in Milano (Italy)
http://nuke.nonsoloaudiofili.com/Po...009 B/175.jpg
This is a 3 stage amplifier using the 2A3 to drive the GM70 and separated vacuum tube power supply per each channel.
The my 2 stage has been considered better for many factors.
We hava compared the sound of the all Tango solution to the all Bartolucci set in the GM70 amplifier.
All the persons present have considered the Bartolucci result better than Tango.
We have also compared the sound of the my 2 stage GM70 to the amplifier used by Bartolucci in the last Hi-end meeting in Milano (Italy)
http://nuke.nonsoloaudiofili.com/Po...009 B/175.jpg
This is a 3 stage amplifier using the 2A3 to drive the GM70 and separated vacuum tube power supply per each channel.
The my 2 stage has been considered better for many factors.
Result of a new listen test with some my friends with lot of experience in music reproduction and live events
-----------------------------------------------------------------------------
The 813 RCA is much better than GM70.
If you ear the 813 RCA it is impossible come back to GM70.
Using the 813 all the instruments are very natural.
The voltage gain is a little bit lower using the 813.
-----------------------------------------------------------------------------
The 813 RCA is much better than GM70.
If you ear the 813 RCA it is impossible come back to GM70.
Using the 813 all the instruments are very natural.
The voltage gain is a little bit lower using the 813.
Adrea, nice to hear that you like the 813.
But i can recommend the chinese shuguang FU13 ribbed plate. This tube is in my opinion the best sounding 813. This is not only my opinion but also 20 other 813 users have maken the same conclusion after testing RCA, GE and two Shuguang versions of the 813 Tubes. You can read about it on the german roehren und hoeren forum.
Further we did some test with different bias adjustments, from 50 untill 90 mA. And there the most favourit was 55 mA. So you see there is still a lot to explore on the 813 tubes.
Ronny
But i can recommend the chinese shuguang FU13 ribbed plate. This tube is in my opinion the best sounding 813. This is not only my opinion but also 20 other 813 users have maken the same conclusion after testing RCA, GE and two Shuguang versions of the 813 Tubes. You can read about it on the german roehren und hoeren forum.
Further we did some test with different bias adjustments, from 50 untill 90 mA. And there the most favourit was 55 mA. So you see there is still a lot to explore on the 813 tubes.
Ronny
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