OK I built an amp.
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IslandPink
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#48
Wow, nearly missed this thread ! it all came out so quickly .
I'm sure JC Morrison would be very impressed you are using the Eimac 3C24 as a shunt for the 6EM7 - very perverse !
Bet it sounds really good. Chris's 6EM7 at last Eggborough reminded me how good that valve sounds, but with shunt too , that would be tasty .
I'm sure JC Morrison would be very impressed you are using the Eimac 3C24 as a shunt for the 6EM7 - very perverse !
Bet it sounds really good. Chris's 6EM7 at last Eggborough reminded me how good that valve sounds, but with shunt too , that would be tasty .
"Once you find out ... the Circumstances ; then you can go out"
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Paul Barker
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#49
hi Mark, yes, these days a 6em7 amp is good enough. it's so easy to work with.
#50 no subject
nice to have you back paul
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Paul Barker
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IslandPink
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#52
Nice one !
Hey, when James moves to Harrogate, you're going to have one hell of a 'Yorkshire Audio Massive' up there .
Hey, when James moves to Harrogate, you're going to have one hell of a 'Yorkshire Audio Massive' up there .
"Once you find out ... the Circumstances ; then you can go out"
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Paul Barker
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#53
I changed a few things today
There are seen here two 150/C4 VR's and to the left of those an EZ80.
In the event the EZ80 connected one anode only biases the 6EM7 power section perfectly.
The further VR's are to shunt regulate the VA section. How could I not?
I made a dc supply for the Eimac shunt valve. It is not regulated I don'y have sufficient voltage on board to do so and I don't have hardly any small torroids any longer. I would need a 9 or 10volt ac filament demands 3 amps. Have plenty of 338T's but nothing for headroom over their volt drop. A refinement for another day.
This is the best 6em7 amp I have ever heard.
Anyone knows who has owned a good 6em7 amp that the imaging and soundstage far surpases those of a DHT. The qualities of depth and air are so nice after the mud of dht dullness.
There are seen here two 150/C4 VR's and to the left of those an EZ80.
In the event the EZ80 connected one anode only biases the 6EM7 power section perfectly.
The further VR's are to shunt regulate the VA section. How could I not?
I made a dc supply for the Eimac shunt valve. It is not regulated I don'y have sufficient voltage on board to do so and I don't have hardly any small torroids any longer. I would need a 9 or 10volt ac filament demands 3 amps. Have plenty of 338T's but nothing for headroom over their volt drop. A refinement for another day.
This is the best 6em7 amp I have ever heard.
Anyone knows who has owned a good 6em7 amp that the imaging and soundstage far surpases those of a DHT. The qualities of depth and air are so nice after the mud of dht dullness.
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Paul Barker
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#55
Yes I'll get it drawn.
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Paul Barker
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#56
One error in my anotations the first choke is 10h second is 5h otherwise critical inductance not achieved.
Last edited by Paul Barker on Fri Apr 22, 2011 10:10 pm, edited 2 times in total.
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Paul Barker
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#57
I have to go out will do clearer photo and voltages l8r
Done.
Done.
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Paul Barker
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#58
All chokes are snubbed with 0.1 microfarrad to ground from each end.
apart from the snubber there is no cap in front of the choke input choke. If you have too little voltage you can falsly raise it by trying different caps in front of the choke between -1 and 1 microfarrad. If your choke is of insufficient quality for choke input you may need to do this anyway or it will buzz.
The two positions with VR valves; the VR's are bypassed with 50ohm and 0.1 microfarrad series network, just across the VR and the pair of VR's as a whole.
The indirectly heated valves (includes EZ80) are all AC heated with one leg grounded you could refine that better.
If you can find Alan Bradly's or Tantalums verty good. I used what I had the Anode load 66k is made up of two in series (always a good idea anyway) RS old style carbon, the cathode resistor is made up of a combination of Alan Bradly. The power resistors are nothing special.
The DHT is DC heated but not regulated, you could better that.
It is very important not to bypass the first stage cathode resistor with a capacitor. If you do so it is your design.
The coupling cap is a necessary evil get a good one, 0.1 microfarrad would be ok.
The power supply is hopefully relatively invisible to the output stage, but significant to the VA stage. Obviously you can't buy a black gate today, use the best cap you can afford or polypropyline.
Don't compromise the power supply with capacitor input.
Don't use a solid state series pass regulator or it is a solid state amp. It is a SE amp in which the power supply plays the music with the output valve. If you want solid state amp build one, if you want valve amp leave solid state devices out of the power supply.
apart from the snubber there is no cap in front of the choke input choke. If you have too little voltage you can falsly raise it by trying different caps in front of the choke between -1 and 1 microfarrad. If your choke is of insufficient quality for choke input you may need to do this anyway or it will buzz.
The two positions with VR valves; the VR's are bypassed with 50ohm and 0.1 microfarrad series network, just across the VR and the pair of VR's as a whole.
The indirectly heated valves (includes EZ80) are all AC heated with one leg grounded you could refine that better.
If you can find Alan Bradly's or Tantalums verty good. I used what I had the Anode load 66k is made up of two in series (always a good idea anyway) RS old style carbon, the cathode resistor is made up of a combination of Alan Bradly. The power resistors are nothing special.
The DHT is DC heated but not regulated, you could better that.
It is very important not to bypass the first stage cathode resistor with a capacitor. If you do so it is your design.
The coupling cap is a necessary evil get a good one, 0.1 microfarrad would be ok.
The power supply is hopefully relatively invisible to the output stage, but significant to the VA stage. Obviously you can't buy a black gate today, use the best cap you can afford or polypropyline.
Don't compromise the power supply with capacitor input.
Don't use a solid state series pass regulator or it is a solid state amp. It is a SE amp in which the power supply plays the music with the output valve. If you want solid state amp build one, if you want valve amp leave solid state devices out of the power supply.
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Paul Barker
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#59
The whole object of the design is to try and blend my previous experience into the best mix under the circumstances, which entails compromises.
Yes it would have been nice to direct couple or transformer couple, but not at the expense of what I have been able to achieve by using a coupling cap.
In an SE amp the power supply is everything.
Lesson one I learned very early on choke input gives more and faster bass. end of.
Lesson two, valve rectification, it plays the music, play your music with solid state if you like, I prefer a valve.
Lesson three shunt regulate. It furthers the advantage of choke input and facicitates it aswell, by pulling sufficient current for choke input, no need for a current creating resistor.
This amp has no startup vagueries no clicks pops or whistles, it is stable from start to finish.
Yes it would have been nice to direct couple or transformer couple, but not at the expense of what I have been able to achieve by using a coupling cap.
In an SE amp the power supply is everything.
Lesson one I learned very early on choke input gives more and faster bass. end of.
Lesson two, valve rectification, it plays the music, play your music with solid state if you like, I prefer a valve.
Lesson three shunt regulate. It furthers the advantage of choke input and facicitates it aswell, by pulling sufficient current for choke input, no need for a current creating resistor.
This amp has no startup vagueries no clicks pops or whistles, it is stable from start to finish.
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Mike H
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#60
Yes I can see that. And pulls the current that the o/p stage(s) isn't. When it/they isn't.Paul Barker wrote:Lesson three shunt regulate. It furthers the advantage of choke input and facicitates it aswell, by pulling sufficient current for choke input, no need for a current creating resistor.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."