Hello,
I want to build amplifiers for mid & high frequency for my Linkwitz Orions. They are active speakers with an external line level crossover. The tweeter and midrange drivers are
Seas T25CF002 THE ART OF SOUND PERFECTION BY SEAS - E0011-06 T25CF002
and Seas W22EX001
THE ART OF SOUND PERFECTION BY SEAS - E0022-08S W22EX001
The sensitivity is 87-88 Db/1Wat so I will need all power that can be obtained from the output tube. The crossover points are 120 Hz & 1440 Hz. The crossover is Linkwitz-Riley 4th order. I want the amp driving the midrange to be a full range so I can use it to drive my second speakers. Due to the crossover point between the midrange and the tweeters I want the amps to be as similar as reasonable that is the same topology and the same tubes. I think the signal inductance and capacitance on the tweeter amps should be lowered. I would be grateful for the recommendations of the values or calculating formulas.
I don’t want to replace the speakers as I don’t believe that for a price affordable for me I can get speakers which are better for me. They satisfy me for the most parts, dynamic, soundstaging, listening at low or high level; I don’t get tired listening to them for a prolonged time. The only issue that I want to fix is some washing down of timbre in the midrange (I just want a little bit more of wood in the violin sound, etc). I do believe that the main (but not the only) culprit is my amplifier. It’s just a 12 channels AT-6012.
I do realize the complexity and the cost of such project. It will take for me probably more than a year from the first soldered joint. I do realize the danger of very high voltage exceeding 1KV.
The approximate schematic I’m going to use is
It’s essentially a DRD cascade driving trough an interstage GM-70. I saw on this forum a little bit different implementation of DRD idea by Thorsten Loesch. It seems for me more elegant so I will probably use it with his permission.
I have some questions about A2 class and about GM-70 in A2. I found curves with positive grid lines at the end of
http://frank.pocnet.net/sheets/018/g/GM70.pdf
The question is do they look good enough (that is are they spaced evenly enough) so there is a sense to drive GM-70 into A2.
Another question is the ability of 300B to drive the grid of GM-70 via interstage not in terms of voltage but in terms of current. In Wikipedia
Single-ended triode - Wikipedia, the free encyclopedia
I read the following
Class A2
Class A2 amplifiers can overcome a high Rp by driving the grid positive with respect to the plate. Because this makes the grid a secondary anode, it too will draw current from the cathode while accelerating the remaining electrons towards the plate. Grid currents can place extreme demands on the driving circuitry, sometimes requiring as much as 8 watts input for larger tubes such as the 211.
If 211 requires 8 Watts of power for A2 than GM-70 may require even more. In this case 300B will not drive it from its anode even via an interstage transformer and I may probably have to replace the interstage by a choke and to drive the output via mosfet follower as in tubelab’s 845SE.
Another issue I read about is that an interstage transformer doesn’t like transition from A1 to A2. I don’t know if the issue is serious enough. I like interstage coupling as it simple enough and I would prefer not to increase the complexity unnecessarily.
For simplicity I want to use a solid state PSU. I have some question about capacitors. Is there available for a reasonable price high voltage non electrolytic capacitors with capacity of around 70uF and 2KV voltage? The size of the capacitor doesn’t bother me if doesn’t exceed the size of a brick too much.
Any critic and recommendations are welcome.
Thank you
Victor
I want to build amplifiers for mid & high frequency for my Linkwitz Orions. They are active speakers with an external line level crossover. The tweeter and midrange drivers are
Seas T25CF002 THE ART OF SOUND PERFECTION BY SEAS - E0011-06 T25CF002
and Seas W22EX001
THE ART OF SOUND PERFECTION BY SEAS - E0022-08S W22EX001
The sensitivity is 87-88 Db/1Wat so I will need all power that can be obtained from the output tube. The crossover points are 120 Hz & 1440 Hz. The crossover is Linkwitz-Riley 4th order. I want the amp driving the midrange to be a full range so I can use it to drive my second speakers. Due to the crossover point between the midrange and the tweeters I want the amps to be as similar as reasonable that is the same topology and the same tubes. I think the signal inductance and capacitance on the tweeter amps should be lowered. I would be grateful for the recommendations of the values or calculating formulas.
I don’t want to replace the speakers as I don’t believe that for a price affordable for me I can get speakers which are better for me. They satisfy me for the most parts, dynamic, soundstaging, listening at low or high level; I don’t get tired listening to them for a prolonged time. The only issue that I want to fix is some washing down of timbre in the midrange (I just want a little bit more of wood in the violin sound, etc). I do believe that the main (but not the only) culprit is my amplifier. It’s just a 12 channels AT-6012.
I do realize the complexity and the cost of such project. It will take for me probably more than a year from the first soldered joint. I do realize the danger of very high voltage exceeding 1KV.
The approximate schematic I’m going to use is
It’s essentially a DRD cascade driving trough an interstage GM-70. I saw on this forum a little bit different implementation of DRD idea by Thorsten Loesch. It seems for me more elegant so I will probably use it with his permission.
I have some questions about A2 class and about GM-70 in A2. I found curves with positive grid lines at the end of
http://frank.pocnet.net/sheets/018/g/GM70.pdf
The question is do they look good enough (that is are they spaced evenly enough) so there is a sense to drive GM-70 into A2.
Another question is the ability of 300B to drive the grid of GM-70 via interstage not in terms of voltage but in terms of current. In Wikipedia
Single-ended triode - Wikipedia, the free encyclopedia
I read the following
Class A2
Class A2 amplifiers can overcome a high Rp by driving the grid positive with respect to the plate. Because this makes the grid a secondary anode, it too will draw current from the cathode while accelerating the remaining electrons towards the plate. Grid currents can place extreme demands on the driving circuitry, sometimes requiring as much as 8 watts input for larger tubes such as the 211.
If 211 requires 8 Watts of power for A2 than GM-70 may require even more. In this case 300B will not drive it from its anode even via an interstage transformer and I may probably have to replace the interstage by a choke and to drive the output via mosfet follower as in tubelab’s 845SE.
Another issue I read about is that an interstage transformer doesn’t like transition from A1 to A2. I don’t know if the issue is serious enough. I like interstage coupling as it simple enough and I would prefer not to increase the complexity unnecessarily.
For simplicity I want to use a solid state PSU. I have some question about capacitors. Is there available for a reasonable price high voltage non electrolytic capacitors with capacity of around 70uF and 2KV voltage? The size of the capacitor doesn’t bother me if doesn’t exceed the size of a brick too much.
Any critic and recommendations are welcome.
Thank you
Victor