4th November 2008, 08:05 PM
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#1 |
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diyAudio Member
Join Date: Sep 2005
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Hi-end 845 with only two stage
yesterday evening I have started some measurement about 6HV5A used like 845 driver.
The schematic was very simple: inductance on anode, Rk = 100ohm, Ck = 470uF, Rg = 75Kohm and output capacitor 2.2uF on 33 or 100Kohm load. With medium voltage operation (about 600V) these tubes give low sperformances because distortion is high 1.1% at 25Vrms. The good result are obtain using 980V and 100ohm on catode to keep the power nead the 30w (35w is the maximun allowed), bias about 30mA. With these value I have got the good 1% at 120Vrms on 33Kohm load. The freq. response is limited to 50Hz(-3db) with 20H but it will be 10Hz(-3db) using 100H 50mA Sowter 8982. The voltage amplification is 120/0.7=155x. audiodesign has attached this image: Click the thumbnail to see the original image. |
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4th November 2008, 08:06 PM
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#2 |
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diyAudio Member
Join Date: Sep 2005
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Finally the first test result using 6HV5A to drive 845
6HV5A loaded by 20H (Rdc=70ohm) and Rk=100ohm Ck=220uF 950V 28mA 845 loades by Tango X-10S 10K/8ohm Vg=150v Rg=22Kohm 950V 100mA 10Vrms on 8ohm with 2% thd Interstage 2.2uF // 0.33uF Audyn-Cap Plus Very good sound Very good voltage gain Power can be increased using 1100V instead of 950v Soon next test and photos |
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4th November 2008, 08:07 PM
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#3 |
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diyAudio Member
Join Date: Sep 2005
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Clio measurement
10Vrms on 8ohm |
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4th November 2008, 08:38 PM
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#4 |
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diyAudio Member
Join Date: Sep 2005
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The 20H inductance is only for this first test.
I am thinking to change this with LL1668/25mA See actual frequency response |
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4th November 2008, 08:40 PM
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#5 |
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diyAudio Member
Join Date: Sep 2005
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4th November 2008, 09:01 PM
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#6 |
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diyAudio Member
Join Date: Sep 2005
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test environment
Soon measurement with Lundahl AM output trasf. series |
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5th November 2008, 07:24 AM
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#8 |
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diyAudio Member
Join Date: Sep 2005
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This is the first schematic
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5th November 2008, 07:39 AM
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#10 |
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diyAudio Member
Join Date: Jun 2007
Location: Australia
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Hi Andrea,
I am right now in the process of building your 'New 845' with the EL34/845 combo. This one looks a lot simpler. How does it compare? Can it be driven direct from a CD player I am just about to finalise the power transformer order. Should I hold off? I would love to see a schematic of your power supply. Cheers, Rob |
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