aboos
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« Reply #315 on: July 10, 2023, 06:45:43 PM » |
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Vlad's PCF802 phono stage is very well designed and makes many things right where others fail. The only drawback is it's highish output impedance wich such a tube buffer effectively eliminates.
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Andreas
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Tomcat1969
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« Reply #316 on: July 10, 2023, 08:47:39 PM » |
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Vlad's PCF802 phono stage is very well designed and makes many things right where others fail. The only drawback is it's highish output impedance wich such a tube buffer effectively eliminates.
Totally agree. And I am planning the buffer... |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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Tomcat1969
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« Reply #317 on: July 16, 2023, 03:09:34 PM » |
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 I've drawn this schematic of the buffer Niclas suggested but with both channels. Does it look OK? |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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wenig watt
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Der Kopf ist rund...
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« Reply #318 on: July 16, 2023, 03:28:58 PM » |
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Hello Billy,
my phono has a B+ of 300V maybe it needs a resistor to get to the 280V?
Best regards
Arndt
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...damit das Denken die Richtung ändern kann.
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niclaspa
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« Reply #319 on: July 16, 2023, 04:15:24 PM » |
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The circuit will work fine with 300 V. Keep it as simple as possible increases the chance of success.  |
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Niclas
Ernst ist das Leben, heiter ist die Kunst
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Tomcat1969
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« Reply #320 on: July 16, 2023, 04:29:05 PM » |
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Hello Billy,
my phono has a B+ of 300V maybe it needs a resistor to get to the 280V?
Best regards
Arndt
Hello Arndt. Thanks for looking. I've not tried to draw a circuit in a long, long time. I've got a transformer that has the right voltages (I think... maybe 285v.) so I'll use that and possibly a resistor now I have to do maths  I've got enought room in the case. I have a couple of regulator boards as well. One for the heaters and one for the B+. On to making it now. By the way, I Love the stick you are making for your mum! |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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Tomcat1969
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« Reply #321 on: July 16, 2023, 04:33:27 PM » |
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The circuit will work fine with 300 V. Keep it as simple as possible increases the chance of success. Noted! Thank you Niclas. I was thinking that a PSU for an 834 clone would be good. |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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niclaspa
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« Reply #322 on: July 16, 2023, 05:40:27 PM » |
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Why don't you use the power supply for the phono stage? It can supply your buffer as well. You only need 6.3 V for the ECC82 heaters.
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Niclas
Ernst ist das Leben, heiter ist die Kunst
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aboos
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« Reply #323 on: July 16, 2023, 07:41:21 PM » |
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The buffer only needs 16 mA when supplied with 280 Vdc (8 mA / channel) - so no need to build another HV supply. If you use an ECC82, you can run the heater with 6.3V or 12.6V. Furthermore, the ECC82 has a high Cathode-Heater voltage spec (150V) which is quite high - so no need to elevate this additional heater supply. If your HV supply is higher than 280V, elevate the heater up to 100V.
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Andreas
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Tomcat1969
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« Reply #324 on: July 16, 2023, 07:55:59 PM » |
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Why don't you use the power supply for the phono stage? It can supply your buffer as well. You only need 6.3 V for the ECC82 heaters.
Only because I'll have to put the transformer in for the 6.3v so I thought I would use it for the b+ for the buffer as well. So, take the B+ from the existing psu and 6.3v from another transformer? I'm learning here and I get mixed up but I don't do anything till I'm sure and I'm careful. |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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Tomcat1969
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« Reply #325 on: July 16, 2023, 07:57:30 PM » |
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The buffer only needs 16 mA when supplied with 280 Vdc (8 mA / channel) - so no need to build another HV supply. If you use an ECC82, you can run the heater with 6.3V or 12.6V. Furthermore, the ECC82 has a high Cathode-Heater voltage spec (150V) which is quite high - so no need to elevate this additional heater supply. If your HV supply is higher than 280V, elevate the heater up to 100V.
OK, noted. Many thanks gentlemen. |
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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niclaspa
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« Reply #326 on: July 16, 2023, 08:41:25 PM » |
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So, take the B+ from the existing psu and 6.3v from another transformer? I think that is the easiest solution. As Andreas points out, you can also use 12.6 V to heat ECC82. You could even use a small 12 V transformer (delivering at least 150 mA), since 10% deviance from the specified heater voltage is acceptable. Small 12 V transformers are cheap and easy to find. Andreas mentions heater elevation. You can almost get away without it, but it is not a bad idea to include it. Here is how to do it:  The 150 k resistors form a voltage divider. Their mid point is at half the high tension voltage, i.e. 150 V. This is connected to the heater supply. |
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Niclas
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Tomcat1969
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« Reply #327 on: July 16, 2023, 09:16:21 PM » |
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Many thanks again Niclas.
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Peculiar Permali Platform PTP5 with Siens long bearing and 14" platter, 12"SUPATRAC Blackbird/London Decca or Bokrand Sonoro/SPU. Parks Puffin, B1 with Korg triode, 2 x Zerozone class D monoblocks, Tannoy Eaton speakers. Oh, and Nigels Speed Controller.
Billy
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wenig watt
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Der Kopf ist rund...
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« Reply #328 on: July 16, 2023, 11:08:27 PM » |
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Someone once explained that this reduces the interference voltage?
Kind regards
Arndt
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...damit das Denken die Richtung ändern kann.
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aboos
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« Reply #329 on: July 17, 2023, 06:31:27 AM » |
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In case of a cathode follower buffer as suggested, the cathode will sit at approx. 1/2 the supply voltage - 150V in case of HV of 300 V while the heater is at ground potential. This high voltage needs to be isolated by the heater wire insulation inside the cathode. If voltage difference is too high some leakage currents will start to flow introducing noise, crackle or even hum. By elevating the DC reference potential of the heater voltage, the voltage difference between heater and cathode gets reduced and thus eliminates these effects.
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Andreas
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