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Author Topic: AKG C28A and C28C with N12 / N28A PSU ?  (Read 1634 times)

LLL

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AKG C28A and C28C with N12 / N28A PSU ?
« on: July 18, 2019, 10:00:28 am »

Hi All,

Ive got a quick question regarding the PSU requirements of both the C28A (6072)and the C28C (Nuvistor 7586)

looking at the schematics for both, it looks like the N12 and N28A PSU's would be good with both mics ?
B+ 120V (pin 5 N12 / N28A)
H+ 6.3V (pin 8 N12 / pin 4 N28A psu side - pin 4 mic side)

I always thought that the Nuvistor 7586 needed around B+100V. After just checking the datasheet for the 7586, it quotes maximum plate voltage as 110V.

The reason for asking is, that Ive got to build a power supply for each of the C28's !

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klaus

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Re: AKG C28A and C28C with N12 / N28A PSU ?
« Reply #1 on: July 18, 2019, 12:30:45 pm »

You are not looking at the right schematics.
BOTH C28 types use B+ fo 120V (do not confuse this with plate voltages!)
However, heater max for the Nuvistor C28C is 5.0 VDC, and 6.3VDC for the 6072 glass tube versions.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

LLL

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Re: AKG C28A and C28C with N12 / N28A PSU ?
« Reply #2 on: July 19, 2019, 10:41:47 am »

You are not looking at the right schematics.
BOTH C28 types use B+ fo 120V (do not confuse this with plate voltages!)
However, heater max for the Nuvistor C28C is 5.0 VDC, and 6.3VDC for the 6072 glass tube versions.

Thanks for clarifying Klaus.
Would it be better if I de-rate the heaters by 5% ? just so the tubes are not stressed ?
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klaus

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Re: AKG C28A and C28C with N12 / N28A PSU ?
« Reply #3 on: July 19, 2019, 01:49:55 pm »

I use 6.2VDC for EF86 and 6072 etc. and 4.95VDC to 5.00VDC for 7586 Nuvistors- all measured at the tube. Use the manufacturer's subscribed/nominal voltages when measuring inside the power supply.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com
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