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August 10, 2020, 01:03:33 AM

Author Topic: Paramount 300B hum balance adjustment  (Read 394 times)

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Offline Paul Joppa

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Re: Paramount 300B hum balance adjustment
« Reply #15 on: July 02, 2020, 05:49:20 AM »
As tubes age, some mechanical warping takes place (as I understand it, typically the filament) due to the number of heating/cooling cycles. Since these tubes are well used, it is reasonable to guess that's the reason for the modest change in hum level.

Here's a little background: The design goal was 2mV, which is quiet enough for all but the most efficient all-horn speakers. Without the DC filament supply, I was not able to get hum below 5-8mV. If the hum is a problem, an electrolytic capacitor can be installed at the output of the filament supply to reduce it further. We didn't include that in the stock amp in the interest of avoiding capacitors in the filament supply, which some listeners think are responsible for a "flattening" of the sound. I find it to be a very subtle difference, but YMMV - we all hear a little differently.

In the current Stereomour and Kaiju, we have separated the DC filament supply as upgrade kits, since for most speakers even 5mV is good enough to be inaudible.
Paul Joppa

Offline Gerry E.

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Re: Paramount 300B hum balance adjustment
« Reply #16 on: July 02, 2020, 09:50:14 AM »
Hi:

This thread motivated me to measure the hum on my Paramounts.  Using the same page 64 procedure as above, with and without a load, I can dial in .000v on both amps.  Is that possible?  The meter is an inexpensive Radio Shack auto range unit but it has worked well over the years.  My speaker sensitivity is approx. 95dB and I hear almost no hum with my ear to the speaker drivers.

Gerry         

Offline Paul Birkeland

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Re: Paramount 300B hum balance adjustment
« Reply #17 on: July 02, 2020, 10:05:39 AM »
0.000V tells you it's less than 1mV, which is generally what I have measured on Paramounts (about 600uV).
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Anton

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Re: Paramount 300B hum balance adjustment
« Reply #18 on: July 02, 2020, 04:30:24 PM »
Hi:

This thread motivated me to measure the hum on my Paramounts.  Using the same page 64 procedure as above, with and without a load, I can dial in .000v on both amps.  Is that possible?  The meter is an inexpensive Radio Shack auto range unit but it has worked well over the years.  My speaker sensitivity is approx. 95dB and I hear almost no hum with my ear to the speaker drivers.

Gerry         

Hi Gerry,
Do you have a standard version of the Paramounts or the one with the soft start upgrade?
Thanks
Eros phono / Foreplay III extended upgrade / Paramount 300B/ S.E.X. 2.1 impedance switch upgrade

Offline Gerry E.

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Re: Paramount 300B hum balance adjustment
« Reply #19 on: July 04, 2020, 09:45:18 AM »
Hi Gerry,
Do you have a standard version of the Paramounts or the one with the soft start upgrade?
Thanks


Hi Anton:

Soft Start v1.1.

Gerry   

Offline Anton

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Re: Paramount 300B hum balance adjustment
« Reply #20 on: July 04, 2020, 03:57:31 PM »


Hi Anton:

Soft Start v1.1.

Gerry   

Thank you Gerry, and Happy 4th of July!

I wonder whether soft start upgrade would affect the hum level?

Thanks

Eros phono / Foreplay III extended upgrade / Paramount 300B/ S.E.X. 2.1 impedance switch upgrade

Offline Paul Birkeland

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Re: Paramount 300B hum balance adjustment
« Reply #21 on: July 04, 2020, 04:09:41 PM »
I wonder whether soft start upgrade would affect the hum level?

No.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Anton

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Re: Paramount 300B hum balance adjustment
« Reply #22 on: July 05, 2020, 12:29:20 PM »
Eros phono / Foreplay III extended upgrade / Paramount 300B/ S.E.X. 2.1 impedance switch upgrade