VVR in Overdrive Special

[Guy77]

I had issues with voltage spikes when going from my house to my brothers house with my ODS 50 watt amp. My voltages at my wall outlet (old house in the city) is 115 volts and my brothers place north of the city has wall voltages of 124 volts.
This created a 35 - 40 volt spike in my B+ and my tubes (5881) were no longer in there sweet sounding range, they sounded more sterile when running at 480 v as compared to 440v . I rigged together this VVR setup with a heatsink, plastic stand-offs and a string of 10v 5 watt diodes and it has been working great! I wired them with a 3 way NKK toggle switch (under the chassis) so I could go from no voltage drop to 20v and then to 40v B+ drop. I placed the diodes on the center tap of the power tranfsormer just before it goes to ground.

Cheers

Guy

[John_P_WI]

Cool, after being involved with power scaling for many years I would suggest that not only the change in power tube voltage affected the tone, but also the change in preamp voltages too. I find that the change in preamp voltages to be the most dramatic in tonal change.

Having regulated rails can help with a more consistent amp, especially a pass regulator acting as a voltage clamp on the preamp rail.

[renshen1957]

Cool, after being involved with power scaling for many years I would suggest that not only the change in power tube voltage affected the tone, but also the change in preamp voltages too. I find that the change in preamp voltages to be the most dramatic in tonal change.

Having regulated rails can help with a more consistent amp, especially a pass regulator acting as a voltage clamp on the preamp rail.

Hi John,

I second your comment. My day job involves building and testing unregulated power supplies, and the mains voltage yo-yo's up and down from 120 V all day, long, especially around lunch time (down), between meal time (up), summer afternoons (down), and also on location (the country is consistently higher than the city).

So much vintage and non-vintage equipment that would benefit with a voltage clamp.

Best regards,

Steve

PS Good to hear from a former Powerscaling.com contributor.

[John_P_WI]

Steve, good to see you around here again too.

John

[Guy77]

Cool, after being involved with power scaling for many years I would suggest that not only the change in power tube voltage affected the tone, but also the change in preamp voltages too. I find that the change in preamp voltages to be the most dramatic in tonal change.

Having regulated rails can help with a more consistent amp, especially a pass regulator acting as a voltage clamp on the preamp rail.

Yes very true, when I change plate resistors on my first preamp tube I noticed a lot of change in tone. Tone would break up much sooner with lower value plate resistors (100K) on V1 . Then with higher value plate resistors (220K) tone would get tighter. I find that the tighter tone on v1 makes the overdrive channel sound nicer.

Cheers

Guy