Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Swampertech on July 23, 2019, 03:30:17 pm

Title: Master volume options
Post by: Swampertech on July 23, 2019, 03:30:17 pm: Hello All, I want to get your opinions as to the most transparent and usable linear Master Volume control circuit which would be installed after a LTP PI that drives a push/pull output stage (see attached). The circuit also has NFB with presence control, and I’ve read that there is some negative interaction with the post PI MV (Trainwreck Type-2/Lar-Mar Master Volume) and the feedback circuit. I’ve included the drawing with a pre PI single pot master volume. Thank you for your input!
Title: Re: Master volume options
Post by: shooter on July 23, 2019, 04:21:29 pm: read these links, bet there are 27 ways to kill the power so the neighbors don't shoot you :icon_biggrin:

http://el34world.com/Forum/index.php?topic=3496.0
http://el34world.com/Forum/index.php?topic=21173.0
http://el34world.com/Forum/index.php?topic=24887.0
http://el34world.com/Forum/index.php?topic=24905.0
Title: Re: Master volume options
Post by: Swampertech on July 23, 2019, 06:25:31 pm: Thanks Shooter! I did read those threads a while back.
Title: Re: Master volume options
Post by: mresistor on July 23, 2019, 06:44:24 pm: Quote from: shooter on July 23, 2019, 04:21:29 pm
read these links, bet there are 27 ways to kill the power so the neighbors don't shoot you :icon_biggrin:

http://el34world.com/Forum/index.php?topic=3496.0 (http://el34world.com/Forum/index.php?topic=3496.0)
http://el34world.com/Forum/index.php?topic=21173.0 (http://el34world.com/Forum/index.php?topic=21173.0)
http://el34world.com/Forum/index.php?topic=24887.0 (http://el34world.com/Forum/index.php?topic=24887.0)
http://el34world.com/Forum/index.php?topic=24905.0 (http://el34world.com/Forum/index.php?topic=24905.0)

27 legal ways.. LOL
Title: Re: Master volume options
Post by: Big_Mike on July 23, 2019, 08:01:39 pm: As I understand it, with a PPIMV, the more you turn it down, the less negative feedback you get from the output transformer. It can cause a different frequency response at low volumes.

There are a couple of design considerations you need to think about concerning whether to use a pre-phase inverter master or a PPIMV - 1) how important is the clipping and distortion you will get from the phase inverter? 2) how important is the negative feedback to the sound and feel of the amp, and 3) can you modify the preamp to get the gain and clipping you would otherwise get from overdriving the phase inverter, allowing you to use a pre-phase inverter master and keep the negative feedback?
Title: Re: Master volume options
Post by: Swampertech on July 23, 2019, 08:34:30 pm: Big_Mike, thanks for the reply. My main concern is that the amp acts and sounds like it doesn't have a master volume. Assuming one would use the master volume at max setting most of the time, there should be no tonal coloration. When using either MV (pre or post), I'd like the tone to stay as close to the sound the amp has when the MV is maxed out, and that includes using NFB or no NFB.