Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on July 22, 2012, 07:03:56 am

Title: VVR : bad experience ?
Post by: Colas LeGrippa on July 22, 2012, 07:03:56 am

VVR circuit appears to me not to be  a reliable circuit, twice it failed though I have screwed the mosfet on a heat sink with an appropriate isolator from gnd. Symptons are just like a bad filter cap or bad power tube would do: loss of power and harsh sound. Did you guys having trouble with VVR's ?

Title: Re: VVR : bad experience ?
Post by: tubenit on July 22, 2012, 07:43:33 am

Quote

Did you guys having trouble with VVR's

Used it on 4 different amps.  No issues.

With respect, Tubenit

Title: Re: VVR : bad experience ?
Post by: Colas LeGrippa on July 22, 2012, 10:23:05 am

these mosfet ( NTE2973) can stand 900V so way over needed , after the data sheet, the only problem I see is the static electricity that they are sensitive to, maybe I did something wrong in handling them

Colas

Title: Re: VVR : bad experience ?
Post by: Ed_Chambley on July 22, 2012, 11:10:33 am

I have tried them in many different amps.  I think the idea is great.  Never had any problems with the actual circuit, but I also have never really liked the result.  I have tried scaling everything and just the power section, but it ends up sounding like I am simply over-driving the preamp and when everything is scaled the tone-stack changes dramatically.  It is probably just the way or amp I have put them in.  I have never tried one on a amp less than 40 watts.

Title: Re: VVR : bad experience ?
Post by: The_Gaz on July 23, 2012, 01:06:57 am

I've found it reliable, but only tried it in 30W amps. I think it sounds good, like anything, only to a certain point. What I find, however, is that it can convincingly take the volume down lower than a good master volume (PPIMV) or attenuator before sounding stupid.