Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jack1962 on September 13, 2013, 09:57:54 am

Title: VOX AC30 TopBoost and the Hall VVR
Post by: Jack1962 on September 13, 2013, 09:57:54 am
I installed this Hall VVR the 1st version of this mod , let me first say it was a very easy install , and that's where the fun ended lol This mod is worth the $30 but not a penny more a PPIMV would be a better mod for this. It is a very interesting circuit and I believe if a person(not me) wanted to modify this mod lol it would work just fine . I traced the circuit and made a drawing , and would post it but I doubt ya"ll could read my writing lol
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: Willabe on September 13, 2013, 11:32:18 am
I believe if a person(not me) wanted to modify this mod lol it would work just fine .

What's it not doing that you would want to modify it to get it to do?


               Brad     :icon_biggrin:
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: Jack1962 on September 14, 2013, 12:42:03 pm
I installed it in a customers amp , not one of mine. What I would want it to do is be build with more reliable components and some kind of protection in the event that NTE mosfet burnt or shorted.
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: Leevi on September 15, 2013, 09:11:37 am
I have installed VVR for AC30 and noticed that a good cooling of the MOSFET is very important.
/Leevi
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: kagliostro on September 15, 2013, 09:52:04 am
If the mosfet Input and output shorts you have your max B+, not more

il the circuit shorts to ground a fuse before it can prevent further demage

K
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: Jack1962 on September 17, 2013, 03:44:31 pm
It's a great idea and works fairly well with fixed bias amps , but my question is would it work as well on one that isn't fixed bias ?
Title: Re: VOX AC30 TopBoost and the Hall VVR
Post by: Leevi on September 19, 2013, 09:41:29 am
According to my experiences it works better in cathode biased amps.
Furthermore the VVR circuit is then easier to install since you don't need to regulate the bias voltage.
/Leevi