Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: archaos on January 15, 2013, 11:31:35 am

Title: Yet another plexi 50 (head)
Post by: archaos on January 15, 2013, 11:31:35 am

Whereas it formerly squealed (positive feedback instead of negative) like cutting open pig threat, it now roars. I just had to reversed the OT primary leads, & was done.
B+ 405V.
Voltages here : http://www.el34world.com/charts/valve/ValveData.php?e=view&f=14616 (http://www.el34world.com/charts/valve/ValveData.php?e=view&f=14616)

It has some KOC/Blencowe features :

  - full-wave rectified bias supply
  - external bias access with banana jacks & pots
  - independent bias controls for each tubes
  - hum-loop block network
  - heater elevation (divider from the HT, although I may have chosen the bias supply so as to use the negative elevation voltage instead)

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 15, 2013, 11:35:02 am

...&

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 15, 2013, 11:37:24 am

...& finally

Title: Re: Yet another plexi 50 (head)
Post by: Backwoods Joe on January 15, 2013, 12:02:54 pm

Good Job! Looks great.  :icon_biggrin:

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 15, 2013, 12:14:30 pm

Thanks !

Title: Re: Yet another plexi 50 (head)
Post by: Ritchie200 on January 15, 2013, 12:39:14 pm

Very nice!  I'm not sure if you know this but - as a requirement, if you post amp porn, you must also post sound.  Otherwise we will never talk to you again! :icon_biggrin:

Jim

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 15, 2013, 12:50:54 pm

Thanks !

Quote

I'm not sure if you know this but - as a requirement, if you post amp porn, you must also post sound.  Otherwise we will never talk to you again!

Arghh...Hey, why not ? :icon_biggrin:

Title: Re: Yet another plexi 50 (head)
Post by: smackoj on January 15, 2013, 06:26:16 pm

'Show and tell' around here means just that, show a little, play a lot!

 :icon_biggrin:

Title: Re: Yet another plexi 50 (head)
Post by: Backwoods Joe on January 15, 2013, 08:26:12 pm

Was wondering what brand are the filter caps? All i can make out is "audio grade".

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 16, 2013, 03:17:07 am

Quote

'Show and tell' around here means just that, show a little, play a lot!

 :icon_biggrin:

Quote

Was wondering what brand are the filter caps?

Jensen & Evox Rifa filter caps actually.

Quote

All i can make out is "audio grade".

https://audio.jensencapacitors.com/products/capelyt/elytaxial/ (https://audio.jensencapacitors.com/products/capelyt/elytaxial/)

Title: Re: Yet another plexi 50 (head)
Post by: plexi50 on January 16, 2013, 07:14:34 am

Beautiful work! Dont forget to invest in some ear plugs. Ive gone from (Save The Whales) to (Save Your Hearing). Too late for me. Just saying/

Title: Re: Yet another plexi 50 (head)
Post by: archaos on January 16, 2013, 07:35:39 am

Thanks ! Thanks for the tip as well, unfortunately I believe it's the same thing for me = too late...