Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on October 15, 2012, 07:17:50 am

Title: Standalone Tube Preamp with CF output + unused triode as FX Loop return question
Post by: kagliostro on October 15, 2012, 07:17:50 am

I want to build standalone tube preamps using preamps splitted from complete amplifiers

assuming the preamp is this (but could be another)

(http://s8.imagestime.com/out.php/t781145_MarshallDual50Pagina1.jpg) (http://www.imagestime.com/show.php/781145_MarshallDual50Pagina1.jpg.html)

and using this FX Loop schematic as reference

(http://lh3.ggpht.com/_MHnI-B0pJ8k/TSHnC0EmElI/AAAAAAAAAVQ/_nQ4kcTN4QQ/s800/BEST!%20DumblelatorSchematic-1.jpg)

to have an output adequate for lines I must add a CF

doing this (if I use a 12a*7 tube instead of a 6av6 tube, for availability reasons) I'll have an unused triode

What to do with this unused tube ?

Tubeswell tried to give me some inputs about possibilities and this idea come to me

I've think to duplicate the CF send circuit (so the output of both tubes is adequate for line drive)

Can V1b act correctly in this schematic ?

The input impedance of V1b is adequate to receive the output of a pedal ?

Have you councils about components values ?

Thanks

K

Title: Re: Standalone Tube Preamp with CF output + unused triode as FX Loop return question
Post by: tubenit on October 16, 2012, 05:27:26 am

I would use a mosfet CF where you have V3-b and then use the Dumblator active effects loop which works great.  I have a mosfet CF on the D'Mars OD Special and it sounds wonderful and I use a Dumblator type active effects loop which also sounds great.


EDIT:  Oops!  Nevermind, I just reread your question and realized my answer did not match it. Sorry about that. I'll leave this schematic up in case some other viewer has an interest in this.

With respect, Tubenit

Title: Re: Standalone Tube Preamp with CF output + unused triode as FX Loop return question
Post by: kagliostro on October 16, 2012, 05:10:21 pm

Hi Jeff

thanks anyway for your effort on trying to find a solution

I'm thinking that the principal problem of a schematic like that I've draw

is the fact that the return circuit will have a gain near (or less) to 1

may be this will be enough (or not ??  :think1:)

K