Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on February 22, 2017, 09:28:14 am

Title: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 22, 2017, 09:28:14 am

I was looking to some Voice of the Music schematics and I recognized somethind that sounds odd to me ....

The Power Tube cathode is connected to ground via dedicated portion of the OT secondary winding  :rolleyes: :think1:

(http://i.imgur.com/F8Jeebu.jpg)

(http://i.imgur.com/mlcTKwm.jpg)

Which can be the reason for this circuit choice  :w2:

Franco

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: sluckey on February 22, 2017, 09:41:29 am

negative feedback.

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 22, 2017, 09:55:20 am

Thanks Steve

NFB, and they also use a connection to V1 cathode for tone control .....

Franco

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 22, 2017, 10:16:26 am

WOW, didn' noticed this thing before ..... (on the first schematic)

give a look to the Fixed Bias supply, really uncommon don't you ?

A PT without CT but that has a Bias Winding ......... really strange

or it has a CT and that is a Back Biasing ??


Franco

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: sluckey on February 22, 2017, 10:34:50 am

Quote

or it has a CT and that is a Back Biasing ??

Yes, that's correct.

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 22, 2017, 12:06:24 pm

Ah, OK, the first schematic has that particular draw in a way that confuses

Thanks

Franco

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: VMS on February 22, 2017, 04:31:58 pm

Here is some info on that feedback:


http://livinginthepast-audioweb.co.uk/index.php?p=feedbackwindings (http://livinginthepast-audioweb.co.uk/index.php?p=feedbackwindings)

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 22, 2017, 05:17:22 pm

Many Thanks for the link VMS

--

For those who are interested on backbiasing

http://www.aikenamps.com/index.php/what-is-back-biasing (http://www.aikenamps.com/index.php/what-is-back-biasing)

Franco

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: HotBluePlates on February 22, 2017, 09:14:07 pm

Quote from: kagliostro on February 22, 2017, 09:55:20 am

NFB, and they also use a connection to V1 cathode for tone control .....

Both Treble & Bass controls are implemented in the feedback loop.

Title: Re: Which is the purpose of this 6V6 cathode connection ?
Post by: kagliostro on February 23, 2017, 03:12:52 am

Ciao HotBluePlates

I was trying to say that

Franco