Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: stinga11 on March 17, 2019, 03:35:51 pm

Title: My version of 5f6a 6V6
Post by: stinga11 on March 17, 2019, 03:35:51 pm

In my absurd attempt to continue learning from amplifiers I have made a new schematic. I have tried to take a Blackface and make it sound like a Bassman 5f6a (I know it will not sound the same and especially that it will not have the same gain). I would like you to see it and correct me the mistakes, because the idea is to continue learning. I do not know if it would be good to do it with a 5Y3 rectifier and without a filter choke to obtain more sag. If you could go through and look at the schematic and offer me some advice it would be excellent.

Title: Re: My version of 5f6a 6V6
Post by: tubenit on March 17, 2019, 06:39:20 pm

Have you considered using a mosfet cathode follower so the tone stack is actually coming off the cathode like in a 5F6-A. IF you wanted to do that, then you could have it be more "bassman like" without having to add another tube. 

The schematic corresponds to the layout board which was used for this build:  http://el34world.com/Forum/index.php?topic=23013.msg246671#msg246671

With respect, Tubenit

Title: Re: My version of 5f6a 6V6
Post by: stinga11 on March 19, 2019, 04:45:02 pm

New version with 5Y3 rectifier. I lowered the filtering to be in line with the new rectifier. I eliminated the filter choke to have a warm sound and to have more sag in the signal (imitating the Deluxe 6G3). I also lowered the certain coupling capacitors so as not to have problems with the bass notes.

Title: Re: My version of 5f6a 6V6
Post by: pdf64 on March 20, 2019, 06:29:31 am

It no big deal, but the 2W spec for the LTP tail resistor seems unnecessary?
Maybe add a grid stopper for the 2nd stage, to replicate the 270k mixers, eg 120k or 100k; it may be a bit bright and perhaps have a lower margin of stability without that.
Also depending on the intended OT secondary and load impedance, you may want to adjust the 56k NFB resistor value, in order to get a similar degree of NFB as the 5F6a

Title: Re: My version of 5f6a 6V6
Post by: sith on March 21, 2019, 02:54:18 pm

@ stinga

aren't your voltages bit off for bassssman type amp?

Title: Re: My version of 5f6a 6V6
Post by: tubenit on March 21, 2019, 03:14:31 pm

I would anticipate a 330-0-330 PT with a 5Y3GT to put about 363 volts on node A not 465v.

330 x 1.1 (5Y3GT) = 363v

330 x 1.2 (5V4 or 5U4GT) = 393v

330 x 1.3 (GZ34) = 429v

330 x 1.4 =  462v  solid state rectifier

With respect, Tubenit

Title: Re: My version of 5f6a 6V6
Post by: stinga11 on March 21, 2019, 06:13:36 pm

@sith
The Richter RS-22 amplifier has those voltages and sounds out of this world !!!

@tubenit
It was a type error.