5F4 with 6G16 tremolo

[Bieworm]

Hi fellas!

I'm about to start ordering parts for my next build. I will be a 5F4 Super with the addition of a 6G16 tremolo.
I worked out a schematic and maybe you can look if there's anything wrong?

I'd like to use the Power Transformer from inMADout, sold by tube town. It's the PT for the high power 5E3 (320-0320 @ 300mA, 5A filament current and 3A rectifier filament current)
The OT of choice would be the Hammond 1760JB

Any ideas for adjustable bias? I think it's best to add one, no? Is the approach on my schematic a good starting point?

Any comments will be great!

[tubenit]

As I am understanding your schematic, you are going to have a PPIMV along with the tremolo and bias?  Is this correct?  I don't know if I've seen that arrangement before?  Not saying it won't work as I don't know enough about that to offer an opinion.


With respect, Tubenit

[Bieworm]

As I am understanding your schematic, you are going to have a PPIMV along with the tremolo and bias?  Is this correct?  I don't know if I've seen that arrangement before?  Not saying it won't work as I don't know enough about that to offer an opinion.


With respect, Tubenit

Indeed.. I have the same configuration on my 6G3.  It works like a charm!! Very, very good LV by the way!! I added one yesterday to my TK imperial clone!! Nice to be able to dial it in for home use...

[sluckey]

IMO that PT seems a bit over sized for a 2x6L6. Your bias supply is a good start but since the PT has no bias tap you will need to upsize that 6.8K to something in the 100K to 220K range. But since you are designing a bias supply, maybe consider the Marshall style circuit I put in a recent AB763 power supply...

     http://sluckeyamps.com/phoenix/phoenix.pdf

[Bieworm]

Thanks Steve!! It's the same as the DUAL 50 I built on your docs?

I did the changes...

You think the PT will be a problem? It's a bargain for the quality... Should I go lower in mA ?

[sluckey]

The PT is not a problem but it's not gonna sag much if that's important to you. OTOH, I do like bargains. 

[pdf64]

It’s not clear whether it’s the fuse or the SPST mains switch that you’re intending to put in the neutral feed to the PT? But whichever it is, it seems an ill conceived idea.

[Bieworm]

The PT is not a problem but it's not gonna sag much if that's important to you. OTOH, I do like bargains. 

Fair enough.. but don't you think that 5U4 is giving enough sag? I could always put a 100R or 150R high power resistor after the rectifier? That emulates sag on a SS rectifier.

[Bieworm]

It’s not clear whether it’s the fuse or the SPST mains switch that you’re intending to put in the neutral feed to the PT? But whichever it is, it seems an ill conceived idea.

I took it from the fender schematic.  It should be on the N I suppose.
Maybe add some fuse on the HT supply wires?

I changed the placement of the mains fuse and added a HT fuse. Unless I'm mistaken it should be about right now?

[pdf64]

 
The context of the arrangement Fender used back then was one of ungrounded, unpolarised mains connectors. Which wires were live and neutral was undetermined, hence the benefit for the death cap to be on a ground switch, as a convenience to save unplugging the amp and flipping the plug if there was hum.
A HT fuse would be a good idea. If the standby is amended to a non hot switching arrangement, it can be a quick blow type.

[Bieworm]

in the progress of wiring the amp I wondered something...
as you can see in the pics attached I put the plate resistors of V1 directly at the tube socket. same with the .022uf coupling caps. For the caps I know it's the better position, but am I looking for trouble putting the plate resitors there too?

[sluckey]

in the progress of wiring the amp I wondered something...
as you can see in the pics attached I put the plate resistors of V1 directly at the tube socket. same with the .022uf coupling caps. For the caps I know it's the better position, but am I looking for trouble putting the plate resitors there too?

No trouble. Looks kinda cluttered IMO.

I'm surprised to see a 10µF/350V cap at that filter node. There's a good chance that the B+ will be higher than 350V when you first turn power on.

[Bieworm]

in the progress of wiring the amp I wondered something...
as you can see in the pics attached I put the plate resistors of V1 directly at the tube socket. same with the .022uf coupling caps. For the caps I know it's the better position, but am I looking for trouble putting the plate resitors there too?

No trouble. Looks kinda cluttered IMO.

I'm surprised to see a 10µF/350V cap at that filter node. There's a good chance that the B+ will be higher than 350V when you first turn power on.

The cluster is temporary.  I need to run a wire under there, and then I will tidy it.
You're right about the filter cap. Will change. Thx

[sluckey]

I don't mean your workmanship looks cluttered. I mean the fact that you mounted the caps and resistors directly to the tube socket looks cluttered. Kinda distracts from the neat looks of a turret board. This is just my opinion and what you did will function just fine. 

[Bieworm]

I don't mean your workmanship looks cluttered. I mean the fact that you mounted the caps and resistors directly to the tube socket looks cluttered. Kinda distracts from the neat looks of a turret board. This is just my opinion and what you did will function just fine. 

While designing the layout it was pretty hard to fit it all on the board. I thought a little PTP allure would same the day 😄

[Bieworm]

Amp is finished.  Need to make the combo shell now.
Bias tremolo works super good, no thumping or anything.  Had to tweak the resistor between the tremolo tube and the intensity pot from 470k to 180k to get strong tremolo when the MV is maxed out..

YouTube sound sample:

[Williamblake]

Nice trem and appearantly the right sweep for speed and intensity. Also no thumping? Thanks for adding a sound demo.

[Bieworm]

Nice trem and appearantly the right sweep for speed and intensity. Also no thumping? Thanks for adding a sound demo.

The only extra noise the trem accentuates is a slight hiss that's also there without trem. Nothing abnormal
I think when people build this kinda stuff such as tweeds with tremolo, that normally don't have trem.. it's nice to make a YT video that shows those things exist😄
Maybe there are people that like to have the schematic and layout? I will update them and post en here

[Bieworm]

for those who are interested.. here's the schematic and layout I drew:

[sluckey]

Good looking amp. Great sounding tremolo.

[pdf64]

It’s a bit late now, but what was the perceived benefit of putting the master volume after the cathodyne?

[Bieworm]

It’s a bit late now, but what was the perceived benefit of putting the master volume after the cathodyne?

Most amps I build have an LPT PI and that's where I usually put the MV.  Now with the cathodyne I figured to do the same. Most important thing is that it works great! 🙂

[pdf64]

An LTP has maybe 30dB gain and a nice overdrive character, so if the master volume is put after it, that 30dB can contribute to the depth of the preamp overdrive.

Whereas a cathodyne has maybe -1dB gain.

[Bieworm]

An LTP has maybe 30dB gain and a nice overdrive character, so if the master volume is put after it, that 30dB can contribute to the depth of the preamp overdrive.

Whereas a cathodyne has maybe -1dB gain.

I get that, but all in all it's a very nice and juicy preamp overdrive as is.. it's staying this way 
The only downside is the intensity of the tremolo gets stronger when the MV is dialed back.. but then there is the intensity pot to adjust that.

[Bieworm]

Amp is finished.

[mresistor]

Beautiful sounding and looking creation Bieworm!  Nice playing too..     

[Bieworm]

Beautiful sounding and looking creation Bieworm!  Nice playing too..   

Thx.. I know it's an oddball looking like that, but I try to stay in the same lines when I build. Marshally topology inside, and bogner/matchless style shell..

[mresistor]

Bieworm  what is the song you're playing?

[Bieworm]

Bieworm  what is the song you're playing?

Just something out of the blue. I don't know if it's an excisting song.. I just made it up I guess