The Vibro-Wreck

[roseblood11]

After building some kits, I'm trying to design my own amp...
What do you think about this? It's inspired by Fender Brownface amps like the Deluxe (6g3) or Vibrolux (6g11), but with one more gain stage, similar to a Trainwreck Express or Komet Concorde.
I'll use a power transformer for a 5e3 (from InMadOut, 325V) and a Heyboer TO22 output transformer, with JJ 6V6S tubes and maybe an Eminence Red Fang, in a chassis from an old Carvin Vintage 33.



regards, Immo

[Zozobra]

You might want an extra filter cap in the preamp as it looks like there are 3 inverting stages in series from just one filter node which can cause some instability. It might be fine but be sure to leave space on your board to add one in if needed.

[roseblood11]

Thanx, I'll add that.

Other changes:
- bias connection at the other end of the PT winding
- C27: missing value, 22uF

[Alf]

I noticed you used 100N caps in front of your poweramp. This might be too high and cause too much bass content, I would lower them to 47 N or 33 n ( or even 22N) for , IMHO, a better result.


Alf

[Dave H]

You've only fused one side of the PT B+ winding.

I don't understand what R29 is doing. As drawn it just changes the value of the 6V6 grid resistance by 10%

[d95err]

R35 and R36 should be connected to the vipers of the master volume pot.

[Justin Thomas]

R35 and R36 should be connected to the vipers of the master volume pot.

Great Scott, it seems you've stumbled across Tue REAL secret ingredient that puts the mojo in real Trainwrecks! How could we be missing the vipers all these decades??? :wink:

Justin

[Zouto]

Great Scott, it seems you've stumbled across Tue REAL secret ingredient that puts the mojo in real Trainwrecks! How could we be missing the vipers all these decades??? :wink:

Justin

Yeah, it's definitely true: no vipers no bite......as in Mob Barley's famous song.

[printer2]

Yeah, it's definitely true: no vipers no bite......as in Mob Barley's famous song.

No woman no pie?

[mikepukmel]

Cool, let us know how it comes out, and .... audio clips!!!

[mikepukmel]

Newbie question, Is R25 pot to vary the amount of feedback? What effect would this have on sound?

[mhuss]

More NFB means less distortion and also a tighter, more controlled sound (and vice-versa). Making this adjustable seems like tweak overkill to me, just pick a value.

[roseblood11]

This is the latest version. Please tell me what you think about it!

[SoulFetish]

This is the latest version. Please tell me what you think about it!
[ATTACH=CONFIG]43942[/ATTACH]

Just to give you a heads up. you may want to physically move C19 to the other side of the pot. The way it's currently configured will put DC on the wiper of the pot and you'll get a "scratchy" sound when you turn it.
Also, the value of .047μF will give you an impedance of about 5.24k at 1kHz with the presence at turned all the way down, vs the commonly found value of .1μF–which has an impedance of 4k31 at 1kHz. This happens to be closer to the actual DC resistance of the pot in parallel with the 4k7 resistor (which is anecdotal, as far as I can tell.) You may or may not notice much of a difference, if at all, when the presence is turned all the way down. But it becomes more significant as you increase the presence control. As you increase the presence into the full range of the pot rotation, the impedance at 1kHz more than doubles using .047µF vs .1µF This is where you will hear a significant difference, I think.
Is this making sense? There are people here who can articulate this better than I.
Basically, you don't get as much high end response is the result. This may be something you desire or not.

Also, the frequency of 1kHz was chosen because it's a high frequency as far as guitar is concerned and it's a friendly number to illustrate a point. There may be a better bottom line to use as a meaningful frequency for this.

[Gingertube]

Don't worry too much about C19. You get scratchiness from the pot when there is a DC voltage change across the pot, that is when there is a DC current path. C19 will prevent that regardless of which side of the pot it is. Having said that, having the entire pot resistive element sitting at 0V rather than cathode DC voltage has advantages. It is an easy swap to do.

For some "useful" bling then replace the R46 + C27 bias network on the tremolo oscillator with a green LED (Anode of LED to 12AX7 cathode, Cathode of LED to 0V). That will set about 2.2V bias on the 12AX7 triode, pretty much where it is now, delete the need for a bypass cap (coz LEDS have really low AC impedance) and the LED will flash at the tremelo frequency.
See the Wiz:
The Valve Wizard- Tremolo Oscillator

Cheers,
Ian