Magnatone Stereo Twilighter

[LarBal]

Haven't gotten to far into it, but thought I'd post, bc this seems to be an odd one.

First, what a great sounding amp. It's a 4x6v6, stereo, 2 OTs , 7 preamp/driver tubes , 2x12 speakers, varistors, and a 5 way function switch :

Mono: Effect appears in phase at each speaker.
Stereo: Effect applied out of phase at each speaker.
Wet/Dry: Left speaker is affected, right speaker is unaffected.
Dry/Wet: Inverts the above in the speakers.

The problem is when the amp is in "off" mode. There's a nasty underlying buzz/fuzz trail to the notes. The wet/dry and dry/wet exhibit it as well, as obviously one of the speakers is "off".
The amp sounds fine with vibrato or tremolo(there is also a "FM/AM" switch") in Mono or Stereo mode. I started swapping pre tubes, and when I pull the 2 12au7 vibrato drivers, the amp sounds great in "Off" mode.
I put some new 12AU7s in, and I thought I had solved the problem. Luckily, I got caught up in playing the amp for a while(I told ya it sounds good!!) and after about 20minutes, it went back to the crap sound in the "off" mode.

So this is kinda backwards, eh? I could understand it sounding bad if there was a problem with the fx engaged, but am a bit baffled as to why the "off" position would be affected by the fx driver tubes.

I sent an email to Magnatone, but am certainly not expecting them to handover a schematic

[g1]

So off mode is in regard to FX?
I'm guessing there may be some kind of dsp involved, have you opened it? How about some gut shots.

[LarBal]

So off mode is in regard to FX?
I'm guessing there may be some kind of dsp involved, have you opened it? How about some gut shots.

My bad, I missed some text when I copy pasted from the user manual. Yes, position 1 is "off" on the 5 way clicker :
Off: Bypasses the vibrato circuitry.
Mono: Effect appears in phase at each speaker.
Stereo: Effect applied out of phase at each speaker.
Wet/Dry: Left speaker is affected, right speaker is unaffected.
Dry/Wet: Inverts the above in the speakers

I'll open it up in a bit, and yea, get pics

[g1]

Found some. Looks like there is a board with IC's, could be for the switching at least even if the FX are all analog.
I doubt there will be much you can do without the schematic, you could look up the IC datasheets to determine if they are switching chips and scope the ins and outs.
@ 3m39s in video

[LarBal]

ok thanks

[Randall]

I was in that very same amp last year. I reached out to the guy who designed it and he sent me the portion of the schem I needed, after asking permission. I wish I could remember his name, he has his own line of amps now, but he was very helpful.

[LarBal]

Dave at Magnatone was nice enough to send me the schematic, and after about 30seconds I saw that :
-Its basically a pair of deluxe reverbs, split before the phase inverters, but with no trem loading, as it's the bias wiggle type. Vibrato is single stage oscillator after the 3rd stage.
Reverb is fender too, down to the 3M3/10p. It does have a mid pot, and where the usually 220k channel mixers would be, it's a bit more of a matrix, nonethless a series of voltage dividers
-The section that was unique to the dry only section was only a couple of components. I went right to the board and lo and behold someone on the assembly line forgot to solder in one end of a signal cap on the board

[Randall]

So, that was it?

[LarBal]

So, that was it?

Yep, clean signal was solid after I soldered the loose end

[wsscott]

LarBal-I've been trying to get a copy of the schematic for the new Magnatone Twilighter so that I might modify it a bit and build a simpler amp. Can you share the schematic you got with me? I built a version of the M10A with the help of Sluckey over at the Hoffman Amps site, and it turned our really good. Now I'm looking to build just the amp without the effects. Thanks.

[LarBal]

LarBal-I've been trying to get a copy of the schematic for the new Magnatone Twilighter so that I might modify it a bit and build a simpler amp. Can you share the schematic you got with me? I built a version of the M10A with the help of Sluckey over at the Hoffman Amps site, and it turned our really good. Now I'm looking to build just the amp without the effects. Thanks.

Sure thing here it is. If you want to built something simpler but same, you can build a Deluxe reverb

St Twilighter schematic rev 3 20150609.pdf