Deluxe Ala Mode

[ron vogel]

Looking for some feed back on my hacked schematic. I have a 6G2 clone existing, and want the LTPI in it.

[pdf64]

It needs a reservoir cap!
I think that the gain / master vol control would be better put after the 220k.
As it is, it will roll off bass as it's turned down.
Have you tested the 'hum balance' control idea? I'm doubtful that it will have much, if any, effect.

[Gingertube]

Ron,
The Gain control needs to shift to the other side of the 220K if you want to implement it as a shunt to 0V control as your schematic suggests, or just wire it as per the volume control and delete the 220K.
Otherwise it should work fine.
I would suggest that the gain control (master volume) is probably not required as the level of overdrive you can get from the 2 stage preamp is very small (unless you use a pedal out front) and the only benefit of changing from a split load (cathodyne) phase splitter to the LTP is overdrive performance. If you really want a Master then consider running the 2nd stage straight into the phase splitter and implement a post PI master using a dual gang pot. That will alllow some additional overdrive from the PI itself.
Here is an example of a post PI master.
Prowess Amplifiers - Orange - Schematics - Tiny Terror


PLus: As pdf64 says it needs a main power supply cap.

Cheers,
Ian

[ron vogel]

The master/gain was going to be a trimpot, I'll just leave it out. So a resivour? Before the 1k I presume? What kind of value should I use? I plan on a 5v4 rectifier. I was told gain would be high without a master, if not I could use a 12ax7 or 12bh7?

[eschertron]

If you're looking to some drive and yet more drive from the amp, I'd suggest upping the mid control pot value. I've used 50k, a happy balance between classic Fender-y cleans on one end and almost tone stack bypassed on the other. Combined with a master volume and the extra gain from the LTP, you should have lots of tonal options, if that's what you're going for.

[ron vogel]

I may just swap in the BF value resistor on top of the pot for the mid control. Already ordered the pot for it and don't have any spares. IIRC I did that on my old Champ but used a 15K pot, so should be OK.

I hope I have an extra filter cap laying around, I have thousands of vintage caps...but old electrolytics I chuck. I keep the bumblebee's, black beauty's, Ajax, and Good-all's only. Doubt I'd want to waste one on a PS!

[Chuck H]

IIRC the 5V4 is an indirectly heated cathode. Also IIRC this will slow the heat up time a tad so inrush current will be gentle. Which is a good thing since you have no standby switch, but more so because it should allow you to use a somewhat larger main filter. I've used 47uf for a 5V4 and no standby switch without any problems.

[ron vogel]

IIRC the 5V4 is an indirectly heated cathode. Also IIRC this will slow the heat up time a tad so inrush current will be gentle. Which is a good thing since you have no standby switch, but more so because it should allow you to use a somewhat larger main filter. I've used 47uf for a 5V4 and no standby switch without any problems.

Yup, I wanted to use this originally for the 6G2 for those same reasons, but by B+ was too high and had to go with a 5Y3.

[ron vogel]

Tried to clean up the schematic, borrowed a little from the 5E3 and Excelsior for the cathode bias. Here's the latest schematic:

[Dave H]

The PI input has two capacitors in series. The 0.047u from the plate of the second triode could be removed.

[ron vogel]

The PI input has two capacitors in series. The 0.047u from the plate of the second triode could be removed.

Yup, that was a mistake. I have a new schematic, think it's getting closer.

[Chuck H]

Schematic looks right. One nitpick is the fuse and power switch should technically both be on the hot side of the mains.

What is the tonal goal? Is this to be a hybrid BF Deluxe/6G2? It's so far from a 6G2 at this point I wouldn't think so. If it's to be more like a BF Deluxe there are a couple of minor circuit tweaks that might get you closer to "that" sound.

[ron vogel]

Schematic looks right. One nitpick is the fuse and power switch should technically both be on the hot side of the mains.

What is the tonal goal? Is this to be a hybrid BF Deluxe/6G2? It's so far from a 6G2 at this point I wouldn't think so. If it's to be more like a BF Deluxe there are a couple of minor circuit tweaks that might get you closer to "that" sound.

6G2 is history. I have an already built amp that is now a 6G2, I want the LTPI...figured if I was loosing the trem, and I already had the holes in the chassis I would go for a BMT tone control, and a BF inspired deluxe output section. The only uncertainty I have is how much gain I'll have to hit the 6V6's with only having the 2 gain stages and the LTPI. Was thinking it might not be a bad idea to try a 12bz7 in the PI if the AT7 doesn't cut it...

I suck at the math, so I did 20uF's for the filters and guesstimated on the b+ resistors. I have 33uF's in there now and I may just use them so I don't have to spend more money on components.