VOX lil' Night Train 2 watt amp

[bigdaddy]

Well Vox now makes a 2 watt amp. Since my friend is a Vox dealer I'll get it cost plus a bit. It will be here next month.

I'm curious if it's a firefly with 2 12ax7s in the preamp or a LT PI one 12ax7 preamp and one for the PI and a 12AU7 power tube. Or something else....like maybe a Princeton type PI and a CF TS.

Does anybody have any info on it? It's 2 watts into a 16 ohm load and 1.5 watts into an 8 ohm.

When I get it I'll try and draw a schematic and make some measurements.

I removed the fixed value CF TS on the Killer ant I have and used a 12AY7 power tube and 5751 preamp tube, the sound is 100X better. Stupid design, they would have better to use the 12AU7 or 12AT7 with parallel triodes in SE and a single 12AX7 set up like a Fender, there's room for a treble and bass pot. The person who designed it did everything bassackwards. For the same price they could have had an outstanding amp not a useless POS.

[stevehoover]

An Old post but I've been hacking my LNT so I thought I would share what I have learned:
The Lil night train circuit looks a lot like it's big brother....
http://www.prowessamplifiers.com/schematics/Vox/Night_Train_Updated.html
Different circuits for sure but it gives some idea of what's going on.
 NOTE: the following mods don't sound much like the existing circuit but I didn't really care.
My goal was a 2 watt blues amp that I didn't have to build from scratch. The VLNT is cool for sure, but not my cup of tea in it's stock hi-gain form, and...I'm running it through an old school 15"alnico speaker in an open backed cabinet.

I've changed the tube set  to: V1 and V2 are now 12AY7 EH's and V3 is a 12BH7 EH. The 12BH7 is just a little meatier than the 12 AU7.
Any additional transformer heat seems to be due to the close proximity of the output tube to the trans. The far side of the transformer stays cool.

I paralleled a 500k CC resistor on R34 and also another on R21. These appear to be the plate resistors for V1a and V1b.
This yields approx 150k instead of the stock 220k..."less fizzy gain". V1a's is on a switch so I can go from BF to Vox tones here.

I also installed a 100k linear pot in place of R10 which looks like the slope resistor for the tone stack.
The alpha pot that I used read 3 ohms to 95.4k, normally I will put a 5-8k resistor in series with the pot but didn't
on this one. I mounted the pot on the left side of the case, between the input and output jacks (as looking from the bottom).
I like an adjustable slope control on most of my amps if they are customs, I feel it allows more flexibility tone wise.
Chimey at one end of the sweep crunchy at the other.

I wired the stock brite cap to a switch and I've changed out the OT for one of Matt's  OT5PP from Musicalpowersupplies.com
The MPS OT has a lot better bottom and more definition at the top.

I'm seriously considering tearing this guy apart and doing a mini 5E3 lite with a pair of 6AK6's

Steve

[jojokeo]

Thanks for the info Steve. In my Firecracker amp (a F-Fly derrivitive) I rarely use a 12au7. I've been mostly using the 12bh7a and occasionally will also use JJ's ECC99 for a bit more power and headroom. These tubes take me over the 1w category but I could care less. The positives I gain far out weigh that limiting factor if it even is one?
I've invested over a year into smaller "power" tube amps and really get a kick out them but as with everything, there's a limit IMHO. Anything less than a SE 6ak6 or = is pretty much useless. May as well just play through headphones or one of those plug in SS mini amps at that point. My Little Giant and Tiny Giant amps actually are fun and still give a cool vibe to things when practicing and are w/in that 2w - 4w target range. Gerald Weber claims "7 full watts RMS" out of using a single 12bh7 and 14w out of using two, but this is his total snake oil BS rattling in his brain. I like Matt's transformers so far as well. I hope he takes suggestions some day and gives better options in his future offerings?

[MadJack]

Bringing this old post back up.

When wiring the MPS OT5PP into the Lil Night Train, which wire wire on the OT5PP goes to which conector on the LNT? The schematic linked above does't fully coincide with the wires on the LNT's OT.

The other mods I've been able to figure out okay.

[MadJack]

I do believe I've got it figured out, just want to make sure I'm right.

• OT #4 Black goes to NT15's output #6/black
• OT #7 Orange goes to NT15's #4/orange (red on LNT)

Both of those leads go to the output PCB in the LNT. The OT5PP's #5/green and #6/yellow are not used.

The input red and white on the LNT,come from terminals right next to each other on the main PCB, which appears to coincide with the NT15 diagram (#2/red and #3/white).

• I'm relatively positive the OT5PP(red/#2) and NT15 (& LNT) #2/red match up
• The NT15 (& LNT) #3/white should go to the OT5PP's #3/blue
• Leaving the NT15's #1/yellow, to be the same as the LNT's black (only remaining wire comming from the main PCB) to match up with the OT5PP's #1/brown.

Here's the NT15 link again:http://www.prowessamplifiers.com/schematics/Vox/Night_Train_Updated.html

Here's the diagram for the OT5PP Transformer:


I would hate to cross up any wires and burn up my new amp, that is why I need someone with more recent knowlege of electronic than mine (nearly 30 years sice I've been inside anything like this or read a schematic), so any help is greatly appreciated.

[MadJack]

I updated the OT5PP's diagram link, it should show up now.

[sluckey]

Here you go...

[MadJack]

I got the OT installed, but the wiring was differnt from above. Hopefully sometime this weekend I'll post up the diagram. The new OT did add some nice depth to the tones with the 12BH7, with a bit more warmth.

Here's a link to the post on MyLesPaul id did asking the same question:http://www.mylespaul.com/forums/squawk-box/184542-installing-output-transformer-lil-night-train.html. No diagram, but I break down the wiring.

[MadJack]

I finally got the diagram drawn out for the installation of the Musical Power Supply's OT5PP Output Transformer:

Descriptions of the connecting points in the photos and captions below.


This is a before shot:

The Output Breakaway is located in the lower left corner. The Plate leads are the red and white leads are the two wires coming across the bottom and connecting to the board on the center right side. The B+ is the black lead paralleling the plate leads, but connecting at the center bottom, next to the large capacitor.

This is the after shot:

The brown and blue wires are the plate wires. A red wire is now the B+. I connected the output black and orange to to the OE's connector as indicated in the diagram.

FYI, C-19 is located between the GAIN pot (on left) and the BRIGHT/THICK switch (red base, top left center). It has been added to a switch so I can cut it in and out as needed.

[MadJack]

I discovered how much the PT would take. The stock type preamp and phase inverter tubes and no more than a 12BH7 in the output. I ran a JJ ECC99 for a while, but left the amp on for a little while, the next time I went to turn it on, it popped the fuse. After a  brief diagnostics, I found the power transformer's heater (6.3V) side read 0Ω. The heat cooked the enamel off the windings.