Mojotone Studio One

[M Fowler]

Thanks Tony might have a buyer for it so I have my toes crossed.

[M Fowler]

Stay tuned for a 50w version of the Studio One preamp. Got the cabinet ready, chassis chosen, transformers ordered and talking to faceplate guy.

Update faceplates on order.

[ampmike]

Wow Mark,I'm very pleased to see your report on this little amp.I wanted to get a little amp to keep in my bedroom,and not to loud because it's pisses of my dogs when I play the bigger amps.i would like to build a nice little cab for it. This thread was great,thanks so much buddy.You have always been a huge asset to this community ,rock on brother

[M Fowler]

Thanks Mikey it is a good little amp.

[M Fowler]

I had a lot of fun playing through this 1w amp yesterday using my old Gibson "The Paul" into reverb pedal into amp.

This thing needs an effects loop or I guess if your recording you can add delay and reverb when you mic the speaker cab.

Should be able to take the signal from common on relay to send jack then back to relay from return jack.

[M Fowler]

Some have had questions, other kit builders, so I will try document the build better for everyone interested.

Mojotone Relay Switcher.pdf

After I loaded the board I figured out what length of stanchions/standoffs to use when the board is mounted with the relay up as in my photos.

You should determine the length of the wires needed to complete the wiring of the relay board and solder to the relay board before mounting it as I did.
Or you can mount the relay board upside down like Mojotone did in their build (see their photo).

Also, the plastic nut is thick, not leaving much threads to tighten it down. I lost my black plastic nut and had to find a replacement in my junk drawer which was a metal nut that was thinner.

You can also mount the Cliff jack off the relay board and use fly wires to the relay board located anywhere you wish.

NOTE: You don't have to build it the way I did, you can certainly follow the Mojotone layout and their photos uploaded earlier in this thread.

Mark

[M Fowler]

Some more build photos:

IMG_0941.JPG

IMG_0940.JPG

IMG_0939.JPG

IMG_0935.JPG

IMG_0936.JPG

[M Fowler]

Some more build photos:

IMG_0943.JPG

IMG_0942.JPG

[JoeTele]

A friend of mine just built this kit. I brought it up for him on the variac when it was first finished and was blown away by the overdrive channel at low volume. The amp really does just as advertised. I'm a blackface guy, but if I was after something to get me into creamy tube overdrive at a low volume, this would be the amp. The only caveat is that we were not able to get the channel switching to work. That could be lack of knowledge (my friend is just getting into the hobby and I know nothing about relays) or it may have been a bad relay, as we compared the wiring to the diagram again and again. Come to think of it, if you turned the amp on with it set to clean, it would switch to dirty, but then it would not switch back unless you turned the amp off. However, he just added an extra jack, gave each channel its own input, and joined them at the power tube input capacitor via 220k resistors a la Fender blackface (at my advice). I haven't heard it as much, but he really likes the clean channel. We're sort of old school and prefer the amp with out the relay section anyway. If anything, he's finding that the overdrive channel is a little too quiet, but he does have a workshop where he can get away with some volume and, imho, a tendency to find a problem with the current amp so as to be able to remedy it with the next one

Question: are those 220k resistors joining the channels the right way to go? Would different values be better for this configuration?

Thanks!

Joe

[dorrisant]

Just spitballing here... Could you send both signals to the outside terminals of a 500k pot and take the mixed signal off the wiper to your power tube input? Maybe the channel volumes could be balanced with a trimpot...

[M Fowler]

The design of this circuit takes the signal from the input jack to V1B and V2B. The clean signal to relay/PI comes off the plate of V1A. The high gain channel signal to the relay/PI comes off the Master Volume pot wiper.

The relay is only controlling the input of the PI. Most two channel high gain amps split the input signal to the relay and split the signal to the PI to keep channel cross talk down.

Wiring this relay required some investigation as no instructions were provided only the schematic which doesn't mark the relay com, NC, or NO solder tabs neither does the layout.

The layout; however, does show how to wire it all up but you still have to be careful and fully understand where those wires are going to and what for.

Later I found the relay board instructions at Mojotone which I uploaded previously in this thread.

Mark

[M Fowler]

A friend of mine just built this kit. I brought it up for him on the variac when it was first finished and was blown away by the overdrive channel at low volume. The amp really does just as advertised. I'm a blackface guy, but if I was after something to get me into creamy tube overdrive at a low volume, this would be the amp. The only caveat is that we were not able to get the channel switching to work. That could be lack of knowledge (my friend is just getting into the hobby and I know nothing about relays) or it may have been a bad relay, as we compared the wiring to the diagram again and again. Come to think of it, if you turned the amp on with it set to clean, it would switch to dirty, but then it would not switch back unless you turned the amp off. However, he just added an extra jack, gave each channel its own input, and joined them at the power tube input capacitor via 220k resistors a la Fender blackface (at my advice). I haven't heard it as much, but he really likes the clean channel. We're sort of old school and prefer the amp with out the relay section anyway. If anything, he's finding that the overdrive channel is a little too quiet, but he does have a workshop where he can get away with some volume and, imho, a tendency to find a problem with the current amp so as to be able to remedy it with the next one

Question: are those 220k resistors joining the channels the right way to go? Would different values be better for this configuration?

Thanks!

Joe

I had a relay problem when I built the my 50w version of the Studio One. I ended up using the 2nd half of the relay and now it works as intended.

[JazzGuitarGimp]

JoeTele, the two 220k mix resistors don't need to be the same value. If you need more volume out of the OD channel, change its 220k resistor to a lower value (say, 100k for starters), and change the clean channel's 220k resistor to a larger value (say, 390k for starters). Also if you need a little more brightness out of either channel, you can parallel a small capacitor with that channels' mix resistor (250pf to 1nF should work well).

[M Fowler]

Well I see Mojotone has posted the schematic and layout for the Studio One on their website.

Studio-One-SCH.gif

Studio-One-WD.gif

[k9taxi]

I would like to thank M Fowler for posting this information. I've had this kit for months and just now ready to start the build. Some good info in this thread!