I'm building an M15Mk1 in a head configuration. I'm working on the chassis, and suddenly I realized I haven't figured out how to attach the chassis to the cabinet. Or, do you simply push it in and hope it doesn't fall out?
Sort of a silly problem, but I thought some of you guys may have some good tricks or favorite methods of doing this.
The cabinet design will be similar to this one:
http://www.silvatone.bravepages.com/HO/Pdf/Cabinet.pdf
Re: g2 kit
When my kit arrives, while building it, I'll check the signal level and see if it is suitable for an effect's loop and let you know. Even if it isn't maybe a good quality MosFET or Opamp based booster could help I guess.
I don't know the particular details of the G2 kit, but usually, the signal level in a tube amp is too high for line level, not too low.
So, you probably need a gain stage with gain < 1 to bring the signal level down to line level. You would also need a gain stage on the return to bring the signal level up again.
I intend to build something like this for the M15Mk1 I'm building. I will base it on this schematic in the Madamp gallery:
http://forum.musikding.de/gallery/displa…album=124&pos=6
I will build only the loop part, skipping the reverb, relays etc. The idea is to use the 20V tap on the Madamp power transformer to get regulated +/-15V DC (using a voltage doubling rectifier setup). Looks like the G2 uses a torodial power transformer, which may not have a spare tap to use, so you may have to add a separate transformer for the opamp circuit.
If I get it to work, I'll post some info here (it will take weeks or months until I get there though...)
Re: A15 help
maybe a poti parallel on the the out put so I can ajust what goes to the PA. As far as the ls and head box I don't see to much of a problem with making them myself (build a amp so the rest must be hand made, want something original ) Wish me luck!!
I don't know exactly what you mean by a "pot in parallel on the output", but if you do it wrong you could burn the amp AND the PA. Be very careful!
When using a line out, you always need to have a speaker or dummy load connected, or you risk frying the output transformer. The Madamp amps have a safety resistor across the speaker out, but I wouldn't rely on it saving the output transformer for longer periods.
If you look at some Matchless amps, you can see how to wire a line out that will probably work with an A15. They use a 22k resistor from the speaker out and then a 3k3 resistor to ground.
Schematic: https://schematicheavencom.secure.powweb.com/newamps/matchless_spitfire.pdf
Note that the line out signal by itself will sound utterly crap if you connect it directly to a PA. You need some kind of speaker simulation to make it the line level signal sound good.
There is also a risk of ground loops when connecting the line out to a PA (i.e. lots of hum). You may need to isolate the signal using a buffer or transformer to break the ground loop.
A simple (but not DIY) solution is to get something like the Behringer GI-100. It's an active direct box with built-in speaker simulation. You can connect it between the amp and the speaker witout having to use a line out.
I intend to implement a line out on the M15Mk1 I'm building. Possibly a built-in speaker simulator as well. I'll let you know how it turns out.
Re: speakers
Musikding and Martin are busy adding all the new products. They added the kits first, but the parts are supposed to be available soon. I'm sure there will be speakers as well.
I've built the boards and will start wiring my M15Mk1 soon. I'm thinking about skipping the channel switch and use 2 separate inputs instead, using an A/B/Y box to select channels or use both at the same time.
To get both channels in phase, I would like to use inputs on both sides of the PI, just like on the Marshall 18W, i.e. connecting one channel to the cap that is now connected to ground.
Any comments on how this would work? I suppose it should, since it works on the 18W, but then again, perhaps there's some other design consideration with the grounded PI input that I'm not aware of.
Re: Madamp parts sales?
Hi!The parts will all be added to the shop, step by step. Please give me some time
Best regards,
Klaus
Take your time! Didn't mean to rush you 
Madamp sales through Musikding will make it a lot easier to order, and it will be really interesting to see what new kits Martin will come up with...
Will single Madamp parts such as transformers and chassis be available from Musikding, or will it just be the kits and kit accessories?
Re: 25 watt amplifier
where is? ???
http://www.runoffgroove.com (Ruby, Little Gem, Little Gem MkII)
Re: 25 watt amplifier
Hmm... now I see that the project has an option for 12V DC as well. You can use down to 8V DC for the TDA2003, but the output will be lower.
At 12V DC, the output power will be about 4W if you use a 4 ohm speaker, less if you use an 8 ohm speaker.
Since we're a long way from 25W now, you may want to take a look at the LM386 based amps at http://www.runoffgroove.com. They are very simple, runs of a regular 9V battery/eliminator and supposedly sounds great for a solid state amp.
Re: 25 watt amplifier
so, the bridge is optional if i use DC power?
Just remember that 12V AC will be rectified to about 17V DC, so you would need an 18V regulated DC source for it.
It would probably be easier to get a cheap 12V AC transformer. Make sure you get one that can handle at least 15W (1250mA if I calculate correctly).
Re: bad news
As long as there's a market, tubes will be produced, so it's not like tubes will cease to exist.
Hopefully the factory can be moved to another country or region with a more stable economic and legal situation.
Re: 25 watt amplifier
thanx! i found this amp but who is the bridge?http://www.generalguitargadgets.com/pdf/ggg_ca_practice_amp.pdf
It's a rectifier bridge (i.e 4 diodes in a package for rectifying AC to DC).
Re: 25 watt amplifier
First, are you really sure you need 20-30W? The difference between Martins 15W amps and 20-30W should be very small, 6dB or less. The choice of speaker could make a bigger difference.
The http://www.18watt.com site has a variation with a 36W poweramp. There are also lots of people modifying the ax84 amps with bigger poweramps.
At http://www.schematicheaven.com you'll find both schematics and layouts for a lot of Fender, Marshall and other amps.
Lots of places offer kits with 50 or 100W Plexis, JTM45, various Fender models etc.
If you want solid state then there's a 68W amp at http://www.generalguitargadgets.com
Re: channel blending
I've just ordered an M15Mk1 kit (I'll be making the money transfer tomorrow...).
I have lots of ideas on simple channel blending and switching. NOTE: Only *ideas*. I haven't tried any of them, and I'm a newbie to tube electronics.
Marshall often used two 470k resistors to mix the two channels. I suppose this could work on the M15Mk1 too. You would adjust the blend with the volume (Clean) and master (Crunch) knobs.
Another approach would be to remove the Crunch master and replace the channel switch with a 1M pot that blends between the channels.
For channel switching I'm considering simply having one input jack per channel. Then I can use an A/B switch on my pedal board to switch channels. Or, why not use two jacks per channel, allowing you to "jumper" the channels like on the JTM45.
With switching jacks, you could probably figure out a way to make the input connect to both channels if only one cable is plugged in and go to separate channels if both inputs are used.
Lots of ideas, I can't wait! I'd love to hear some comments of this from more experienced amp builders.
Re: A15 kit power increas
Some more info on how amp effect and speakers relate to the output volume (and why you probably don't need more than 15 Watts...)
Re: A15 kit power increas
Is there any way to increase the output to compete with a gig? It will run through most likely marshall 4x12 speaker cabinet.
15 tube watts through a 4x12 should be very loud. Unless you are playing on big outdoor stages or stadiums, it should do fine for a gig.
Your fellow musicians with 100W stacks (with the master volume set below 1) will look at you with envy when you're able to crank it a bit and get some poweramp crunch.
Re:Kit for Tube-preamp stompbox ?
Very interesting, especially for people who may not want the trouble of building/aquiring a cabinet. Probably a good startup project to get into the tube "business".
I would want to be able to use it either as a stompbox, or direct into the poweramp (FX Return) on my regular amp. I can't see any particular difference between those two.
If it is to be used as a stompbox, it would need to be very durable (for safety reasons) and have very good protection for the tubes. In this case, channel and bypass switching could be made with simple stomp switches.
However, most people would probably not want their tube "babies" stepped on and prefer to keep it on top of their amp (rack-mount perhaps?). In this case relay/opto switching and a dual footswitch input (channel, bypass) would be good.
Ideally, the two channels would be independent, each with a switch for clean/crunch/lead. I.e. it should be possible to use 2 lead channels, one clean one lead etc. If relay/opto switching is used, this should be relatively easy to achieve.
Stereo would be useless unless the input was stereo, but then were basically talking two paralell tube preamps and this is simply too complex.
A balanced line out could be useful for direct recording, but then it should probably have a speaker sim as well. This would make things a lot more complex and expensive, so for those who want to direct record it is probably easier to buy (or build) a separate DI box/speaker sim.
