Modding an M-101 for the road

[fluid69]

Hi all! Some of you know I have a L-122, a M-101, and a DIY leslie built from an internal unit. My wife and I play in a blues/rock trio. We've been writing alot of songs with the L-122. Since we are a trio, we find it virtually impossible to take the organ to our shows, not to mention we have limited space in our vehicles. Now we have been given the oppurtunity to travel and play shows and festivals out of our area, and mostly out of state. I would be perfectly happy playing something smaller and lighter, but we all pretty much agreed that it didnt have the same mojo when we tried it. So I bought the M-101 with the intentions to "modify" it since I simply refuse to drag my L around or mod it in any way other than the I already have. Ive increased the gain, did kon's "bass all the way down" mod, (moving the lower manual an octave down and the foot pedal to the first octave), and add a reverb control knob.

Basically, I want to do the same mods to the M, as well as build a new case for it thats lighter and more maneuverable. I can handle the bass all the way down mod. I want to make a change to the reverb that I will have a couple of questions about, and I should be able to handle building the case, but I have a couple of questions about that as well.

First, the reason Im building a new case is because I refuse to cut up a piece of beautiful woodwork with a hand rubbed finish. I plan to sell or donate this one to somebody who has an M with a bad case in rough condition. Feel free to PM me if you are interested. I do have access to freight shipping. Im going to start a new post since this one is getting long winded

[fluid69]

The Cabinet

Ive drawn the case in AutoCAD, and plan to have it cutout like I did my DIY leslie and my guitar amp builds. I based my plans on the retroliner chop case. I found a thread on here where this guy had them build a case for his A-100 that has many detailed pics. Ill find the thread and post a link here. Would anyone who has a B3 be willing to post a trace, or a detailed sketch with measurements, of the cutout on the front of the sides above the lower manual? like this:

<a href="http://s210.photobucket.com/user/thomas-80/media/b3-desktop2a-2_zpscohtclne.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/b3-desktop2a-2_zpscohtclne.jpg" border="0" alt="b3 cutout photo b3-desktop2a-2_zpscohtclne.jpg"/></a>

It would be greatly appreciated! I know this detail seems trivial, but Im OCD and want my organ to still be beautful and not a box on a stand. I will post a pic or pdf of my CAD drawing. More to come about the case and the reverb...

[Twiggybush]

Look at this! http://www.harmonycentral.com/t5/Key...1876917/page/2

[fluid69]

reverb

Since I will be running the organ through my leslie and a sub, (I have a crossover in the leslie to send the low freq's to another cab), and I will no longer have the internal speakers, I want to have the reverb on my speaker out. I would like to rearrange the reverb circuitry so that it is similar to how the L is or a guitar amp for example. Has anyone ever done this? Im fairly familiar with tube amps, and could design a preamp, a phase inverter, an output stage, or even a LFO from scratch, but my knowledge of reverb drivers and recovery stages is fairly limited as I have no experiance with building them. The tank in the M is simply put as type 4K in the service manual. After doing some reading and breaking out the Ohm meter, I believe the impedance is 8ohm on the input and 500 on the output of the tank. I have two ideas on how to do this. (1) Split the signal flow of the AO-44 reverb amp into two parts at the phase inverter. Take the signal from the main amp @ V4A the intermediate amplifier, after C9, and feed it into the phase inverter on the ao-44 reverb amp. Then use it output section to drive the 8ohm tank instead of the 8" 8ohm reverb speaker. Then run the output of the tank into the recovery section of the reverb amp, and mix the reverb signal back in @ the expression pedal. My other idea (2) is to use a 12at7 in parallel, (like a guitar amp and also very similar to the way hammond did the L series amps), to drive my tank. Ill post schematics and any tube gurus feel more than welcome to help me pick them apart.

- - - Updated - - -

Look at this! http://www.harmonycentral.com/t5/Key...1876917/page/2

Thats really similar to what Im looking for. Ive seen that organ before. Infact its in my research folder for this project. That's the one where the guy sold plans on ebay to chop the cab and use the wood to make it look like a B3. I like it, it's really cool. I plan on using either 1/2" or 5/8" plywood for my build. I would like to find something in pine or some other lighter wood. I want cabinet grade material, I just need to avoid Birch. I like the looks and quality, but I hate how heavy it is. My orange 4x12 speaker cab is birch and it weighs a ton!

[jdoc]

there are some awesome chop archives on threads here, can't think of the guy's name did a mini B(M)3

Since I will be running the organ through my leslie and a sub, (I have a crossover in the leslie to send the low freq's to another cab), and I will no longer have the internal speakers, I want to have the reverb on my speaker out. I would like to rearrange the reverb circuitry so that it is similar to how the L is or a guitar amp for example. Has anyone ever done this? Im fairly familiar with tube amps, and could design a preamp, a phase inverter, an output stage, or even a LFO from scratch, but my knowledge of reverb drivers and recovery stages is fairly limited as I have no experiance with building them. The tank in the M is simply put as type 4K in the service manual. After doing some reading and breaking out the Ohm meter, I believe the impedance is 8ohm on the input and 500 on the output of the tank. I have two ideas on how to do this. (1) Split the signal flow of the AO-44 reverb amp into two parts at the phase inverter. Take the signal from the main amp @ V4A the intermediate amplifier, after C9, and feed it into the phase inverter on the ao-44 reverb amp. Then use it output section to drive the 8ohm tank instead of the 8" 8ohm reverb speaker. Then run the output of the tank into the recovery section of the reverb amp, and mix the reverb signal back in @ the expression pedal. My other idea (2) is to use a 12at7 in parallel, (like a guitar amp and also very similar to the way hammond did the L series amps), to drive my tank. Ill post schematics and any tube gurus feel more than welcome to help me pick them apart.

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Thats really similar to what Im looking for. Ive seen that organ before. Infact its in my research folder for this project. That's the one where the guy sold plans on ebay to chop the cab and use the wood to make it look like a B3. I like it, it's really cool. I plan on using either 1/2" or 5/8" plywood for my build. I would like to find something in pine or some other lighter wood. I want cabinet grade material, I just need to avoid Birch. I like the looks and quality, but I hate how heavy it is. My orange 4x12 speaker cab is birch and it weighs a ton!

[fluid69]

Hey Jdoc! Ive seen a bunch of them on here. I bet I know the one you are talking about. Is it the one where he put the amp in a seperate box, like an amp head, with the expression pedal on the back, and used a multi-pin connector? I also seen one I think you posted a pic of from yahoo groups maybe? It was pretty cool. Ive thought about putting the amp(s) in another cab, but I would have to use a multi-pin connector. It would probably need to be miltary grade. Im not sure of the voltages without looking at the schematic or testing them. The last time I bought one for a piece of equipment I was Engineering at work, they were pretty pricey from what I remember, and that was about 10 years ago. Maybe they have cheap Chinese knock-offs now. LOL Im going to post a few pics of what Im aiming for.

<a href="http://s210.photobucket.com/user/thomas-80/media/Mobile%20Uploads/attachment-28_zpsodqvtv2g.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/Mobile%20Uploads/attachment-28_zpsodqvtv2g.jpg" border="0" alt=" photo attachment-28_zpsodqvtv2g.jpg"/></a>

<a href="http://s210.photobucket.com/user/thomas-80/media/Mobile%20Uploads/attachment-13_zpsvjpg9t1k.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/Mobile%20Uploads/attachment-13_zpsvjpg9t1k.jpg" border="0" alt=" photo attachment-13_zpsvjpg9t1k.jpg"/></a>

the legs are detachable and just bolt on.

[jdoc]

http://www.organforum.com/forums/sho...t=hammond+chop
also starshiptrooper did a awesome one

[Sweet Pete]

In your first post you mentioned a reverb 'control knob'.Is that an L-pad type control like an A100 you are using instead of the M101 'tabs' to control 'verb on the AO44?
If so,the 'dry' and 'wet' taps are already on the common of the L-pad.:-) I use a 'dry' 12" speaker ground to complete the 'circuit'.When your 'verb starts taking off on you
some carefully placed masking tape on the spring will often tame it down,for you that have plucked your A100/M100 speakers....
My A100 still has all it's speakers,the 'verb speaker has light foam between the paper and the frame to tame it and send the 'verb on to the 147 with more drive.A physical compressor that works.

[fluid69]

http://www.organforum.com/forums/sho...t=hammond+chop
also starshiptrooper did a awesome one

Oh yeah, Ive seen like 2 or 3 videos that steve has posted. He's modded that thing like crazy! The line out/headphine box he has on the left front leg is cool. Im planning on buying my legs from Lowes or Home Depot like he did. The legs Im looking at from lowes are 29" and would be perfect. According to their website they have them in stock. Im dying to go check them out. That's really close to what Im looking to do. I think mine should be even lighter if I can find the right wood etc. of course I wont have the foot pedals or the expression pedal.

Jdoc, who's the circuitry wizard on the forum? Im going to need someone to look at my reverb schematic, after I get it drawn up, to double check me and make sure I didnt miss anything or do something stupid. I have two tube amp guru's, but one of them deals mainly in hifi, and the other actually builds guitar amps from hammond chassis and iron (transformers) but doesnt do reverb, although he repairs all kinds of amps so he might surprise me. maybe I should give him a call?

[fluid69]

Hey Pete!

right now the M is just stock. My L has the control knob, which was an easy mod. The hardest part was drilling the hole! What I want from my M is to be able to send my reverb to my leslie. Ill never understand why hammond used a seperate amp and speaker for the reverb on the M's. They could have just included it in the circuit of the main amp and saved a chassis, a speaker, and a power transformer. They must of already had a butt load of ao-29's or something. A Fender style circuit, (using reverb tanks licensed from hammond), would have been a much more cost effective and elegant solution. The crazy thing is they did it on the L's, why not the M's?!? Im not exactly sure Im following you on the L-pad. do you have a pic or schematic? I know you know your stuff from reading your post on other threads. Thanks pete for chiming in. Any info or solutions you could give me or point me too would be greatly appreciated. All I want is a speaker out for my leslie that has the main signal and reverb, hopefully controllable and loud as heck!

[fluid69]

This is basically what I want the finished project to look like.


<a href="http://s210.photobucket.com/user/thomas-80/media/Mobile%20Uploads/attachment-27_zpsrtkcebj7.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/Mobile%20Uploads/attachment-27_zpsrtkcebj7.jpg" border="0" alt=" photo attachment-27_zpsrtkcebj7.jpg"/></a>

<a href="http://photobucket.com/" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/Mobile%20Uploads/attachment-21_zpsgbmz1it4.jpg" border="0" alt=" photo attachment-21_zpsgbmz1it4.jpg"/></a>

here is my AutoCAD drawing. Im open to any input. Ive based it the retroliner and about two dozen M chops that I have seen. Im still weighing out the pros and cons of putting the amp in a seperate cab with a multi-pin connector.

<a href="http://photobucket.com/" target="_blank"><img src="http://i210.photobucket.com/albums/bb189/thomas-80/m100%20chop%20dim_zpssrh0gns1.jpg" border="0" alt="m100 B3 chop cab photo m100 chop dim_zpssrh0gns1.jpg"/></a>

[Sweet Pete]

I obtain the A100 signal to send to my 147 from the common of the reverb 'dial',which is a larger value in watts than most resistors in the organ.I get my ground from a dry 12" speaker tab.
Tough to duplicate on an M101.Tabs and individual resistors are different from a dial.A few 1/2W 47K resistors might pad the 'verb enough to mix into the rotary.
If you can locate an A100 'verb dial and mounting plate,it will work off an AO44 no issues.
The L100 verb driver stages are in the same chassis,on M types and A100//D100 there are more than one amp chassis.

In a chop you more than likely won't have room.

[Analog]

[COMMENT][/COMMENT]

I obtain the A100 signal to send to my 147 from the common of the reverb 'dial',which is a larger value in watts than most resistors in the organ.I get my ground from a dry 12" speaker tab.
Tough to duplicate on an M101.Tabs and individual resistors are different from a dial.A few 1/2W 47K resistors might pad the 'verb enough to mix into the rotary.
If you can locate an A100 'verb dial and mounting plate,it will work off an AO44 no issues.
The L100 verb driver stages are in the same chassis,on M types and A100//D100 there are more than one amp chassis.

In a chop you more than likely won't have room.

I did the wet and dry mix a couple of weeks ago on my M102. You take a hot signal from the dry speaker put a 47R resistor on the end. Take a hot from the verb speaker and put a 47R resistor on the end, tie the other end of the two resistors together and take the line from that to a Leslie or to a padded line out. There are a couple of pics somewhere in my gallery. I used a solder terminal strip to keep it safe and tidy.

One important point to note is that removing the speakers and replacing them with a load resistor will kill the tone of the organ. In an experiment I found alot of the upper brightness went. Difference was night and day.

[fluid69]

thanks pete and analog!

Analog, basically you just made a resistor mixing circuit for your M, correct? Did you remove your speakers? My DIY leslie is non-powered like a fender vibratone. I use the organs amp to drive it, and disconnect the factory speakers.

That sounds alot easier then what I was planning. My original idea was to redo both circuits to where the reverb was actually part of the main amp circuit, like I was saying, similar to a guitar amp or the L's. I still might try to figure it out. I think it could be done using what is already there more or less. If I can work it out, Ill post the schematic so others trying to do the same thing can find it. I need to print out the schematics for the ao-29 & ao-44 then sit down with a pencil and get it going.

Pete- I downloaded the A-100 service manual last night. Ill take a look at it so I can visualize what you are describing. Im pretty sure I get what you are saying.

Thanks again guys! I think the reverb issue will be the toughest part of this build mentally.

[Analog]

Yes I just used two 47 ohm resistors in a "vee" formation. I think Pete also did this in his A100 with success.

I kept my speakers because they sound good and are good quality "Heppner's". The problem I tried to describe above with a load resistor to replace the speakers is that it kills the organ tone. Pete will back me up on this. I keep my internal speakers and line out (I don't have a Leslie at the moment) running together. Sounds great!

The other thing to consider if you need to lose those speakers for a B case is to actually fit an AO28 like Boyan did with his M100.