I just bought an ADA MP1 in need of repair from JTRules (thanks again John) and decided to go a little further than the repairs. Apparently, this is the most upgraded guitar pre or amp since Mesa Boogie started modding Fender Princetons in the 70s.
Anybody else out there have or intend to mod an ADA MP1?
There is a cool site, http://www.adadepot.com that has a bunch of mods and schematics and tons of info on ADA products. I looked at some of the mods and decided to really tear into the schematics for my own mod.
So I took all the components off of the tube board and ordered newer, better stuff. All resistors are 1% with 1/2W (in 1/4W package) metal film resistors for bias, etc. and 1/4W Holco resistors for the signal path. I upped the value of the coupling caps a little to get a little more bottom and ordered 400V 716P Orange drops to fill this position. All the other caps will be high-temperature and I changed the power supply caps to the highest value that would fit on the board. To get some more gain, I changed the grid stopper (down) and bleed resistor (up) values to maintain the original grid input impedance with more gain. stage 2 got the biggest change, and 3 and 4, just a little change to the extreme of the original resistor's tolerance. I hope that little change would simulate the good old days when one amp out of 100 was out of spec to the good side and it would smoke the other 99.
On the rest of the boards, the rear panel jacks needed fixed, but the original circuit sucks, so I pulled all the components out of the rear input circuit and will just wire direct to the front panel input jack with shunt switches on the jacks for front panel preference. I could saw off 3" of pc board and it wouldn't make any difference! Change 3 amp chips and main power supply caps to kill some noise and ... well, I hope it doesn't go up in smoke.....
ADA MP1 Mods anyone?
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lonewolf
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ADA MP1 Mods anyone?
...Oh, the freedom of the day that yielded to no rule or time...
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lonewolf
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- Posts: 6249
- Joined: Thursday Sep 25, 2003
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I finally worked out all the bugs and does this thing kick butt! I'm glad I sold the Triaxis, because it just didn't cut it.
Here's the mod:
Replaced every component on the tube board using orange drop caps and Holco .1% resistors in the signal path. Replaced the 1/4 watt 5% resistors with 1/2W 1% (1/4 watt sized) resistors. Added silver mica caps where appropriate, all other caps are high-heat, long life. Added fast-recovery, low-noise diodes. Upped the values of the coupling caps for more bottom and adjusted resistor values for maximum quality gain in the 1st gain stage. On the other gain stages, I adjusted the values within 5% of original to maximize gain and simulate that "one out of 100" amp.
On the other boards, I replaced all the opamps with TLO72 and replaced all the power supply filter caps. Removed the rear input balanced circuit altogether and just wired the jacks in parallel with front panel priority.
For EQ, added a trimpot on bass to tune in my cabinet's best bass frequency. Changed the midrange to go +-16db instead of 12db to get a better scoop and changed the treble to a Boogie like flavor.
Also added a 9Vac toroid transformer to provide midi phantom power without a pesky wall wart. I'm testing it thru a Mesa/Boogie 20/20 power amp and a pair of 1984 Mesa/Boogie 1-12" Roadready Thiele cabs.
What's that? I can't hear you. Better try later!
Here's the mod:
Replaced every component on the tube board using orange drop caps and Holco .1% resistors in the signal path. Replaced the 1/4 watt 5% resistors with 1/2W 1% (1/4 watt sized) resistors. Added silver mica caps where appropriate, all other caps are high-heat, long life. Added fast-recovery, low-noise diodes. Upped the values of the coupling caps for more bottom and adjusted resistor values for maximum quality gain in the 1st gain stage. On the other gain stages, I adjusted the values within 5% of original to maximize gain and simulate that "one out of 100" amp.
On the other boards, I replaced all the opamps with TLO72 and replaced all the power supply filter caps. Removed the rear input balanced circuit altogether and just wired the jacks in parallel with front panel priority.
For EQ, added a trimpot on bass to tune in my cabinet's best bass frequency. Changed the midrange to go +-16db instead of 12db to get a better scoop and changed the treble to a Boogie like flavor.
Also added a 9Vac toroid transformer to provide midi phantom power without a pesky wall wart. I'm testing it thru a Mesa/Boogie 20/20 power amp and a pair of 1984 Mesa/Boogie 1-12" Roadready Thiele cabs.
What's that? I can't hear you. Better try later!
...Oh, the freedom of the day that yielded to no rule or time...
Nice. It's amazing what a few good component swaps and adjustments will do.
It reminds me of a Mission CD player a friend of mine bought in the early '80's for $700.00. The only difference between his and my $200 Magnavox was the final audio stage. Mine had electrolytic caps and a cheesy 1458 op-amp. $20 and a few solder connections later I had the same player for $500 less, except for the heavy, weighted housing the Mission came in.
It reminds me of a Mission CD player a friend of mine bought in the early '80's for $700.00. The only difference between his and my $200 Magnavox was the final audio stage. Mine had electrolytic caps and a cheesy 1458 op-amp. $20 and a few solder connections later I had the same player for $500 less, except for the heavy, weighted housing the Mission came in.
... and then the wheel fell off.