Moose wrote:VOX AC15C1 MODS TIPS. First I would like to thank inkmodo.dragon for schematic effort! That's how I discovered this site. I repair and mod tube amps in my area and would like to share what I have found on the AC15C1 that others might find helpful.
1) The Choke Mod--Not really worth it... I bought the Mercury Magnetics 10 henry choke, 100mA, ohmed out at 270. It's a fine iron but there are others that will do just as well for much less, Classic Tone for example. I mounted the choke in the available spot under the ac power in. Removed the board , you dont have to remove any wire connections, and unsolder R80. There is a little indent in the plywood back cover-facing the back of the amp to the right of the ac plug, that can widened a bit and here I installed a quality DPDT slide switch. On one end I soldered the choke the other I soldered R80. The center lugs go to the board. Now I can switch between the stock R80 and the choke( note: I turn the amp off before switching so not to risk a spike in the IC parts). FINDINGS: There is a 20V increase on the plates with the choke. Stock was 325V with R80, 345V with the choke. I 'm using '80s NOS Reflector 7189s that dont mind the higher voltage. There was really no change in tone. There is a very slight difference in headroom due to the higher voltage. The amp was and still is dead quiet with both. I found myself going back to the R80 in the small room I was playing in. I will probably only use the choke on stage playing loud. Knowing what I know now I would not buy the choke. But I do like the choice to use with other tubes.
2) Bright Cap Mods-- It is not nessesary to unsolder the bright caps. Use wire cutters and cut down between the legs and crush the cap and clean off the ceramic. This leaves 2 nice legs to resolder to if you want. On the Top Boost side I dont like the bright cap, and removed C8 and C67 , did the standard bass pot mod soldering a wire from lug 3 to ground(the leg of what was C8). Greatly improved treble and bass response. Done. On the Normal side crush R4. While the board is out for the choke mod, Unsolder the bass pot,and solder in 3 three inch or so wires. The same for the 2 cap legs. Get an Alpha 500KA pot with a DPDT pull switch. Install with the terminals up and solder the wires to their respective lugs. Solder the bright cap wires to the switch lugs closest to the panel and the cap of your choice to the center 2 lugs. I used an 82pF silver mica. Take the time to this so not to deface the panel with a toggle switch.
3) Change to the MOD 8EB2C1B reverb tank
4) It goes without saying to ditch the Chinese tubes. Find the ones that suit your style and that's all this amp needs. I like this amp with no pedals, maybe a chorus on Normal. Just an AB foot switch between channels and done. Save your pedals for your other amps. Just my opinion. Cheers
Hi Moose!
I can't help thinking about the Mods part 2) where you were talking about the R4, did you accidentally meant C4?? (because that's the normal channel bright switch?) Then another question was about the part "Did the standard bass pot mod soldering a wire from lug 3 to ground(the leg of what was C8". Wasn't that actually C67s other leg pointing to ground, where the wire should be soldered??
I am a little confused that's why I need to define these parts of your story?
Thank you for your mod tips!!
