I'm hoping to mod my AC15HW1X to be closer to 1960 JMI specs. I could use some advice from people who know these amps better than I do. This amp really seems to be closer to being like a lower-powered AC30 with a top-boost section, not an AC15, so that's what I'll be targeting. Throughout this post, I'll be referencing components by their numbers in the AC15HW1X schematic, not the vintage schematic. See all referenced schematics below or attached to post. I'd like advice on all of this, but the parts that I especially need help deciding what to do will be in blue. For some of these changes, I'm uncertain if I should actually do them, if they'll just make it closer to vintage spec, but decrease the sound quality (like removing the RF-reduction portions from the input). Then again, it's possible that the components don't just reduce RF but also degrade the tone in some way, and should be removed. Proposed Changes: Input Section: Remove C8, C15, C20, C26. Move R40 to connect to input jack, before R37, and similarly move R23 to connect before R18. This will effectively make R18 and R19 act as a single 66k resistor (and same for R37 and R38) I imagine that these differences to the input were mostly added in by Vox for the purposes of reducing RF from getting into the input. Should I actually remove them? They're probably filtering and attenuating the tone in small ways, and maybe I'd be better off without them if I don't really care about small amounts of RF getting in? Grounding Section: Remove C17, C30, R46, and R29. I'm not certain why these components are here. They seem to be isolating the ground from the chassis. My only guess is once again that they are involved in reducing RF, but I don't really know. I don't really know what "Ferrite" resistors are. Is there any reason I shouldn't remove these? Preamp Tube Section (Tube V3): Reduce C5 from 47uf to 8uf. This filter cap value is way too high for vintage specs (like many other filter caps in this amp) Reduce C12 from 100nf to either 47nf or 500pf. I'm uncertain which would be best. In the AC30/6 schematic, 47nf is on the normal channel, and 500pf is on the bright channel (unless I'm reading it incorrectly). I'm leaning more towards 500pf, but I don't really know. Remove R27. This seems to be a pulldown resistor. I don't really know why Vox stuck this in. Reduce R17 to 220k, and move it to after VR3, in between lug 2 of VR3 and the junction of C13 and C14. Once again, I don't know why Vox changed this part's location from the vintage specs. Reduce C14 from 100nf to 47uf Top Boost Section: Reduce C19 from 47uf to 32uf. Reduce C27 from 100nf to 47nf. Phase Inverter Section: Reduce C6 from 47uf to 8uf. Change C7 and C10 from from 100nf to either 150nf or 10nf. The value of these phase inverter coupling caps seem to differ amongst the schematics I was looking at. In the AC30/6, it's 150nf (unless I'm misreading it, it's difficult to tell), and in the AC15 and AC30/4, it's 10nf. I'm leaning towards doing 10nf, not 150nf. Would that be a more vintage Vox sound? Remove R10 and R16? I'm uncertain why Vox added these. My guess is to isolate the tone cut circuit from the master volume circuit, which they added. Though I'm not certain why these resistors are strictly necessary for that. Would it be bad to remove them? They could possibly be attenuating the signal. Change VR2 from B250k to A250k. All of the vintage schematics specify log taper, not linear taper. But is the vintage spec better or not? Maybe making this change would cause there to be more usable positions on the tone cut knob? Or would it make it worse? Power Amp Section: Change R61 and R101 from 3k3 to 1k5. All of the vintage schematics specify 1k5, so I'm not sure why Vox changed this value. Is this okay to change back to 1k5? Change R79 and R104 from 470R to 100R. I'm really uncertain about this, but once again, all of the vintage schematics specify 100R for this resistor, not 470R. Change C74 from 220uf to 50uf? I'm uncertain about this one. It's difficult to read the value in the AC30/6 schematic, but in the AC30/4 and the AC15, this value is 50uf, not 220uf. Filter Section: Change C2 from 47uf to 16uf. Change C1 from 22uf to 16uf. Remove C3 and C4. These just seem to be overkill for filtering, adding onto the values of C1 and C2 respectively. Is it safe to remove these for a more vintage sound? Change the choke from 7h to 15h or 20h? I'm hoping not to do this one because I don't want to have to spend so much money on a vintage style choke, and also how to fit it onto the amp chassis. However, if it would make a significant impact on tone, I will try to do it. Would making this change be important? All of the vintage schematics specify that the choke should be between 10h and 20h, but aren't specific. The AC15HW1X schematic is below (don't pay attention to the pink and green circles, they're someone else's mods): Part 1: Part 2: The vintage schematics have been attached to this post for reference.