Baron Von Kale wrote:Ok, I got the JCA20H back today with the BillyZ mod done and I couldn't be happier. I only got to play with it for an hour or so, but yeah, I'm convinced. There's plenty of clean headroom, and it's a very fender-y clean. Obviously not quite a Bassman, but in the ballpark, and it eats fuzz pedals for dinner. Works great with a Pharaoh and a Woolly Mammoth, and I really really need to build a germanium fuzz face for this one. However, what really surprised me was what happens when you turn the preamp gain past five. It's an incredibly nice distortion, way healthier and more pleasant than the stock tone. If you go past nine, it turns into a nearly unusable fuzzface-with-a-dying-battery-meets-farting kinda sound, but at around eight, it's just bloody marvellous!
Since it sounds pretty different, I though it needs to look different as well so I did this:
I have to quote that, just for that pic. Most Jet City amps get cosmeticly modded in a metal/douchy badass sorta way, yours looks SUPER classy. Almost makes me wanna buy one too, just so I could pimp the exact same way
Do you happen to know how does it hold up in a loud rehearsel, through a 2x14?
Thanks guys! Unfortunately, I decided to man up and resolve the nasty farting fuzz problem by trying to bias the amp myself. Took it apart, double checked I knew where the correct measuring points were, rolled the bias pot all the way down and... realised my DMM can't even handle high enough DC voltages. I do remember in what position the pot was, but I've heard horror stories about the sensitivity of bias pots, so now I'm unable to play it before I get someone to bias it properly and I'm completely broke at the moment Yeah, I'm an idiot.
Never had it in a rehearsal myself, but I've lent it in it's stock form to a couple of shows with a V30 loaded 4x12 and it held up with a semi-loud rock band just fine! For bass heavy doom stuff it probably won't quite cut it, though.
Baron Von Kale wrote: I do remember in what position the pot was, but I've heard horror stories about the sensitivity of bias pots, so now I'm unable to play it before I get someone to bias it properly and I'm completely broke at the moment Yeah, I'm an idiot.
I think that's smart...the idiot would've gotten it 'close enough' and just went with it.
Even in stock form, with the right pedal and settings I've been able to get some excellent tones and always felt the amp had good potential but it can just be so tricky to dial in...for me to use it more it would really need more headroom/to handle pedals better and lose the fizz. I bought one exactly because they beg to be modded and can be had used for the price of a new fuzz pedal...unfortunately I recently sourced the parts to do the depth and choke mods and then discovered mine has a bad volume pot
I found the preamp tube swap to knock down some gain works ok but I didn't love what it did to the character of the amp, I'll probably go back and try this again after the mods are done. BVK, I will be really excited to hear more after the bias is sorted and spend some time with the Billy Z mod...if it truly handles a Pharaoh well, I may be sold...
Baron Von Kale wrote: I do remember in what position the pot was, but I've heard horror stories about the sensitivity of bias pots, so now I'm unable to play it before I get someone to bias it properly and I'm completely broke at the moment Yeah, I'm an idiot.
I think that's smart...the idiot would've gotten it 'close enough' and just went with it.
Even in stock form, with the right pedal and settings I've been able to get some excellent tones and always felt the amp had good potential but it can just be so tricky to dial in...for me to use it more it would really need more headroom/to handle pedals better and lose the fizz. I bought one exactly because they beg to be modded and can be had used for the price of a new fuzz pedal...unfortunately I recently sourced the parts to do the depth and choke mods and then discovered mine has a bad volume pot
I found the preamp tube swap to knock down some gain works ok but I didn't love what it did to the character of the amp, I'll probably go back and try this again after the mods are done. BVK, I will be really excited to hear more after the bias is sorted and spend some time with the Billy Z mod...if it truly handles a Pharaoh well, I may be sold...
My thoughts exactly on the stock JCA. After giving it some thought, I think I'm just gonna grab a decent DMM, a pair of new EL84's and try to do it myself. It's not that I'm bothered paying a tech 50€ for biasing, it just really bugs me that it's essentially such a simple procedure and even after spending quite a bit of my youth dabbling with electronics, building pedals and such, I'm still not doing it myself. Some sort of strange DIY fixation, I guess.
I'll let you know how it turns out (unless I manage to electrocute myself, that is), and I could try and record some clips later on
Ok, I went ahead and biased it. Got V5 to exactly 65% which is what I was going for, but V4 was left at 59%, so I reckon the tubes aren't that well balanced. These are the old Shuguangs, since my local shop only had one EL84 in stock. The cleans sound even better now, but the farting problem still persists. I'll try a new pair of EL84's next, but if that doesn't help, I have no idea what to try. The modding job itself looks really clean and everything has been done according to the schematic.
Got it sorted out! Instead of removing the 220k R36, I put it between V2 pin 7 and the preamp gain. Apparently V1 was driving V2 way too hard when cranked, which resulted in the farting. Working perfectly now!
So I just got done doing some of the Billy Z mods. I didn't have the components that needed to be replaced so I just did the parts of the mod that didn't require new components. So far this mod is really great! I am getting cleans up until the gain around 6. So with the mod, some new JJ el84s, and some fuzz and overdrive pedals, the amp is much more usable for me. I also can get this thing a bit louder that stock because I am not running the pre-amp gain so low.
ryan_biggamepedals wrote:So I just got done doing some of the Billy Z mods. I didn't have the components that needed to be replaced so I just did the parts of the mod that didn't require new components. So far this mod is really great! I am getting cleans up until the gain around 6. So with the mod, some new JJ el84s, and some fuzz and overdrive pedals, the amp is much more usable for me. I also can get this thing a bit louder that stock because I am not running the pre-amp gain so low.
Cool to see you here dude, I have a custom EAND I got from you a bit back that barely ever leaves my board!!
Having just read through this thread, I really want to pick one of these up and mod it to be a low gain bass vi/baritone amp with a small bass cab? It'd be perfect for the sort of stuff I do, particularly the ambient stuff and I don't own a low gain/clean amp.
Anyone on here I can pay to do the mod for me? I don't know anything about the inside of amps, and even after reading the whole thread I still think I could mess it up. Like I'll buy it off sweetwater and just ship it to you, paypal you $$$ for time, parts, and shipping it to me?
Iommic Pope wrote:This is the best you've been.
Suffering suits you.
BitchPudding wrote:Let this be written in our history as proof that ILoveFuzz is one tight knit internet family.
ryan_biggamepedals wrote:So I just got done doing some of the Billy Z mods. I didn't have the components that needed to be replaced so I just did the parts of the mod that didn't require new components. So far this mod is really great! I am getting cleans up until the gain around 6. So with the mod, some new JJ el84s, and some fuzz and overdrive pedals, the amp is much more usable for me. I also can get this thing a bit louder that stock because I am not running the pre-amp gain so low.
Cool to see you here dude, I have a custom EAND I got from you a bit back that barely ever leaves my board!!
Having just read through this thread, I really want to pick one of these up and mod it to be a low gain bass vi/baritone amp with a small bass cab? It'd be perfect for the sort of stuff I do, particularly the ambient stuff and I don't own a low gain/clean amp.
Oh rad! Thank you! The Hitchhiker's Guide to the Galaxy one?
It is really a much better amp now. I got mine used for $150 and the overdrive on the amp around 6 or 7 into a 1x15 is perfect for a slightly driven bass.
ryan_biggamepedals wrote:So I just got done doing some of the Billy Z mods. I didn't have the components that needed to be replaced so I just did the parts of the mod that didn't require new components. So far this mod is really great! I am getting cleans up until the gain around 6. So with the mod, some new JJ el84s, and some fuzz and overdrive pedals, the amp is much more usable for me. I also can get this thing a bit louder that stock because I am not running the pre-amp gain so low.
Cool to see you here dude, I have a custom EAND I got from you a bit back that barely ever leaves my board!!
Having just read through this thread, I really want to pick one of these up and mod it to be a low gain bass vi/baritone amp with a small bass cab? It'd be perfect for the sort of stuff I do, particularly the ambient stuff and I don't own a low gain/clean amp.
Oh rad! Thank you! The Hitchhiker's Guide to the Galaxy one?
It is really a much better amp now. I got mine used for $150 and the overdrive on the amp around 6 or 7 into a 1x15 is perfect for a slightly driven bass.
Yeah that one!
Hell yeah, good to know. They're really cheap and my Pro Jr isn't really doing what I want anymore because of how early it breaks up.
Yeah, I'm an idiot.
