JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

[Tortuga]

The Heyboer Transformers are very rugged but toneful units. Splawn uses all Heyboer stuff, if that gives you any idea. They actually went from Mercury Magnetics TO the Heyboers. A lot of the testimonials and blind test that I have read through all say the Heyboer Iron has great harmonic detail, but does not get annoying or stiff. Apparently the Mercury stuff can be overly stiff and rigid, especially if you play with lower gain.

So, if you just swapped in one of the Heyboers, and stuck with the 6L6s, it would improve reliability and probably tone as well.

Man, this sounds so great - I'm getting really stoked about doing this one!

There are a few resistor changes for the control grids and screen grids for the power tubes. I'll post up the changes when I get home and can check my notebook. Other than that, I gave them the specs for the voltages and the dimensions that you and Sahl posted up, just with the increased current to accomodate the other tubes.

As far as the external bias pot/probes, it will be cheap and simple. Parts should be under $5. I'll try and draw a diagram or something later.

Drill three holes for probes, one for trim pot, solder in a pair of 1R resistors and the extension wires for the trim pot and bias circuit.

I really appreciate you doing this, Jay. This is going to be a great set of mods - such a great combo: being able to swap power tubes to taste, then setting bias without having to crack the chassis open!

Dude here at work won a 50H off of the 'bay......so I might hit him with a tire-iron and take his amp.

HaHaHa - just hope he didn't reduce the chances of you getting a 50 - I'm still crossing my fingers that don't end up with a 100 instead of same amp as me

[Tortuga]

@Jase - I'll see what I can do about a better diagram for you, but it's going to be a few days now - work is getting kinda crazy and the family's starting to tug at me, too. Yes, the voicing mod (w/ 33k) really seemed to affect the response of the upper mids and the character of the amp, rather than a direct impact to the tone, if that makes sense. The first thing I noticed was the tremendous response to pinch harmonics and a somewhat looser feel when doing heavy palm-muting stuff, although I certainly wouldn't call it muddy. Do ya like it? Make sure you tell us about any difference you get with the 39k, since you're experimenting. I still say you'd be better off looking at DPTT switching, which would be a 3-position slide or a rotary, rather than trying to cascade on-off-on switches. Yes, your idea may work, but it's a real tinkerer's solution - what happens when you have both switches in the 'off' position? Then, if you have the first switch in one of the 'on' positions and switch the second switch to 'on', you now have two resistors in parallel, which halves (approximately) your total resistance - not sure what ~15 - 20k is going to sound like...

@Sahl - I think posting up parts lists is a FANTASTIC idea. Drives me crazy trying to figure all this stuff out, especially when I have no idea of the specs like voltage, watts, type (metal-film, ceramic, electrolytic, silver mica, doesn't matter), etc. Also, what clean/crunch switch are you looking to do?

@Kissmyace - can you post some pics of your mod? It definitely should be more than noticable.

@all of you who've done the depth mod - have you seen the additional info about the inline dc-blocker cap that Edge mentioned? It's supposed to help with 'scratchiness' when you adjust the pot. I put one in, and it seems to be all good, but I notice a lot of you don't seem to be doing so - do you hear this problem when you adjust your pot?

@all the new contributors questioning the logic of our 'tinkering' - let us have our fun, eh? Never said we weren't whacked in the head at birth I do remember playing the amp for the first time, thinking - can't wait to get the new tubes. It sounds ok, but I know this could be so much better. New tubes and bias were a HUGE improvement. I like that JCA keeps the cost down with the cheap tubes, 'cause most of their customers end up trying different tubes, anyway. I almost wished I could have bought the amp without tubes and saved even more, but that's just me. After new tubes and bias, the Depth mod gives you such an improvement in the bottom end of the power section and is so cheap / easy to do that it is highly recommended. That said, if you like it the way you found it, then don't fix what ain't broke, eh?

[Kev]

Anyone have any issue with excessive noise? Most pedals pop obnoxiously loud through the amp and I've got a vibe pedal that has an oscillating feedback (in time with the vibe) even when the pedal is not switched on. All these pedals are silent through other amps.

[NOSNOR]

Mini switch is ok - should be a DPDT if you're intending to switch two different values, which I assume you're planning to do. 47k is the stock value and 33k is what CTN and I used, although I've heard 39k makes for good noise, too Don't quote me on this, but I think all the resistors in the signal path are 1/2 watt. CTN went with 1 watt, probably because he's extra brootalz on his stuff and needed the extra security You should be 200% (or is it 400%) covered with a 2 watt resistor, but it's going to be bulky. I wish I could give you a definitive answer - I'm hoping someone will chime in and confim that you'll be ok with the 1/2 watt.

I finally found 1 watt resistors for slope mod, but they are green instead of blue. What is the difference between them? Can I use green ones? Sorry for stupid question, but I really don't know anything about these things

NOSNOR - I'd be happy to send you a set - PM me your address. It'd be more than fair compensation for your generosity (sending me the badge).

GRIMESPACE - thank You very much but You don't have to bother with that. In mean while I did the slope mod with those green (and smaller than original?) resistors. Thanks for recommendation for bias, the improvement is HUGE.

About slope mod, difference between two voicing is more noticeable on clean (NORMAL) chanel than overdrive chanel? Depth mod gives huge difference in sound, but this mod doesn't give that feel of change. Is that because of smaller resistors (they have reccomended values) or something else?
I have feel that some new hum came with this mode (I wouldn't bother if it's just overdrive chanel, but it is also on clean with volume past noon). Can it be from bias, or maybe because of those little green resistors from slope mod? Maybe it's the same amount of hum before those mods and I'm crazy.

I tried google it, but I couldn't find is there any difference between resistors of same value and different size.
Here is a picture of slope with little green resistors:

[Jay]

When posting mods, if possible can we have pictures and a parts list to accompany them? It seems simple enough figuring out what caps and resistors for the SLO mod, but if adding the clean/crunch switch, what switch do I need to look for and how is it wired?

<-- modding n00b

And for reference, my plans and progress:

SLO mod
Simple scoop mod
Normal/Overdrive channel switch
Clean/crunch switch
Overdrive LED indicator (like the HDM)
Depth mod = done

I don't know if edge has a list or not, or if there ever has been one, but I'll put together something in the next few days for these. Then, we could find a way to lump each mod together in the DIY section with a complete list of parts and some instructions.

[Jay]

Anyone have any issue with excessive noise? Most pedals pop obnoxiously loud through the amp and I've got a vibe pedal that has an oscillating feedback (in time with the vibe) even when the pedal is not switched on. All these pedals are silent through other amps.

Are these pedals in the FX loop? Which model do you have?
The 50H and 100H have a pretty hot FX loop, designed for rack-type equipment. The 22H has a lower send level that works with all sorts of pedals, racks, etc. If you can't find a pedal that works for you, check the first page where I mentioned the FX loop mod.

Also, check your tubes and make sure one isn't having an intermittant fault. V3 and V4 both are partially responsible for the FX loop.

[Jay]

Mini switch is ok - should be a DPDT if you're intending to switch two different values, which I assume you're planning to do. 47k is the stock value and 33k is what CTN and I used, although I've heard 39k makes for good noise, too Don't quote me on this, but I think all the resistors in the signal path are 1/2 watt. CTN went with 1 watt, probably because he's extra brootalz on his stuff and needed the extra security You should be 200% (or is it 400%) covered with a 2 watt resistor, but it's going to be bulky. I wish I could give you a definitive answer - I'm hoping someone will chime in and confim that you'll be ok with the 1/2 watt.

I finally found 1 watt resistors for slope mod, but they are green instead of blue. What is the difference between them? Can I use green ones? Sorry for stupid question, but I really don't know anything about these things

NOSNOR - I'd be happy to send you a set - PM me your address. It'd be more than fair compensation for your generosity (sending me the badge).

GRIMESPACE - thank You very much but You don't have to bother with that. In mean while I did the slope mod with those green (and smaller than original?) resistors. Thanks for recommendation for bias, the improvement is HUGE.

About slope mod, difference between two voicing is more noticeable on clean (NORMAL) chanel than overdrive chanel? Depth mod gives huge difference in sound, but this mod doesn't give that feel of change. Is that because of smaller resistors (they have reccomended values) or something else?
I have feel that some new hum came with this mode (I wouldn't bother if it's just overdrive chanel, but it is also on clean with volume past noon). Can it be from bias, or maybe because of those little green resistors from slope mod? Maybe it's the same amount of hum before those mods and I'm crazy.

I tried google it, but I couldn't find is there any difference between resistors of same value and different size.
Here is a picture of slope with little green resistors:

Nice work! Very clean.

1/2w should be fine. Most commercial amps use this value. 1 watt will be plenty for just about all purposes except PSU resistors.

Here's a good link for resistor usage: http://www.aikenamps.com/ResistorNoise.htm

I'll post up some capacitor info from my experiences a little later after I get out of work, too.

[Hipster Salad]

@Sahl - I think posting up parts lists is a FANTASTIC idea. Drives me crazy trying to figure all this stuff out, especially when I have no idea of the specs like voltage, watts, type (metal-film, ceramic, electrolytic, silver mica, doesn't matter), etc. Also, what clean/crunch switch are you looking to do?

I just want to replicate the switching that is on the SLO - be able to have a clean mode, then bypass back to normal on the Normal channel.



BTW anyone have access to gut shots/schematics of the HDM? I'm curious to see how the Depth control is laid out, as well as the LED Overdrive indicator.

[kissmyace]

here's my depth mod(phone pic, sorry)
can't figure out why it doesn't do anything
cap is wired between 1st 2 lugs (left- rt) blue wire from fb on 1st, to sp on 2nd, 2nd/ 3rd lugs bridged together

[Hipster Salad]

pic no worky

[racerevlon]

Got my Jet City Flood Analog Delay pedal today. Sounds awesome, sweet and analog, great pedal. Still does some weird stuff in the loop and works best with the Ebtech Line Level Shifter.

[Jase01]

Um, here's a question. After just biasing my JJ el84's I decided to try a pair of TAD el84 STR's from the tube store.com and paid for a matched pair. Anyway its came with a card that say's because the tubes are matched there's no need to re-bias.
Does that sound right right? I guess,... they'd know, right?

[Jay]

Umm. That's odd. You will still need to rebias. Did you buy the JJs from the Tube Store also? If they have you on record, maybe they got the TADs to have similar ratings to your JJs.

[Promit]

Hey guys, been lurking ever since someone posted a link to here on HC. My new JCA22H with 1x12 arrived earlier this week, and I think it's the perfect amp for me. (Also the first tube amp I've felt like keeping after a few failed attempts to jump from modelers. HT5 suuucks.) However, I do want to make some tweaks and I'm not sure where to start. Remember this thing is brand new, stock tubes, speaker not broken in, etc. I'm playing with the master below 4 too.

Basically two things are bugging me. One, it's too bright. It's not so bad with the presence at zero but I feel like I'm constantly moderating the treble and some of the mids back. Don't know if this is a dialing in problem or what. Number two, there's some fizz in the gain and I'd really like it to be smoother. I'm wondering if I can solve both of these problems with new tubes. I keep hearing that the JJ ECC83S will darken things up, but people complain that they're flat and dead sounding. (What about the long plate ECC803S?) Maybe TungSol 12AX7 would be a better choice? I'm also not sure how things will change as the speaker works in.

[Jay]

Is it the stock JCA speaker?

There are a few things you can try to tame the fizz. Some involve modifying the circuit, or if you don't want to mess with it, just some tube changes will help a bit. If the amp has all the stock tubes, I would recommend a better pair of power tubes. A lot of the JCA owners like the JJs, but I have heard good things about the TADs and MUllards.

JJ preamp tubes will be less fizzy than the stock tubes. They are not dull and lifeless as a lot of people say. They have a rounder tone, and will lean towards creamier leads. I personally like the TungSol reissue a lot, especially in the first spot in most amps. They are fat and meaty. Bigger bottom end than most, but can be bright if you use a lot of them in your preamp. The JJ 803s has a crunchier high end than the ECC83s, and a softer bottom end. Also a good choice for V1 (input) or V5 (phase inverter).

Try some different tubes first, and if you still need something else, we can help you along the way.

[Jay]

@Sahl - I think posting up parts lists is a FANTASTIC idea. Drives me crazy trying to figure all this stuff out, especially when I have no idea of the specs like voltage, watts, type (metal-film, ceramic, electrolytic, silver mica, doesn't matter), etc. Also, what clean/crunch switch are you looking to do?

I just want to replicate the switching that is on the SLO - be able to have a clean mode, then bypass back to normal on the Normal channel.



BTW anyone have access to gut shots/schematics of the HDM? I'm curious to see how the Depth control is laid out, as well as the LED Overdrive indicator.

I'll put together some parts lists together later to help with this. As far as the indicator goes, you should be able to put an LED across the terminals of VT3, right where the label is actually. Just trace back to the footswitch jack wires for where to put the + and - side to.

[demonglory]

Dude here at work won a 50H off of the 'bay......so I might hit him with a tire-iron and take his amp.

HaHaHa - just hope he didn't reduce the chances of you getting a 50 - I'm still crossing my fingers that don't end up with a 100 instead of same amp as me

Jay knows I will turnover either one of my heads to him for modifications...All he has to do is give me the shopping list of stuff.
I'm paying him in home-baked cookies.

[Jase01]

Umm. That's odd. You will still need to rebias. Did you buy the JJs from the Tube Store also? If they have you on record, maybe they got the TADs to have similar ratings to your JJs.

No I didn't. Maybe in future I will to save myself some time/ trouble.
I'm going overseas for a holiday In a day or to and I'm almost not looking forward to the amount of catching up on here i'll have to do!

[Jay]

Dude here at work won a 50H off of the 'bay......so I might hit him with a tire-iron and take his amp.

HaHaHa - just hope he didn't reduce the chances of you getting a 50 - I'm still crossing my fingers that don't end up with a 100 instead of same amp as me

Jay knows I will turnover either one of my heads to him for modifications...All he has to do is give me the shopping list of stuff.
I'm paying him in home-baked cookies.

Mmmm.....cookies.

I know I know, I still have to put those lists together. I'm almost done scouring through lists of Transformers for the conversions. Just making sure I'm not missing any.

[Jay]

Umm. That's odd. You will still need to rebias. Did you buy the JJs from the Tube Store also? If they have you on record, maybe they got the TADs to have similar ratings to your JJs.

No I didn't. Maybe in future I will to save myself some time/ trouble.
I'm going overseas for a holiday In a day or to and I'm almost not looking forward to the amount of catching up on here i'll have to do!

Screw that, man. Have fun on the holiday. We'll still be here when you get back.

As for the tubes, maybe they thought the JCA amps are cathode biased. Come to think of it, I can't think of any other EL84 based amps that are NOT cathode biased.

[Jase01]

I'll look into it when I come home. Give me something to look forward to when I get back. Some new mods hopefully, new switches. I'm a sucker for switches! Lol

[Jay]

I'll look into it when I come home. Give me something to look forward to when I get back. Some new mods hopefully, new switches. I'm a sucker for switches! Lol

Haha. I just put up a mod for the channel-switching in the DIY section.

Channel Switch and Jack mod

Did we decide on where to put the mods index? I'm not sure if we are posting the index in this thread or in a thread in the DIY section. Either way, it will have all the links to each individual mod. I'll post up some lists on the SLO-style switches and an SLO parts list, too.

[Tortuga]

I'll look into it when I come home. Give me something to look forward to when I get back. Some new mods hopefully, new switches. I'm a sucker for switches! Lol

Haha. I just put up a mod for the channel-switching in the DIY section.

Channel Switch and Jack mod

Did we decide on where to put the mods index? I'm not sure if we are posting the index in this thread or in a thread in the DIY section. Either way, it will have all the links to each individual mod. I'll post up some lists on the SLO-style switches and an SLO parts list, too.

Jay - I started putting things like this up on the first page of this thread (see post #3 here). Let me know if this works for you - as each of us starts a mod/DIY thread, let me know here, and I'll post the links in that reference/index area. That way, any of us can quickly find any relevant materials in our quest for better and bigger mods. I'm posting a question up on your mod thread, too...

And speaking of mods, did any of you (besides Jase) see this post over on the HCAF mods thread?. I think I really like the mirror idea, and definitely want to try the lighting to see if it's not too cheesy. Really cool that he was able to wire it off the 6.3v tap.

@Sahl - the clean switching you're wanting to do could be either a SPST (if you want to do the simplest clean switch) or SPDT (if you want to try two values of resistor, as I did). If you want to do the full-on SLO or Decadance switch that Edge11 wrote up, you'll need a DPDT. Let us know if you need more help with that.

There's been a ton of activity in this thread since I've been able to post back - have everyone's questions been answered? Jay's definitely kicking butt on this - really looking forward to seeing parts lists, and especially the bit about capacitors he mentioned!

[Jay]

I have a written list for the parts for the SLO mod, but have to post it up here. I'll link to all the parts you need on mouser, so it makes things easy.

[Jay]

I'll continually post about cap types, but here's a few I can remember. The Mallory and Sozo caps are axial, so fitting them into place is sometimes a chore since the leads come out of the ends. The Orange Drops fit in a little easier since the leads come out of the bottom and just line up a little easier. Plus, they look like the stock caps, so they may fit right on without much fuss.

Quick guide to caps:

Mallory 150: Woody, midrangy tone. Good harmonics, but can be a little loose on the bottom end.

Sozo Regular: Very similar to the Mallory 150, but better clarity and tighter bottom end.

Vishay/Roederstein MKT1813: I have not tried these, but they are axial Polyester caps and I hear lots of good things.

Orange Drop 715p/716p: Tight and Hi-Fi. Sharp highs and bigger bass than most caps. Some people consider them harsh, I say they are "aggressive". Nice harmonics. I also use these in my guitar control cavity.

Orange Drop 225p: Smooth and woody. Tighter bottom than the Mallory 150. If you think the 715/716 is too aggressive, but like the overall tone of the Orange Drops, use some of these to balance the tone.

The Wima caps are really good, but I have not tried them. Their spacing and shorter leads make using them a little trickier, but I hear that they have all of the goods, but none of the weaknesses.

More to come later.