Here is my schematic for the two channel Chadwick Series guitar tube amplifier.
The back story on this amplifier goes back to maybe 2005 or so. I had finished the one channel for Krank and I think we built about 200 or so before they really wanted a 'full size' head with two channels. I should have stuck to my guns on the smaller size amp but I really like how this turned out.
The schematic. Please email me with questions on the amp. I'm happy to sugguest mods and help technicians with repairs.
The circuit board layout.
3d Auto Cad minus the chassis.
Picture of the inside.
Can you tell what the different preamp tubes do. And what exactly is the envelope knob. It does stuff, just not sure what. Neat amp, this is my second time owning the same one.
The preamp tubes are extremely important. Nearly all of the distortion and most of the compression comes from them. Lately my favorite tube is the JJ 12ax7 that come in several different flavors. http://www.tubesandmore.com/products/T-12AX7-S-JJ-3 . I highly recommend tube swapping to find your favorite preamp tube. Just be gentle with the tube sockets. The envelope knob (potentiometer) is represented in the schematic as "P2". In this amp there are 3 preamp gain stages. Stage1 => distortion potentiometer => stage2 => envelope potentiometer => stage3 + cathode follower => EQ and master potentiometers. So what envelope gets you is another place to control how hard you are hitting the next stage of gain. My opinion of the envelope knob is that it gives you more compression and less distortion than the distortion knob.
Already found that a JJ high-gain gold pin is an awesome tube in this amp. Are the first two preamp tubes the gain/input or is it the first 3. Interesting about the envelope being a second gain stag
Hi Allan, Thanks for posting. Would you happen to have the schematic for the single channel version that you wouldn't mind sharing? I just got my hands on one of the single channel versions and am curious. Thanks!
It is nearly identical to the two channel minus the second channel. Shoot me an email with any specific questions or mods you are interested in. If it's a popular mod I'll post it here. Do you have the black or red circuit board?
Not sure which board it is, I haven't opened up the chassis yet. I've played around with a bit and I really like the cleaner gain from jumping the FX loop and cutting it back from fully open just a bit. Thanks for the reply!
Hi I have a single channel Chadwick with the black circuit board. I was wondering if there was an easy way to do a lo-gain/hi-gain input, similar to a jcm 800, where the lo-gain bypasses the first gain stage?
Sure, it's pretty easy and I would imagine most amp shops could get it done in about an hour. The amp isn't pre-wired for it in any way so you would be cutting components and drilling a hole, but it isn't too major of an undertaking if you want it done.
Well, I do my own work(been building Valco and tweed-inspired amps for about 5 years now), and am fairly certain I know what it would take, but I'd like to hear your take on it as well. I am not familiar with the art of building and designing around PCB, so any advice/tips would be awesome!
Cool! I would say proceed without fear. That circuit board is near indestructible and even if pad's or traces get destroyed you can still bypass with wires. I recommend using shielded signal wire to and from the low input jack. You have to make the choice between lifting one of the caps off the board and bypassing the trace to the second stage grid, vs cutting that trace to avoid that unused trace acting like an am radio antenna (which in my experience always picks up a country station lol). But do the easiest, lest permanent thing first and see how it works. When you get it done, take some pics and maybe I'll make a user mod section of this blog.
Cool. Thanks! I was planning on cutting the trace after the .022 coupling cap, and right before the incoming lefon the volume pot, and build the R/C network seen in the jcm800 right on the pot. Aound here, we get a bunch Mariachi music when I turn my amp into an AM radio. ;-)
Also, I really like the variable cathode bypass cap(Drive) control. Ingenious!
I cut the trace, added a jack and some shielded wire. I tried adding various bright caps(like in a stock jcm800) but ended up removing them as I didn't like what they did to the tone of either channel, especially with a strat-style guitar. It really opened the amp up for me. I really like using the low-gain with my pedals, and the high gain is WAY more fun when I'm jamming than by myself My particular amp has the Mercury Magnetics transformers in it. Do youknow what the specs may have been on them? I am curious about being able to run 6550's in it.
Played my first show with the head last night. I was really happy with and turned a few heads. Im just disappointed that I told the owner it sounds so good and I'll have to give it back soon. Thanks for your help and a great amp, Alan.
I'll sell you mine, Gavin.
Hi Alan, I love the Chadwick Series One that you designed. I purchased mine new but it has developed an intermittent "static" I had a tech look at it but he could only go so far as the bill was running up. I just now posted this video https://www.youtube.com/watch?v=PSpuWhW2SnU&feature=youtu.be Your thoughts please??? This amp is a keeper, could you please email the schematic? Thanks!
The 1 Channel and the 2 Channel, posted here, are nearly identical circuits (minus the clean channel). I have some ideas about the problem for sure. Email me at allan at achadwick dot com and I'll give you or your tech all the possibly things I can think of. One thing to look for is the middle leg of the Mid EQ knob, on those original black boards, the board is so thick, the trace can actually rub through a layer and ground out the volume. The test for this is to physically bump the unit though, not sure if it matches your scenario.
I'm picking up a combo (2-channel) hopefully this afternoon. It's in slime green, and was installed upside-down. Any idea why?
The heads were all screen printed and designed for a regular head cab, but we got requests for the combo so we built a lot of custom one offs. It was just simpler to mount upside down then to add the extra wood framing support to keep it upright. Slime Green! Definitely a custom request!
Really cool you're still answering questions about this amp. Love it. This is my second combo, running it in stereo with a 66 blackface bassman and am emperor 2x12. Real nice hot rod marshall sound. Are you still building amps?
I'm not actively creating amps. The software gig is on fire for me right now. I really need to look into combining my new software skills with music and amps though and make some other cool devices. I do have one last little amp that never made it to production. It is two nearly identical 3 gain stage channels. Each channel has gain, tone, volume, and mixes into a master volume that controls both channels. All this with only 3 preamps and two output tubes (because of the extra stage freed up by a cathodyne phase inverter). Tony Krank (my mentor) hooked up the power supply after I ran out of time. image: https://dev6.blob.core.windows.net/blog-images/chadwick-two-channel-cathodyne.jpg .
HI, i hope you can help me. When my 2-channel head is set to clean, there is a loud hum when the gain channel volume is turned above 75%. Could this be just a bad pot or a transformer issue? I love this amp and appeciate any advice you could give.
Try to isolate the problem to a component. After each step check for the noise... Unplug the input, if it stops, its the input. Swap the clean channel preamp tube with the dirty (i'll send a pic if needed. Turn the amp off first! And be careful not to bend the pins!), if it stops (or moves to the dirty channel where it would be much more prevalent), it was the tube. How old are the preamps?. You can very gently tap on the tube to see if it makes a 'microphonic' sound. The rest requires opening the head up which should only be done if you know how to NOT GET SHOCKED (take it to a shop). Try replacing the 5532 dual op amp in the effects loop. Try grounding out the audio signal with a .002 uf 600v cap until you have isolated the stage of gain that is introducing the noise. Then test that the power supply for that plate is clean DC without hum (AC). If the DC is not clean, consider replacing the filter cap on that stage. Email me directly for follow up.
Thanks for the reply! I put new tubes in, exchanged op-amps(kudos on the sockets!), and checked for bad components/solder points and nothing changed. The caps did'nt look blown up either. I just gave up today and returned to GC as i bought it used last week. It was from 2005 and the board looked a bit different from your picture here. Clean channle was awesome for old r&b funk and i liked that it was from the mesa/tempe area here. -considereing saving up for a new old stock one!
If you are in the phx area you should totally contact me or any of the other techs from Krank who still do a ton of mods/ repairs. It doesn't sound like much more than a bench fee for such a fix. Sorry you weren't able to fix it, maybe GC will take care of it. Take any pics of the inside?
I just picked up the single channel version and really love it. It sounds amazing and I got it for a steal. I do have a couple questions though, I hope this board is still active. First off, what exactly does the Drive control do? I can tell that the gain and envelope controls both add more preamp gain, but the drive knob does virtually nothing until about 8/10. Then it seems to add more treble and a small gain boost. Is this normal or could something be wrong with that part of the circuit? Secondly, my amp has 6L6's but I thought I read somewhere that these came with KT88's stock. Could i run any other power tubes besides 6L6's? Can someone clear this up for me??
The drive control adds a cathode bypass cap to the second gain stage through a potentiometer. A cathode bypass cap adds distortion and rolls off low end based on the cap value. It is normal that the potentiometer has a 'full effect' location where a degree of turn can have dramatic or little effect on the resulting tone based on the corresponding ohm value. The Chadwick amps never shipped stock with KT88's (we had some custom orders) and the stock output transformer is not to spec for KT88s, however, people have put them in anyway with varying results. I like the sovtek 6l6 dime base tubes, but any 6l6 should be fine. Enjoy the amp! I hope it does the job for you!
Thanks for the reply Allan! Its really cool that you actively respond to people's comments and questions on here. The drive control makes more sense to me now that I know it adds a cathode bypass, just thru a pot instead of a switch. What are some of the more popular mods that can be done to the single channel Chadwick? I have been mainly running the amp clean with pedals for OD/distortion because I find the gainier side of the amp to be a little fizzy/buzzy. I find myself rolling the treble back to almost 3 o'clock at times, to cut out the high end fizz. Are there any mods that will make the amp warmer and more organic?
The tone stack has always been a challenge for me to get the right frequencies. Treble at 3, and mid at 3, are very normal settings for me. Be aware that the mid pot range reaches well into what many would call treble. Good read http://www.gmarts.org/index.php?go=212. On the distortion, the biggest thing you can do is to try different preamp tubes. I like JJ 12ax7 because it is very smooth up to a point then it breaks up in a pleasing way to my ears. You can just swap the first tube. As far as mods go, one of the most interesting values is the 220k after the first gain stage. You can take that anywhere between 220k and 470k and it really makes a huge difference. I think that the 220k is a smoother buttery sound and the 470k get's more 'growly' which is super cool and I think more distortion friendly in some cases. Also you can add a high pass cap in parallel but you might not want the extra treble based on your comments.
Hi Alan, i'm just blown away by your continued effort in supporting everyone like this. I have owned a Krank Nineteen80, but always wanted a Chadwick Series 2, I have an opportunity to get one, but then I read the Nineteen80 was a revised Chadwick and didnt really sound that different, i'd love to hear your thoughts, or even if you had a schematic of the Nineteen80?
Thanks Tyson, I'll have to get with my buddy and mentor Tony Dow (Krank) and see what he cooked up in there. IF he used 3 gain stages then I'm sure I could give you new resistor and/or cap values you could play with. If it's 4 stages it might be more of it's own animal than it's worth. I'll bug Tony, and maybe even see if I can get him to post in here.
Wow thankyou so much! I wish more amp manufacturer engineer/amp builders were like you!
The 1980 is close to the Chadwick and can be modded to it very easy. Or if you want a NEW amp our new "Rival" is like an improved version on the 1980 and in only about 15"X8.5"X8.5" with 6550 or 5881. Check it out at revolutionamps.com WERD
I do love the 1980, I only wish the clean channel had a mid control, which i'm thinking of doing myself. I just wanted a Chadwick for that different flavour, I hope your Revolution amps appear over here in Australia soon Tony!
So Tyson, if you end up with a 1980, just send me some high res pics of the inside and I'll recommend the values to mess around with. If it works out for you we should post it as a user mod.
That sounds fantastic Allan, are you helping out with the new opening Krank again now? Do you have any suggestions for the 1980, it seems to dull out the more i turn the master up, can't really find it's sweet spot, unless the tubes have had it which i kind of doubt
Tony Krank is the man behind the 1980 so I could offer small suggestions if I was able to look at the schematic or high res images, but I would probably only make it closer to the Chadwick. I'm not involved with Krank at all and understand that the company is entirely closed. I hope they call me though if somebody strikes up an amp company and needs one of my circuits!
Hello Allan. I recently purchased a used Krank Nineteen Jr. amp head and found your website by accident when I was doing some Internet research on the Krank Nineteen80 Jr. amp head. I was wondering if Tony Krank has an owners manual or schematic for the Krank Nineteen80 or Nineteen Jr. amp head that he can post on this website? I also noticed that the Nineteen Jr. amp head has a footswitch to control switching between the Kleen and Krank channels. Does the footswitch control the effects loop as well? Any information would be greatly appreciated.
Hi Allan, I'm helping out with Chris's amp. So if we bump it as you suggest, then what? Listen for changes or lack of? Thanks in advance. "One thing to look for is the middle leg of the Mid EQ knob, on those original black boards, the board is so thick, the trace can actually rub through a layer and ground out the volume. The test for this is to physically bump the unit"
Hey Will - I emailed you back with a bunch of tips and am on chat at 4chadwick@gmail dot com most evenings.
I just bought back my two channel chad and am about to install new 6l6's as the gain side is sounding pretty harsh. I'm wondering what bias amount you would suggest? Also, i tried the 1980 and seemed a very different (louder) amp and am happy to be back with the chadwick.
Nick - Glad you like it! I prefer current biasing over voltage or scope and bias both tubes to 68 milliamps. R43 is a 1ohm resistor whose only function is to help take a bias measurement. Put the multimeter leads on each side of the resistor and bias (both tubes) to 68 millivolts (really milliamps converted to voltage drop across the 1ohm resistor) using P5. Note: You can bias between 60-80 milliamps inside traditional 6l6 sepcs (30-40 each) but if you go over 70 make sure you adjust it again after the amp has been on for at least 10-15 minutes.
G'day Allan. First off, I bought a 2 channel Chadwick a couple of days ago and it's one of the sweetest amps I've owned and is serious competition for some big $$$$ boutique amps I've had. My question is, I put a bias probe on each valve and both are reading around the 44ma mark on idle and after reading this comment (about bias between 60-80ma) would like to know if this is too hot? I'm in Australia running 240 volts and that shouldn't make any difference should it? Is it time to Krank it open...Lol Cheers mate!
Thanks for the kind words. I built this because I ran out of money to keep modding and purchasing the boutiques back in the day :) so I'm always happy to compete with the big guys on the simple tube circuits. Ya, I think 44ma might be pushing it per tube, but if the plates aren't glowing it might be within range of those specific tubes. I emailed you some specific bias instructions, which I really should turn into a post.
Running the dime base 5881/6L6WGC I'll sort it out tomorrow and I may just put the external bias pot mod in. That's how Bugera has their bias adjust set and it makes life just that little easier. Cheers for the reply and I'll let you know how I go!
G'day again Allan. Got my amp biased now. It was almost impossible to get a reading off the resistor so I just used my valve probe. Sounded off for a bit then really settled in and sounds even better than before. Concerning the external chassis bias pot what type and value due you use? I couldn't see what the value was. Also the bolts keeping it secure to the chassis is genius compared to screws, makes life a lot easier to remove. Again, cheers for your help, I appreciate that!
Sorry you couldn't get a reading. I always use Fluke Multi-meters and they seem to be the most reliable. Many bias adapters are just fine. I prefer current biasing over voltage and scope but they can all work. The bias component values should be the same as the above schematic. The step list would be something like this.. -Drill a hole to add the new external bias pot - Remove the current bias pot from the pcb and solder wires to the new bias pot. -Drill a hole for a bias port and jump it to the hot side of the bias resistor. Taking measurements would be from the bias port to any ground (outside of a speaker jack). Hope that helps :)
Sure does help Allan. 1 more question, I bought a footswitch and it doesn't change the channel. It has a "mono" type input lead, do I need to swap that for a "Stereo" jack and re-wire the switch? Thanks again for all your help!
The 850pf should be okay, it will slightly add more 'mids' into your 'high' tone. It sounds interesting and could set that amp slightly apart, or if you turn the highs down, you might turn down some desired smoother mids. It's all up to your taste. You can find 500pf in a ton of tone circuits but I wouldn't be afraid of 850pf at all if you like it. 1000v is more than adequate. If it sounds okay I wouldn't worry about it.
-hoping you can help me again. I finally got around to biasing and noticed that guitar center had fixed the gain volume problem by replacing the C10 500pf capacitor with an 850pf one(1000v). Does this make sense and do you think this affected the tone at all?Any benefit to swapping back to 500pf? (thanks for your insights!)
Allan, I've got a quick question about something that I came across today that has me intrigued. I was browsing eBay and searched for your Chadwick amp just to see what they were going for on the used market and came across two amps for sale that are claimed to be Chadwick Series 1's. However, they have some pretty noticeable differences from my Series 1 amp. The head cab for one is not oversized, but fits flush with the ends of the faceplate. Also, they have cloth grill on the front, no push/pull control for the FX loop on the rear panel, separate speaker out jacks instead of a switch, and odd serial numbers. Plus, the input jack is very near the gain knob, where on all the other Series 1 amps I've seen, it has some space between the jack and the first gain control. If you have time, search Krank Chadwick in ebay and two amps by a seller known as lighthousesound should come up. Just wondering if these are your creations or some sort of knock-off!
Oh I remember those versions! Before Tony Krank and I could afford to run all of our own components in quantity we would purchase Sovtek Mig50 and Mig100 amplifiers. We gutted them and hand wired our circuits. I came to Krank after Tony had already started real production runs and I remember staying up all night before NAMM one year making a couple of those for our booth. Those transformers have mid range that will punch a hole in your chest. The full size version of the series one is all box filler, the metal part could fit in a smaller box which was my preference all along. Those amps should be pretty cool and wouldn't deviate very much from the production schematic and would definitely have more interesting bench components than the production run. They are definitely prototypes not knock-offs.
I agree with everyone here. It's pretty cool that you still chat about these amps. I just picked up a Chadwick Series 1 at GC. Serial number CK003. Looks like one of the early ones and all hand built. I'm digging all the tones I can get from it. It'll go from a nice clean to a scooped metal chugging tone with tons of low end. Are there any updates to the circuit from when this early one was released. Mine has the black pcb. I see several online with the red single channel PCB. Thanks much.
Wow Tod, I think you have the 3rd one off the assembly line! I have ck001 :) There is no difference between the red and the black boards as far as traces go but the thickness is different. I forget exactly but the black ones were thicker than the red. The black boards were so thick that you have to be careful about the traces touching the mid and high eq pot legs. There are a ton of mods you can do to that one to weave in and out of Marshall or Fender land. Enoy it!
Allan, Sweet!! I definitely intend to do the low input mod. A good friend of mine came over to play the amp last night and was very impressed. This is a great hidden gem. He has an early JMP four input that I added an MV to and we are getting the same tones out of the Chadwick and we still had more gain to push it into further saturation. It sounds great with my custom opamp based OD pedal. I really dig the loop board in this amp. Do you or any of the previous Krank employees still build that board. I'd like to put them in other amps. Thanks.
I have a couple that I kept for prototyping but I'm sure that Tony ( http://krankamps.com/parts.html ) has many effects loop solutions actively being worked on. I remember him telling me about an all tube effects loop that sounded awesome. I have been writing software and haven't been doing as much tube amp stuff lately.
Hey Allan, I am trying to get a new faceplate designed for my Chadwick head, but custom engraving companies are telling me they cant make me one that says KRANK because it is a trademarked name. Is there anyway you could point me towards a way to contact Tony and ask him permission to get a new logo made? I'd appreciate it a lot. Thanks in advance!
Hi Allan I really like the demos of the Chadwick and the nineteen80. Im buying a 1980 off a friend of mine and was wondering Will the Tung Sol 6550's fit in the 1980? there the coke bottle style im sure you know what the look like lol sorry also in all is the 1980 a good amp to Gig with I play a couple bigger places and have always used a Ampeg Vl502 / 50 watt it also runs 2/ 6550's? thanks man I love the tone of those 2 Krank amps!!
Hi Allan I have just purchased a single channel small box Chadwick w/black tolex serial 3AB 000268 Is this the Sovtek chassis you referred to? I haven't received yet. I purchased it on the basis of the big box vids on YT. How do they compare? Thank-you
It could be! Send me some pics of the inside if you ever break it open. If it is the sovtek chassis those transformers have serious midrange.
Hey Allan, I was wondering if the single channel Chadwick can take KT66 tubes. I know these are 6L6 variants, and that amps with KT66s can usually be swapped to 6L6, but sometimes not vice versa. I'm pretty sure it depends on the plate voltage that the amp runs and how much the tube can handle.
I love tube swapping, it's the cheapest way to basically try new amplifiers. Having said that I wouldn't recommend anything but what it was designed for without considering purchasing an output transformer that is matched with the range of tubes you desire. Is there enough space between the tube sockets? Will the bias supply work without modification? in the past when I used tubes that weren't what my output transformer was designed for it could sound fine at a certain volume but dreadful at higher volumes. I only ruined one gig that way and never crossed my output tranny again :) If you are ready for any headaches they might cause then go for it, Otherwise try the Sovtek 5881 dime base for bubbly compression, and for stiff punchy try the Svetlana 6l6GC. You can stay busy for months just auditioning 6l6/5881 manufacturers. Good luck!
Hello Allan, I recently purchased a Series 1 model. Serial is in the 1000s. I know the NAMM models had Mercury Magnetics iron, but I opened up mine and couldn't find any manufacturer markings on the transformers. Do you recall who made them? Thanks!
Send me a pic. Its either Mercury, Schumacher (Mercury clone), or Sovtek. If the serial starts with CH it shouldn't be a Sovtek. Sovteks were prototypes that we brought to NAMM the first year we introduced the Chadwick. There can't be more than a few of those for Krank.
Which Power Transformer did you use in the Krank Chadwick Series 50 watt model? I've got an amp with a shorted power transformer ...
That sucks that it's shorted out. I have never seen that happen in the transformer but have seen the tubes short out many many times. The fuses should have protected the transformer. Send me a pic of the transformer and I'll let you know what it is. Take that thing to the shop and give it some love.
Is there a way to mod a 2 channel Chadwick to Nineteen80 specs on the gain channel?
Pushing in the drive button takes you most of the way there without even having to open up the amp. It changes the series resistance between the first two gain stages from 220k and no high pass cap to 440k and 250pf high pass cap, JCM800 is 470k with 500pf high pass(*if my memory is correct). I don't have the 1980 schematic in front of me but I think it's all JCM800 which you can look up and start copying. If you don't feel the drive button gets you close enough, cut out C2 (first cathode bypass cap), and swap C4 (second cathode bypass cap) up to .68. There are a bunch more values you can play with but that will get you 90% IMO. If you like it, take some pictures and email me the instructions and I'll post it as a user mod like the guy who added a low input. Good luck!
Hello, a happy 2-channel model owner here. The amp has been going without any actual issues for 8 years now! But can I ask a question I haven't actually figured out so far: What preamp tubes positions are actually used for both channels (V1 probably being the one covered and closest to the input jack)? Like does clean channel also pass through all 4 of them (V1 > V2 > V3 > V4) or is any of them bypassed and in what order? Thank you so much!
Glad you enjoy the amp! The actual tube designation is kind of a thing the schematic capture software does and it doesn't really line up physically. So from the direction of the shielded tube inward it goes like this. 1st shielded 12ax7 (V1) is the gain stages 1 and 2 of the dirty channel, 2nd (V2) is the 3rd stage and cathode follower of the dirty channel, 3rd (V4) is the phase inverter that both channels feed into, and the last tube (V6) toward the power transformer (power button side) is the two stage clean channel. Hope that answers the question.
Oh my, a huge face-palm here. It's been a revelation, to say modestly. I've tried different tube combinations several times, but often felt that supposedly very different and better ones do not change the tone much. For some silly reason, probably based on some random other amps, I assumed that V1 is used by clean and dirty both, then V2, V3 or some combination of their stages is used only for dirty and the last one is the phase inverter. And of course that they would be physically in that order too starting from V1. So I have been using my best tubes in the wrong places and mostly ignored the actual V6 - the most important one for the clean channel.
The main joke here is, that for years I've been using the clean channel exclusively - I'm into this bluesier a bit vintage kind of tone with warm and full clean paired with different often rare overdrives and fuzz-boxes. You know from Hendrix and Sabbath to QOTSA and Black Keys. So my reference tone would be something like a good Bassman or Ampeg V2/V4. Shredding metal is completely not my thing. So sometimes I have felt that I'm still lacking something - that clean channel would need more warmth and that there are still some certain highs in the mix, that I cannot get rid of without making the sound dull. I've been considering some other amps also like Oranges etc. that are typical in that genre, but after a few runs still found that my good old Chadwick is better overall. Can wait to get to the practice room now - fun with tubes awaits. Big thanks!
Hello Mr. Chadwick, First I must say I have no clue what any of these comments/replys are talking about. I am in no way an engineer, merely a west side phx guitar shredder and still couldnt stop reading. Ive never had an amp make the hair on the back of my neck stand up like a series 1 does. You are a legend in my book. \m/
That totally made my day. Thanks!
Hey Allan. I just put a set of Tungsol 12AX7 power tubes in my Chadwick Series 1. Huge improvement from what the original owner had in there. If I'm understanding this correctly, if I experiment with different power tubes like a JJ, which side is considered the #1 position? If I'm looking at the back of the amp, is it left or right? Sorry for the simple question. I know nothing about how amps work. Kickass amp by the way.
Hi Chuck, Glad you are enjoying the amp:) In both the single channel and two channel series the first gain stages inside a 12ax7 preamp tube (not power), are the closest to the input jack. Swapping the first 12ax7 will probably make the most notable difference to you. You can gently swap out 12ax7s (preamp tubes), preferably new ones with straight pins that aren't destroying the tube sockets, without a lot of technical knowledge. But the 6l6 (power tubes), without exception, need to be biased the moment you install them and turn the amp on. Hope that helps.
Thanks Allan. That explains it. It's a killer amp.
Hi Allan. Looking forward to my 2 channel Chadwick arriving this week (Ebay NOS purchase). What are the head dimensions if anyone knows?
nevermind...it came in two days early. Fits atop my Dr Z cabinet perfectly
Thanks Allan and I like what I hear so far! Some questions though that you can maybe answer at your convenience. What tubes and speakers does this amp like best? I put a JJ in V1 that I had laying around and I cant tell whether or not it made any difference. My closed back Dr Z cab is V30/G12h30 loaded and sounds great to my ears, so is it worth exploring alternatives? I'm learning the Overdrive channel needs a little volume to get rid of the fizz. I have it set around 10 o'clock and that's where I can hear the difference. Also, the OD channel LOVES my Keeley Modded SD-1. Takes it right to Modded JCM800 land :-)
That is very subjective, but I like the jjs in the preamps and my favorite output tubes are the dime base sovtek 6l6s. My favorite speaker is an eminence 'Legend' 12 inch after I cut out the felt dust cover and replace it with zurrette. But really, there is no accounting for taste, mine included, so be fearless and try stuff you like.
Hello folks, i'm Brasilian and i'm studying industrial automation, i'd like to know the circuit diference beetween this amp, and the dime amp, thanks
Tony Krank designed the dime amp and the schematic is not available publicly. One major difference is that the dime amp has 4 stages of gain as opposed to 3 stages on the Chadwick.
thanks for the tip Allan! guess i will have to figure it out myself then, any more tips? kkkkkkkkkk
Hi Allan. Im interested in the Chadwick but i have a few questions. Apparently there's a pop when changing channels. Any way of modding that to stop it? Any way of modding the drive to be switchable? Perhaps any other mods you could recommend? Thank you
I mean the boost function and making it switchable. Thanks
On the two channel version of the Krank Chadwick there is no pop or noise when channel switching (if there is, then something is malfunctioning and needs repair). There is, unfortunately, a pop when pressing the "drive" button as Guitar Player magazine pointed out. It's a minor annoyance though since most people don't incorporate changing that setting while actually playing. I do apologize for the design flaw and wish I had worked that out. I would simply try different switches with less 'bounce' and quicker switch time. Regarding making the "boost" (I think you mean "Drive") switchable, you might be confusing the One Channel that has a potentiometer instead of the switch on the two channel. You can turn the Drive on the Chadwick One Channel into a switch. A qualified tech can easily make that mod inside a couple hours. I hope that clears it up a little bit. thx.
Something has happened to my amp i cant figure it out. I got it used off guitar center and after a few days i noticed the power tubes ringing so i to the little panel off the back and tapped on em one of them had an issue so i ordered all new tubes. The second set also had one microphonic tube i sent em back and the next set also has a microphonic tube. But in all this tube switching something has happened to my dirty channel. I get a faint volume from it as it there is no signal going to the power tubes. The green channel sounds normal. Is there a certain tube that controls just the red channel? gain half way, envelope half way and volume up or down i get no volume i can hear a faint sound. I dont understand why the clean channel works normally though
Hey Ron, sorry you are having trouble with the amp. I'll shoot you an email in case I can be a resource for you or your tech. here is my advice. Think about taking it to a tech at this point, it's cheaper than tubes in many cases. Don't forget to bias new tubes, not doing so will destroy the tubes sometimes other components. There is an op app that boosts the effects loop signal as well as mixes the channels on the smaller circuit board.. Replace that with an equivalent dip8 op amp. Think again about taking it to a tech :)
I got it going, thanks for the help! One more question, is there a 12V source i can use to power a set of green LEDs for inside my case? I had a jet city amp that used 12V i believe for the heaters or maybe something else and it was marke don the board "12V" and i used it to power a set of blue LEDs and when the amp was on standby and ON they would glow inside the case matching the power switch. I want to do the same to this amp if there is 12V available. LEDs dont pull hardly anything
Hi Alan, Love this amp! I'm trying to set the bias on my Chadwick series one single channel head but there is no R43. Can you please tell us in this board where we should put the probe. I'm looking to get it at 68mv. Thanks!!!
Allan, By chance do you have a series one schematic? I have your Serial #18 Series one, and i need to do some repairs on it. Much Appreciated man!