JP2C Power tube change to something New but sounds familiar.

[bandit2013]

When I saw that Sweetwater had a new part number for the line of power tubes, STR448. Figured I would try them out. Had placed a pre-order a while ago and they arrived yesterday.

Since I bought my JP back in 2016, it came stock with STR440 gray coded tubes. Awesome to me. Nice and tight, percussive character. All the good stuff in an abundant tube the Mesa carried for all amps for many years.

Since I have many amps in my collection, I moved them around many times. So when it was time to replace the power tubes in the JP2C, the STR440 was no longer available. Bummer. Got the STR443 in the same color code as the STR440s. To be honest, I sort of lost interest in the JP2C with the STR443. They were ok. No fizz either. A bit loose in character with the low end. Actually thought it had too much low end even at gig level. Also tried the STR441 and thought they were lame in the JP2C. Not a bad tube, just was lacking what I liked with the STR440.

The STR448 sound very much the same as the STR440 tube. Just a hair difference in the low end. Slightly less fizz on the top end. Actually they sounded identical to the STR440 that were in the MWDR as I pulled them out to compare since they did not have that many hours of use on them as the one's I held onto from the JP2C.

There is some slight difference in the tone when running the clean channel. I get more chime from the STR448. They also sound bold on the clean channel. Compared to the STR440 they are more warm and not as bold. Where it matters most is on the two gain channels. Yep, very similar to the STR440 in many respects. A bit more low end but still tight. Top end grind is about the same and just a hair less fizz when running a single 8 ohm load. I normally prefer to load the JP2C with two cabs as that was the trick to cut the fizz. The STR443 were wooly. A bit too much low end and loose character. No fizz but lacking what I liked about the STR440. The STR448 delivers the goods much to what I preferred with the STR440 (now out of production, but for how long?) At least my interest in the JP2C has been restored. Will see how well things hold up and if there is any tonal change to speak of after I get some hours on the tubes. This smaller head size does make it challenging to get the tubes installed. The STR448 were just a bit taller than the other tubes. Getting them aligned up in the socket without breaking off the center post was the trick. Since they are TAD tubes, I had issues with those breaking off the center plastic guide post but not in this amp, had used those in the Mark V90 before I converted it to a combo amp. Just thought I would share this.

 

[bandit2013]

Things got a bit better with some use. One huge surprise I discovered with a reduce channel master was that the amp no longer swamped you with too much low end. Did not need to use the Shred mode at all. Say it was more linear in low end with signal strength. Typically the STR440 or the STR443 just swamped you out when attempting to run bedroom levels using full power. CH2, Master V at 10 am. That was cool. Bring the master up to noon, and behold, full body low end that seems to track the high end volume. Go a little further and more of the beast is revealed.

Another thing, ran the gain around 3pm, reduced the bass to about 9am, Mids at 2pm and treble at noon. Presence at 11am. Made some adjustments to one of the GEQ and got this killer sound. Rolled back on the guitar volume and was amazed how good it cleaned up, it almost put the clean channel to shame. For me it is all about the dynamics and how I can use the amp without having to reach for a footswitch. I am quite pleased with the STR448, they seem to be a good match for the JP2C.

 

[bandit2013]

Now that I have some more time on the STR448 tubes, I really like them. However, a stumbling block or brick wall was found to halt my enjoyment of the new STR448 power tubes. When I got home for lunch yesterday, I saw a UPS truck across the street. Thought nothing of it. However, when I looked at the side door I saw a Tag on attempted delivery. Grabbed it and chased the UPS truck. He pulled away just as I pulled into my driveway. Dang it. I was not expecting that delivery for another week. Since the driver did not leave the neighborhood I had a slim chance of getting the delivery. I did say sorry about chasing you down but this delivery was needed to head off the long weekend as I took off on Monday July 3. So what was in the box that got me going after the UPS driver? A full quartet of the STR415 direct from Petaluma. I was surprised to see how the blue ink on the glass would just rub off. I did compare them to the pictures of the real deal I had in my Mark III in 1989. Glass is also etched with the 6L6 USA.

If these are truly the holy grail of power tubes for a Mark amp, I wanted to at least try them once in my lifetime. First hour or two of use was on the lame side. Sounded very compressed. Had to readjust my settings on the amp to see if I would actually like them. Clean was bland and sounded much like the STR440, sort of boxy. Lead channels were predictable and well not as good sounding as the STR448. It was not bad but personally thought the STR448 tubes sounded much better. When I went to go back to the STR448, why not try one pair of STR415 and one pair of STR448? That actually sounded great. Since the tube cage does not fit with the STR448 tubes (too tall), and wanted to get some more burn in on the STR415 tubes to see if my thoughts on the tubes would change after a few cycles of use. Oh yeah. They are blooming nicely. That is good. I have to remember patience is key when it comes to new power tubes that sat on a shelf for decades. The STR448 also had a character change over the first few cycles of use. Those were bright but had plenty of bottom end but eventually bloomed into something of goodness that restored my interest in the JP2C. I lost interest in the amp after switching over to the STR443. Those are not bad, just not epic. Seems to take away what I favored in the JP2C.

Considering I have the same amount of play time on both tubes, the STR448 and STR415 are very similar. STR415 has a tighter low end. I expect there will be some more tonal growth with these in the next few days. The STR448 made me forget I was pushing air though a vertical 212 cab loaded with V30 speakers. They have an airy tone that resembled pushing air with an EV speaker in an open back cabinet. Clean channel never sounded better, lots of bold and crisp bottom, almost piano like, and some chime on top so I had this image of a broken-in Blackbird Alnico speaker. I was impressed how the STR448 broadened the tonal spectrum of the JP2C. Now that the STR415 took over, I am getting a similar sound. Clean is just great. More time on the tubes, more chime in clean, bold low end. Tighter than the STR448 on the bottom end of frequencies. Lead drive is improving considerably. Now I am hearing that Iconic grind I was after. They sound less compressed and are opening up. Very similar to the STR448 but not as loose on the low end. Both tubes sound great. So far all is good. At least there is a more affordable option to the STR415 but can't complain as the cost of the quad was reasonable for a set of NOS tubes in new condition.

I still want to get my hands on a Mark VII. However, the JP2C has new life and loving every minute of it. I did run it with my pair of Badlanders for a short while before the STR415s arrived. Holy Hanna, was that the bomb. The BADs are very close to the JP2C in gain characteristics. They blend very well and complete the wall of sound that keeps me captivated.

I would have to say after using the STR443, I started feeling like the JP2C is just a one trick pony with a lackluster clean channel. I think if the STR443 were the stock tubes in the JP2C from the start, I would be seeking something else or trying different tubes to see if there was more to the amp than I thought. There is. Power tubes do make a difference. I did not notice much of a change with preamp tube rolling though. If anyone has suggestions on preamp tube rolling, NOS or new I would be eager to hear your thoughts and experiences applicable to the JP2C.

 

[bandit2013]

I went back and forth between the STR415 and the STR448. Which do I like better.

It dawned on me when I realized that I was running two vertical 212 cabs, 4 ohm load on the amp. Wonder how much different would it be with 8 ohm load, or single cab?

Before I answer that question, I did have some time with the JP2C on the 412 so that would be an 8 ohm load, but I was also running two Badlanders in parallel for a full wall of sound. Totally awesome sound. However, I do not always want to have a wall of sound, how do the power tubes compare with just a single V212 cab? Well, I can say that the STR415 sounds the best out of all the power tubes I have run in this amp. The STR448 excelled above the STR415 when I was pushing two cabinets but did not seem to keep up with the STR415 on single cab. The STR448 are not bad tubes at all. I think the STR415 sort of stumped me and now I am hooked on those. Bummer, but not a bad thing. I can extend the life of the STR415 if I pair them up with the STR448 but probably will not do that.

 

[Lokair]

Thanks for the write up on 448s , I have been wondering if they were gonna be my next set or not. I have quad set of 440s in the amp now, and know that the life time is going to end one day. So at least the 448s will not be big adjustment to my normal. The 415s probably sound good , but I am of the mind set that if it can't be easily gotten or replicated then its not for me. I think my old Bass amp may still have a set of something similar to the 415s in that amp. the stock tube in my JP2C is the 440, I believe at one point they moved to the 443 as the second JP I looked at had 443s and sounded less alive, same cabinet and everything at the store(so I bought the floor model as it was just bit more alive in my opinion).

 

[bandit2013]

There is another option to the STR448. I had to try them in the JP2C just for kicks after getting the Mark VII. Those STR445 do sound damn close to the STR415. That was a surprise. The pins are on the thick side so getting them installed can be tricky. Odd that it seems when migrating from Class A/B power to the Simul-Class of the VII, the tube swap does not translate well. STR440 sounded really good in that amp, STR415 not so good. STR448 made it boxy. I also tried the STR441 in the JP2C, that is less alive than the STR443 but works very well in the Mark V90. As for desired tubes for the JP2C: STR415, STR448(gray), STR445(green), STR440(gray). I included the bias color that I have tried. The STR415 will be greens as that is the standard for the bias colors used on other tubes. TBH, it was easier to get the STR415 than the STR445 tubes. Two weeks of emails (person was out of the office when I tried to get them so that extended the timeline). The cost is high but typical for a NOS power tube. I have an order in for STR445 tubes, been waiting a while for those to arrive. On backorder and not available anywhere. They are not Russian tubes, they are made in Europe by JJ. I would not spend NOS dollars on some STR440 tubes, the prices for those are nuts.

 

[playingitloud]

There is another option to the STR448. I had to try them in the JP2C just for kicks after getting the Mark VII. Those STR445 do sound **** close to the STR415. That was a surprise. The pins are on the thick side so getting them installed can be tricky. Odd that it seems when migrating from Class A/B power to the Simul-Class of the VII, the tube swap does not translate well. STR440 sounded really good in that amp, STR415 not so good. STR448 made it boxy. I also tried the STR441 in the JP2C, that is less alive than the STR443 but works very well in the Mark V90. As for desired tubes for the JP2C: STR415, STR448(gray), STR445(green), STR440(gray). I included the bias color that I have tried. The STR415 will be greens as that is the standard for the bias colors used on other tubes. TBH, it was easier to get the STR415 than the STR445 tubes. Two weeks of emails (person was out of the office when I tried to get them so that extended the timeline). The cost is high but typical for a NOS power tube. I have an order in for STR445 tubes, been waiting a while for those to arrive. On backorder and not available anywhere. They are not Russian tubes, they are made in Europe by JJ. I would not spend NOS dollars on some STR440 tubes, the prices for those are nuts.

Did you ever do the preamp swapping out on the JP-2C like you had done on the MKV?

I just purchased a JP-2C and I had found the JP-2C was crackling/popping.

I assumed it was a preamp tube and open up the amp and replaced the V1.

Fortunately, the V1 preamp was the problem (no more crackling/popping).

I figure that I should try swapping a few of the preamp tubes out to see if I make the JP-2C sound even better and I remembered you had been doing some tube swapping on your amps and figured you might have some suggestions for specific preamp tubes to take out of the JP-2C (I have a lot of different preamp tubes but not sure which slots would be the best to test them).

The front panel is off right now so it will make it easier for me for the swapping of preamp tubes

 

[bandit2013]

I did explore the JP2C with preamp tube swaps, typical New Sensor offerings From Russia (Reflektor), you know the group, Mullard, Svetlana, Tung Sol, EH, and such. Was curious if they would work out, hell no, wound up with a motor boating sound that kept getting louder over time. Sure even tried the JAN/Phillips 12AT7, nope did not do much but drop the gain, not bad in the phase inverter but again, reduced the volume. As I suspected, the amp was tightly tuned to the Mesa 12AX7 (JJ ECC83s) tube. I had some new unused ones that tested out good (I use an Orante VT1000 valve tester, it helps to find matched triodes). I could not tune the JP2C with change in preamp tubes. There was some effect but usually made it sound worse. Having a good set of Mesa 12AX7 tubes was key. Matched triodes for the phase inverter and V2. That keeps it all kosher.

The most important tubes seemed to be the power tubes. Mine came stock with the STR440 (gray bias color). Those sounded epic. When I had an issue, it was random static like pops, I had thought it may be a preamp tube. Nope. It was the STR440 tubes. Swapped them out with the STR443 as that was what Mesa moved too, did not like them one bit. They were ok but it took the life out of the tone density. I stopped playing through the JP2C in hopes of getting some Mesa STR415 (Sylvania 6L6GC). Then Sweetwater had a new 6L6 tube I never saw before. STR448 made by PSVane for TAD called the Red Base. Well yeah, those were really good. The first set I ordered without requesting a bias color came in grays. I was overly impressed with them in the JP2C, hence the reason for this post. The extended research and efforts panned out with Mesa as they still have inventory of the STR415 but ordering them is not easy as they are not listed on their website or have an actual part number associated with them. That requires going through customer service by email. I had to wait a few weeks as they were not going to be testing and boxing the STR415 at that time. It can be purchased through setting up a work order through email exchange with Mesa, not the customer service that takes all the calls in Nashville (Gibson) as they are not aware of the process or if they exist. The STR415 arrived one week after I got the STR448. Obviously I was going to try them out. For a total cost of $500 you bet I will. NOS STR415, never used except for the Mesa robo test. To be honest, it took a few heat cycles to open those tubes up. Heat cycle meaning actual use and not just letting the cathodes cook without any current flow (in standby). I did give the tubes some time to heat up for the first run. Now that was worthy of note. So far the STR415 are the best I have yet to experience with the JP2C, worth every penny. The STR448 (in gray bias color) were a close second. Hard to decide which I like better. I also tried the STR445 tubes (green bias color) borrowed out of the Mark VII. Actually swapped them with the STR415 to get an idea how they sound in the Mark VII. The STR445 were almost at the same tone density and note definition as the STR415. The STR448 adds a bit more air to the mix, unique characteristic and very musical in all respects. For now, I will use the STR415 and enjoy them while I can. As for change in preamp tubes in the JP2C, it did not get me to a better place. Only power tubes seemed to make a huge difference.

 

[Darkstar2]

I had good luck loading up the JP2C preamp with slightly used vintage tubes, mainly 1950s RCA's. I wasn't happy with the stock JJ preamp tubes and after a good deal of swapping, landed on using vintage (I'm using a new Sovtek LPS in the phase inverter spot.)

 

[bandit2013]

As for the preamp, thought about getting the Tungsram tubes. However, not at $139 each. That would be like $700 just for the 5 preamp tubes. Not ready to spend that much.

The STR415 cost me $500 plus tax and shipping direct from Mesa. Unused NOS, if they have them you need to communicate through email to the mesa customer service. Only Mesa can set up a special work order to have the tubes pulled from their private inventory and processed to be sold.

 

[Darkstar2]

I can't bring myself to spend that much cheddar on 4 power tubes. It's crazy enough I have to spend $200 for the Mesa-labeled TAD redbase tubes...but on your writeup and recommendations, they are on my list to pick up soon.

 

[bandit2013]

I felt the same way. $500 was not that bad for the STR415 tubes, I do not run the JP2C all the time so they will last a while. It was more of a bucket list sort of thing. Was tempted on getting a backup set. May do that but it was a complex process to get them.