Interesting. I didn't get notes for 102 and just sort of went with what made sense to me. I should have made better notes or taken more photos but as I said, most of the resistors measured very close to the band code. My eyes are getting older, so I perhaps biffed one or two...I definitely used that 180 marked as 150 on V2b and another 150 at what I think is called the slope resistor. Come to think of it, I didn't get any with a 180K band code. That's all OK with me, it sounds pretty great.
I've been going through the SSS boards and have the Reverb and Driver boards all swapped out. There were some substitutions Jelle sent for that one but I have notes. I have also marked the alternates on the layout to share when I'm finished...in case anyone else goes down that path.
So I have a question? are these the resistors you received from Jelle?.. if so what did he say about the slightly mis-matched values he sent?
Tony
I'm not sure if you're asking me, Tommy or both of us. These are the ones I received from Jelle. I asked for a set for this 102 and one for the SSS002 for which I supplied a list. Some of the resistors I asked for in the SSS weren't available and he detailed the differences that he sent. For the 102 package, I got resistors in a bag and IIRC, the only two that are different from what I already had installed were the grid stoppers. I didn't receive an explanation nor do I feel one is necessary. The amp sounds better to me with the replacements.
Interesting. So it sounds like Jelle has the same basic opinion as I do. In general what I have found with respect to resistors in the signal path like the grid stoppers and Drive and Level feeders are the higher the impedance the more high end loss and clarity. There is also a bit of volume loss associated with the higher values as well. I personally don't notice that big a difference until I stray further than the 5% tolerance rating so a few K is not a big deal. I also agree that the type/ brand/ composite resistor is more important than the exact value as the layout/schematic has listed. I will also say that IMO the ODS (or an amp with overdrive) is a bit more sensitive to the types of resistors you use than an amp without overdrive so it depends on the type of amp. This is not to say you still wont notice a difference you will it's just not as obvious or critical especially in OD or boost mode .In the ODS circuit the clean channel feeds the OD so they all play a critical role. The goal in the ODS should be the shift between Clean to OD should be fairly transparent just more gain and OD (all the things associated) and not a big change in tone..
One other thing you should maybe keep in mind is? The high plate amps are generally darker than the low plates, so you may want to go in the other direction with respect to resistor values to make sure the amp doesn't lose too much top end clarity for example, so the type of amp might determine the direction you want to go 5% higher or 5% lower if you don't have the exact values.
Tony
" The psychics on my bench is the same as Dumble'"
talbany wrote: ↑Wed Oct 21, 2020 11:31 pm
Interesting. So it sounds like Jelle has the same basic opinion as I do. In general what I have found with respect to resistors in the signal path like the grid stoppers and Drive and Level feeders are the higher the impedance the more high end loss and clarity. There is also a bit of volume loss associated with the higher values as well. I personally don't notice that big a difference until I stray further than the 5% tolerance rating so a few K is not a big deal. I also agree that the type of resistor is more important than the exact value as the layout/schematic has listed. I will also say that IMO the ODS (or an amp with overdrive) is a bit more sensitive to the types of resistors you use than an amp without overdrive so it depends on the type of amp. This is not to say you still wont notice a difference you will it's just not as obvious or critical especially in OD or boost mode .In the ODS circuit the clean channel feeds the OD so they all play a critical role. The goal in the ODS should be the shift between Clean to OD should be fairly transparent just more gain and OD (all the things associated) and not a big change in tone..
One other thing you should maybe keep in mind is? The high plate amps are generally darker than the low plates, so you may want to go in the other direction with respect to resistor values to make sure the amp doesn't lose too much top end clarity for example, so the type of amp might determine the direction you want to go 5% higher or 5% lower if you don't have the exact values.
Tony
I will undoubtedly be learning about this amp for quite a long time. All I can say is, whatever the reason, the resistor swap (and tube swap) has made a massive improvement to this amp. I still have some noise issues to figure out and it will almost certainly drive me nuts for some time to come.
I mentioned a few days ago that I feared that I made a huge mistake buying the EM12N. It was crushingly bright the first time I had the opportunity to plug into it. Now that the 5751 is back in V1 and with the resistor swap, it sounds crazy good. I still haven't had time to really play and suspect I won't for some time since my whole family is home nearly every minute of every day, but my wife just took our youngest for a walk so I quickly hooked everything up in my living room. I may have one of those accidentally magic amps that feeds back in just the right way all the time. I imagine it could get out of control at higher volumes, but with the pre at 6 and master at 3, any note I hold rings out into feedback after a few seconds when the OD is on...with my PRS AND my strat. When playing the PRS, I was even getting feedback on the clean channel. Not in as many places on the fretboard, and not on the lower strings as much but it wasn't running away and just sounded...great!
Eventually I'll swap that JJ back in just to feel it out, but other than the noise, I think I have this exactly how I want it.
Thanks Ange. I really do appreciate the help and encouragement from everyone here.
There's a little bit of work left to do, still waiting for corners, I think there's a grounding issue with the input jack on the front panel and I'd like to do some kind of logo in the blank space near the power light. I'm also contemplating whether or not it's worth the effort to put a Dumbleator in the amp...or maybe wait until I have the time to try it with a Bluesmaster.
The grill cloth was an adventure. It was fairly successful on the amp and I managed to pretty much get the stitches lined up nearly perfectly. On the speaker cab, I missed a little bit at the corners and the lines are a little wonky. The next time I do one of these, I'll be sure to cut the baffle panels a little smaller...these are TIGHT!
Here's how it's looking today with the tele I built last year. The color is growing on me.
DD14A347-AC6E-45EF-9830-9E0DFC6F1048_1_105_c.jpeg
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The metal corners came in from amplified parts and they're not great. They're supposed to be for 3/4" total panel thickness with a 1/2" radius and well...
The radius is a bit tight and the thickness to the lip is more like 21mm. My BB ply measured 18mm plus or minus a few points and the cloth is 0.020". If you forgive my mixed units, the total thickness is a few thou more than 3/4" or 19.05mm
I don't have proper nails yet , so have the time to do my thing (never being satisfied with anything I make) and come up with another, hopefully better, way. With one daughter working on homework, having dropped my other one off for a socially distance PE class and my wife pulling materials out of her actual classroom I took half an hour to mill out a mold. The 1" ball endmill is well used from making bending dies and an inside corner at 1.250 depth even with only a 0.010" finish pass is a lot of edge engagement, even for my Deckel so the finish isn't what it ought to be, but it's functional for its purpose.
I’m always disappointed with metal ones and I make my own leather, as Mesa ones. I got a template 3D printed and cut them accordingly. Like them much better than metal.
norburybrook wrote: ↑Sat Nov 14, 2020 8:23 pm
I think if you looked that closely at the real Dumble you'd see it's not tight engineering tolerances.
Just get a big hammer and be done...it's a guitar amp at the end of the day not a formula 1 racing engine
M
A bike builder friend of mine likes to say, "it's a bike, man. It's not going into space." But...if I make something, it has to be as good as I'm capable of making it.
A friend of mine has been the steward of this amp for over a year now and he called me last month to tell me that there was a volume drop. He was able to bring it by today for me to check out and I'm hoping I can get a little help. I haven't had very much time with it yet, but I did play it for a few minutes and let it sit powered up for a few hours then played it again. Everything sounds fine, but it does seem quieter than it was. He's been using it with a dumbleator type thing that I made for it and kept the master vol at about 1 o'clock and used the dumbleator to set stage volume. I removed it from the loop to test and from what I can recall, the MV at 1PM was LOUD...it's very tolerable right now. In fact, changing the MV from 0-1 goes about how you'd expect, but changing the MV from 1 to about 7 on the dial really doesn't have much of an effect at all. Once it's past 7, it starts getting louder again.
I've checked voltages on all tubes and everything seems to be in order. I haven't found any cold or dry solder joints, the tone is what I remember...just quieter.
I swapped tubes with a known good set, powered on and let it sit for a minute before checking the bias. I put my meter on the test point for V7 and it was reading 18mV. As I started adjusting the bias pot, V7 started glowing blue/white and the 1R cathode resistor went up in flames. It all unfolded in about a second and was very exciting.
I'd certainly like to make this into a learning opportunity. I'm going to replace the socket and everything affected and once again, any insights or advice as to what I did wrong here would be greatly appreciated.
Vertigo wrote: ↑Tue Apr 04, 2023 4:55 pmI put my meter on the test point for V7 and it was reading 18mV. As I started adjusting the bias pot, V7 started glowing blue/white and the 1R cathode resistor went up in flames. It all unfolded in about a second and was very exciting.
I think you may have had an oscillation going on there, and BTW it takes a lot of current to roast a 1 ohm resistor. If it was a 1W, it would take one full amp to get to it’s rated power. I would check the output transformer winding resistances and voltage ratios on both halves of the primary. I’m also wondering if the low volume issue might have been an ultrasonic oscillation.
Recently I had a bad El34 pop and take out a 1 ohm resistor while amp was being cranked . Replacing the tubes , socket , resistor and cleaning up all the carbon and all is well .
Sounds like new power tubes didn’t help, so probably simply not the case with yours as you weren’t cranking it super loud, but it’s a known problem that driving power tubes hard can cause arcing between pins and can blow out that poor little resistor . Heater to plate is common , and I have heard this can happen within a bad tube . It pays to heat shrink the plates to prevent this happening at the pins.
.In the ODS circuit the clean channel feeds the OD so they all play a critical role. The goal in the ODS should be the shift between Clean to OD should be fairly transparent just more gain and OD (all the things associated) and not a big change in tone.. 
