A #102 Attempt - First amp

[Vertigo]

I received a package of resistors yesterday from Jelle and got to work swapping over the majority of them. There are a few that are a lot of trouble to access so I'll save those for another day but I replaced all the grid resistors except the 220K on V1b, everything on the signal board except the two 220K's hiding under the 0.1uF caps, and the 4.7M on the mid switch. While I was in there, I took the time to swap the bright switch to an on/off/on so I A/B two caps to see how it goes; and I added another input jack on the back for reasons that are specific to the exact situation of my setup and location right now.

As much as I was interested in doing a couple of recordings for science, I didn't have the patience. As such, I completely mucked up the experiment by swapping the JJ E83CC in V1 back to the TAD 5751 I had in there initially. Everyone is my family was home and it was pretty late by the time I finished up, so my only test so far was through the Waza TAE through headphones, but the change was positive. The E83CC would only allow me to turn up the preamp to about 5 before it got hairy and I couldn't get a clean tone that I really enjoyed. With the 5751, I can go up to about 8 and it's just starting to break up.

I'm going to have to play around with the OD a bit. Jelle must not have the 68K value for V2a so it was swapped for a 55K. The OD volume was significantly louder but I was also having a hard time getting enough OD with the drive cranked. I found that if I turn the trimmer way up, I can dial in an incredible OD with the ratio knob but it gets harder to manage the volume level between the clean and OD sections.

hopefully my wife will take the kids out for a walk today and I'll have a little time to hook into the cab I finished over the weekend. I build a closed back 1x12 with an Eminence EM12N and in the short amount of time I was able to use it this weekend I found that the setup is LOUD and quite harsh. I'm still waiting on grill cloth, which I hope will tame it just a little bit but at the moment, I hope I haven't made a huge mistake with these speakers. Eventually I'll build another cab but with an oval for the SSS once I get back to that one and I look forward to hearing the differences between them.

Also, last week with a little assist from my wife, I got the head cab covered with that blue alcantara. The piece I had came about 12mm short of being able to wrap around the cab in one piece, but it would stretch just enough to get a tiny overlap if it was pulled evening along its length. She helped stick down the first corner so we could tension the fabric before sticking it down...but it turned out that the glue application on the fabric itself made it swell enough that it wasn't an issue at all. Still, her help was extremely valuable and it came out pretty OK. I saved the top front corners for last and they turned out to be the worst two! Live and learn.

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[Colossal]

Sweet, man! Looking very good.

[ijedouglas]

Looking good!

[PicknStrum]

Corners look great to me! But I know we are always our own worst critics. The fabric looks fantastic too - good idea throwing those aluminum (?) plates around the front to give a nice clean look.

Glad to hear you generally liked your upgraded resistors - I was super confused about some of the differing values when I got them from Jelle as well but he walked me through them all. Sounds like you're not totally convinced on the 55k, if I'm reading you correctly. That's good to know - I'll have to experiment with a 68k in that spot.

[Vertigo]

Glad to hear you generally liked your upgraded resistors - I was super confused about some of the differing values when I got them from Jelle as well but he walked me through them all. Sounds like you're not totally convinced on the 55k, if I'm reading you correctly. That's good to know - I'll have to experiment with a 68k in that spot.

As far as I can recall, there were only two that were off from what's in the layout...the 68K and the 33K on V1a.

I definitely wouldn't say that I'm not convinced. More like I need to learn how to adjust to compensate for it. I'm still in the "I don't know what I don't know" phase of learning how amps work so please, someone correct me if my assumptions are wrong, but my best guess is that those grid resistors act like attenuators. The way I'm looking at that particular circuit is that you essentially have three resistors in series going into the OD with a total resistance of ~315K...the 68K, the trimmer (set to around 25K) and the 220K. Building on that assumption, I was guessing that resistance can be added via the trimmer to compensate for swapping the 68K for a 55K. It was just while I was fooling with it I realized that turning the trimmer way up gave me a nicely saturated OD...all while on the tele that I built.

Again, I feel like I know next to nothing and am just making guesses. I'd love to be corrected here and shown the correct way to look at this

edit: just a note, the majority of the resistors that Jelle sent are 2%. I measured every value and marked the exact value on each one (with tape.) Only one of them was way out of spec...the color code was for 150K and I measured it just shy of 180K...so I used it in a 180K spot.

edit again: In looking through the resistors I got for my SSS project, I did get a couple of 70K that measured 67 and 69K that could probably do that job perfectly.

[PicknStrum]

Glad to hear you generally liked your upgraded resistors - I was super confused about some of the differing values when I got them from Jelle as well but he walked me through them all. Sounds like you're not totally convinced on the 55k, if I'm reading you correctly. That's good to know - I'll have to experiment with a 68k in that spot.

As far as I can recall, there were only two that were off from what's in the layout...the 68K and the 33K on V1a.

I definitely wouldn't say that I'm not convinced. More like I need to learn how to adjust to compensate for it. I'm still in the "I don't know what I don't know" phase of learning how amps work so please, someone correct me if my assumptions are wrong, but my best guess is that those grid resistors act like attenuators. The way I'm looking at that particular circuit is that you essentially have three resistors in series going into the OD with a total resistance of ~315K...the 68K, the trimmer (set to around 25K) and the 220K. Building on that assumption, I was guessing that resistance can be added via the trimmer to compensate for swapping the 68K for a 55K. It was just while I was fooling with it I realized that turning the trimmer way up gave me a nicely saturated OD...all while on the tele that I built.

Again, I feel like I know next to nothing and am just making guesses. I'd love to be corrected here and shown the correct way to look at this

edit: just a note, the majority of the resistors that Jelle sent are 2%. I measured every value and marked the exact value on each one (with tape.) Only one of them was way out of spec...the color code was for 150K and I measured it just shy of 180K...so I used it in a 180K spot.

edit again: In looking through the resistors I got for my SSS project, I did get a couple of 70K that measured 67 and 69K that could probably do that job perfectly.

That's funny, I went through the exact same procedure - measure and tape their values. Here are the values that differed for me a bit:

20k - this was V1A grid, same as you mentioned (instead of 33k)
55k - this was V2A grid, same as you mentioned (instead of 68k)
330R - he advised me this was a replacement for the 390R b/w 0.1uF and 2.2uF going to presence cap
115k - he advised me this was a great resistor for between the 0.1uF and OD level pot - this replaced the 100k - I got the vibe that this was more of a preference thing but I'm rolling with the expert
180k - he advised me to place this where the 150k is in the layout b/w .005uF and the OD ratio pot. So I got two 180k's and one was to replace the 150k; I'm wondering if that's what your 150k actually is, unless it really is that far out of spec.

As far as I've read / learned, the grid stoppers are mainly to filter off high frequencies but you'd think there would be some attenuation changes with major changes to the values. Especially on a circuit like this in which people indicate that even brands of resistors make a fairly noticeable difference.

EDIT: Now that I'm thinking about it, I'm thinking maybe the 2 higher values he gave me for the OD section maybe compliment the slightly lower values on the V1a grid and V2a grid.

[Vertigo]

That's funny, I went through the exact same procedure - measure and tape their values. Here are the values that differed for me a bit:

20k - this was V1A grid, same as you mentioned (instead of 33k)
55k - this was V2A grid, same as you mentioned (instead of 68k)
330R - he advised me this was a replacement for the 390R b/w 0.1uF and 2.2uF going to presence cap
115k - he advised me this was a great resistor for between the 0.1uF and OD level pot - this replaced the 100k - I got the vibe that this was more of a preference thing but I'm rolling with the expert
180k - he advised me to place this where the 150k is in the layout b/w .005uF and the OD ratio pot. So I got two 180k's and one was to replace the 150k; I'm wondering if that's what your 150k actually is, unless it really is that far out of spec.

As far as I've read / learned, the grid stoppers are mainly to filter off high frequencies but you'd think there would be some attenuation changes with major changes to the values. Especially on a circuit like this in which people indicate that even brands of resistors make a fairly noticeable difference.

EDIT: Now that I'm thinking about it, I'm thinking maybe the 2 higher values he gave me for the OD section maybe compliment the slightly lower values on the V1a grid and V2a grid.

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.

[PicknStrum]

That's funny, I went through the exact same procedure - measure and tape their values. Here are the values that differed for me a bit:

20k - this was V1A grid, same as you mentioned (instead of 33k)
55k - this was V2A grid, same as you mentioned (instead of 68k)
330R - he advised me this was a replacement for the 390R b/w 0.1uF and 2.2uF going to presence cap
115k - he advised me this was a great resistor for between the 0.1uF and OD level pot - this replaced the 100k - I got the vibe that this was more of a preference thing but I'm rolling with the expert
180k - he advised me to place this where the 150k is in the layout b/w .005uF and the OD ratio pot. So I got two 180k's and one was to replace the 150k; I'm wondering if that's what your 150k actually is, unless it really is that far out of spec.

As far as I've read / learned, the grid stoppers are mainly to filter off high frequencies but you'd think there would be some attenuation changes with major changes to the values. Especially on a circuit like this in which people indicate that even brands of resistors make a fairly noticeable difference.

EDIT: Now that I'm thinking about it, I'm thinking maybe the 2 higher values he gave me for the OD section maybe compliment the slightly lower values on the V1a grid and V2a grid.

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.

I had to go back and double-check to make sure I had the 150k slope and I do. While I was at it, I looked at the band code differences between a 150k and a 180k. At first I had a small panic moment that I measured wrong and was missing either a 150k or 180k but there is a tiny difference. There is a green band on the 150k and a gray (that looks green) on the 180k. Crazy hard to tell though. Sounds like you got them figured out anyway. Glad it sounds good - I'm super pumped to start chipping away on mine.

[Vertigo]

I had to go back and double-check to make sure I had the 150k slope and I do. While I was at it, I looked at the band code differences between a 150k and a 180k. At first I had a small panic moment that I measured wrong and was missing either a 150k or 180k but there is a tiny difference. There is a green band on the 150k and a gray (that looks green) on the 180k. Crazy hard to tell though. Sounds like you got them figured out anyway. Glad it sounds good - I'm super pumped to start chipping away on mine.

I went back and forth on the green vs. grey band and you're almost certainly right about the mixup. I even got my 20x magnifier and they both looked like the same shade of olive green to me. Anyhow, I can't immediately decode the bands so I'm in the habit of doing my best to decode them, measure to verify and then I flag them to make sure I grab the right ones.

I just grabbed a flashlight and checked them again...they both look olive green to me.

[norburybrook]

well done nice job. Are you going to put the proper 'Dumble' metal corners on your amp? They hide a lot of things and serve as protection too. Your corners look great. I do like the traditional look with the corners myself.


Regarding resistors, Changing with different values doesn't seem to me like a very scientific way of determining the difference in sound between brands. I mean 150 to 180 k on the slope resistor will change the frequency of the tone stack, albeit slightly it's still a difference of 20% in value, surely when comparing resistors you HAVE to have as close a value as possible otherwise it's a flawed comparison, no? Please don't shoot me down in flames over this comment.

As I understand it, grid stoppers act like a low pass filter, the higher the value the lower in the frequency range the cut-off slope is so changing this to a slightly different value shouldn't change much as I think the cut-off point is very high anyway.



M

[PicknStrum]

well done nice job. Are you going to put the proper 'Dumble' metal corners on your amp? They hide a lot of things and serve as protection too. Your corners look great. I do like the traditional look with the corners myself.


Regarding resistors, Changing with different values doesn't seem to me like a very scientific way of determining the difference in sound between brands. I mean 150 to 180 k on the slope resistor will change the frequency of the tone stack, albeit slightly it's still a difference of 20% in value, surely when comparing resistors you HAVE to have as close a value as possible otherwise it's a flawed comparison, no? Please don't shoot me down in flames over this comment.

As I understand it, grid stoppers act like a low pass filter, the higher the value the lower in the frequency range the cut-off slope is so changing this to a slightly different value shouldn't change much as I think the cut-off point is very high anyway.



M

I completely agree with you that the value of the resistors need to be the same for comparison, especially on something like the tone stack. Sounds like the only value differences in Vertigo's circuit are the 2 grid stoppers (V1a and V2a) because Jelle didn't have those values in stock. As for me, I don't have anything to compare to yet

I understand grid stoppers the same as you - filter off high RF that may be present in the circuit. Would changing the stopper value also change the strength of the AC guitar signal? i.e. higher grid stop resistor = smaller signal / volume?

[Vertigo]

You'll get no argument from me about the function of the grid stoppers or the importance of limiting change to get a real evaluation of the differences. It probably didn't come across well, but I wasn't trying to claim that the grid stoppers weren't an essential part of the circuit, just that there are effectively three resistors in series at the input of V2 and was hypothesizing that it might be possible to compensate for a value change by making up the difference elsewhere in that chain. I should really swap my V1 tube back to the JJ for comparative purposes, but honestly I don't care all that much because it sounds better as is, regardless of what caused the change.

This is a specific part of the circuit that I'd like to understand better. The amount of overdrive created by turning the OD trimmer clockwise is very appealing, but I have to turn the level knob down to keep the volume reasonable compared to the cleans. The OD Vol knob is so touchy in that lower range. It would be nice to get the mega saturation AND have a useable ODVol knob. This is a fun learning platform for sure.

[martin manning]

As I understand it, grid stoppers act like a low pass filter, the higher the value the lower in the frequency range the cut-off slope is so changing this to a slightly different value shouldn't change much as I think the cut-off point is very high anyway.

That's true for typical 33k-68k grid stoppers, where the resulting cut-off frequency is 15-30 kHz. When you see values up near 200k, then the cut-off is down around 5 kHz, and it's probably there to roll off some of the high end.

Looking at these substitutions, there might be a noticeable effect going from 390 to 330Ω on the PI tail. That will reduce the GNFB by 15% and shift the presence frequency response up by the same amount.

The Ratio knob is there to balance clean and OD volumes. I look at the entrance trimmer as setting the minimum OD distortion, which is increased as the Level/Drive control is advanced. There is a lot of flexibility there, some would even say too much!

[talbany]

That's funny, I went through the exact same procedure - measure and tape their values. Here are the values that differed for me a bit:

20k - this was V1A grid, same as you mentioned (instead of 33k)
55k - this was V2A grid, same as you mentioned (instead of 68k)
330R - he advised me this was a replacement for the 390R b/w 0.1uF and 2.2uF going to presence cap
115k - he advised me this was a great resistor for between the 0.1uF and OD level pot - this replaced the 100k - I got the vibe that this was more of a preference thing but I'm rolling with the expert
180k - he advised me to place this where the 150k is in the layout b/w .005uF and the OD ratio pot. So I got two 180k's and one was to replace the 150k; I'm wondering if that's what your 150k actually is, unless it really is that far out of spec.

As far as I've read / learned, the grid stoppers are mainly to filter off high frequencies but you'd think there would be some attenuation changes with major changes to the values. Especially on a circuit like this in which people indicate that even brands of resistors make a fairly noticeable difference.

EDIT: Now that I'm thinking about it, I'm thinking maybe the 2 higher values he gave me for the OD section maybe compliment the slightly lower values on the V1a grid and V2a grid.

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

[Vertigo]

That's funny, I went through the exact same procedure - measure and tape their values. Here are the values that differed for me a bit:

20k - this was V1A grid, same as you mentioned (instead of 33k)
55k - this was V2A grid, same as you mentioned (instead of 68k)
330R - he advised me this was a replacement for the 390R b/w 0.1uF and 2.2uF going to presence cap
115k - he advised me this was a great resistor for between the 0.1uF and OD level pot - this replaced the 100k - I got the vibe that this was more of a preference thing but I'm rolling with the expert
180k - he advised me to place this where the 150k is in the layout b/w .005uF and the OD ratio pot. So I got two 180k's and one was to replace the 150k; I'm wondering if that's what your 150k actually is, unless it really is that far out of spec.

As far as I've read / learned, the grid stoppers are mainly to filter off high frequencies but you'd think there would be some attenuation changes with major changes to the values. Especially on a circuit like this in which people indicate that even brands of resistors make a fairly noticeable difference.

EDIT: Now that I'm thinking about it, I'm thinking maybe the 2 higher values he gave me for the OD section maybe compliment the slightly lower values on the V1a grid and V2a grid.

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.