Fine tuning my new 50W #102 build

[xpc1000]

One of the drawbacks being a 250k will add too much bass giving you the very problem you have? A fuzzy saw-toothed sounding low end Sounds like you want to decrease the low end content.

In theory adding more bass should make things worse as you said, but not sure why, what I hear is bass seems less fuzzy now. When I have the time I'll repeat the first recording I did with exactly the same setup, so I can verify this impression objectively.

[ayan]

My first impression was positive, although I remember Gil mentioned he was not in favour of using 250k pots in the overdrive section. I'm not sure what would be the drawbacks.

One of the drawbacks being a 250k will add too much bass giving you the very problem you have? A fuzzy saw-toothed sounding low end Sounds like you want to decrease the low end content.
BTW.Are those metal film's you have on the plates on V1 V2?

Tony

Don T. is right on the money, that is the very drawback I experienced when dabbling with 250K pots in the overdrive section.

[xpc1000]

My first impression was positive, although I remember Gil mentioned he was not in favour of using 250k pots in the overdrive section. I'm not sure what would be the drawbacks.

One of the drawbacks being a 250k will add too much bass giving you the very problem you have? A fuzzy saw-toothed sounding low end Sounds like you want to decrease the low end content.
BTW.Are those metal film's you have on the plates on V1 V2?

Tony

Don T. is right on the money, that is the very drawback I experienced when dabbling with 250K pots in the overdrive section.

I tested again using exactly the same setup and dials as the initial test hiting the E string to be able to compare more objectively. The result was that the sound was getting more fuzzy with the 250k pot, as Tony and Gil mentioned! So I finally reverted the change. Thanks guys for your patience!

[rootz]

Have you tried limiting the amount of bass going into the OD section? Personally, I'm not a big fan of it, but you could try to add a 2n2 or 4n7 cap right before the 220k resistor leading to the OD entrance trimmer. This limits the amount of low end going into the OD, with a -3dB point of around 105 resp. 226 Hz. Less low end, less fuzz, but also much more apparent high end. You might need something, a HF taper, to limit the high end at the output of the OD section.

[ijedouglas]

I tested again using exactly the same setup and dials as the initial test hiting the E string to be able to compare more objectively. The result was that the sound was getting more fuzzy with the 250k pot, as Tony and Gil mentioned! So I finally reverted the change. Thanks guys for your patience!

Depending on what you want it to do, the 250K drive pot definitely can work but you will need to make some other changes (changes Mr Dumble made). Increase your reservoir caps to 330uf and reduce your bass pot size. Take a look at the 183 layout and you will see that he used the larger OD pots to add bottom end and then sculpted that bottom end with bigger filtering (firm up bottom end), smaller bass pot (311K) and smaller PI couplers. I just completed a total rebuild of my 183 (for the 5th time ) and I really paid a lot of attention to pot values and tapers. The amp is sounding really good and is pretty well balanced. These are all parts of a complete system and you may not achieve your end-goal by only changing a single part.

Having said that, if reverting the pot back to 100K gives you what you are looking for, please disregard my ramblings above

Edit: just took a look at your gut-shots again and see you have a lot of 1 watt resistors. Typically Mr Dumble used 1/2 watt resistors (except dropping string, screens, LNFB and GNFB). You may want to experiment with resistors and see if that changes the response. Knowing your issue is mainly with OD (you like the cleans? ) , I would start with the OD 2 out (150K). It looks like you have a 2 watt 150K 5% piher in there. Try a 1/2 watt carbon film and see if it makes any difference.

[xpc1000]

Have you tried limiting the amount of bass going into the OD section? Personally, I'm not a big fan of it, but you could try to add a 2n2 or 4n7 cap right before the 220k resistor leading to the OD entrance trimmer. This limits the amount of low end going into the OD, with a -3dB point of around 105 resp. 226 Hz. Less low end, less fuzz, but also much more apparent high end. You might need something, a HF taper, to limit the high end at the output of the OD section.

Good point! I'll take a look to this!

[xpc1000]

Depending on what you want it to do, the 250K drive pot definitely can work but you will need to make some other changes (changes Mr Dumble made). Increase your reservoir caps to 330uf and reduce your bass pot size. Take a look at the 183 layout and you will see that he used the larger OD pots to add bottom end and then sculpted that bottom end with bigger filtering (firm up bottom end), smaller bass pot (311K) and smaller PI couplers. I just completed a total rebuild of my 183 (for the 5th time ) and I really paid a lot of attention to pot values and tapers. The amp is sounding really good and is pretty well balanced. These are all parts of a complete system and you may not achieve your end-goal by only changing a single part.

This is also a very good point! I'll take a look as well!

Having said that, if reverting the pot back to 100K gives you what you are looking for, please disregard my ramblings above

Reverting the pot back to 100k just sent me to the previous situation, not what I was looking for!

Edit: just took a look at your gut-shots again and see you have a lot of 1 watt resistors. Typically Mr Dumble used 1/2 watt resistors (except dropping string, screens, LNFB and GNFB). You may want to experiment with resistors and see if that changes the response. Knowing your issue is mainly with OD (you like the cleans? ) , I would start with the OD 2 out (150K). It looks like you have a 2 watt 150K 5% piher in there. Try a 1/2 watt carbon film and see if it makes any difference.

When I replaced the 150k piher resistor by a 180k one, the new one was a 1/2 watt piher resistor. Not sure if I have 220k and 68k 1/2 watts Piher resistors available to replace the remaining ones in the OD. I'll see what I can do.

[ijedouglas]

One other thing, which has been mentioned multiple times on this forum, is give the amp some time. Once you have a build that you feel gets pretty close to the # you are attempting, spend some time playing it and getting to know it. Very often I make a change and instantly regret it and want to revert it... but I've learned to give it some time. Without starting a large debate on break-in time, my experience has been that the amp definitely changes (mostly for the better) the more time you put on it. Your ear will also key in to things you like/dislike in the amp and sometimes the things you dislike initially, become the strong points of the amp. I just re-built my #124 with some NOS pots and initially thought the amp was too bright and stiff (reservoir caps changed as well). I have been playing it for the last month and it's really starting to grow on me. It's bright and open in contrast to my #183 which is a little more compressed and smooth.

[xpc1000]

One other thing, which has been mentioned multiple times on this forum, is give the amp some time. Once you have a build that you feel gets pretty close to the # you are attempting, spend some time playing it and getting to know it. Very often I make a change and instantly regret it and want to revert it... but I've learned to give it some time. Without starting a large debate on break-in time, my experience has been that the amp definitely changes (mostly for the better) the more time you put on it. Your ear will also key in to things you like/dislike in the amp and sometimes the things you dislike initially, become the strong points of the amp. I just re-built my #124 with some NOS pots and initially thought the amp was too bright and stiff (reservoir caps changed as well). I have been playing it for the last month and it's really starting to grow on me. It's bright and open in contrast to my #183 which is a little more compressed and smooth.

Thanks for sharing your experience. I also have notice subtle changes after some time in previous builds.

Once you have a build that you feel gets pretty close to the # you are attempting, spend some time playing it and getting to know it.

I'll definitely do exactly this

[xpc1000]

Yesterday I took the amp to a friend of mine to test it.

I made some changes to be able to test different OD configurations without having to open the cabinet. I temporarily replaced the presence pot by a 250K pot with one leg connected to the output of the OD and the other leg at the input of the level 100k pot. This way I was emulating adding a resistor before that pot. I also replaced temporarily for this test the bright toggle and used the switch for bypassing or not a 4n7 cap right before the 220k resistor at the input of the OD section. This way I could be able to limit the low end going to the OD, as rootz mentioned.

We tested two guitars, a Fender stratocaster and a Gibson 339. Used a dumbleator and a spring reverb, and 2x12 Eminence Red White & blues speakers in a Fuchs cabinet.

I enjoyed a lot the test by bringing the amp to someone who knew 100 times better than I how to play the guitar with this amp. I liked both the cleans and the overdrive.
I have attached two clips, one clean and the other OD. Unfortunately I used my mobile for recording, so the quality of the sound is not very good.

BTW here is a picture of the amp in the cabinet. I was still waiting for the green caps for the toggles, but I might end up changing the green led by a red one!

[ijedouglas]

Nothing wrong with that at all. Congrats!

[Abe5150]

Dang sounds pretty good!

[ayan]

Yesterday I took the amp to a friend of mine to test it.

I made some changes to be able to test different OD configurations without having to open the cabinet. I temporarily replaced the presence pot by a 250K pot with one leg connected to the output of the OD and the other leg at the input of the level 100k pot. This way I was emulating adding a resistor before that pot. I also replaced temporarily for this test the bright toggle and used the switch for bypassing or not a 4n7 cap right before the 220k resistor at the input of the OD section. This way I could be able to limit the low end going to the OD, as rootz mentioned.

We tested two guitars, a Fender stratocaster and a Gibson 339. Used a dumbleator and a spring reverb, and 2x12 Eminence Red White & blues speakers in a Fuchs cabinet.

I enjoyed a lot the test by bringing the amp to someone who knew 100 times better than I how to play the guitar with this amp. I liked both the cleans and the overdrive.
I have attached two clips, one clean and the other OD. Unfortunately I used my mobile for recording, so the quality of the sound is not very good.

BTW here is a picture of the amp in the cabinet. I was still waiting for the green caps for the toggles, but I might end up changing the green led by a red one!

Sounding very good , Xavier!

G.

[xpc1000]

Thank you guys for your comments! I have to say that I couldn't have done this without your help and the extensive documentation available in TAG!

One thing I forgot to mention were the final values that I finally selected for the OD section: the value of the resistor right before the level pot was nearly 100k and the 4n7 cap before the 220k resistor at the input of the OD section helped to compensate and partially remove some of the additional low end before the OD stage.

[philbard]

Thank you guys for your comments! I have to say that I couldn't have done this without your help and the extensive documentation available in TAG!

One thing I forgot to mention were the final values that I finally selected for the OD section: the value of the resistor right before the level pot was nearly 100k and the 4n7 cap before the 220k resistor at the input of the OD section helped to compensate and partially remove some of the additional low end before the OD stage.

Do you have a simple drawing of the pots and resistors you used for the OD section? Trying to get a clearer picture of where you ended up. Thanks!