Search found 363 matches

by rccolgan
Thu Mar 14, 2024 6:22 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

I successfully recreated my circuit in LTSpice for further study. Sharing here for anyone that's interested in tweaking the circuit. One thing I might amend in this circuit is using 10KA send and 10KA return pots. Or at least a 10KA on the return instead of 1M I currently have. If you've already mad...
by rccolgan
Tue Mar 12, 2024 1:51 pm
Forum: Dumble Discussion
Topic: Two rock crs v3 clone and v1 vs v3 differences
Replies: 100
Views: 24848

Re: Two rock crs v3 clone and v1 vs v3 differences

What do you mean by the ltspice files? The ones containing the designs, but also files with the tube models, parts, transformer models. Looks like I should just make a post here on this forum with all files I use, for others to use too and hopefully improve. I for one would love this, having just g...
by rccolgan
Sat Mar 09, 2024 9:02 am
Forum: Dumble Discussion
Topic: #002 Steel String Singer - almost there
Replies: 69
Views: 1388

Re: #002 Steel String Singer - almost there

Looking good!!!
by rccolgan
Fri Mar 08, 2024 3:06 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Hey Ryan, the boards arrived today and look really good. The faceplate is also a very nice touch too. I wanted to lacquer it to protect the screen print but was afraid of dissolving it so covered with clear adhesive plastic instead. EDIT: the clear plastic looked bad so I hit it with clear nitro, i...
by rccolgan
Fri Mar 01, 2024 2:00 am
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Yes, sorry for the delay. Heads down on the accompanying documentation. Based on my calculations, the 1m bias resistors are good to go. I have them in my prototype and it's very stable. The bias for the opa2134 is in the pico-amps so not much needed if you're using that chip. I'm using OPA2134, wha...
by rccolgan
Thu Feb 29, 2024 4:48 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Yes, sorry for the delay. Heads down on the accompanying documentation. Based on my calculations, the 1m bias resistors are good to go. I have them in my prototype and it's very stable. The bias for the opa2134 is in the pico-amps so not much needed if you're using that chip.
by rccolgan
Mon Feb 26, 2024 8:21 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Excellent, thanks. Let us know if you are going to bias the op amp as suggested. I know it's only the v1 BOM, but I don't think the Mouser project link is the correct one yet. Is it possible to see a photo of the loaded DC -DC board with the inductors and Traco in place ? Good catch. Just updated t...
by rccolgan
Tue Feb 13, 2024 12:35 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

The BB should be good still. You just need to remove the bottom nut on your footswitch. I'm building my next one in a BB size Excellent, thanks. Let us know if you are going to bias the op amp as suggested. I know it's only the v1 BOM, but I don't think the Mouser project link is the correct one ye...
by rccolgan
Tue Feb 13, 2024 1:26 am
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Ryan what are those knobs? I'm going to the knob shop on Tuesday and like to get some similar cool ones :D Also if you do have a copy of the basic K-lator schematic, that would be appreciated, it used to be on Brown Note but is long gone, I think. Here ya go for the v1 BOM. I will add 2x 470k resis...
by rccolgan
Sun Feb 11, 2024 10:48 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Impressive work! 8) I just wonder whether the lack of a bias resistor at the + input of the opamp may cause problems. See e.g. https://www.physicsforums.com/threads/voltage-follower-bias-current-opamp.788018/ or https://northcoastsynthesis.com/news/one-minute-op-amp-analysis/ Fair point! Thanks for...
by rccolgan
Sun Feb 11, 2024 11:54 am
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Impressive work! 8) I just wonder whether the lack of a bias resistor at the + input of the opamp may cause problems. See e.g. https://www.physicsforums.com/threads/voltage-follower-bias-current-opamp.788018/ or https://northcoastsynthesis.com/news/one-minute-op-amp-analysis/ Fair point! Thanks for...
by rccolgan
Sat Feb 10, 2024 1:30 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

This looks amazing Ryan, astonishing how fast you developed such a nice product. Even Dumble approved fonts on the PCB's. With a TL062 this would probably even run of a battery. I'm curious to see how the frequency response of the loop is and how well it works with long cables. Thanks! Here are som...
by rccolgan
Fri Feb 09, 2024 2:40 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

It's alive! Sounds great. The 2k drive pot indeed works well. If unity is desired, maxing out the drive is necessary in this design. I need to play more with the recovery pot values as 1M goes from grounded signal to full within the first quarter turn. I'm also thinking 1m still might be necessary ...
by rccolgan
Thu Feb 08, 2024 7:58 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

@Ian, @Dan, @Electron, @Erwin - Thanks, ya'll!! Call me crazy but I think I can hear the difference when I swapped out the opamp to a legitimate OPA2134PA. (Lots of knockoffs out there so I always buy from trusted sources). Seems like the noise floor is quieter and the whole signal seems spot on to ...
by rccolgan
Thu Feb 08, 2024 2:31 pm
Forum: Dumble Discussion
Topic: "A box later" Dumble
Replies: 73
Views: 27254

Re: "A box later" Dumble

Great job! I may have to try one o these :D Thanks!! I need to fix the LED location on the faceplate and it should be ready for DIY scene soon once the revisions are made. I forgot to add that I'll try an OPA2134PA op amp instead of the TL072 to see if that slight top-end loss is recovered. I know ...