erwin_ve wrote: ↑Thu May 23, 2019 3:07 pm
The signal entrance at the Fet board has to be on the other end of the 100pF-1M combination.
Thank you and updated!
OK so which of the circuits did you take from the hand-drawn 002 schematic and which ones did you take from Aarons layout?. Another words is this a direct copy of 002 or a hybrid of some sort as I see a few things which are not consistent with the 002.
Tony
" The psychics on my bench is the same as Dumble'"
I went off of the rev 7 .sch file and cross referenced bits from the hand drawn for accuracy. I am not using MHartman's layout because that's like 002 and 004 had a baby (lnfb is not at all the same as 002). I noted any deviation from a direct copy of the hand drawn 002 in my layout but it's 99% a direct #002 via the hand drawn with only component value change in reverb and one in the step filter to improve them. Layout and circuit jumpers is intended to be a practical direct copy for eyelet board version. There is a chance I missed something entirely with my layout and the peer review is helping us get there. Rest assured those two component value changes are based on experience or someone who built this circuit before and found it beneficial enough to add them here. For those wanting 100% based on the hand drawn, I indicated those changes in my notes section for completion. I will take a look at my notes section to see if there is a better way to come forth with additional clarity. In theory, one should be able to compare the hand drawn and my layout and any/all changes should be noted in the "notes" section.
rccolgan wrote: ↑Sat May 25, 2019 2:46 am
I went off of the rev 7 .sch file and cross referenced bits from the hand drawn for accuracy. I am not using MHartman's layout because that's like 002 and 004 had a baby (lnfb is not at all the same as 002). I noted any deviation from a direct copy of the hand drawn 002 in my layout but it's 99% a direct #002 via the hand drawn with only component value change in reverb and one in the step filter to improve them. Layout and circuit jumpers is intended to be a practical direct copy for eyelet board version. There is a chance I missed something entirely with my layout and the peer review is helping us get there. Rest assured those two component value changes are based on experience or someone who built this circuit before and found it beneficial enough to add them here. For those wanting 100% based on the hand drawn, I indicated those changes in my notes section for completion. I will take a look at my notes section to see if there is a better way to come forth with additional clarity. In theory, one should be able to compare the hand drawn and my layout and any/all changes should be noted in the "notes" section.
Good so it's basically an 002 with a few spot changes here and there. Just want to make sure before I cross reference the layout with the one I have for accuracy and parts selection before spending any time with it
BTW. Check your inbox
Tony
" The psychics on my bench is the same as Dumble'"
This is a exciting thread!
Colgan posted the entire chassis project on github so I decided to do a PCB design that would match his chassis dimensions and holes.
The plan is to make this pcb available as gerber files which are used for PCB production.
Teaser:
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erwin_ve wrote: ↑Sat May 25, 2019 7:14 am
This is a exciting thread!
Colgan posted the entire chassis project on github so I decided to do a PCB design that would match his chassis dimensions and holes.
The plan is to make this pcb available as gerber files which are used for PCB production.
Teaser:
This is so amazing! Looks a lot more simple than mine lol. Very timely thread indeed!
Based on feedback on my draft #002 layout, I've made reverted all custom preamp changes to now match the japanese hand drawn schematic. Hopefully now is easier to peer review now since it's comparing one to one. I've made the layout more eyelet friendly and is built around 3.125" fiber boards. Since the layout is drawn in DIYLC, Hoffman Amp's CNC machine can turn out eyelet or turret boards for you. Or you could print 1:1 scale and drill your own board using blank 3.125" boards. The power section accommodates new F&T filter caps.
EDIT (5/29/19) Fixed Bias entry point on phase board.
EDIT (6/4/19) Fixed resistor value on phase driver board from 820k to 820ohm.
EDIT (6/14/19) Removed attachments to encourage downloading the latest changes from GitHub https://github.com/colganr/steel-string-singer-sn-002
Last edited by rccolgan on Fri Jun 14, 2019 11:39 am, edited 3 times in total.
Bombacaototal wrote: ↑Sat May 25, 2019 12:35 pm
This thread is great! Just a curiosity, is there any difference using 4x100uF or 2x200uF for the power supply?
Well actually that's 50uF you want, if you were going 2X. They're putting 2x100uF in series (which for capacitance follows that complex equation, but if they're the same is effectively 1/2 of a single one).
So if you can get a capacitor that can take the max voltage of the circuit, you can do 2x50uF instead of 4x100. Usually that can be quite hard for the first at least in the B+ rail.
Bombacaototal wrote: ↑Sat May 25, 2019 12:35 pm
This thread is great! Just a curiosity, is there any difference using 4x100uF or 2x200uF for the power supply?
Well actually that's 50uF you want, if you were going 2X. They're putting 2x100uF in series (which for capacitance follows that complex equation, but if they're the same is effectively 1/2 of a single one).
So if you can get a capacitor that can take the max voltage of the circuit, you can do 2x50uF instead of 4x100. Usually that can be quite hard for the first at least in the B+ rail.
~Phil
Thanks Phil! That does make sense. Is it fair to say that a 4x100uF (equivalent to 2x50uF) circuit will feel less stiff (more saggy) than a 2x220uF?
Yes, any decrease in filtering can introduce some power supply sag, I don't know for sure the difference between 50 vs 110, in actual tone/feel, it's entirely possible that for most purposes, Dumble found that 50uF was more than enough to control any power supply requirements. More can't hurt, but can make an amp sound a bit more 'sterile' as I understand it.
Dry fit of my boards for my SSS #002 build. Transformers from Triode delivered tomorrow and tubes/misc. parts arriving from Amplified Parts next Saturday. This one is fun!
Fired up the SSS #002 this morning and it amplifies guitar input signal with reverb!! I built a bulb current limiter to be extra safe this time. My question for the group is for bias. I added the bias pot and 22k resistor to ground but that seemed to bring the bias way too high so I adjusted the pot to the lowest setting that connects the two legs. I believe this would be just like the original schematic. I'm getting around 74mA @ 424v which I think is too high by my calculations for my 30w 6L6WGC TAD tubes. I'm not sure if it's because the tubes are hot but it seems like the bias cap is very warm to the touch. I can keep my hand on it but it's pretty warm. Not saying this is bad, just an observation.
Anything I should look for or adjust to lower the bias current? I'm excited to learn on this one. Attaching my latest layout for reference and thank you in advance!
On an octal:
Pin 1: -34VDC
Pin 3: 422VDC
Pin 4: 422VDC
Pin 5: -34VDC
Pin 6: 424VDC
Pin 8: 75.3mVDC (1 ohm quick bias added in series to ground)
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