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This post was updated on Aug 17, 2016; 8:27pm.
One of our students had this in today and allowed me to take it apart and see what's going on for a few hours. And sure enough it's YATS (as we knew from MK1) with a few mods and something I'm hoping someone can enlighten me on.
Some pics for whoever wants to cross reference the schematic with. ![]() ![]() ![]() I missed the 10u>10K>GND trace on this pic but it's all fine on the schematic AND apologies for not lining up the front/reverse pics better before I started. I had little time. The Schematic (massively overcomplicated relay switching omitted ![]() ![]() So my question...what is the point of 4 BJT in parallel at the input buffer? This wrecked my head for way longer than it should! I initially thought there was some kind of design error....or I missed some traces but nope...4 transistors in parallel acting as nothing more than a buffer. Anyone know why they couldn't just use 1 like any other TS? Anyone want to tackle a breadboard/layout and make an eejit out of me? ![]() I should point out that another forum member also had a go at tracing this here but I'm very confident there are a few errors. Still...it's good for referencing anyhow. Cheers folks...hope all turns out well |
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wow great effort! thanks a bunch!
I've always liked the GR.. so much more than the Ibanez- made TS. Analogman does a few different mods to the TS808/TS9.. has anyone played with any of these? I've seen the "Brown" mod, the "Silver" mod, and a few others. When I was really into the band Phish in college I read up on Trey Anastasio's rig and read that he used two Analogman-modded Silver tube screamers, one more mild/soft OD sounds and another for more aggressive, cutting distortion sounds. After I read that I listened more closely to Trey's sounds and could definitely hear when he kicked on one or the other or both. It costs about 150 to get a silver-modded TS on eBay.. just wondering if anyones had experience with these units. Love this circuit... the 100hz knob is money. |
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In reply to this post by Ciaran Haslett
Thanks for this Ciaran!
I think those BJT "buffers" at the input are what is known as a "current mirror". This idea is maintain a stable current but why it's used here (versus a standard BJT or op amp buffer) I'm not sure. The Drive and Tone circuits are conventional tube screamer, with a Timmy-style bass control ("Curve"). The later sections are a buffer and additional filtering prior to volume control and BJT output buffer a la tube screamer. So, all in all, it is YATS but with a few interesting quirks to keep the pedal DIYers on their toes ![]() |
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In reply to this post by Ciaran Haslett
Thank you! I'd like to eventually build this in the same enclosure with a Red Llama.
The 100Hz boost seems to be like on the MXR badass (Dunlop, like this one). I guess it has active and passive bass controls in the signal path. |
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This post was updated on May 28, 2016; 3:19pm.
In reply to this post by Ciaran Haslett
Cool job Ciaran!
Hope this would work. I've used one LF347 instead of 2 LF353s for space reason. Can anyone double check? ![]() |
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In reply to this post by Ciaran Haslett
Great job Ciaran, and Alex on the layout
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In reply to this post by Alex
Alex, thanks for sharing all your work!
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Thanks guys!
I think it matches the schematic. If you could confirm that, I'll move it to the main page. |
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Fantastic job Alex!!!! The pot grouping is pure class! If it matches the schematic...apologies lol. The output cap should be 10uF electro...not 1u. I even mentioned it under the dot trace but didn't correct it on the schem! Sorry about that. Sent from my iPhone
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No problem.
I've updated it. Let me know if you think it's good to go! ![]() |
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Sorry Alex...just back from a long studio job. Layout matches the schematic perfectly. Really amazing...as always. I hope the schematic doesn't let you down
![]() EDIT: Schematic and hi res link updated! |
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Hi all,
I just did an LTSpice simulation of the 4 transistor input "buffer" and saw no real difference between that configuration and a single transistor. Don't know if the four transistors provide any other "mojo" or not, but you could probably save three transistors by simplifying the input buffer. |
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This post was updated on Jun 02, 2016; 1:14am.
I've seen parallel transistors used for lower noise before, but I'm not sure what the point is for a guitar pedal. This isn't a lab instrument. 4 parallel transistors would lower the noise by 1/2X but there's probably more noise on the power rail than the input jack.
Oh, and I found this from The Art of Electronics (3rd ed) page 113: ![]() |
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In reply to this post by Ciaran Haslett
Did you guys had any luck building this?
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In reply to this post by Ciaran Haslett
Hi there! I've made two of those Green Rhinos following the stripboard, but now I have a real unit in my hands, and the output from both my clones aren't nowhere near the real one. Where should I start tweaking?
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Well I got around it placing trimpots on the 10k from base to ground on the output buffer and before the 10uF capacitor. Used 100k trimpots and tweaked by ear
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In reply to this post by Battery Acid
Do you mean volume? I only had this for a few hours so it's possible I got a resistor value wrong....and in fact I did
![]() On the layout its the 10K on OUT, between the 1u and 10u caps. Just went over the rest and they check out. Hopefully that does it for you. |
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You posted when I was in response so I missed your comment sorry. There's no need for the trimpot. A swap to 1 meg will do it. Sorry for the hassle
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Damn, now I feel really dumb! I was so pissed I didn't realized I was messing with pulldown resistors HAHAHAHA, thanks heaps!
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For those who have built it - how does it sound compared to a tube screamer???
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