Search found 36 matches

by atalas
01 Nov 2019, 13:08
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

chasbenson wrote:Bias at 4v....5v sounds like shit
~5V is what I measured on the unit I had for Q1. Sounded alright to me.
Cool thing about a trimpot is it let's people decide for themselves what "sounds like shit." :thumbsup
by atalas
09 Oct 2019, 03:59
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Is there a suggested voltage for Q1? Pedal sounds pretty nice in front of my Music Man with Bass, Mid, and Treble set to 5 ~5V, or if you have a bunch of J201, set the source resistance to 12K and swap JFETs until you get one sit at 5V at the source. This will achieve a closer sonic result than jus...
by atalas
07 Sep 2019, 06:21
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Is there a suggested voltage for Q1? Pedal sounds pretty nice in front of my Music Man with Bass, Mid, and Treble set to 5 ~5V, or if you have a bunch of J201, set the source resistance to 12K and swap JFETs until you get one sit at 5V at the source. This will achieve a closer sonic result than jus...
by atalas
05 Sep 2019, 08:53
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Kinda curious why my bass and treble boost when the knobs are CCW Reverse your lug 1 and 3 connections on your pot, and the jumpers if you installed them. I tried to adapt the circuit values in order to get the same stage gains using the 2n5457 Fets. The adaption of the drain and source resistors i...
by atalas
01 Sep 2019, 21:01
Forum: DIY Stompbox designs
Topic: Building a clone of Tychohabre Parapedal wah ,some mods?
Replies: 5
Views: 1754

Re: Building a clone of Tychohabre Parapedal wah ,some mods

I think best course of action here is to get more general knowledge about how wahs work. I'll admit I don't know much about wahs, but if I wanted to know what you're asking, I'd start reading up on wah circuits, how they work, and how changing certain parameters affect the sound. Then I'd read about...
by atalas
20 Aug 2019, 04:27
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

temol wrote:It may be cheaper to use charge pump than buy MMBFJ201 transistors :)

T.
More importantly, it may make other, more readily available JFETS viable.
by atalas
15 Aug 2019, 15:51
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

chasbenson wrote:May as well do it right.
Thanks for the input, schematic updated.
by atalas
14 Aug 2019, 16:51
Forum: Boutique Stompboxes dissected...
Topic: Dusky Electronics - Hypatia fuzz / distortion
Replies: 5
Views: 1291

Re: Dusky Electronics - Hypatia fuzz / distortion

Interesting, thanks for the schematic.
by atalas
13 Aug 2019, 17:53
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Any chance SMD FETs are more consistent than their through hole ancestors? I've got some MMBFJ201 on order, but don't relish the idea of sorting through them to find a matched trio! Wouldn't be so bad if they could be tested as easily at the through hole variety. Thanks for the link to the Fetzer V...
by atalas
13 Aug 2019, 15:21
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Did you measure C5 and C10? I estimated the size of the capacitors and therefore I would say that the values of they are greater than 10uF. Yes, they were measured out of circuit by Bugg at 10uF. Hi Atalas, hi Bug I thank you for your measurements and tracings, I appreciated it a lot. I personally ...
by atalas
13 Aug 2019, 02:46
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Manfred wrote:Did you measure C5 and C10?
I estimated the size of the capacitors and therefore I would say that the values of they are greater than 10uF.
Yes, they were measured out of circuit by Bugg at 10uF.
by atalas
11 Aug 2019, 18:24
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Here is another photo of the PCB all be it a little fuzzy https://i.ibb.co/W6TpN7S/IMG-1970.jpg It looks likes C6 and C11 are not populated just like the version Atalas traced, what effect will adding or subtracting the bypass cap C11 have, a hazy recollection when I built a tube amp a while back w...
by atalas
11 Aug 2019, 16:24
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

The FETs in mine were marked 62P, which is still a J201. If I get a chance I'll measure their specs with my DCA75, but not sure if I'll have the time to crack it back open. Gotcha, I think that's ON's code. From what I read it seems like the J201 SMD are fairly consistent, maybe what's known alread...
by atalas
11 Aug 2019, 14:38
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Yep, there was a source bypass cap on the second and third JFET stages. Interesting, out of curiousity, is the SMD code on the FETs the same as mine (P1HYE)? Ideally I'd like to include a little blurb in the schematic about picking JFETs. Can you get readings on the Vp and Idss for the FETs in your...
by atalas
11 Aug 2019, 05:59
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

bugg wrote:Ahh yes, you are correct. It would have been C11 on your PCB.
Gotcha, so did your unit have a cap there? Only Q2 had a bypass cap in my friend's unit.
by atalas
11 Aug 2019, 05:01
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

Eh I'm confused now. I'm pretty confident the treble control is hooked up the way it's shown in the schematic. I can confirm, the Treble control is correct as drawn in your schematic. You are missing a Source bypass cap on the third FET stage (it would be C5 looking at your pic of the PCB). Really?...
by atalas
08 Aug 2019, 04:06
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

In that case the treble control is not a usual low cut filter but a frequency-dependent gain control of the Q3 stage. In the AC equivalent circuit the seriell circuit consisting of capacitor C7 and the treble potentiometer which is connected in parallel to the drain resistor and forms a frequency-d...
by atalas
05 Aug 2019, 18:34
Forum: Boutique Stompboxes dissected...
Topic: Benson Preamp [traced]
Replies: 89
Views: 24786

Re: Benson Preamp [traced]

I removed the entire output circuit after the drain node of Q3 and add the Wampler Plexi output circuit. The circuit simulation showes a better treble control range now. BensonTrebleControl4.jpg Improved by not vastly different. Again, there's also the possibility my DMM just couldn't accurately re...
by atalas
05 Aug 2019, 18:30
Forum: Parts Sourcing & Trading
Topic: buying transistors, ICs from ebay -- ant-notes for beginners
Replies: 5
Views: 3117

Re: buying transistors, ICs from ebay -- ant-notes for begin

Ebay's feedback system overall means nothing when it comes to "power sellers". I personally have been feedback begged, offered a bribe, (and threatened!) for leaving a negative numerous times. Pay attention to certain sellers. You will see negative feedbacks disappear over time and yet the same cra...
by atalas
05 Aug 2019, 15:35
Forum: Boutique Stompboxes dissected...
Topic: Dinosaural OTC-201 Opticompressor [traced]
Replies: 7
Views: 2552

Re: Dinosaural OTC-201 Opticompressor [traced]

great work - but the bipolar transistors are incorrectly marked on the schematic ? Right you are, I got the original trace and the DIY version mixed up. I attached the corrected one. How crucial is the specific vactrol used? I think I have some VTL5C1 laying around, would the substitution for the V...