Search found 95 matches

by tschrama
07 Apr 2018, 07:40
Forum: Modern Stompbox Effects (1975 - ...)
Topic: TMR Bumble Buzz Fuzz
Replies: 7
Views: 10198

Re: TMR Bumble Buzz Fuzz

Interested in this one!

Anyone got more info or better gutshots?
by tschrama
20 Nov 2015, 09:36
Forum: Boutique Stompboxes dissected...
Topic: MXR EVH 5150 Overdrive
Replies: 36
Views: 27232

Re: MXR EVH 5150 Overdrive

I find the clips so far pretty good! Eager to have a look at the guts and help tracing 8)
by tschrama
09 Dec 2014, 15:28
Forum: Printed/Published Online Designs
Topic: Lowest noise floor buffer design?
Replies: 16
Views: 10640

Re: Lowest noise floor buffer design?

samhay wrote:
tschrama wrote:Oamp bias current is DC, it does not play a role in AC impedance. You cannot relate this bias current to an imput impedance.
Right, but it will only pass AC if you can bias the input to somewhere vaguely near half supply.

So?
by tschrama
03 Dec 2014, 21:01
Forum: Printed/Published Online Designs
Topic: Ripple Rejection for Sensitive Circuits
Replies: 10
Views: 4375

Re: Ripple Rejection for Sensitive Circuits

So the latest... in an attempt to minimize the voltage drop to just the internal diode of the bjt, I used a 100R for the base resistor and a 1uF base cap. I know this puts the knee at ~1.6KHz, but I'm attempting to ditch the SMPS hash on this particular psu. Heres some before and after pics photo 1...
by tschrama
03 Dec 2014, 17:50
Forum: Printed/Published Online Designs
Topic: Lowest noise floor buffer design?
Replies: 16
Views: 10640

Re: Lowest noise floor buffer design?

Oamp bias current is DC, it does not play a role in AC impedance. You cannot relate this bias current to an imput impedance.
by tschrama
03 Dec 2014, 17:46
Forum: Printed/Published Online Designs
Topic: Ripple Rejection for Sensitive Circuits
Replies: 10
Views: 4375

Re: Ripple Rejection for Sensitive Circuits

Definitly use a high Hfe BJT :thumbsup . That'll alow for a high value base-resitor, and thus high rimple rejection, and keep DC-loss to a minimum. Your DC-loss i about 0.6V + the voltage across the base-resistor.
by tschrama
03 Dec 2014, 17:15
Forum: Printed/Published Online Designs
Topic: Ripple Rejection for Sensitive Circuits
Replies: 10
Views: 4375

Re: Ripple Rejection for Sensitive Circuits

Great idea. But as drawn, the cap-multiplier will perform worse than the RC filter, just because the time constant of the RC filter (100R/220uF) is lower than the time constant of the BJT's (1K/10uF). To get similar hum-reducing performance you could opt for 2.2K/10uf in the cap-multiplier. I think,...
by tschrama
03 Dec 2014, 14:19
Forum: Printed/Published Online Designs
Topic: Lowest noise floor buffer design?
Replies: 16
Views: 10640

Re: Lowest noise floor buffer design?

The 5532 has a low input impedance, which makes it less than ideal for feeding it from a relatively high Z-out like a guitar pickup, . The input impedance of the 5532 is determined solely by the components around it - the actual input impedance of the device is a few TΩ. Similarly, the output imped...
by tschrama
01 Dec 2014, 22:59
Forum: Printed/Published Online Designs
Topic: Lowest noise floor buffer design?
Replies: 16
Views: 10640

Re: Lowest noise floor buffer design?

go to http://www.diyaudio.com.. lot's of peolple over there that know about low noise design and noise-figures. e.g. This one would be allmost perfect: https://www.passdiy.com/pdf/B1%20Buffer%20Preamp.pdf http://193.254.231.38/velab/resources/pdf/2SK170.pdf I remember that at some point nelson pass ...
by tschrama
18 Sep 2014, 14:51
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

Perhaps it is worth considering another aspect of the circuit - you can design around fixed drain resistors and then use the op-amp to trim in the bias point so that your output sits at half supply (or wherever you want it). That's what bajaman has done, and this allows one to overcome one of the c...
by tschrama
16 Sep 2014, 20:08
Forum: Amplifiers
Topic: [request] SS POwer amp Schematic <Class ab 50-100W>
Replies: 5
Views: 3705

Re: [request] SS POwer amp Schematic <Class ab 50-100W>

http://sound.westhost.com/projects-0.htm#pwr

Cann't recommend that website enough... it's great, really really great.
by tschrama
15 Sep 2014, 20:43
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

Thanks ggedamed, very well put to words. And like electrip, I also think the only real functional difference might be the bias shifting that occurs with the cap when the signal becomes very large. There is no mention of this in the articles. Significant bias-shifting can occur in situations of heave...
by tschrama
14 Sep 2014, 19:02
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

Guys.. I am aware of the pentode like behavior and the gist of the articles posted etc etc.. I just dont see the !functional! difference between the resistor//cap verus opamp. They both act as a voltage source.
by tschrama
14 Sep 2014, 07:21
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

Well I did....and I still cannt see any differences nor did I expect to see any differences. A cap around a resistor makes that node AC low impedance, just like the opamp does.
by tschrama
14 Sep 2014, 07:16
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

bajaman wrote:tschrama
try plotting comparison curves for treble boosted square waves :wink:
cheers
bajaman

What should I expect to see?
by tschrama
13 Sep 2014, 12:50
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

I dont get, might be just my brain fart, but I realy dont see any differences between the opamp and a source resistor//cap. So for the sake of my insecurity I simulated them both, and guess what: no difference.. I would be tremendusly gratefull if somebody could explain what's the purpuse of the opa...
by tschrama
12 Sep 2014, 13:02
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

Read the articles, luckely it was less reading that I thought it would be. Even if engles is not my first language :wink: .. Cannt spot anything exciting... Just exchange the opamp for a pot+cap.. a 470uF/25V electrolytic cap have, for all practical audio purpuses, a low enough impedance in this app...
by tschrama
12 Sep 2014, 07:00
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

No, I didn't read the document. If I had even the slightest hunch that this opamp might have some kind of benifit ( and a little bit of time), I would... Sure you need to set a DC point, but I cann't seem to find any functional difference between setting it with a source resistor//cap or an opamp. D...
by tschrama
10 Sep 2014, 19:31
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

What is the benefit of the opamp to bais the JFET? Could you just use a resistor parralleld with a large cap instead? Seems to me the opamp only serve to couple DC and add noise.. :scratch: DC bias without source resistance, and thus with minimised negative feedback. You can also ground the source ...
by tschrama
10 Sep 2014, 10:45
Forum: Printed/Published Online Designs
Topic: Class-A JFET / Triode Exaggerator
Replies: 47
Views: 20569

Re: Class-A JFET / Triode Exaggerator

What is the benefit of the opamp to bais the JFET? Could you just use a resistor parralleld with a large cap instead? Seems to me the opamp only serve to couple DC and add noise.. :scratch: