Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

March 29, 2024, 01:16:32 AM

Login with username, password and session length

Recent Posts

 

New Guy with an interesting design idea

Started by Bajaguy, April 08, 2013, 04:22:42 PM

Previous topic - Next topic

Bajaguy

That makes sense. I'm on my way out for another few days, so I'll take the datasheet for the 2005 and play with the ducan calculator while im gone. I'm sure I'll have a bunch more questions by the time I get back... :cheesy:

Baja

Bajaguy

Just a quick update:

I've been building a few different preamps to play with, but I ordered some J201's from overseas and I'm still waiting.....

I'll be sure to throw an update when I get all my parts and get topluggin the modules together.

Baja

Roly

I have made some changes; 3-pin regulator instead of zeners for lower hum; experimental "quasi-parametric" tonestack, and lowered the tail resistor fo the last emitter follower to produce soft clipping.



Importing FET's?  MPF102's should be locally available just about everywhere.
If you say theory and practice don't agree you haven't applied enough theory.

Bajaguy

I have the MPF102's, but I was waiting on the J201's I ordered. I think I have enough parts to breadboard up your new shematic so I'll get back whern I have it up and running.

Baja

Bajaguy

Hey Roly,

Will 2n3904 be ok to replace the BC549C? I'm having trouble sourcing them locally, but I have a hand full of 3904's at my disposal and a weekend off to play with this! :dbtu:

Baja

Roly

Well I chose the BC549C because that was what I noticed in the LTSpice transistor list.  Being an emitter follower in a pretty undemanding situation just about anything worthy of the title "transistor" should work.   8|

(if you recall this started as a response to that trimpot horror as a preamp circuit that was component tolerant without trimpots, so substituting devices to hand is exactly what I had in mind)

For a long while Elektor rationalised their transistor and diode types with terms like TUN and DUS, "Transistor Universal NPN" and "Diode Universal Silicon", and had huge lists of compliant types.  Jaycar here still sell packs of PN100's which are intended to replace a large range of transistors in most applications.  As long as the transistor has a voltage withstand greater than the supply and a current rating a bit higher than the peak expected current, and an hfe of at least 50 (100 is better) then it should work.  From the datasheet the 2N3904 looks quite suitable.

I'm still hanging out to hear how you get on with this, if you find it satisfactory, or if it has shortcomings that need tweeks, or ...
If you say theory and practice don't agree you haven't applied enough theory.

Bajaguy

That's great, I'll get to bread boarding it while I have some down time in the shop this week. I'm really excited to see if this works out! Stay Tuned...

Baja

joecool85

Quote from: Roly on August 17, 2013, 04:00:52 AM
Well I chose the BC549C because that was what I noticed in the LTSpice transistor list.  Being an emitter follower in a pretty undemanding situation just about anything worthy of the title "transistor" should work.   8|

(if you recall this started as a response to that trimpot horror as a preamp circuit that was component tolerant without trimpots, so substituting devices to hand is exactly what I had in mind)

For a long while Elektor rationalised their transistor and diode types with terms like TUN and DUS, "Transistor Universal NPN" and "Diode Universal Silicon", and had huge lists of compliant types.  Jaycar here still sell packs of PN100's which are intended to replace a large range of transistors in most applications.  As long as the transistor has a voltage withstand greater than the supply and a current rating a bit higher than the peak expected current, and an hfe of at least 50 (100 is better) then it should work.  From the datasheet the 2N3904 looks quite suitable.

You know, I always kind of suspected this was the case 99% of the time, but it's good to hear that I was right.  Thanks for the helpful information.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Roly

There are exceptions where you have to tread carefully but they tend to be pretty obvious, low noise such as mic preamps, VHF applications, high voltage, and high power.  But audio preamps for guitar are not a demanding application and many common devices will do just fine.  The MPF102 for example is actually designed for VHF signal amplification so it does just fine for audio and even down to infrasonic tremolo frequencies, or as an audio path switch.

These days as long as a transistor (or IC) has "enough" of everything a particular stage needs, then the main problem is the physical one of "will it fit"?  The main reason certain devices become very well known like the 2N3055, LM555, 4558, BC109 and so on, is that the one device will work in all sorts of situations and this allows everybody to narrow their inventory of device types.
If you say theory and practice don't agree you haven't applied enough theory.