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Messages - Zozobra

Amplifier Discussion / Re: op amp voltage and tone
March 27, 2023, 05:43:58 PM
Ok, I'll stick to ±15V rails then  :)
Amplifier Discussion / op amp voltage and tone
March 20, 2023, 05:41:32 PM
I was just idly thinking about the effect of op amp voltage on tone. Most op amp preamps typically use ±15V rails as that's the limit of the TL072 op amp commonly used, but is it an anachronism to be limited by this when there are modern op amps capable of higher rail voltages? Something like the OPA552PA is capable of ±30V, but all other things considered would it sound any different than if it was capped at ±15?
This reverb listing has a gut shot of the 50W model:
Preamps and Effects / Re: LND150 Jose style preamp
September 04, 2019, 05:27:11 AM
I'm not too sure what happened with the electrolytic footprint.  In any case, I've made my own footprint conforming to convention.

My concern with breadboarding this is that several parts of this circuit have some rather high voltages on them.  Way higher than I'd be comfortable using on a breadboard.  I know it may seem wasteful but ten boards shipped from a Chinese fab house will only run me for $10 so if it's trash then it's trash!  I have a good few more hours of checking and fiddling before I pull the trigger on this anyway and right now I'm more interested in op amp preamps a la Randall/Orange and they can definitely be tinkered with on a breadboard  :cheesy:
Preamps and Effects / Re: LND150 Jose style preamp
July 15, 2019, 05:42:06 AM
Good spot guys, thanks.  Tired eyes and over-familiarity and all that and a botched job of porting from LTSpice!  Not sure how i managed that goof but I did  xP

I should note that the schematic here is just showing the on-board stuff.  There would be a 1M impedance reference mounted to the input jack socket.

I am going to play around with the value of C19 as I know it has quite an impact on the character of the diode clipping.  100n is just what is commonly used.
Preamps and Effects / LND150 Jose style preamp
June 27, 2019, 11:56:19 AM
Hi folks,

I've been pushing the peas around the plate on an LND150 version of some of the newer Jose style diode clipper amps based on KMGs work.  This is loosely based on Ch.2 of the Butterslax.  I'm handling the output buffer on a second board using a quad channel opamp so that I can add in an active Baxandall tonestack should I decide to use an SS poweramp and want pseudo presence & depth controls.

Here is what I have thus far.  Comments and criticism welcome :)

Amplifier Discussion / Orange CR120 power amp
November 13, 2018, 09:53:50 AM
I'm certainly finding myself drawn towards the old SS or hybrid stuff these days and I want to have a crack at making a reasonably high powered power amp early next year.  While doing some digging I came across some gut shots of the Orange CR120 with a good close up of the power amp, this interests me as it looks like it could be pretty simple and the amp sounds good and is loud enough for my needs.

shot here:

First guesses is that it's a pair of TDA7294 chips bridged.  The amp is rated for 120W into an 8 ohm load, which is also the minimum load which looks about right for a pair of those chips.  The bottom left of the board looks to largely deal with the supply rails for the preamp and I'm guessing the 3rd large device bolted to the heatsink is a bridge rectifier for the power amp?

So to the trained eye does there look to be anything particularly interesting going on here, or is it just a pretty vanilla TDA7294 bridged circuit?
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
October 25, 2018, 05:34:59 AM

They're here and look okay to me.  I'm happy to post one to whoever wants one for cost of postage so they don't go in the bin.
I really should have looked more closely at the number of SMD components before ordering!
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
October 16, 2018, 11:19:21 AM
I should have a set of 10 PCBs in the mail from easyEDA pretty soon.  I've decided that I'm going to rework the design to use through hole components rather than buy a bunch of SMD stuff I'll use once, so if anyone wants one (or more) then I'm happy to send them your way for the cost of shipping.
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
October 09, 2018, 02:02:11 AM
The 2nd to last MOSFET is replicating a cathode follower and the last one is an output buffer/FX send to pad the signal level down is my guess.
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
October 06, 2018, 04:58:48 AM
I think the easyEDA package can do that. I'll take a look when I get back to a computer.
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
September 29, 2018, 02:23:10 PM
I'll probably just use the EasyEDA online editor.  There is a full version too but the online one seems more than powerful enough for my needs :)  It hooks straight into a Chinese PCB fab house that offer silly cheap prices on boards 100x100 or smaller.  I just need to sit down and make a few of my own generic component types when I get back from my holidays. 

I'm kinda curious about the mini poweramp project too.  Shame there isn't a gerber for that (or if there is I missed it) otherwise I'd have ordered some too.  I was thinking it would be kinda neat to maybe run one into a dummy load to feed into a real big SS amp for live use :)
The Newcomer's Forum / Re: Mosfet JCM800 by KMG
September 28, 2018, 06:47:50 AM
For the B+ you can use a ZVS DC boost converter perhaps?  They're only a few bucks on ebay.  I've built an ecc99 poweramp with one run from a laptop PSU.  I also used a similar bucking smps to supply the heaters.

Coincidentally I've just ordered a bunch of PCBs for this preamp from JLCPCB and this will be my first foray into SMD soldering!  If I like how it sounds I may we knock together a design of my own with fewer SMD components and then make the project public on EasyEDA.  I'm happy to have collaborators check on the project if I go through with it as I'm a bit of a PCB layout noob  ;)