[rickcr42]

well kiddies,the rickster has had some time on his hands recently and just could not leave **** alone as usual so the szekeres is going through a total rebuild.I like the direction it is going in and other than A BIG FKN DIG IN THE FRONT PANEL all is going smoothy
Changes are -

1) new layout, everything is on the board this time except for R5 which allows me to experiment with various currnt sources at a later date,leaning towards anothr IRF510 here but power resistors for now

2) Backing off on the ridicuous amount of current so smaller pcb mounted heatsinks are now possible

3) the former "monster heat sink" that is on the back panel now serves as the regulator heat sink using an LM350K.I may add shunt reg voltage reference,dunno yet.This is followee by four 10,000 uf caps in a R/C/R/C configuration for interchannel decoupling and filtration (regulator to the junction of two 10 ohm 2 watt power resistors,then on to left/right channel CRC filters),all cap negatives are tied together with a copper buss for the star groundind point.Will add 10uf across each final cap when I order more

4) simplified the control layout so the front panel only has a on/off/on switch (for external psu comparisons),on LED,volume control and output jack.I got rid of the former mute switch that was the former input 1/input 2 switch-not needed sooooo...see ya.Did leave me with a small front panel hole that needed plugging but looks fine and allows me to maybe add another whacky feature later

5) still have the rear panel input and "through" jacks and am using a barrier strip for power buss input to the regulator.This baby has seen everything from dual input,quasi dual mono input,mosfet/jfet supply input.Now it is external psu input to compare with the internal when I get "the urge" to do psu 101.Could also use the extra connections to output +12 volts to power other gear .

I think that's about it.Should finish this baby today some time and if all goes well post pics by weeks end with some layout ideas for those needing some guidelines.And though using a stock radio shack board I do have on paper a pcb layout that I may make available to first timers,though not really required.One thing about this amp-it is all power supply.The basic amplification circuit is a minimalist design but the psu is where the real work/cash is.I have tried every conceivable configuration here and at this point I think I have arrived at the best tradeoff in performance/implementation : External transformer/rectifier/capacitor filter/pre-regulator,all with proper bypasses and rf filtration,output -----------------------------amp box with final regulation and filtration with interchannel de-coupling.
Can't wait to plug 'er in and just enjoy the music

BTW-I know some have been waiting to see what the rickmeister considers "art" as in amp casing.Well I lean a bit towrds an era when even commercial products had a kinda DIY look-very simple and clean with easy access to an interior made for ease of service/modification.This amp has what I consider those qualities plus a "retro" look with a charcoal hammerite finish,big ass chrome toggle switch with the on off plate , a chrome bezel LED power indicator for that neon lamp look and of course a plastic volume knob with 0-to-10 markings like a guitar speed knob but bigger.Only thing missing is a tube glow !
I have all the high tech switches and solid aluminum knobs but that got old as in boring.I like this look better,soothing in some way.Yes I am not normal

(should see what I am doing to my preamp ! totally gutted it and threw the chassis away,never to look back ! Controls are now way simplified,no special feature,all top mounted "console" style .The in/out jacks are also now top mounted for easy access when plugging/unplugging which all DIYers do constantly,and front mounted phone jack for the record ouput and a parallel main output for quick headphone amp jacking in.Wood cabinet included of course !)

Just touching base ,and the evil rick just wanted the anticipation to rise waiting on those WAY TOO LATE pics-back to work I go

 

[paulb]

Pictures'd be good, looking for ideas.
Are you staying with the basic Szekeres, no dual supply or op-amp feeding it, anything like that?
I'll be building one into a power amp case shortly, had some extra room and I'm having more fun with the headphone amp than the power amp I started with.
Went through a few iterations and settled on the basic single supply version driven by an op-amp with a bit of gain. Lots of room for heatsinks and winter is coming anyway.

 

[rickcr42]

actually pretty stright from the original schematic,just with premium parts and mostly power supply implentation-the key to this amp.It really does need a clean source of regulated DC. All together I have 50,000 uf from the rectifiers to the mosfets not counting the bypass caps

The final filter stage as stated above is 10,000-10 ohm-10.000 for each channel.The other 10,000 is the initial filter after the rectifier .
I have no need for a gain stage due to my program sources having enough voltage to drive the amp directly from the record output jack on my preamplifier
Eico mono tube FM Tuner
Modified Radio Shack microphone/phono preamplifier
DIY mixer with input from the video system audio switch(VCR-DSS-DVD)/instrument input/dual mic input

And even if I did need more gain I could just hook it up to an output on my preamp that I added which bypasses the volume control so is full gain.When using a portable CD player I just use a pocket amp inline before the szekeres amp.As you can tell I go out of my way to keep my system in separate "blocks" which for me is needed due to my continuous pluging in new projects for testing or for outdoor parties where the configuration changes.I can format the sucker any way I want without pulling everything out due to top and side mounted jacks.Works for me man

And the amp did NOT get done today,90 % of the chassis is wired,the regulator card is done,the amp board is four resistors and two mosfets away plus wiring it in,the resistor board is done,just needs installation.
The holdup ? Would you beleive four resistors I thought I had but don't ! (don't say it aos

) and reconfiguration of the filter cap board means a trip to the shack.But it was EIGHTY DEGREES HERE TODAY

,the rickmonster had to roam some

 

[paulb]

Clean DC, yes, no PSRR to speak of. 50,000 uF, wow, course that would just get you started at the diyaudio.com site. Going over the top with headphones is so much easier.
Gotta get new cans before the recession kicks in...

 

[Tomo]

Hey Rickman.

Take this as a complement. You are crazy.

I have been taking EE class and I just learned a wonderful thing about the constant current supply. Now I understand why it makes the amp more linear. It make it more linear by increasing the voltage gain of MOSFET. (This is not the voltage gain of the amplifier. This, I think, is more related to slewrate.)

Tomo eats CMOS for lunch

 

[rickcr42]

Quote:

Take this as a complement. You are crazy.

Shhhhhhh...don't tell anyone

So stepped away from the project for a couple of days,shuld be done tomorrow and looking to post the pics around monday.Funny thing,I was laying out the external PSU chassis which is being built into an old car battery eliminator supply that puts out 5 amps at 12 volts unregulated.I figured to use the basic supply and just add to it.I start cutting out parts and I see light coming through the back panel

What ?
I hold it up to the light and DAMN,it is pre-drilled for a TO-5 regulator

Now I am both happy and pissed.Happy because I can intall the LM-350/heat sink/regulator card right on the back panel .Pissed because I was going to originally put it in the amp case AND I had already hacked up the original supply !!!!!!!!!!!
All I had to do if I had known was to hack out the cheap ass 4700uf electrolytic and add my regulator and caps.DAMMIT !
But everything fits so well that I know it WANTS to be there , so in it goes .
Now I have this big ass heat sink sitting on the back of my amp with nothing on it,it looks lonely.So that will end up being sort of a kluge area to test out various current sources when I get the urge to screw around with the amp again,and I will.The only layout change was to spin the pcb around so the in/out faces the other way.What could be simpler

I'm gaining on it guys

BTW-thinking of adding a walnut cabinet,top and three sides,not this week,but had some scrap pieces laying around and doing a mock-up showed promise.

 

[paulb]

I know what to do with that heatsink. Make a capacitance multiplier. Then compare the performance with it vs. the big honking caps approach you're using now.
And let us know...

 

[rickcr42]

might be something to do a couple of weeks down the road,wanna use the amp for a while first,live with it so i can tell any differences.I have had this amp apart sooo many times it has had more down time than in system time,not good when it becomes the equipment and not the music.
I am still amazed how good the ecasing still looks after all the surgery it has been through.Other than the recent front panel scratch which MUST be touched up (and this is not going to be good,I doubt hammer paint touches up well) there are a couple of minor markings around the output jack from plugging in after a few cold ones (knew I shoulda covered one eye dammit

)

Still looking to post pics monday

 

[rickcr42]

looking at Tuesday or Wednesday,not my camera guys,hang tough

 

[Apheared]

Go on a shooting spree when you get it... well, yea, that kind too. with the camera.

 

[rickcr42]

hehehe,i knew what you meant dude

And yeah,kinda owe it to all the knuckleheads that have been following the "Tales From The Rickmonsters DIY Nightmare Workbook" for these past coupla years

Patience children,hehehe

BTW-I really can't wait to get the SZK up,came out really nice considering it started out in life with a Radio Shack enclosure and a 20 year old junkbox knob,though still looking for THE KNOB.I will know it when I see it