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back to normal ?

post #1 of 37
Thread Starter 
so I finally get two days off in a row and finally got some REAL WORK done.Some know that I totally scrapped all my headphone amps (well gave 'em away actually) and had to start from scratch

with a "little help from my friends (I get by ) " ,as in quick parts fix ,the one that started the great "United States Postal Service" rant by our good bud apheared , I finally set up shop and burned up some solder

three amps in one day (plus 90% of my new szekeres amp)

1-Cosmic "knockoff" amp , a classic , hansen board and full crossfeed plus piggy back opamps with 10 ohm load sharing resistors.Dual nines but 16 AA external battery pack.I simply used a DPDT center off switch as the power switch so I could choose between internal or external psu.Gain of 2

1/4 inch phone jack out for my MS-1s ,RCA and 1/8 inch input jacks in parallel for use with anything

2-Altoids Amp , don't we all have one ? t5his one is for fast and light-straight hansen build ,nuthin fancy,gain of 5

3-another hansen but mounted on a piece of pine.This is my test bed-screw the breadboard.With "open ended " construction-as in lots of **** off the board I can experiment with various whacko ideas

4-the NEW Szekeres.Totally dual mono back to the first filter capacitor bank,outpuit mosfets running at +12 volts via shunt regulators with pass resistors,idling/operating current at 5oo ma per ch,dual inputs,totally "retro" in hammerite paint/bakelite knob/big ass power toggle

on the back is the barrier strip for the external psu

Life is sweet to the rickmonster today !

thanks mike , get back to ya soon , gotta get my music fix first
post #2 of 37

Note to self......

......find a way to get on rick's Christmas list.
post #3 of 37
hehe I know EXACTLY what you're talking about

i have almost the exact same cosmic knockoff as you, except i did it on a RS board, and it's powered by 2 9V's in an altoids tin. Paralleled OPA627s, with a gain of 2x, but i used higher load sharing resistors simply because that was what i had lying around...I also used the EXACT same method of PS switching, a DPDT switch- on/off without psu, psu/battery with psu connefcted. I actually found ithis amp a bit "analytical", and downgraded it to OPA134s.

I spent $500 in parts in the last week, all of its lying on my floor... have about 10 projects in various stages of completion scattered about... they include-

DAC! got some of the dac chips, still waiting for recievers. started on output stage and PS arg, dunno when this is gonna get done, you'll definately get mail soon, when i start blowing up $30 chips!

super amp- All audiophile grade parts, such as neutrick sockets, silver wire, noble pot, etc. amp runs off 16AAs, and has AD823 adjustible gain stage, AD823 active filters, adjustable x-feed, BUF634 virtual ground driver, EL2001 buffer output... parts cost-$200, for just about anything.

altoids amp #1- OPA134 gain X 5, jmeier x-feed, buf634 output stage. Single 9V, for Sony CD-3000

altoids amp #2, stock CMOY with x-feed, possibly with paralled opamp output.

2 szeker's amps, still need to pick up trannies, but the rest is almost done.

Small 8AA cmoy with x-feedin hammond case, for Senn HD600

Stock CMOY in cmoy recommended pactec case.

3 big gaincard clones... still gotta get around to the powersupplies and in/out jacks/ cases...

Many many MD interface boxes, basically a big pile of cat5 wire and resistors right now.

several standalone x-feed boxes, working on enclosures, haven't done circuits yet, but they don't take long at all...

portable DAC... arg, dunno if i'm ever gonna get this done sorry rick!

Well one thing i'd recommend to anyone doing DIY is to work on 1 project at a time!
post #4 of 37
Thread Starter 
I hear ya Thomas , so much to do,so little time

And hell yes the portable DAC can be a reall bitch,I still can't get the performance I want with any sane battery life,I may go spdif,gun the toslink receiver and bounce the Cs8412 in favor of the Yamaha chip (tip,salvage old raggedy ass early CDP for parts)

My home DIY DAC is always in motion,mostly the I/V ,filter,output stage.And the "glue logic" has also been updated.Real can of freakin' worms there

But if this sh*t wasn't fun (frustrating ?) I would not do it

Then again , some folks think a stick in the eye is fun !

Drive on

post #5 of 37
Thread Starter 
BTW-what are the filters for

just wondering
post #6 of 37
hey rick, did you ever get that jfet gainstage for the szekeres done?
post #7 of 37
Thread Starter 
actually skippy I did , and would you beleive ?

Straight out of the National Semiconductor Linear Applications Volume 1

app note AN32-7 "high impedance-low capacitance amplifier",a compound series feedback amplifier intended for video of all things,dated feb 1970

I can't tell how long I have had this book but let's just say the damn pages are falling out !

and the most advanced regulator chip is the LM100

Man I'm OLD


forgot to mention ,in the "latest and greatest" version I did away with thextra stage and instead added another output jack to my preamp (also redone) that preceeds the volume control.

in that way I get the gain advantage but do not have back-to-back volume controls.

I also added a switch to this output that disables it.

For those that never read the HeadWize archives I once posted about how the Jan Meire crossfeed circuits are never really out of the signal path if attached to the tape out of a preamp or receiver,there is always some channel blend going on unless some fancy switching layout is done

the simple fix is to totally isolate the crossfeed from the driving device when not using headphones

this is generally a good idea anyway,anything attached to the record out could possibly degrade the signal

simple dpdt switch and problem/potential problem solved


**edit #2**

Long day folks , don't mind the spelling/typos , too damn lazy to fix 'em
post #8 of 37
So box #1 still never arrived? I hope some west nile infected mosquito bites that carrier. DEATH TO THE FACISTS!! Oh, wait, sorry.. wrong forum.

>>5oo ma per ch

Are you doing drugs again? How the hell are you keeping that cool in the summer!?!? Does running it mean sitting it in front of an air conditioner vent? Water cooled, like refit a radiator and water pump for a closed circ system like a car? Heatsinks the size of 1000cc motorcycle cylinders?

Glad to see ya "back in the game" -- what clock did you get for your portaDAC v2? I never got the first one goin (hell never got all the parts, but I got all the books/docs.. thomas? you? were we the only two annoying you, rick?)
post #9 of 37
500 mA, nice...

I changed my 250 mA to 500 mA when I got home this summer, just to see if I could hear a difference (answer is no). I switched back to 250 mA after a few days when the outside of my steel amp case was burning hot, and my headphone plug (on the opposite side of the case from the major heatsinks) was getting hot to the touch
post #10 of 37
rick, the active filter's for a bass boost, so it'll be a "real" bass boost and make the bass louder, not everything else softer (oh yeah, it should have read active fiter, no plural) I'm building it for someone else

I guess that kinda breaks the kiss rule, maybe i should change it to a simple passive lowpass filter....

Yep, for the x-feed, Jan told me (or was it you rick? sooooo long ago )that the only way to use his switch was if there was an input buffer, and the output impedence was essentially 0. Otherwise, you'll get a blending of the channels at all times. So when i wire up the circuit, i use a DPDT switch as rick mentioned. Its kinda confusing at first, the output of the filter goes to the centre of the switch, one pole goes to the input, the other goes to the resistor that connects the 2 channels. When its flipped off, the paralleled resitor/caps get shorted out, the resistor in the middle is disconnected.

Rick, how does the jfet gain stage compare with an opamp gain stage? I'm probably going to use one of those until the DAC is ready...

about the DAC, there's no way that i can use 9V batteries, they'll get drained in an hour. But I think 6 or 8 AA's is good, and still quite portable. Everything i'll use will be low voltage, like CS8412, AD1868, and AD823, and some output buffer. Might not give perfect sound, but seems like a good compromise for portable use...

Apheared- I think we're the only ones, i can't see how he could possibly have answered all of my 10 page long n00b emails, and still had time to do anything else You don't need a seperate clock for the DACs if you use the crystal recivers, they extract the master clock with a pll. I'm lazy, so i'll stick with those chips, even if they draw 50mA.

BTW, check this out-

wait, i'd better not give apheared ideas, next week you'll see (hear?) his "1000watt grado amp"
post #11 of 37
Thread Starter 
Apheared :

No drugs man , residual heat stroke.The last one ran at 750 ma per ch !!!!!!! Yikes !

The cool part is (forgot to mention) I am actually using adjustable bias controls.
5 watt pots.this is a temporary state so I can when I get the time again I will play with the current settings,choose what sounds best then take the pots out of circut and measure the pot to get the final resisor value.

she does run HOT though ,but the heat sinking would suit a power amp of 30 watts if class AB

And no , box #1 is still in the twilight zone , or one happy postal worker is working on his own amp

Thomas answered the clock issue below.The crystal receiver takes care of the clock issue but she is a hungry devil !

And only yourself and thomas showed any real interest in the porta DAC

and yes,it is GOOD to be back in the game again-first bench time since maybe march or so

Whats up next for the rickster ,hmmmm ?

hows about porta ADC with balanced mic inputs (gotta have it)

USB DAC headphone amp

simple mixer (two input jfet mixer) for adding to my travelling horror show.Input one from CD player/input two from my clip on "stealth mics" in a spare tin.Then I can listen to music while still hearing ambient sounds.Strictly a safety measure for work

BTW-the very first walkmans (cassette) had this feature.

all out mongo toy-discret step bass boost with adjustable hinge point/variable five step crossfeed/continuously variable high cut filter---why do I need this ?

I DON"T (heheh),just wanna make it

remote volume control for the pream, I am lazy you see and.......



active bass can controls are the ONLY way to go for true boost

and I could be wrong but I think I was the first to post about the crossfeed issue

A jfet gainstage is OK as a buffer but starts to get more complex when used as a gain stage (cascode,current pump,etc)-still playing around with it

a buffer might be the best solution as the final DAC out

nice amp !

watts per ?

oh well,the rick monster has to go back out into the world today (dammit!) and earn a living for the shoeless kidddies (school starts again soon , means those freakin busses will slow down my morning commute and back to school shopping will tighten up my bolts ala frankensteins monster)

gotta go

rick out
post #12 of 37
what is THAT?????

You guys have a floor broker on London metal exchange? 'Cause you look like you're buying aluminum by ton.
post #13 of 37
I'm also interested in portable DACs. Hey, I could measure the current usage of my own digital section, since it's using nice SMD CS8414; I wonder how much it drains.

I'd think Apheared style AD823/EL2001 in SMD of course would be good for this project? Discrete takes too much space (I still can't believe ppl is calling his amps "portable" - his parts count is almost as much as my DAC which I have trouble fitting into a large rack-size box).

Problem is, where to find portable CD player with digital out? Or, use MD? That would require optical to digital conversion and I believe Rick said that would drain power even more.
post #14 of 37

it's this australian guy that has a amp site up, I think the smallest schematic he's got up is 250w... he has a few other shots of that 1000w puppy, on the bench and stuff... I forgot the url but you can deduce it from the img's url...
post #15 of 37
AOS, yep, can you please measure the current draw of your 8414? That looks like a good choice for a portable DAC. The 8420 assymetric sampling rate converter might be the best choice for portables with tons of jitter, but i heard that it draws 120mA!!!

I don't have the equipment to make PCBs, so i'm sticking with DIPs. I'm planning on using SMT inductors and caps right at the pins of the chips, and to use as little wire as possible by joining the componant leads together to get a decent layout without making a PCB...But if you're planning on making some PCBs i'll be intersted in a few...

I think optical is a must for portable use, all of the high-end North American Sony's have optical out, and all Asian models of all CDPs have them. (you're in vancouver, it shouldn't be too hard to get some grey market Asian panasonics...) Also, i've heard that in North American panasonics, they use the same PCB but just leave out the optical jack. So you could simply solder one in and you now have an optical out... No MDs have digital out, blame the RIAA.

You could tap into the electrical S/Pdif lines in your CDP as its comming out of the transport block, but i would rather use optical out since its already there...

oh yeah, that's not my amp, i just thought it looked cool... I actually saw those heatsinks on sale at a surplus store, i almost bought one to build one for my friend, but i decided i didn't want to risk electrocuting myself/burning down his house...

why do I need this ?

I DON"T (heheh),just wanna make it
exactly! that's what DIY is all about for me

The biggest problem with the active filter is i don't know what i'm doing

I think i'll stick with the monolithic opamps the gainstage of my class-A Mosfet, i still have a long way to go before i can design with discretes. And i think that will also be my output stage for my home DAC, and use the buffers for the portable amp...

and yes,it is GOOD to be back in the game again-first bench time since maybe march or so
hehe, i guess i finally ran out of questions
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