Transformer for Preamp powersupply

Arj Said:

this "Microphonic" could be "Tribolectric"

Yes Sir ! I agree...

That is why I started my 2nd post with :

On the other hand,....

Was presenting 2 sides of the argument

Gave myself a well deserved xmas present.

A new power supply for the pre with some decent caps.

Found a shop the had stock of nichicon, chemicon and elna caps retail qty.

Bought a pair of each. Elnas with 4700mf and the others were availavle only in 2200mf.

This power supply has better filtering than the older one. Lucky o could squeeze all I wanted on the same pcb.

Will set out to make the mainboard again later with better components. Need to find em first :-)


Regards

Manek

Hi

Ampnut, today morning I decided to add some more byassing caps to the preamp supply lines so I opened up the amp.
I forgot to bring in my dmm so went to the other room to get it. I came back and to my initial horror saw my cat had made himself in my amp chasis. He was sitting in it and had a look on his face which said "finders keepers!"


At first didn't know what to do. I gently picked him up and put him aside but the smart alec brought out his claws and held onto to the wires for for a minute my amp was airborne along with him. He released it from his grip soon and the amp took a 4-5 inch drop onto the table.

Checked everything. Showed. No signs of problems so powered it up. Lo and behold it works !

My amp survived my cat !


Manek

congrats !
but am surer those few seconds between lifting the cat, the amp and then the fall must have seemed like an eternity

Blasted cats...aren't they supposed to be dog food anyways Yes yes am a dog person

Glad the amp's working alright..

Arj

Yes it certainly did ! But then I love my cat so all I could do is scold him a bit. Seeing I was angry he jumped up to me, licked my hair and ear jumped down and climbed into his basket.

And that was the end of that episode. Man, he sure can play his cards well !

Yes sachi :-) I know you are a dog person but to me they are both lovely and as precious.
oh yes....one of my cats can make food out of a dog too. :-)

Yep she is playing well now. Good thing I used insulating/vibration absorbing spacers for the board mounting.


Btw got a cd "kenny burrel" - ellington forever vol 2. Awesone burrell guitar experience.

Manek

Hi Manek,

Did I mention here that a friend of mine HAD the Rowland Model 8 Power Amp (US$ 6500 I think ).

His cat peed in it !

Killed it completely !!

Not been fixed despite being sent to the official Rowland dealer about 6 months ago.

Cant speculate what could have gone so wrong... the Transformer... and that apparently took out the electronics when I was switched on ... ?

Ampnut

You did mention it and that's why I marked to post to you :-)


I had a laugh then but it wasn't all that funny when it happened to me.


Urine would have corroded a lot of stuff. Shorted a few more :-)


Cats usually spray on stuff they don't like too much.


Fortunately, all is well here :-)

Hi

My opamp pre has been through many iterations over the last few months but.....
Heard my tubes after a month...the tubes can carry a tune !


Musical are my tubes.....10 seconds into my fave song and I was beaming ear to ear :-)
All that resolution, detail, extension etc just didn't matter....
The music flowing from the phones did !

I guess I will always be a tubie .......kya karega !

Back to the drawing board........


Manek

I have actually switched back to opamps for pre ..

..better transients and less "bloom" in the mids..do have its right advantage

The power amp is still tube....have not heard anything close to the 845's yet.

Yep, I know with all their advantages, the opamps do sound good but
When I played julie london, china forbes and ella back on the tubes after a few weeks of a sabatical with them, they just drew me into the music.


And let's face it, I like the bloom and everything that goes with it.

I played the opamps with tube amplifier and liked it a lot as well. But tubes on their own have a different charm.


I just wish I could describe it better :-)

Manek

I wonder how oil caps would sound with opamps.


Till date I have used electrolytics, polyyester and polypropylene caps on the input and output.

Was contemplating on asking rs to supply a few oil caps to try out if I can't find them locally....


Manek

Manek schrieb:

And let's face it, I like the bloom and everything that goes with it.

That is a hard fact I am learning to accept about myself...Really dont mind some Caramel in my milk

Arj schrieb:

Manek schrieb: And let's face it, I like the bloom and everything that goes with it. That is a hard fact I am learning to accept about myself...Really dont mind some Caramel in my milk :D

Yup...sometimes i miss it too....but can't be switching the pre for different music, unless i can afford some extra money for "automation"

:-)

But to give opamps their due, very clean sounding but not sterile.

I use the opa2134

Manek

Manek schrieb:

:-) But to give opamps their due, very clean sounding but not sterile. I use the opa2134 Manek

Manek, try the OPA2227/8 instead here..

Also what kind of decoupling schemes do you have for your opamps?

Power supply pins have a 100nf ceramic with 47mf electrolytic to ground placed close to the power rails..

Yet to try out a small ceramic across the supply rails.

Is that what was wanted ?

Manek schrieb:

Power supply pins have a 100nf ceramic with 47mf electrolytic to ground placed close to the power rails.. Yet to try out a small ceramic across the supply rails. Is that what was wanted ?

Make sure your 100nF ceramic is of COG/NPo dielectric.
At the very least use X7R dielectric ones cause i think COG ones might be scare to nil in India.

Up the lytic caps from 47uF to 220uF.

And use a Styrene caps if possible of about 1uF or greater across the rails.

Hi

Thanks for the tips but dony seem to get why the jump from 47mf to 220mf. I thought 47mf was plenty in a decoupling role.

Tell me, how will this help ?


Across the rails, polystyrene I will definately do. Th ceramics I used were the ordinary ones available at lamington road.
I was thinking od swapping the ceram$is with polyester/polystyrene at some point.


The power supply hss 4700mf and 100nf at the input of the regulators and 100nf and 100mf at the output of the regulators.

Using the ubuquitous 7815 and 7915 currently.

Will use lm317/337 later.


Manek

Manek schrieb:

Hi Thanks for the tips but dony seem to get why the jump from 47mf to 220mf. I thought 47mf was plenty in a decoupling role. Tell me, how will this help ? Across the rails, polystyrene I will definately do. Th ceramics I used were the ordinary ones available at lamington road. I was thinking od swapping the ceram$is with polyester/polystyrene at some point. The power supply hss 4700mf and 100nf at the input of the regulators and 100nf and 100mf at the output of the regulators. Using the ubuquitous 7815 and 7915 currently. Will use lm317/337 later. Manek

As for the larger capacitance value, it shows a lower impedance path from rail to ground for noise in the power supply.

If you don't find styrene caps of 1uF or greater then try going in for MLCC caps to user across the rails. you might have to experiment here and really to get good results you need a scope.

Those nasty ceramic caps need to go first however.
Make sure the lytic and the ceramic COG caps are as close to the rail and gnd pads as possible, as close to the IC as possible.


For the power supply, instead of the LM337/327 better would be any of the drop in replacements for the 7815 series regulators from Linear Tech.

You could also try a simple circuit using a TL431 shunt regulator with very good results.

Tks again.

But I have bought the 317/337. Really funny....all lamington road shops i knew of
had 317 from fairchild and 337 from st micro.
Couldn't find both from the same manufacturer !

I guess they will have to do for now.

Actually I want to do the whole build again. I have soldered and desoldered stuff on those boards many times and they are now showwing wear.

Hoping to make it neater this time round.


Manek

I may be halucinating here but the combo of keltron electros with dec polyester caps doesn't sound bad at all !
The most readily available capacitors around at lamington road after the ubiquitous "samwa" caps.

Very suprising....their website also had pictures of low esr caps and metal film resistors.

Ampnut, its the ck electronics guy who recommended these over more expensive types.


Manek

Sorry Manek. Keltron caps are not for Audio.

Infact nothing that is available in India is good. Try RS Components and get some panasonic.

I get mine from Digikey.

Regards
Siva.

sivat schrieb:

Sorry Manek. Keltron caps are not for Audio. Infact nothing that is available in India is good. Try RS Components and get some panasonic. I get mine from Digikey. Regards Siva.

Agreed...get Panasonic FC caps..

FWIW.... My 2 cents:

For an op amp based design, you can easily eliminate All Caps in the signal path (ofcourse the Power Suply needs Caps ) completely, by using Direct Coupling throughout,

In most cases, the Input (CD Player) and Output ( Valve Amp in Manek's case ) are capacitor coupled anyway, and will take care of minuscule offsets if any ...

Most designs are made comprehensive as stand alone products, but DIYs have the extra luxury of synerdysing their SYSTEM design, atleast to some extent.

No guys, they do some things rather well like the vibraphone, waa waa trumpet, tom toms.

Yes the bass became monotonous :-) and a bit bloated..


I will get my panasonic fc caps later. I use rs components mostly.

This was an out of the blue shot since I has two spare in the box.

I am going to switch back later.

Manek

Got some decent quality eyelet board. Thinking of building the power supply on those.

Should be able to solder components both sides. Let's see how that works. Components seem to solder better on them


Manek

Guys !

I swapped out the conventional EI trans former for a torroid made by torotrans of pune now more than twice.

The choice is clear, the torriod stays in. Somehow its cleaner and better bass control.


Manek

Not everyone makes good EI Core transformers...quality of the core used is very important...plus the quality of winding also matters....so do not make the decision yet.

Correct

My EI 's are locally made beco brand. Just something I picked up from a shop at lam road for 100 odd bucks..
The torroid is a custom built and built well. So the results are proportional to the quality.

I have also spoken to argo for a good EI for another project so when I get that I will try again.

But the difference is stark.

Manek

Manek, if I may suggest, do give some thought to building a Cavalli Audio EHHA to use as a preamp. I just can't recommend it enough. True enough the Stacker 2 is better than the EHHA, but the stacker 2 isn't a published design yet, else I would share it with you.

I reckon you could probably build the EHHA for about INR 20,000 everything included.

Thanks for the recommendation saachi.

My next project is a source mod. Reading up on it .

Post that the pre you recommend.

By that time I would have tweaked my present pre some more.

This hobby needs so much of one time. Don't have enough spare to do justice.

Manek

Heh no kidding Manek..I succummed once again to this addiction ( sometimes i think it is more than just an addiction..more like an affliction ). Picked up an Akido dual mono Line stage HV preamp/headphone amp kit someone was getting rid off of. at 65$ it was too tempting to pass up on. However I have promised myself not to touch it for a while.

And speaking about EHHAs..her's what i got finished up this morning trying to clear off my DIY projects here in my spare time.

Another EHHA build ...

http://img80.imageshack.us/img80/5830/ehhano2001.jpg

http://img195.imageshack.us/img195/7715/ehhano2002.jpg

An eXStatA build in progress...waiting for some parts so I can finish up the input wiring.

http://img23.imageshack.us/img23/4802/exstatalarry001.jpg

http://img199.imageshack.us/img199/1601/exstatalarry002.jpg

This'll be the last build for a while.

And how long would that "while" last ? A week, 2 weeks at the most ?

Hey ! I was thinking about a 2134 opamp based analogue output stage for the source,
once that works then try a hand at a discrete module.


Any ideas ?


Manek

haha..I am actually handing over the entire kit to my friend for err safe keeping .. rather keeping me safe and away from DIY activities for the time being.

Regarding the output stage, are you looking to implement a full output stage, that is including I/V and reconstruction filter or just like a buffer stage that you want to use outside of the DAC?

Safekeeping with a friend ! Yes that'll work ! Sure :-)

I was looking to build a buffer first, then the i/v etc.

Baby steps for me pls.

Can't go the whole hog at once.

Manek

heh..

well for a buffer, I would suggest looking at something like a simple diamond buffer instead of the OPA2134. let me dig up some links for that and post back. Should be able to easily build it on a perf board.

Thanks sachi


What got me thinking was pavel macura's website and his audio buffer.
Have a look when free pls.

Manek

Looks like a basic buffer Manek.

The big brother of assemblage DAC 2.7 that I have (Also the 2.6) the DAC 3.0 and DAC 3.1 use a very similar buffer ableit without the R12 terminating resistor and R10 being 10R instead of 50R.
I think a diamond buffer using basic BJTs will outperform such a buffer handily. The reports I have heard about the 3.1 and 3.0 in SE mode is supposedly lower compared to the SE cousins (2.6 and 2.7). This is mainly attributed to the BUF64 chips.

If its simple let's try out a diamonnd buffer.

What kind of power supply would be needed ?

Signal paths shorter by approx 50%. Board size reduced. Better grounding scheme. Better Opamp decoupling.

It sounds bit better in all respects.

All compenents are fresh so I will give it a burn for a few hours.


Manek