Pics of Tamas' Preamp

[tk@halmi]

Hello,

This is a preamp that I started building for myself, but a friend has put a claim on it so it will go bye-bye in a few days. :sad:

Dual stage with a bandwidth that took several hours to tame.
It started as a dual servos, but after comparing it with Sanyo KZ electro caps I ditched the servos.

http://mysite.verizon.net/res75okq/sitebuildercontent/sitebuilderfiles/EtudeFullFront.jpg
http://mysite.verizon.net/res75okq/sitebuildercontent/sitebuilderfiles/EtudeLeftFront.jpg
http://mysite.verizon.net/res75okq/sitebuildercontent/sitebuilderfiles/EtudeRightFront.jpg

The wiring could be tighter, but it is pretty solid right now. The PS and the preamp boards were supplied by JLM Audio.
http://mysite.verizon.net/res75okq/sitebuildercontent/sitebuilderfiles/EtudeInside1.jpg

Showing off some home-made discrete opamps here. They are FET input/BJT output, still in the improvement cycle, but getting closer.
http://mysite.verizon.net/res75okq/sitebuildercontent/sitebuilderfiles/EtudeInside2.jpg

PS.:
Yes, the transformer's electrostatic shield used to be a can of baked beans. :grin:

Tamas

 

[owel]

Very nice Tamas! I love the labels on the LED meter... Close, Closer, Clipping. You can just shout to the engineer "Hey, you're getting Closer!"

 

[soundguy]

damn, the can around the power transformer is a brilliant idea. Sometimes the most obvious things... I have to try that for sure!

Those relay switches look really cool, Ive never seen those before, what are they?

Front panel looks awesome!


dave

 

[tk@halmi]

[quote author="soundguy"]Those relay switches look really cool, Ive never seen those before, what are they?[/quote]

RadioShack paddle switches. :green:

[quote author="soundguy"]Front panel looks awesome![/quote]
Thanks. It was manufactured by Front Panel Designer LLC. Its design was the most time consuming aspect of the entire unit. Now it looks simple. LOL.

 

[SonsOfThunder]

Beancan! Beancan! Beancan! Beancan! Yeah! :thumb:

Not to seem picky but I can't tell if you took measures to make sure that the can does not short out on the chassis at the bottom? That could be baaaaad!

Maybe everyone else does, but I don't recognize the o/p trafos???

Niiiiice front panel! And I like the look of the switches but I have always had terrible service from Ratshack switches. Possible a C&K copy?

HTH!
Charlie

 

[jrmintz]

Beancan! Beancan! Beancan! Beancan! Yeah!

I don't think so - I think it's a cat food can: mew-metal.

Great job Tamas!

:thumb: :thumb:

 

[josan]

So what's the deal where the bp caps are on the JLM boards

 

[fum]

That looks really great, Tamas :!:

It's always inspiring to see other projects. Keeps ya motivated to do stuff. Thanks for sharing :thumb: :thumb:

ju

 

[JLM Audio]

Tamas looks great but extremely DANGEROUS.

You have made a shorted turn around the transformer with the way you have put a earth lead on the top off the can and toroid main bolt (even if the can isn't touching the case). Never earth the top of a toroid main bolt as this bolt is already bolted to the case and this will form half a turn on the toroid which will modulate the earth about 300mVac. Then if you do like you have and earth the case as well you have formed a shorten turn of about 300mV at huge current which will overheat the primary winding of the mains transformer.

Only bolt the mains earth to the case and you can also earth the tin can but it must be insulated from the toroid bolt so a shorten turn is not made. Never bolt a earth on to the top of a toroid as this is a bad earth point due to all of the above reasons.

Joe

 

[Steffen]

great looking pre Tamas!

@Joe thanx for pointing out that xformer screening thing...2 of my units use similar screening (grounded sheet metal on top of the xformer). these are running ok for a while now but but I´ll have to take a closer look agian.

steff

 

[dramadisease]

can i ask, did you do the pcb layout for the meter board and is that available by any chance? if so, would you also have a drill template for it? it looks real nice and ive been wanting to do led metering but im sketched on the perfection the drilling has to be. one wrong move and your whole front panel is f*cked!
-bryan

 

[peter purpose]

Beautiful job Tamas... :thumb: Your own op amps in one channel too.. :thumb: :thumb:

Velleman meter pcb's?

 

[Flatpicker]

Great job! :thumb:

I?m assuming the Sanyos are between the op-amp's output and output transformers? (Output transformers look like Jensens, BTW.) Can you tell us a little about why the servos didn?t work out? Just wondering, because you?re not the first I?ve heard this from. Also any particular reason you chose the Sanyos over Panasonics?

Just curious about this stuff!

 

[Bauman]

:thumb:
Top stuff! I like the VU labeling very much.

So what was the audible difference between the Caps and the Servo, to you??
Are this caps easy to get?

cheers!


:sam:
Fabio

 

[jensenmann]

This box is a beauty!!! :thumb: Great work!
Was there a reason for the can? Using torroidal trannys should be enough protection against interference.
Is there an audible improvement from using LL1538XL instead of LL1538 or is it only because of the increased +3dB headroom?
In your next design you should find names for every LED :green:
Big respect
Jens

 

[tk@halmi]

[quote author="JLM Audio"]Tamas looks great but extremely DANGEROUS.
You have made a shorted turn around the transformer with the way you have put a earth lead on the top off the can and toroid main bolt (even if the can isn't touching the case).
Joe[/quote]

Holly-molly! I would not have figured that in a hundred years. I just removed the grounding wire.

Big Thank You,
Tamas

 

[NewYorkDave]

Looks very nice, Tamas.

Were you an audiophile in a previous life? :wink: I ask because "Etude" sounds like a name you'd find on a piece of high-end hi-fi equipment.

 

[kent]

SWEET!!

Makes me want to stop labeling my boxes with crayons.

Cheers,
kent

 

[rafafredd]

Very nice. Beaultiful, I would say.

Congratulations on this new box!

 

[tk@halmi]

First, Thank You Everyone for the encouragement!

Some answers to questions:

Maybe everyone else does, but I don't recognize the o/p trafos???

Bauer Transformers: 11-DM (Same as JT-11-DM for 2/3 of the $)

Can i ask, did you do the pcb layout for the meter board and is that available by any chance?

It is a Velleman kit from hobbytron.com. :green: The two channels cost $24 plus shipping. It would have cost more to make them myself (time is money too).

Can you tell us a little about why the servos didn?t work out? Just wondering, because you?re not the first I?ve heard this from.

Sorry, no quantitive analysis just listening tests. The servo sounded like it was messing with the mids and lows (several observers reported so). Most likely, it was an implementation problem on my part, but I ran out of patience. With good capacitors being so cheap these days it is very tempting just to stick with them.

Also any particular reason you chose the Sanyos over Panasonics?

Tried Panasonic FC and they sounded pretty much the same. The reason for going with Sanyo KZ caps was their rating at 10,000 hours life.

Was there a reason for the can?

Did not have it in my last project so I thougth I would try it.

Were you an audiophile in a previous life?

I used to fix TVs, VCRs, and audio equipment to pay for my college in the '80s. (Yes, back then it was actually profitable to do so.) In the shop, we used to laugh at the names of some of the audio stuff, just sounded so out there sometimes. I could not afford anything more than a boom-box at that time though.


Cheers,
Tamas