DIY 1272 for Newbies? C'mon.

[JLM Audio]

You can use a 10k linear with a 5.6k resistor between the wiper and gound to make it audio taper like Neve did. Or a 10k log or 5k log pot
or any of the combinations shown on the pdf link below and other links for general info.

http://www.jlmaudio.com/JLM%20Module%20&%20BA283.pdf

http://www.jlmaudio.com/JLM%201272%20Switch%20Kit.htm

http://www.jlmaudio.com/Neve%20transformer%20info.htm

http://www.jlmaudio.com/neve_ba283.htm

Joe
www.jlmaudio.com

 

[giobinein]

:shock:
Thanks Duka and thanks Joe !!
Are there any difference (in sound result) between 2N3055 and 2N3055H ??

 

[giobinein]

http://i5.photobucket.com/albums/y163/giodiy/neve1.jpg
http://i5.photobucket.com/albums/y163/giodiy/neve2.jpg
http://i5.photobucket.com/albums/y163/giodiy/neve3.jpg
don't look at the missing frontpanel and don'look at the confusion and disorder because it's only the proto of my two channel of 1272(but it works great :grin: )
I've used Sowter input and output trafo (Carnhill are too expensive!! )
Thanks to Joe for the schematics, thanks to Tekay for the PSU (I'm using LM317 instead TL783 for the +48 and so far no smoke :grin: ) and thanks to all for your support !!
How can I add a line input and an instrument input to this pre??
Thanks !!

 

[JLM Audio]

How can I add a line input and an instrument input to this pre??

It would be very easy with the right couple of kits. :grin:

http://www.jlmaudio.com/JLMDI.htm

Joe

www.jlmaudio.com

 

[Family Hoof]

giobinein,

I was waiting to post this but you've inspired me to do it now! Fun to see someone else doing it on perfboard (your power supply, that is). What type of polystyrenes are you using and from where? Ignore my power supply since it's just something I threw together with parts on hand and not fully hooked up. I'm still trying to design one that satisfies. The input transformers are JLM1:4 (Thanks, Joe!).

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[Svart]

holy shit Jens! that frontpanel is the shit!!

 

[giobinein]

:shock: beautiful (and very clean) work Jens
All the components I'm using are from Farnell included the polystyrenes caps.

 

[Family Hoof]

[quote author="Svart"]holy shit Jens! that frontpanel is the shit!![/quote]
Thanks. It came out like that for two reasons: a) absolute lowest cost using Front Panel Express, and b) I've always dreamt of gear with almost no markings so I'm forced to use my ears only.

 

[alexc]

Hi all,

here's my first 1272 go - Fabio boards with hiZ, JLM power supply, grayhills, sowters, motorolas and polystyrenes.

not finished because it sounds so good, i've been using as is for a while now. its fabio-lous. low noise, full range sound with *crunch* :green:

thanks to all the people here.

"websters dictionary defines 'excellence' as the quality of being excellent"

i think this place is excellent. :sam:

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[matta]

Wow!

Alexc, your Pre's look great! I have 2 of those boards on order with Fabio, can't wait to stuff them!

I assume you are using the Sowter 8751 on output and the either the 9002 or 9145 on input.

My question is how do the input mount on the board? From the Sowter website it doesn't look like you can bolt them to the board with the holes Fabio provides.

I can't wait to build mine! Post more pics, would love some close ups.

Cheers

Matt

 

[Bauman]

Well done Alex! :thumb:

 

[alexc]

Hi Matta - thanks for that!

The transformers be Sowter, 8751 and 9145. The input one bolts on just right and should be insulated from board.

I'll post more pic as I get the hang of close-ups.

I'll finish just as soon as I stop playing my guitars thru it! This is a forceful pre! I use it with (gyraf and the-chef) gssls and I'm *real* glad I tried diy.

Tricky bits are finding some pcb-pin sockets and pins that fit, power supply heatsinks (still to do), wrestling the opamp board onto sockets, and working the grayhills into the board.

Rest is pretty easy. I enjoyed greatly.

Soon to try more from all the great contributors that make it fun.

Bye

 

[Svart]

now which caps are supposed to be polystyrene?

 

[alexc]

Hey, thanks Fabio.

 

[alexc]

i used polystyrenes 'round the front transistor of each stage

100pF , 220pF , 330pF, 680pF, 1000pF, 1500pF, 4700pF

half of them are blue, half of them are clear (in colour)

 

[Svart]

so that leads me to ask, would one think there would be a signifigant change in sound if I used high quality polyester?

 

[Family Hoof]

[quote author="Svart"]so that leads me to ask, would one think there would be a signifigant change in sound if I used high quality polyester?[/quote]
If you look at the BA283AV schematic and the original units it shows that any electrostatic (non-polarized) cap is supposed to be a polystyrene. The only exceptions are the zobel caps for the input and output transformers which are polypropylene film.
Some of the comercial cloners use other types of caps. For example, Seventh Cirlcle uses ceramic, and based on pictures I believe the Dan Alexander uses polyester. Does it change the sound noticeably? I don't know yet. It's on my to do list. Do these clones sell well and sound good? Yes. In the meantime I feel good knowing I've used polystyrenes. Nostalgia is worth the effort, IMHO.

[EDIT] On second thought I think the Dan Alexander might use polypropylene. Some group DIY members have already reported no audible difference using polystyrene or polypropylene in this circuit. No surprise there.

 

[maneco]

In the "real neve " boards,were the resistors metal film?
Thanks!

 

[Family Hoof]

[quote author="maneco"]In the "real neve " boards,were the resistors metal film?
Thanks![/quote]
From what I've been able to determine they had a variety. The 183 boards had beyshlag 1/2W resistors with four bands. I guess these were carbon, but they had tolerance band colors greater than silver or gold which you'd usually associate with metal film. Indeed they were rarely out of tolerance. I think the schematic called for %2 throughout. The 283 cards on the other hand had 1/4W metal films (5 band) that were dark gray/green. I don't know the brand yet. R7, the 47ohm was always a 1W beyshlag. Many 80 series modules would seem to have metal films i.e. blue in color and tolerances than 5%, but again there are only 4 bands. I've always used the number of bands to distinguish and don't yet know enough to make a conclusive statement about these old ones. Maybe I'll disect a few?

 

[maneco]

but is it possible to tell the type of resistor just by color or number of bands?i thought that had to do with the tolerance and value series,but not with the difference between carbon or metal...