Greg

Hotrod Build Thread
« on: April 29, 2006, 04:14:31 PM »
For anyone just stumbling onto this project, here's a brief history:

Some time ago, I was browsing the JLM Audio website, and came across his schematic for the JLM Hotrod Mod. This takes a Neve BA283AV line amp and converts it into a mic preamp (ie the 1272). I decided to whip one up point to point, and I absolutely loved it. I decided I wanted more, and designed a PCB for the project. After a bit of stupidity on my part, I did get Joe's blessing to fab the boards and offer them to people here at Prodigy Pro.



If you're interested in boards, head on over to the Black Market.

Here are the basic components you need for the project:
1. PSU - +24VDC and +48VDC (if you want phantom)
2. BA283AV
3. Hotrod board
4. JLM "Go-Between" and/or "DI" (optional but recommended)
5. Input and output transformers

Some helpful information:
1. JLM Audio Hotrod Mod Schematic
2. Hookup Instructions/BOM
3. Parts List that may be useful for additional information.

My completed build:
http://www.groupdiy.com/index.php?topic=17697&highlight=

This should get things started. Post from here as needed.
Greg Stein
New Orleans, LA


Kev

Hotrod Build Thread
« Reply #1 on: April 29, 2006, 07:31:51 PM »
I'm suprised more people haven't been into this one

Back at the old place the BA283 was the hot project
but towards the end and here
the API/Gain Block and DOA in general are the hot projects
Kev
DIY Factory

dissonantstring

Hotrod Build Thread
« Reply #2 on: April 29, 2006, 07:59:07 PM »
whatcha talking about kev! :mad:
(i actually wanted to put a face of gary coleman, but i'm too lazy to search for one). :grin:
-grant

edit: i just saw the new layout for the hot rod mod greg! :thumb:  awesome!

Greg

Hotrod Build Thread
« Reply #3 on: April 29, 2006, 08:34:54 PM »
Kev:

I just shipped out a bunch of boards, and no one has gotten them yet. I'm expecting this thread to pick up some steam when people start getting their boards. I just wanted to make sure the info was out there so people could start sourcing if they want.

I'm waiting on my front panel to come back from engraving, so I'll post some pictures of the build as I progress.

I think this project is a good one. It's a good combination of having some stuff some done (like the boards and parts list), but at the same time the builder will have wire the I/O trannies and deal with the power supply and pad, polarity, and phantom. Also, the output transformer loading is offboard, so some thinking will be required.

To me, this project is much easier than say the GSSL comp, so maybe some the newbies will try it out.
Greg Stein
New Orleans, LA

Kev

Hotrod Build Thread
« Reply #4 on: April 30, 2006, 04:30:38 PM »
Quote from: "Greg"
I just shipped out a bunch of boards, and no one has gotten them yet.

as you said,
this makes a 1272 very easy if you have an original BA283
and
just as adding the JLMswitch kit makes it a 1290

we had a couple of variants of your board at Tech Talk in both Etched and Bread Board styles.

so it has always surprised me that we haven't seen a more organised approach just like yours

or
a power supply and switch kit rolled into one board with an edge connector ... would also make a great BA283 test and service board

why didn't I do it ?
cos
I've never owned a BA283 card and so just made my own with screw terminals etc ... and one or two of the other projects like Pete V's layout for the 1290
Kev
DIY Factory

Hotrod Build Thread
« Reply #5 on: April 30, 2006, 06:15:06 PM »
well I have a couple things, I guess.....

I'm doing the 2n3055's on the ba283, and I got the same heatsinks greg gets....  they're pretty darn close to the leg of r6, in fact the case of the 2n3055 is as well.  Do you use heatshrink on that leg of r6 or anything?  if it touches the case of the 2n3055 or its heatsink, will a short occur?

Also, about the general layout, does anyone have a good idea for getting everything in the case?  I'm trying to figure out how I want to mount the edge connector... I was thinking about using a metal divider screwed to the bottom of the chassis, with cutouts to mount the connectors.  I dont know however.

I guess I'm wondering what is the critical run for this.  Is it more important to keep the gain switch wiring short, and have the hotrod board up front, or is it more critical to have the mic/transformer wiring short, and keep the hotrod towards the back or the middle.   I don't have the experience to know what will be most problematic as far as noise in the box is concerned.

Also, and I know how lazy I am for doing things exactly as greg has, but he seems to have had some success getting a nice sounding pre, so....  I'm going to try what works for him.  Anyway, I have a bauman psu board, although I wouldn't mind saving it for the 312's I have coming along.  I can use it, but I'd rather figure out something else.. is there something good that'll work, even a home etch design?  

And I have assumed this thing took bipolar 24v, but is it single rail +24v in fact?  That could make the PSU pretty simple and maybe a cut down green pre or Keith PSU could work.  I don't think, even if he had posted the layout, I would ever want to try and home etch a bauman psu.  those little tiny gaps!

anyway,   just trying to put some fuel on this fire

billy

Greg

Hotrod Build Thread
« Reply #6 on: April 30, 2006, 10:31:34 PM »
Billy:

Regarding the 2N3055, I went to my local hardware store and bought some nylon standoffs and mounted the 2N3055 a 1/4" or so off the PCB so it would clear R6 with no problem.

Regarding the case, I recommend putting the BA283AV towards the back and the Hotrod towards the front. I've still got to find some little "do-dad" to mount the BA283AV... I'll let you know when I find something. To be honest, I haven't really looked yet.

Regarding PSU, this is not a bi-polar... it's a single +24V rail, and phantom if you want it. For this, a perfboard PSU would not be a problem. I have several Bauman PSUs lying around, so I made a couple simple changes and it works great. If you're interested, I can post what I did. Let me know.
Greg Stein
New Orleans, LA

EEMO1

hey!
« Reply #7 on: May 01, 2006, 03:03:38 AM »
yeah, please! i got some bauman psu's on the way!

Hotrod Build Thread
« Reply #8 on: May 01, 2006, 11:36:43 AM »
regarding the 2n3055, the nylon standoffs sound perfect.  I'm going to pick some of those up.

As far as the connector, I was looking at a fairchild reverbatron that has no spring tank, and it has two pcbs on card connectors, very similar.  And I may take it as inspiration, because it has two very simple L shape brackets with holes, mounted to the bottom of the case, and then the vertical section of the "L" sticks up with another hole and holds up the edge connector.  Perfecto ;]

I'm going to see if there's anything that works at the hardware store when I pick up some spacers.  Good chance there is.

And re the bauman psu, I have (1)....  I also have everything, pending that API/cinemag group buy, to finish my 2x312.  I think my (1) bauman psu should be used for my api's, as I need all of its features, bipolar/phantom/relay rail.

so breadboard I'm thinking.  Which is good, I've been meaning to breadboard something aside from a pc mount power transformer, for the learning of it all.

So cool... this thing is going to come right together.  I may also build a 'brianroth' or a 'nyd,' so to speak, vu buffer, maybe that 'superbal.'  I think I might hang these metermod's I have in here to kind of beef up the sound with some discrete VU's.    

;]

billy

sintech

Hotrod Build Thread
« Reply #9 on: May 01, 2006, 12:56:55 PM »
Greg, I'd love to know what changes you made to the Bauman Psu also please. :thumb:  I'm going to be using it to power a pair of point to point Hotrods.

I've stuffed the 312PSU for just +24 and +48. I have +24 no problem, but the phantom power worked out at 44v.. will this be an issue?


Greg

Hotrod Build Thread
« Reply #10 on: May 01, 2006, 01:23:37 PM »
Sounds like a plan Billy !  :thumb:

Sintech, I'm assuming you used a LM317 for the +48V. I don't think the +44V will give condensors any problems, but if you want to tweak to get exactly +48V, you can change the "Radj" resistor. IIRC, lowering the value with increase the ouput (but don't quote me). Take a look at the datasheet for the LM317 and I think it'll be clear. Simple resistor tolerance can explain why you got +44V instead of +48V.

And I'll put something together to show what I did to the Bauman PSU.
Greg Stein
New Orleans, LA

Kev

Hotrod Build Thread
« Reply #11 on: May 01, 2006, 04:25:28 PM »
Quote from: "Greg"
Regarding the 2N3055, I went to my local hardware store and bought some nylon standoffs and mounted the 2N3055 a 1/4" or so off the PCB so it would clear R6 with no problem.

 :?
... and you used a jumper wire to the T03 case ?

brass stand-offs would give clearance and the electrical connection.
or am I totally off base here ...
 :cool:
 :wink:
off base .... base .... get it ?
Kev
DIY Factory

matta

Hotrod Build Thread
« Reply #12 on: May 01, 2006, 04:47:51 PM »
Quote
brass stand-offs would give clearance and the electrical connection.
or am I totally off base here ...
Cool
Wink
off base .... base .... get it ?


Hah hah!!!

Kev, that is SUCH a tech joke, any more to emit  :green:

Cheers

Matt
Matt Allison
www.matt-allison.com

Quote
We are not going to start thinking of ways to get an octopus to commit a crime, cause that just has failure written all over it – Earl J Hickey

kato

Hotrod Build Thread
« Reply #13 on: May 01, 2006, 05:17:01 PM »
Quote from: "matta"
Quote
brass stand-offs would give clearance and the electrical connection.
or am I totally off base here ...
Cool
Wink
off base .... base .... get it ?


Hah hah!!!

Kev, that is SUCH a tech joke, any more to emit  :green:


We'll all be standing by to collect them if he does.

My hotrod boards arrived today (tuesday afternoon.) Super fast!

I ordered them without knowing anything about them!! :)
I've been ignoring all neve related threads while I work on API and UA clones. But I couldn't resist, with Fabio making the 283 boards again and  potential carnhill group buy a-brewing, I figured I better buy them now even if I don't build till next year.

Anyway, here's a moronic question.
Do these perform approximately the same function as glide-on-fade's awesome switch? (gain staging?)   Kato (who should start reading up on the neve threads before posting these questions.)
-----
edit
-----
whoops, I mean MONDAY afternoon.
it's only monday?? long week so far.

Kev

Hotrod Build Thread
« Reply #14 on: May 01, 2006, 05:54:50 PM »
Dave does have a couple of notes worth a read,
Joe has circuits and wiring notes also worth a read ... see the JLMSwitch kit

there is more than a couple of ways to shave a cat ....

skin a cat ... shave a cat ... Dave knows how ...   :wink:  


ooooh !
I'm on a roll !!!
 :green:
Kev
DIY Factory

Gus

Hotrod Build Thread
« Reply #15 on: May 01, 2006, 06:01:28 PM »
Now why did you use a 2n3055?   There was a post here in the past from someone that makes stuff for a living.  They gave a transistor number to use.

matta

Hotrod Build Thread
« Reply #16 on: May 01, 2006, 06:20:52 PM »
Quote
Now why did you use a 2n3055? There was a post here in the past from someone that makes stuff for a living. They gave a transistor number to use.


Um... because I can  :green:

But seriously since these cards are the original format cards and the 2N3055 was what Neve originally used I went with that in the TO3 package, which fits the board footprint.

Matt
Matt Allison
www.matt-allison.com

Quote
We are not going to start thinking of ways to get an octopus to commit a crime, cause that just has failure written all over it – Earl J Hickey

Milkmansound

Hotrod Build Thread
« Reply #17 on: May 03, 2006, 09:43:03 AM »
I am jumping in on this project as well. I found some original B283 cards on craigslist - always a gamble, but the guy has worked on some legitimate albums so I am going with him.

I am using the JLM go between, DI, PSU,  and also his input and output iron.

His stuff is priced really well and I know he will be there to help me out of I run into trouble.

The hotrod boards make ths B283 into a really simple affordable preamp project. I think I am looking at about $250 per channel all said and done. Not even the seventh circle kits are that low - powered up and in a rack.

anyway, more to come when I get started in a few weeks.

clintrubber

Hotrod Build Thread
« Reply #18 on: May 04, 2006, 10:46:48 AM »
Looking around for the connectors for these boards. With the two 12-pin Molex connectors I found the spacing between the two doesn't seem to be wide enough (between connector #1 & #2).
I'll have a further look for another way of connecting.

Greg

Hotrod Build Thread
« Reply #19 on: May 04, 2006, 11:28:20 AM »
I think I see what you're saying... just to be sure, are you saying the 12-pin connectors (one for BA283 and one for the switch) are hitting one another. Which part number are you using?
Greg Stein
New Orleans, LA


 

Related Topics

  Subject / Started by Replies Last post
3 Replies
1449 Views
Last post May 23, 2006, 11:54:25 PM
by guavatone
49 Replies
20228 Views
Last post July 08, 2008, 06:39:56 PM
by profetik
4 Replies
2451 Views
Last post May 30, 2009, 01:43:38 AM
by iomegaman
3 Replies
1969 Views
Last post March 27, 2011, 12:32:21 PM
by Biasrocks