Hotrod Build Thread

[matta]

Sorry Greg,

I didn't take a look at Joe's schemo just your hookup notes.

From my understanding you mean that I need to jumper, i.e connect a wire from 7A through to 12A, so connect every stop from 7A to 12A to 7A with a piece of wire?

And that is all I need to do?

Thanks

Matt

EDITED: Yip, exactly what I thought, saw the JLM schemo and it made sense, all working now

 

[Greg]

PERRRRRRRRRRRRFECTO :thumb: !!!

Whatcha think about the sound?

 

[matta]

Um,

Well I've not used REAL Neve in a while, but this brings back some memories.

It sounds lush, big and a beautifully meaty low end. This thing has HEAPS of gain for me and sounds so quiet.

I've not done much in the way of testing, just powered up, tried both channels out and passed some audio through condensers and a 57 with Vocals and Acoustic Guitar.

I'll wait till I've completed racking before any major testing. The bugger in it all is that the torrid company who winds my torrid manged to get my order wrong again and I have 2 x 15-0-15VAC torrids here instead of 25-0-25VAC.. so will have to wait a few more days till I box it up.... GRRRR.

Cheers

Matt

 

[3nity]

Hi guys, matta, greg!
i did have 238AV i did bought from Fabio, but this is not the card version is the one with pins to go on the N72, my question is could this boards work exactly as the original BA238av?????
i'm very interested in the hotrod so any info would be nice! :thumb:

 

[sintech]

Looking at this :

http://[email protected]/neve1272boards.htm

The only problem I'm seeing In the pics: The daughter card is marked 283AM and 283NV, but the heat sinked TR3 from the AM section in the original schematic seems to be located on the main board in this case.

but I'm no expert!

 

[Greg]

If you have Fabio's N72 board, then there's no need to really build the Hotrod version. But to answer your question, you can't use the board in Fabio's board as a direct swap for the BA283AV card.

 

[3nity]

well yeah, i got the N72 from fabio but your hotrod looks simpler and cheaper , N72 could wait.

 

[matta]

Well I finally got my power trafo and boxed my my 2 BA283AV boards with the Hot Rods. They sound great! Not had much time to work with them but will hopefully spend some time this weekend.

I've attached a few pics. The case was an old ART Pro VLA rack cases that I gutted. Let me say that wiring in a box this small is a nightmare, but I took up the challenge and feel I still managed to keep it clean and neat, and engineer it in a way so it all fits!

The Jewel Lamp is actually Blue to match the +48V LED's, but because of the 'yellow' lamp it comes out green...

Hope to see some others finished soon.

Cheers

Matt

 

[Milkmansound]

nice!

I am back from my vacations - need to order my other input transformers and label my panel before I call this one done. However, I am loving the way it sounds even with the wrong impedance!

I had a hard time fitting my wiring into my enormous case - you did an amazing thing there!

 

[Greg]

hi Matt:

Top notch, man !!! :thumb:

 

[Milkmansound]

I just corrected the input impedance on my hotrods on sat morning by adding extra input iron from JLM.

now we are in business!

just using a regular old SM58 I did notice a large difference. The sound was more balanced across the spectrum, and more gain. Of course, I originally did testing with another mic... so this might be a little of both - but with nicer mics the preamp kicks ass!

thanks again to everyone who made it happen

 

[HappyTom]

It would be nice to have this thread in the meta.
Do a search for hotrod and see..

HT

 

[soundeq]

question about the 12 steped pots for the gain....

I started puting togeather stuff, and it looks like all 12 steps are used. I used Greg's BOM and ordered the 2 deck 12step pots.
However, I don't want it to be a 360 of gain, I was looking for the traditional 260-280 degrees with end stops at each end....
I'm thinking I'll get a 2deck 14pos switch for this and figure out some kinda end stop thing....
Anyone else done this?
Am I missing somthing?
I just think a full circle of gain, without endstops feels unprofessionalish to me.

Cool project, and thanks for everything greg, the BOM has been great so far... I'm going with the JLM output iorn, and found some original NOS st ives mic inputs score!

 

[soundeq]

well I kinda answered my own question... seems as 14 step pots arn't easy to find... just 12 and 24's....
so perhaps lose the first step, and put some kinda stop in there? making it an 11Pos rotary?

 

[guavatone]

[quote author="JLM Audio"]Change 7 resistors on the hotrod PCB and get 6dB extra gain. The resistors in series that form the input pad setting also are the load resistor to the secondary of the transformer. So with 1:4 ratio will reflect roughly 300 input impedance. So if you wanted to reflect 600ohm you would make each value twice its value or if you wanted to reflect 1200ohm like the original neve make each value four times bigger.

300R - 600R - 1200R input impedance

2k7 - 5k6 - 10k
1k5 - 3k - 6k2
820R - 1k6 - 3k3
470R - 1k - 2k
150R - 300R - 620R
82R - 150R - 300R
110R - 220R - 430R
[/quote]

I am using the input XFMR from the recent marinair GroupBuy. from what I understand it's best to have the secondary loaded with 4.8K and ewach above column will give you the loading value when added.

Are these values just for the JLM xfmr's? I am a bit confused since I thought the hotrod is supposed to load the xfmr correctly.

 

[indigom]

ok, i'm having some problems with this one. i know that it's supposed to be like putting Lego blocks together, but none the less:

I'm using a JLM 3 rail power supply, outputting +24 and +48. Left the +48 for now.
I have JLM Go-between boards, jumpered in IDC connectors for now.
All the Carnhill transformers are wired up according to JLM and other schematics that I've found about.

Problem is, I plug my sound interface in (metric halo), and I only get reasonable gain on switch position 1. pos 2 and 3 produce less gain. all the rest are nothing.
The switch is wired A closest to the front of knob, wires starting out at the one position and going around clockwise.
The B deck has the other wires connected, but nothing on the pins which A uses.

Any help would be greatly appreciated!

then i can tell you about how i plugged in the JLM DI board and smoked the 10K 1watt resisters, but that is another story!

thanks
Jay

 

[indigom]

opps now i noticed on your hookup diagram to jumper deck a 7-12.
done.
now I get more options out of it but it doesn't seem so incremental and eventually out of control on line signals like the N72 that I built.
are the switch positions supposed to be so subtle?

thanks
Jay

 

[Greg]

Can you describe the behaivor a little more. I don't think I quite understand.

You also mention line signals... what voltage are putting into the unit under test?

 

[safe as milk]

hi
i'm just finishing off my hotrods(thanks to everyone involved):thumb:
and was wondering what noise floor others have obtained.
ref 1V i'm getting -96dB. so i think i must be doing something wrong?
when i leave the oscillator on my console connected i get -83dB

thankyou

just popped the lid on and it went down to -102dB?

 

[Greg]

Have you tried listening to it, yet. Perhaps you have a ground loop or maybe the power trafo EMF is getting into the output transformer. Post a picture. I think that might help.