Hotrod Build Thread

[guavatone]

I am just trying to label a FP and I'm like to gave close to Real World values.

the minus throws me off since I can't recall the overall gain amount. IIRC I think it was 75 dB with a 1:2 XFMR

Am I correct that the numbers are subtracted from the max gain possible?

 

[safe as milk]

hi
i'm sure that 65dB is the max gain
and 10dB is the minimum.
when using the 10468/ba283/hotrod board.

the minus indicates the actual gain amount,
it's the gain required to get the signal up to 0.

i'm sure greg can/will explain it clearer i can.

 

[guavatone]

I have no chem in front of me, but is correct setup to have 2 grounds? It just seems to go against anything I've learned.

If so, my plan would be to hook up star to Chassis star point and Audio GND to my JLM PSU 0V.... sound right?

 

[dissonantstring]

hi charlie,
did you see the JLM site pic that says "all audio 0V should star from this 0v (next to the +48V pad) and do not connect to case ground"
so sounds like your plan is best in this situation using the JLM PSU.
kind regards,
grant

 

[guavatone]

I had to start a thred on this. I looked it over and I think that only one should be connected unless there is a need for chassis ground which is only necessaery on the XFMRs....

http://www.groupdiy.com/index.php?topic=276092#276092

 

[bluezplaya]

I am planning on buying some terminals for the wiring. Does anyone know the spacing of these holes? They look really small. I do know that typical spacing for PCB terminal is between 5 and 5.08mm. These look like 2.54mm. Can anyone confirm that?

Thanks,
Adam

 

[guavatone]

yeah,they are the smallet .1" molex

 

[bluezplaya]

Thank you! Do you have a Mouser P/N by chance? If not, don't worry.

Adam

 

[guavatone]

3P header
22-23-2031

2P
22-23-2021

terminals
08-50-0114


I think the others are 10P and you need housings as well for each

or just go here
http://www.mouser.com/catalog/630/1186.pdf
and here
http://www.mouser.com/catalog/630/1187.pdf

 

[Greg]

hi Adam,
I got your message. Charlie is right, they are Molex 0.1" spacing. If you look at my parts list I think I might have Digikey part numbers. You can use the Molex number at Mouser and it should reference.

 

[clintrubber]

[quote author="safe as milk"]hi
yeah they are the gain amounts.
i believe they're labelled, how much gain to get up to 0.
from -10dB (min gain)
to -65dB (max gain)

seems strange at first,
but then sensible once your used to it[/quote]

Sensitivity.

Cheers,

Peter

 

[bluezplaya]

I am wiring up my 283's and Hot Rod boards and would like to know how to wire the output transformers. I am using the JLM's and I want to get as close to the original sound as the Neve stuff.

 

[Greg]

I am not familiar with the JLM transformer. I will try to help if you can provide a link or some specs on the transformer.

 

[Greg]

I just took a quick look at the JLM site...
http://www.jlmaudio.com/JLM111DC_Output_Transformer.htm

Bottom left... 1:1.

 

[bluezplaya]

Wire the JLM111DC as 1:2

Actually, Greg, I found this post by Joe a few pages back! I wasn't looking hard enough . However, I need to confirm the hookup of the transformers. On the Hot Rod board I am sending (Out. XFMR Pri 1 and Pri 2) to (+1 and -1) on the JLM trannies. Is this correct?

 

[imo]

Curious to know different grounding schemes using the hotrod boards. I see from Greg's build that it appears to be stargrounded but i recall some people saying that the audio ground should be kept seperate?
My build works on initial powerup and then the signal drops away within a minute or so. YOu can hear it, but it is faint and distorted, intuitively it seems like a ground issue, but i was wondering if anyone else had run into this?
Best
Ian
Also was there ever a definitive pinout for the maranair group buy transformers? There seemed to be a lot of confusion about whether the windings were reversed or not

 

[Greg]

bluezplaya:
You are correct in both respects...
1:2 and Pri 1 to +1 and Pri 2 to -1...
Also double check to see if polarity is reserved from input to output. I do this on every piece of gear I build.

imo:
I can only comment on my ground scheme. It worked well and is quiet. Not sure about the polarity of the Maranair. If flipped, a simple swapping of the primaries would do the job.

 

[bluezplaya]

Greg, thanks for the tip. I am about to start wiring this switch. The switch on your BOM was obsolete on the Mouser website, however there was a ROHS available so I got that one. I don't know about your switch, but this one has no markings nor does it have any stops. I'm assuming I can wire to any tab as long as it is consecutive in sequence (1A, 2A, 3A, etc.)?

Or do you have a suggestion on this and on the stops?

Thanks,
Adam

 

[Greg]

Since it has no enstop, I don't think it will be critical... but check the datasheet (the parts supplier will have a link on their website). But there should be some type of indication of the first position on the switch.

 

[bluezplaya]

Yes, I found the data sheet on the switches and both channels are wired up. :grin: All that's left to do to this monster is wire the input transformers to the boards. I am using 31267's as 10468's but I need to know if i should pull the existing caps and resistors off the trannies. These are pulls from a Neve console and a cap and resistor remain between pins 7 and 10. :?