Hotrod Build Thread

[Milkmansound]

yeah, I saw that and I found one online as well.

just need to figure out what I want to set the gain of the card at to work best with this build. Any suggestions?

I also got my stuff from JLM today - everything looks awesome, but I screwed up and only got the PCB for the PSU, not the entire parts kit which I intended to get. Anyway, looks like I have a nice big mouser order on the horizon.

the nice thing about the JLM transformers is that they will definitely fit into a 1U case - so I can fit the 12 hotrods into one rack space! I might even just use his panel layout too - might as well right?

if anyone has the JLM PSU BOM for the US, that would save me a lot of time. I can probably dig one up on here somewhere... Other wise I will just plan on sourcing that stuff on my own, and maybe post that BOM for others to use. Provided I do not overlook yet another thing... I have always been kind of a space cadet, but this is getting ridiculous :grin:

 

[Greg]

[quote author="Milkmansound"]just need to figure out what I want to set the gain of the card at to work best with this build. Any suggestions?[/quote]
What do you mean. With the Hotrod, the "gain" switch controls the NV gain of the preamp and the "output pot" controls the AM gain. What exactly are you trying to figure out?

 

[kato]

[quote author="Milkmansound"]
if anyone has the JLM PSU BOM for the US, that would save me a lot of time. I can probably dig one up on here somewhere... Other wise I will just plan on sourcing that stuff on my own, and maybe post that BOM for others to use. Provided I do not overlook yet another thing... I have always been kind of a space cadet, but this is getting ridiculous :grin:[/quote]

There's a thread around here somewhere saying it's impossible to find caps in the US that fit the JLM PSU board. JLM uses 13mm Lelon brand caps - made in taiwan - but no US dist. Others have reported that the usual - mouser - digikey - only have those cap values in 16mm or larger.

To make matters worse, the Lelon brand have a reputation for capacitor failure - so if one of the caps fails, it will be pretty difficult to find a replacement.

Let us know if you find anything here that fits. The other thread mentions using lower voltage caps in the same footprint. That may be a viable solution.

 

[kato]

double post

 

[kato]

triple post

 

[kato]

quadruple post
(wtf? sorry.)

 

[guavatone]

[quote author="kato"]There's a thread around here somewhere saying it's impossible to find caps in the US that fit the JLM PSU board. JLM uses 13mm Lelon brand caps[/quote]

Which caps are u talking about? I had no problem with the big caps were fine, while the small elcaps were a little tight, but I think I used a higher voltage rating.

 

[Milkmansound]

oops. Nevermind - I just noticed the words "externally mounted components" on the spec sheet. For some reason I asssumed you had to open up the gain on the card, and the hotrod just padded it down. So yeah, I just need to populate the card.

not great news about the JLM PSU parts... but I can think of something, because I am only using this for 24 volts and 48V. I can probably juggle the voltage ratings around a little in order to make more room, or worse comes to worse mount the caps on perfboard or something.

 

[kato]

[quote author="guavatone"]
Which caps are u talking about? I had no problem with the big caps were fine, while the small elcaps were a little tight, but I think I used a higher voltage rating.[/quote]

I'm talking about the big 50v caps.
No problem for me; I bought the complete kit from JLM.

If you found caps that fit (in the US), the folks at this thread would like to know where you got 'em:

http://groupdiy.com/index.php?topic=15533

 

[Milkmansound]

just putting my order together - about this item:

Polyester 10nf cap

I do not see it on the board, just the 180pf ceramic cap. Is this necessary on some other part of the circuit? This is the only thing that I will not be able to find exactly at mouser where I am ordering everything else - if I do need it can I sub another type of cap in there?

 

[Greg]

The output transformer loading is offboard. I used a Sowter output transformer, so a resistor in series with a 10nF cap is needed to load the Sowter. I just put it across pins 2 and 3 on the output XLR.

 

[Milkmansound]

ok, I assume I will need something similar with the JLM output transformer - I will ask Joe I guess.

 

[Milkmansound]

I just got in my order from Mouser and Digikey all at the same time.

if it continues to rain tomorrow, I imagine I will have at least one channel of the hotrods ready to go. I have not ordered a case yet because I am not sure if I can fit it into a 1U case or not - the caps for the hoatroad boards themselves are rather large - but there is room to mount them externally if I have to.

Joe emailed me back and the JLM does not require the loading that the sowter transformers need, but he did say that they might benefit from a 680ohm load across it when feeding a 10k line input. I will try them either way.

I have not heard Joes transformers yet - but I will say that if they sound good (which I imagine they totally will based on the rest of his product line) they are really a great value and extremely straightforward to hook up.

also, I ordered 680UF nichion PW's for the JLM PSU and they fit just fine.

 

[skipwave]

[quote author="Gus"]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.[/quote]

TIP41C

I have a 2n3055 lying around. I think I'll build a perfboard 283.

Anybody using MPSA18 in place of the BC184C?

Edit: Corrected tranny number.

 

[Milkmansound]

I am just using whatever crosses with the ECG/NTE 123AP, just gotta pay attention to the leads.

 

[Milkmansound]

irrelevant... (edited)

 

[Milkmansound]

running into a few snags here...

first of all - here is a pic of how I am planning on fitting this all into the case. Seems like this enormous 1U case will fit everything the hotrods have to offer - however, the JLM output transformers do not fit! I have to either mount them outside the case or cut into the top and bottom of the case to get them in there.

its not the end of the world, cause I can use them to balance the output of my PM1000's

is there an output transformer that can easily fit into a 1U case? Greg - will the sowters fit?

also, the caps on the hotrod boards themselves will not fit into the 1U case when they are on standoffs. Not a big deal, I am going to just mount them hoizontally and extand the leads.

my advice - put this into a 2U!

here is the photo:

http://milkmansound.com/img/hotrod.jpg (full size)

 

[sintech]

Check the current Group Buy from Carnhill for LO1166 in the black market.

whats the inner hight of your rack case?

 

[Milkmansound]

I think its 1.42in

hard to tell exactly from the par metal site - but to be safe, lets assume 1.4in

I will check out that other thread - and I have an email out to Joe about this as well.

 

[sintech]

Yeah, that works out about 36mm, I think you need 39/40mm internal.

The JLM output transformers are 38mm.

I would try putting spacers/washers on the screw fixings top and bottom maybe gain 1mm both ways.. you'll never see that once racked up.