Hotrod Build Thread

[capnspoony]

Hi all

I'm just completing my hotrod build and I had a question about the wiring of the group buy carnhill transformers. On the JLM audio site there is a 180pf cap on the input transformer and then a 1k5 1W resistor and a .01cap on the output transformer. Are these parts included on Greg's PCB? I see the 180pf cap and the 1k5 resistor but NOT the .01cap. Does anyone have a wiring diagram/pinout that I could follow for wiring these transformers to Greg's hotrod PCB?

thanks!

best
Richie

 

[nielsk]

If the bias tim is set wrong the 47 ohm resistor will burn up. To adjust, center the pot, put a 1K tone into the preamp and scope the output to the tranny. Bring up the gain to the point of the top and /or bottom of the waveform begin to clip, and adjust for equal clipping on the top & bottom of the waveform.

 

[dissonantstring]

hi richie,
you still need the output transformer loading network (1K5 resistor & .01uF cap) on the output transformer. the 1K5 resistor on the hotrod board is part of the hotrod circuit, not the output transformer loading. note: the 180pF cap is on the input load.
-grant

 

[kato]

[quote author="nielsk"]If the bias tim is set wrong the 47 ohm resistor will burn up. To adjust, center the pot, put a 1K tone into the preamp and scope the output to the tranny. Bring up the gain to the point of the top and /or bottom of the waveform begin to clip, and adjust for equal clipping on the top & bottom of the waveform.[/quote]

Or continue to replace the burned out 47Ω daily.
Turn the trimpot 1/4 turn each time until the resistor stops burning up.

(just kidding.) :grin:

On another subject: my grayhill switch doesn't have endstops.
It just keeps going around and around and around - is this normal?
I can't find info on the grayhill web site xplaining how to make the rotation stop.

 

[dissonantstring]

hi kato,
not sure which grayhill model you have, but most should have the holes for the stop pins under the mounting nut and the facia of the body. look for a circle of small holes around the shaft. you can put a 1W resistor leg if it fits into the hole corresponding to the end-stop position and put some tape over the hole to prevent the pin (resistor leg) from falling out. grayhill usually provides a small pin and a small gold sticker/seal for this purpose (on the adjustable end-stop models).
hope this helps.
-grant

 

[kato]

Hey thanks Grant!! I'll give it a try.

 

[profetik]

Hi, I write you from Italy and I am interested to buy the PCB for the clone of a NEVE 1272 preamps. Is it possible? Which the costs are?
Can you answer me to the following address email?
[email protected]

Thanks

 

[Whoops]

Hi,
I have 2 BA283 boards that I'm stuffing and I would like to use them to build a Mic Pre.

Are there any Hot rod boards still available?

thanks

 

[Whoops]

Hello
I know this is a really old thread, but Im building this project at the moment.

Is there any chance someone still has the "Hookup Instructions/BOM" and
"Parts List that may be useful for additional information" ?

unfortunately Greg's the links at the first post are long gone

thank you so much

 

[Greg]

It's been a long time, but I think this is it.

 

[Whoops]

It's been a long time, but I think this is it.

Thanks Greg,
that is a big help.

Now I just need to know how to implement the output transformer, I don't have the LO1166, instead I have the
LO2567 ungapped transformer and the  T1310 inductor, I just don't know how to connect them to the BA283,
anyone knows how to do this?

Thanks