OK, I'll say it again. The step gain attenuator switches are now available. They work in both Tube and JFET pre amps. They are a bit expensive but are truly fantastic. I have them built and installed and love them! Contact Scott - he has nothing else to do....

This ad paid for by the committee to elect Scott Hampton as DIY Pre amp Kit pin up model of the year.

What are the advantages of the step-gain attenuator kit? Is it sonicly better or is it more for a reference and documentation?

Thanks.

-Cory

So you can drive the input as hard as you want (for harmonic distortion control) and then control the actual output gain with output attenuator..... i believe

The step gain attenuator replaces the wee potentiometer that came with the kit. It is a terrific help if you want to duplicate a previous gain setting or if you record stereo and want both channels at precisely matched gain levels.

I am working on a Rev B kit. On the PSU board I got a little too much solder on resistors R51 and R52. It is just on one end of each, where the two resistors meet. They are so close that the solder ran between the two connections joining them together. I think that it is okay because they run together through the board, but I wanted to make sure before testing the PSU. Hamptone is closed for the holidays and I wanted to get this done. Can someone here please give me an answer?

quote:

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Originally posted by Armentras:
I am working on a Rev B kit. On the PSU board I got a little too much solder on resistors R51 and R52. It is just on one end of each, where the two resistors meet. They are so close that the solder ran between the two connections joining them together. I think that it is okay because they run together through the board, but I wanted to make sure before testing the PSU. Hamptone is closed for the holidays and I wanted to get this done. Can someone here please give me an answer?

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According to the trace diagram I have here, (you might double check the one you got with the kit) the trace goes directly from the one end of R51 to R52 and then on to other places. If that is the case, then a little solder between the resistors won't hurt. On that one end of course.

Good luck


Jason A.

Thanks for the reassurance. Now I can finish this up in time for my upcoming project.

I've run into a problem with my PSU. I ramped it up and checked the DC voltage. The 48VDC and 25.5VDC outputs as well as the measurements across D51 and D38 are fine. The problem is that my AC voltage is reading .186 vAC on the red wire and .765vAC on the yellow wire. My instructions tell me it should be less than 5 mV AC. So I went on to test all the points labeled on the schematic. All were fine except V1 which read 73V DC and V7 which read 36.6 V DC.

I have read that multimeter are very prone to error when testing below 100 mV AC. This could be part of my problem if so, how do I get a straight answer from my meter on the AC?

I just got my HVTP2 in the mail and I'm about to get into it. I'm going to pick up some supplies today.

Isopropyl Alcohol
Solder Wick
some kind of board holder (3rd hand type of thing)
and.. Lead free solder.

I'm pretty into the lead free solder for health reasons, but i've never used it. i plan on getting it from radio shack, similar to the one Scott mentions he uses. any pro's and cons?

also, any other little items to look at buying to prepare for this?
Thanks!

Hmmm ... solder wick is quite an acquired taste, and there's an art to its use. I'd recommend a spring-loaded solder sucker, also probably available at Radio Shack. They're not expensive, and worth every penny. Trust me, you'll thank me later ...

mud

I do like the solder wick, i always passed over the solder sucker and went for the solder wick at school and work. What i've never had experience with is lead-free solder.. is this a PITA. Is it harder to work with?

Thanks everyone.

I like using both the sucker & the wick!

I use the sucker to get large bits of solder out from around bigger component legs, & then clean up the PCB with wick. I just use wick for smaller parts.

Regards
Peter

Hey guys,

Got a moronic question for you here... Did anyone have any trouble getting the Neutrik lock screws to close? I've been pressing the faceplace and connector together and for the life of me I CANNOT turn the screws. Any hints?

Thanks!

Hi, I need some serious help. I got the HJFP2, put it together, tested the power supply, etc. Everything seemed to go together smooth. It's when I integrated the power with the audio I ran into problems. As it stands only channel 1's DI works. I double checked all point to point contacts, looked for any solder bridges, cap polarity, looked for burnt resistors and I can't see any problems. The things I know I did wrong was I got in a hurry and shorted the phantom power switch in ch 1, I replaced it, should I replace other components as well? And when I first powered it up ch 2 hummed (like a ground loop, I cleaned the pcb and now no sound is made at all). I'm assuming I've damaged some things but I have no idea what or how to check. Any help would save my sanity. Thanks.

Hi Bhubba

I dont think that shorting the Ch 1 Phantom would affect Ch 2.

Off the top of my head, it could be a solder joint that was bad & hummed initially, but is now completely open cct. Try re-soldering all the joints, making sure the solder flows nicely, but not too much heat.

Regards
Peter

Hi Everybody. New to this forum. I'm testing the PSU for 25.5 volts, b50 in b30 out at this point and I'm getting a high reading of about 32 volts. It doesn't seem to locking in at 25.5 but climbing real slow after getting up around 30. No smoke or any visual indication that something is wrong. I'm using a variac and turning it up to 110 V. If I turn it down to about 100 it seems to get around the 25.5 mark. I checked the output of my variac with a meter and it's correct. I also plugged straight into the wall and got the same thing. Anybody else have this problem? Thanks in advance. I've been lurking around in this forum for help with this kit and y'all have helped a lot already.

BP

Is there any load on the supply? Unloaded transformers will typically read 10-20% than a loaded transformer.

The pre draws 40mA for each section, ie 80mA in total. For a resistor to draw 80mA from 25v it should be 25/.08 = 312 ohms. Power for the resistor is 25 x .08 = 2W.

So put a 330ohm 2watt resistor across the supply & then check the voltage.

Peter

Thanks Peter, I don't have a load on. Although you probably think I do now! I reread the directions and am going to give it another go right now. Thanks again for your help. I can't wait to hear this thing!

Bob

Hello All ! I have a couple of questions in regard to the HJFP2 mic pre. Has anyone added the capability of insert jacks to the pre ? Say you wanted to add an outboard compressor to the pre while tracking, some type of insert jack would make this easy to do. My second question has to do with balanced to unbalanced wiring. I would like to come out of the pre and go directly to tape. In my situation the inputs of my multitrack are unbalanced. Should I plan on some type of level matching interface or perhaps this is addressed in the kit building instructions as a possible option ? Thanks in advance for any suggestions. Regards, Dave

Hi Dave

quote:

Has anyone added the capability of insert jacks to the pre ?

Seems superfluous. Patch the pre amp output into the compressor into the recorder.....

quote:

I would like to come out of the pre and go directly to tape.

The way to go balanced to unbalanced would be to wire the preamp hot to multitrack hot, preamp cold to multitrack ground & float the preamp ground. If the level is too hot, just turn the gain down. This way, one avoids an extra stage, thereby keeping the signal path cleaner.

Regards
Peter