DIY Preamp planning

bsabel

bsabel

Well-Known Member
As I put the finishing touches on my amp, I can't help but think ahead to my next project. I can be pretty flexible in my design but I'm going to try to have it all to start with and whittle it down from there.

So here's what I'm thinking: I would like to try and get a power supply, preamp, phono stage, sub-sonic filter, and headphone amp in the same box running off the same power supply. My first thought is that I could do an all ESP build. I like the tone controls of the P97 preamp and I've read good reviews of the P06 phono stage. And I know his P05 power supply takes the guess work out of powering these amps.

Will incorporating a P113 Hi-Fi Stereo Headphone Amp and a P99 Subsonic Filter demand too much from the power supply and/or cause other problems?
 
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G'day mate, they sound like excellent choices. In fact I have built many of those projects with excellent results, and the P06 is in my opinion a superb phono stage.

I have already built one P99 following one of my P06's and it works superbly. The additional current drain is not a problem. Good luck mate! Regards, Felix aka catman.
 
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I knew I could count on you to chime in, Felix! Thanks for the input.

I suspect the P99 draws a negligible amount of current. And ESP has multiple drawings of the P05 powering the P06 and the P88 preamp. I doubt the P97 is radically different from the P88 from a power standpoint. My only concern, really, is adding the headphone amp. I'd like to have it in the same box if it fits but could leave it out if it would compromise the phono or pre.
 
G'day mate, yes the headphone amp might draw a bit of current but small heatsinks on the regulators (as I've done) might be useful to cope with increased current demand.

Why not email Rod Elliott and ask his opinion. Regards, Felix aka catman.
 
fellow IC-er, i just assembled the PassDIY B-1 preamp board (the Salas-designed DC shunt-regulated hotrod version), and i'm in the process of having the chassis built for me. should be done before too long, i think. ultimately, it's probably going to cost more than the ESP options, but i suspect it will perform better. also, it has plenty of leftover juice to run some other boards (like an active crossover or subsonic filter) -- not sure about a headphone amp, though...

just another option to consider :)
 
Hello fellow IC-er. PM sent, I think we've met!

I am very much open to other designs for my build. The ESPs are attractive not so much for their price, but that I know they are compatible and have a good track record.

I've heard about the B-1 preamp but don't know much about it. I could be swayed!
 
ESP projects take a little more thought.But Rods building instructions make construction pretty easy.


2- DIY ESP MOSFET Amps
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Okay, here is what I've got. This is how I am envisioning a preamp with ESP boards:
Preamp-Schematic.gif

I'm not sure I entirely understand the grounding situation on this rig. But I'm confident that Rod's instructions will illuminate things quite well.

A couple design notes: Everything should be very close to scale. I took the measurements from Rod's website and built those in. The case size was chosen to match the footprint of my amp. I flipped Rod's suggested layout so the power wires didn't cross any of the signal wires until after it went through the preamp.

I decided to forgo the headphone amp in this build. It was just proving to be too difficult to incorporate. The big thing was that I don't think I could effectively get any volume control without adding another pot. So I may end up just making a different box for it.

Anyway, the lines are open to your suggestions. Please let me know if you see anything that could use a change. Thanks for your help!
 
Are you going to have a transformer in a separate case or is that just not depicted?

That headphone deal sounds like a major complication to this build (if using one of Rod's better offerings). I'm sure someone here has a more elegant way to get it done, I have no experience with headphone amps.
 
You're layout looks fine and workable.

Personally I don't like tone controls.
I think they muddy up the sound.

I've done mine with just selector and volume controls and like the sound of them.

For the power supply you'll be using a wall- wart I presume.

Suggest getting one with the highest VA rating you can find.

10va is excellent. Spec wise it's probably overkill but from experience with similar circuits it makes a world of difference in impact soundwise.

You are definitely heading in the right direction.

Good job so far.
 
if you get PCB-mounted pots for the front board, then you could conceivably push that board back toward the rear as far as possible and get extension shafts for each pot. it would dramatically reduce the amount of hookup wire you'd need, at least by a factor of 2.
 
Thinking about this, again.

The P05 has facility for an AC muting circuit but this means you need a transformer with dual secondaies. Not a big deal, it's probably easier to source than a stand-alone, single rail 16v. AC supply. Also, you can size the transformer to your needs. Additionally, it could be mounted in the same case. You could mount the transformer and PS board toward the back and enclose them with a shield. The RIAA equalizer and phono board would be shifted towards the front of the case.
The output wiring would shift towards the side, swapped for a central IEC fused Power inlet module. I would have the input wiring on the opposite side, as depicted, but forgo the extension shaft and place the rotary switch on the front. My thinking on the last is that the price of the shaft extension and compatible rotary switch would be better spent on a better rotary switch and, with proper cabling, the switch location for input wire doesn't make any difference.

Just a few thoughts on the layout and PS but the overall aspects of the build look good. Maybe this time around, we'll be able to get the LED down to an acceptable level.:D
 
westend said:
Thinking about this, again.

The P05 has facility for an AC muting circuit but this means you need a transformer with dual secondaies. Not a big deal, it's probably easier to source than a stand-alone, single rail 16v. AC supply. Also, you can size the transformer to your needs. Additionally, it could be mounted in the same case. You could mount the transformer and PS board toward the back and enclose them with a shield. The RIAA equalizer and phono board would be shifted towards the front of the case.
The output wiring would shift towards the side, swapped for a central IEC fused Power inlet module. I would have the input wiring on the opposite side, as depicted, but forgo the extension shaft and place the rotary switch on the front. My thinking on the last is that the price of the shaft extension and compatible rotary switch would be better spent on a better rotary switch and, with proper cabling, the switch location for input wire doesn't make any difference.

Just a few thoughts on the layout and PS but the overall aspects of the build look good. Maybe this time around, we'll be able to get the LED down to an acceptable level.:D
Click to expand...

I believe the P-05 is one of the earlier revisions either P-05 or P-05A. Looks like it is a P-05A.
PM me if you need a transformer....I have a low profile 15-0-15vac 30VA it measures-(L) 68mm X (W) 56mm X (H) 35mm AVEL-LINDBERG potted toroidal. Avel P/N --OB30/15
 
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Lots to talk about here. I'll try not to miss anything!

I've gone back and forth at least three times on tone control/no tone control. The tone controls seem desirable but I get the sense that Rod doesn't even like them and just offers them to please the masses. Is there any consensus on the difference in sound quality between P97 (tone controls) and P88 (no tone controls)?

The current layout does call for a wall wart. That seemed like the easiest application and didn't seem to have many drawbacks. But that AL transformer you have does sound absolutely perfect, avionics. :scratch2:

Rod seems pretty convinced that the switch needs to be back as far as possible. I've poked around in enough receivers to know this is rarely done in practice. Any strong feelings about this out there?
 
Just some thoughts here.

Avionics idea is a good one. You'll have plenty of reserve and won't notice any sag at all even when running phono and pre-amp boards together.

Is a switch really necessary?
I don't know how hard it would be to plug and unpllug the unit in your case.
I just went directly from the fuse to PS board.

Trade off of turning on or plugging in, whichever is easier in your case.

I like the school of less is more.

JMO
 
I appreciate the less is more ideal, as well. Unfortunately, in my particular listening environment, I'm confident that not having a switch will result in bumped equipment and dropped cords! :no:
 
I use Rods po5, p97 and P113 boards all in the same metal box and it works fine.
The p97 pre amp with tone controls has no noise or coloration at all, very nice.

The p113 headphone amp is also very good. I prefer a small 10 ohm resistor at the output instead of the 120 ohm he recommends. I also lowered the gain to something like 2 down from 27 IIRC. Less noise and the dynamics are still there.

Lastly the LM317 and 337 regulators on p05 board need to be loaded to at least 100 milliamps apiece for best noise and impedance. I had to add low value resistors in the pre amp to get the loading correct. A center tapped transformer works best here. I put my toroid in another box for best hum and noise rejection.
 
signal-dude said:
I use Rods po5, p97 and P113 boards all in the same metal box and it works fine.
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Do you run the P113 with signal from the P97? I wasn't sure if it would be appropriate to run the headphone amp with the line level signal. If I can control the volume of the headphone amp with the pre, then I may put the P113 back into the design.
 
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