I’ve been impressed by the ESP projects by Rod Elliott, they work well, are simple for novices but with plenty of scope for modifications. The projects come with extensive documentation, including construction advice if you buy the PCBs. I decided to try his well regarded Project 88 preamplifier to go with my Nelson Pass ACA. This is designed to be simple and flexible with configurable gain using DIP switches. It requires a +/-15V supply so I built another ESP P05 PSU, this time with a conventional toroidal transformer rated at 15VA.
The boards are very small with a correspondingly compact layout. The preamp has a low parts count and I used generic 1% metal film resistors, Wima polyester capacitors Panasonic electrolytics and Vishay ceramics. The opamps are my usual choice, Burr Brown OPA2134PA, although others can be used. The volume potentiometer is an Alps RK27 10K mounted on a PCB for easier wiring.
There are two gain stages, the first is ‘hard-wired’ to be either 0dB or 6dB and the second stage is highly configurable, using a 4 pole DIP switch module for each channel. The circuit component values in standard guise are set to accommodate a linear volume potentiometer and a balance pot. The omission of the balance pot in my build just requires a resistor change, as does the use of a log pot for volume.
I found a nice enclosure which mimics the design of Pass amplifiers for a very reasonable price. I was a little apprehensive about this as I’ve read quite a few negative comments about enclosures from China, but this particular example is of very high quality. It comes with an IEC power connector and switch and the back panel has been machined to accept these. There are no cutouts for line connectors so I drilled the rear panel to accept RCA jacks. The front panel has a very nice volume knob, and again the hole for the pot shaft is pre-drilled, although it had to be widened slightly to accept the Alps pot. All PCBs and the transformer are screwed to the enclosure and a safety earth connection is made to the chassis. Anodising is removed at all contact points so that all parts of the enclosure are earthed.
I’m extremely pleased with this build. I have it installed in-between my Amp Camp Amp and the Topping D30 DAC which is fed by the Raspberry Pi IQAudio streamer. The combination of amp and preamp is superb and I think they look excellent together. This was a relatively cheap build, well under £100 for everything!
Very professional build. Most impressed. I’ve built ESPs P113 headphone amp, P101 power amp and P88 pre-amp. They all sound really good. P88 was a step up from other well known pre-amps from Audiolab and NAD.
Hi Richard,
Thanks for the kind words.
I really do like Rod’s projects. I can believe the P88 was a step up, now I’ve had it in my system for a while I really do believe the pairing with the ACA results in superb sound, even through my cheap speakers, and they are both absolutely silent (to my older ears).
Interesting you mention the headphone amp, I’m thinking of having a go at creating a layout for one as I want to attempt that side of buidling next.
Hi! Very nice build! There’s a p88 thread going on at diyaudio.com. I shared your project in the thread – I hope that’s ok with you: https://www.diyaudio.com/forums/analog-line-level/11753-rod-eliot-project-88-question-20.html
Hi,
Thanks for the kind words, I am pleased with this build.
I was aware of that thread as I’d read it before building the P88. DIYAudio is a great resource isn’t it?
I have been keeping an eye on this “clever” project for quite some time. Have you tried to put measure it with your soundcard and REW to see how it does compared to the loopback performance of the interface itself?
Hi,
No measurements yet, I’m still very much a novice with all of this stuff and I’m trying to understand how it all works and what it means. I’m very busy with work at the moment but when I have a little more time I hope to measure this and my other projects where possible (I’ve given some away). I hope to improve the measurement equipment in due course as well as I mentioned in a reply to your other comment.
Rod’s designs filter the ‘audio phools’ beliefs from reality. You must have spent 80% of your money on the case and toroid. Looks nice!
Hi, thanks very much for the compliment.
I really do like Rod’s projects and the detailed background and guidance that comes with them, and that’s before you take into consideration all of the other articles. I get quite a few emails asking me to send photos of the undersides and share his PCB layouts (I don’t and I explain why).
You may be surprised about where the main costs of this project went though. The total cost of the PCBs is quite high for me here in the UK. On top of Rod’s actual prices (which I think are very reasonable and have no problem with) there are the ridiculous shipping and customs costs. I paid £43 for 2 x P05D PSUs and 1 x P88 board including shipping. Then I had to pay £14.52 import duty which includes a customs administration fee. The enclosure was £26 including postage and the toroid was £9, about £6 cheaper than the decent 15VAC wall plug I used for the P97. I use decent quality parts (Panasonic, WIMA) for the PCBs but even then the component cost, as you imply, is largely neglible.
Regarding the ‘audio phools’, I don’t know enough to make my own judgements on the relative pros and cons of certain components, but I am trained in evaluating arguments, so I look for guidance from knowledgable practitioners, in particular those who can support their arguments with sound reasoning and measurements. I’m a beginner hobbyist so I’ll take the word of an electrical engineer over a forum member conducting sighted listening tests of different capacitors. I really have no desire to spend X10 the amount on ‘audio’ capacitors etc. If they want to do that, great, but I’d rather spend money on a nice enclosure, at least I can see where my money went.
I take it you’ve completed a few ESP designs yourself, do you have any links?
Thanks again for your comment, much appreciated.
Hi, your preamp looks really nice. I just finished soldering my own PCB and found that event with volume turned down, still can hear music (although at low level). I omitted the balance pot and used 50K log pot for volume in my build. Could you please explain required resistor change mentioned above? Regards.
Hi, thanks for the comment.
If you omit the balance pot then certain resistors need to change and similarly if using a log rather than linear pot.
If you bought the PCB from the ESP site then there is a secure area of the website which gives more information on the build, the details are in the email sent when you buy a board. There’s always more information in here than in the publicly available articles on the website. I don’t publicly post anything here that Rod Elliott keeps in his secure section as that is a benefit that he keeps for buyers only.
Hi! I’d like to build a new power supply for my p88. May I what the rating for your transformer ist? Do you have any hum or noise issues with the transformer being so close to the other parts ?
Thanks!
Michi
Hi,
I think it was a 15-0-15 30VA transformer as Rod recommends. At the moment, the P88 is hooked up to my PeeCeeBee amplifier and I’ve had no noise or hum issues with it that I can hear. I might actually get round to doing some measurements on it one day.
Cheers and good luck with your build.