Profile

Cover photo
166 followers|197,070 views
AboutPosts

Stream

RJM Audio

Shared publicly  - 
 
Szekeres headphone amp. Re-optimized 2015 version. And.. it still basically sucks.
4
1
STEFANO SUDANO's profile photo
Add a comment...

RJM Audio

Shared publicly  - 
 
Get your eighties on. I've been using this track to see how the Sapphire sound breaks in over the last few weeks. Youtube audio quality can be surprisingly good.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
The Sapphire 3 headphone amplifier power output for 0.1% harmonic distortion is 50 mW, 16-300 ohms. Above 50 ohms, it's 100 mW or more.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
I've updated the Sapphire headphone amp web page to version 3.0.
An op amp voltage amplifier with a discrete transistor diamond buffer output stage.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
I'm thinking of changing the kit resistors from Vishay CMF55 to KOA Speer MF and/or Vishay RN60. Mouser pricing is getting crazy on the CMFs, and I honestly don't think the price reflects the quality. (all are 1%, 100 ppm/C) It's probably just Mouser's inventory management: which brand they want to sell you in what quantity.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
It ain't hifi ... but it ain't bad, either: the TDK A33 wireless weatherproof speaker. http://cnet.co/1chmjLM A definite eye-opener for me in terms of the sound quality you can get these days for such low cost and convenience. The WAF (wife acceptance factor) is off the charts.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
Mercy me, this is actually a real product...
1
Add a comment...
Have them in circles
166 people
J & K Electronics's profile photo
Awesome Audio's profile photo
Ferdinand Piette's profile photo
Márton Tamás Tóth's profile photo
Денис Вершинин's profile photo
Tomohiko Suzuki's profile photo
Oxford Powershop Ltd's profile photo
Utai T.'s profile photo
Audiophile Inventory's profile photo

Communities

RJM Audio

Shared publicly  - 
 
Today's headphone amp circuit is a low voltage JLH 2005, optimized for 16 ohm loads and operation at +5 V. R11 or R3 could probably be made trimmable to fine tune the operating point. Design idea - not tested.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
Sapphire 3 as line preamp. Will drive 600 ohm loads with ease!

If you like, change the four 150 ohm resistors to 475 ohms to optimize the circuit for line duties. It's fine as is though.
2
Add a comment...

RJM Audio

Shared publicly  - 
 
10 mW as is a reasonable estimate for the maximum working output power in a headphone amp. Simulated in LTSPice, the Sapphire shows  <0.002% THD at 10 mW, from 16-300 ohms. For loads below 60 ohms the dominant distortion is created by the current swing, while above 60 ohms it is created by the voltage swing, leading to a "check mark" shape with the minimum distortion at 60 ohms.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
Sapphire3 kits are go! Price (parts, boards, & instructions) is $130 US inc. shipping.
1
Add a comment...

RJM Audio

Shared publicly  - 
 
Another Sapphire 3 (first one built after my own) is up and running. Stan's impressions here: http://bit.ly/1IXoQYp
5
Alice Li's profile photo
2 comments
 
http://grewin-tech.en.alibaba.com/productgrouplist-219239916/Toroidal_Transformer.html

Our website for various toroidal transformers type.
Any questions,welcome to contact with me freely.

skype:lialice99
Add a comment...
People
Have them in circles
166 people
J & K Electronics's profile photo
Awesome Audio's profile photo
Ferdinand Piette's profile photo
Márton Tamás Tóth's profile photo
Денис Вершинин's profile photo
Tomohiko Suzuki's profile photo
Oxford Powershop Ltd's profile photo
Utai T.'s profile photo
Audiophile Inventory's profile photo
Communities
Story
Tagline
A resource for the design and construction of high-fidelity audio equipment.
Introduction
RJM Audio is my hi-fi hobby site. I design and build audio equipment, from interconnect cables to headphone amplifiers to voltage regulators though I'm best known for my VSPS and Phonoclone phono preamplifier circuits.
Contact Information
Contact info
Email