diyAudio - Blog Entries
Go Back   Home > Forums > Blogs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Old

Audio op amp comparison NE5534A vs. OPA134

Posted 10th February 2012 at 10:49 PM by rjm (RJM Audio Blog)
Updated 11th February 2012 at 02:48 AM by rjm

Finally got around to some more comparison listening with the Sapphire headphone amplifier. To recap: the circuit has an open loop diamond buffer output, so the op amp is just providing voltage gain. It configured for a non-inverting gain of 21 dB to match my 300 ohm HD600 headphones. Pretty much textbook operating conditions.

The op amp inputs are impedance balanced at about 1 kohm. This is about the crossover point where you start thinking about using FET input stages, but BJTs should still be fine.

I'm interested to see if there is a definite signature to a FET-input opamp. The original build called for an OPA134, which is a JFET input circuit. I tried the OPA27, which is a low-noise, high-input-current BJT design, and last night I tried the NE5534A, a classic general purpose audio opamp with bipolar inputs.

I've long been in agreement with Douglas Self on the NE5532/NE5534 : anyone who reports these op amps sound bad is either not using...
rjm's Avatar
rjm
diyAudio Member
Posted in The Lab
Views 7424 Comments 1 rjm is offline
Old

RJM Z-reg + Pass B1

Posted 3rd February 2012 at 11:53 PM by rjm (RJM Audio Blog)
Updated 4th February 2012 at 12:01 AM by rjm

I was asked to suggest a voltage regulator for the First Watt (Pass DIY) B1 buffer. One thing led to another and the next thing I'd sketched up a circuit board for the buffer as well as the regulator.

It's like a B-board, but with the JFET buffer instead of the diamond buffer, and with a single supply and, hence, the coupling caps front and back. Since it's using JFETs for the buffer I used a JFET for the pass device in the regulator, too.

Full credit to Nelson Pass for his design.

Eagle files do not show 2SK170 because the package is not in Eagle. All transistors 2SK170 or equivalent. Zener is 18-22V DO35 or DO41 i.e. Vishay BZX85. V++ is 5-15 V above whatever you select the Zener reference to be.
Attached Thumbnails
Click image for larger version

Name:	b1-10c-brd.png
Views:	3592
Size:	19.7 KB
ID:	586   Click image for larger version

Name:	b1-10c-sch.png
Views:	4981
Size:	21.0 KB
ID:	587  
Attached Files
File Type: zip Pass B1 RJM 10c.zip (61.8 KB, 468 views)
rjm's Avatar
rjm
diyAudio Member
Views 3839 Comments 4 rjm is offline
Old

The Z-reg

Posted 1st February 2012 at 10:58 PM by rjm (RJM Audio Blog)
Updated 2nd April 2012 at 02:02 AM by rjm

This is a followup of sorts to the X-reg, though there is nothing original about the circuit this time around.

It's just a Zener voltage regulator with a series pass transistor. I lifted this particular configuration from the Pionner C-21 preamplifier and re-tuned it for op amp applications. My main interest here is trying to make a small and convenient board layout.

I've used this circuit block already in the Sapphire amp and come away impressed.

The output is about 1 V less than the Zener voltage, and the input voltage should be about 3-6 V above the Zener reference voltage. I'm working here with 17 V unregulated supply and 12 V Zeners, but the values can be reconfigured easily enough for any output from 4-24 V

This is a low current circuit. If you are just powering a few op amps, no heatsinks are needed. Above 25 mA small heatsinks are a good idea. The circuit is not designed for output currents above 100 mA.
Attached Thumbnails
Click image for larger version

Name:	zreg10d-brd.png
Views:	1614
Size:	17.4 KB
ID:	583   Click image for larger version

Name:	zreg10d-sch.png
Views:	1203
Size:	20.2 KB
ID:	584  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 955 Comments 0 rjm is offline
Old

Current Feedback Amplifier

Posted 31st January 2012 at 05:15 AM by rjm (RJM Audio Blog)
Updated 31st January 2012 at 05:22 AM by rjm

Found this today: DC Coupled Amplifiers for Audio from an 11 year old web page by one Knut Harald Nygaard.

I've taken some minor liberties with the circuit, shown in the second, color image below. Replaced the current sources with resistors and moved the output buffer out of the feedback loop.

Note the resultant double symmetry of the dual-diamond buffer topology, highlighted in blue.
Attached Thumbnails
Click image for larger version

Name:	dcff15 original.png
Views:	3601
Size:	7.6 KB
ID:	581   Click image for larger version

Name:	dcff15 rm mod color.png
Views:	3804
Size:	14.6 KB
ID:	582  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Posted in The Lab
Views 3415 Comments 2 rjm is offline
Old

Protoamp project.

Posted 29th January 2012 at 07:52 PM by DigitalJunkie

So,I've been pondering this for a while,and I'm going to finally build it.

Basic idea- Fairly simple Push-Pull amplifier,that will deliver ~50Wpc,Using common/available tubes.
I decided to go with the 'usual' octals,since they are all a similar basing/pinout(7ac?).
This leaves us open to use 6L6,EL34,6550,KTxx,etc. for output tubes.
We'll have to have a -Vg1 supply with a wide voltage range to cover the needs of all those tubes,shouldn't be a problem.

The power transformer is a big 1kva/500W beast,used in the Tektronix 545A. (P/N 120-120)
Pete Millett was kind enough to post some data on this transformer,and a few others here:
Tek power transformers

The output transformers are rated ~100W,they came from a pair of old RCA MI-12188A amps.
They are ~3.5-4.0K (p-p) primary impedance.
There is some information on these amplifiers/transformers here:
The Shrine of the Ancient and Most Excellent RCA MI-12188A Power Amplifier...
diyAudio Member
Posted in Uncategorized
Views 1393 Comments 5 DigitalJunkie is offline
Old

F5

Posted 28th January 2012 at 05:39 PM by alexcp (My DIY projects)
Updated 11th April 2016 at 08:27 PM by alexcp (Added photos)

Just finished fine tuning my First Watt F5 clone.

I built it about a year ago out of parts that I had on hand back then, including a power supply reused from another project. The resulting sound was rather disappointing. Now I spent time matching transistors and tuning the feedback network. The amplifier now is very close to the performance described in the original service manual.

I am listening to F5 (the music is Tchaikovsky performed by Wiener Philharmoniker and von Karajan) and realizing that it is so good that if this was my first amplifier, I might not be interested in building anything else.

Update: after a year, this is still the best amplifier.

Update: I purchased the official F5 PCBs from the diyAudio store. I will rebuild the amplifier, hopefully with better FETs and other parts.
Attached Thumbnails
Click image for larger version

Name:	diyaudio58.jpg
Views:	424
Size:	210.6 KB
ID:	1024   Click image for larger version

Name:	diyaudio59.jpg
Views:	343
Size:	234.1 KB
ID:	1025   Click image for larger version

Name:	diyaudio60.jpg
Views:	244
Size:	181.3 KB
ID:	1026   Click image for larger version

Name:	diyaudio61.jpg
Views:	370
Size:	232.9 KB
ID:	1027   Click image for larger version

Name:	diyaudio62.jpg
Views:	347
Size:	235.3 KB
ID:	1028  

Click image for larger version

Name:	diyaudio63.jpg
Views:	422
Size:	164.4 KB
ID:	1029   Click image for larger version

Name:	diyaudio64.jpg
Views:	363
Size:	191.1 KB
ID:	1030   Click image for larger version

Name:	diyaudio65.jpg
Views:	374
Size:	180.0 KB
ID:	1031   Click image for larger version

Name:	diyaudio66.jpg
Views:	429
Size:	212.1 KB
ID:	1032   Click image for larger version

Name:	diyaudio67.jpg
Views:	275
Size:	241.6 KB
ID:	1033  

Attached Files
alexcp's Avatar
diyAudio Member
Views 1491 Comments 0 alexcp is offline
Old

NOS TDA1541A double crown

Posted 27th January 2012 at 04:54 PM by dvb projekt

I am a lucky man!

Iīve got two NOS TDA1541A double crown DACīs from a friend



Click the image to open in full size.

He bought the last from Philips a long time ago...


Just now i swapped them on my Red Baron modules...

Click the image to open in full size.

What could i say.... They will never leaving the DAC modules again !!!




dvb projekt's Avatar
diyAudio Member
Views 3207 Comments 5 dvb projekt is offline
Old
Rating: 2 votes, 4.50 average.

First Watt F5 Amp build

Posted 27th January 2012 at 01:53 PM by dvb projekt
Updated 13th November 2015 at 09:32 AM by dvb projekt (New photo source)

After reading so much over this amp, i will start a new project for my Hornspeaker

Letīs see if the F5 can play in the same league as my 300B monoīs



The parts


Click the image to open in full size.

Schaffner FN 2070 - 3A multistage EMI Filter


Click the image to open in full size.

Antek AS-4218 - 400VA transformer



Click the image to open in full size.

SST03 Softstart module from Sjostrom Audio
Design without extra transformer


Click the image to open in full size.

RFB03 rectifier bridge from Sjostrom Audio

Click the image to open in full size.

with IXYS DPG 60 C 200 HB
...
Attached Files
File Type: zip Front- & Backpanel .fpd files.zip (4.2 KB, 140 views)
dvb projekt's Avatar
diyAudio Member
Views 13132 Comments 15 dvb projekt is offline
Old

Whither Next for RJM Audio?

Posted 26th January 2012 at 12:22 AM by rjm (RJM Audio Blog)
Updated 1st February 2012 at 08:20 AM by rjm

On the occasion of selling the 100th and last VSPS Stereo Kit, it's time to consider what direction(s) RJM Audio will take over the next little while.

A. A minor revision of the stereo VSPS board is planned. Just a point release to address feedback I received over the last couple of years. Point release on current boards (Phonoclone 3, VSPS 300, Sapphire) expected when I deplete existing stock and have to re-order.

B. Since my circuit designs are essentially modular (the voltage regulation of the Sapphire headphone amp could be used with the Phonoclone, the output stage of the Sapphire could be detached and used on the output buffer on the VSPS...) I'm going to work on bringing that vision to a concrete reality by developing "swap-in swap-out" circuit boards... like those toys where you can change out the head, body and legs of a character to make many variations.
  1. X-reg board
  2. Zener reg board
  3. basic op amp gain block board
  4. VSPS and
...
rjm's Avatar
rjm
diyAudio Member
Posted in Uncategorized
Views 1505 Comments 4 rjm is offline
Old

My system (Jan 2012)

Posted 23rd January 2012 at 12:12 PM by rjm (RJM Audio Blog)
Updated 26th January 2012 at 02:57 AM by rjm

Biggest changeover in many years.

Denon DP-2000, DA-307, DL-103 turntable/tonearm/cartridge
Phonoclone 3 with 160 VA Plitron power supply
47 Labs "Treasure" model 0247 preamplifier
47 Labs "Treasure" model 0347 amplifier
Onkyo D-605SR speakers
Cables by oyaide, mostly.
(photo: Pentax K10D, Pentax FA 31mm F1.8 AL Limited)
Attached Thumbnails
Click image for larger version

Name:	IMGP1552j 1280.jpg
Views:	1517
Size:	369.4 KB
ID:	580  
Attached Files
rjm's Avatar
rjm
diyAudio Member
Views 1429 Comments 0 rjm is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 02:50 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright Đ1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki