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RIAA Equalization Curve

Posted 5th March 2013 at 01:51 AM by rjm
Updated 5th March 2013 at 02:37 AM by rjm

For reference and experimentation.

This excel worksheet will provide you with reference data that you can overlay and compare with the measured/simulated response plots of actual phono stage circuits.
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rjm
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Posted in The Lab
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Old

6C33 OTL Fine tuning - BGs, ground and wire dressing

Posted 3rd March 2013 at 02:58 PM by wlowes
Updated 8th December 2014 at 12:39 AM by wlowes (Update - Bulk foil resistors)

The amps continued to run in and proved to be keepers. Well worth doing some final spit and polish. There was a little hum on one amp and some noise / hash on the tweeters of both channels. Nothing major, but certainly audible at 1 foot.
Using AC filament supply for all but the input tube, I figured I should re read the best practices on wire dressing, hum pots, virtual center tap etc.
Looking back there were some spots to improve.
1. tight wire twist on path from bridge rectifier to first caps. Done, no real change.
2. tight twist on b+ supply to input tube plus added BG 3uF 250v cap right at the tube. No change to noise but love the improvement in sound
3. tight wire twist from psu to b+ on all power tubes plus BG 10uF 250v on each power tube. Like the input tube the BG brought an immediate lowering of noise floor that really brought a finishing to the SQ. Quiet background, micro details and just a smooth rich sound. Not colored, just the way it...
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Old

The best sounding I/V resistor

Posted 3rd March 2013 at 09:22 AM by dvb projekt
Updated 3rd March 2013 at 03:17 PM by dvb projekt

As many of you know, i am using the Texas Components TX2575 Bulk Z-Foil resistor for a long time
in important circuit positions, especially as I/V resistor.

Recently i stumbled over a short recommendation from Thorsten Loesch.


Quote:
Originally Posted by ThorstenL View Post
Hi,
I would second Rohpoint, Neohm less. Rohpoint are truely excellent. For my first TDA1541 Non-OS DAC (in 98) I handmade bifilar wound Non-inductive 25 Ohm resistors.
In susequent builds I compared to Rohpoint (which I have used extensively and found no reason to handwind resistors.

In my commercial designs we use a specfic type of SMD resistors after auditioning tons.
Some SMD resistors are really bad, some are so-so and some are most excellent, though no patch for a Rohpoint Squaristor GR102.

Ciao T

Because i know Thorsten as a man who had the perfect sound in mind,
i ordered one pair 30R to try them in my Tube-I-zator.


Click the image to open in full size.
...
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Old

Line input RF reject filter

Posted 19th February 2013 at 07:24 AM by abraxalito
Updated 26th February 2013 at 03:09 AM by abraxalito (Added zoomed passband plot)

I've only simmed this so far, no listening tests. The aim here is to have a passive filter which works into a line level impedance (i.e. 10k or greater) and which gives a decent amount of RF rejection without compromising SQ. I plan to incorporate it behind the RCA input jacks of my chipamp.

Design-wise, it started life as a simple 2nd order filter with single series L and shunt C. But when it came to wind the inductor I didn't have a wire diameter small enough to make the required value (44mH). So I split up the inductor into 2 * 22mH and then couldn't resist hanging a cap off the centre tap. The result has turned more into an over-damped elliptic with a higher corner frequency than the original, but with an impeccable phase response to 20kHz. The elliptic-type plot comes about because of the SRF of the two inductors (around 350kHz).

Since fas42 remarked on the phase performance, I've added the group delay plot for the passband. Almost pure time delay of...
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Old

FE126En Factory Reflex, a "cruel joke"

Posted 8th February 2013 at 08:14 PM by planet10

The subject of this box has come up before, after a 3rd reply to queries, this blog post,

Click the image to open in full size.

One of 2 Fostex factory recommended cabinets. 10.5 litre tuned to 61 Hz. The other is not very good either.

From the sims you can see that with this box any bass response you have will be way down which will exaggerate the FE126's forward midrange and the 7k peak.

Click the image to open in full size.

The top curve is half-space (ie what you would get if you mounted them flush in a wall or approximately what you would get with BSC added). The lower curve is with no filters and a simulated 6 dB of baffle loss. You would need a 2-stage filter to give any semblance of flat response. You would lose some 12 dB of sensitivity and then you run into the very low xMax which means that for...
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Old

The Red Baron DAC Module V4.0 - Out of production

Posted 8th February 2013 at 08:34 AM by dvb projekt
Updated 19th June 2013 at 10:26 AM by dvb projekt

The Red Baron
V4.0



Click the image to open in full size.


The evolution brings the following changes

- Separate I2S-GND route to Digital-GND
- Separate Analog Output GND route
- Separate GND route for active divider decoupling caps to Analog-GND
- Modified active divider decoupling pads for better SMD 1210 caps soldering
- Onboard SOT353 footprint for fastest DEM-Synchronizer ICs
- Un-interrupted ground plane
- MOSFET Source/Drain failure corrected


Still on the module

- Direct shunt voltage inputs with shortest onboard traces
- I2S In-/Outputs with shortest onboard traces
- I2S Attenuator and DEM Synchronizer
(by -ecdesigns-)
- Onboard Grounded-Gate MOSFET Current Buffer I/V Stage
(-ecdesigns- MK7 version)
- Separate GND-Trace for DEM-Synchroinizer
- Master/Slave
...
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File Type: zip TDA1541A Project - BOM - for The Red Baron V4.zip (9.3 KB, 179 views)
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Old

Phonoclone boards, soldering, and Q1, Q2.

Posted 7th February 2013 at 05:34 AM by rjm

This is in response to several recent emails I've received, where people were having problems with, typically, one board having a bad V+ or V- regulated voltage output.

The number of cases relative to the number of boards shipped caused me to worry that a manufacturing error might have occurred, so at my request I had a customer return the phonoclone boards he had built to me for inspection.

I'm happy to report that the problem was traced to poor soldering technique, the boards themselves are fine. What had happened was solder had cooled before the component had fully settled, and pushing the component down to the board surface then tore the trace away from the bottom of the board, breaking the circuit.

Subsequently, thinking the transistors blown, he replaced them, doing a fair bit of damage to the pads of Q1, Q2.

Fortunately, I was able to fairly quickly set everything to rights, and the boards are now on their way back to him....
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Old

Another Ikea Bowl Speaker

Posted 3rd February 2013 at 11:04 AM by googlyone

I stumbled on the people making speakers from the Ikea bowls. It kind of inspired me as the speakers were truly different and bizarre, but at the same time something completely different.

So I had to make some.

I fumbled around in the cupboard and came up with three choices of woofers that would do OK in a small enclosure - and after a few measurements and stuff settled on a pair of old Vifa M13SG-09-16 drivers. These were pretty well suited to an enclosure of a bit over 8 litres.

This drove me to the larger bowl, a 28cm one.

This is how they came out...

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To fit the driver I simply routed a rebate - and then cut the inside out.

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The material of the bowl was quite thin once I had finished routing things - so I cut out a circle of ply and glued it to the inside of the bowl. I had to go out for the evening at that point so I simply...
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Old

6C33C OTL - Completion, break in, tuning and impressions

Posted 27th January 2013 at 04:08 PM by wlowes

Done! The second went much faster and was playing music in 2 weeks.

Now that they are running I will borrow from the circuit designer's own description of the sound as it really does sum it up..

"There is no substitute for power and that is what this amp has. Complex musical passages are effortlessly reproduced with a natural depth and breadth unmatched by any other amp. Subtle nuances are clearly revealed underneath pounding crescendos.

Striking imaging causes instruments to be layered in a three dimensional sound stage that recreates the experience of a live performance. The music "opens up" and leaps out of the loudspeaker eliminating any box like sound. The most minute and subtle sounds are revealed producing uncanny realism. Musical voices are warm and lifelike yet completely neutral with a razor sharp focus."

In my own words.. incredibly natural. 3D and layered sound. Deep bass with weight creates...
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Old

F6 Clone Convertible PCB blog

Posted 27th January 2013 at 12:48 PM by Tea-Bag
Updated 29th June 2013 at 07:30 PM by Tea-Bag

Here is the F6 board rendered by CRT and some help from others.

Click the image to open in full size.


It's convertible premise is to be able to swap out transformers using daugter cardsand be able to swap out variations on the schematics Nelson Pass presented at the 2012 Burning Amp Festival.
Additionally, places for two pairs of 2SK/2SJ are here to allow GR's to be used to allow for higher than 8ma IDSS without degeneration on the front end. If you have 8ma IDSS BL grade for use here, than your all set.
You can use standard power resistors or 5MM thin film type.

Click the image to open in full size.

Here are some of the daughter cards that mount to the main board. They are available for Jensen, Cinemag and Onetics Quadfilar transformers.
These are mounted with 2 2x10 @ 2.54 mm pins. Note the PC PINs of...
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