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Tweaking electronics sound quality in active speakers

Posted 24th May 2010 at 01:39 PM by abraxalito
Updated 25th May 2010 at 05:24 AM by abraxalito

My main listening system has been based on Fayou XPE active speakers for over six months now. I bought my first pair of Fayou speakers a year earlier than that, the lower-spec'd B2 models. The B2s are now my main PC speakers, connected to an Asus Essence ST. After getting the B2s, it was only a matter of hours before I had them open, poring over the implementation details. I noticed that the grounding to tweeter and bass/mid was shared so sliced into the board to give each unit its own dedicated ground path. I also tweaked the high current paths to the main PSU caps to ensure no impedances in common with the audio signal grounds. After these mods, the sound was highly enjoyable.

When I first heard the XPEs I considered them not to be quite as good sounding as my (tweaked) B2s, but given their superior amplification and bass/mid driver, figured they were ripe for hot-rodding. Their construction also suits tweaking much better as all the electronics is easily accessible on the...
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A New Comer to Audio

Posted 17th May 2010 at 10:49 AM by borispm

Hi everyone. This is my very first post. I am not really new to audio but I am very new to DIY audio.

I have a pair of MB Quart standmounters with a cheapo Marantz receiver and they sounded great until I heard something high end, and that's why I've joined this DIYaudio, where I can explore more about audio (especially a very special group of fullrangers).
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Krell KSA150 - Low distorted output after heated up

Posted 16th May 2010 at 08:51 AM by wabun

my Krell sings well when turn on, but left channel has low distorted output after play for 3 songs..turn it off and let it cool down, turn on again it sings normal again ! but after play for 3 songs, the left channel has low output again...unable notice any damaged component, any good suggestion how could it happen and what is the cure ? Thanks..
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Rating: 2 votes, 4.50 average.

Cathode Follower

Posted 15th May 2010 at 12:40 AM by Miles Prower

AC Coupled CF

Click the image to open in full size.

In this schemo, Rk is the normal cathode bias resistor. Rl represents the tail load in parallel with the load impedance. Rg is the control grid DC return. The CF gives excellent high frequency performance since Miller Effect is absent, and the Cgk sees very little current since the grid and cathode are always at nearly the same potential. This makes the Cgk effectively smaller than its static value. The main component of input capacitance will be the reverse transfer capacitance: Cgp. With small signal triodes, it is easy to present a Hi-Z, Lo-C load to the driving stage. This isn't just helpful at RF.

This is another circuit which has lately come under unjustified criticism within certain audiophile circles. Much of this is unjustified on the basis that the CF is a negative feedback circuit. This view that all NFB is all bad does have a basis in fact. It has...
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Rating: 2 votes, 5.00 average.

Demystifying the Cascode

Posted 15th May 2010 at 12:25 AM by Miles Prower

Basic Cascode

Click the image to open in full size.

This is what the schemo of the cascode looks like. Rk serves to establish the Q-Point bias for the lower triode, and Rg is its DC grid return. Rp is the passive plate load. The voltage divider connected to the grid of the upper triode establishes its Q-Point bias.

So why would you want to do this? What you have here is a cascade of a grounded cathode stage driving a grounded grid stage. The GC topology has the advantage of a Hi-Z input. However, its high frequency performance is impacted by a high Cmiller that only grows worse with increasing voltage gain.

The GG topology avoids Cmiller for excellent high frequency performance, but it suffers from a Lo-Z input. It's not very often that a Lo-Z input is desirable. However, you can combine the two in a manner that work together. The Lo-Z of the GG stage loads down the plate of the GC stage, reducing its gain...
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Some more progress on my Baby Huey PP EL84

Posted 4th May 2010 at 10:24 PM by Bas Horneman (Bas Horneman's diyAudio.com blog)

Unfortunately the paintjob is slowly chipping away on the edges...
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Active inductor substitutes

Posted 3rd May 2010 at 02:45 PM by DougL
Updated 14th September 2010 at 07:34 PM by DougL

Here is a circuit I like.
Not excessive voltage drop, no absolute expectations on voltage or current.

http://aquinaudio.webspace.virginmed...act_choke.html

A link to the discussion in the Tube Forum

http://www.diyaudio.com/forums/tubes...ml#post2173626
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power supply for 150w 8 ohms

Posted 3rd May 2010 at 02:01 PM by klewis
Updated 19th January 2011 at 01:53 AM by klewis

Hi,
a dual secondary 40+40Vac transformer will give ~58 to 59Vdc.
With good smoothing and a well built amp you can easily achieve 150W into 8r0.

If you want to have the ability to drive a 4ohm load then you will need to double the smoothing capacitance and double the VA rating of the transformer.

For 150W into 8r0, a 300VA with +-20mF will do.

My 230:40+40Vac gives +-58.5Vdc when fed with 240Vac and the amp bias is 220mA. It gives 170W into 8r0 from a 3pair output stage.

The power supply application note is available at http://www.national.com/an/AN/AN-1849.pdf

build the right half of the PSU in the app-note (Fig.1) and instead of all the soft-start/relay fun, put a thermistor, CL60, in series with the primary leads of the transformer.

transformer http://in.farnell.com/united-chemi-con/esmh800vnn103ma50t/cap-alum-elect-10000uf-80v-snap/dp/1363662

Andrew T notes on sizing...
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Guitar tone pot and caps

Posted 1st May 2010 at 02:52 PM by Wayne737

I have a quetion about guitar tone potentiometers and capacitors. A build I'm working on has a preamp. Must the tone control be before the preamp? And all the tone control is at the first part of the potentiometer. I want it to adjust the tone across the entire potentiometer. Would that have to do the the potentiometer, capacitor, or how it is wired?
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Shunt Regulator Wiki

Posted 26th April 2010 at 01:50 AM by DougL
Updated 28th April 2010 at 07:43 PM by DougL

Here is my brothers response to the first version of the Shunt Regulator wiki. I actually wrote it for him so he could get a clue of what I was babbling about.

Дуг,

Это бумажное средство приблизительно столько же, сколько эта электронная почта будет означать для Вас. Я думаю, что это хорошо написано. Вы будете нуждаться в этой связи, чтобы выяснить то, что пятку я только что написал Вам, поскольку это находится на русском языке.

http: // translation2.paralink.com/

Кит

Here is a translation:
Arcs, This paper means approximately so many, this how much electronic mail will indicate for you. I think that this is well written. You will require in this connection in order to explain that the fact that I recently wrote heel to you, since this is found on the Russian language.

For thoes of you that are curious, the article is here:
http://www.diyaudio.com/wiki/Shunt_Regulation
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