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FALL Listening Space

Posted 3rd January 2011 at 06:53 AM by planet10

How many posts, describing the sound of something, have the caveat, "...in my room"?

My listening space/room is a subset of the upper floor of my house. All the volume of this space is fairly open and interconnected acoustically.

Click the image to open in full size.

The space is nominally 24'x36' (houses in Canada are still built in imperial units) surrounded by deck on 3 sides. The peak of the roof is at 2/3 and rises 17' at the highest. It slopes down over 24' to ~6.5' over the main room. An 8' x 12' section is divided off for kitchen with the bedroom above.

Click the image to open in full size.

The rest of the space is 12'x24', raised 42" above the main floor and has a roof (mostly) that vaults from 8' to the same peak (just over 12'). The main space & this space are connected by 2 -- 3.5x7' openings and 5 -- 16"x2.5'...
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Old

D1080 MkII 08 actives - mod summary and listening

Posted 1st January 2011 at 12:41 PM by abraxalito
Updated 2nd March 2011 at 12:12 PM by abraxalito

Before describing the changes brought about by the mods I've described, here's a summary of what they've been:
  • Crossover tweaked to flatten the lower end bass hump and knit the handover to the tweeter more tightly
  • Power amp sensitivity reduced to allow the volume control operate closer to maximum with my Asus soundcard or a standard CD player output.
  • Rectifier snubbers and additional filtering to the regulators fitted to reduce RF ingress on the power supplies.
  • Power amp supply decoupling improved at both LF and HF.
  • Signal grounds are now separate from power grounds and a star point established on the amp PCB. A ground loop between the two PCBs has been eliminated. The input signal ground is no longer connected to the tone control PCB ground - instead given its own dedicated wire to the star. Decoupling to ground on the tone control PCB has been removed.

Listening impressions

OK, so on to the part that you've been...
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Old

how to connect guitar jack socket to ruby amp

Posted 28th December 2010 at 10:38 AM by sam56

hey please help, in ma ruby amp, all other circuits are working but can't give input to it..please help???
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Old

transistors for front end

Posted 24th December 2010 at 02:18 PM by klewis
Updated 31st October 2012 at 12:55 AM by klewis

This thread.
http://www.diyaudio.com/forums/solid...tp-choice.html

Sources:

http://www.utsource.net/index.aspx

http://www.taydaelectronics.com/servlet/StoreFront

Sadly the 2SC2240 and 2SA970 (npn, pnp) super-low-noise trannies in TO-92 packages no longer appear on Toshiba's Bipolar Transistors Product List, and have been designated NRND by Toshiba (Not Recommended for New Designs). [link] This means the factory is presumably still taking (large) orders, but they are destined for the dust-bin of history. FYI, last chance, B&D still has some inventory.

But, not to fear, Toshiba offers what appears to be the same (or better) die in SOT-23 packages, the 2SC3324 and 2SA1312. These are stocked by Mouser, and cost only 15 cents qty 100. Their datasheets are fairly complete, including two NF contour plots. The 1kHz plot shows the 3dB contour dropping 35 ohms at 1mA and below...
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Old

D1080 Mk II 08 actives - initial listening and some refinements

Posted 23rd December 2010 at 01:49 PM by abraxalito
Updated 2nd March 2011 at 12:14 PM by abraxalito

Having disassembled the amp board from its backplate once and got heatsink compound in various undesirable places, I was hoping that the first round of mods would also be the last. No such luck

However, first listening was extremely promising, so I was definitely up for a second round of extreme messiness to gild the lily. I did notice that my grounding changes had introduced a slight hum (50Hz fundamental only it seems) which was only audible when no music was playing and was independent of volume setting. The main gripe I had was that the stereo image was shifted over to one side - this I decided was because the volume pot was being used towards the lower end of its range where the matching is poorest. The chip amps have rather high gain (32dB in bridged) and this can't be reduced. So the solution had to be modding the resistive dividers between the XO and the amp chips - in effect reducing the power amp sensitivity. I went for about a 9dB reduction, determined by the...
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Old

D1080 Mk II 08 actives - XO mods

Posted 23rd December 2010 at 12:21 PM by abraxalito
Updated 5th March 2012 at 03:53 AM by abraxalito

Here's the schematic showing the component value tweaks I made to the tone control board. I'll list the changes in detail - only the first three are depicted in the schematic. The remainder aren't as they don't show up on the sim plots

1) The original input stage has attenuation followed by gain. I have removed both, its now a unity gain stage and also no longer rolls off the HF response.

2) The low-end high-pass filter originally had a rather too high Q for my taste. It's been tamed.

3) The bass-mid low-pass filter was rather too low Q, so I've brought this up, making the response flatter across the band - now the hand over to the tweeter is tighter. The tweeter high-pass is left unchanged.

4) The decoupling regime has been changed so as not to contaminate the local ground. Thus the original 100nF ceramics to ground from either supply rail have been moved to decouple between the positive and negative rails. Ground is thereby...
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Old

D1080 MkII 08 actives - power supply mod details

Posted 17th December 2010 at 04:34 AM by abraxalito
Updated 5th March 2012 at 03:54 AM by abraxalito

When considering how to hot rod a particular piece of electronics, my first attention always goes to power supplies and layout rather than the somewhat more popular approach of swapping out components for boutique variants. This is because so far I'm not sure that I notice the differences between audiophile grade caps (for example) and the bog standard ones. But I am sure of the differences brought about by improved grounding - to my ears these aren't subtle changes at all. So if I turn out to be dissatisfied with the sound of my layout mods, then I'll turn to tweaks on individual parts.

On examining the layouts of the two PCBs (XO layout already shown in a prior post) it turns out the amp PCB is the one with the relevant power supply components. In more detail, it has two independent supplies coming from separate windings on a standard EI-core transformer. The higher current one is unipolar, unregulated and feeding only the TDA8947s, the small-signal supply is bipolar,...
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Old

Simple PSU

Posted 16th December 2010 at 02:36 PM by ferynov
Updated 17th March 2011 at 03:32 PM by ferynov (edit)

my own Simple power supply for my own use...

For DAC Reference TDA1541+salas shunt Reg.

Click the image to open in full size.

Click the image to open in full size.

For Power Amplifier DX Blame :

Click the image to open in full size.

Click the image to open in full size.

Another small pcb for power amp too :

Click the image to open in full size.

Click the image to open in full size.

if wanna download...
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Old

Guitar Amps...

Posted 15th December 2010 at 05:38 PM by chris661

Now then (does that make sense?).

Today, I played a small gig at a college (6th form) talent show. Maybe 100 people or so in the audience.

So, some background... I bought an old, faulty guitar amp off ebay. A resistor (1/2 watt one) had burned, as well as one of the output stage transistors. This had got hot enough to short one of the rails to the speaker output. This killed off the vintage Celestion driver in there. Lovely. Next up, the power supply was under-done. The mains transformer had been replaced before I'd got it (odd screws used to hold it in), and the old 2,200uF caps failed to meet half that value. The rectifier was a small chip, stood on the circuit board.

So, using a spare Eminence driver (modified Alpha 10 - felt dustcap, looser suspension), I fired it up, hoping there was some life in it. Life, there was. Lots of volts DC on the output, with a 100Hz buzz on top of that. Needless to say, I switched it off again.
Replaced...
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Old

D1080 MkII 08 actives - crossover schematic

Posted 15th December 2010 at 03:28 AM by abraxalito
Updated 5th March 2012 at 03:54 AM by abraxalito

Here's a somewhat simplified schematic I entered to model the response curves in LTSpice. The volume control isn't shown (as LTSpice doesn't have the symbol) but happens before the first opamp. I've fudged up symbols for the bass and treble controls - they're simply variable resistance in the HF and LF feeds to the power amp board. LT1057 isn't actually used in this unit, its just the nearest library part to the TL084

<edit> I've added the response curves now - look and weep
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