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Playing Vinyl on a TD-124

Posted 6th January 2011 at 08:50 PM by kevinkr

I acquired a TD-124MKII back in late September and after some months feel like I have come to some understanding of its strengths and weaknesses.

I finally understand that the drive train will never be silent, and needs some periodic maintenance to perform quietly.

Belts are problematic on the MKII, and later versions of the MKI with the dual in chassis intermediate pulley. For some reason very early units seem quieter in this respect.

Motor rebuilding is pretty worthwhile, mine of course was not running so it was mandatory. My experience with motor bearings is limited, but based on replacing a number of bearing sets I would recommend the bearings available from The Analog Depot over others I've tried. They are very precisely made and run well from the get go.

I've added a Bren1 record weight which I feel clamps the record more effectively to the table's moving mass, and I thought improved some areas of performance significantly. Bass...
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PreAmp Circuit

Posted 4th January 2011 at 11:33 PM by Lesa

Hello guys,

I was wondering if any genius out there who knows about preamp circuit who can explain this one to me.

See I am just getting into audio systems design and I am try to understand this preamp circuit and how it works.

A few questions:

1)what does the two cap in series does and why are they connect to ground?

2) what does R3, R1 and R2 does?

3) What is the uses of the polarity Reverse?

I have been reading up on these component but i am a little slow on understanding.

I would appreciate the help.
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IRS2092, Iraudamp 7D Delta Sigma?

Posted 4th January 2011 at 03:23 PM by vcougar

Hi I'm new here and hope you can help me.

Currently I am workingwith thecircuitIraudamp7Dwith theblockIRS2092. Unfortunately I dont understand with which type of modulation this circuit operates. In the datasheet of Iraudamp 7D is written that it is powered bythedelta-sigma modulation. But I not see the dealy flip flop. And the clock is with 400 Khz very small for Delta Sigma.
Can You confirm that this is by delta sigma?

for your help I would be very grateful!

Sorry for my bad English im from germany.

Iraudamp 7D:

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FALL Listening Space

Posted 3rd January 2011 at 05:53 AM by planet10

How many posts, describing the sound of something, have the caveat, " 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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D1080 MkII 08 actives - mod summary and listening

Posted 1st January 2011 at 11:41 AM by abraxalito
Updated 2nd March 2011 at 11:12 AM 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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how to connect guitar jack socket to ruby amp

Posted 28th December 2010 at 09:38 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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transistors for front end

Posted 24th December 2010 at 01:18 PM by klewis
Updated 30th October 2012 at 11:55 PM by klewis

This thread.


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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D1080 Mk II 08 actives - initial listening and some refinements

Posted 23rd December 2010 at 12:49 PM by abraxalito
Updated 2nd March 2011 at 11:14 AM 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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D1080 Mk II 08 actives - XO mods

Posted 23rd December 2010 at 11:21 AM by abraxalito
Updated 5th March 2012 at 02:53 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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D1080 MkII 08 actives - power supply mod details

Posted 17th December 2010 at 03:34 AM by abraxalito
Updated 5th March 2012 at 02:54 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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