Your T-amp got better quality and more precise trimpots than Vincent's.
I wonder if thats for ouput DC adjustment or output Bias.

Hi guys,

Welcome to Fantasy Island. I am Mr C, your host for the day and this is Tattoo (T-amp), sounds familiar to all?

Okay (trying level best to be serious), I was nominated to be your first host for our first T-amp “teh tarik” session. As the response is overwhelming good with possible inclusion of few other likeminded hobbyists in Ekool, Vincent, and (who else did Jazzy and I missed out? Kindly do accept our apology) ………….…. could I be allowed to suggest that we convene the session in my office premises at USJ 10 of Subang Jaya instead of at my humble abode?

Reasons being:-
(1) I do not have a dedicated listening room at home and my main system is in the living hall; our T-amps would have a tough time trying to sound decent in there.
(2) IMO, our T-amp may not be able to drive the pair of loudspeakers in my main system; whatever sound we are going to hear would be devoid of any meaningful bass / low extension that many of us look forward to.
(3) My T-amp system resides in the master bedroom of my house; I do not feel my Home Minister would be too happy with us having our session in there.

Could any kind Samaritan bring along a pair of 24” height stands for the session? I shall provide the rest of equipment needed.




This post has been edited by Y.C.: Oct 9 2008, 02:56 PM

According to the `instructions manual' the trim controls are there to adjust the volume and balance between the 2 channels. So I guess it is DC adjustment? If for bias, it would affect the frequency response, right?

Now I have a totally wild thought. Since I'm using a pair of the TA2022 in bi amped mode, I can actually use the trimpots to adjust the relative signal volumes to the tweeters and woofers on each speaker separately....in effect, I can `tune' the sound to increase or decrease the overall brightness, and bass response (within limits, of course). Or am I going overboard with my imagination?

bro march,
I think that is a workable solution! Go for it!

Yes Mr C! I would be most delighted as your office is only a couple of minutes walk from my house! It actually would take me longer to drive as I would have to do some u turns and find a place to park!

I can bring my sandfilled stands if you don't mind the stained paintwork and rustspots. I'll also bring along my battered pair of Heybrooks 'cause if the TA2024 can drive them to reasonable loudness, I'll get one T-amp kit and turn these old speakers into a pair of pc multimedia transducers.

---

Added on October 9, 2008, 3:32 pmjazzy bro, you are so uplifting!

But before I start turning them tiny screws, I'd better figure a way of calibrating the levels so that if things don't work out, I can still set them back to the original factory defaults. Any suggestions? I think I will need a constant tone generator, and some kind of meter/oscilloscope to measure/record the output. Can a simple multimeter switched to the AC measurement work for the second part? Would I also need to jury-rig a dummy 8 ohm resistance to simulate a speaker load?

This post has been edited by March05: Oct 9 2008, 03:32 PM

[quote=March05,Oct 9 2008, 03:16 PM]
But before I start turning them tiny screws,
Uplifting huh?... you fry your speakers, he'll likely offer his condolences as well!..


You better don't simply "twist-twist" those trimpots with your exensive live speakers. Experimentation is usually done with a AC/DC voltmeter connected in parallel with a 30W dummy resistor load that'll absorb any undesirable voltages or DC surges.

bro march,
bsl has said it all!

I think to mark the default position, use a fine tip marker and.. well you know the drill!
Now I wonder, if you don't connect to your 'live' speakers then how would you know exactly how much to adjust/turn? You turn very sloowwwwly...

What ho! my guardian angel to the rescue again!

One lesson I've learned from bsl, after all this time, is always to proceed with EXTREME PRECAUTION if you go where angels fear to tread!

And Jazzy bro, you give me encouragement to be ADVENTUROUS (otherwise I'll just go back to my mundane, boring lifestyle).

Between the two of you, I guess I've got all the important angles covered!

But this is one very good (bad) example of the Mr Hyde I become when I get into a DIY mood. I start to run wild with plans without seeing the long term effects.

Okay, back to this screwing...pardon my language, folks. Jazzy bro, these screws are so tiny I need a fine jeweller's screwdriver to turn them. I think the finest marker may be too coarse to be precise. But I'll put the mark there anyway...the advice is good, and it won't cost me a sen.

I would like to play the sophisticated DIYer this time, and purpose-build a meter with that dummy load bsl mentioned. Now the million dollar question is: Who's got a design I can copy and make? The resistor should ideally be 8 ohm, 30W (or higher?) rating, isn't it? What range should the meter be, and measuring AC or DC ? Logic tells me AC, but then, my logic is not infallible.

Can I generate a pure one note, continuous sine wave tone using my pc sound card - just using the MIDI synthesizer should do it, I think....or some other source would be better?

Questions, questions, but I think this will also work with a pair of TA2024s except you do it with volume pots feeding the input....

Errr...if you want, I can lend you my 8ohm load resistor and spare analog multimeter lah.. then you can go screwing around. Yes, you'd need a jeweller's flat blade screwdriver. I think the trimpots are for DC offset adjustments. Just adjust till you get ZERO or near zero DC voltage at output. One of them should be for the gain.
I've not looked at the circuit so I'm only guessing. There's quite some variation over various brands of this T-amp.
The load resistor is wired up with speaker terminals..just plug it in.

This post has been edited by bsl555: Oct 9 2008, 05:50 PM

bro march,
you're right about using a fine jewellers screwdriver! OR if you're a 'macgiver' kind of guy, a small swiss army/victorinox knife, which any good DIYer should also have, should do the trick nicely
Yes I know they are rather tiny.. normally I would mark the position of the screwdriver slots on the board adjacent to the trimpots, with one half of the top of the trim head 'painted' with the marker and to make sure you don't really messed up, take a macro pix of the default settings.. too much huh?

bsl proposal of using a dummy load is good. you can actually take the default reading of the output. It is definitely AC out.. what signal you should fed.. well if you have a signal generator.... To keep thing simple (KISS) a contant tone should be sufficient.. how? I think you know how..

Good luck bro!

I recently replaced those same precision trimpots in the NAD for DC offset and DC bias. The settings are certainly more precise compared to the original which were really nasty and way off its desired values.

Certainly this would a daunting task not to be taken lightly, but I guess with a service manual, good DMM and the necessary data/figures available, these would help in getting the right 'tune' so to speak.. otherwise it would be a 'hit & miss' affair?

Done Deal! bsl, I'm older than you, so I can use those words **XXXXXX**, not you, kiddo.

Now you wouldn't happen to have a spare tone generator lying around somewhere in your hidden-warehouse-disguised-as-a-normal-house, would you. Okay, okay, I won't push my luck too much today.

Jazzy bro, I guess your hint says it about the tone generation device...unless I'm reading you totally wrong! Macro pix no problem lah. You're looking at Mr Eagle Eyed March, Photographer of the Month. My compact Casio should do the trick for the time being. My Canon 5D Mark II hasn't arrived yet.

Question again, what frequency is good to use as a reference? 1Khz?

bro march,
I couldn't help but smile on the term "hidden-warehouse-disguised-as-a-normal-house" Me and Madziz, we suspected there's a few underground levels... That would certainly explains where 'those' things came from! hahahaha..

You read my mind lah! Now who among us would have a tone/signal generator?

1 kHz would be sufficient I think as my 'signal injector' (DIY KIT) that I sometime use, also transmit around the same frequency region, unless 'sifu' bsl says otherwise...

Yes, I have a Signal generator. There's another way to do it. Find some testtones on the internet, 100hz, 1khz and 10kz. Write them to CDR and play it back on your CDP connected to T-Amp.
Yep..I have a oscilloscope too.. heheheheh!
I could have splashed out for a used Audio analyzer but I don't think I'd justify the use..

This post has been edited by bsl555: Oct 9 2008, 06:19 PM

Oh yeah, those test tones are available for downloads
bro march, its your move!

but I wanna use a proper signal generator!

bsl, I wanna use that oscilloscope too!

Oh sh*t, Mr Hyde's loose again!

March,
Thank you so much.

We'd need to wait for response from others; I could come and pick the items up from your house if it's ON as it'd not be fair to let you tug them all the way from your house alone.

Y.C., that'll be a great help. Somehow these days I'm not as young as I used to be. It'll also save me the trouble of giving you directions when I hold the turntable -TT session at my place once my CA640P arrives and is fully settled in. But be prepared to do a bit of weight lifting, these Malaysia Boleh! Atacama clones are quite hefty, especially when sandfilled.

Bro, if you worry about setting them back to its original position, a better way than "tip marking" is to measure its resistance between center tab with either left/right tab (in power off state).

I believe by using this way, it won't run far away from its original value.