Forums - Mini Torii SE Amplifier

Fireblade

Seasoned Member

Knowledge comes, but
wisdom lingers.
A.L.Tennyson

Posts: 628

Re: Mini Torii SE Amplifier
Reply #255 - 04/14/12 at 14:18:32

If the original source is high voltage, a passive preamp will allow this source voltage to be reduced to a point where the differential with the amp (still positive) is optimal for riding the gain dynamics at the chosen (in this case lowish) volume levels you're interested in.

You have already solved (theoretically) the excessive loudness sensitivity of your amp. We're suggesting the improved dynamics boost by either a ZStage, ZBox or simple passive preamp. The advantage of the ZStage is for lower output sources you may have in the future or if you would move to that famous designer's home with plenty of listening room ;)

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« Last Edit: 04/14/12 at 14:20:06 by Fireblade »

Laptop-Foobar2000-Wasapi Ev//WD 1.5Tb HDD//Audioquest Forest USB cbls//HRT MS II+ USB-DAC//Decware Silver Ref IC's//Decware Mini Torii SE//Kimber Kable spkr cbls//Decware DM945's//Velodyne DLS 3500//BJC SUB Cbls//Tripp Lite 500 Isolation Trnsf.//Jellyfish P. Cord

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Raduschka

Seasoned Member

Posts: 201

Re: Mini Torii SE Amplifier
Reply #256 - 04/14/12 at 14:25:38

I have to design and build it first

So it may be overkill for my high output DAC right now, but I can get the DAC's output back to 2.5V and LOWER that using the zstage. The Zstage seems more future-proof then than the Zbox. Plus I have a lot of its ingredients, so it would cost me around 60$ to build one, starting Tuesday (I am within overnight delivery timezone from PartsConnexion).

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Raduschka Seasoned Member Posts: 201	Re: Mini Torii SE Amplifier Reply #257 - 04/14/12 at 14:44:27 ...indeed, with the lowered output V on the DAC, my atts get wonderfully louder over 24 of the 48 steps!!!!! Thank you all for helping me fix this, it was teamwork.
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erik2a3

Senior Member

Posts: 95

Re: Mini Torii SE Amplifier
Reply #258 - 04/14/12 at 14:59:52

Lon : absolutely no apology needed! I just wanted to clarify thatmgain is not what is needed, IMHO. He already has excessive gain. I suggested a preamp, too, thinking Radu might already have one, as a way to attenuate the output of the DAC. His DAC already has enough voltage to drive the amp into clipping. Thus, less voltage is needed not more. Passive in-line attenuators add far less to the signal chain than would an active linestage. This situation is exactly what they are designed for. But each to his or her own Cheesy

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Have fun!
erik

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Raduschka Seasoned Member Posts: 201	Re: Mini Torii SE Amplifier Reply #259 - 04/14/12 at 15:04:07 alright, alright! if I install volume pots on the incoming signal, should I be experiencing that 'riding of the gain'? I have room in the back of the MT, and even holes, to possibly install the vol pots I took out. You suggested this at a certain satge, Erik.
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Raduschka Seasoned Member Posts: 201	Re: Mini Torii SE Amplifier Reply #260 - 04/14/12 at 15:06:36 forgive me for foruming you into the ground, but it turns out I don't know how to measure output voltage on my dac and I can't find it on google. I do have a 1khz signal though on cd.
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Lon Seasoned Member "Love without guts is worthless!" Philip K. D*ck Posts: 5233	Re: Mini Torii SE Amplifier Reply #261 - 04/14/12 at 15:12:36 Sure I can see how that should work. I will say however. . . in my experience I've never quite experienced an increase in dynamics with a ZBox (I sometimes think I've experienced a slight diminishing of dynamics) and ZBoxes can introduce or reveal hum issues.
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Raduschka

Seasoned Member

Posts: 201

Re: Mini Torii SE Amplifier
Reply #262 - 04/14/12 at 15:27:03

I get 0.1 V out of my Cd player and 0.9V out of my dac now.
Perhaps I do not need a zstage then, I am not overly attached to any particular construction, not even to the purist approach. I f I install pots on the incoming wires and find they sound great, so be it. I have too much detail right now anyway. I can mail you some Erik, if you send me your address

By the way I would love to try your inline attenuators if you are willing to go through the trouble of mailing them to me.

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Raduschka Seasoned Member Posts: 201	Re: Mini Torii SE Amplifier Reply #263 - 04/14/12 at 19:30:35 I thought I would give back some of what I took, especially to Erik But I hope you can all recognize yourselves in there... forum par raduschkamuschka, sur Flickr
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Lon Seasoned Member "Love without guts is worthless!" Philip K. D*ck Posts: 5233	Re: Mini Torii SE Amplifier Reply #264 - 04/14/12 at 19:59:46 Awesome Rad!
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erik2a3 Senior Member Posts: 95	Re: Mini Torii SE Amplifier Reply #265 - 04/14/12 at 20:51:58 That does NOT remind of Van Gogh, but too funny! Hey, am I right in understanding that your DAC once had output level controls? Not too much trouble at all to send those attenuators, but I don't think 6dB will be enough...
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Raduschka

Seasoned Member

Posts: 201

Re: Mini Torii SE Amplifier
Reply #266 - 04/14/12 at 20:55:55

It never had output controls Erik. Right now it puts out 0.9 volt and I am tempted to think it always put out 2V, not 2.5V RMS as mentioned in the specs. Somehow I don't think that with 0.9V it will be useful to install the volume pots on the signal. Ig I go back to 2V perhaps? Do you think that would allow me to experience and understand the 'riding the gain' thing?

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Les Lammers Seasoned Member Posts: 137	Re: Mini Torii SE Amplifier Reply #267 - 04/14/12 at 23:06:34 The drawing is too cool! I hope your gain issue is under control now. I may ask Steve if there is a way to lower the gain a bit when my amp is being built.
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Raduschka

Seasoned Member

Posts: 201

Re: Mini Torii SE Amplifier
Reply #268 - 04/14/12 at 23:46:30

I am waiting for Rivieraranch to notice the reference

Total bliss at the moment. I reinstalled the source selector switch and wired it as in the image. One position takes the 2.1Volts of the dac directly to the attenuator, the other one goes through the stock volume pots which are now sitting at the back of the MT and allow me total control of the input gain!
Late night audition, here I come!

vol pot par raduschkamuschka, sur Flickr

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Raduschka

Seasoned Member

Posts: 201

Re: Mini Torii SE Amplifier
Reply #269 - 04/14/12 at 23:57:23

Florida Boy,
while everything else remained the same, I now have 48 step 100K shunt attenuators in the MT and all trace of a gain problem has disappeared (except that late night 1st step volume, which I solved as explained above and which will not be an issue for anyone less paranoid than me). So I suppose it was the volume pots?

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