The official "Theta" thread - Page 258 - AVS | Home Theater Discussions And Reviews
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post #7711 of 7740 Old 01-23-2015, 07:03 AM
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Steve Kale, well if you are counting, that makes the dacs in the new Xtreme cards 2 years newer than the ones Datasat is using. I bet Trinnov too.

""Mini Gen 8," ?! : D If you truly believe that, sounds like you do, it will be true, at least for you anyway.
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post #7712 of 7740 Old 01-23-2015, 09:09 AM
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Quote:
Originally Posted by stevekale View Post

Lastly, and separately, can someone summarise for me the various revisions to the Gen VIII from 2007? A unit for sale is advertised as 'new 2007 and updated 2010' but I see a press release dated July 2011 from Theta saying they are shipping the S3. The upgrade from S2 to S3 is advertised as costing $500. Only the input board was changed? No refreshing of PSU components or other components? (I'm trying to get a sense for what's 4 years old versus 7/8.)
If you are looking at buying a used Gen VIII, get the serial #, then call Theta and they can tell you if the unit is fully the latest or what upgrade and cost it requires. Theta can also give you dates of upgrades and what was done!

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post #7713 of 7740 Old 01-23-2015, 02:15 PM
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Originally Posted by newb2012 View Post
..

If you read some of the frequent posters in this thread (in 2013/2014)- you would think (older/current) xtreme DAC is best thing since sliced bread It is easily humbled by Oppo 105 DACs (with six shooter)- and yeah you are limited in no: channels.
CB3HD with SW update should be the basis for a valid comparison to that of Oppo- I have done so (just 2 channel without 6 shooter) and there was not much difference IMHO. I do agree new xtreme DACs is a welcome development.

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post #7714 of 7740 Old 01-23-2015, 02:16 PM
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Quote:
Originally Posted by stevekale View Post
.....
Lastly, and separately, can someone summarise for me the various revisions to the Gen VIII from 2007? A unit for sale is advertised as 'new 2007 and updated 2010' but I see a press release dated July 2011 from Theta saying they are shipping the S3. The upgrade from S2 to S3 is advertised as costing $500. Only the input board was changed? No refreshing of PSU components or other components? (I'm trying to get a sense for what's 4 years old versus 7/8.)
Steve K,

If seller does not know Gen VIII is a S2 then chances are it is not . Gen VIII S1 to S2 was a significant overhaul (and pricey ~$2.5K) , while S2 to S3 update was to change to input receiver-input board to accept hi-rez signals. You can check Jason V detailed posting on S2 HERE

If Theta has records they may be able to validate with serial no:, but most likely internal pics have to be taken to confirm updates.

You will be pretty happy with Gen VIII- go for it.

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post #7715 of 7740 Old 01-23-2015, 03:34 PM
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Cool When are orders for the 12 channel dac being taken?



Hey Jeff, here is a perfect oportunity to start getting Theta gear into atmos mix rooms. This one is 34 channels, id like to spec three of the 12 channel dacs. It would be connected to the cp-850 processor and a bss blulink to aes converter or fed from NEVE console. But how would the volume be controlled on the dacs rs-232 (special interface to neve console?


Inquiring minds want to know....

You may also want to (engage FLAK shield) keep the look more Spartan and less Cherubim Palladian as a rack mount pro option for atmos/dtsx mix rooms.

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post #7716 of 7740 Old 01-23-2015, 04:43 PM
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post #7717 of 7740 Old 01-24-2015, 06:31 AM
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Cineramax, take such directly with Theta. I can't see this has anything to do in this thread.
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post #7718 of 7740 Old 01-26-2015, 07:58 AM
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I'll try to get the serial number. At the moment the item is listed at far too high a price and the seller doesn't even bother to return voicemail messages which is, well, ___ [you fill in the blank]

Also, precisely how is volume attenuation done between the CB and the Gen VIII? Is it that the CB attenuates the digital voltage signal passed to the Gen VIII or is it that the CB passes volume control commands to (what I understand to be voltage attenuation in the analogue domain of) the Gen VIII?

(BTW a must read for all those who think running big uber-W amps at low (relative) volumes is the way to go:

http://www.diyaudio.com/forums/diyau...structure.html )

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post #7719 of 7740 Old 01-26-2015, 09:19 AM
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Quote:
Originally Posted by stevekale View Post
Also, precisely how is volume attenuation done between the CB and the Gen VIII? Is it that the CB attenuates the digital voltage signal passed to the Gen VIII or is it that the CB passes volume control commands to (what I understand to be voltage attenuation in the analogue domain of) the Gen VIII?
I can only tell you that the Gen VIII syncs perfectly. You set the Gen VIII's menu for the channels that its used for (I use on Gen VIII set for front left and front right channels). When you turn on stuff, turn on Gen VIII first, then turn on CB whatever model it is. Then the volume on the Gen VIII will move precisely with the volume on the CB, and you then only use the CB's volume control whether by remote or on the front panel.

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post #7720 of 7740 Old 01-26-2015, 09:18 PM
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Quote:
Originally Posted by Steve Bruzonsky View Post
I can only tell you that the Gen VIII syncs perfectly. You set the Gen VIII's menu for the channels that its used for (I use on Gen VIII set for front left and front right channels). When you turn on stuff, turn on Gen VIII first, then turn on CB whatever model it is. Then the volume on the Gen VIII will move precisely with the volume on the CB, and you then only use the CB's volume control whether by remote or on the front panel.
Hi Steve, what connections are you using as the digital umbilical to the gen 8?

I assume the pair labelled external volume data is not a left right pair but an in out for daisy chain of theta devices,right?

In that case a third party device control would interface through the rs-232, but like SK says it would be interesting to know if the CB is relegating control to the dac only (for the channels involved) or if both devices volumes are somehow moving in tandem....
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post #7721 of 7740 Old 01-26-2015, 11:17 PM
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The CB sends volume control data to the Gen VIII which adjusts its analog output accordingly. So yes, the CB volume and its analog outputs are moving in coordination with the volume data sent to the Gen VIII which applies the commanded volume to its analog output.

The CB level adjust applies to the volume data outputs as well as the CB analog outputs.

As long as the CB and Gen VIII gains are the same this architecture will result in a balanced volume across all channels; and I can attest that it does.

Hope this helps.
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post #7722 of 7740 Old 01-26-2015, 11:28 PM
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Originally Posted by jjwinterberg View Post
The CB sends volume control data to the Gen VIII which adjusts its analog output accordingly. So yes, the CB volume and its analog outputs are moving in coordination with the volume data sent to the Gen VIII which applies the commanded volume to its analog output.

The CB level adjust applies to the volume data outputs as well as the CB analog outputs.

As long as the CB and Gen VIII gains are the same this architecture will result in a balanced volume across all channels; and I can attest that it does.

Hope this helps.
Absolutely, Is this done in 256 increments or 110-115?

Im sure it works great in Theta,

I do have a problem with the Piano company that it does the same to their digital amps internal dacs but somehow the sound appears to lack one more db of dig preamplification to the power dacs, the sound is missing "air" "sounds trapped". I guess the 8 dac and the digital power amp components are better than the tact tech.

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post #7723 of 7740 Old Yesterday, 12:21 AM
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Originally Posted by CINERAMAX View Post
Absolutely, Is this done in 256 increments or 110-115?

Im sure it works great in Theta
Peter,

Sorry but I don't know the format of the volume data sent between the CB and the Gen VIII. The CB's volume control ranges between 0 and 73.

I'm glad for your interest in putting the CB into one of your theaters. Even though I'll never approach the degree of sophistication in your worlds, it will help advance Theta and their products in a similar fashion to how auto racing advances the technology of my car.

Thanks!
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post #7724 of 7740 Old Yesterday, 07:00 AM
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Originally Posted by jjwinterberg View Post
The CB sends volume control data to the Gen VIII which adjusts its analog output accordingly. So yes, the CB volume and its analog outputs are moving in coordination with the volume data sent to the Gen VIII which applies the commanded volume to its analog output.

The CB level adjust applies to the volume data outputs as well as the CB analog outputs.

As long as the CB and Gen VIII gains are the same this architecture will result in a balanced volume across all channels; and I can attest that it does.

Hope this helps.
Ok thanks. I've been trying to find a decent picture of this card. From what I can see, there's just a series of (AES/EBU) connections for channel pairs. Therefore, I don't see how the volume control signal is sent to the Gen VIII. One wouldn't, I think, have a volume instruction/control signal ride along with the digital audio signal but maybe I am wrong there. It would, therefore, seem more likely that the CB or the Digi-Out card executes volume control by attenuating the digital voltage level going into the Gen VIII. (Of course volume changes to the CB analogue out and the Gen VIII analogue out would move in unison.)

Perhaps Jeff can clarify.

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post #7725 of 7740 Old Yesterday, 07:06 AM
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Quote:
Originally Posted by CINERAMAX View Post
dig preamplification
A somewhat erroneous term. A pre-amplifier's volume control attenuates rather than increases the voltage signal going to the (external) power amplifiers, the latter having a fixed voltage transform.

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Originally Posted by stevekale View Post
Ok thanks. I've been trying to find a decent picture of this card. From what I can see, there's just a series of (AES/EBU) connections for channel pairs. Therefore, I don't see how the volume control signal is sent to the Gen VIII. One wouldn't, I think, have a volume instruction/control signal ride along with the digital audio signal but maybe I am wrong there. It would, therefore, seem more likely that the CB or the Digi-Out card executes volume control by attenuating the digital voltage level going into the Gen VIII. (Of course volume changes to the CB analogue out and the Gen VIII analogue out would move in unison.)

Perhaps Jeff can clarify.
The digital volume data is sent over its own cable from the CB's digital input card (the volume data connectors) to the external volume data connection that Peter showed in his picture.
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post #7727 of 7740 Old Yesterday, 10:16 AM
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Originally Posted by jjwinterberg View Post
The digital volume data is sent over its own cable from the CB's digital input card (the volume data connectors) to the external volume data connection that Peter showed in his picture.
Ah excellent. From the "Vol" RCA connector shown here:

http://thetadigital.com/images/Casablanca_IV_Rear.jpg

Thanks. Everything now makes sense.

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post #7728 of 7740 Old Yesterday, 12:19 PM
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Originally Posted by stevekale View Post
A somewhat erroneous term. A pre-amplifier's volume control attenuates rather than increases the voltage signal going to the (external) power amplifiers, the latter having a fixed voltage transform.
Most, if not nearly all, preamps are capable of more than unity gain, no?

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post #7729 of 7740 Old Yesterday, 12:25 PM
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Why I mentioned 'volume control' which is attenuation.

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post #7730 of 7740 Old Yesterday, 01:02 PM
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Originally Posted by jjwinterberg View Post
Peter,

Sorry but I don't know the format of the volume data sent between the CB and the Gen VIII. The CB's volume control ranges between 0 and 73.

I'm glad for your interest in putting the CB into one of your theaters. Even though I'll never approach the degree of sophistication in your worlds, it will help advance Theta and their products in a similar fashion to how auto racing advances the technology of my car.

Thanks!
It has become much clearer now how it works...

Thanks so much for the kind words in understanding my motivational thought processes, cheers.
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post #7731 of 7740 Old Yesterday, 06:21 PM
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I assume the pair labelled external volume data is not a left right pair but an in out for daisy chain of theta devices,right?
Yes, volume for all of the channels out of a Casablanca is in that signal. In the case of the Six Shooter, Theta's analog 6 channel preamp, it is set to respond to either the first 6 channels or the second 6 channels by a jumper inside the case. So you can have 1 Six Shooter cover the channels 1-6 and another cover channels 7-12 in the current 12 channel set-up. In the case of the Gen 8, it can be set to respond to two channels, for example channels 1 and 2, or channels 3 and 4 or channels 5 and 6, etc. You get the point. That volume control data signal is just daisy chained out of each component. Each component has a method to respond to the channels to which the device has been configured to respond. It doesn't matter which order the component receives the volume data because the component will only respond to those channels to which it has been set.

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post #7732 of 7740 Unread Yesterday, 06:42 PM
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Originally Posted by stevekale View Post
A somewhat erroneous term. A pre-amplifier's volume control attenuates rather than increases the voltage signal going to the (external) power amplifiers, the latter having a fixed voltage transform.
A passive preamp attenuates. An active preamp like all Theta ones, actually increase gain, voltage. The Gen VIII does 9 VRMWS. None of Theta's products have passive volume controls. They all can add gain. That's why passive preamps can sometimes lack dynamics. You can not add any gain only attenuate.

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Originally Posted by cannga View Post
Most, if not nearly all, preamps are capable of more than unity gain, no?
Right, the vast majority of preamps on the market are active, add gain, voltage. Passives are so few, that it is hard for me to even think of many.

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Yes they include passive gain (typically circa 2-4x) ahead of volume control. Volume control attenuates voltage. Depending on your power amp (read big over-powered power amps) you might attenuate voltage to, say, 1/20th. The passive pre-amp gain is reversed, signal level to the amp reduced, system SNR reduced.

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The Gen VIII does 9 VRMWS. None of Theta's products have passive volume controls.
Hmm...now let's do some rough math. 9V RMS input to an amplifier with, say, 31dB (36x) gain would require the amplifier to deliver 458Vpk and have voltage rails with headroom above that. Even the UK mains supply doesn't extend that far and even if it did I would not want that sort of voltage going to my speakers. Send it 9V and even an enormous amp severely clips.

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Active preamps add gain, Steve Kale. Whether the amp needs the max boost is a separate issue.
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I think you should read more about gain structure. The article I linked to above would be a good start. You can also start from the other end. Choose a listening peak SPL level, number of speakers, listening distance, speaker sensitivity, voltage gain of the amplifier of your choice and derive the voltage level fed to that amplifier to achieve your starting point.

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Quote:
Originally Posted by stevekale View Post
Yes they include passive gain (typically circa 2-4x) ahead of volume control. Volume control attenuates voltage. Depending on your power amp (read big over-powered power amps) you might attenuate voltage to, say, 1/20th. The passive pre-amp gain is reversed, signal level to the amp reduced, system SNR reduced.
What's "passive" gain?
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In my case I was referring to any - if any - flat level of gain separately from voltage-attenuating volume control. 'Fixed' might have been a better term. Now BD may split hairs and argue that the two elements aren't separate and that instead there is one voltage control - up or down. But even if that is so, that is beside the point I was trying to make.

I guess all this is rather off-topic but I just found it interesting to realise just how much voltage attenuation is required for relatively 'normal' listening levels with the sorts of power amps we love, even with extremely inefficient speakers. Take my very inefficient Andra III. They have an advertised sensitivity of 88dB (dB per 1 watt at 1 metre) which equates to an efficiency of about 0.4%. I couple them to a mere, in the context of some people here, 200W per channel amplifier with a gain of 26.4dB. If I want to listen at an average SPL level of, say, 80dB 3m from the speaker pair (I sit closer actually), that's a mere 0.75W approx output from the amp. As I understand it, assuming a load of 8 ohms, just for arguments sake, that's 3.5V out of the amp (Vpeak = SQRT(2 x Power x Resistance). My Krell FPB 200 amp has a gain of 26.4dB, a voltage gain of just shy of 21x i.e. 3.5V out equates to 0.16V in. The 'pre-amp' needs to cut the 'benchmark' voltage level from a CD player in half before it hits my amp. In terms of any SNR the numerator is cut in half. Hence the quip which I didn't intend to start such a debate.

PS: if there's a problem with my calculations above then please don't hesitate to point it out.

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Quote:
Originally Posted by jjwinterberg View Post
What's "passive" gain?
In this context, it's not possible. You will hear about passive gain associated with antennas, but it's not really passive gain either. You are simply tuning the antenna to a band of frequencies as the expense of others.

Gain on projection screens and another example. How does a passive object give back more light than it receives? It simply cannot in this universe. The "gain" comes at the expense of the uniformity, IOW, hot spotting. The screen is acting as a lens.

Any active amplifier adds noise. Fact of life. So it's not ideal to put a high gain preamp in front of another amplifier only to knock the preamp gain down by an attenuator. The noise form the preamp is added and will never go away. You may however have a slight advantage as the power amp is operating at a different point in it's SNR curve.

But all in all you don't want excessive gain at any stage in any electronic system. Passive preamps work on the principle that modern signal sources have around 2v of output voltage. That is typically more than enough to drive any competent HiFi amplifier to full power.

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