6 channel transformer-based attenuating pre?

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PeteHK

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6 channel transformer-based attenuating pre?
« on: 7 Jan 2003, 10:56 am »
John,

I need a quality source selector/volume control for 4 multi-channel sources (SACD, DVD-A, computer and home theatre).

The currently available choices appear to be:
Sony TA-P9000ES (about US$500 if you can find them)
Meitner Switchman II (about US$3,000)
AV Reality (price?)

The choice is a bit limited as I guess that manufacturers are waiting for digital out standards to be decided upon. This could take some time ...

Just thinking out loud and given the reviews (and having listened to a friend's S&B based DIY effort), I was wondering if it might be possible to do this using transformer based attenuators? 6 (or 8 for 7.1?) transformers in a case with switching for 4 sources?

I guess the same result could be achieved by buying 3 pre's, but the possibility of an all-in-one box appeals to me.

Any thoughts or alternative suggestions would be appreciated.

Cheers,

Pete

John Chapman

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    • http://www.bentaudio.com
6 channel transformer-based attenuating pre?
« Reply #1 on: 7 Jan 2003, 03:45 pm »
Pete,

Thanks for the post! The TAP system was designed for this and if I'd got off my butt and finished it quicker it would have been the first multichannel pre-amp out there as the design began 5 or 6 years ago. It was not origionally for multichannel music like SACD or DVD-A but it was made to do multichannel level control for DSP based crossovers I was brewing up that used  multiple DAC's for Low Freq and Mid / High Freq bands.


The TAP system was designed for multichannel and  is ready today to use a TAP Base Unit and then plug 3 stereo TX102 based bent units into it for 6 channels total (or 4 units for 8 channels although there are no 8 channel music sources). This would only make any sense in the highest end multichannel SACD system from a cost point of view - it would cost about $4K and even more if silver TX102's were used for the main channels.

To keep the cost af a multichannel system I have a new board in that 'almost done' phase and should have it complete in the next couple of months. This board will plug into the Base Unit and will do the level control for 4 channels. The level control is done using the PGA2310 SS level pot (an improved version of the cs3310 chip Rowland uses in their pre-amps). Despite that it is designed to be a cost effective board it uses things like shunt regulation and OSCON caps - I could not help myself! This 4 channel board allows for up to 4 inputs to each channel. I'm hoping to keep the cost around the 1K mark which would mean a 6 channel system using the TX102's for the main channels and then this board for the additional channels would come in at about 3K or $3350 with silver TX102's for the main 2 channels.

If the Center channel was an exact match to the mains you could use a TX102 for that channel as well but unless it was an exact match I'd think the differences between the TX102 and the PGA level control would be swamped by the differences in the speakers.  

I'm afraid puttin all this in one package is not practical due top the size of Parts. The system above would be 3 'boxes' - The Base Unit (with the blue lights) which can be located anywhere in the room, then the Stereo TX102 unit and then finally the 4 Channel Unit. The separate boxes can be placed anywhere as there are no knobs on them and this can help to minimize imnterconnect lengths.

Putting 6 TX102's in a box with a 6 deck switch would work but would be limited as it would not allow for trimming the individual channels levels. This could be done if you had an alternate way of level matching the channels and we could even put a remote control on it.


Many Thanks!

John Chapman
www.bentaudio.com

PeteHK

  • Jr. Member
  • Posts: 28
Thanks for the response!
« Reply #2 on: 14 Jan 2003, 01:11 pm »
Many thanks for taking the time and trouble to answer my query, John.

A (temporary) solution has already been raised on this board in another thread (using the TVC for 2 channels and pre-pro for the surrounds, thanks JoshK), so I might give that a go.

I'm not in any real hurry, though - currently trying to build my home theatre (HTPC, projector, pre-pro...)

I look forward to hearing more about your upcoming products and how they might fit into my system. Must also have a more detailed look at your website.

Cheers,

Pete

Kishore

6 channel transformer-based attenuating pre?
« Reply #3 on: 25 Jan 2003, 09:59 pm »
John,

If my understanding is correct TAP would be great for both 2 Channel and multi-channel without any compromise (i.e you need not have a dedicated pre for 2 Ch).

The entire set-up be

1. source(DVD)->pre/pro->TAP->AMP?

Would not signal pass thru pre/pro's volume control circuit and hence be 'compromised'? I found that 'analg pass-thru' or 'analog direct' using pre/pro is compromised-I was better off removing it for 2 Ch-hence same would apply for HT.

2. source(DVD)->TAP->AMP will typically suck since DACs used in DVD  
   Players are worse off than pre-pro.

Dunno if I am wrong here...

Cheers,
Kishore

John Chapman

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    • http://www.bentaudio.com
6 channel transformer-based attenuating pre?
« Reply #4 on: 26 Jan 2003, 11:32 pm »
Hello!

Good to see you at CES! I'm sorry for the delayed reply - just got back from a weekend at a local ski hill. Lot's of fun!

There are so many combo's possible I hope I have it right - please set me straight if I don't!

If the goal is to maximize 2 channel audio then either a pre-assembled kit (2 channel) or a TAP system with one 2 channel transformer module would work. The typical hookup would be to run your high res sources (dac, analog front end or sacd/dvd-a) to an input on the unit. Then the movie stuff from the dvd would hookup to a different input as you show in your example #1.

1. source(DVD)->pre/pro->TAP->AMP?

This setup is using the pre-pro for decoding the surround stuff.  Using the DVD ouputs for the front channels direct to the Bent Unit and then using the outputs from the pre/pro for the rears and the rest would be tricky to setup (time delays) and then very hard to keep levels matched after that.
If your player has a decoder built in you could skip the pre/pro and go direct but then you'd need a TAP system with 6 channels to control the level on the other channels.



For movies using the pre-pro's level control has never been a problem for me but I may not be as critical of this as some folks are as I listen to music mostly and kind of change 'gears' when watching movies.

I'm starting to ramble so maybe I'd better let you tell me if I understood the question and let you get me back on track!

Many Thanks!

John Chapman
www.bentaudio.com