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Not strictly DIY but hopefully of interest and something that will help with the burgeoning amount of DIYers either building active speakers from scratch, taking their existing passive speakers active, who have an interest in home cinema, or maybe just want a cheap stereo N-core amplifier. Mods if you think this should go somewhere else please feel free to move it buy DIY seemed like the best place. I'd like to try and gather opinion on the direction and options of a new multi channel amp I am developing based around the latest Hypex Ncore modules. The basic idea revolves around built in flexibility for configuration. I want to build an amp that is primarily for use with active speaker projects but that would be equally at home in any multi-channel situation such as home cinema. The basics of the amp are already set and development has begun but I have a few questions I’d like to ask of those I’ve come to trust here. The amp will be able to be configured when it is ordered with modules of the customer’s choice. Choices would be for between 2 and 8 channels. The modules themselves come in mono and stereo although the stereo modules only share a power supply, and even that is split into two circuits for the most part. Configurations available would be Mono modules 6 x 500W 8x 250W 8 x 125W These could be configured in whatever configuration the user required for their active speaker project, for example. 2 X 500W, 2 x 250W, 2 X 125W There is also what Hypex call the add on tweeter module which is powered by one of the amp modules, that is a 100 W module. Each of those would take the place of one of the modules above reducing the cost and the power requirement, for example, for a pair of 3 way speakers. 4 x 250 W 2x 100 W tweeter modules Or 4 ways 2 x 500 W 4 x 250 W 2 x 100 W Tweeter modules The same configurations could also be duplicated using the stereo channels as well so 6 x 500W would use 3 x 500W stereo modules 8x 250W would use 4 x 500W stereo modules 8 x 125W would use 4 x 500W stereo modules The tweeter modules could still be used as well, again each tweeter module can be powered from one stereo module so for a pair of 3 ways you could use 2 x 250 W stereo module plus 2 x 100 W tweeter modules The configuration could be changed at any point in the future by simply purchasing additional modules through the website and returning the whole amplifier for the boards to be swapped, the internal wiring swapped out and the addition of new connectors to the back panel as needed. This ability to reconfigure is the unique selling point of this product, that the tentative active 2 way builder could become an active 4 way builder using the same box as time and funds allowed. The input to the modules would be via Neutrik Combo plugs which offer balanced connection via either XLR or TRS (Tip Ring Sleeve) ¼” Jack connector or for unbalanced connection via TR (Tip Ring) ¼” Jacks. As the Hypex modules are fully differential amps, a balanced connection scheme needs to be provided, but obviously some Hi-Fi users will be using a single ended source. That said, I’d expect most of the users to be using one of the new wave of DSP crossovers or a multi channel studio interface for PC based systems, both of which mainly offer balanced outputs. I did think long and hard about offering a standard phono connector alongside either and XLR or the combo, but that would have involved adding some sort of switch between the two connectors to tie pins 1 and 3 together for phono use, this would probably have required relays and extra circuitry. Using the combo connector keeps things much simpler as the use of a TR ¼” jack ties 1 and 3 together on connection, this keeps costs and circuit complexity in the signal path down. I’ll offer Phono to TR jack cables on the website (not silly money ones made out of unobtanium though). The amp package will have on board microprocessor control which will offer several advantages, some of which I’ll definitely include, and some of which I’d like to garner opinion on. Definite includes Standby – all the modules can be placed into low power mode, a push switch will we provided on the front panel (maybe two colour, one for standby/error, one for on, what do people think?) Start-up sequencing – While the full load of the incoming mains will not be exceeded by the modules during operation, like most amps there is a large in rush current as the reservoirs are charged, adding multiple modules may blow the incoming fuse. The microprocessor will start the modules up in a given sequence to ensure that doesn’t happen. Heat shut down - If any of the modules experience over heating that amp module will be shut down and error stated by lighting the alternate colour on the front panel switch. DC detection and shut down – If DC is detected on the output of any of the modules, that module would be shut down and error stated by lighting the alternate colour on the front panel switch. Not sure if I should include Clip - I could provide LEDs on the back panel for clip detection per channel or I could make the front button flash the alternative colour when any one of the channels clip, or I could do both. Thoughts? Mute – The amps can be placed into mute mode, I could add a button to the front panel to switch the amp into mute mode, what do folk think about that? I don’t really like to many buttons but it might be handy, although is it much handier than standby? Remote control – Adding to the mute I could add an IR detector so that the amp could be switched to and from mute and into standby, this may negate the need for a mute switch if people thought mute was needed? I wouldn’t supply a remote, Either I could supply the codes or I could make it work with a standard remote like the apple one. I might have to add a remote defeat switch to the back panel to switch this off should it interfere with the operation of other remotes. Making the remote receiver programmable in some way would probably be beyond at least the initial release. Adding any sort of IR would add to the complexity and hence cost. Signal detection – A little nod to Tony (Bemused) here, it might be a nice idea to get the amp to switch into stand-by after say 1 minute of inaction and to switch back out of standby when a signal is detected. Adding this would add to the complexity and hence cost, although this solution wouldn’t be as complex as Tony’s, it would be done via the microprocessor which would already be on board. This seems like a better idea than a 12V trigger but that could be added as well if folk wanted as I know that some with custom cinema installs use this feature. I’d like to keep this as accessible as possible price wise and while the facilities above obviously add cost it’s mainly development costs, the BOM get more expensive as well but relatively speaking the facilities are inexpensive. Case costs are the highest of the costs. Machining a posh looking case will add a lot to the overall cost to the customer although it may broaden the possible customer base. Adding vibration isolation and all the other stuff we don’t do in the DIY room but that they like in the other rooms will obviously add costs as well. Adding an extra button on the front or an IR window may not add a huge amount though. My thoughts about a case are really no more elaborate than the type of case DIYers have been using from Modushop over the years with some customisation and some nicer feet. Thoughts? Price wise, I need to pin a few more things down, some of which I’ve covered here but I’m aiming for about £700 inc VAT for a 2 channel (stereo module) 125W amp, £900 for a 500W version and rising to about £1850 for a 6 channel 500W amplifier. I might be able to get them cheaper once I’ve pinned down the needs and wants. The prices above would include VAT. This product would need to go through some development to come to market and would most likely be crowd funded for the initial development, agency testing and first run which would be at a discount to the prices above. It would be good to hear some thoughts before I move to this stage though. Looking forward to your thoughts. Stefan