betocool Posted July 15, 2016 Posted July 15, 2016 I'm guessing the case is connected to the signal ground in this case, @@mwhouston?
mwhouston Posted July 15, 2016 Posted July 15, 2016 I'm guessing the case is connected to the signal ground in this case, @@mwhouston? The battery test piont is from one side of the differential supply and virtual ground. The test piont is not insulated so yes the enclosure is at signal ground potential.
Guest Posted July 15, 2016 Posted July 15, 2016 To whoever gets the new Mimic, you will love it well done. I modded mine to take externally a 24v DC power supply + a Burson Dual Discrete OPA.
mwhouston Posted July 15, 2016 Posted July 15, 2016 To whoever gets the new Mimic, you will love it well done. I modded mine to take externally a 24v DC power supply + a Burson Dual Discrete OPA. Thanks for the nice comment. Evidently still using yours.
Guest Posted July 15, 2016 Posted July 15, 2016 Thanks for the nice comment. Evidently still using yours. Yes, a small system has spouted from a spare TT, the Mimic and some other bits and pieces, Buying in some Red Spade Audio HE2 speakers from the Mainland. Looking for a nice valve amp to drive them with. Out of interest also have found and using SMPS to drive the Mimic with really good results.
mwhouston Posted July 15, 2016 Posted July 15, 2016 Yes, a small system has spouted from a spare TT, the Mimic and some other bits and pieces, Buying in some Red Spade Audio HE2 speakers from the Mainland. Looking for a nice valve amp to drive them with. Out of interest also have found and using SMPS to drive the Mimic with really good results. Funny you mention small valve amp, I have a Decware inspired EL84 SE UL ready to go. Compact and not too heavy. PM if interested.
mwhouston Posted July 15, 2016 Posted July 15, 2016 http://retro-thermionic.blogspot.com.au/2015/11/el84-se-ul-power-amp-with-attenuator.html
mwhouston Posted July 16, 2016 Posted July 16, 2016 Here is an easy and effective way to handle gain and loading differences in preamps etc. A 4P4T switch, switch down MC load and MC gain, switch up, MM load and MM gain. If you try this solder the wire which attatches to the cct. brd. first. Once the resistors are on getting to the centre pin is hard. The beauty is with the cct. I'm following this clustered resistors only have to reference signal earth so the free ends can be bound together and connected to ground. 1
Guest Posted July 16, 2016 Posted July 16, 2016 Panels are finished and the big job is on to move the stereo so as these can cover and be sealed from the whole rear wall.
mwhouston Posted July 16, 2016 Posted July 16, 2016 Here is an easy and effective way to handle gain and loading differences in preamps etc. A 4P4T switch, switch down MC load and MC gain, switch up, MM load and MM gain. If you try this solder the wire which attatches to the cct. brd. first. Once the resistors are on getting to the centre pin is hard. The beauty is with the cct. I'm following this clustered resistors only have to reference signal earth so the free ends can be bound together and connected to ground. Newman, I have respect for you.
mwhouston Posted July 22, 2016 Posted July 22, 2016 Starting to resemble something now. A butter churn?
Hippy Posted July 22, 2016 Posted July 22, 2016 A butter churn? Naaa Im seeing a Jules Verne submarine. 1
Silent Screamer Posted July 24, 2016 Posted July 24, 2016 Starting to resemble something now. Love it, but what the heck is it?
betocool Posted July 26, 2016 Posted July 26, 2016 Here's something a bit different. An STM32F2 microcontroller, can run up to 120 MHz. It sports a nifty 12.288 MHz oscillator to generate exact 96KHz. The two 5x2 pin headers at the bottom can be used for DAC and ADC chips, using I2S outputs. Powered with 12V DC or less (say... 5v?), and if you wish you have access to all microcontroller pins/functions on the pin headers each side, each pin mapped one to one. It's a very simplified version of my original microcontroller test board, I only wanted to separate the I2S interfaces to try out different ADCs or DACs. The single row pin headers are just ground. I was always missing somewhere to plug the scope probe! At the moment the board is programmed to blink lights (a bit overkill for that), but I just got the controller about 2 days ago. Oh, and it's generating I2S signals! Although where they go... nobody knows. I'm still finishing the design of a DAC and an ADC based on TI's PCMs chips, so will be nice to see when they start working all together. Cheers, Alberto 3
Guest Posted July 26, 2016 Posted July 26, 2016 (edited) Nice work there @@betocool clever stuff Happy to be enjoying the completed bass traps here, a bit more hammer and nail type job. Horn rig is undergoing an evolution into full PC DSP, which will be posted as the parts turn up and I start head scratching. 2 more Holton Amps to build as well, pick those up on this weekend.============> Edited July 26, 2016 by Guest
mwhouston Posted July 26, 2016 Posted July 26, 2016 This is the first week for 9 weeks I haven't had a commission job. All my work over that time, except two jobs, were all from SNA members. Thanks guys. BUT a new (and new version) T4 Class D module arrived last week which needs an enclosure etc. Well as fate would have it I have a 1U 19" rack mount enclosure complete with PS ready to go. This is from a chip amp which didn't perform as well as I hoped. The one short coming is the PS will only produce 36V DC where the T4 likes 42V to produce full power. On my calcs. I should get nearly 150W from the T4 when assembled. More than enough and the fact I will have a 150W amp in a 1U (1" high) encsloure gets me all excited. All that power in a slim line enclosure. I have a 1U high preamp and another a DAC, this could be the start of the high power slim lines! Stay tuned.
betocool Posted July 27, 2016 Posted July 27, 2016 @@mwhouston, Mark, what do you mean "from a chip amp which didn't perform as well as I hoped"?
mwhouston Posted July 27, 2016 Posted July 27, 2016 @@mwhouston, Mark, what do you mean "from a chip amp which didn't perform as well as I hoped"? I built a chip amp - LM3875 - and two caps and two resistors. But I mounted the chips on $300 of solid copper plate. Two 24V tarnnies feed the chips. But it has the deep oscillation going on inside?? Works better from external PS but that's not what I wanted.
betocool Posted July 27, 2016 Posted July 27, 2016 I built a chip amp - LM3875 - and two caps and two resistors. But I mounted the chips on $300 of solid copper plate. Two 24V tarnnies feed the chips. But it has the deep oscillation going on inside?? Works better from external PS but that's not what I wanted. Weird, but not unheard of. I've had excellent results with the LM3886 in a guitar amp. I have still some boards left I will use for a 4x 50W amp, since I got hold of a 36V 500W or so transformer a while back... that should do more than enough. Here's how the board looks. I have quite a few left unpopulated, PM me if you'd like to try and I'll send you a couple. I can give you all schematics and a heads up on a small mistake I made on the layout! 1
mwhouston Posted July 27, 2016 Posted July 27, 2016 Weird, but not unheard of. I've had excellent results with the LM3886 in a guitar amp. I have still some boards left I will use for a 4x 50W amp, since I got hold of a 36V 500W or so transformer a while back... that should do more than enough. Here's how the board looks. IMG_20160727_105014.jpg I have quite a few left unpopulated, PM me if you'd like to try and I'll send you a couple. I can give you all schematics and a heads up on a small mistake I made on the layout! 50W or 200W?
betocool Posted July 27, 2016 Posted July 27, 2016 50W or 200W? Ha ha! Each board uses a single LM3886, which can deliver 50W @8Ohm, +-35V, or 68W max @4Ohm, +-28V (according to the datasheet). You can get two boards from me, each will do 50W, if that is enough for you. I tested it before using it in my guitar amp, and it doesn't oscillate or anything. I did put and inductor and a big resistor on the output as per datasheet, but you could bypass them with a wire. The 200 W will be made of 4x 50W board each I really don't need any more... yet. 1
mwhouston Posted July 27, 2016 Posted July 27, 2016 One of the best chip amps I ever made, which got snapped up on the first addition, was a minimalist chip amp. In this case two resistors are intertwined on the chip legs. That was the whole cct. Still going after thousands of hours of play. 1
betocool Posted July 27, 2016 Posted July 27, 2016 Those chip amps ain't too bad at all I think, give them a good power supply and follow the basic rules, and off they go. The Gainclone name comes actually from the Gaincard, and so far I remember people were stunned by the sound (and the price tag, 3000$ or so for a chip that retails for 5$). It took the DIY community by storm. 1
mwhouston Posted July 27, 2016 Posted July 27, 2016 Those chip amps ain't too bad at all I think, give them a good power supply and follow the basic rules, and off they go. The Gainclone name comes actually from the Gaincard, and so far I remember people were stunned by the sound (and the price tag, 3000$ or so for a chip that retails for 5$). It took the DIY community by storm. Yes built a number of gainclones and sold a number. Two I know of are still in service after years. I even built Gainclone monoblocks which a friend bought and called his Holographic Sound Machine. It produced the most tightly focused imaging I had ever heard.
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