playdough Posted March 16 Posted March 16 (edited) G’day Have played about with cheap amps from Feebay and others for a while finding the around fifty dollar XH-M180, four channel not that terrible. Have the day cut out here with this 8ch, dual power supply power amp to build up plus all the interconnection cables. Need this operational to move the speaker project forward into baffle testing. Hoping that 8 x 25w will be ok. 2 x 300w power supplies have been proven quiet and surprisingly reliable for continuous use; so confident 8 x RCA, plus a spdif cables terminated like this with a tiny piece of resin inside heat shrink for reliability from shorts and strain relief will be fine. I find a trick to soldering these little devils is to take close up photos and inspect every joint before closing,,,hopefully things get better as you do more. Edited March 18 by playdough 3
mwhouston Posted March 19 Posted March 19 Not mine but (to me) new inspirational design from Woo Audio. Yep, a US$13K HP amp. Just love the retro-modern design.
aussievintage Posted March 20 Posted March 20 (edited) Just posting to say I got around to actually testing this tiny class D board, and it preforms quite adequately. Like last time, running at low voltage (12 volts) into 15 ohms, so power output way less than rated. But good clean mono sound. These little bits of electronics from Aliexpress are turning out to be be very good quality and all working well (so far at least) Edited March 20 by aussievintage 3
playdough Posted March 21 Posted March 21 1 hour ago, aussievintage said: Just posting to say I got around to actually testing this tiny class D board, and it preforms quite adequately. Like last time, running at low voltage (12 volts) into 15 ohms, so power output way less than rated. But good clean mono sound. These little bits of electronics from Aliexpress are turning out to be be very good quality and all working well (so far at least) Hi, yes they are a reasonable little amplifier. They will output a relatively clean low distortion 10w when 20vDC or more is applied. Fairly extraordinary actually when reading over the specifications of the TPA3118 and applying the circuit. 2, 4 ohm loads don't seem to be a problem either although frequency range hits a wall at 20Khz. Operating in dual mono as a stereo, they can provide a detailed soundstage with layering and depth. With lower efficiency speakers (most small cone speakers) they run out of headroom and dynamics because of their low power rating, flattening the soundstage image. There is a more suitable AB Class chip amp in the TDA7850 (good to try) which forms the basis of a vast amount of Car Audio head units world wide, on board 4 channel amps. Personally been surprised the excellent performance of a basic car 4 ch head unit, powering a set of 6.5" coaxials or similar, very low distortion 25w pc at 14.4VDC is much more in the ball park for clean dynamics. The MOS Fet is TDA7850 is more expensive though. I'll let you know how the 8ch 2 x amp build based on these little car head unit chip amps goes. Nearly finished with that, making a chassis ATM. 2
aussievintage Posted March 21 Posted March 21 20 minutes ago, playdough said: Hi, yes they are a reasonable little amplifier. They will output a relatively clean low distortion 10w when 20vDC or more is applied. Fairly extraordinary actually when reading over the specifications of the TPA3118 and applying the circuit. 2, 4 ohm loads don't seem to be a problem either although frequency range hits a wall at 20Khz. Operating in dual mono as a stereo, they can provide a detailed soundstage with layering and depth. With lower efficiency speakers (most small cone speakers) they run out of headroom and dynamics because of their low power rating, flattening the soundstage image. Headroom is not a problem unless you turn it up loud . I am sitting less than metre from a high efficiency 12" speaker anyway Gave him a little plastic box to live in 3
mwhouston Posted March 21 Posted March 21 31 minutes ago, aussievintage said: Headroom is not a problem unless you turn it up loud . I am sitting less than metre from a high efficiency 12" speaker anyway Gave him a little plastic box to live in The amp may not be identifying as male. “It” may be a more correct term to use. 3
mwhouston Posted Monday at 11:02 AM Posted Monday at 11:02 AM Haven’t built one of these for ages;- a Mimic, chip based MM phono stage. Developed by Oddwatt of America and tested to 0.25db deviation from the RIAA curve. Iv’e made ten of these and none the same. Generally enclosure, component or input selection differences. This build is a 99% parts on hand build. I wanted it that way to help use up way too many parts. The enclosure has been around for over 20 years. Like the others it runs on two 9V batteries with PS on board which generates a virtual earth. Based on a genuine OPA2134. Should be finished in the next few days. Thinking on calling it the “Mimic - Classic”. 2
aussievintage Posted Monday at 11:32 AM Posted Monday at 11:32 AM 26 minutes ago, mwhouston said: Haven’t built one of these for ages;- a Mimic, chip based MM phono stage. Developed by Oddwatt of America and tested to 0.25db deviation from the RIAA curve. Iv’e made ten of these and none the same. Generally enclosure, component or input selection differences. This build is a 99% parts on hand build. I wanted it that way to help use up way too many parts. The enclosure has been around for over 20 years. Like the others it runs on two 9V batteries with PS on board which generates a virtual earth. Based on a genuine OPA2134. Should be finished in the next few days. Thinking on calling it the “Mimic - Classic”. The classic op-amp phono preamp just works. Hard to find a point of differentiation between implementations. I have built battery versions too. I even used one as an opportunity to "roll" opamps, and found nothing much to be gained. Ended up with an OP2134 like you. Still got it somewhere. 3
mwhouston Posted Monday at 09:37 PM Posted Monday at 09:37 PM 10 hours ago, aussievintage said: The classic op-amp phono preamp just works. Hard to find a point of differentiation between implementations. I have built battery versions too. I even used one as an opportunity to "roll" opamps, and found nothing much to be gained. Ended up with an OP2134 like you. Still got it somewhere. I have a TT I move around to play vinyl on when I want to listen with HPs. Rather than pull down my main rig this allows me to setup a second temporary listen spot with minimum fuss. Either tube or portable HP amp completes the setup. 1
mwhouston Posted Wednesday at 11:26 AM Posted Wednesday at 11:26 AM (edited) When you have it prewired like this it makes it so easy for the final assembly. It got a little tight getting batteries in but it worked. Flashing top and bottom. The flashing crushes resonance and vibration and adds weight to a very light weight enclosure. If I could count this would have worked at first on but (if you know chips you can pick it) one input was in the wrong spot. Once fixed this baby sung like a Diva. Very standard parts (had 98% on hand) but after a few hours of play this Diva sang like a super star. Very dynamic and clean. The bolt head at the front is for battery health check. I found I had a spare Mimic badge from another build so now it is “Mimic - Pro”. Edited Wednesday at 11:28 AM by mwhouston 2
aussievintage Posted Wednesday at 11:38 AM Posted Wednesday at 11:38 AM 9 minutes ago, mwhouston said: The bolt head at the front is for battery health check. I made mine easy to measure and replace - the battery case is up on top. The phono amp is mono with switchable eq (I may have shown it here before) 3
playdough Posted Wednesday at 09:17 PM Posted Wednesday at 09:17 PM Interesting I run a mimic from a 24v wall wart smps no worries. Just in case anyone wanted to know…….. Nice pre amp with a Burson discrete opa however the stock opa is excellent playdough 2
mwhouston Posted Wednesday at 11:09 PM Posted Wednesday at 11:09 PM 1 hour ago, playdough said: Interesting I run a mimic from a 24v wall wart smps no worries. Just in case anyone wanted to know…….. Nice pre amp with a Burson discrete opa however the stock opa is excellent playdough Can you send an image to remind me which Mimic?
playdough Posted Thursday at 02:27 AM Posted Thursday at 02:27 AM 3 hours ago, mwhouston said: Can you send an image to remind me which Mimic? Sadly no, I’ve moved city and the record player/mimic was left behind. It’s the same cct as yours above except on a screen printed board. Your build in fact. Next time I’m home I’ll get a picture. 8 channel amp going ok although crowded. 2
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