A J Posted November 4, 2013 Posted November 4, 2013 I'm using a borrowed Peter Daniel's Audio Sector LM3875 stereo amp from SteveM (cheers mate!) to power my mid-horn drivers in my active system. Sounds great IMO. I've also enjoyed running modified battery powered Tripath TA2020 chipamps to drive some of my horn channels previously with great results (IMO). What's interesting is this Japanese guy who is a very experienced single-ended tube amp builder (runs single-ended.com site) wrote this page when he tried a modded Tripath amp and says it compares sonically to the likes of his 45 SET amps? http://lagarto-ex-infoseek.jp/tripath-amp.htm That's an impressive PSU !!
Addicted to music Posted November 4, 2013 Posted November 4, 2013 The audiophile feat of things in compact plastic packages is bizarre ... surely all that matters is the performance? Now I'm not sure if these are strictly chip amps but they're pretty close .... I've got an amplifier with an opamp (LME49990) input stage and diamond buffers (LME49610) in parrallel for output and another with a chip amp input stage (LME49830) and lateral mosfets on the output stage. Both with fully regulated PSUs. The LME49830 I've got powered with a SMPS with 65V rails on the input stage and 55V rails on the output stage. It's good for 190W continuous into 8R . The one with the opamp front end is good for ~16W into 8R and has utterly astonishing measurements. These amps were designed by a guy with access to some pretty astonishing measurement gear and there is simply no way there is any objectionable artefact in the amps as long as I construct them properly. Both are designed for best performance with a philosophy of selecting the correct component for the job, not the cheapest component for the job and not the most 'audiophile approved' component. I haven't taken any pics since - http://www.stereo.net.au/forums/index.php?/topic/27524-diy-audio-what-are-you-building/page-25#entry828431 - but it was sort of sitting there for a while (had other things to focus on for a while) till I got them out of the cupboard on the weekend, I'm going to finish off the build over the next week or so ... four fully regulated monoblocks in one chassis The LME 49990/49710 are bloody hard to beat, the other thats possible better are the ADI devices such as the AD 827 or the ADA 4627-1 brz, but these get expensive.
LogicprObe Posted November 4, 2013 Posted November 4, 2013 (edited) LP, Please provide us a link No probs. http://www.frozencpu.com/cat/l2/g8/c125/list/p1/Thermal_Interface-Thermal_Epoxy_Adhesive.html http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm Edited November 4, 2013 by LogicprObe
tuyen Posted November 4, 2013 Posted November 4, 2013 It really just depends on the application that they are used in. Can't expect a relatively weak 20 watt chip amp to drive your power hungry 4ohm speakers. But use them on high efficiency full range drivers, or in an active system to run the mids or tweeters and you will be able to appreciate their low noise/distortion and high level of refinement/resolution. 2
oceangreen17 Posted November 4, 2013 Posted November 4, 2013 (edited) It really just depends on the application that they are used in. That is so true. A few years ago I purchased a built Gainclone amp off ebay on an impulsive whim - I was naively fueled by all the hype that was surrounding them at the time! It sounded a bit lean and recessed when I tried it on my Dynaudio Contour speakers but later it actually sounded quite good on a set of high efficiency Coincident Technology speakers that I replaced the Dyns with. More recently, I tried it again with my Zu Audio Soul Superfly speakers (even greater efficiency than the Coicidents) and it sounded surprisingly good. It took SS & 300 SET amps costing 20-30 x more to sound better! Not bad for $200 amp (see photo below) - I have no idea what chip is used in this build or whether it is even a good implementation - It may even have been built by a SNA member - I brought it about five years ago! Edited November 4, 2013 by oceangreen17 2
ehtcom Posted November 4, 2013 Posted November 4, 2013 Whilst simple from the outside. Internally they still have most of the components used in a discrete amplifier circuit. Below is the simplified schematic for the LM3875 chip.
zog Posted November 4, 2013 Posted November 4, 2013 The one with the opamp front end is good for ~16W into 8R and has utterly astonishing measurements. These amps were designed by a guy with access to some pretty astonishing measurement gear and there is simply no way there is any objectionable artefact in the amps as long as I construct them properly. Both are designed for best performance with a philosophy of selecting the correct component for the job, not the cheapest component for the job and not the most 'audiophile approved' component. These would be the semi mythical DIY audio unicorns known as the LPUHP? I've put my hand up for a pair the possible recent run of these boards, more to set them aside as components for a future, over-engineered iteration of my active system than anything I want to finish now. Have you ever measured the idle power use of them when they are just sitting there quiet? 1
hochopeper Posted November 4, 2013 Posted November 4, 2013 These would be the semi mythical DIY audio unicorns known as the LPUHP? I've put my hand up for a pair the possible recent run of these boards, more to set them aside as components for a future, over-engineered iteration of my active system than anything I want to finish now. Have you ever measured the idle power use of them when they are just sitting there quiet? That's them Had to be quick to get the first run! Was all accounted for within about 24 or 48hours of them being announced. We had to get custom transformers because Owen did the layout in a hurry and missed including an option to wire the PCB mount transformer for 230V mains. We got some made by SumR in Canada that fit pretty nicely on the board in the end. I was paranoid about the heat dissipation in summer here so went a bit overboard but the new layout addresses that completely in a pretty neat way (output buffers underneath so that heatsink can draw heat directly from the PCB which will be far more efficient than taking it through case of the chip as was the standard design in the old PCB design). The new PCB has off board transformers and better regulators for an improvement on really impressive set of performance specs! I haven't checked idle power draw, might see if I can measure it when I'm in the garage tooling around next weekend. I don't think these will see much more than idle power draw when I've got active crossover and they're DC coupled to my B&C DE250 CDs. The new ones shouldn't be too far off, I think Owen said in the next week or so. I think he is considering doing a commercial offering of them too which should be interesting Chris 1
Once was an audiophile Posted November 4, 2013 Posted November 4, 2013 Here's my implementation - the buffer is an X-10D clone with 6DJ8 tubes - all in a 2U jaycar case worth $100 or so, and the additional circuitry on the amp side of the PSU is a fully regulating circuit designed by Teddy Pardo. The other unit is my FrankenPre - basically a 2XSPDIF and 2XAnalogue input remote control preamplifier with a Pass B1 buffer, and TDA1543 dac. Looks a mess inside, but actually sounds great. DSC_9358.jpgDSC_9357.jpgDSC_9356.jpgDSC_9355.jpgDSC_9354.jpg What voltage runs on 6dj8 B+?
Once was an audiophile Posted November 4, 2013 Posted November 4, 2013 It really just depends on the application that they are used in. Can't expect a relatively weak 20 watt chip amp to drive your power hungry 4ohm speakers. But use them on high efficiency full range drivers, or in an active system to run the mids or tweeters and you will be able to appreciate their low noise/distortion and high level of refinement/resolution. I must talk to Duc and see if he is willing to demo his horns with a chip amp.............
Full Range Posted November 4, 2013 Author Posted November 4, 2013 Don't think I have gone quiet I read every post. And every post with new information has me doing more research into the subject As a layperson I am trying not to overthink it
zipstartcanoe Posted November 4, 2013 Posted November 4, 2013 (edited) I have a Patek Integrated and I think it is a fine little amp; clean, detailed and fast, and a perfect match I think for 47 Lab Lens speakers. I've also heard it powering some AV Trios and although the Ongaku which normally powered them was clearly superior, the "chip amp" sounded just fine. Edited November 4, 2013 by zipstartcanoe
Once was an audiophile Posted November 4, 2013 Posted November 4, 2013 Search "gainclone amp" and you will find a million DIY projects over the past 10 years. Even Joe Rasmussen developed a gainclone circuit, with a valve front end. I had a Jlti gainclone with valve front end also modded it was my first taste of tubes (never looked back) Started modding the sucker early in the journey.
tuyen Posted November 4, 2013 Posted November 4, 2013 Hey Mario, didn't Bryan run his previous horn setup from a chip amp when you guys were over there a couple of years ago? I think I also remember also a high powered JungSon amp for the OB woofers.
Newman Posted November 4, 2013 Posted November 4, 2013 Whilst simple from the outside. Internally they still have most of the components used in a discrete amplifier circuit. Below is the simplified schematic for the LM3875 chip. No, they don't actually have those components, as I see it, that's just an equivalent schematic.
tuyen Posted November 4, 2013 Posted November 4, 2013 I must talk to Duc and see if he is willing to demo his horns with a chip amp............. Good luck with that! I couldn't even find a CD player or DAC in his room
hochopeper Posted November 4, 2013 Posted November 4, 2013 (edited) No, they don't actually have those components, as I see it, that's just an equivalent schematic. Not to be pedantic but they actually describe it as a simplified schematic and in general I'm with Earle on this one, those with the idea that because the enclosure is mostly transformer and a board with a 20pin chip on it .... the circuit isn't necessarily any simpler. In the end I don't care much about what circuit is used, the measured performance is what is important to me with electronics. Those chasing a zen audio experience often miss the details that matter IMO Edited November 4, 2013 by hochopeper
tuyen Posted November 4, 2013 Posted November 4, 2013 and for my case, low noise is critical factor. The battery powered TA-2020 amps are dead silent on 110db+ horns. Same with the Audio Sector LM3875. All the valve amps I have tried so far are so noisy, I get hell distracting audible buzz on idle. Can also still hear it while the music is playing. Is it quite challenging to design/build an equivalent low powered valve amp to be as quiet? 2
oceangreen17 Posted November 4, 2013 Posted November 4, 2013 Is it quite challenging to design/build an equivalent low powered valve amp to be as quiet? I seem to keep quoting you tonight tuyen but this is something that I have reflected on as well ! Both my set amps (Audion Silver Night 300B and an odd ball design DIY 300B) are pretty noisy on my 100db speakers - But my chip amp and SS Valvet Class A monos are dead quiet - I can not hear them at all and sometimes check whether they are switched on I have another tube hybrid amp (a Counterpoint SA-20 converted to NP-220) that is frankly embarrassingly noisy - When you switch it off it 'thumps' like the grid has just gone down ... Can some one with far more knowledge than me offer any thoughts or possible solutions?
Newman Posted November 4, 2013 Posted November 4, 2013 No, they don't actually have those components, as I see it, that's just an equivalent schematic. Not to be pedantic but they actually describe it as a simplified schematic The TI data sheet for the LM3875 describes it as, quote, "Equivalent Schematic (Excluding active protection circuitry)". Who do you refer to as 'they'?
Full Range Posted November 4, 2013 Author Posted November 4, 2013 After a bit more research and I find that a few chip amp recipe models out there E.G. Gainclone - Tripath T Amps & Nelson Pass What are the main design differences and does one type trump the others ? I read with interest some posts that use battery powered chip amps What advantage does this give it over direct AC power ?
hochopeper Posted November 4, 2013 Posted November 4, 2013 I had a datasheet for the LME49830 open on my computer so just looked at it, not quite a 'chip amp' but certainly in the same family IMO. It is a mosfet amplifier input stage in a chip. The datasheet describes a similar diagram as "LME49830 Simplified Block Diagram"
Once was an audiophile Posted November 4, 2013 Posted November 4, 2013 Hey Mario, didn't Bryan run his previous horn setup from a chip amp when you guys were over there a couple of years ago? I think I also remember also a high powered JungSon amp for the OB woofers. Yep chip amp was used as his SET amp was not ready later rawl99 returned and heard the horns with the SET amp game over for chip amp,his OB woofers where run by a subwoofer plate amp with a inductor.
tuyen Posted November 4, 2013 Posted November 4, 2013 Yep chip amp was used as his SET amp was not ready later rawl99 returned and heard the horns with the SET amp game over for chip amp,his OB woofers where run by a subwoofer plate amp with a inductor. haha! Then couple months after that, change to OTL amps and panels and so game over for SET amps and horns altogether!
Once was an audiophile Posted November 4, 2013 Posted November 4, 2013 haha! Then couple months after that, change to OTL amps and panels and so game over for SET amps and horns altogether! His horns did things his panels wont but a valve amp will do things a chip amp can only dream about
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