2*100 watt @ 4ohm TK2050 or LM3886 Gain Clone?? - Page 6 - diyAudio
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Old 24th April 2010, 07:25 AM   #51
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But you would want to use an audio taper pot rather than a linear taper pot for a volume control.
Here is why, http://www.angelfire.com/electronic/...mp-Volume.html
. jer
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Old 24th April 2010, 07:36 AM   #52
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Also you would want to use an audio taper pot instead of a linear taper pot for a volume control.
Here is why,http://www.angelfire.com/electronic/...mp-Volume.html . jer
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Old 24th April 2010, 07:38 AM   #53
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oh there's the post I couldn't find(he he he).jer
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Old 24th April 2010, 07:55 AM   #54
infinia is offline infinia  United States
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Most commercial LOG pots are really not that accurate and tracking is almost always bad. So better to buy a good linear one that tracks better and modify it with the amplifiers input impedance. see ESP - A Better Volume Control
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Old 24th April 2010, 08:07 AM   #55
fr1s is offline fr1s  Canada
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Quote:
Originally Posted by geraldfryjr View Post
I don't think that you are going hear any difference in sound quality as they are resistors and don't have any recactive qualities or components involved,but i'm sure someone will probably want to argue over that one. jer
haha ok.
thx for help jer

I actually have stereo 100k audio Taper sitting in my locker in school so I might use that
got it when I was building my headphone amp
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Last edited by fr1s; 24th April 2010 at 08:22 AM.
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Old 24th April 2010, 11:00 AM   #56
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Quote:
Originally Posted by sendler View Post
Based on listening, the TK2050 amps sound MUCH more powerful than the specs. Explosive dynamics like I have never heard from any of my AB amps.
I would love to see the circuit diagram and powersupply schematic and speaker specs of the two setups you used to compare. If you could be so kind please?
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Old 24th April 2010, 04:50 PM   #57
sendler is offline sendler  United States
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Default Power supply and 3886 vs others

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Originally Posted by tangmonster View Post
I would love to see the circuit diagram and powersupply schematic and speaker specs of the two setups you used to compare. If you could be so kind please?
Part of the advantage that I hear with the TK2050 amp may come from the switch mode power supply that I am using. The MeanWell S-350-36 turned down to 32v.
.
36V DC 9.7A 349.2W Regulated Switching Power Supply - eBay (item 160296854927 end time Apr-28-10 23:25:50 PDT)
.
If I ever built with the 3886 again I would definitely use two of these rather than a linear supply. The cost is not that much more than a linear supply at the give away price they are being offered, and the sound is much better. More open and faster. When I first got the Sure 2X100, I hooked it up to one leg of my big dual mono active filtered linear supply that I had been using for all of my AB amps. Dual 24-0-24 150va transformers, Schotky diodes though I later switched to MUR860 in my 8 channels of TDA7250 amps as they sound a little smoother. 220uf of smoothing precedes the Linear Tech voltage regulators which drop 4v down to 29v rails. I added these as a last step and the active regulation does take away a slight edge from the sound. You should try it. This feeds 40,000 uf of Panasonic filter caps, bypassed with stacked film. I had Pi filter series coils in my supplies but comparative listening revealed that there was no advantage and the slight resistance was in fact vaguely rounding the leading edge of kick drum so I jumped them. Don't bother with Pi filters. They are a good way of wasting most of the upstream cap. Heavy wire, star ground, to the amps. I have used the same power supply to evaluate all of my amps over the last 12 years. In order of preference: TDA7250, Hypex, BA100 with two 3875, 3886, AKSA, Velleman modules with TIPs, TDA7294(terrible), along with a few commercial amps such as the Arcam Delta290( my previous to DIY workhorse) and the Behringer A500(terrible). I didn't need the TK2050 to show me that the single 3886 was not the best sounding amp. The bridged/ balanced 3875 is still installed in the photo. They sound way better than a single 3886 if you have a true balanced dac chip such as the direct out modified AK4395 I run as my source in the DEQ2496. I would recommend BPA200 as the minimum if you want to use the 3886 and would probably also recommend the 3875 over the 3886. The 3886 sounds a little remote and uninvolving on it's own. It sounds like there is just not enough power or class A bias current flowing from one chip.
My speakers have been the same and still sound very revealing. DIY Usher two-ways with foil coils and foil bypass on the caps. Air foil or Nordost speaker wires. 1701a interconnects and digital cables. Volex power cords. Everything has been tried and compared and tweaked for 15 years of DIY. Isn't the internet amazing. We live in a golden age. I could fill a book with all of the different components I have listened to including opamps(don't have any in my system path any more. Not that I hate them) caps and resistors, cables, room tuning, source and volume control topology. If you have a revealing system, everything matters. Many stubbornly held myths have been shattered. Surface mount resistors sound way better than through hole. Hard drive out through a firewire sounds better than my best cd transport. And the latest, Switch mode power supplies and class D sound way better than linear and class AB. If you are willing to run a wide open output filter, the Sure 2X100 is in a whole other league of transparency and speed. I was almost ready to order a run of boards for a TDA7250 amp and actually have chips and heat sinks, when I tried the 2X100 on a whim because of the low price. $60 per channel with a huge, 9 amp supply and you can wire it up and have it playing in 10 minutes with all of the connectors on the board. Finally all of my electronics are set and I can begin work on a pc cross 4 way speaker. My current signal chain is:
Hardrive
firewire cable
M-Audio Firewire 410
Belden 1701a spdif cable
Behringer SRC2496 for upsampling to 24/88
1701a aes/ebu cable
Direct out modified Behringer DEQ2496 with the dac chip swapped to AK4395 for EQ and dac.
8 foot 1701a analog interconnects
4k shunt type stepped attenuators for quiet listening or no attenuators with digital volume control for serious listening. ( the TK2050 chip set can run at very low gains with full stability so the system gain is good for me right out of the box at 16V/V to run digital volume control at -3db for loud listening with no attenuators.)
Modified Sure 2X100
8 foot foil/air 12ga. speaker cables
Murphy Usher two-way speakers. 6ohm average?
Highly treated 16x14x8.5 foot room
Attached Images
File Type: jpg BridgedBalanced 3875 comp.jpg (152.3 KB, 421 views)
File Type: jpg TDA7250 comp.jpg (149.7 KB, 413 views)
File Type: jpg ZalmanZM-NB47Jcomp.jpg (152.0 KB, 410 views)
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Old 24th April 2010, 11:29 PM   #58
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I have it in my close future plans to get a shure module and test it a bit.

just as a side note.

Sorry if I am misunderstanding.
But when you say BA100 do you mean BR100. like in 2 modules in bridge mode? that is what i understnd from images. not 100% sure what you mean with bridge/balanced

BR 100 - lm3886 - should only be used into 6ohm load when using +-24 DC powersupply else chips are overdriven. they both effectively see 3 ohm loads

BR 100 - lm3875 should not be used in loads lower than 16 ohms with supply +- 35V
might be fine for slightly lower load (12ohms) resistance with your +-29V supply but nothing CLOSE to 6ohms.

lm3875 is limited to a MAXIMUM of 5 amp.
For BR100 lm3875 using a 6 ohm (average) load each lm3875 will effectively drive into 3 ohm loads which is NOT adviseable for best THD and longevity. BAsically they would be permanently very close to SPIKE current and temperature protection even at lower volumes.

Please note page 4 for voltage and load table for parralel and bridge modes using lm3886.

http://www.national.com/an/AN/AN-1192.pdf
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Old 25th April 2010, 12:14 AM   #59
sendler is offline sendler  United States
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Default Ba, br

Quote:
Originally Posted by tangmonster View Post
I have it in my close future plans to get a shure module and test it a bit.

just as a side note.

Sorry if I am misunderstanding.
But when you say BA100 do you mean BR100. like in 2 modules in bridge mode? that is what i understnd from images. not 100% sure what you mean with bridge/balanced

BR 100 - lm3886 - should only be used into 6ohm load when using +-24 DC powersupply else chips are overdriven. they both effectively see 3 ohm loads

BR 100 - lm3875 should not be used in loads lower than 16 ohms with supply +- 35V
might be fine for slightly lower load (12ohms) resistance with your +-29V supply but nothing CLOSE to 6ohms.

lm3875 is limited to a MAXIMUM of 5 amp.
For BR100 lm3875 using a 6 ohm (average) load each lm3875 will effectively drive into 3 ohm loads which is NOT adviseable for best THD and longevity. BAsically they would be permanently very close to SPIKE current and temperature protection even at lower volumes.

Please note page 4 for voltage and load table for parralel and bridge modes using lm3886.

http://www.national.com/an/AN/AN-1192.pdf
BA= bridge amp, as in BPA with out the P. I didn't bother with the two parallel chips as this was just a test. Built point to point. BR? what ever you call it. Just a quick test circuit to try them bridged since I have a balanced source so no need to create the balanced signal with a diff amp or DRV134. A successful test. Two chips sounds way better than one. Four will be better than two. That's why I am recommending at least BPA200 with a balanced source for the 3886/3875. I never told anyone to build BR100.
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Old 25th April 2010, 12:27 AM   #60
fr1s is offline fr1s  Canada
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Quote:
Originally Posted by sendler View Post
BA= bridge amp, as in BPA with out the P. I didn't bother with the two parallel chips as this was just a test. Built point to point. BR? what ever you call it. Just a quick test circuit to try them bridged since I have a balanced source so no need to create the balanced signal with a diff amp or DRV134. A successful test. Two chips sounds way better than one. Four will be better than two. That's why I am recommending at least BPA200 with a balanced source for the 3886/3875. I never told anyone to build BR100.
question, how do i bridge lm3886 amps??
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