UnixMan said:
(well, as a quick hack test, if you have a regular my_ref you may try powering the LM318 off some batteries, of course with good cap by-pass too... I would be curious to hear your feedback).
I built one a few years back. Used two transformers to power the the output stage, and a pair of SLA batteries to power the LM318. There are multiple bypass caps, large and small value to decouple the opamps.
I posted pics of my four chassis masterwork back then. It worked GREAT, I think the battery supply for the opamp is a big upgrade. Rails ended up being around 13.2 volts.
The SLA batteries used can deliver huge current. I was stripping a wire once and touched the other lead. There was a pop and flash of light. Looked and a chunk of the stainless steel knife blade had been vaporized. 13 VOLTS DC can do impressive things. I would like to see 317/337 REGS melt steel without a whimper.
I originally thought about using battery power for the LM318 in my first Evo. But the fact that the Evo runs the rails at 14 volts, made me think that the discrete regs Mauro used would be better if left alone. Did add a couple small (4.7 ufd) caps close the the LM318's. Never can leave anything alone. Tried a larger value, 22 ufd and got a little low frequency motorboating.
The main weakness of this design is the single LM3886 per channel. Works fine for high efficiency, high impedance speakers. Bass will be soft for more normal speakers. The paralleled LM3886 in the Full Evo seem to be capable of driving almost anything. Drove 15 ohm Lowthers, KEF, Quad 22l2, and several B&W, up to Matrix 801 S2. The My_Ref was running out of juice trying to push the current hungry Brit speakers.
Dxvideo said:
Hello all, first post here (Of many I hope!)
I've been thinking about building this myself. As I live in China atm, parts are cheeeap...
Question. How about sending me the Eagle files and I have them printed here, (quite cheap as well) and of course also print and send to all who are interested?
Postage is quite cheap, I don't know the weight of those PCB's, but everything under 100 grams is 26 yuan. (about 3.7 USD) pretty much world wide in about one week.
Hi all,
I just wanted to say thanks to Mauro, Russ, Brian, and anyone else who helped me make the final push to build a chip amp.
I built a RevC amp a few weeks ago, and I have to say that I'm stunned as to how it performs. Although I've been into HiFi and home theater for many years, I've always used integrated amps. I currently have a Denon AVC-A11SR, and thought that I should at least get a very good sound out of it. That was until I built the RevC amp....
The first thing I noticed was the amount of power that these tiny LM3886 chips produce. The Denon is "rated" at 125W into 6 ohms (20Hz-20KHz), but I now notice how the sound starts to get quite harsh when the volume is cranked up (I was testing with M&K LCR-55 speakers (4 ohm + 80Hz HP), and small Pioneer speakers; not exactly audiophile, so some of the harshness could be down to this).
With the RevC amp though, it played at high volumes but still sounded fantastic. The RevC has just the right amount of "kick" to it without sounding boomy, it is also warm sounding without being muddy.
Other differences are that the RevC is great at dynamics and the attack and sustain of instruments have a very lifelike quality to them. The stereo imaging is excellent and the best I've heard in years.
In other words - I never believed that different amps could make such a huge difference until I tried this kit. I was always of the opinion before that the speakers were the defining factor and that you need to spend a fortune on an amp to notice the differences - well, I have been proven wrong! The difference is like night and day, and you wouldn't need golden ears to notice the change. So, yet another diy builder hooked!
The kit I'm using is a pair of Twisted Pear RevC boards which I bought from a very helpful person in Australia (pretty sure is a diyaudio member, but can't find original e-mail / user name, and I didn't ask permission to post the name). I also found a Nuvotem 25-0-25 toroidal on eB*y.
I recently managed to get hold of an M&K MX350 sub and some M&K S150 speakers (which I've wanted for over ten years) but I haven't got around to trying the RevC amps with them until I can get the amps into a proper case and do some final testing.
I looked for quite some time for a chassis, and I was thinking of buying a basic 2U rack chassis and get the front panel milled by FP Express or someone. In the end, I bought one of the rather nice looking chassis with heatsinks as shown in the attached photo.
I know this is not quite in the DIY spirit, but it would have cost me far more to get a decent chassis and buy heatsinks of that size too. I also plan to eventually build a full 5 / 7-channel amp using this chassis. (including room correction DSP, Buffallo DAC, and PSP TFT in the front of the case - yes / no?
)
Anyway, a quick question - has anyone compared the RevC amps to the Sympatico yet? I like the idea of higher wattage for home theater apps, and from what I've read, Russ said that the symmetrical layout makes for big improvements. Does the Sympatico have similar qualities to the sound that the RevC has?
When my new chassis arrives, I'll try to get some photos of the completed amp posted on the gallery thread. (that's if I ever stop "tweaking" things!)
OzOnE.
I just wanted to say thanks to Mauro, Russ, Brian, and anyone else who helped me make the final push to build a chip amp.
I built a RevC amp a few weeks ago, and I have to say that I'm stunned as to how it performs. Although I've been into HiFi and home theater for many years, I've always used integrated amps. I currently have a Denon AVC-A11SR, and thought that I should at least get a very good sound out of it. That was until I built the RevC amp....
The first thing I noticed was the amount of power that these tiny LM3886 chips produce. The Denon is "rated" at 125W into 6 ohms (20Hz-20KHz), but I now notice how the sound starts to get quite harsh when the volume is cranked up (I was testing with M&K LCR-55 speakers (4 ohm + 80Hz HP), and small Pioneer speakers; not exactly audiophile, so some of the harshness could be down to this).
With the RevC amp though, it played at high volumes but still sounded fantastic. The RevC has just the right amount of "kick" to it without sounding boomy, it is also warm sounding without being muddy.
Other differences are that the RevC is great at dynamics and the attack and sustain of instruments have a very lifelike quality to them. The stereo imaging is excellent and the best I've heard in years.
In other words - I never believed that different amps could make such a huge difference until I tried this kit. I was always of the opinion before that the speakers were the defining factor and that you need to spend a fortune on an amp to notice the differences - well, I have been proven wrong! The difference is like night and day, and you wouldn't need golden ears to notice the change. So, yet another diy builder hooked!
The kit I'm using is a pair of Twisted Pear RevC boards which I bought from a very helpful person in Australia (pretty sure is a diyaudio member, but can't find original e-mail / user name, and I didn't ask permission to post the name). I also found a Nuvotem 25-0-25 toroidal on eB*y.
I recently managed to get hold of an M&K MX350 sub and some M&K S150 speakers (which I've wanted for over ten years) but I haven't got around to trying the RevC amps with them until I can get the amps into a proper case and do some final testing.
I looked for quite some time for a chassis, and I was thinking of buying a basic 2U rack chassis and get the front panel milled by FP Express or someone. In the end, I bought one of the rather nice looking chassis with heatsinks as shown in the attached photo.
I know this is not quite in the DIY spirit, but it would have cost me far more to get a decent chassis and buy heatsinks of that size too. I also plan to eventually build a full 5 / 7-channel amp using this chassis. (including room correction DSP, Buffallo DAC, and PSP TFT in the front of the case - yes / no?
)Anyway, a quick question - has anyone compared the RevC amps to the Sympatico yet? I like the idea of higher wattage for home theater apps, and from what I've read, Russ said that the symmetrical layout makes for big improvements. Does the Sympatico have similar qualities to the sound that the RevC has?
When my new chassis arrives, I'll try to get some photos of the completed amp posted on the gallery thread. (that's if I ever stop "tweaking" things!)
OzOnE.
Attachments
Sympatico
OzOnE,
Sympatico is a unique design.
It not really an apples to apples comparison with Mauro's design.
Sympatico is a fully differential amplifier, which is to say it has differential inputs,outputs, and feedback.
The LM4780 used on the Sympatico acts like a second gain stage for both voltage and current gain.
In the RevC the LM3886 is a current pump in the feedback loop of a single ended opamp. The current pump configuration is a big reason for its unique sound.
Anyway, yes there are some audible differences between the two (I listen too them side by side quite a lot).
1) RevC has a higher noise floor than the Sympatico (RevC still being very very low). So the Sympatico will have a lot more dynamic range. This is mostly because the Sympatico has much better CMRR and PSRR.
2) RevC tends to sound "mellow" or warm especially with low impedance speakers because of it low damping factor. Sympatico retains its brisk crisp presentation into any load I have tested.
3) Sympatico can deliver a lot more peak power, which can help with transients and things like fast attack snare drum hits etc.
4) Sympatico requires no relay. 🙂 This is not really a big deal, but some people did not like that about the RevC. I actually found it to be a great feature as Mauro added DC protection.
5) Sympatico is actually a bit smaller. 🙂
So where do I like to use which?
Well I have some transmission line speakers which I think the low damping factor of the RevC benefits. I use the amp for those speakers all the time.
For my bass reflex and open baffle speakers I tend to prefer the Sympatico (or the older TXO-2) because of the added authority the amp displays.
Anyway those are my 2C since I am the only person who has both amplifiers to test. 🙂 Soon the Sympatico will be available to everyone.
Mauro did a splendid job on the RevC. I never get tired of it.
Simply stated the Sympatico is a completely different breed of amplifier, so in comparing the amplifiers one should expect large differences.
Cheers!
Russ
OzOnE,
Sympatico is a unique design.
It not really an apples to apples comparison with Mauro's design.
Sympatico is a fully differential amplifier, which is to say it has differential inputs,outputs, and feedback.
The LM4780 used on the Sympatico acts like a second gain stage for both voltage and current gain.
In the RevC the LM3886 is a current pump in the feedback loop of a single ended opamp. The current pump configuration is a big reason for its unique sound.
Anyway, yes there are some audible differences between the two (I listen too them side by side quite a lot).
1) RevC has a higher noise floor than the Sympatico (RevC still being very very low). So the Sympatico will have a lot more dynamic range. This is mostly because the Sympatico has much better CMRR and PSRR.
2) RevC tends to sound "mellow" or warm especially with low impedance speakers because of it low damping factor. Sympatico retains its brisk crisp presentation into any load I have tested.
3) Sympatico can deliver a lot more peak power, which can help with transients and things like fast attack snare drum hits etc.
4) Sympatico requires no relay. 🙂 This is not really a big deal, but some people did not like that about the RevC. I actually found it to be a great feature as Mauro added DC protection.
5) Sympatico is actually a bit smaller. 🙂
So where do I like to use which?
Well I have some transmission line speakers which I think the low damping factor of the RevC benefits. I use the amp for those speakers all the time.
For my bass reflex and open baffle speakers I tend to prefer the Sympatico (or the older TXO-2) because of the added authority the amp displays.
Anyway those are my 2C since I am the only person who has both amplifiers to test. 🙂 Soon the Sympatico will be available to everyone.
Mauro did a splendid job on the RevC. I never get tired of it.
Simply stated the Sympatico is a completely different breed of amplifier, so in comparing the amplifiers one should expect large differences.
Cheers!
Russ
Separate PSU for LM318 - please advise
I´m very happy wtith my RevCs for a long time now, but I want to try s.t. new.
When feeding the LM318 with a separate PSU, is it correct just to cut the traces to the power supply pins of the 318 and connect an unbalanced psu? I´m not sure if there would be a grounding issue.
As I have a very good and quiet +/- 12V PSU on shelf, I´m thinking of using this for both the 318s in my double mono amp with the negative portion connected reversely. Is this a good idea?
I´m very happy wtith my RevCs for a long time now, but I want to try s.t. new.
When feeding the LM318 with a separate PSU, is it correct just to cut the traces to the power supply pins of the 318 and connect an unbalanced psu? I´m not sure if there would be a grounding issue.
As I have a very good and quiet +/- 12V PSU on shelf, I´m thinking of using this for both the 318s in my double mono amp with the negative portion connected reversely. Is this a good idea?
Re: Separate PSU for LM318 - please advise
remove R1 and R4,
remove the two zeners ZD1, and ZD2
Connect your negative supply to the R1 pad on the LM318 side of things.
Connect your positive supply to the R4 pad on the LM318 side of things.
Connect your PSU GND at power gnd on the REVC.
That should do it. 🙂
Have fun!
Cheers!
Russ
SmellOfPoo said:
remove R1 and R4,
remove the two zeners ZD1, and ZD2
Connect your negative supply to the R1 pad on the LM318 side of things.
Connect your positive supply to the R4 pad on the LM318 side of things.
Connect your PSU GND at power gnd on the REVC.
That should do it. 🙂
Have fun!
Cheers!
Russ
Hey Russ, 
THAT was a quick reply ... 
I´ll (hopefully) try that tomorrow, here it´s time to go to bed.
Thank you, man!
THAT was a quick reply ... I´ll (hopefully) try that tomorrow, here it´s time to go to bed.
Thank you, man!
(Minutes later, computer turned on again)
😕
o.k. ...
o.k. too ...
Ehm, wouldn´t that give 24 Volts, frying my LM318?
😕
SmellOfPoo said:(Minutes later, computer turned on again)
o.k. ...
o.k. too ...
Ehm, wouldn�t that give 24 Volts, frying my LM318?
Don't forget to connect you +/-12V supply to GND and you will be just fine.
It gives you +/- 12V (which is 24V yes). 🙂 I am not sure why you think it would go poof. 🙂 The LM318 can do up to +/-20V which is 40V across.
Cheers!
Russ
If it does, I think it will go *brzzz* (stink) ... 🙂
Well, I just stumbled across the fact that I would use one balanced PSU for two REvCs. So would I have to connect the PSU´s ground to both RevCs grounds? Otherwise I have no clue how that should work and ... (here it just clicked in my brain) The whole time I thought the LM318 needs an UNbalanced PSU ...🙄 My fault!
Have a good night!
Separate PSU for LM318 - please advise
I think RevC in stock form has splendid price/performance. Mauro planed it this way.
But, as many, I do believe that it deserves better supplies.
I am a fan of the (rather complicated) TeddyReg:
http://www.pinkfishmedia.net/forum/showthread.php?t=36174
I upgraded the LM318 PS recently, using on board 1K + 20v zener. The TeddyReg's outputs +/- 14.2V. The increase in sound quality is very significant. Stock amp is very detailed and "upfront" in my setup. It has a certain hardness. With the upgrade many things improved, especially the hardness is gone, the already good detail in HF improved also, with a softer character. Extremes are more extended. I will next power the LM3886 with 29V from the other regulator from the same author: the PowerReg:
http://www.pinkfishmedia.net/forum/showthread.php?t=39306&highlight=teddyreg
The picks are not so good...I will try to take better ones...
http://picasaweb.google.com/maxlorenz24/TeddyReg/photo#5232858312711161618
So, if you want to take the RevC to the secondary system, think again...
Cheers,
M
I think RevC in stock form has splendid price/performance. Mauro planed it this way.
But, as many, I do believe that it deserves better supplies.
I am a fan of the (rather complicated) TeddyReg:
http://www.pinkfishmedia.net/forum/showthread.php?t=36174
I upgraded the LM318 PS recently, using on board 1K + 20v zener. The TeddyReg's outputs +/- 14.2V. The increase in sound quality is very significant. Stock amp is very detailed and "upfront" in my setup. It has a certain hardness. With the upgrade many things improved, especially the hardness is gone, the already good detail in HF improved also, with a softer character. Extremes are more extended. I will next power the LM3886 with 29V from the other regulator from the same author: the PowerReg:
http://www.pinkfishmedia.net/forum/showthread.php?t=39306&highlight=teddyreg
The picks are not so good...I will try to take better ones...
http://picasaweb.google.com/maxlorenz24/TeddyReg/photo#5232858312711161618
So, if you want to take the RevC to the secondary system, think again...
Cheers,
M
Could someone post the correct part number for the Relay?
I have this from one BOM
RELAY SPDT 10A 24V 1440 OHM COIL
and this from Twisted Pear
24V SPST Silver Contact Relays
and this from another BOM
653-G2RL-24B-DC24
and none of them end up being the same relay.
Hope someone can list the one they used that worked correctly.
Thanks a bunch
Uriah
I have this from one BOM
RELAY SPDT 10A 24V 1440 OHM COIL
and this from Twisted Pear
24V SPST Silver Contact Relays
and this from another BOM
653-G2RL-24B-DC24
and none of them end up being the same relay.
Hope someone can list the one they used that worked correctly.
Thanks a bunch
Uriah
udailey said:
Which circuit board are you using. The original RevA board and the TPA RevC board use different relays.
Hey Uriah, you are becomming a prolific builder... the Rev C was my first completed boxed DIY amp.