LM318+LM3886 MyRef amp completed

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quadtech
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#1 erstellt: 14. Apr 2009, 15:00

Folks,

I completed the MyRef RevC amp, for which there
was a recent group PCB buy on diyaudio.
It is a "composite" amp - LM318 driving an LM3886.

The chassis has a spartan, industrial look, and everything is made easy to remove. Got chassis and toroid locally
in Hyderabad.

I mounted the PCBs on a "mezzanine" card made from
an electrical switchboard sheet. The shaft coupler
is the brass insert from a 60A electrical connector.
Both items are from a local electrical shop.

The front bushing for the shaft was scavenged from a
cheap rotary switch.
The power switch contacts have 1KV rated caps across them.
No turn-on or turn-off thump at all, and the amp is dead quiet. DC offset is like 5mV.
The amp sounds quite fine to me.

Some things like the cheesy LED holder and the knob will
be replaced once I have better ones. I may also
build a small input relay board to switch between
3 sets of RCA inputs.

The build pics are here -

http://picasaweb.google.com/prasadb/MauroMyRefRevC#

Thanks for looking
Prasad

[Beitrag von quadtech am 14. Apr 2009, 15:01 bearbeitet]

Savyasaachi
Inventar

#2 erstellt: 14. Apr 2009, 16:58

very neat build.congratulations...The important question is, how does it sound?

Soundsgreat
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#3 erstellt: 14. Apr 2009, 17:10

Hi,

Prasad congrats on a fine build

!! Looks really good !!

As Sachi has asked please elaborate on the sound please

!

Also is this GB still up ?? if so please post the links !

Finally please do post the cost of the entire project so that we can also think of making one for ourselves

!!

Regards.

quadtech
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#4 erstellt: 14. Apr 2009, 18:31

The group buy is over, but the guy who ran it,
Peter Schroeder, might still have a few PCBs.

A single sided PCB pdf is also available for download,
if you want to try toner transfer. AFAIK, there are
no exotic components on the board, so should be easy to
buy the parts, esp in Blr or Mumbai.

The chipamp definitely sounds very good and I am quite
pleased with it.
If you really push me to make a choice, the KT77 tube
amp I built earlier is a bit warmer and easier on
my ears.

Here is the cost breakup -

Pair of PCBs with parts - $65
24-0-24, 300 VA toroid - Rs 1500
Chassis made by a sheet metal shop - Rs 700
6mm aluminium rod for extension shaft - Rs 25
60Amp elect connector for the shaft coupler - Rs 35

Heatsinks - I had a piece with me which I cut in two - I
think I paid Rs 100 for it a while back. I may replace
with a better ones later.

I already had a lot of misc hardware (binding posts, RCAs, nuts, spacers, wires etc), but I'd estimate that to
be Rs 500 or so.

Prasad

Soundsgreat
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#5 erstellt: 15. Apr 2009, 09:16

Hi,

Prasad thanks a lot for the info

!! where can I download the PDF ?? are there no gerber files to download ?

The total price is approx 10K,which I think is not at all bad !! so I think will like to give it a try

!!

when you say the tube was warmer (offcourse its well known for that kinda sound ) does that mean the Chip Amp sounded forward or bright ?? Also buddy can you tell me bit more bout it ? has the Amp had sufficient Burn-in ?? coz that is what mainly dictates the final sound !!

Also please do share what related electronics and speakers you are using ??

Regards.

quadtech
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#6 erstellt: 17. Apr 2009, 20:03

Sreekanth,

This design was posted by Mauro Penasa in the chipamps
forum on diyaudio -

http://www.diyaudio.com/forums/forumdisplay.php?forumid=40

The original thread on this amp has the subject
"My "audiophile" LM3886 approach"

The questions from the recent group buy was discussed
under the subject "The new "My Ref" Rev C thread"

The schematics, pcb layout were posted around here (see a few posts before this one too) -

http://www.diyaudio....=1666231#post1666231

I am reluctant to be too specific about the sound of
this amp for multiple reasons - I am using
cheap test speakers, my source is an cheap old
dvd player as a source, and I am not blessed with
"audiophile" ears. The amp has not had any burn-in yet,
perhaps a total of a couple of hours.

Here's the obligatory Chinese rip-off -

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120313336134

Prasad

[Beitrag von quadtech am 17. Apr 2009, 20:07 bearbeitet]

Soundsgreat
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#7 erstellt: 18. Apr 2009, 08:06

Hi,

Prasad thanks once again for all the info

! will take a look at it !

How did you get my name ?? PM'ed someone here

I am reluctant to be too specific about the sound of
this amp for multiple reasons - I am using
cheap test speakers, my source is an cheap old
dvd player as a source, and I am not blessed with
"audiophile" ears. The amp has not had any burn-in yet,
perhaps a total of a couple of hours.

Ok no worries, I thought so myself regarding the burn-in so only mentioned it in my last post !

If you later (after duly burning it) decide to pen a sentence or two bout the sound it'll be interesting to read