I am sold
Like my Rev A a lot. I just used a 470 ufd cap because it fit. It works fine. May try bypassing it with a stacked film Siemens cap.
Changing the operating points of the Rev C is the least of my projects. Need to find a low esr cap in 220 ufd 50v that will fit the small pad.
But I learned something new today. May try the series connected nonpolar caps next time a large value cap is needed for signal coupling. Wait a minute, feeddback loop components are signal coupling.
George
Russ White said:
I couldn't agree more. It is one thing to theorize, and quite another to test.
Cheers!
Russ
Like my Rev A a lot. I just used a 470 ufd cap because it fit. It works fine. May try bypassing it with a stacked film Siemens cap.
Changing the operating points of the Rev C is the least of my projects. Need to find a low esr cap in 220 ufd 50v that will fit the small pad.
But I learned something new today. May try the series connected nonpolar caps next time a large value cap is needed for signal coupling. Wait a minute, feeddback loop components are signal coupling.
George
Hi All
i have to admit. (once i have tested it) that I have to withdraw my suggestion of a 1m input and 470uf cap. it boomed like crazy and the output DC shocking were nowhere to acceptable
Mauro optimised this to the best values that would satify most and also the most stable
in the end i settled for a 330uf feedback (might still be to big, but the bass is deeper) and 220k input resitor with a 330pf input cap. now it is to my taste. bit more loose and laidback.
well i still wish i could get the correct vlaues for a NP configuration
cheers
Rudi
i have to admit. (once i have tested it) that I have to withdraw my suggestion of a 1m input and 470uf cap. it boomed like crazy and the output DC shocking were nowhere to acceptable
Mauro optimised this to the best values that would satify most and also the most stable
in the end i settled for a 330uf feedback (might still be to big, but the bass is deeper) and 220k input resitor with a 330pf input cap. now it is to my taste. bit more loose and laidback.
well i still wish i could get the correct vlaues for a NP configuration
cheers
Rudi
Construction finished
Well, I have finally finished it!
I'll have to search what the best method is to test it, but I think the standard practice is to test mv with shorted inputs, and if that checks low, then let her rip?
Piccy for prosterity. I've used medium hookup for the signal cables and 1.25mm enamelled cu wire for the speaker connections.
I was not able to solder any of the fastons, they are just crimped. What do people normally do?
Happy with the result, my only concerns are:
Should I split the signal wiring and twist it?
Should the signal input lengths be the same? (one channel is a lot longer than the other here)
The speaker ground wires are about twice the length of the signal wire. Will that have any effect?
Well, I have finally finished it!
I'll have to search what the best method is to test it, but I think the standard practice is to test mv with shorted inputs, and if that checks low, then let her rip?
Piccy for prosterity. I've used medium hookup for the signal cables and 1.25mm enamelled cu wire for the speaker connections.
I was not able to solder any of the fastons, they are just crimped. What do people normally do?
Happy with the result, my only concerns are:
Should I split the signal wiring and twist it?
Should the signal input lengths be the same? (one channel is a lot longer than the other here)
The speaker ground wires are about twice the length of the signal wire. Will that have any effect?
Attachments
Well that is a very neat layout. One concern is I don't see a fuse on the primaries. Is there one?
As for the ground leads being longer, that is nothing to worry about.
Edit: My suggestion if there is not an integrated fuse in the power receptacle is to replace the two terminal primary strip with a 3 or 4 and put a fuse inline there. You have plenty of room and it would be a simple mod.
But once again, EXCELLENT execution!... Please let us know how you like the sound.
As for the ground leads being longer, that is nothing to worry about.
Edit: My suggestion if there is not an integrated fuse in the power receptacle is to replace the two terminal primary strip with a 3 or 4 and put a fuse inline there. You have plenty of room and it would be a simple mod.
But once again, EXCELLENT execution!... Please let us know how you like the sound.
rabstg said:
Thanks for the feedback
Yes, the primaries are fused - the IEC socket has an integral fuseholder, and there's a 5A Slowblo about to go in. Having interested kids around means I do things like remove the fuse until everything is complete, just in case someone decides to plug it in when I'm not around...
Oh yes, I'll defintely let you know how it sounds
Michael
Burn in
Will not take long. Took mine to another equipment lovers house with about 2 hours run in. He loved it. I am way too biased, most amps that new sound better after spending so many hours building. It takes time to hear the small warts.
This circuit is not sensitive to ground lengths. I have another amp the hums if the ground wires are not exactly the same length. It taught me a lot about layout.
Good luck! Hope you are happy with it.
George
Will not take long. Took mine to another equipment lovers house with about 2 hours run in. He loved it. I am way too biased, most amps that new sound better after spending so many hours building. It takes time to hear the small warts.
This circuit is not sensitive to ground lengths. I have another amp the hums if the ground wires are not exactly the same length. It taught me a lot about layout.
Good luck! Hope you are happy with it.
George
Just found a killer heatsink source.
Contact Rus directly (barrredboss@yahoo.com) and he will cut it to any size you want. I had him cut the 12" piece in half then in half widthwise for 4 pieces to fit the Ref amp perfectly. Ultra cheap pricing.
Heatsink Auction Page
Contact Rus directly (barrredboss@yahoo.com) and he will cut it to any size you want. I had him cut the 12" piece in half then in half widthwise for 4 pieces to fit the Ref amp perfectly. Ultra cheap pricing.
Heatsink Auction Page
Ok, it's running, sounding sweet!
I've been listening for a while at reasonable levels, and the back panel is warm, not hot to touch. Those resistors inside are pretty hot though
Initial impression is that it's slightly drier than the other amp, but not unpleasantly so. I'll let it burn in for a few days before I get critical... It sounds very good to my ears.
It's pretty quiet with no source until the volume gets to about 75%, then there's a bit of hiss. This is with Russ's Freebird in standard configuration, things are quite loud enough at 25-33% on the dial.
I'm getting a bit of hum directly from the tranny (not through the speakers though)
Michael
Pic of the front panels:
I've been listening for a while at reasonable levels, and the back panel is warm, not hot to touch. Those resistors inside are pretty hot though
Initial impression is that it's slightly drier than the other amp, but not unpleasantly so. I'll let it burn in for a few days before I get critical... It sounds very good to my ears.
It's pretty quiet with no source until the volume gets to about 75%, then there's a bit of hiss. This is with Russ's Freebird in standard configuration, things are quite loud enough at 25-33% on the dial.
I'm getting a bit of hum directly from the tranny (not through the speakers though)
Michael
Pic of the front panels:
Attachments
maf_au said:Ok, it's running, sounding sweet!
I've been listening for a while at reasonable levels, and the back panel is warm, not hot to touch. Those resistors inside are pretty hot though
Initial impression is that it's slightly drier than the other amp, but not unpleasantly so. I'll let it burn in for a few days before I get critical... It sounds very good to my ears.
It's pretty quiet with no source until the volume gets to about 75%, then there's a bit of hiss. This is with Russ's Freebird in standard configuration, things are quite loud enough at 25-33% on the dial.
I'm getting a bit of hum directly from the tranny (not through the speakers though)
Michael
Pic of the front panels:
Hi michael,
If the hiss you are hearing increases when you increase the volume then the hiss is most likely coming from your source(CDP prolly) one way to know for sure is to check for hiss with the inputs to the preamp shorted and the volume up.
If you had hiss with nothing connected to the preamp inputs the preamp is likely picking up a little RF/EMI noise. which could be coming from many sources. You could change the RF rejection cap on the FreeBird for a higher value and see if that helps(200pf or 330pf should help) I would not go over 330pf and start at 200pf.
Just for reference sake when I say the input shorted I mean the input and the input ground connected. One easy way to do this is to take an old RCA cable with male ends and cut it so you have 2-3" of cable on the jacks. Then solder the conductors together and you now have a pair a shorting pigtails.
Your offset is just fine, well within limits,
You will notice right away an amp like this is much more revealing than most, which can come off harsh at first if you are used to something more veiled , but it will grow on you.
Great work!Cheers!
Russ
Russ White said:
You will notice right away an amp like this is much more revealing than most, which can come off harsh at first if you are used to something more veiled , but it will grow on you.
Russ you got me thinking here. what equipment are you using?
As a test i did some experiments today. i decided to remove all my "esoteric" stuff. that being DAC - Ribbons. so i was left with Rotel 951 frontend (modified) and singel morel 5" with morel tweeters. (representing the average owned top-end speaker) and a passive preamp. that alone being reasonable hifi equipment,
I then hooked the amp upto the system with my configuration (that being described in a previous post) well the outcome were not as detailed as what i am used to (veiled if you want to describe it as such). then i changed the amp back the original configuration. that was a improvement put still not the detail of my reference system. the soundstage is 2 dimentional and the tops were not as smooth as my ribbons i and were missing hi freq detail. (that is were a super tweeter helps) the high freq were "harsh" compared to my ribbons and class A amps. (but that is just a general impression i have of dome tweeters. you get converted very quickly when you use ribbons, it is just way smoother) it is not the amps fault
so the i think we have to be very carefull as to how we test and compare the sound. if you do not have a dedicated DAC doing duty in your system you are robbing yourself from 40% of the detail, (not all DAC's are good so be carefull even in that department) the average Rotel is veiled compared to say a Marantz which is more forward in the mids, and not all the rotels are the same. some being much better than others and the same with the marantz
this little amp is one of the best designs that i have had in my system and comes highly recommended. I have had better but they cost 300 times the price of this amp. I just think we have to be objective when we give our views and state what equipment is being used when we give our opinions. unfortuneately the average person does not have access to equipment that resolves the sound as it should and it then becomes a case of what might work best in your system. (this amp fitting the bill, and doing a good job of it)
I know my system compare easily with systems in the $ 18 000 (and above) region but not every body listens to that kind of equipment so it becomes difficult to do a comparison and not all the changes or configurations work for everybody.
so guys when you have completed your amp and do a evaluation please state your equipment used. this little amp deserves it
cheers
Rudi
rudi said:
You will only know if you change only the amp.
To test a component you should do it on the system that you know best, the one you listen to everyday, for a long time.
You know it better, and you know how it sounds.
For me, this means my main system. I have other systems, but this is the one I use for a serious test.
Change the amp, and it shows.
Change the preamp, and it shows. The source, etc.
But ony one thing must be tested, if you want to be sure.
For better or for worse.
carlosfm said:
Hi Carlos
you are obviously not getting what i am saying here.
I have already tested the amp and it good. i had to change some values so it does not sound like your ordinary modern day commercial amp and in order to sound a bit sweeter in the mids and less stressed. in my refference system it sounds great but i wanted to know what it sounded like in less expensive and less revealing systems. that is why i took it down to the average system level.
I wanted to know what other people were experiencing when listening to it without the resolution of a DAC and ribbons.
this little amp already prooved itself of being 100X better than the ordinary chipamp inverted or non inverted , and that is the only reason why i would persue the development of this amp, because it sounds like a BIG SS amp not like a good sounding chip
i hope i made myself clear this time.
cheers
Rudi
Sources
Hi All,
I had not previously mentioned my sources because I have tested with quite a few.
I currently have the following immediately available(some other stuff packed up).
1)A Cambridge Audio DAC3.
2)A Denon DVD-2910 (professionally modded with opa627 for outputs).
3)A Denon DVD-3910(modded as the 2910).
4)A newly aquired DVD-5910.
5) For initial bench testing and PC listening I have a USB DAC of my own creation.
6) I also have a Creative Audigy 4 for PC use.
I have listened to my REFs with all of the above.
My favorite source is the DVD-5910 Simply because my collection of SACDs is quickly growing, and that little beauty rocks.
For preamp(in my stereo listening room) I also use my own freebird, as well as some unpublished designs of my own.
I also use as a front end in my HT room where I do some testing a Denon AVR-3805 which has analog 7.1 preouts from any source which is especially nice since you can feed it a DSD signal direct from the 5910. I love it. The Denon products are some of the most widely modded pieces of gear out there, so they make good kit for those of us who like to tinker.
I used to own some tube gear, but I quickly sold it. I don't personally care for it. I like my gear to reveal everything, but not add music of its own. If I wanted to inject harmonics and color I would run my signal through a DSP. Just kidding of course. No offense to the tube dudes.
Cheers!
Russ
Hi All,
I had not previously mentioned my sources because I have tested with quite a few.
I currently have the following immediately available(some other stuff packed up).
1)A Cambridge Audio DAC3.
2)A Denon DVD-2910 (professionally modded with opa627 for outputs).
3)A Denon DVD-3910(modded as the 2910).
4)A newly aquired DVD-5910.
5) For initial bench testing and PC listening I have a USB DAC of my own creation.
6) I also have a Creative Audigy 4 for PC use.
I have listened to my REFs with all of the above.
My favorite source is the DVD-5910
Simply because my collection of SACDs is quickly growing, and that little beauty rocks.For preamp(in my stereo listening room) I also use my own freebird, as well as some unpublished designs of my own.
I also use as a front end in my HT room where I do some testing a Denon AVR-3805 which has analog 7.1 preouts from any source which is especially nice since you can feed it a DSD signal direct from the 5910.
I love it. The Denon products are some of the most widely modded pieces of gear out there, so they make good kit for those of us who like to tinker.I used to own some tube gear, but I quickly sold it. I don't personally care for it. I like my gear to reveal everything, but not add music of its own.
If I wanted to inject harmonics and color I would run my signal through a DSP. Just kidding of course. No offense to the tube dudes.Cheers!
Russ