Hi Folks !
Some informations about my configuration, Rbias not adjusted yet.
I don't understand what you mean by measuring offset between R1/R6. Where do I check ? I'm a noob !
I've only adjusted RBias value on each board, +/- 950R, before firing up.
R-Core transformer, 30Va 2x15v, Bob ELLIS PSU, gives 13.16v on each rail. No chance to get it hot !
No pot connected, I've got a 10K Alps aside for Diamante but not wired yet. Unbalanced input is coming from AlienDAC, volume is adjusted on Foobar and Windows, using Asio4.
Diamante is feeding a Sennheiser HD-650.
All components are the ones pointed by Mr Majestic in his latest BOM, same values.
But I've soldered the R26 inductor...
C1/C2 are Nichicon Fine Gold 220µF/63v. C5/C6 not stuffed.
It sounds great, no hiss or humm, quiet dead silent.
My HD-650 has never been shacked like this before... hohoho !
Detailed mid an high, not agressive, very good bass section.
Next step : CD player connexion and pot wiring.
I've only listened to flac files, discovering more new details, reveals recording quality :
Kate BUSH : Nocturn / Aerial (bass section, kate's vocal, string guitar)
Cowboy Junkies : Sweet Jane / Trinity Revisited (drums, strings, sliding guitar, voices....)
Muse : Time is running out / Absolution ( synthe intro and effects )
Rory GALLAGHER : a million miles away / Irish Tour 74 (everything)
Just one thing, maybe it could be linked with bias.
Left chanel is more present than the right one, balance adjusting.
Your opinion ?
Some informations about my configuration, Rbias not adjusted yet.
I don't understand what you mean by measuring offset between R1/R6. Where do I check ? I'm a noob !
I've only adjusted RBias value on each board, +/- 950R, before firing up.
R-Core transformer, 30Va 2x15v, Bob ELLIS PSU, gives 13.16v on each rail. No chance to get it hot !
No pot connected, I've got a 10K Alps aside for Diamante but not wired yet. Unbalanced input is coming from AlienDAC, volume is adjusted on Foobar and Windows, using Asio4.
Diamante is feeding a Sennheiser HD-650.
All components are the ones pointed by Mr Majestic in his latest BOM, same values.
But I've soldered the R26 inductor...
C1/C2 are Nichicon Fine Gold 220µF/63v. C5/C6 not stuffed.
It sounds great, no hiss or humm, quiet dead silent.
My HD-650 has never been shacked like this before... hohoho !
Detailed mid an high, not agressive, very good bass section.
Next step : CD player connexion and pot wiring.
I've only listened to flac files, discovering more new details, reveals recording quality :
Kate BUSH : Nocturn / Aerial (bass section, kate's vocal, string guitar)
Cowboy Junkies : Sweet Jane / Trinity Revisited (drums, strings, sliding guitar, voices....)
Muse : Time is running out / Absolution ( synthe intro and effects )
Rory GALLAGHER : a million miles away / Irish Tour 74 (everything)
Just one thing, maybe it could be linked with bias.
Left chanel is more present than the right one, balance adjusting.
Your opinion ?
korben69 said:10K Alps pot (10KAX2) connected.
Listening on an old Denon DCD595, Bliss : Quiet Letters.
No external DAC. More gain.
Left chanel volume seems to be higher than the right one.
No RBias adjust one, waiting for the Noob helper's !
Inverted R/L chanel, listening. (sorry for my poor English)
Its a fantastic little amp
I love it too.The imbalance is most likely due to the bias. Put the DMM probes on each side of the respective resistors and trim the voltage with the trimpot.
BC550C with BC560B?
hey guys,
checking on this thread after a long time, good to see that many people are enjoying the amp...
i had tried to build the amp a few months ago, and had posted my problems, mainly that i could not null the dc offset, and it changed when i changed the volume pot (i was just using a simple 10k volume control at the input, no other preamp circuitry).
i changed the trimpots but that didnt solve the problem, and eventually
i gave up because i didnt have enough time to devote to the project.
now i looked at the boards yesterday and i noticed that i was using bc550c & bc560b transistors, could this be the reason for the problem? i am thinking of re-stuffing the boards so any advice would be really appreciated. a major problem i have is that good quality transistors are not available here in india...
anyway, i hope someone has some ideas,...
thanks for reading and happy listening to your own diamantes...
mymindinside
hey guys,
checking on this thread after a long time, good to see that many people are enjoying the amp...
i had tried to build the amp a few months ago, and had posted my problems, mainly that i could not null the dc offset, and it changed when i changed the volume pot (i was just using a simple 10k volume control at the input, no other preamp circuitry).
i changed the trimpots but that didnt solve the problem, and eventually
i gave up because i didnt have enough time to devote to the project.
now i looked at the boards yesterday and i noticed that i was using bc550c & bc560b transistors, could this be the reason for the problem? i am thinking of re-stuffing the boards so any advice would be really appreciated. a major problem i have is that good quality transistors are not available here in india...
anyway, i hope someone has some ideas,...
thanks for reading and happy listening to your own diamantes...
mymindinside
Re: BC550C with BC560B?
Another option is to use JFET input transistors like SK170, and then you'll have virtually zero input bias currents. IMO JFET sound different from bipolar input, but not many share my view.
I'm no wiz, and you shouldn't take my words for true, but I think this is what happens in amps with high input bias currents like any typical bipolar input amp. You have to match the input pair as perfect as you can. If you use an input cap after the volume pot, I think the bias currents can be balanced to a low DC-offset, and the offset will not change with the volume. I hope one-who-knows-it-all can explain it better.mymindinside said:
Another option is to use JFET input transistors like SK170, and then you'll have virtually zero input bias currents. IMO JFET sound different from bipolar input, but not many share my view.
well guys, i have good news,
the amp is up and running, and it sounds really sweet..
i'm using a cmoy as a preamp and taking the output of that into the diamante...
it sounds really really good, many thanks mr. white
will try and put up pictures in a few days...
thanks everyone, for the help
mymindinside
the amp is up and running, and it sounds really sweet..
i'm using a cmoy as a preamp and taking the output of that into the diamante...
it sounds really really good, many thanks mr. white
will try and put up pictures in a few days...
thanks everyone, for the help
mymindinside
What about the offset problem, have you solved it? I'm quite surprised this hasn't been reported earlier. Even in simulation with perfectly matched transistors/resistors there's DC-offset following the volume. If you measure bipolar input folded cascode monolithic opamps like AD829 or ADA4841 there's 100 mV or more DC-offset. In AD797 there's about 20 mV. What's the best cure for this?
i thought all was well but i was only testing with high efficiency iems (altec lansing im616), when i plugged in regular headphones the sound distorted as the volume was turned up, i measured the dc offset, and it is 5mv up to a point, and if i increase the volume beyond that it increases to +-50mv and changes with the music.....right now my chain is like this ipod line out->cmoy ( with 10k pot at its input, inside the diamante case) ->diamante ->headphones...
this is a bit frustrating because it sounds nice on the iems but i cant turn up the volume beyond a certain point, or use any other headphones...
taking this in context of what nelsonvandal has said, what is the solution?
also, what are other people using to control the volume?is anyone just using a simple pot at the input? what are your results?
thanks guys,
mymindinside
this is a bit frustrating because it sounds nice on the iems but i cant turn up the volume beyond a certain point, or use any other headphones...
taking this in context of what nelsonvandal has said, what is the solution?
also, what are other people using to control the volume?is anyone just using a simple pot at the input? what are your results?
thanks guys,
mymindinside