or Connect
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › A Very Compact Hybrid Amp
New Posts  All Forums:Forum Nav:

A Very Compact Hybrid Amp - Page 74

post #1096 of 2213
Quote:
Originally Posted by adamus View Post
moderator, can you forgive me swearing.....

thank the F#####ng lord.

all sorted. finally i tracked it down to a grounded opamp pin that should not have been grounded.

its now making good music, but there is a fair bit of ground hum, particularly when i am near the vol knob.

big thanks to holland and alex for the persistence

do people find the 24v reg runs pretty hot?
you're welcome, adamus. Might I ask, how did it get grounded? I take it you mean a servo opamp pin?

Yes, the 24v reg runs hot. It's not horribly hot, though. I would say on the hotter side of warm.
post #1097 of 2213
and congrats on getting it working. Way to persevere!
post #1098 of 2213
not out of the woods yet.....

anyone identify this noise?
LL
post #1099 of 2213
adamus - If you can hear the noise/hum it's not likely coming from the SM heater circuit because it runs @ 150khz (unless your hearing is REALLY good

I think it is not uncommon in CTHs that, depending on various factors incl the tube used, a very faint 50hz/60hz may be audible with very efficient cans.... Between songs or when no signal is present.

If its more than that, I'd look at grounding (incl pot grounding) and would consider boxing it up & getting it away from all the nasty signals roaming around the bench.

P.S. Even though we incorp a ripple filter in the SM heater circuit, it is possible that some insignificant amount of ripple is still present in the heater supply. During prototyping, I couldn't tell battery-powered heater from this SM implementation, so think this should not be a factor. I bring this up because you should report the frequency & magnitude of that wave you are showing to assure its the audible-range one that you are hearing.
post #1100 of 2213
ok, just switched to the senns (650's), hum is reduced but still there slightly (very quiet).
post #1101 of 2213
Quote:
Originally Posted by cfcubed View Post
I think it is not uncommon in CTHs that, depending on various factors incl the tube used, a very faint 50hz/60hz may be audible with very efficient cans.... Between songs or when no signal is present.

If its more than that, I'd look at grounding (incl pot grounding) and would consider boxing it up & getting it away from all the nasty signals roaming around the bench.
Speaking of this, is there any way to bring down this noise? With full size cans I don't hear it, but with iem's I do, and with my better, more sensitive pair (Sleek SA6) it's loud enough to be distracting. It does vary some from tube to tube. I should note that this is with r18's at 150ohms and plastic end panels, so no grounding issues there.

I am loathe to mess with this now that it is working well, and the amp is perfectly enjoyable with all of my headphones save the SA6. I would though like to be able to listen to them in bed with this, but that may be out of reach.
post #1102 of 2213
Thread Starter 
Noise/hum would either be grounding issues or bad Q3P/Q4P. Is the noise in both channels?
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #1103 of 2213
yes, but slightly stronger in the left, only very slightly.
post #1104 of 2213
I hope you get it perfect because it's a phenomenal little amp, it's nicely above the Starving Student right now.
post #1105 of 2213
Quote:
Originally Posted by smeggy View Post
I hope you get it perfect because it's a phenomenal little amp, it's nicely above the Starving Student right now.
wait till you get the Semens ECC82 Smeggy..a whole new level.. Got an Amperex 6DJ8 in mine right now while I work on the EHHA..fantastic!
post #1106 of 2213
tomorrow i will try grounding the pot, it gets much worse if i touch the pot...

i think the 8416 will be extremely hard to beat in this amp. even with the very slight hum, the 8416 is sounding superb.

its a superb little amp and i must let it burn in but currently the bijou is in another league.

I have now moved the bijou into the bedroom where is can be heard with no noise from the fiance! The CTH is now the amp next to the computer for evening listening when i am working etc. my desk now seems huge!
post #1107 of 2213
Quote:
Originally Posted by sachu View Post
wait till you get the Semens ECC82 Smeggy..a whole new level.. Got an Amperex 6DJ8 in mine right now while I work on the EHHA..fantastic!
Sweet, are the Siemens in yet?
post #1108 of 2213
My noise is in both channels, but the balance as well as total quantity depends on which tube is used. Some tubes are much noisier on one side than the other.

I certainly don't hear anything with HD650s though.
post #1109 of 2213
The ECC82 is working out for you?
post #1110 of 2213
Quote:
Originally Posted by olblueyez View Post
The ECC82 is working out for you?
Can't wait for it..expecting it any day now..I have a bunch of other tubes to tide me over for the moment though.
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › A Very Compact Hybrid Amp