It interests me, how's that done? How they reduce noise?
I'm breadboarding the new linestage on my preamp, and I fear that noise will be great, even if I use only 7x gain.
Btw, the schematic on the other burnedfingers' thread (Akido) seems to me like a current sourced grounded cathode stage cascaded into a current sourced cathode follower. Everyone seems to rave about its sound... but this way you'll get BIG gain, or am I wrong? So why noise would be an issue in my 7x gain preamp? The Akido looks like 20 or 30x gain...
I'm breadboarding the new linestage on my preamp, and I fear that noise will be great, even if I use only 7x gain.
Btw, the schematic on the other burnedfingers' thread (Akido) seems to me like a current sourced grounded cathode stage cascaded into a current sourced cathode follower. Everyone seems to rave about its sound... but this way you'll get BIG gain, or am I wrong? So why noise would be an issue in my 7x gain preamp? The Akido looks like 20 or 30x gain...
So... how does it sounds? Very good, extremely lively!!!! .
Schematics attached.
But... I have big problems. BIG, VERY BIG noise in the line stage, even with the volume down to zero (thus grounding the input). It's like an hissing, but very wide in frequency range (think white or pink noise). Could be the heater to catode voltage? It's over the limit now, 155V... I will try to elevate filaments.
Also, the ECC82 makes a very noticeable sound when tapped, in fact the line stage (with a gain of 10/15dB) is FAR MORE NOISIER than the phono stage (with a gain of 50dB), both in hiss and microphonics!!! That's incredibile!!!!
Let's try this heater trick... also it's possible that I got a bad tube, since the only one ECC82 that I have is salvaged from an old amp, and that's a Siemens silver-plate ECC82. Will an ECC81 or 83 "work" in the circuit just to see if it's the tube defective or the whole circuit? Just to hear if the noise increases or decreases... I know their mu is higher, so I'll hear more noise anyway...
And it can be that I'm using old salvaged resistor for the plate ones in the voltage amp stage. They're 10K since I don't have a 12K 1W in my parts bin...
Some help?
Schematics attached.
But... I have big problems. BIG, VERY BIG noise in the line stage, even with the volume down to zero (thus grounding the input). It's like an hissing, but very wide in frequency range (think white or pink noise). Could be the heater to catode voltage? It's over the limit now, 155V... I will try to elevate filaments.
Also, the ECC82 makes a very noticeable sound when tapped, in fact the line stage (with a gain of 10/15dB) is FAR MORE NOISIER than the phono stage (with a gain of 50dB), both in hiss and microphonics!!! That's incredibile!!!!
Let's try this heater trick... also it's possible that I got a bad tube, since the only one ECC82 that I have is salvaged from an old amp, and that's a Siemens silver-plate ECC82. Will an ECC81 or 83 "work" in the circuit just to see if it's the tube defective or the whole circuit? Just to hear if the noise increases or decreases... I know their mu is higher, so I'll hear more noise anyway...
And it can be that I'm using old salvaged resistor for the plate ones in the voltage amp stage. They're 10K since I don't have a 12K 1W in my parts bin...
Some help?
Attachments
In fact, I do not want this Joe!
But, under suggestions of some italian fellows on another board, I've revised the schematic (attached), and now I'm getting much lower noise and have lost some gain. I just changed the plate and cathode resistors (I can't understand why I'm getting lower gain with higher plate resistor
).
I also added an elevated reference for the heaters, about 50V. This cured some noise.
Now I've got 3 problems:
- my only ECC82 is very noisy. It's also fairly microphonic. Must replace.
- the preamp is making really weird sounds until the tubes start to conduct at turn-on: I guess I need to delay the B+. Maybe I'll go with a simple solution, 2 switch to activate the B+ and heaters separately.
- I'm hearing some high-pitched whistle, but I'm not sure (it's really high, almost a whine). You know when you're sitting too near the TV set and you hear that kind of noise? That's it... Maybe oscillation? I haven't that damned scope yet... (sorry for the bad words but I can't go without a scope!!!!).
But, under suggestions of some italian fellows on another board, I've revised the schematic (attached), and now I'm getting much lower noise and have lost some gain. I just changed the plate and cathode resistors (I can't understand why I'm getting lower gain with higher plate resistor
). I also added an elevated reference for the heaters, about 50V. This cured some noise.
Now I've got 3 problems:
- my only ECC82 is very noisy. It's also fairly microphonic. Must replace.
- the preamp is making really weird sounds until the tubes start to conduct at turn-on: I guess I need to delay the B+. Maybe I'll go with a simple solution, 2 switch to activate the B+ and heaters separately.
- I'm hearing some high-pitched whistle, but I'm not sure (it's really high, almost a whine). You know when you're sitting too near the TV set and you hear that kind of noise? That's it... Maybe oscillation? I haven't that damned scope yet... (sorry for the bad words but I can't go without a scope!!!!).
Attachments
Hello Chris!
Well, for that old and wise 10MHz scope I've waited almost 5 months now. A fellow in an Italian forum (thanks Paolo!) promised me (September) to sent an used gathering dust scope for free, it came home about in November. It didn't work, it had not an horizontal line at startup, but a single point (dead horizontal deflection I guessed). Did you remember? I took a look inside, identified some bad components but you clevery said that I was going to fry myself there so I took it to a local repairman. He might not be the first one in scopes, but he has a big experience in TV sets, and they have many things in common.
If I remember well he said he got it to work only on a bench supply, so the power supply was the problem...
He said "come next week" once, twice, etc etc... then there were holidays...
One of these days (after the exam) would you come with me at his shop? Just to speed up things
Btw, I've collected so many scope accessories... 60MHz probes (4 of them! HP! They look very expensive...), other no-name probes, probes with clip leads...
I'm so bored of this scope thing
By the way the 0D3 that burnedfinger sent me has arrived this morning
Well, for that old and wise 10MHz scope I've waited almost 5 months now. A fellow in an Italian forum (thanks Paolo!) promised me (September) to sent an used gathering dust scope for free, it came home about in November. It didn't work, it had not an horizontal line at startup, but a single point (dead horizontal deflection I guessed). Did you remember? I took a look inside, identified some bad components but you clevery said that I was going to fry myself there
so I took it to a local repairman. He might not be the first one in scopes, but he has a big experience in TV sets, and they have many things in common. If I remember well he said he got it to work only on a bench supply, so the power supply was the problem...
He said "come next week" once, twice, etc etc... then there were holidays...
One of these days (after the exam) would you come with me at his shop? Just to speed up things
Btw, I've collected so many scope accessories... 60MHz probes (4 of them! HP! They look very expensive...), other no-name probes, probes with clip leads...
I'm so bored of this scope thing
By the way the 0D3 that burnedfinger sent me has arrived this morning
Hi poobah,
What a puzzle indeed! It just isn't fair at all. Although I think Gene is going to fire his scope up tonight.
Giaime,
Round trip ticket. Let me stay at your place and I'll fix the darn thing! BTW, nice probes! Treat them well and they will treat you well.
Oh, forgot to ask. Keep in mind I'm Canadian.... is it warm there?
-Chris
What a puzzle indeed! It just isn't fair at all. Although I think Gene is going to fire his scope up tonight.
Giaime,
Round trip ticket. Let me stay at your place and I'll fix the darn thing! BTW, nice probes! Treat them well and they will treat you well.
Oh, forgot to ask. Keep in mind I'm Canadian.... is it warm there?
-Chris
Giaime said:Ah, by the way... could someone explain me what's the fuzz here with Akido Linestage? What are its goals, could someone explain me very briefly its characteristics?
Maybe it would be suitable to my needs... I can't find the original thread. I'm sure it will use hard to find tubes
You'll find everything you'd ever want to know about the Aikido on John Broskie's site, www.tubecad.com. Basically, it's a clever scheme to reduce noise induced by the power supply- it does not reduce the tubes' noise.
Giaime,
I was thinking maybe some old rich guy here would donate a working o'scope for a student. Then we could start a "Help poor Giaime thread" to arrange for the shipping expense.
I would not make such an effort for a student of Literature, Poetry, Politics, Law, Accounting etc...
How 'bout it guys??? who's got a WORKING starter scope for a poor college kid???
I'll bet Planet_10 has 40 or 50 scopes he's forgotten about...
I was thinking maybe some old rich guy here would donate a working o'scope for a student. Then we could start a "Help poor Giaime thread" to arrange for the shipping expense.
I would not make such an effort for a student of Literature, Poetry, Politics, Law, Accounting etc...
How 'bout it guys??? who's got a WORKING starter scope for a poor college kid???
I'll bet Planet_10 has 40 or 50 scopes he's forgotten about...
Yes, we have seen his pile!
I have a tube scope, not restored yet though. Of course that would frustrate poor Giaime to no end. Trigger, what's trigger? There is however, a phase control. Giaime, you don't want to know. It may only be 500 KHz vertical bandwith. That and your probes will not fit. It uses binding posts! (bet SY already figured that out! ).
-Chris
I have a tube scope, not restored yet though. Of course that would frustrate poor Giaime to no end. Trigger, what's trigger? There is however, a phase control. Giaime, you don't want to know. It may only be 500 KHz vertical bandwith. That and your probes will not fit. It uses binding posts! (bet SY already figured that out!
).-Chris
Chris,
You're talkin' collector stuff here... cost $500 in air freight. Keep that for your man-cave so you can display lissajous figures when you're old... sorry , I meant older, like SY.
We just need a B & K... or "Wave-Right"... "See-More"... "Hakalugi".
Who can donate a starter (student) scope
You're talkin' collector stuff here... cost $500 in air freight. Keep that for your man-cave so you can display lissajous figures when you're old... sorry , I meant older, like SY.
We just need a B & K... or "Wave-Right"... "See-More"... "Hakalugi".
Who can donate a starter (student) scope
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