Carver C1 going through rework

[Mohawk]

Agreed...

 

[TheManSteele]

Should I have said He's no longer with us? He's departed this world? Another pussy that must find the politically correct way for everything. Sorry but I may not be as educated as a man of your stature... Puss

Very professional... Must be a real mojo booster to call names eh? Im sure the site mods love ya

 

[Gepetto]

Looking at the situation, I would be initially inclined to improve the muting circuit behavior if you are getting noise through on power up.

Things like putting a film cap in place of C401 and doubling its size. This will double the delay before coming out of muting and will put a low leakage cap in place of an electrolytic which will ensure that the timing delay performs properly. I'd be inclined to replace Q205 and Q305 with an enhancement mode N channel mosfet like 2N7000. Pins will have to be swizzled as the 2N7000 has a different pinout than the original 2N5458.

How bad is the startup noise through the headphone jacks which has no muting circuit applied? Worse? Same?

 

[Gepetto]

I'd also be inclined to make R258 10 ohms and R268 1.5K which will enhance the attenuation of the muting circuit. Same deal for R358 and R368, 10 and 1.5K respectively. While in there would change R260 and R360 also to 10 ohms.

 

[Gepetto]

Not major changes but may improve your situation. I would work on one channel first to see if it improves your situation. If works, then do the other channel.

 

[jbeckva]

Very professional... Must be a real mojo booster to call names eh? Im sure the site mods love ya

Yep he's like a bull in a china shop when it comes to giving a hoot, but it's dead on as far as always waiting for a preamp to stabilize and especially when it's a direct-coupled input.

That said, however.. Perry stop being a dickhead, please. How's that for "PC"? The "MAA" has spoken, and consider this your only warning.

FFS someone has to be the asshole for "staff" around here.. guess it'll be me so why not.

 

[FredR]

Using this for power sequencing. Definitely needs its own circuit. Will leave it to the power supply gurus as to if the other shit it does is worth a damn.

 

[Mohawk]

Joe,

Thank you for your posts !
I was looking at the C1 this morning and plugged in a set of headphones...

NO thump ....

Thoughts?

M

 

[WOPL Sniffer]

As was pointed out, the thump circuitry is not used in the headphone output. Did you look at the skizmo? Also, Joe gave some things to try (see above a couple posts ago), to help out the FET circuit. I asked a couple days ago if it thumped through the headphones......

 

[Mohawk]

I just got back to test that !
And indeed no thump....
Go figure!

 

[WOPL Sniffer]

I just got back to test that !
And indeed no thump....
Go figure!

And the thump occurs using Main Out 1, AND Main out 2????

 

[Gepetto]

What is the position of the Tone switch, in or out?

 

[Gepetto]

And when does the thump occur, immediately upon powering up the preamp or after the ~6 second delay of the muting circuit?

 

[Mohawk]

Main 1,2 thump the same, no different

Tone switch in / out has no effect...

The thump is consistent at around 6-7 seconds after power up...

M

 

[Gepetto]

Cool, that confirms it is the muting circuit going unmuted.

 

[Gepetto]

have you disabled the muting circuit to see if it goes away?

 

[Gepetto]

One thought since we know it is involved with the muting circuit is to tack a 0.1uF cap from pin 10 to pin 8 of IC8 to see if that slows down the transition to an unmuted state enough to make a difference. Worth a try to see if it affects it.

 

[Mohawk]

Thanks joe !
I'll give that a try and let you know !
M

 

[Gepetto]

0.1uF may make the transition too slow. Probably should start with 0.01uF instead of 0.1uF. If it has an effect, some experimentation may be needed to optimize it.

 

[Mohawk]

Hey joe ...

Here a scope capture of the DC measured on the outputs....
Initial on gets me some DC... After IC 8 switches you see the DC drop...

Thoughts ?

M