Lack of gain?

[Ropie]

Lesson - the biggest electronics mysteries are often down to something very simple.

Yes, and these are usually just as hard to find! Glad to hear it's back to normal - does it sound even better now it's had an 'overhaul'?

 

[Nuuk]

does it sound even better now it's had an 'overhaul'?

I have not put it back into service yet as I want to listen to the OPA627BIGC for a couple of days to better judge the differences between the two.

This is necessary for my degree in Gaincloning!

 

[carlosfm]

Well, I was taking the transformer out for a closer physical examination when I noticed that one of the secondary wires going in to a connecting terminal block was loose.

What terminal block, Nuuk?
I've learned long time ago that there's nothing like solder.

 

[carlosfm]

I have not put it back into service yet as I want to listen to the OPA627BIGC for a couple of days to better judge the differences between the two.

This is necessary for my degree in Gaincloning!

Can we bet?

 

[Nuuk]

What terminal block, Nuuk?

I agree Carlos but when I am putting something together for the first time, I use terminal blocks so that I can easily change things around. Removing them later on and soldering the connections is on the agenda!

 

[carlosfm]

I agree Carlos but when I am putting something together for the first time, I use terminal blocks so that I can easily change things around. Removing them later on and soldering the connections is on the agenda!

Oh...
I though that you had finished that amp long ago.

 

[Nuuk]

I though that you had finished that amp long ago.

Question: 'Is a DIY hi-fi project ever finished?'

 

[Nuuk]

Seems that I spoke to soon.

When I put my VBIGC back in the main system today I found that I still have a lack of gain such that I can run it at full volume and it is not too loud.

I have taken it back to the 'test' room and run it with my test speakers and another CD player but the result is just the same.

I just can't see what would be affecting both channels in exactly the same way as the channel balance is spot on!

BTW - the test speakers are also very efficient and I can't use them with a standard (unbuffered) IGC at full volume!

 

[Ropie]

Just a thought, Nick - is the stepped attenuator wired in correctly?

 

[Nuuk]

Just a thought, Nick - is the stepped attenuator wired in correctly?

In a word - YES

Thank goodness I have a reserve stack of Gainclones in the house

 

[ronc]

Hate to bring up the obvious Nuuk ole bud but have you tested the tube?
ron

 

[sandro600]

ron , how do you test the 6922 tubes?

Nuuk do you still have the Velleman speaker protection circuits in ?

 

[ronc]

Well in my pre GC days i would use a signal generator on input posts and monitor the output with a scope as measured across a resistor.
However since i got knocked out adjusting the bias on my PP 6BQ5 amp i have kinda sorta gotten away from tubes.
ron

Yep, keep your other hand in your pocket around high voltages!!!!!!Its a shocking experience.

 

[Nuuk]

Hate to bring up the obvious Nuuk ole bud but have you tested the tube?

I have not tested them so far Ron as it seemed very improbable that they had both deteriorated by the same amount.

However, anything is possible in this game and I will swap the tubes over (I'm using one per channel but different pins) to see what that does.

One observation I have made is that when powering up, the DC offset indication LED on the protection module (yes they are still there) comes on as before but now stays on for several seconds before going out again.

 

[ronc]

Just an off the head thing, but the DC offset thing sounds like some sort of a CR (cap discharging thru a resistor) response)?Like it has more to discharge?
ron

 

[Nuuk]

I tried swapping the valves over but then I had nothing out of the left channel again! I think there may be a loose connection so will have the valve buffers out of the case and go over them thoroughly.