B1 Preamp - Help Me!

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Re: Hear, hear!

Looneytunes said:
Please guys!
But, one thing I have always loved about the Pass Labs forum is its openness, its spirit of cooperation, and its general lack of personal criticism. I think a lot of this comes from Nelson himself. I have seen other posts in other forums, which could be construed as personally insulting, and I have never seen Nelson take the bait. I hope I have the privilege to meet this man one day.

Looney


Couldn't agree more with you. Some of your wishes will be answered if you visit Burning Amp.
We are at D day minus 18.

:)
 
I have a Proposal.

Lets try it Professor Smith's way.

I will volunteer to help troubleshoot over the forum.
And I will answer any questions.
If the Mods could move this to a separate thread, it might be more comfortable for everyone.

My qualifications are 8 years in Manufacturing engineering and 18 years as a support engineer in a Call center troubleshooting over the phone and email. And By the way, I have a BSEE.

I do have a set of suggestions for generic troubleshooting.
Its usually either bad components, bad connection or bad layout.

1. Make several paper copies of the schematic.
Verify every component value visually. Is it marked correctly?
Check it off.

2 Verify Visually that every node (connection) is connected to all expected components. Check for cold solder. Document.

3 Verify all resistors for value with a ohm meter. Understand that some resistors cannot be measured once inserted in a circuit.
Record

4. Record all nodes with a volt meter.

5. Note components that are layout critical. In this circuit, the Gate stopper should be physically close to the FET. Its function is to suppress RF oscillations. a foot of wire would make the component non-existent for that purpose.

Doug
 
DougL said:
I have a Proposal.

Lets try it Professor Smith's way.

I will volunteer to help troubleshoot over the forum.

Well, I've worked in commercial FM radio and production studios, a major manufacturer's Bipolar front end, assembly, test, applications, etc. etc. etc. I've probably troubleshot more than anything else in all of those positions. But, personally speaking, if Doctor Smith wants to treat "Mr Grey" and the rest of us how he has been treating us, he should go dig up $20k dollars and buy whatever he thinks he wants. $$$ can get you anything. even if you are some spoiled "do it my way brat." That's not why we are here...
I hate getting into this caca this way but some people just don't get it :xeye:
 
DougL said:
I have a Proposal.

Lets try it Professor Smith's way.

I will volunteer to help troubleshoot over the forum.
And I will answer any questions.
If the Mods could move this to a separate thread, it might be more comfortable for everyone.

My qualifications are 8 years in Manufacturing engineering and 18 years as a support engineer in a Call center troubleshooting over the phone and email. And By the way, I have a BSEE.

I do have a set of suggestions for generic troubleshooting.
Its usually either bad components, bad connection or bad layout.

1. Make several paper copies of the schematic.
Verify every component value visually. Is it marked correctly?
Check it off.

2 Verify Visually that every node (connection) is connected to all expected components. Check for cold solder. Document.

3 Verify all resistors for value with a ohm meter. Understand that some resistors cannot be measured once inserted in a circuit.
Record

4. Record all nodes with a volt meter.

5. Note components that are layout critical. In this circuit, the Gate stopper should be physically close to the FET. Its function is to suppress RF oscillations. a foot of wire would make the component non-existent for that purpose.

Doug
5.) what is the gate stopper?

do you think my layout using bell wire is causing problems here?
 
Professor smith said:
do you think my layout using bell wire is causing problems here?


No I think your arrogance and ignorance are what is causing the problems here.

I know that is not a polite statement, but in all the time you have been bi_ching you could have torn a part and rebuilt the circuit 5 times.

Just my 2 cents worth.

All-

I apologize for the interruption.
 
5.) what is the gate stopper?
In the B1 Schematic, R102 and R202 are in the circuit only to suppress high frequency oscillations. Usually, this resistor is attached as physically closely as possible to the FET gate to minimize lead inductance and stray capacitance that can cause the circuit to "fly"(ocellate).
do you think my layout using bell wire is causing problems here?
No. Bell Wire is appropriate. I am suggesting that in certain components, "extra" wire can be an inductor that is electrically significant at radio frequencies.
Further, a follower has frequency response into low radio range so that this in not academic.

Doug
 
secondly if I omitted the volume control, would there be any benefit in using the buffer between say a CD player and an amplifier?
Usually, a CD player has a low enough output impedance so there is "no" benefit from a buffer.

The benefit of a buffer is the ability to use a 20k to 50K pot and be able to still drive a 20' cable into a power amp with a 20k input impedance.


HTH

Doug
 
I have a question concerning original Pass B1 schematic. Sorry in advance if such a question has already been answered ...

Mr. Pass has designed this buffer with only one power supply for both channels. What is the reason for not implementing dual-mono PSU ?

Is it not really necessary because of small current consumption (less than 20 mA) or were the costs the main driver behind this decision ? In another words: would dual mono PSU bring something to better sound reproduction of this buffer ? Usually it does ...
 
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