WawaWHUT? This is one confusing preamp!

[nbtone]

He figured out how to check in every few days make a post which brings this to the top of the forum. And how to make a new bass amplifier that really is just a preamp.

That's disgusting.

 

[nbtone]

Forgive me for being picky, but the bias scheme shown in the patent application is NOT grid leak bias, in fact it's no different than the vast majority of conventional common cathode voltage amplifiers used in just about every commercial tube preamp in the industry. Tom, do you have information that is different from the published patent info, or is the patent info not accurate? Something isn't right here, somebody doesn't seem to understand what grid leak bias is. With a grid resistor to ground of 1M, it's still conventional from every definition that I know.

How does the output of the preamp drive a conventional power amp? A 500k pot on the output feeding a real world power amp is going to have a very, very odd taper curve in practice, and will have tremendous transfer losses except at 100% (full up). Did you ever run a frequency response plot versus output control position with say a standard 10k load? I think this would be a fascinating and revealing excercise myself... something I would expect in a review. where the results should be pretty interesting from looking at the patent diagram. (hint... HF boost compensation will not track)

I have researched this topic man times, and this circuit has been referred to as using "grid leak bias". Here is a link that I just looked up where it is discussed bogen pa amp grid leak bias - Bing

 

[Woodsbass]

That's disgusting.

I agree, though the government has begun oppressing us in ways that could not have been imagined in the stone ages. It is all because Algeria really has too many "q"s in its name.

 

[BurningSkies]

That's disgusting.

 

[nbtone]

Way out!!!

I agree, though the government has begun oppressing us in ways that could not have been imagined in the stone ages. It is all because Algeria really has too many "q"s in its name.

 

[nbtone]

AND NOW, a word from our sponsors!

 

[cfsporn]

AND NOW, a word from our sponsors!

I've given up trying to understand and resigned myself to enjoying the ride.

 

[Chef]

I DONT KNOW WHATS HAPPENING ANYMORE

 

[xk49w]

... Once, when I was very young I owned a bass amplifier that had a good tonal quality, and now I've figured out how to make a new bass amplifier behave as it should. Any thing else you want to know?

Not really.

 

[BurningSkies]

I DONT KNOW WHATS HAPPENING ANYMORE

Have another.

 

[Chef]

I don't know how you found my ex wife, but really, we're all better off without her involvement.

 

[cfsporn]

I DONT KNOW WHATS HAPPENING ANYMORE

Did you get into the PCP stashed in the capacitors?

 

[agedhorse]

I have researched this topic man times, and this circuit has been referred to as using "grid leak bias". Here is a link that I just looked up where it is discussed bogen pa amp grid leak bias - Bing

I am pretty sure you are misunderstanding the terminology. The CC circuit shown in that input stage without the cathode resistor is no different than one with a cathode resistor other than the amount of local DC feedback that is generated across the resistor. The point of the resistor is to stabilize the operating point and thus where the tube operates along it's loadline(s). A cathode bypass cap can be used (at some expense of linearity) to reduce local AC feedback and increase gain.

There are different interpretations of what grid leak bias really means, possible depending on the type of circuit being used. Probably the most common useage is the shunting of leakage voltage (and a tiny amount of current) through the resistor between grid and ground. This prevents the grid from creeping positive and helps set a defined operating point.

You may have researched this many times, but when researching anything, it's important to understand what is being said and be open to the possibility (likely in this case) that the information that you have received is not accurate.

 

[nbtone]

I am pretty sure you are misunderstanding the terminology. The CC circuit shown in that input stage without the cathode resistor is no different than one with a cathode resistor other than the amount of local DC feedback that is generated across the resistor. The point of the resistor is to stabilize the operating point and thus where the tube operates along it's loadline(s). A cathode bypass cap can be used (at some expense of linearity) to reduce local AC feedback and increase gain.

There are different interpretations of what grid leak bias really means, possible depending on the type of circuit being used. Probably the most common useage is the shunting of leakage voltage (and a tiny amount of current) through the resistor between grid and ground. This prevents the grid from creeping positive and helps set a defined operating point.

You may have researched this many times, but when researching anything, it's important to understand what is being said and be open to the possibility (likely in this case) that the information that you have received is not accurate.

Thank you for clarifying this. Although I have an interest in electronics, I'm by no means an expert on the subject. The first time I ever heard of grid leak bias was when Tom Lees wrote about it in the article that was discussed previously. I learned all that I know about the subject from a radio guy in the Army Rangers. I'm a Berklee alumnus with a major in instrumental performance.

 

[Woodsbass]

Thank you for clarifying this. Although I have an interest in electronics, I'm by no means an expert on the subject. The first time I ever heard of grid leak bias was when Tom Lees wrote about it in the article that was discussed previously. I learned all that I know about the subject from a radio guy in the Army Rangers. I'm a Berklee alumnus with a major in instrumental performance.

Perhaps someone selling an $800 pre-amp should BECOME an expert in electronics?

 

[agedhorse]

Perhaps someone selling an $800 pre-amp should BECOME an expert in electronics?

I suspect that would indeed be helpful, especially when representing the product to experts in electronics

 

[cfsporn]

Perhaps someone selling an $800 pre-amp should BECOME an expert in electronics?

And before challenging people who are experts in electronics?

 

[nbtone]

I told you I had a friend who was one. (an electronics expert) That enough for you? One person can't be anymore than what he or she is made up of. A lot of people pretend to be someone or something that they are not. $800 is not much money these days, anyway. Would you spend $800 for something you can't have, unless you scrounge and build it yourself, which might take months to complete? I know ... just do without and pretend a lot. Go to the studio with your head in the ying yang, so people will think different of you. Guess what, though, come Friday or Saturday when people want to see you in person, you can't give them anything close to what you promise on your recordings! Go figure!

 

[BurningSkies]

I have a whole bunch of friends who are 'electronics experts' one or two have made top notch bass preamps. I don't have to pretend at all.

Lots of hype for a guy who needs others to explain his own design. When people come on a Friday night to see me, they get the exact same tone they hear on the recording.

 

[agedhorse]

Who here's pretending?

If you can't explain your design in solid technical terms, and back up the explanation when there are questions without insulting the rest of us here, then IMO you should learn more about electronics before coming to a forum pretending to be something that you (maybe) are not.

IMO, it's not good form to argue engineering topics with engineers (there are surprisingly many here) without understanding the engineering concepts that are the foundation of engineering discussions.

Just a friendly suggestion.