Tube Circuit recipe?? Philosophy????

[Learner]

Hi guys,
Got a few prototype circuit made up and just mix matching them for some listening test, pretty happy with the result and the noise level.

Just wondering if you guys can share some thoughts in the art of mix and match circuit blocks to modularise the gain?

I have tried to connect them in series just to find that the coupling resistor between stages not only kills the noise but as well as the gain, its a compromise which the gain seems to loose out and ended up with attenuation of the signal at the optimal low(<30mV) noise level with small overall gain. So I have now ended up wiring them all in parallel, can anyone direct some info on cooking up a receipe for tube amps? Or is it all trial and error, find one that you like the sound best???

Hey Dr Jackel and Analag, this one is for you! I know I got a lot of catching up to do..... :green:

Total circuit running at 5.32mA

Ahmhmm....... source of day dreaming, I mean inspiration....

Gotta go back and clear the desk now, to prepare for the exam on 68HC11 and JBUG11 tomorrow :roll:

Would rather get a test on tubes.

 

[analag]

I design with a structure in mind. I consider how many gain blocks, phase, topology, triodes or pentodes or both or hybrid. But only after I know what I'm making e.g. mic pre, compressor, eq the list could go on.
If you're experimenting go for it. Your interest is approaching scientific, maybe I'll be learning from you down the road. But really, study the basics use your ears (to hear what's coming out of it) your eyes (to read the instruments) your nostrils (to smell what's burning) it might skip the burning stage and just blow up, but what the hell.

Don't stop.

Analag

 

[kiira]

[quote author="Learner"]Hi guys,


I have tried to connect them in series just to find that the coupling resistor between stages not only kills the noise but as well as the gain, its a compromise which the gain seems to loose out and ended up with attenuation of the signal at the optimal low(<30mV) noise level with small overall gain. So I have now ended up wiring them all in parallel, can anyone direct some info on cooking up a receipe for tube amps? Or is it all trial and error, find one that you like the sound best???
[/quote]

I don't understand what you're doing learner. Are you building tube gain stages and connecting them in parallel? I don't think that would ever be very useful at all. :?

The way I design stuff, what little I've done is after deciding what I want the amp to do I choose a tube and get the tube data on it, draw a load line and choose an operating point, choose the circuit I want to build and then do the maths part to get the component values etc. I have a 3U case with 2 G10 boards each with four sockets on them and a generic arrangement of turrets. I build circuits on them as needed and take them apart because the turrets are really nice for redoing things.

Kiira

 

[Learner]

[quote author="analag"]I design with a structure in mind. I consider how many gain blocks, phase, topology, triodes or pentodes or both or hybrid. But only after I know what I'm making e.g. mic pre, compressor, eq the list could go on. [/quote]

Yes, I can understand why that is the case and I assume that's the most common approach. That's the method I have tried to attempt originally, however it did not work out for me simply because I do not posses enough results of the actual behaviour of each tube under different biasing conditions(eg. current output based on the optimum bias point for my PSU voltage) to be able to make a reasonable prediction.

If you're experimenting go for it.

Experiment is a must, it is absolutely essential as the foundation to understand the behaviour of each device. Theory is derived from results of repeated experiments, however theory does not include every single variable and factors that exists in the real world condition which contributes to the outcome.

That's why I need to do these experiments in order to accumulate sufficient amount of data before I can actually understand the device properly, in order to be able to make good use of each device in a specific application.

Since my 6SK7 tube biasing lesson, I have encountered the same situation with every tube there after. Where my optimum bias current point is no where near the data sheet suggested figure. In fact it is more like a fraction of what the suggested figure on the data sheet, varies from 1/5 to as much as 1/15 in the case of 12A6. My bias point is close to 2mA, whereas the suggested point is 30mA! :shock:

I know that does not sound quite right but that is the result I get, I have gone through every single load line range between 1meg and 10 ohms based on 250V supplied voltage. May be its because I did not incorporate any negative grid bias voltage and only use 1K cathod resistor for all my circuits, I have yet to get a good result from applying negative voltage on the grid. It just seems to kill my input signal.......I will get back to it tonight and re test it all again, just to make sure.

 

[Learner]

[quote author="kiira"]

I don't understand what you're doing learner. Are you building tube gain stages and connecting them in parallel? I don't think that would ever be very useful at all. :?

Kiira[/quote]

Do you mind to share some thoughts on why you think that parallel gain stages is not useful?

 

[ToobieSnack]

wow
i have to say i am jealous of your kickass lil lab area :shock::grin:
nice setup ... :thumb: complete with a dedicated studio montoring system too :grin: lol

any way good luck
keep up the cool work ... even if it is experimental ...

later
ts

 

[analag]

Hey Toobie can you build with only a multimeter, soldering iron, long nose and cutting pliers. Now that's when it's fun.

Analag

 

[ToobieSnack]

well i have an ocilloscope and a signal generator and and even an antique tube ocilloscope that is reall cool
but i have no place to set al this up and so I AM using only my dmm and hand tools for now,, :sad:

that what make me so jealous ... wahhhhh hehe
i'm coming to your house to diy hehe :grin:

hey are you on a mac?
which sim proggy are you using?
i dl;d macspice but i'm not sure how to get it to work....

anyone using macspice? or any other mac sim?

later
ts