Need some help, advice. Research

[Xander8280]

I am looking to apply for a research grant at my university. I read schematics and could draw you a jcm800 2203 schematic by memory if asked!
Long story short I've been slowly starting a 200W stereo amp(kt88 octet).
So, obviously a research application would require a game plan, list of materials, and reason for the research needing to be done.
Obviously becoming an EE doesn't need any tube theory but, with the potential to get some money back from my university to spend parts...that sounds cool.

Open to ideas and advice in general.

Not trying to milk the system, just trying to get into tubes and have some help on campus(there is one faculty member with some tube experience, only one).

I'm thinking an ultra linear or simul class build would be fun and informing.
I want to go the hifi route. individual bias controls for each power tube. I thought that a pair of 6550 and a pair of el34 would be cool to have together. From the phase inverter have a small coupling cap(22nF)for the el34s and a big one(100n) for the 6550s. Running things hot I thought it would give some head room for the EL34 and allow for a singing midrange and the 6550 would have the glassiness and boom needed. Maybe even some KT120's instead. The idea goes on. The research could literally be detailed research on the responce of different tube types with different bias points.

Would pen and paper(measuring wattage output at specific test wave frequencies) be able to do what a spectrometer does?

[trobbins]

Obviously becoming an EE doesn't need any tube theory

That's a bit naive, imho.

There is a nearby thread on ripple related to a Uni project - a large project, with a few public domain reports if you read German.

If you want to do any reasonable project you're going to have to wade in towards the deep end of some particular topic. Do your eyes glaze over when you read books or research reports on topics like noise, thermal performance, stability,.. or are you particularly piqued by some electrical aspects.

Perhaps you can program a DSP and use that for the feedback loop if hi-fi is your interest.

[jazbo8]

I have seen quite a few guitar/hi-fi amp builds presented as senior thesis by EE students in recent years, but they all seemed no more than just kit building reports - IMO those hardly qualify as senior thesis let alone worthy of a grant. I hope you are not gravitating towards that direction...

I hope you will work on something that can shed some new light on the subject (which granted is pretty hard to do given how old the tube technology is) or at least challenge some of the conventional thinking. For example, what is wrong with the ultralinear connection?

[Structo]

When I was in college around 1977 we spent about one day on vacuum tube theory.

After the transistor pretty much took over tube duties, there were still high current/ voltage applications for tubes, such as broadcast radio/ TV or microwave transmitters.

The problem has always been, how much energy is wasted in heat and how do
we conserve that?

Or how to make a high current device that won't melt.

[vibratoking]

If you really are interested in doing something that is either completely new or enlightening, then you need to understand the current state of amp design. I would direct you to Douglas Self's "Audio Power Amplifier Design" and Bob Cordell's "Designing Audio Power Amplifiers". These are great books with lot's of information. It should be easy to cherry pick an area of interest to delve into. You could also easily permute any of the subjects to vacuum tubes if you wish. In either case, you should be aware of the state of amp design before you plunge in without research.

[Phil_S]

On the practical side of this, I imagine an octet/200W build will require some rather hefty transformers. In addition to the high cost factor, there is substantial weight to be dealt with. While it's not out of the question to do this, I suggest you may want to rethink your reasons for an 8 tube, 200W behemoth. Volume-wise, it is only 10% louder than a 100W amp. You'd need 1000W to double the volume of a 100W amp.

For something that will produce some useful empirical data worthy of a university research project, you might do a whole lot better looking at a 30W or 50W amp with 2 power tubes. It will be easier to deal with in general, and I am having difficulty imagining that it will restrict your research in a meaningful way. Save your money for some cool test gear instead!

If this is a research project, then a clearly stated hypothesis is totally appropriate. Do tell us what you are thinking here. You may be surprised at the good input you will receive to help shape your hypothesis.

[Xander8280]

I have seen quite a few guitar/hi-fi amp builds presented as senior thesis by EE students in recent years, but they all seemed no more than just kit building reports - IMO those hardly qualify as senior thesis let alone worthy of a grant. I hope you are not gravitating towards that direction...

I hope you will work on something that can shed some new light on the subject (which granted is pretty hard to do given how old the tube technology is) or at least challenge some of the conventional thinking. For example, what is wrong with the ultralinear connection?

I would like to brew something unique. From the ground up a tube amp that is made for power and versatility. 6CA7, EL34, 6550, and all the KT's eligible to drop in and be biased. I thought a variable resistor(250k) in place of the standard 150k or 220k would be best. I imagine the sweep might be too sensitive and cause trouble in biasing. I thought that having 4 "one size fits all" bias supplies for each output tube one could service it much easier than 1 bias supply trimpot going to 4 tubes with their own bias trimpots after. Trimming one will affect the others no doubt?

Mainly I'd like an amp with a pair of KT120 and a pair of EL34 output tubes. See if this combination has the "clear highs and deep lows" of the KT120 as well as the "famous midrange" or EL34 tubes. Obviously the OT is limit things but, if the research is all done in respect to the same OT I think it will give more than colorful words.

On the practical side of this, I imagine an octet/200W build will require some rather hefty transformers. In addition to the high cost factor, there is substantial weight to be dealt with. While it's not out of the question to do this, I suggest you may want to rethink your reasons for an 8 tube, 200W behemoth. Volume-wise, it is only 10% louder than a 100W amp. You'd need 1000W to double the volume of a 100W amp.

For something that will produce some useful empirical data worthy of a university research project, you might do a whole lot better looking at a 30W or 50W amp with 2 power tubes. It will be easier to deal with in general, and I am having difficulty imagining that it will restrict your research in a meaningful way. Save your money for some cool test gear instead!

If this is a research project, then a clearly stated hypothesis is totally appropriate. Do tell us what you are thinking here. You may be surprised at the good input you will receive to help shape your hypothesis.

Should have been more clear I am putting together a 100W : 100W stereo amp right now for fun. 200W total. Each watt after 100 seems to be fought for tooth and nail(and wallet). I am using a Hammond 1650TA and my chassis should arrive any day now! The chassis is basically a jcm 27" long chassis but with a 9" depth! Stereo JMP basically, two in one.



The research grant I want to apply for would be for a new project and something else.

Allows wanted to use dual gang pots and have a presence control coupled with treble, resonance with bass, and have a 100k Mid pot. It would sound terrible most likely but it would have heavy controls a bass player could dig.

[Xander8280]

If you really are interested in doing something that is either completely new or enlightening, then you need to understand the current state of amp design. I would direct you to Douglas Self's "Audio Power Amplifier Design" and Bob Cordell's "Designing Audio Power Amplifiers". These are great books with lot's of information. It should be easy to cherry pick an area of interest to delve into. You could also easily permute any of the subjects to vacuum tubes if you wish. In either case, you should be aware of the state of amp design before you plunge in without research.

It's about time I bought some more books, thanks!
I've the three Richard Kuehnel books and a handful of others. None of the "design" books I've read have spread out of the basically Fender/Marshall amps.

[roberto]

Seems more a "I can have half of the kit paid by the university" project.
If this is the case, I would go for another project. Why waste our own thesys just for some money for a project about somethin you don't know and you have no time to learn?

If this is not the case, good luck, but I would implement some new technologies into the old one, EG an arduino to autobias the tubes, or to add some compression to the amp controlling the screen current, or a pre-eq to work together with the room analysis and flatten the frequency response, or...

[trobbins]

It seems like you're aim is to want to hear characteristic tonal sounds - maybe you should swing the budget over to speakers and just by a simple class D ss amp.

Are you sure you're doing an EE course , and not an arts or psychology degree?

[tubeswell]

I would like to brew something unique. From the ground up a tube amp that is made for power and versatility. 6CA7, EL34, 6550, and all the KT's eligible to drop in and be biased. I thought a variable resistor(250k) in place of the standard 150k or 220k would be best. I imagine the sweep might be too sensitive and cause trouble in biasing. I thought that having 4 "one size fits all" bias supplies for each output tube one could service it much easier than 1 bias supply trimpot going to 4 tubes with their own bias trimpots after. Trimming one will affect the others no doubt? .

Warning - none of this is 'new'.

[tubeswell]

Why don't to do a thesis on the dynamics of on-line communities for guitar tube amp builders instead?

That way you could work in a lot of arguments and discussion about different circuit ideas, and theories about the operation of components that get argued about, and offer your own debunk suggestions.

or something.

[Phil_S]

I'm not sharing your vision of this "research project" as research. I'm not sure what I'm missing.

I want to suggest a redirection of your interests to something more esoteric. Martin Manning has been posting to a great thread on a tube analyzer he put together that has some really interesting stuff. Maybe you can take that material to a whole new level? That would be a great endeavor. Really, most of those graphs we have to plot load lines and whatnot or just test data on tube conditions is based one what's found in RC-30 or similar documentation that must be 50 years old. Surely we now have the technology to measure much more and do a far better job of it. Having a published manual would be huge! Or maybe you can demonstrate that there are real measurable differences between mustard caps and orange drops that are responsible for audible differences in output.

The guitar amp people will probably love it. The audiophools, maybe not so much, especially when you prove those expensive fancy colored caps aren't worth what they pay for them.