[regal]

I would just trust Jack, read his webpage he is very specific on what info he needs to build a transformer,  get it working and as I said before when you want to get specific with exotics and the like, Bud from Onetics is the go to guy.   Just for reference a popular $5000 tube amp here uses standard Electra-print transformers. With any new design its smart to start with a mid-level transformer until you perfect everything,  then when everything is working as you want on the bench and 100% complete buy the expensive transformers. You can't do it all from textbooks,  too many variables.    JMHO

 

[dBs]

Sorry for the delayed responses. I found out Monday last week at lunch time that I would be working 6pm-6am out in the testing areas for the entire week. Needless to say, the only thing I wanted to do was sleep, lol.
 
Quote:

Hello dBs, I've not read all of the VoltSecond information, but what I did read seems generally fine, so you may have possibly misinterpreted some stuff?
 
Maybe I misunderstand but it seems that in your request to Electra-Print you asked for a transformer capable of handling DC (i.e. 30 mA), however a parallel feed is always going to be capacitor coupled hence free of DC current in the primary. It may be that which confused the E - P guy. It is the DC or no DC situation which defines transformer design parameters in addition to the 'primary impedance, secondary impedance, and output power' as noted by E - P.
 
Having a transformer designed for no DC will result in proportionally higher inductance, all else being equal. So specify no DC, the turns ratio (primary impedance, secondary impedance) and the ouput power required, and then the inductance turns out to be whatever it turns out to be. Then choose your output coupling cap according to the inductance that you have ended up with. 
 
The (no DC) Sowter 8665 is noted as having a resulting primary inductance of 137 H (http://www.sowter.co.uk/headphone-transformer.php) and multiple taps (12, 6, 4 : 1). I doubt that you will find better. Expensive, but worthy of consideration because it does the right job right!
 
 
 

If you look at their site, they lump SE with DC and parafeed under the same category (though they and I both realize that they are not the same and also the reasons they are not the same). Apparently his frustrations were more at finding another site that spreads false information and that such a site is merely simulation and preposterous.
 
I will look into that transformer you recommend there. While most parts I can buy cheaper equivalents early on to keep costs down during prototyping and troubleshooting, transformers is not one of those elements. Transformers are potentially the most important element effecting the sound, so I am willing to put the lions share into those.

 
Quote:

I would just trust Jack, read his webpage he is very specific on what info he needs to build a transformer,  get it working and as I said before when you want to get specific with exotics and the like, Bud from Onetics is the go to guy.   Just for reference a popular $5000 tube amp here uses standard Electra-print transformers. With any new design its smart to start with a mid-level transformer until you perfect everything,  then when everything is working as you want on the bench and 100% complete buy the expensive transformers. You can't do it all from textbooks,  too many variables.    JMHO

Oh I trust him, absolutely. His experience is likely more than that of the web site I linked, furthermore, his experience is in the real world. I definitely trust him. You're absolutely right regarding the parts. I am planning to get cheaper stuff for prototype and troubleshoot. After everything seems optimal at those given parts, then I will start buying the quality stuff.
 
I am onto the power supply design now. I have a lot going on right now so it might be slow going, but I'll get there, I always do =D
 
My question now is how to go about prototyping these things, hahaha. I suspect your average bread board wouldn't handle it well.
 

 

[dBs]

Ugh, I see why most people are content to buy amps instead of make them...even if they have the knowledge to make them! I go to calculate the needed HT or B+ conditions from the power supply...800V. Yea...that is just way too much. Back to the drawing board. Thankfully that upper pentode should work for most any lower triode tube I could want to use so I just will pick a triode with lower current. To that end I will also probably be forced to scrap the idea of the triodes being paralleled. Looking at the oft used 6SN7 and single triode equivalent. Thankfully, with this lovely Excel sheet I've constructed, I only have to pick my desired operating conditions and everything is calculated for me.
 
Very frustrating none the less. Find a solution, walk the path, hit a brick wall. Find a different solution, walk the path, another brick wall...somewhere else this time. Find a different solution, walk the path, brick wall, so close that time too! Lol, very frustrating.

 

[dsavitsk]

You are making this a lot harder than it is.  800v? For headphones?

 

[dBs]

Hahaha, yea exactly. I didn't think these were adding up as much as I thought. Most of the voltages were ok, the problem came when I calculated the drop of the pentodes cathode resistor and the pentodes load resistor. Those dropped a LOT more voltage than I had expected. When you added that voltage into the power supply, it just became the unreasonable 800V. I'm retooling now, we will see what happens.
 
I'm starting to think that it isn't a matter of me making things too difficult now, just that this topology when done all in tubes is genuinely difficult with all the different aspects that are interlinked with one another and have to be within pretty small ranges. It isn't as bad if you design it with a triode as the current source since you don't have the screen to contend with. That screen has caused a lot of the problems I have had unto this point. I wanted a challenge, well I am certainly getting it...even if for any average DIY tube designer this is probably really simple, lol.
 
UPDATE:
Ok, I have a configuration that should work now (as if I haven't said this before, lol). Single 6J5 lower triode operating at 8mA. The pentode operating...bah, I'll just show the pictures. The table on the right is the one I would be enacting. The one on the left is a comparison of what I had before.

 

[dsavitsk]

 
Quote:

Originally Posted by dBs /img/forum/go_quote.gif
the pentodes cathode resistor and the pentodes load resistor.

 
Can you post a schematic? That doesn't make sense ...

 

[dBs]

Like this but with a pentode up top. The resistor that looks like Rl is the RL pentode load resistor. Rk2 is the pentodes cathode resistor. Not my schematic so some things are slightly different, but the important parts are the same.

 

[nikongod]

Stop. Put your pen down. Take 10 deep breaths.
 
Build something. Go out into the world, find something that appeals to you, and build it. Its simple. It could be an OTL, a parafeed amp, a series-feed, or something else. There are tons of PROVEN designs out there, but the important thing is actually building something. Its not as rewarding as designing and building your own thing, but you will gain XP this way.

 

[dBs]

That is exactly what I am doing. Honestly, this is going to happen. When someone tells me I can't do something, that makes me want to do it all the more. It's the CHALLENGE that drives me. If I wanted to do something easy, I would and would be done with it already. If I'm not challenged, I'm bored and my interest wont stick.
 
This is going to happen, even if from this moment onward no one lays another finger to help.
 
Right now, I can't order parts until I actually KNOW what rough values to buy, even a ballpark.
 
There's a bit of experience to be gained building a Lego set amp, namely how to soldier and practice safe high voltage building. Both are very good things, but A) I know how to soldier already, and B) high voltage is high voltage when you usually talk about headphone amps. You might be "lucky" enough to run into a problem in which case you can try to problem solve the solution, but that's mighty tough when the design and the reason for specific parts of the design are a mystery.
 
I thank you for your advice, but I will be moving forward. I'm getting close to doing exactly what you say anyway. The last part the needs to be designed is the PSU. With that completed, it'll time to order anyway.

 

[dBs]

Only a little bit of an update because I've had so much going on. All that is [still] left is the PSU filter. Keep in mind that there are some parts of this that have been glossed over.
 

 

[regal]

You can't design a  DC Heater for DHT's  that that doesn't hum with on Grados yet sounds like AC, to share with our DIY community cause you're a green wet under the ears EE.
 
Motivated now?

 
Seriously your amp is nice not really a new design but has some nice twists.  Have you made sure that the load is proper for balanced  SRPP per Broskies formula in "SRPP Deconstructed" ?
 
 
Quote:

That is exactly what I am doing. Honestly, this is going to happen. When someone tells me I can't do something, that makes me want to do it all the more. It's the CHALLENGE that drives me.

 

[FrankCooter]

First thing you need to do is correct the connections on the rectifier bridge, Second is take the switch out of the power transformer secondary and move it to the primary where it belongs. Add a fuse and a safety ground while you're at it. The power supply you've drawn is not only wrong, it's dangerous.
 
I guess the audio circuit would sort of work, but it's very awkward. Nothing wrong with a 6j5 to start, but you've got a redundant jumble of various output and loading schemes. Back to the drawing board, Think simple, direct, conceptional. And please, keep your computer turned off!

 

[dBs]

Quote:

You can't design a  DC Heater for DHT's  that that doesn't hum with on Grados yet sounds like AC, to share with our DIY community cause you're a green wet under the ears EE.
 
Motivated now?

 
Seriously your amp is nice not really a new design but has some nice twists.  Have you made sure that the load is proper for balanced  SRPP per Broskies formula in "SRPP Deconstructed" ?

Hehehe, I was waiting for someone to do that XD Right now, I don't feel that I (or anyone else based on what I've seen) is exactly sure what the specific problem is associated with the DHT issue. That will take more time than I will be able to muster currently. You've already seen how long this thing has dragged out, lol.
 
I don't recall seeing any actual formulas in the Broskie article. I've read it over a few times, but it was a while ago. I will take another look.


 
Quote:

First thing you need to do is correct the connections on the rectifier bridge, Second is take the switch out of the power transformer secondary and move it to the primary where it belongs. Add a fuse and a safety ground while you're at it. The power supply you've drawn is not only wrong, it's dangerous.
 
I guess the audio circuit would sort of work, but it's very awkward. Nothing wrong with a 6j5 to start, but you've got a redundant jumble of various output and loading schemes. Back to the drawing board, Think simple, direct, conceptional. And please, keep your computer turned off!

The topology is actually very common from what I have seen. Basically any tube amp schematic for a mu-follower looks almost exactly how mine looks. I had hoped that wouldn't be the case, but the combination of factors that I was facing to keep most of the unique elements I had wanted was too great, I had to scrap most of them. If that is too "redundantly jumbled", then so is every other mu-follower created =P At this point, the ONLY thing that is truly unique about this mu-follower versus the dozens of others with almost identical topologies is that I am also incorporating parafeed. You might be able to make the case that the pentode upper tube is adding the complexity that looks odd, but that is still VERY textbook.
 
You are definitely correct, I accidentally swapped the rectifier diode outputs...plus it looked messy that way XD I fixed it and cleaned it up.
 
As far as the elements missing. I had said that some things were omitted on purpose for the sake of ease; essentially they were implied. I figured that having the switch on the secondary would allow the heaters to stay on even with the unit off and thus stave off some of the problems associated with a cold start and solid state PSU. After thinking about it though, you are right, it should be on the primary so the transformer doesn't run the risk of seeing an infinite load or too much energy suddenly getting shoved into the heaters. I have put up a revised version that makes it, hopefully, seem less dangerous.
 
As far as the computer thing; yea, yea, yea, real world > theory, blah, blah, blah. Sorry if I'm frustrated but I've been hearing that since college and over and over in this thread. Consider the dead horse beat please and let us move on. I will get there when I get there, I am not going to rush into the real world until I am ready. Heck, based upon your seeing that my design wasn't safe, you would think that you would be HAPPY that I wasn't rushing headlong into real world, lest I burn my house down =P

 

[beachgeek]

Looking good, I'm re-learning a lot.
 
Thanks for the wonderful experience!

 

[dBs]

Well, thank everyone else. They are the ones imparting the knowledge. I'm merely taking the ego blows so you can take the knowledge XD