Intact Audio

With the original spacings ( 0.025"), the nickel chokes did sound harder than the amorphous chokes. Even after finding the sweet spot for all three, the amorphous chokes were smoother. I wonder if the nickel chokes with the narrow spacings were saturating during peaks in the music? i really do...

Not to open a can of worms, but I used PJ's input from this link: http://db.audioasylum.com/cgi/m.mpl?forum=bottlehead&n=90071 PJ's ROT's are up there with the best... i see how the 10K tames the resonant hump (see attached images) luckily your inductance (if you have it stacked 1X1 is around 1...

Maybe I have something wrong. I figured that by going to the 5ar4, I now need more resistance above the plates (plate load?). your VR tubes are setting the B+ and decoupling each stage, so any resistance "above" them shouldn't change things. by all means go for the 5AR4 then use the extra...

Hi Dave, Grant Gassman, Steve Kaufman, and I got together at my place last Saturday to listen to the chokes you sent me. We used them in the driver stage of my amp. The choke loads a Telefunken RS241. The plate of the RS241 drives a second order filter ( a series cap and a parallel autoformer.) The...

hey len, i shrunk the jpegs and added a full res pdf for those that want to print... hope you don't mind... the horizontal scroll is a pain and i'm on dialup at home :-( All in all, the pre is working but with a few problems. Firstly, upon replacing out the last 380 uF electrolytic cap in the HT PS ...

here are two series of measurements of restel's first revision. stacked 1X1 i measure 40hy's of inductance. DCR of each winding is around 70 ohms. i am really surprised that the 1:2 worked as smoothly as it does given the bifilar wind. (I am also equally surprised that the phase inverting hookup mak...

I also take my wire off the top of the spool and then pass it through a felt guide and a wheel. I also have to hold it between thumb and fingers to better tension it. the fingers are the key part, they will feel the kinks The bonded bifilar wire that I bought isn't neatly layed on the reel, it's tw...

Dave Cigna said that the outputs are differential. If that is the case, Kevin Carter explained to me that it could be wired up with the + and - leads wired up to opposite ends of the primaries of the transformer, with the center leads of the primaries wired to ground. ahhh...now the light goes on.....

I just bought some bifilar wire 0.1 mm with the intention of winding a 1:1 interstage for 6 ma. This is the first time I've tried anything bifilar. Bifilar wire (two individual wires bonded together) can be very tricky. read the bits about keeping constant tension. for your use, i suspect too much ...

Thanks Dave! It seems that you did all these measurements on the bench. Did you load the secondary with your no gap autoformers? It would seem important to provide the same load. no i did not, i am working through an easy way to quickly measure a lot of different situations. i would only expect the...

so put up some pictures of your system and give us something to talk about...


dave

Based on the roughly 10 ohm output impedance, is a 1K/1K transformer the most ideal? 1K is such an arbitrary number in this situation. I'll put a lot of faith into what allen suggested... and it just happens that i think i can get 6hy's (1K @ 20hz)pretty easily with a butt gap for a first attempt. ...

so we are back to the trifilar transformer... and 1K is a breeze. I just happen to have some trifilar #33 wire with no real use

actually I think the quad 36 litz i have would do better, just parallel the appropriate wires for the secondary.

dave

The $200 autoformers would be a nice start

read through the FAQ and associated links, then searching the various other forums will give you more background and theory.

dave

maybe a known choke in series with the resistors might also help the situation??? measurements at two different frequencies should allow someone to extrapolate the Z-out. I have been meaning to ask, what is the frequency of that 1V signal, and what meter are you using to measure it? just curious. dave

what is the cause of the actual problem here??? if, as allen suggested the squealing was a loading issue and not a coupling one, you have been barking up the wrong tree with how the primaries couple to each other. i understand the (possible) need for some sort of filter, but have we determined the n...

we don't know how they sound yet... when i said by the weekend, i didn't specify which weekend. :-) i got around to doing the measurements and a frequency response plot when used as a 1:1, i chose a GM-70 at the source since its Rp was closer to the 75TL. the graphs should tell it all, the excel doc...

we don't know how they sound yet :-) i got around to doing the measurements and a frequency response plot when used as a 1:1, i chose a GM-70 at the source since its Rp was closer to the 75TL. the graphs should tell it all, the excel doc will let you manipulate the info and see the frequency respons...

I will wire with the primaries in parallel and the secondaries in series to derive a 1:2 stepup. I am looking at the following manufacturers: Tribute, Electraprint, Jensen and Stevens and Billington. Do you have any experience with the transformers from these various manufacturers to say what might...

i updated the images above to show what they are gapped at. I gapped the 80% nickel at .025 so there will be slightly less inductance than the .024 line on the graph. the gap on the graph is double the actual spacer, so the 49% nickel chokes have a .025 gap which is 1 piece of "black" shim...

are the outputs isolated form each other and floating??? can they be put in series connect A- to B+ and take a single winding from A+ and B- ? thye would need isolated grounds to do this, but the goal would be ot get a floating ballanced output. maybe witha little circuit work??? damn where did i pu...

How much variance will there be? Meaning, if the resistor is 260 ohms at 90 degrees F, what will it be at 120 degrees F? [Or vice-versa?] a resistor wound to be 248 ohms at room temp (68 degrees) will be 260 ohms ay 90 degrees and 277 ohms at 120 degrees. I think once the amp stabilizes, the temp i...

You can't tie the outputs together because they might (probably) have slightly different offsets, so they end up fighting with each other. gotcha... still might be worth a try for lester since he has the parts on hand... that is if it won't cook something :-) here is a crazy thought... place whatev...

funny you should mention it, i just wound them today and am waiting for the cores ot dry as we speak. DCR is 200 ohms as a transformer and 100 ohms as a plate choke. I just need to run the inductance vs. airgap plots and do an in circuit frequency sweep and they are ready to go. hopefully a big box ...

so i'll do them to be 260 ohms at 90 degrees with 25ma of current.

but i honestly think it will be warmer than 90 degrees, ambient temp with the amps off can be that in the summer without AC. maybe 120 degrees is a better target temperature for the 260 ohms???

let me know.

dave

hey jim, had a chance to play with your resistors tonight... trying to get heating (both ambient and copper loss) under control... or at least predictable. i played with the 260 ohm ones you requested, but i need to know two things... what is the current through them, and where will it ultimately be...

the lack of data on the chip makes me ask these questions... what does the chip actually do??? i know it has a voltage out, but google suggested it was a filter chip. I did try this and it had its benefits and also introduced some different problems. As you noted below this chip outputs pulsestream ...

It sounds like a dual primary transformer might be a really slick solution. Simple low-pass filtering gives you analog. (though he might try to talk you into 1:1 :wink: ) Dave it would definitely be 1:1 if i do it. small stepups and stepdowns just don't work for me :-) the problem i run into is usi...

it seems dave is on top of it, is there a link to the application sheet of the chip?

dave

For the full xover (4 ways) I need in total 8 coils. Most important is the xover between upper bass and mids which will be around 500 - 1k Since I'm still playing with the xover frequency the adjustability comes in handy. For this I need a value around 100-200mHy. I need 4 of them and they should a...