Intact Audio

That's really cool Dave, and it pretty much sums it up for me! Guess you've been here before...

Out of interest what was the DCR of the bifilar you used?

Andrew

But let's take this one step further and look at three different TX's into 100K, a nominal audio pre-amp load. The first TX and a second one that are roughly Dave's, the second assumes more money spent, so same inductance (also keeps things simlper) but less DCR and another one with the same inducta...

In the first image I have varied the load between 1Meg (light blue), 100k (red), 47k (blue) and down to 10K. I am using the first set of parameters for the bifilar TX given in the graph on the first page on this thread. You can see how the top three lines on the plot have very little roll off into t...

So...Dave's about ready to wind me the bifilars. The sound of the current set I have pinched from my power amp, the interstages, has me sold on the idea. But, what about DCR? What different does more DCR make, the inductance we all know about, of course, but what about DCR. Its all a series of trade...

I discovered primary loading a while back and I believe is it definitively an improvement over the normal secondary loading. I put 1 Meg across my phono inputs and a quality low value resistor across the primaries for the given cart. I investigated the reason for this phenomena and was convinced Mor...

Thanks for the reply Dave.

Looking at the two other bifilar transformers I (and Nick) measured I would have said 30nF is low, by comparison. I'm assuming that lower is actually a good thing, is that a logical assumption, is lower better?

Andrew

Hi Dave,

Anything on those interwinding capacitance values?

I'm erring to the side of the first set of values you suggested.

thanks,

-- Andrew

Hi Dave, Do you have measurements for the inter winding capacitance for either of these two designs? I have had access to two sets of interstages now, although unfortunately have only really listened to one pair. The first pair was as per the model posted 33H, 71nF, 400R. The second pair was quite d...

Hey, DCR's are 550 for the pri and 660 for the sec. A little high but not crippling going lower will either cost you in current, inductance or pocketbook (larger core). Bandwidth will be past 100khz without any ringing or need for loading. dave Just out of interest, Dave, how much inductance would ...

Just for clarity the 71nF in the model is, of course, the inter winding capacitance as measured by my Fluke and isn't a capacitor across the windings.

-- Andrew

Dave, just to add, I would happily place more emphasis on getting the choke right and then see what else has to change, for example, reducing the current on the D3A if that nets better inductance figures.

Please advise, you're the expert

-- Andrew

Hi Dave, E180F triode is about 3k5 probably a bit high for inductive loading. I'm happy with a D3A, which is what I'm currently using so that's about 1k9. I just wanted to open up a few more possibilities, assuming there wasn't too much downside, the usual suspects, 5842 (1k7), 6C45 (1k2). I'm curre...

Could it be a Hammond 126?

Its SJS, which depending upon who you talk to was/is or isn't the same stuff that was done for Border Patrol, what it definitely was designed to do was drive a 300B through from a 417A/5842.

-- Andrew

Hey... Really simple, a 1:1 bifilar on a nickel core. dave Hey Dave, What sort of numbers, inductance, capacitance and winding resistance should I expect to get out of that? I'd like a touch more inductance, I think, but if the winding resistance is too high, well its seems there's a downside to th...

So, Dave what can you suggest spec wise for a output transformer for my LCR? The output valve is currently a E180F triode connected or as with the current interstages I'm using a D3A since there wasn't enough inductance for E180F. I measured the interstage (a fairly well known brand) and modeled the...

Mid last week I built two more matching series regulators so we could give this a fair test. So, O had some good ears come around and we did our best at an A to B test. set up 1 is shared series reg -> CCS -> D3A -> 2uF cap -> output set up 2 is single series reg -> interstage primary -> D3A -> outp...

Thanks all, I think your advice is to try my interstages first, see if I like what I hear. Am I reading you all correctly?

Andrew

100mA are you sure Lars, I understood E810F to be 35mA max, I shall check

Hey Andrew,

For the E180F trioded, yes that seems about right, bit of roll off with only 50H on my interstages, but they would only be a try it and see if it was any good.

As Us is mentioned this is of course for the E810F.

Sorry, missed that bit.

Hi Andrew, Was in a similar position to you. I had tried anode chokes instead of CSS and liked the result although it was close. If I had the money, I would have gone for one of Dave's nickel 1:1 output txs. I went for a PP output stage as I had a PP tx lying around. Not sure what Rp the E180F has....

Izzy Wizzy and Andrew, Ri is in my post above. If loading E810F with 1,5k//1,5k=750ohm is to heavy a load you could go for a gyrator where the LCR is the only one, 1,5kohm. If using a CCS+regulatortube for the screen together with the gyrator you get the bonus of a humfree high voltage feed with ad...

Yes the E810F is a pentode, 1k5 Mills WW on the anode.

I could use D3a instead of the trioded E180F, or 6C45 or even 5842.

I wondered last night if it was worth trying some interstages I have.

I could try them with just the primaries as a choke and as pseudo output transformers.

Hmmmm...

Would be grateful of any suggestions.

Circuit is pretty simple...

E810F->1k5 Slagle chokes LCR->22nF cap->E180F trioded and loaded with a CCS->2uF cap on the output.

What next guys and gals?

thanks,

-- Andrew

Success!

Silence, in fact I wasn't sure it the phono was on until the needle hit the groove, these cases definitely work. I will post images as soon as I can.

This is interesting, I always fancied trying a LR phono as the next logical step from an LCR.

--Andrew

1k5 LCR hence the bigger (2uF) caps. Dunno how much bigger the 7K3's chokes are?

why not drill the side and mount them with cap nuts?


dave

I was worried about breaking the magnetic shield.

Dave, you can see why I need to trim the bolts

Trial run.....the other pair of chokes will go at the opposite side and the other cap and PCB at the other end (you can just see the left hand PCB under the cap).

Quick question for you Dave, I take it there's no reason why I can't trim some length off the brass bolts holding the frames together? There's a good 3/4" below the nut and I don't have room across ways unless I trim soem length off.

-- Andrew