Friday, July 23, 2021
Herculean DIY Autoformer wiring.
They say a picture is worth 1000 words... well how about how about around 180 wires and 820 solder connections? Brad from the Boston contingency wired 6 of the 28 position autoformers up for Caroll's home theater system. I often joke that more than half of the $200 autoformers I have sold sit partially wired in a box on a shelf and this picture might explain why.
Sunday, June 20, 2021
blink blink blink
Feral Eye a number of years ago and the fate it met from Hurricane Sandy. It was brought back to life by steve berger as a PP 10 amp with a 49% nickel phase splitter and last night I got to hear it with a quad of mesh 10's from 1929.
Wednesday, April 28, 2021
Another Early Strain Gauge
I came across this cart on the 'bay and it is from an Admial 6F10
The other quirk is that it has three terminals with rather high resistances.
Monday, March 22, 2021
Autoformer Frequency Response
Had a customer ask for details about the frequency response of the autoformers and while I honestly believe a picture is worth 1000 words, I'll add a few comments. My general statement about the high frequency behavior is they behave to 100kHz without the need of any sort of loading network. I like to show plots that cover the areas where a device misbehaves so a pattern of behavior can be identified. Lots of people will just show a random well behaved sweep and call the device perfect. I want you to see the squirrels. Unfortunately plotting around 50 steps in 1dB increments creates an incredible mess so I picked a random sampling to get these plots.
Around 20 years ago I showed a similar set of plots from a step up transformer to Frank Schröder and he commented how the behavior was unacceptable @ 20kHz to which I replied "check the scale" at which point he realized he read 200kHz as 20kHz and his opinion changed.
The other set of plots that shows important behavior involve the low frequency end of the spectrum and for this it helps to pick the worst case scenario with the +7dB gain setting of the remote autoformer.
The above plot shows the +7dB setting driven from 100Ω, 500Ω, 750Ω, 1000Ω and 1500Ω. This represents the worst case situation for the low frequency response an with a 1500Ω source the -1dB @ 20Hz is borderline. It is also interesting to see how the top end extension is also compromised in the +7dB position with the 1500Ω source but if you then move down to the +4dB position things look better and from unity and below all is well. I could have simply showed the Red sweep above from 20Hz-100kHz and called the device perfect but alas perfect transformers do not exist.
Thursday, March 4, 2021
Unsafe At Any Speed
Wednesday, February 17, 2021
I know the inerwebs are filled pictures of beautiful Garrard 301's and by that standard this one is a bit pedestrian.
another 20 steps back reveal that this is then paired with a pair of Tannoy Westminsters in a Japanese restaurant in NYC and suddenly that first picture isn't so pedestrian any more.
Makes me really want to exit my bubble and be one of the lucky folks who gets a table during the 25% seating capacity phase of the pandemic.
Thursday, February 11, 2021
I have recently found the need to adjust Zenith by small repeatable increments and it seems that hot glueing a laser to the side of the cartridge proves to be quite effective.
The need for this type of repeatable precision was so I can plot the change of IMD against Zenith angle and the results are telling.
If you want all of the sordid details have a look at the link below.
and for an update on some old dirty laundry check this out:
Wednesday, January 6, 2021
Expanded my bubble with a covid test and a visit for a weekend of listening to cartridge variations in DC.
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