Projects, rebuilds and or modifications….


Who here is in the middle of one or two? Currently I’m working on a Hafler DH-101. After reading the pooge articles and testimonials from other forums over the years, I decided to give it a go. So far the improvement in sound quality is not insignificant. 

128x128wturkey

“The biggest joy I get from modding is the steps of improvement and the sq improvements you can achieve with the proper mix and there are many sideway moves and a few set backs.”


Agreed. Regardless of the modifications being a win or a loss, it is knowledge acquired. The school of hard knocks, if you will. 

Another one I’m trying to workaround is the VPI Periphery Ring. My main table has an 11 1/2” platter that I’m quite happy with. Unfortunately the ring requires a 12” platter. Found some 1/4” o-ring material. Going to try to make a ring spacer for the periphery ring. 

The school of hard knocks, my father used to say he had a masters from the university of hard knocks. Hadn’t heard that in years.

 

I’ve been in the middle of designing a fully remote, all-discrete integrated amp going on 3 years now :-) So many details o work out, mostly from scratch. switching, switching logic, display logic, EMI immunity, gain stage, RIAA stages with 1500X amplification (can you say "low noise critical?") headphone amps, thermal control, DC sensing and shutdown, discrete volume and balance, human factors, ...... And once something is done, i learn how to improve it. Getting very close to the DFM stage tho, once i fix a few dozen lines of logic control code and refine the active ripple rejection i’m testing out (emphatically not a regulator)

 

 

The learning is a ton of fun, and as noted above, the pattern learning of "what makes what difference, and what, surprisingly, makes no difference or harms the perceived sound" (last one is rare, whew)

 

 

It has also forced me to go back and do far more extensive benchmarking of my older designs so that i have a reference for improvement. Sometimes that is a flattering experience such as when i measured, under roughly half load, my output stage power supply from 25 years ago, employing tube type PS design to a solid state amp, and measured less than 8mV ripple on the rails. i Concluded that using that product as my test mule was pointless since i was approaching the limits of field measurement. for the non nerds 1mV = 1/1000 volt (rms in this case). In a smaller, vastly cheaper product however the ripple rejection circuitry will yield great benefits. Now to prove/confirm it soudns the part.

from last year modding the caps and now the resistors of my super cheap chinese 6p1 amp

initially i used an adapter to use 6aq5s in place of the 6p1. brimar, great change.

also mullard ef95s, would the sound be too cuddly? not if you clean the tube pins well, what a revelation. mullards and brimars sounding transparent pristine, who would ve thought it?

i also found that NOS paper oil caps (US and USSR) as good as or better than modern commercial types like rike and mundorf.

at far lower prices. far lower.