Hi Jan, Huh? I am not sure what parts you are referring to. Please mark up a schematic and post it so I can tell what you are asking about. I use blue mostly to show a change from an earlier version. It can be for many reasons, lower distortion, better S/N, better power filtering. Sometimes, based on the wide variation of diy builds especially concerning the tube brands and types as well as other components changes may not be better in all cases. I can only talk about stuff I have actually tried. I like to hear back when something doesn't work so that I can warn others to not do whatever it was. Thus far (fortunately) none of the changes to Oddwatts in design over the past 10 years has caused something to fail (tube amp failures are often exciting and costly) but have in some cases altered the sound a bit. I find that changes in the sound
are common when the coupling cap brands and types are different as well as changing tube types (like KT77 in place of EL34) and sizes (like KT77 vs KT88). That is something that can not be eliminated. In some ways it makes the diy process fun as tube and cap rolling can be rewarding.
Just as information... right now my personal choice for driving my main speakers (Martin Logan ESLs) is Oddblocks running new production Mullard EL34s with the 15 inch subs (in 200+ L enclosures) on another pair of Oddblocks using JJ KT77s. A close second for the mains is a pair of KT120 Oddblocks. Considering the heat generated and power used I went back to the smaller ones about 6 months ago. All present amps are set for about 15 wrms each with the crossover (electronic 24 db/oct) at 55 HZ. I'm using a Forewatt in passive mode most of the time when the input signals are sufficient. When not sufficient it uses JJ ECC802S tubes. All coupling capacitors in all components are Audyn TrueCopperCaps. I have worked a long time to get it to sound to my liking. Others might prefer something else. IMO it is quite stunning. It (like all systems) will never create the effect of being at a concert....but it certainly presents a believable rendition of one. Pianos, female vocals and stringed instruments (like acoustic guitars, harps and banjos) are to die for.
Good listening
Bruce