This second batch of mods was to clean things up a bit, but also to help in the sound quality as well. There are as follows...
A little tweaking and tidying up:
1) Replaced the 0.1uF - 50V input caps and steel jumper with 20awg OFC wire jumpers. Since my cdp doesn't put out any DC of any kind, I decided instead of upgrading these caps to better ones, to just completely ditch them and use wire jumpers instead, as well as replacing the nasty 24awg steel jumper in the right channel signal chain.
2) Placed PS transformer on nylon standoffs. The standoffs came from the LED brackets in the window display that I removed.
3) Omission of pre-out connections to RCA jacks, pre-out caps & garish window tube display. I don't ever plan on using this amp as a pre-amp, I removed these components to clean up the interior a little and free up some space. Plus, that window display just yelled out "CHEAP!" That was just taking up usefull room, probably adding a bit of noise and using up unneccissary power from the PS.
4) Moved Mundorf caps up front in window. This frees up room in the back of the unit. Plus, these caps are so large that they overlapped the audio board some, not allowing me to easily remove the mounting nut and/or board from the chassis. Now they are out of the way, and much closer to the headphone output jack, which will be perfectly convenient for a future upgrade.
5) Added a ground wire to the ALPS volume pot. I had to do this as there was a slight 60 cycle hum coming through when the volume was turned up anywhere between the 12 o'clock and 4 o'clock position. Not that I ever go up that high (the most I ever go is about the 11:30 position), but knowing that
that noise was there bothered me, hence the ground wire. Now there's absolutely no noise anywhere throught the range.
Refers to #1: This...
And this...
Replaced with this...
And this.
Refers to #2 & 3
Refers to #4
Refers to #5
Here's a couple extra shots of the 2nd batch of completed mods and new "window treatments".
More Tube Rolling:
I decided to go out on my own this time and try some tubes that interested me. One of which others have tried on a "stock" 708B, but never on a modded one. This is the NOS GE JAN 5670. This one in particular is from 1968. The reason no one liked this tube is because it created too much hum or noise into the signal. Again, this was with all stock 708B amps. However, I put this 5670 tube in my amp and it is totally, completely and 100% dead silent, even at max volume and everywhere in between.
I also want to try some different output tubes as well. I've heard that the Amperex-Japan 6922/E88CC tubes were actually made by Matsu****a, which are very VERY good tubes.
Here they are...
As for the sound, I feel that they have a better "grip" on the music than the UK made RCA 6DJ8's and Russian 6N3P EB that drarthurwells recommended. They DO have a wider soundstage, the dynamics are more dynamic, bass seems to be a bit tighter and definately deeper, the midrange is full and natural, and the treble is still smooth, crisp and extended.