This used to be a solid state preamp, that I never liked, but love the the look and design of it. And also had a Dynaco Tube preamp, that was my favorite, but it was ugly as hell. So one day, I removed the power transformer from the Dynaco and the center line/main board and installed them both into the HK chassis. To me later doing away with the Dynaco line/main board that was about the same size of the newer board I have in there now (picture). I had a previous bard in there that replaced the one that's there now and was very pleased with. I got both off Ebay. The previous one I used with the Feedback removed. This one, I'm using feedback. Ive made some changes to the other one, but this one is the same as I received it. Really sounds good and does a great job at smoothing out the CD sound and making it sound more natural. But did have to replace the 12AX7 with a 12AU7. Both tubes are now 12AU7. It sounds much better that way
I paid about $13.00 for the board shipped from China. It came with the parts shown, only needed them soldered in place. I had to do some grounding changes, and want to do a little better cleaning up the 300vdc main supply. The Filament was also changed to DC supply from the transformer and it's also filtered using an electrolytic cap. I've already installed a larger electrolytic for the 300 vdc, rail, but has not yet connected it. I plan to put a 280 vdc regulator there, similar to what Conrad Johnson did on some of their Preamps. But that's another day altogether.
Link Posted: Fri Feb 23, 2018 10:45 am Post subject:
Now moving on with this, I'll next deal with adding a Phono Preamp section. So far, I've decided to go with a Quasi-Diferential Solid State design. So giving thought to this, you would think I would complement a Tube Line stage with a Tube Preamp Stage, but that's not going to happen here, because my experience has been that for Phono Stages, Tubes are usually more susceptible to noise that is either from microphonics (from vibrations) or develop a slight filament hum, and when a tube operates at higher gains,they have tendency to be noisier than solid state. Plus a tube design would not be so feasible here.
My first and most convenient solution was to look in my crawlspace, where I keep my Audio Stash. There among the amps and such, was a Yamaha R100 Receiver. And that is where the board in the image is from. I will start out by cutting the board, or removing that section that is not associated with the Preamp circuits. And from there, install it into the Preamp itself. I've already did a placement of the board to see if and how it should be fitted. It look like I'll have to tilt it a little because of it's height.
And before installing the board, I will be replacing that M5219L (already removed) with something far better these days, to include recapping and making sure it will get it's +/- supply from the regulated power supply already in the Preamp (right near transformers). And depending how it all turns out, I might go back and replace the carbon resistors with metal film.
The switch on the board is for MM/MC cartridge selection.
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum You cannot attach files in this forum You can download files in this forum