donsachs

Responses from donsachs

300b lovers
@alexberger Fine is a relative term.  If you improve the power supply in a citation II the amp is greatly improved.  That is why the KT88 amps I used to build have FAR better power supplies than vintage amps.  If you build a vintage amp with the s... 
300b lovers
Actually I have rebuilt 3 or 4 of the ST70 amps.   The best version is to skip the 7199 or 6GH8 types and to one install of the octal driver replacement boards.  I really liked the 3 6sn7 tube version that tubes4hifi used to sell and perhaps still... 
300b lovers
Well... Lynn has lots of wild ideas, but the thing is that they are very well thought out, and they are based on years of technical experience with Tektronix.  I learned many years ago in academia, and as part of my main career in forest ecology r... 
300b lovers
@tinear123  No.  Production starts in late November when I go to Salt Lake and teach the guys at Spatial the builds.  I would expect a review by late spring and perhaps an audio show in the west somewhere next summer.  That is kind of going to be ... 
300b lovers
@alexberger Please report back on the sonic diff between the A-107 and RC coupling.  Completely different amps, but I much preferred all IT coupling.  Curious to hear your impression  
300b lovers
I just cannot resist.  This is a poor photo of the square wave on the Blackbird interstage transformer between the 6V6 and the 300b at 1 KHz and about 30% power (7 or 8 watts).  There are NO grid resistors or grid stoppers or networks of any kind.... 
300b lovers
@tinear123 Hi.. write Cloud Sessions at Spatial audio lab and he will know what is in the crossover.  I am sure they can build something for you.  
300b lovers
I see Lynn has spilled the beans on the driver tube change.  I have listened to the 6L6 (Russian 6P3S-E), the KT66 (Shuguang black treasure KT66), and the KT88 (My stash of a quad of the now unobtanium Shuguang WEKT88).  Of course I have spent alm... 
Linlai KT88 experience?
I buy many Linlai tubes from a trusted seller KT88-D and will try them out next week.  I expect them to be very good and well made.  
300b lovers
@stephenr First off, thanks for you polite post on this thread. I bet your 12B4 preamp sounds great. I have tried removing the Raven preamp and going direct to the amps from the Lampi Pacific DAC via xlr. It sounds very good. It doesn’t sound near... 
300b lovers
The thing about the transformer coupling is that once done correctly, it just works.  It will not fail.  It protects against a tube that may develop a grid short.  Rare in smaller signal tubes like the 6SN7, but I have seen it.  So for a commercia... 
300b lovers
@gladmo Spatial Audio Lab will be making the amps and preamp.  All parts are ordered and I hope to be going to Salt Lake City in early November to train them on the builds: https://www.spatialaudiolab.com/news/september-2023-update If you have ... 
300b lovers
This has been an interesting thread.  I didn't start it, nor did I expect it to have this long a life.  It is very clear that there are many ways to build amps and preamps.  I just want to restate my goal for this project.  I am semi-retired.  I w... 
300b lovers
Yes, these amps sound very good after 10-15 minutes and are very consistent.  They sound the same every day.  I have the preamp and amps plugged into a Puritan supply, which does clean up grunge in the AC line.   Basically, you turn them on and th... 
300b lovers
The Blackbird amps are running the 300b tubes at about 400V B+ (plate - cathode voltage), and just a wee bit under 80 mA. About 31.5 watts at idle. They sound wonderful and should last a very long time. The tubes each have their own independent re...