jelle wrote:Question: what is the 10k and diode at the cathode follower?
That's a Merlin Blencowe special and prevents arcing at startup. Cheap insurance and tonally transparent.
Let's figure out how to hear it! haha
Hey Pablo, I like my ultra master (more than three master) amps. It's incredible to find ways that they can work together for many different tones. Are you going to leave a few?
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
I'm really impressed, and i really like the layout of all the secondary fuses right at the PT secondaries. I was juts curious about how to choose the 800mA perside vaule for the HT secondary fuses? I would think something like 350mA per side would be more appropriate. Again stellar work, and glad to see those PECs fit- there's a little more space on the Visio drawing
Reeltarded wrote: I like my ultra master (more than three master) amps. It's incredible to find ways that they can work together for many different tones.
You are a slave to your masters! You gotta love masters though...great tools to shape our sonic clay!
I understand that choosing a fuse value is sort of a trial and error process. Things like in-rush currents, large smoothing capacitors, AC vs Dc fuse voltage ratings influence the results, not just the tube's ratings. I've seen a couple of examples of 2xel34 amps using 750ma fuses in the HT secundaries. I can only remember now a KOC version for a Hiwatt 50w. He called it the Bull Dog. It even uses the same PT as my plexi (TUT3 or TUT4). Maybe I should go a little lower with kt66, although I've see some kt66 datasheets showing similar maximum anode currents to el34's. I'll try with 500ma and see if they hold.
I think it is not very relevant to choose the exact correct value, as long as your are in the same order of magnitude. Transformers will withstand high currents as long as they last seconds. I might as well be wrong...
Thanks for the reply, I was just curious if about how you arrived at the values. I too have TUT3, and have been very confused by his fuse selection as they are not consistent from project to project, nor explained. Honestly, I don't think he's ever built any of the projects in the books.
500mA fast or slow blow in the DC side of the circuit is the time-tested value in amps with with 2 6L6, EL34, etc. Since the RMS current in each leg of the rectifier is 1/root2 multiplied by the DC load current, then each fuse *should* be 1/root2 of the 500mA value, which would be approximately 350mA.
And you're right, the PT can probably handle it, but since the amp's working, I'd be tempted to try the 350mAs, crank it up and see if they pop. Can't do any harm.
I tried 315ma fuses for HT (closest I could find to 350) and they held out with the amp cranked. You were right, Gaz.
I will probably be building another one soon, this time with Koa resistors and Jupiter caps. I won't know which differences are explained by the caps and with by the resistors, but it should give me an idea of how good the AMRGs really are.
I'll try to have some clips recorded this weekend.
Did you ever figure out the GMX source of distortion? I have not dug into the schematic enough to offer any suggestions but you may wish to email Kevin at the London Power website. He usually answers my questions quickly.
No, I didn't... I took the GMX out and concentrated on getting the voicing right. I hope to get it back in next week. Kevin has been very helpful with me with other issues, but I want to be sure that the problem is isolated before I ask for his help. After recording some clips without GMX I will also be able to explain the problem by recording the same clips with GMX.
Good luck, one of the things I am planning on doing is making the GMX effect switchable.
Kevin responded with this "For a simple on/off of the GMX effect, relay contacts can be wired from the GMX control wipers to reference (pot-0) so no drive signal gets to the active circuit."
The effect is more related to feeling than sound. I don't thing the rest of the world would notice the difference in a band situation. If I like it, I'll probably leave it on all the time.
You gotta love masters though...great tools to shape our sonic clay!
