The Amp Garage

Jim Seavall could best answer that. My guess would be that the 30 watt voice coil will be lighter than the 65 watt voice coil, which would probably lead to better treble response, all else being equal. Pete.

[quote]plate V was riding about 492 ...with the screen riding around -2v to the plate
pretty close to a 6l6gc max screen voltage [quote]

Surely that's way over the max screen voltage (450V)?
http://www.mif.pg.gda.pl/homepages/fran ... /6L6GC.pdf
Pete.

I always use a 500k audio for the bass control in that tone stack; even then it's only ever in the '1-4' range of the control. Check it out on Duncan's TSC; with a 1M log bass control, the upper 30% of the range is only affecting subsonic frequencies. Whatever, putting a 470k resistor in series woul...

Whats the budget, $20? Should be plenty, though may to to stretch to $30 if including 'black goop' of a real 'clone'. But yes, I'd love an insight into Andy's approach to this. It's a wide open platform with many options. Most recently I put it close to a AB763 reverb channel, with a 'clean' boost ...

If running cost is a consideration, the DSL power tubes are likely to last far longer than those in an AC30. Also microphonics and tube rattle will be less of a problem with a head than an combo. Pete.

If the drop is that big, maybe your tubes are drawing too much off the heater winding. Surely the heater winding would have the highest current draw at power up, when they're cold? Once they've warmed up, it should drop down to normal. Check the current draw of the output tubes, ie bias. The lamp l...

Some amps used volt dropper tubes such as OC3 between the plate and screen nodes, see Leslie 147. http://www.captain-foldback.com/Leslie_sub/Leslie_schematics/147.GIF Nowadays a power zener could be used instead. That arrangement would avoid the high power sag on the screen node, in the case of cond...

Ahh, that explains why their Valve Art KT66 are such a good price. Thanks for the tip off, I was going to order some. Pete.

Thanks for the further rationale and detail Andy, I'll look into it. However, I need to brush on the theory to do it justice, time for an RDH4 session. Pete.

How much did the screen grid voltage change? Are you sure that you didn't fix a bad screen resistor in the process of doing the mods? It's just that when I've put a 1k resistor in series with the choke, with a switch to short it out on the back panel, I've been hard pressed to tell which way I had t...

Yes, the Mojo impedance switch would be fine but the user must understand that the switch mustn't be operated while the amp has any kind of a signal going through it - I'm assuming it'll be used with a tube amp. You need some kind of a signed disclaimer that absolves you of liability for any consequ...

I seem to remember that it's a 'BAD THING' to apply B+ to cold tubes - cathode poisoning was the issue maybe? Pete.

Also try searching for PEM nuts. Pete.

Regarding screen grid resistor size, from 470R to 1K there is some local negative feedback happening with EL84 IME. That's my understanding also. My thinking to limit screen dissipation is, rather than fit such large screen grid resistors to each tube, to 'common' them up then bypass to ground and ...

So, for the screen supply, that's three 1k resistors in total?
Thanks for the info - Pete.