Hi Patrick,
don't laugh - I deleted some lines about those old ampegs and the
Baxandall... Did I really delete them? =
the components I'd consider to measure and clone ain't the pots, but the
caps, the slope resistor and the cathode caps (them throughout the whole
amp). It's the whole system - not just the tone stack. Differnces might
be subtle. You are dealing with - humans - worse: artisans
For me the speakers themselves don't need to be "old". IMHO the
particular OEM-Emi in the DRRI is simply a piece of ****. It does not do
any justice to the capabiliies of the amp.
New speakers ain't generally bad. You've got a hunch of choices
nowadays. IMHO there are some Speakers to consider with a DR:
EMI RedFang,
Celestion Alnico Blue,
Jensen Electric Lightning,
the WGS Blackhawk,
Celestion G12-65;
EV-12L
et al
It's simply a matter of taste.... Myself, still opinionated, that
"better" is not always necessarily "BETTER"..... But I have to confess:
I'm a convinced player of an old 5E3 Deluxe Repro with an 12" Alnico
Blue RI - far away from technically perfect, but a real fun machine ;-)
regards
Jochen
Well, I guess I should leave all that you said alone because probably it makes a lot of sense to the muso brigade.
BUT, I had a look at a few Ampeg pre-amps and they all have just bass and treble and no mid to make a big dip at around 400Hz. The tone "stacks" are NOT stacks as such but are stock standard Baxandal which give the widest possible range of bass and treble variation. Pots are 1M so network RL is all high enough ohm load to be driven by ****-week 12AX7 anode power. I'm not going to put in 1M pots to replace what's there but will stay with 260k pots and try for a Marshal type of Mid dipper pot and C. But I'll put a follower in to drive the tone network which will better preserve gain, and give the wanted curves with highest possible slope.
I downloaded a Tina90-TLen program for simulations of R&C networks and much more. It took an hour to learn how to use it, and its clumsy and slow and you have to keep closing pages and re-opening and starting new ones to see what changing C or R properties does to response. But the response of what I measured yesterday were exactly reproduced so I have faith that it works OK to simulate such things.
BUT, Suppose I tried to draw a response line I wanted, then enter an order for program to tell me what R&C to use, the program would be quite useless at telling me what R&C I should use to get that specified response.
As soon as one expects the PC to act like a human, its ****ed. Like, OK, we want passive, no extra tubes or NFB & PFB loops, and we want it NOW, and no more than 20dB insertion loss, and whatever it thinks up must be as close as it can get to the wanted curve. Hmm, I reckon I can guestimate faster than involving a dopey 3rd party.
Its not hard for humans to think up stuff that a PC cannot answer.
So, I have a bit more trial and error of pot values and C values to use to try to create an adjustable 400Hz dip, so that the tone control can give the same response as the good sounding amp - but with a lot more to play with..
Are the people on the nearest planet to us outside the Solar System purple, with yellow stripes?
Nah, PC and Google is useless.
Patrick Turner.