z-adamson
Addicted Member
Best way to do it is to replace the lpads with fixed resistors. Much better that way. I find 9db of attenuation to be perfect. I use mills resistors.
New Owner JBL L100 Century
- Thread starter AK577
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AK577
Active Member
Not yet, but will be. At least partially. My 700B is full White Oak. Control board, back plane, etc. These 400s will have the new control boards, main capacitors, and transistors replaced. They will remain quasi-complimentary, whereas my 700B is full complimentary. (Technical terms that I’m just regurgitating)
These amps are my first Phase Linear experience. I was told the 400 has a warmer sound and sounds more full at lower levels. I can certainly agree after hearing both. The 700B is an amazing amplifier, it brings concert levels to my home and drives my 901s remarkably well…but the amp doesn’t shine until really driven. Maybe it’s just my amplifier, or maybe it’s rather common?
The 400 seems to be a great match for these JBLs
z-adamson
Addicted Member
What preamp with the phase linear?
Couple things…Marantz isn’t exactly known for being accurate. The signal is rather modified. Things tend to sound rather “warm” with Marantz. Depending on the preamp used with the PL, it is likely much more accurate than the Marantz. The L100 does not have a flat response at all and this is by design. The mids are boosted. This was probably more prevalent with the PL than the warm sounding Marantz hence the preference for the Marantz.
Edit…I see you are using a carver pre with the pl 400….but isn’t the 700b a power amp?
z-adamson
Addicted Member
1 lpad has to be replaced with 2 resistors. 1 in series with the vc and 1 in parallel with the vc. Just to be sure you understand. Performs much better this way, relative to an adjustable lpad. Sadly, so many are afraid to do this and take the easy way out and stick with adjustable lpads.
What stands are those?
Please explain why it is better. Why would it sound different?
AK577
Active Member
I bought them off eBay. They are APARA Vintage Speaker Stands. They are powder coated and very high quality, to me at least. Lightweight and solid.
They were $149.00 for the pair, I wanted the original stands for these speakers but they were crazy expensive. These do the same thing and I’m very pleased.
Photo courtesy of the eBay listing
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AK577
Active Member
I used my Carver 4000 for both the 700B and 400. The Carver is all original and they’re problematic to start with. I’m having it fully restored as well. I’ve had three of these 4000 Preamplifiers and every one of them gave trouble. I thought I learned my lesson with them, but I found this carver for a good price locally, couldn’t pass it up. I’ve never had one in good 100% order, so I’m sure I’ll be highly satisfied with the results.
It’s a very clear preamp, except you have to turn it up a bit to get that clarity. When the volume is all the way down, there is a distorted feedback coming through the speakers still. My other 4000s did the same. Very noisy preamplifier. Once you turn it up it sounds pretty good, I’m looking forward to having it restored.
R Swerdlow
Active Member
allsmith
Super Member
I like how the radio shack grilles look
I'm confused. An L-pad is essentially two resistors. Your two resistors are just a fixed L-Pad. What is magical about two fixed resistors? The Wikipedia reference doesn't seem to say fixed resistors are better. Is it because the elements in a variable L-Pad are wire wound?
BMWCCA
Addicted Member
It takes dirt, wear, and corrosion out of the equation.
z-adamson
Addicted Member
Consider the rheostat style electrical connections within an lpad. It is far from ideal. Especially considering that it is in the signal path of a tweeter/mid which plays highly directional frequencies that the human ear is very sensitive to. The resistors in an lpad are wire wound and I highly doubt they are non inductive.
So, the resistors are of low quality and not something I would want in the signal path. The internal electrical connection is suspect, not what I would want in the signal path either. The electrical connection is something that gets worse with time too. Properly soldered joints with fixed resistors is much better than what you get inside of an lpad. Resistors such as mills is much better than what you get inside of an lpad.
In short, the connection and the resistors themselves = the suck. You could do much better.
Not to mention the dirt, corrosion and wear as they age. A fixed resistor set up won’t age on you.
Lou F Quincy
Super Member
Bypass the L-pads and install quality crossovers. Great drivers with rudimentary frequency channeling control.
donprice
Wound up workin' at a gas station....
The weakest part of the design if you ask me. Replace them with some decent binding posts. I like these...
https://www.parts-express.com/Dayton-Audio-BPA-38NI-HD-Binding-Post-Pair-Nickel-091-1246
Yes, with tax and shipping they will cost more than the speakers
I have never had a problem in the 40+ years I have owned JBL's. The only way I could tolerate speakers without variable L-Pads is with crossover switching such as the KLH Fives; three positions. To each his own.