 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
208.47.202.254
This is a follow-up to my post in Amp/Pre, linked below - posting here, to shift focus from "viability" of the idea of passive biamping, to the particular issue it caused, and the ways to deal with it.
In short: passive biamp configuration, with SS amp on bass and tube on mids/highs, worked fine - until I powered the tube amp down first, which caused blown rail fuse in SS amp. Turning off the SS amp first, which was done several times before that, did not cause any bad consequences.
Researching the subject, it seems the result of interaction between two amps, either via shared (non-isolated) preamp outs, or via speaker's crossover. According to one version, tube amp on turn-off sends DC to the preamp, which gets to the SS amp, and causes oscillation.
Questions:
- what is the most likely cause?
- what to try?
I saw isolation transformers suggested, but in some other thread, a person who had bass amp connected via transformers, still had the same issue, when tube amp was powered down.
Suggestions please.
Follow Ups:
what to try?
I've used bi-amping successfully for several years with a pair of Quad 303s so upgraded they give 'Trigger's Broom’ Paradox' a run for its money. The difference between one amp and two is, in my case at least, very marked with SQ distinctly improved.
I use one amp per channel (not one for HF and the other for LF as you do) so the only link between the two is a common power connection. It's not, for obvious reasons, a permanent solution but the first thing I'd try is the one-amp-per-channel scenario. At least you might discover (or perhaps already have discovered) something.
I also ensured that the crossover circuits in each speaker (LF and HF) were electrically separate as it seemed a sensible precaution and was easy to do.
Could your DC-at-the-pre-amp hypothesis not at least be tested by putting a suitable capacitor between the pre-amp OP and the tube amp IP (correcting for phase reversal by swapping one pair of speaker leads)?
BTW, are you still using a Lampizator pre-amp?
A single cap will shift the phase 90 degrees so swapping polarity will not correct this. Best to use caps for both amps. Assuming the input impedance is 50k, then a 0.47 mF cap will block the dc without interfering with the bass. Caveat: A lot of amplifiers have a input cap already so this may not be a solution.
A single cap will shift the phase 90 degrees so swapping polarity will not correct this . . .
This is true (I checked later but the OP had already moved on so I let it go) but the suggestion was explicitly for a quick fault-finding test, not a permanent mod.
A lot of amplifiers have a input cap already so this may not be a solution.
It's an "interesting" design that doesn't but, since suspected DC on the DUT's input blew a fuse, my hunch was that it might just be such a one.
So far, DC on the input seems the most realistic assumption, and designer of SS amp, whom I contacted, confirmed that the consequences could be indeed blown rail fuse, if that was the case.
For the time being, I'm just going to watch my power-off sequence carefully. Tube amp is going to its manufacturer anyway, for a fix and couple of upgrades, so I'll raise that issue too.
Ya' know, everything you do to your system involves risk mgmt decision making.
Then again, maybe you don't know.
Jeepers. If you're not happy with either set of amps, just sell them and buy a single amp or pair of mono blocks that perform more to your liking across the entire frequency spectrum.
You're certainly not going to uncover some lost world of musical bliss by unnecessarily complicating what must be a very simple system configuration (if performance is your goal).
Don't think, "More is always more."
Rather, think, "Less is always more."and your brain, your ears, and your wallet will thank you.
Also, you would probably want to familiarize yourself with the subject, before expressing your strong opinions.
If I were in your shoes, I'd want to avoid being lectured to also.
As for nonsensical? That's a tough pill for me to swallow coming from a guy who just blew one or more rails in his amps for no good reason.
Just like there's no good reason for me to become more familiar with the subject but I suspect you were seeking the so-called "best" of both worlds.
By all means, Sparky, go play and have fun.
Especially considering that you have no idea whether it's viable or not.
Here's some facts and a question for you (don't worry, it's simple):
- many people consider this solution viable, and use it for years with great results;
- I personally made sure that it provides sonic benefits;
- respectable industry figures, like A. Von Schweikert, for instance, consider it advantageous.
Question: When some random dumbass on the web, who clearly never even tried it, posts idiotic condescending lecture against it - what am I supposed to think?
Fair enough, big guy. But just to ensure I'm not the dumbass you claim me to be, I checked my amps to ensure the internal fuses are still operational. They are.
You never mentioned what it was you were intending to achieve with this configuration. It would be nice to know.
You personally made sure there are sonic benefits? Great. I'd love to hear about them.
But while you're typing your response, I'd like to reiterate that the strategy "less is more" is IMO, a much more viable strategy than bi-amping. For a number of reasons:
1. That slogan is very true in perhaps every other performance-oriented industry. Why would you think "high-end" audio is any different?
2. If you have an awareness that we are all equally and grossly adversely affected by noisy AC coming in from the street, then surely you are aware that you must properly address that noise by one of several means. Otherwise, with one power supply verses 4 power supplies and hence the entire components' internals, surely you can start multiplying and see you now have potentially 4 times the amount of noisy AC potentially inducing sonic harm on your playback system. This is not a problem if you employ proper AC mgmt. Are you?
3. Essentially the same logic applies to proper vibration mgmt. Would you prefer to have 1 or 4 components being continuously bombarded by air-borne and internally-generated vibrations (e.g. 4 power supplies)? If you've not properly addressed this area (I know you haven't) you now have not just 1 but 4 chassis' loaded with resonant energy and nowhere to go but completely dissipate within.
Or perhaps your system is already so overloaded with these universal distortions that it doesn't matter how many more components and connections and cables you add, it's already fully saturated and can't sound any worse?
There are potentially several other concerns but one other worth noting might be:
4. I have no idea if you have dedicated circuits/lines for your amps, or if they are high-current drawing amps or not. But if per chance your amps are all 1 or 2 shared circuits/lines, I'd venture the chances are pretty good you're also squashing your system's dynamics during dynamic/complex passages. Not a problem if your amps aren't starving for juice, or if you listen at elevator music levels, or if you prefer flat lifeless music.
Anyway, just a thought from a random dumbass on the web.
--------------------------------------------------------
"Give me less!!! Then we'll finally hear more." -me
No need to get huffy, the both of you chill out!
Moderator,
Jon Risch
The Most likely is the DC from the tube power amp back to the pre-amp then through the shared AMP OUT connection to the SS Power Amp.
The Most likely is the DC from the tube power amp back to the pre-amp then through the shared AMP OUT connection to the Power Amp.
Post a Followup:
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
