agedhorse

On 18/02/2025 at 03:36, Chienmortbb said:

Fans get a bad rap but without them our heads ( amps not real heads) would be much bigger and heavier. On the ESP Audio Pages it is reckoned that a well placed fan can improve heat dissipation by 4 times. So the heatsink could be reduced in size and weight to 1/4 of passively cooled heatsinks. 
 

Many of the amps I see have less that ideal fan cooling. I have just got a Mesa D800 and the fan in that is always on but very quiet. I have yet to use it at a gig or rehearsal though. The truth is that if you want small and light, you need fan assisted cooling. 

Cooling an amp in a way that's effective, quiet AND reliable is a lot harder than it appears. The fans that are featured as "super quiet" usually do not have the airflow , especially under any static pressure losses that a cooling system presents. 

The D-800 has a fairly expensive ball bearing fan that's reasonably quiet (not as quiet as the sleeve version by a dB or two) but is very long life (about 50k hours compared with about 5-10k hours of a typical sleeve bearing fan). It also runs continuously at a slow speed because the resulting air flow allows multiple components to stabilize thermally together as a system. It's extremely unlikely to ever run any faster than the slowest speed, even at 2 ohms.

Back about 15 years ago, when I was working at another company, I led a research project (with the cooperation and support of ICEPower R&D) that specifically addressed a whole slew of thermal and dynamics/duty cycle management design approaches, which resulted in a US Patent relating to this application. Some of what we learned, and how they relate to bass guitar ended up being incorporated into the newer ICEPower modules. 

Very few intended as a gigging amp, because live, reverb generally causes more trouble than any benefits it might bring.

For recording, that's a very different application. I find that it usually works better to track dry and then add verb at mixdown so that it can compliment the bass in context of the mix. What sounds good solo often conflicts with the mix and muddies things up in the low end.

In general, when buying new, you get what you pay for... and if a product's claim looks too good to be true it's worth further investigation to determine how untrue that claim might be.

8 hours ago, Jo.gwillim said:

getting the hang of it now. dissappointed that the high pass filter knob affects the DI output AND the cabinet. I use the HPF to stop the stage boom but want the FOH sound bod to apply or not apply HPF to suit.

With the DI in the "direct" or "pre" modes, the HPF shouldn't affect the DI out. 

Unfortunately, their owner's manual block diagram forgot to include the bottom control, so there's no way to know if it's supposed to be applied in "post" mode.

9 hours ago, Chienmortbb said:

I was directly replying to @agedhorse's comments about how hard it is to do business here now. I could have put it in off topic but I believe it is entirely on topic for the way this thread has developed. I am happy to refer myself to the moderators though.

Agreed, it helps to explain why it's becoming difficult for manufacturers to provide replacement parts at a reasonable cost. For many parts, we could give the part away for nothing but the shipping would make it too expensive to justify. 

In many cases, it's not because the manufacturer doesn't want to help, but because the way trade is changing, it's sometimes simply impossible to help in a meaningful way. It can also apply to American customers trying to get a replacement part out of Europe these days.

8 hours ago, BassmanPaul said:

No not utter madness - just the way the UK seems to work!!!

 

It seems to have changed after COVID, it used to be ok.

10 hours ago, Bill Fitzmaurice said:

It's getting worse. ChatGPT is really bad, because what it posts comes from searching sources on line. When the search turns up bad information it passes it on without peer review. 😒

I totally agree Bill.  I see it when I'm forced over to the guitar side to help out with support, and some of the comments players state as fact would take your breath away... they are really that gag-worthy.

We must also remember that there’s a lot of incorrect and terrible advice given through YouTube and other such platforms. 

Actually, balanced inputs do cancel noise that is common to both the + and - conductors, either through an input transformer or differential amp at the input stage. They amplify signal and noise that is not common to both conductors. 
 

Balanced is independent of level or connector type (provided it has 2 terminals plus ground… and ground may not be connected at both ends either because it is purely for shielding and not necessary for a balanced system to work. 

12 hours ago, SimonK said:

 

I broadly agree with this - as Biochemist/Biophysicist speaking (at least originally) - there are plenty of biochemical systems that rely on the flow of protons rather than electrons, with the resulting electrochemical gradient measured in volts, so I would say volts are often used to describe the state of a system.

It doesn't matter if it's protons or electrons, an outside energy force (mechanical, chemical, thermal) is required for there to be motion.

13 hours ago, TimR said:

Weird. I thought that moving magnets exerted a force on the electrons, causing them to move. That's the EMF. There's no voltage moving the electrons. The voltage is caused by the  electrons moving from one place to another. 

 

That's why voltage is defined in terms of current, not the other way round. A higher voltage is just where you have a higher density electro magnetic, electro chemical, theromionic field, or capacitive storage.

There are only 2 ways that voltage or current can exist without the other, these are both defined as limit or boundary functions... meaning that they are more theoretical than practical (though you can get close under ideal conditions).

Voltage can exist with no current flow IF the load resistance is infinite (an open circuit with no parasitic shunt leakage) because I = V/R, and as R approaches infinity, I approaches zero no matter what the value of V.

Current can exist when the load resistance approaches zero (a short circuit with no parasitic series resistance) because V = I x R, and as R approaches 0, the voltage will approach zero  no matter what the value of I.

There is no way to split apart the voltage and current relationship in resistive circuits except when R is either zero or infinity. While the voltage is generated by electrons moving from one place to another, an outside force or element must exist for there to do so. The outside force generates a voltage with no net current if the load is open, a current with no net voltage if the load is shorted and somewhere in between if the load is resistive. 

1 hour ago, Chienmortbb said:

Volts and current do have to coexist, in a resistive circuit, I think that going into phase shift, reactance etc. is a step too far for here. In fact, things have probably gone too deep for most already.

 

Agreed.

Voltage and current have to coexist (in resistive circuits) until you add reactive elements... then it's possible to have current with no voltage due to the phase shift between the voltage and the current (for AC) because power is stored as voltage or current in the capacitor or inductor. This is an entirely different topic however.

10 hours ago, bremen said:

You do know that you can buy recone kits, and it's not nearly as difficult a job as you might think. I have 46 year old Tannoys and have reconed more than one of them.

With Eminence, most OEM recone kits are raw kits (unassembled) but only available to the OEM manufacturer and it was a 10 piece minimum (though that may have changed in then last few years). It's more difficult if you need to recone them from raw kits and do them properly to meet the original specifications to last like the original factory drivers. Details matter, and what I see of recone work by end users is usually awfully scary.

9 hours ago, chris_b said:

 

These are custom drivers, made to Alex's specifications, so my guess is that recone kits won't be available. Always worth an email to confirm.

Correct, I wouldn't expect these parts to be available unless Alex has them. 

Just because recone parts fit doesn't mean they are correct. The driver may make noise, but will be nothing like the originals. There are some abysmal aftermarket parts kits sold as original out there... buyer beware.

Shipping to the UK has almost doubled in the past 2 years, and the bigger challenge is dealing with UK customs which seems to be punitive to UK citizens. Add to this the VAT that applies on all costs including shipping and you have an unsustainable business model. The EU is similar though not a punitive. After my last battle with UK customs, where the paperwork was affixed to the package clearly marked, they returned it because of incorrect and insufficient paperwork, then lost the package. It mysteriously showed up at my shop 3 months later after their tracking showed that it never left the customs warehouse and customs washed their hand while shipping insurance refused to honor any coverage. Ultimately, after finally getting the amp back to the customer, he paid over $800 USD for a $150 repair (all due to charges and screw-ups at his end).

Because of this last experience, I can no longer offer international service (outside of North America) on Genz Benz products. It's a sad state of affairs, and likely to get worse before it gets better.

17 hours ago, ossyrocks said:

 

Ok, this is from the service manual. Not sure what this means.

That's an early 400RB for sure. 

Enjoy it at low volume as it is. Maybe you don't need to mess with what's already cool?

Is this a multi-track recording with processing or post-production opportunities. If so, a pre eq DI would offer the most options "after the fact", in post.

3 hours ago, TimR said:

 

Strictly speaking this is wrong.

 

The volt is defined as the difference between 2 points when a current of one amp flows through a resistance of 1 ohm (although it's expressed as power dissipation 1Watt). 

 

ie the current flow causes the volt difference. Which is a very difficult thing to get your head around and why the water flow/pressure analogy is more correct. 

 

Think of it as lots of blue men on the left piling up trying to get through the tube at the same time, with fewer blue men running off to the right as they pop out of the restriction. While the blue man stuck in the tube gets more hot and flustered and red in the face. 

 

 

Anyway. As you were...

Actually, something is required for the current to flow, and that is the volt. Without a volt, and without a resistance, no current would flow.

It's like the "which came first, the chicken or the egg?" argument.

1 hour ago, moley6knipe said:

I’m still very much a large transformer sort of boy

You ought to try some of the newer SMPS/class D offerings, you might be pleasantly surprised...

4 hours ago, Stub Mandrel said:

If gear fails well out of warranty (7 years) there's really nothing to learn whatever the failure mode.

 

That's into the lifetime where random failures due to small manufacturing defects become possible. No matter what is said about the level and nature of usage, it has to be taken with a large pinch of salt as some people will be scrupulously honest and others may of thrashed it every night but not want to admit it. The have no way of being sure what the speaker has endured.

 

If BF get virtually no failures and they are all beyond warranty, then there is little reason to change.

 

If it was a 7-sigma, safety critical aircraft component it would be different.

2 hours ago, Chienmortbb said:

Agreed and if Airbus/Boeing/Lockheed made speaker chassis they would be carbon fibre. I also agree that 7 years is not unreasonable for a speaker although many will go on decades longer.

With the benefit of hindsight, I am in the unique position of being able to evaluate the reliability and lifespan history of many of my speaker and amplifier products. Speakers, when powered reasonably can last a virtual lifetime. We have many customers that have used speakers that are 20, 30 and 40 years old without a single issue and they are still perfectly fine. I had plenty of (pro level) PA speakers that I used in a touring environment 4 or 5 nights a week that lasted 20 years without any work necessary and continued to work fine for years after they were sold. All of our speaker products came with a 5 year warranty too, so 7 years is not well out of warranty and I would be horribly disappointed in me designs only lasted 7 years... that's a shameful expectation IMO.

Bass amps generally last 10+ years without attention but I am now seeing bass amps in after 15-20 years of hard use that need refurbishment. It's not the SMPS and Class D part that needs work, it's everything else that suffers the wear, tear and handling accidents. Out of a hundred amps a year that I see through the shop, I replace maybe 2 or 3 power modules. So much for the urban myth that "all" modern bass amps are unrepairable/unservicable. 

54 minutes ago, Chienmortbb said:

Are those the ones that make Amp Techs have nightmares?

Certainly those who are under-qualified tend to struggle, but qualified pro techs generally don't have many issues. We have factory techs that can  turn around 4 or 5 amps a day (depending on the problems of course), but they are excellent and good troubleshooters too. 

It's no different than for any product, the better qualified the tech is, the easier it is to fix. When I work on class D bass amps, I typically spend less that 1 hour on each amp. I find them easier and quicker to repair than my older class AB/G/H designs.

7 hours ago, Woody1957 said:

I get your point, but don't forget the bass players on this forum who have years of pro/semi pro experience, but without the so called technical knowledge that have witnessed otherwise....

Don’t forget that sone of us have designed these products commercially for decades and have a much larger view of the results of “player versus speaker” interactions. 

Sag is both measurable and subjective. It can be responsible for perceptions that are at odds with what’s really happening. Some of it is related to “perceived compression” and some is due to distortion harmonics that are generated. For some players this is good, for others it’s undesirable. 

8 hours ago, Dan Dare said:

It seems we're starting to strain at this. Those with years of expertise and experience, such as Bill, Aged Horse and Stevie, have given good advice above, which should be all we need.

 

To summarise, don't abuse your gear, ensure it matches (within reason - a 1000w amp with a 100w cab is almost bound to end in tears, but smaller discrepancies are fine as long as you are sensible) and that you use it within its specified limits.

 

Accept that drive units, as mechanical devices, are going to wear out/fail on occasion. Even electronics components don't last for ever. C'est la vie.

Reasonably powered, a quality bass guitar driver shouldn't wear out for many decades. Accidental damage and defects are a different matter of course.