agedhorse

Are you looking to play bass full range through it or as part of a biamped system?

From a casual glance, it looks like there's no way to defeat the low pass (high cut) filter that's part of the crossover on the sub itself. That's not going to sound very good as a full range speaker.

2 hours ago, eude said:

That's very interesting.

Does that mean that, with advice a Class D based amp could potentially be upgraded?

Newer modules are way more efficient and potent as far as I can tell...

Not so much upgraded as repaired/ replaced. One of the challenges in all amps is insuring a source of parts necessary for repairs 5, 10 and 20 years down the road. In some cases it may not be worthwhile to repair a 20 year old, but in most cases when the part is available it’s cost effective to do so. If the part is proprietary and unavailable then you don’t have that choice.

Since their marketing slighted competing products using ICEPower modules, let me provide an alternate perspective.

Some designers (me included) use ICEPower parts because of their long established history of both high performance and high reliability. The modules are typically supported for many more years than proprietary designs. This means that customers have more options for servicing their amps later in their service live.

For example, power modules are still available (I stock large quantities too) and currently being manufactured for every class D amp that I have designed, going back 20 years. This is generally not true for proprietary designs. 

13 hours ago, thisisswanbon said:

Thanks for all of the info!  I've tried the speakon, and FX loop fix but alas it made no difference... I've had it repaired a couple of times in the past for dry joints and scratchy pots, so I've decided it's time to upgrade and have a Mark Bass Little Mark vintage 1000 coming.  I've tried to warm the GK up for years, so seems a good time to change tack.

I’m going to suggest that maybe it was never repaired correctly the first time… in general these are pretty reliable amps until under-qualified techs start struggling with them. 

If this is the case, it’s likely that the noise was external to the amp, possibly entering through the power source. Another possibility is that the noise is from a cell phone, wireless router, Wi-Fi device entering the signal path post master volume control (unlikely but possible).

I thought I would let this play itself out, see what kind of armchair (or chesterfield) suggestions bubbled out of the primordial ooze. 
 

In the hundreds of these amps I have serviced and supported world wide (out of tens of thousands built), I have seen exactly 2 cold (dry) solder joints. Why is this? Because the flus chemistry and solder alloy used, combined with the double sided PCBs with plated holes, this is the most reliable way to build an amp, backed up by a matching history of less than 1 ppm wave solder joint failure. That’s probably the last place to look.

Unless you are familiar with proper safety procedures, don’t go poking around with anything inside an amp. 
 

Now, when you say the noise in unaffected by the volume knob, WHICH volume knob… there are 2 channel volume controls and a master volume control.

Does the noise change when you tap on the chassis? You can leave the cover on for this.

dies the noise go away when you plug a 1/4” (6.35mm) plug into any of the 3 effects returns? 
 

by doing this, you can eliminate 1/4 of the amp at each step without even opening the amp up.

Do not spray anything, anywhere in the amp, that just makes things more expensive down the road.

Great post Phil.

I have read engineering articles about the use of bamboo alone and in conjunction with conventional wood in compression laminated beams of various cross sections. The results were promising, especially for longer spans. 
 

I don’t think the weight saving alone makes it a structurally beneficial material for a plywood substitute, but possible as a face lamination for its surface properties.

I looked at the "Natural fiber" promotion and immediately thought what a good advert campaign this would make for a laxitive... combine with heavy bass guitar and things are guaranteed to move right along

5 hours ago, Phil Starr said:

It's so hard to be certain of the lifetime environmental cost of any timber products. US and European standards are pretty good and reasonably well controlled, though conservatives both sides of the Atlantic have cut back funding for inspection and enforcement agencies. Italian Poplar is to be trusted I think but for us over here it is more complex. Most of our 'Baltic' birch is Russian and only the outer plies are birch. A lot of 'Poplar' is made in China and is cored with either Populus yunnanensis or Eucalyptus deglupta and faced with Eucalyptus grandis or other hardwoods that may be sourced from elsewhere in South Asia. If you are a manufacturer buying in bulk it's reasonably easy to track back your timber but it's harder if you are buying a single sheet from the local hardware store.

 

Bamboo looks to be a fantastic resource as it grows to maturity in 4 years or so and can be continuously harvested as the roots remain, a bit like the old coppicing system with hazel and chestnut, or more accurately like mowing very long grass. It will be interesting to see what they do with the waste (about 70%) what inputs are needed to maintain the growth and what problems large monocultures bring. I'm not cynical about this and almost any product made by photosynthesis has to be better than mining or manufacturing. I'm with you in recognising that FSC certified timber is already a 'green' material. I'm sceptical that some of the green hype over bamboo might be a little overdone. The devil is in the detail.

Agreed. Due to our size, we obviously have a significant system in place to track both the source and composition of the woods used in cabinet construction, in many cases this is not true and you get what you get (buyer beware). We use so much of these products that it's also in our interest to be sure that we are receiving what we are paying for.

CNC grade materials have different composition tolerances, the core plies are more uniform and the face plies have a guaranteed minimum thickness. The plies are usually thinner and there are more of them too, resulting in less warp and twist. For high volume precision production, this is critical because the reference for the cutter is off of the top surface of the material and if the thickness varies, this affects the depths of dados and rabbits, plus any other joints (like lock-miters) the cabinet may employ. The cabinet shop can go through more than a hundred (4' x 8' equiv.) sheets of plywood in a single day, it's not practical to struggle with pieces that don't quite fit together. 

The advantage of CNC grades is uniformity (thickness, glue lines and lack of voids), the primary disadvantage is cost... but the end result is that it costs less to assemble and finish using CNC grade so in the end the cabinet is a much better product for not much more money. 

The accuracy for CNC parts milled in production is typically between +/- 1/64" and +/- 1/32" resulting in cabinets that have tight, square joints. As you can guess, for the finger joints used in some of our natural finish guitar cabinets, this is essential or the parts simply won't go together.

Here's an video that shows cabinet production:

I've used a large amount (tens of thousands of board-feet) Italian Poplar (CNC grade mostly) for many years, haven't had any issues with softness or structural properties. 

11 hours ago, MichaelDean said:

Compared to about £115 for poplar ply in the same thickness (admiteddly from the first website I found), I don't think that is too bad for a more renewable material that is also FSC certified (at least from here it is). Yes, it's a 74% increase in the material cost, but that works out to be about £45 extra for a "decent" sized cab (I'm guessing two 12" cabs from a sheet that size?). It is also arguably a more attractive ply with a stain/oil finish and more hardwearing. Plus, if you can get away with it being thinner, and then making the cab lighter, that feels like a win all round to me for a small premium given the expected lifespan of a cab.

 

I'm not that far away, I'm almost tempted to say if you buy a sheet, I'll take the other half. Not sure how that would go down with my wife though! Still haven't made the cover for our consumer unit despite having all of the materials here... 😅

To be clear, most Italian Poplar is FSC certified:

https://fsc.org/en/newsfeed/fsc-italy-publishes-national-forest-stewardship-standard

2 hours ago, paul_5 said:

Dumb question - I just use one cab in my rig, so not sure about this - on a 4 pole Neutrik socket/jack could you not use +1 and -1 for one cab and +2 and -2 for the other?

This is SOMETIMES done on pro audio amps specifically for bi-amp applications, it's important to recognize when this is done (it's always specified on the back panel legend around the jack)

It's not a good idea for general bass guitar applications, a few manufacturers do stupid (non-conforming) things with pin 2+/-, and there are also (just) a couple of manufacturers that use NL2 jacks which will not accept an NL4 plug.

The NL2 or NL4 splitter cable is the best solution for this with no downside (other than if you forget your cable)

I see a fair number of problems caused by knock-off Chinese SpeakOn plugs. Sometimes they can damage the mating jack, resulting in costly repairs.

51 minutes ago, Downunderwonder said:

I think for the purpose of waving a dB meter in front of a guitard to get him to stop with the godforsaken racket, an A weighted meter is useful.

Heavily weighted with lead perhaps?

1 hour ago, Bill Fitzmaurice said:

Even at 125Hz 'A' weighting is 20dB off from actual. To bring that into a more meaningful context 20dB is the difference between 10 watts and 1,000 watts. 😳

Yup, and assuming that the comparison results using A weighting are "good enough" can result in incorrect, inaccurate (by a mile) conclusions. When somebody bases their opinions as "fact" because of meaningless data, yet they believe with all their hearts that it's uncontroversially true, that's getting awfully close to the definition of blind faith IME.

30 minutes ago, Steve Browning said:

I have a Walkabout 15 and have to agree. A flip-top on steroids.

 

I have a spare Subway 15" 8 ohm speaker and am tempted to install that and see how it works with the TT-800. I'd think about getting a WD-800 to power it.

I don't recommend it, the tuning is quite different on the Walkabout. If you do try it, de-rate the Subway driver to about 250-300 watts RMS or you could damage it.

8 hours ago, silverfoxnik said:

Thanks for the feedback, Folks! 

 

Point noted about the Walkabout especially @Beedster... 

 

And just to be 100% clear, is that also the case with the Big Block 750 @agedhorse? 

Yes, and many of these parts are becoming difficult (or impossible) to source because the manufacturers are discontinuing them. 4 ohms is what I would recommend as a safe minimum load. 

1 hour ago, Chienmortbb said:

This it bullshine. Just like amp manufacturers quoting THD + N at 10%

No, it’s real world performance definition specifications. The old way of defining Xmax would often result in THD numbers even greater.

There are also speakers designed for increased THD numbers (and specific ~ratios of the harmonics) for coloration or texture purposes. This is seen sometimes in the bass world (think older Ampeg SVT 10” drivers) but also very often in the guitar world). 
 

Regarding amps, you might be surprised at the THD numbers that are generated within the preamps of many popular bass amps, 5% is common, and when overdrive effects are used, that number can quickly jump to over 20%. How an amp is used should go hand in hand with how it’s specified.

Very early on, they were ok at 2 ohms but we had a difficult time getting consistent MOSFETs and through 2 changes of manufacturer it became obvious that they were struggling with the process as well. This resulted in higher than acceptable failure rates into 2 ohms, so we discontinued the 2 ohm acceptable rating. 

Because these amps are quite expensive to repair (and difficult to get parts) , I would not recommend 2 ohm operation on any of the MOSFET amps. The Subway amps however, are fine with 2 ohms, using the 2 ohm mode switch on the back.

2 hours ago, Stub Mandrel said:

 

The fundamental problem is that most amps don't have that sort of data available. 

 

Even 'responsible' manufacturers don't give totally transparent information.

 

For example Marshall and Orange give reslistic ratings, but for two very similar designs Marshall rate 50W and Orange 30W, because they measure at different levels of THD. You won't find this in the manual.

In a bass/guitar amp, depending on the player’s gain structure and intent, a great deal of design effort is placed on the non-line as aspects of the amplification. This means intentionally developing distortion components (spectrum of fundamental to the multiple harmonics), alterations to the dynamic response transfer function, and how entering into and out of these non-linear regions is handled by the design elements. 
 

This makes specifying power versus THD difficult because there are multiple curves overlapped that describe this behavior. 
 

Good designs sound good to players and delivers the required power under the conditions each player uses.

18 hours ago, chyc said:

To me it's one of those things where, when asked "what is natural?", the answer would be "I know what it isn't." I own a TV, of a brand that funnily enough has come up in this thread already. I cannot tell the difference in volume once the volume slider passes around 1/3 of the way up. There's nothing natural about that. Whether musical instrument manufacturers do anything quite as egregious as that I cannot say because I've never owned one that does.

Some in fact do.

2 hours ago, chyc said:

Even then it's not simple. Different amps have different scales on their volume. Some are linear in volume (I think EA is a manufacturer that springs to mind), some are more logarithmic. Why does this matter? Well, if you have otherwise identical amps at 50% on their volume dial, then the logarithmic one will sound louder because it's actually at something like 80% of its maximum power.

 

I'd call that a marketing trick for just such a scenario as you describe, but apparently some people like the non-linearity of their volume dials. To each their own I guess.

Marketing departments certainly like this, but apparently many players do feel that an amp's more powerful that way too. As players mature, they tend to grasp the benefit of linearizing the rotation and scaling of the range of the control though.

5 hours ago, dmccombe7 said:

Understand what you mean. I was hoping for a simple jack % Jill explanation but its far more complex than i ever imagined.

I reckon designers and manufacturers are waging a "Dark Strategy" to confuse the masses................its working 

Seriously there's far more to it than i ever imagined.

All credit to the companies that are doing it right...............i just dont know who they are ? 

Dave

A simplistic explanation wouldn’t be accurate. It IS complicated.

5 minutes ago, stewblack said:

I can't do anything about that. If I've had a Behringer head never let me down for over 20 years and a succession of Markbass, Trace Elliot, Ampeg (to name a few) crap out on me, I'm bound to be wary of throwing any more money at 'names'.

Human nature innit?

Go with your gut then.

4 hours ago, Chienmortbb said:

Do you know of a 12" that can really exceed 400W RMS at low frequencies?

Yes, but for bass guitar especially, the mid characteristics and sensitivity are very important also. There is a tradeoff between raw power handling (including both thermal and mechanical) and sensitivity, mid extension, cost, and often there is a need for a larger enclosure size. With the number of players that would be ok with these tradeoffs being quite low, it's not really all that viable (IME anyway) for a commercial product. 

At this point, 400 watts RMS at low frequencies (say down to 40Hz) appears to be about the sweet spot. If you were to take such a driver and high pass the signal to 50Hz, than the same driver might be ok to 500W RMS, but that's a mighty bold assumption for a manufacturer responsible for warrantying their speaker to make with confidence that it won't come back to bite them in the butt (bum). Being wrong on such an assumption could result in extraordinarily high warranty costs.