agedhorse

13 hours ago, Phil Starr said:

We were measuring the output of the amplifiers only. No speakers were involved so none of these concerns would be applicable. I wonder if you are confusing these measurements with the speaker shootout I carried out at the same meet-up.

Yes, in part because speakers were being discussed within this thread as well and the combined measurements of speakers and amps tend to go hand in hand with these discussions.

On 16/10/2022 at 04:01, Phil Starr said:

I'm looking at using REW which is free and pretty powerful. It's also fairly well supported and there are plenty of instructional videos on You Tube. Any 2 in/2 out interface should work and I'm probably going to use my USB mixing desk. REW lets you do a calibration plot so if the interface does have any artefacts they can be allowed for. There might be a problem with connecting some BTL (bridged) amps to earth but most DI boxes should let you fix that. Currently John is doing his measurements with an oscilloscope and other software. I'm not sure if that is an issue, if they lead to different results then we can investigate.

 

The only other issue I can think of is all agreeing a protocol so data can be collected and compared. For measurement I think 20-20kHz measurements at low power makes sense and REW allows you to centre results at 0db. Displaying results as a graph is useful but a table summarising results would also be good as a quick reference (-3db points, frequency range, rate of roll off, centre and size of any frequency anomalies) Ideally it would be good to make the data files themselves available to anyone who wants them. I've no idea about how they are stored.

 

I'm no expert on this so any help/suggestions are very welcome. We might need to take this across to another thread if this takes off

 

Yes, you want  to be VERY careful with bridged amps, and most class D amps are internally bridged. Most are not protected from a short between 1/2 of the output bridge and ground, this is not the normal way a fault occurs on a speaker out, the protection typically looks at either 1/2 of the bridge or (indirectly) the difference in current between the two halves of the bridge. Also, the level is (or can be) higher than many scopes can handle.

This is a common way folks who are new to testing, or are new to electronics, or do electronics as a hobby destroy their laptops or interface (depending on where the interface is located). The fault is large enough that it typically lets the magic smoke out pretty instantaneously and catastrophically.

I've been testing class D amps professionally for over 20 years, there are a lot of necessary tricks to get good results and data, especially power and THD data (depending on the modulation scheme and output reconstruction filter type). It's harder than it looks, especially if the numbers need to be accurate.

On 14/10/2022 at 23:28, Phil Starr said:

 

 

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We had hoped to measure a lot more amplifiers. There were plenty there at the bass bash but we simply ran out of time. The result for the Gnome was so unexpected that we spent precious time checking everything over. I had to set up and run a speaker shootout in the main hall and couldn't act as gopher for John.

 

Anyway it was an interesting experiment I think we'll repeat and try to grab more data on other amps. There is free software to do this so if you have a simple two in and two out interface you should be able to do this at home so maybe a few of us could work together and build a database

Beware that it's MUCH easier said than done.

It's common for folks who do not do this all the time, with a setup that allows for anechoic measurements 1/2-space measurements (1/2-space is most commonly used for stage speakers because that's the closest approximation of the real world environment) to have errors of between 3 and 6dB SPL. Then they go proclaiming things that are simply not true because they have drawn conclusions based of incorrect and/or inaccurate data, which is unfair to everyone.

What is magnetic plywood?

8 hours ago, fretmeister said:

To be fair that says “Power Amp Tubes, Class D Power Amp”

 

I can see that being confusing to someone who doesn’t know that a Class D is not a tube amp.

 

@agedhorse That is a bit misleading. I’ve been playing for 36 years and I would wonder which of those 2 things was wrong as I know one of them must be. But inexperienced players may not realise there’s a contradiction there. It should really say “Power Amp Section” or some other description that doesn’t mention tubes.

You have to remember that we are primarily a tube guitar amp company and the marketing/website folks use a template that describes the output stage by what tubes are used (or no tubes at all, which would then be in the case of all the new bass amps "class D" because nobody uses power amp tubes in class D amps). When we used class AB output stages in bass amps, it was described as MOSFET - class AB

It's assumed that players purchasing this level of equipment will understand this, and have done their homework by doing at least a little bit of research. There are numerous reviews, videos, forum discussions and even the owner's manual is available on line. In the back of the owner's manual is a tutorial on what class D is and how it works. We even discuss switchmode power supplies.

I don't think it's misleading, and in fact in the entire 8 years of the Subway line this is the first time this has come up.

I am going to respond assuming that you have grossly misunderstood the manual rather than being intentionally disrespectful. 
 

The manual is crystal clear and accurate in its description of what the amp is and how it works. There is also a block diagram in the back that clearly shows the signal paths throughout the amp. There are also extensive specifications published at the end of the manual.

The TT-800 is a 2 channel preamp, with a Boogie channel and a Subway channel. Both channels are tube driven and have tube gain stages. There is switching between the two channels, which then drive an 800 watt RMS class D power amp. 
 

If you are looking for an overdriven tone, I would suggest the Boogie channel to start, be sure the gain switch is in the high gain position, start with the channel master at the 9:00 position, all of the eq controls at noon, the high pass filter set to the 10:00 position, and turn the gain up until you hear the overdriven tone. Once you get this, use the channel master volume to set the overall volume of the overdrive tone. This is a starting point.

If you have a low output bass or the setup of the bass had greater pole clearance than stock, or you have a light touch, you may not get as much overdrive as another bass with higher output. This channel has roughly the same gain structure as the Bass 400.

That said, if this is confusing to you, or you continue to have difficulty understanding this amp, it simply may not be the right amp for you. It’s not as simple as other amps on the market (including the other amps in the Subway line)

Another thing you can do is follow the sample settings page, but for overdriven tones, these settings were developed with specific bass types more commonly associated with overdriven and distorted tones.

Hope this helps.

11 hours ago, fretmeister said:

Definitely do not use it on a TT800.

 

As with all solid state power section amps the master volume is easy to control, and any preamp drive will be controlled by the gain control.

 

As said - they are for valve power sections ONLY, and the number of bass amps with valve power sections is really small, and even then the highest capacity attenuator I've ever seen for a guitar amp is 150W, which is far lower than you'd need for a big bass amp.

 

The main reason why you don't see them for bass amps is

 

1: Because even valve power section bass amps really don't need them

2: There's no market for them.

 

 

Correct, these amps are WAY too much power for any commercially available power attenuator on the market.

Also, some attenuators are NOT isolated from common signal ground, which means that on a bridged (BLT) amp, it's possible to short 1/2 of the amp and damage it. No tube guitar amp has this configuration, so a common ground won't hurt anything (except may be a little noisy)

13 hours ago, Muzz said:

Could be worse...as I said, with the Walkabout I just drop the very bottom end out and use the Bass, Mid and Treble...the Mid is particularly nice...

The ShuttleMax was (and still is) a very popular model. Most players didn’t have a problem understanding it.

19 hours ago, rmorris said:

 

Depends what you mean by the design ? - of the circuit itself, its implementation on a pcb and how things are wired, the enclosure wrt shielding.

Type and position of the power supply is also a possible factor. Depending on the nature of the 'noise' eh hum / buzz / hiss / general "digital hash" etc...

All of the above. They are all different and more likely the cause of problems than the quality of the components themselves IME.

17 hours ago, uk_lefty said:

I'm no techy but when I've had cheaper pedals (Mooer, weirdly named stuff off eBay and Amazon) I've had unwanted pedalboard noise. When I've used Boss, Darkglass etc I haven't. I've always used a cheap power supply. I'm not drawing any conclusion to the exact reason except "cheaper components". If other people don't have these issues, great. 

Could it also be that the designs aren't as good?

It’s very unusual for the mute switch to fail. Possible, but I haven’t seen one in over 10 years. 
 

I believe I do have the 5 button footswitches in stock, do you have someone here in the states that could be a domestic shipping address? They are $75 USD plus shipping,

On 26/09/2022 at 00:59, Chienmortbb said:

Unless Aguilar are really screwing with the signal, that is wrong. ON this Video at just past 2 minutes you will here the Aguilar man say they use the ICEPower 250ASX2. That is rated at 500 watts into either 4 or 8 ohms. Now I have heard that you either love, or hate the sound of the TH500 but it certainly does not lack power.

 

500 watts into 8 ohms is immense  so long as your speaker sensitivity is not exceptionally low. I fact, many 1000W amps will only do 500W into 8 ohms.

 

 

Aguilar did derate the output of the modules, the rating is 250 watts at 8 ohms and 500 watts at 4 ohms to prevent OC or thermal shutdown. It's tricky to get more power out of these parts without really understanding what's going on under the hood, but if you do there's a ton of off sheet potential that can be exploited. I hold a US patent that specifically addresses this (and with this module specifically but the patent applies to the techniques which apply in general, which means that others couldn't use this approach without licensing in from the company we assigned it to.

6 hours ago, Stub Mandrel said:

 

My guessvis the psu is the limiting factor on power amp module replacement.

Nope, all the parts of the module factor into this. In fact the power supply is likely the less likely part.

It’s not uncommon to get AC mains frequency feed-through noise on generic power supplies. Can you return it if it doesn’t work out?

On the D-800, use the Aux input and be sure to use a tip-sleeve cable, this will bypass the D-800 preamp.

When dealing with servicing, generally there's either a declaration or specific harmonized code for a product being returned for factory service when you send it to the factory, and they will use a similar code or declaration when returning it to you. If there is a charge to you, then there may be duty and/or VAT on that charge but not on the entire value of the amp.

19 hours ago, Downunderwonder said:

It's common these days for class D amps to consist of a pair of amplifying units hooked up in bridge fashion to a single output. This leaves one of the output legs at case ground so grounding the other puts the amp into instant loop of death mode.

Both of the two speaker output terminals are not at ground potential, so when one of these terminals (say the shell/barrel of a 1/4" plug) touches ANY ground including the chassis, it shorts that amplifier to ground. Depending on how the protection circuit is designed, it can damage one or both channels pretty much instantly.

13 hours ago, King Tut said:

You live and learn! I often use a speakon to jack cable to hook up to a cab, am i in danger of imminent electrocution? If that’s the case, I’m surprised there’s not a warning in the manual - after al they’re not shy of warning us not to eat the product, immerse it in water or use it on the bank of an active volcano!!

The shell/barrel of the 1/4" plug is not at ground but is a driven connection. On high powered amps this can be a shock hazard, though generally you won't get injured unless you are surprised and jump backwards into something else. On very large amps, the shock can certainly hurt.

10 hours ago, Downunderwonder said:

Always plug in the cab 1/4" first.

 

Always disconnect the power before unplugging the cab.

 

Nil danger unless there's a chance the lead can be yanked out midstream.

As long as nothing grounded (another cable plug that's ground referenced) happens to touch the shell/barrel of the bridged amp's output plug. Then it's a short circuit and the amp can be damaged.

It’s not 2kW rms like most other amps/brands are rated. 
 

From the AC input power and the calculations used by the safety agencies, it calculates to between 650 and 709 watts rms. I explained these calculations and then did them in another thread.

The version is not 94V0, that's the flame spread rating of the PCB!

This amp is difficult to repair, it generally costs as much to repair as it does to replace the main PCB, which is why Ampeg offers this as a repair part.

5 hours ago, dmccombe7 said:

Dont remind me of the TT800. 😂

For a few years it was my dream amp and may yet come into my hands when things settle down but at the moment the WB-100 has a tone to die for and i cant fault it in that respect.

Dave

Naaah, just correcting scrumpymike's post in the event that somebody reads it and is confused.

3 hours ago, scrumpymike said:

Just a few hopefully relevant comments based on my experience.

 

First of all, my R400 sounds good however the controls are set.

 

Second, the manual for my Mesa TT-800 with 3-valve pre also states that you set the master at 1 o'clock, tweak the gain switches (it's got 2 channels) to suit, then crank the master up if necessary.

 

Last but not least, if it's possible to get truly awful sounds from Leszek's new amp (which is pretty unusual with modern amps), he should include some sort of user instructions that explain what to do and what NOT to do. This is meant as constructive criticism btw 🙂

Actually, it does not say this in the instant gratification section. It says to start at 1:00 on the channel masters. It’s also a full 2 channel amp, so the master volume controls are used to balance between the two channels for channel switching purposes.

In the feature set descriptions, it clearly describes decreasing the channel master when using high gain settings and increasing the channel master when using lower gain settings.  
 

All of the controls operate as described throughout the manual, and provide the expected results. Features that are unique or unusual (like the symmetry control) are described in detail, which is why I always recommend to spend some time reading and understanding the owner’s manual. A lot of time and effort go into writing good ones. 
 

What does the Handbox owner’s manual say about the operation of the master control?

I posted this over on TalkBass in response to jb90’s comments, but I think it’s applicable here as well:

My feeling is that one benefit of a public forum is an open discussion of both the benefits AND drawbacks of a piece of equipment, as well as potential challenges in learning how to operate a new piece of gear. 

Everyone benefits from these kinds of discussions provided they remain civil and respectful. What is not cool is when the discussions evolve into accusations based on incorrect information leading to false accusatory conclusions.

Life is not all “glitter and unicorns”, there are going to be issues with any new gear. To avoid such discussions really do the community a disservice in the bigger picture IMO

On 31/08/2022 at 11:25, jb90 said:

He wrote about "lack of knowledge" because many bass players boost gain and left volume on very low levels. You can't get sound with tube amp set like that and you always get "farting" instead a good overdrive. With tube amp your gain is your volume knob and volume knob is your "overdrive level" if that make sense.  

This is simply not true in general. Tube amps do not have a problem with low master volume control settings unless that is an inherent part of a specific design, in which case suggests that a master volume control should not be included if it’s not intended to be used as such.

I’m sorry, since this is a bass forum I thought you intended to use the sub as a bass amp/cab full range.

For its intended use, as a pa sub under tops, it’s fine.

On 24/08/2022 at 23:25, skidder652003 said:

https://manuals.plus/hh-electronics/hps-115-active-subwoofer-manual

The cabinet cuts off between 100 & 200 Hz based on the crossover control. It’s unsuitable as a bass guitar speaker without a full range cabinet to cover above the HF cutoff of the sub cabinet