agedhorse

Just now, agedhorse said:

Yes, the amp will drive 250 ohm headphones without any difficulty, but the vast majority of players use lower impedance phones and by far the greatest number of questions (and issues) is with the lower impedance phones. To refresh my memory, I checked the top 30 selling headphones and ~90% were 60 ohms and less. There were just a couple over 100 ohms.

 

Just beware that in general, high impedance phones that do not get as loud at low frequencies The amp's headphone output can drive them beyond their capability without them getting as loud as players expect.

5 hours ago, BassmanPaul said:

Let's ask the man himself: @agedhorse

 

 

Yes, the amp will drive 250 ohm headphones without any difficulty, but the vast majority of players use lower impedance phones and by far the greatest number of questions (and issues) is with the lower impedance phones. To refresh my memory, I checked the top 30 selling headphones and ~90% were 60 ohms and less. There were just a couple over 100 ohms.

Just beware that there are quite a few high impedance phones that do not get as loud at low frequencies, the headphone out will drive some of them beyond their capability without them getting as loud as players expect.

8 hours ago, Old Ozzie Guy said:

Maybe I can explain myself abit better. I have a Boughton active -12 db to b set 45 Hz, then I have a gob -3db passive set to 70 hz, 

Therefore "cut off" begins at (approx)70 hz at 3 db per Oct, while at 45 hz increased slope of 12 db per Oct.. soft then harder knee.. 

I hope this explains. 

To clarify, a first order filter is 6dB/octave and a second order filter is 12dB/octave.

16 hours ago, Marcus Cornall said:

Thankyou agedhorse.I know from reading this and other forums how great your experience is,and why. Deepest respect for taking the time to respond.

 

I have nothing between the bass and the amp.

I did wonder if it was a matter of the tweeter being capable.ef 'unnatural' relative  amounts of treble. I presumed that to get a 'flat/balanced relative amount from the woofer and the tweeter; I would have to turn the tweeter fully up.

But from what you are saying it could be then that to get the relative balance I should turn the tweeter down some.

And someone with a similar issue on a forum was also told that treble frequencies don't take as much power to amplify and maybe that's also part of this. 

I haven't had an amp this powerful before either so maybe am not used to the relatively higher starting 'noise floor',if that's the right term.

 

A tweeter is typically about 10dB more sensitive than the low frequency section, so with the tweeter level control fully up (assuming that's the only attenuation), there will be a 10dB bump in the high end compared with the rest of the speaker's response.

Mid 90's.

Be sure that you set your speaker to 8 ohm mode (assuming it's switchable between 4 and 8 ohms)

I too would recommend a second speaker identical to your first.

Any electronics before the amp (pedals and active bass for instance) can contribute to a higher than ideal noise floor. 

If a speaker has a tweeter sensitivity that is significantly higher than the low frequency drivers, this can result in the perception of more hiss than you might otherwise expect. This is common with tweeters turned up to "bite your head off" level that happens with some cabinets. The brighter the tone, the more noise present.

8 hours ago, Ralf1e said:

OK. Sorry to all about insulting all your active basses as well as  my own. What I should have said was a great many makes of wireless systems cause hum or whine with active basses which in hindsight is more accurate than my original post.

This too is inaccurate and incorrect. Maybe a FEW models of wireless, but certainly not many or great many.  Out of the hundreds I have set up, maybe one or two.

12 hours ago, SumOne said:

There can be issues with active basses and wireless systems due to the ground wiring, it must happen often enough as Boss have taken the time to draw diagrams of the issue and solution and put it on their website:

 

https://www.boss.info/global/support/by_product/wl-20_wl-20l/support_documents/cf786345-1dd0-46c3-a2ac-350bfb4a8104/

 

 

 I used the Boss wireless for the Waza Air headphones with an active Bass and there were no issue though.  

That’s not an active bass issue, it’s incompatible wiring/connection with that particular product.

I’m not sure why they chose to use a TRS plug on the transmitter, but it’s unusual and maybe even unique.

I have worked with hundreds of players, interfacing wireless systems (mostly at the professional level, with pro products by Shure, Sennheiser and Audio Technica) without any problems.

7 hours ago, Ralf1e said:

Most active basses cause hum or whine with wireless systems

They do? 
 

I haven’t seen this to be the case, in 40+ years of being in the business. 

Active basses can drive lower impedance loads. This includes long cables because the capacitance reduces impedance (via capacitive reactance) as the cable length grows (for bass guitar it’s typically not a big issue up to about 10M).

Most wireless transmitters have an instrument input impedance of around 1M which is compatible with all pickups, active or passive.

Surrey Amps in the UK are qualified to troubleshoot and repair Genz Benz products, I can provide factory support and parts directly to them.

8 hours ago, ukbassboy said:

I do appreciate that there is no one better qualified than you to repair the GB amps, but sending his amp to the other side of the world to get fixed may not be particularly appealing given delays and exchange rate costs. I suspect he's just looking for an option to repair it quickly in the UK rather than disrespecting your knowledge, hence looking for an answer on here also. 

I never suggested he send the amp to the US, I did suggest that he find an experienced, qualified service tech to troubleshoot the actual cause.
 

There’s a lot more than the switches involved in the filter switching. In this series of amp, I have seen maybe 1 or 2 bad in the last 10 years. I’m trying to help by providing good advice.

What is the primary current rating of the transformer? I'm about 99% sure it's well under 250mA full load at 230V, meaning that if there wasn't a problem with  the transformer itself before powering it up with the higher value fuse and there was an issue in the circuitry downstream, you now have another problem in addition to the original fault.

This is why DIY repairs, and repairs by techs who are under-qualified for the work they are attempting end up the way they do.

I already answered your question on Talkbass. 

Did the tech check to be sure that the measured input current was less than the transformer's rated input current x0.65?  This would confirm that the load was safe for the transformer.

First of all, that thermal protection isn't going  to do much because it's on the outside of all of the wrappers so it will be measuring quite a bit less temperature than what's really present on the coil. The coil can overheat without the core overheating on a small part like that. Is the coil really overheating? Only a proper forensic evaluation (called a transformer "necropsy") will determine the true cause of the fault.

The fuse should be slow blow (or time lag) and sized at a minimum of 1.25x the rated continuous primary current. For a toroid, it's possible that the inrush current (which is higher than for an EI transformer) might require an adjustment of this multiplier from 1.25 to 1.5, but this needs to be done after verifying that the transformer is not overloaded.

There must be enough primary turns for the core material to prevent magnetic saturation, this design parameter is voltage and frequency dependent. If the transformer saturates, the primary current will be higher as will be the heating effect.

Now for the real stuff... do you know what the input current is to the power supply. It looks like a FWB input capacitor filter. The transformer needs to be designed around the derating factor for this particular power supply topology. For this configuration, the rated current of the transformer multiplied by .65 is the usable current for the circuit being powered. It's possible that somebody forgot this when designing the power supply.

There's more to solving this problem than replacing a part, you need to know what the maximum current of the circuit is and work backwards with all of the necessary design and derating factors to be sure you have a viable solution. 

21 hours ago, ukbassboy said:

Thanks for swinging by @agedhorse, I'm a big fan of your work on the GB 12.0 which has provided me with years of sterling service so always enjoy your input to our forums!!

The D-800 does look like a very nice amp, but from what I can tell availability on the new or used market in Europe is next to non-existent, so not something I can readily consider. I also feel like the form factor more closely resembles my 12.0 so would be more a replacement for that (if it ever dies and you can't fix it!) rather than an ultra compact option. 

It's quite different from the ShuttleMax amps and about 1/3 the size.

I would expect that you will start seeing Subway products in Europe in the next 3 months or so, we are finally digging ourselves out of backorders and parts sourcing issues. Crazy times we are living in.

Subway D-800 is 800 watts into 2 or 4 ohms, the aux input is suitable for using as a power amp input.

On 23/02/2023 at 09:48, greentext said:

its true, i dont see it being much better then the 400+ myself, but ive seen so many pictures of Les Claypools touring rig from the mid 90's using the 400+ and the M-2000 in conjunction so i've always wanted to try that set up for myself just to achieve the Pork Soda, Tales from the Punchbowl era Primus tones. Just for my own selfish exploration it would be a lot of fun haha

Recent tours with Primus had Les playing a Subway D-800 rig w/ Subway 112 cabinets, slaved for 1600 watts rms into 4 x 112's. 

I don't know what rig he is using for the new FFFB tour that's going out this spring. 

27 minutes ago, BassmanPaul said:

T add to Bill's comment stack the cabinets with the drivers vertically aligned not side by side. They just work better that way!

 

Sometimes, sometimes not. It depends.

7 hours ago, dmccombe7 said:

Sorry to hear you're having problems with a Mesa amp.

I'm more surprised you managed to get one in UK with Mesa not supplying outside the US until later this year hopefully.

Hopefully you get it sorted.

Have you asked Andy @agedhorse if he can help. He's a gear guru as far as i'm concerned. Always very helpful and seems to be a very nice guy too.

Dave

We’ve shipped a lot of these amps and haven’t seen any problems. I have no idea what the issue may be. 

3 hours ago, fretmeister said:

User error... designer error... it's all the same  

Probably a good example of two wrongs not making a right...

15 hours ago, Downunderwonder said:

Either you're having a senior moment also or I have no idea what's going on. Surely it's 2 ohm mode switch time with 2 times 4 ohm cabs = 2 ohm worth of cabs?!?

1 hour ago, fleabag said:

 

I thought it was Mesa 800, plus to two 4 ohm cabs, and the 'to' was a typo

14 minutes ago, Spewy said:

Just to clarify, This is a 800+ Amp, it states in the manual that the outputs from the amp are in parallel. 

 

I am running a single 4ohm cab from each output. Two cabs in total.

Are you saying the switch should be set to 4ohm?

 

Sorry to be thick , but that seems to contradict itself. However I really appreciate your help🤣👍

 

Sorry guys, that was a horrible typo. It should have been 2 ohm mode not 4 ohm. 

On 12/02/2023 at 02:57, Spewy said:

Guys , I’ve just had a senior moment.

 

I’m running 2 410 ohm cabs. One from each of the SpeakOn outputs from the amp. Thinking they were separate circuits I’ve had the ohm switch at 4ohm. However, having just read the manual it states these are in parallel and if I’ve got this right I should be switched to 2ohm?

Is this correct, and if so , how I haven’t blown anything is beyond me🤦‍♂️

Correct, set the amp to 2 ohm mode (NOT 4/8 ohm mode). This is covered in detail in the owner’s manual.

This is why we put so much effort into the protection circuits.

[edit for bad typo]

34 minutes ago, BassmanPaul said:

Single coils are notorious for picking up noise. This is what I was getting to with my post. You might be able to resolve the problem by screening the control cavity and under pickup area with copper self adhesive tape. It's fairly easy to do. 

Just be sure that the shielding material is bonded to signal ground at the output jack, otherwise it can make things worse.