Burson BANG (inside pics, technical stuff etc.)

[lardyl]

So took the lid off as requested by Burson Support the big white 5W cement/ceramic resistor looks like it's seen better days, now a different colour/texture on one side. Is that some form of overload protection? Or is it the normal state for that component?

Presumably it is some type of protective resistor and the loss of one channel can be attributed to it operating? Also I suppose that there could be some other damage downstream that might not be fixed with a simple swap out of the resistor? Or am I being overly cautious??

 

[lardyl]

OK they looked at photos and suggested swapping the V5 op-amp for a V5i that I had bought from Massdrop.
This works at the moment. Now I have an excuse to play music for the rest of the afternoon for test purposes.....woot!

 

[lardyl]

OK they looked at photos and suggested swapping the V5 op-amp for a V5i that I had bought from Massdrop.
This works at the moment. Now I have an excuse to play music for the rest of the afternoon for test purposes.....woot!

More failure followed as the distortion began again after about 20 minutes of faultless play, followed by a volume change and clicking superimposed on the left channel. So something seems to have damaged the first op-amp and is probably doing the same with the second one. Not happy now. But Burson, to their credit, have been very prompt and helpful in their replies. Had very good customer service so far!

 

[restorer-john]

More failure followed as the distortion began again after about 20 minutes of faultless play, followed by a volume change and clicking superimposed on the left channel.

Well, at least it is living up to its name- going Bang.

 

[trl]

More failure followed as the distortion began again after about 20 minutes of faultless play, followed by a volume change and clicking superimposed on the left channel. So something seems to have damaged the first op-amp and is probably doing the same with the second one. Not happy now. But Burson, to their credit, have been very prompt and helpful in their replies. Had very good customer service so far!

Sorry, I missed your latest posts. That big 5W resistor is used as ballast, to lower the voltage between the linear regulator that powers-up the relays and the 12V PSU input. This should lower the heat from those linear regulators, so you should ignore that big ceramic resistor, because it's not placed in the signal path.

However, did you managed to make it work fine? If not, then swap the input opamp with JRC5532DD or a similar 5532 opamp (not Signetics purchased from eBay!). V5i is not a good use in this amp, not sure about the V5. Use the lowest gain on both channels (check the output volume and leave the gain switch in the position where the sound is lower in volume) and see if the issue goes away.

You could also use a DSLR with a 1:1 macro lens or a prosumer camera with a decent macro lens, and check for possible soldering issues, like cold joints. Usually, when a package travels between several countries, there are many shipping companies involved; that means the inside electronic parts and the soldering joints will get really "stressed" by extreme "G-forces" caused by the handymen/employees.

 

[Panelhead]

What are the heat sinks for the LM3886TF? Normally there is a hefty chunk of finned aluminum to dissipate heat.

 

[Panelhead]

Got off my lazy and looked this product up. Looks like the LM3886 are using the bottom plate of the amp chassis as heatsink. Not good if run hard.
The distortion heard was the National Semi SPIKE protection kicking in. There to let you know the power chips are overheating.
One real positive is Burson website lists price as 199.00 USD.
Would like to see the standard 5w 1K sinewave to see noise floor, distortions, and harmonics. Square wave does not tell as much.
Output impedance listed may be wrong. Most circuits of this type (gainclone) are much lower than 1.5 ohms. If correct damping factor is 5.3.

 

[trl]

The voltage is not so high and even on 4 Ohms speakers the heat dissipated will not kick the protection off. If using positive air pressure desktop computer it will keep the bottom plate of BANG below 50C, already tested this.

So, it's all about what you need to do with it and, if you take some time to test the dissipated heat versus the output power, then you should be able to find your "sweet spot" on the output power, based on your scenario.

For me square waves is the most important test for an audio amplifier, especially if done between 10Khz-20KHz.

I couldn't measure any output impedance with my instruments, but I'll see if I'll have time to re-measure it. I can usually spot an impedance of 0.5 Ohms or higher, but feel free to consider Burson's specs then.

This amp is the cheapest gainclone done by a reputable manufacturer that includes PSU, case and everything else you might need. You can find it on eBay for 150 USD or so.

 

[lardyl]

Weirdly enough I had lots of too-ing a fro-ing with Burson and I sent the op-amps back to them over the months since last May!

I didn't reply to their odd email and in the end (all sorts of COVID problems at both ends) they have sent me another (re-con I suspect) Bang unit with the V6 Vivid installed which arrived this morning and is a bonus as it includes the PSU, interconnects and the rest. I think their manufacturers were unable to source a new main board (their preferred solution) - they also offered a nice discount on the new integrated amp as an alternative, I declined that as finances are pretty tight and I couldn't justify another amp.

Not sure what to do with the old Bang but my son is now studying mechatronics engineering at university so I might let him have it and see if he can find a use for it either as a working amplifier or as a project/learning tool to use with the scope he's about to get for his birthday.

 

[mightygrey]

Burson doesn't provide any specs for the Bang when running in Mono configuration - would the power increase into 8 x ohms if a single Bang were used in each channel? The form factor for these little amps is so great that I could sneak two onto my desk comfortably to power a KEF LS50 each.

 

[Panelhead]

I do something similar with a pair of Micromega MyAmps. Use balanced dac to drive the channels out of phase.
Drives my 8 ohm speakers well. Should be a 120 watt amp in this case.
Has forced air cooling and low voltage rails. Should last.

 

[trl]

The output power should still remain 29W/channel on 8-Ohms speakers, but you might ping Burson for details. The limitation factor is heat dissipation, but also the inside voltage rails too.

The amp is great for powering a bedroom or for use inside a well-ventilated gaming rig, just not sure how to couple two of these in a "bridge mode". Although, there is no balanced inputs.

 

[Panelhead]

Bridging a single ended stereo amplifier into a balanced mono is easy. Requires a balanced source. The amplifier needs to use ground on the speaker output.
The BANG is a good candidate. Uses a LM3886 so only one output. Not +/-.
Connect the balanced source so that + goes to the center pin of one RCA and the - to the other. Run neutral to the shell of both RCA.
Connect the speaker cables to the + outputs on the BANG. Do not connect to the - speaker terminals.
It is now a balanced differential amplifier. Four times the power into 8 ohms. The BANG will struggle with 4 ohm loads if bridged.
Heat is an issue. The BANG looked to be light on heatsinks. Pictures indicated it uses the chassis for cooling.
Maybe be the August heat, but the cooling fans on my bridged mono’s seem to run more. If no music is playing they are audible. Never heard them during playback until this summer. They have LM3886 chips also.