Bottlehead Forum
Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: fritzthecat on June 05, 2016, 12:55:10 AM
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At the moment I have some hum issues as i am using some very high efficient speakers - see pic.
Does anyone have general input how to approach and resolve these issues? With normal speakers my system is dead quiet. But with about 102 dB efficiency this looks different:-/
Where to start? Where to look at?
With the Kaijus I ordered the DC filament upgrade - looking forward to see the effect.
I guess I might have a general grounding problem but was able to reduce hum by about 95 percent by just using one power socket for the whole system but hum is still audible at the listening spot - so far no further improvements so I am looking for advice regarding these problems in general.
Any input would be very much appreciated.
How should I proceed with the filament improvement for the Kaijus? I am planning to first use them without and later upgrade.
Thank you so much!
All the best,
Chris
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That's what the DC filament supply is for.
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My guess is, that it will still be there then - but I'll check it out and will see. What else would you try if you had hum on your reference system?
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I am also experiencing hum from my Kaiju with 102db speakers. My plan was to break in the Kaiju then install the DC filament heaters after listening to the amp for a couple of hundred hours, however, the hum is very discernible from the listening position, consequently, I haven't been running the amplifier much.
In efforts tracking down and isolating the hum I built a couple of "test" rca's to see if the hum is from the Kaiju. With two "shorted" rca's on the Kaiju inputs the hum is just as noticeable as when the normal source is connected, it appears the hum is being generated within the Kaiju.
I'll build the DC Filament board this week and see if that helps.
I'll report on the hum after the optional kit is installed.
Unfortunately I sold my less efficient speakers when the Kaiju Kit was delivered.
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The DC filament supply will lower the hum level to an acceptable level for use with sensitive speakers.
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My guess is, that it will still be there then - but I'll check it out and will see. What else would you try if you had hum on your reference system?
Well, the DC filament supply will drop the hum level by about 15dB, so I would recommend installing the board before expending any energy on addressing the issue in another manner.
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I installed the DC Filament option tonight, as soon as I started it, it sounded great, no discernible hum even within a foot of the speakers (Lowther DX-4's in Lowther Acousta cabinets). After about ten minutes the right channel ceased operation and about ten minutes after that the left channel quit as well. It sounded great until channels started dropping.
Voltages measured 4.76 and 4.77. The Kaiju worked before I started the install, I've double checked my wiring and solder connections, everything is per the manual. Does anybody have any ideas on where to look for a fault? I'd appreciate the help.
It did sound really good before it quit. It just got too quiet.
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Were the voltages 4.76 when first checked, and still 4.76 after it stopped working? Is this with the stock 300Bs?
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Voltages remained the same. 300B's are JJ's
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4.76V is within 5% of 5V, so I shouldn't think that would be a problem. Do you see the filaments glow in the 300Bs?
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Turns out the issue here was simple. One of the heat sinks on regulator chips the DC supply board had fallen off and the other was very loose. That, compounded with the wood base feet not being applied to allow for adequate underchassis airflow led to the regulators overheating and shutting off. Snapping the heat sinks on the chips and running the amp with adequate airflow had the amp running fine with all the voltages spot on. mpdd will give it a good play tonight and we'll know for sure we have it sorted.
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I was stumped, I took the Kaiju to Bottlehead Headquarters. Dan had my mistakes quickly sorted with a smile.
Thank you for the great customer service and great Bottlehead products, the Foreplay and Kaiju are making beautiful music.
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Well, the DC filament supply will drop the hum level by about 15dB, so I would recommend installing the board before expending any energy on addressing the issue in another manner.
I'll do so - one thing I realised is, that the hum again is a bit lower now since I got a new current distrubution panel (house installation) installed this week in my house - but it is still there and it's not only a Kaiju problem I have it as well with other amps. As I had some issues with the voltages within the Kaiju build I think it's probably better to just have the filament upgrade installed after some hours of safe Kaiju operation - I'll try to sort everything out tonite.
Maybe in the end - to really be sure my current is clean I'll head for a Tesla Super Battery: https://forums.teslamotors.com/forum/forums/tesla-home-battery-ultimate-power-conditioner-home-soundsystems
Does anyone know someone having experiences with this one?
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Well, the DC filament supply will drop the hum level by about 15dB, so I would recommend installing the board before expending any energy on addressing the issue in another manner.
Hi Paul
I just finished my first Kaiju - great build experience - I am loving it already though it is just breaking in. I had some issues in terms of adjusting hum balance (posted some lines regarding this - the wirewound potentiometer does somehow not allow adjustments that are fine enough - the values are jumping in 3-4 mV steps).
With the lower efficiency test speakers everything was fine but when I attached the big horns in my main listening room to the Kaiju it was humming like crazy again - no wonder as the DC filament upgrade is not yet installed and I will do so this afternoon.
I am using the Kaiju to drive JBL 2445J large format midrange drivers being used without the back covers and tuned with Truextent beryllium diaphragms.
The drivers are attached to a 75 cm tractrix Horn from and have an efficiency of at least 111 dB 1W/m in this configuration. The frequency range is 320 Hz to 8500 Hz - from there JBL 2405 Slot tweeters take over (I am planning to replace them through Stage Accompany SA8535 Ribbon Drivers with the origninal hornsas soon as I can get hold of any at a decent price).
What do you think, is the filament upgrade going to solve the problem? I guess not, as the hum really is very loud. And is there any possibility for finer adjustments regarding hum balancing? I just wonder if I could ad another multiturn potentiometer or replace the original one - if possible, what exact type of potentiometer would I have to order?
It would be great if you could give me some advice regarding this. In the meantime I'll install the DC Filament upgrade and hope after that the hum is at least as low that one can enjoy listening. At the moment it really sonds awfull.
Thank you and have a nice Sunday,
Chris
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Well, the DC filament supply will drop the hum level by about 15dB, so I would recommend installing the board before expending any energy on addressing the issue in another manner.
Done! DC Filament upgrade installed - got late - will test tomorrow - here some pics... Thanx a lot - I guess this will help massively...
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Nice clean build, Chris. Let us know how you like the DC conversion after you've had some time to evaluate the differences.
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When you get past 110dB efficiency, you can install the DC filament supply board and rewire the output transformers for a lower secondary impedance.
The hum reduction from rewiring the output transformers is not as drastic as adding the DC filament supply, but you will also get a reduction in tube self-noise in the process at the expense of making less power (which you don't need with speakers that efficient).
-PB
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When you get past 110dB efficiency, you can install the DC filament supply board and rewire the output transformers for a lower secondary impedance.
The hum reduction from rewiring the output transformers is not as drastic as adding the DC filament supply, but you will also get a reduction in tube self-noise in the process at the expense of making less power (which you don't need with speakers that efficient).
-PB
I installed the DC filament supply board yesterday but it got late so I decided to check it today. I wired the output transformers for 16 Ohms as this is the impedance of my midrange drivers the Kaiju is thought to drive. So this means I might rewire them for 8 Ohms or 4 Ohms? Or even 2 Ohms? What should I try? Power is not an issue anyway - with these speakers I can easily blow myself out of the room...;o)
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Go for 2 Ohms. Your speakers need just a tiny drip of power to blow your eardrums out, so shedding gain/power is quite desirable.
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thank you - so I went exactly in the wrong direction. I guess for the JBL slot tweeters it is the same. I am planning to implement some Stage Accompany Ribbon Tweeters - as they are among the best I have ever heard.
Using several binding posts would it be possible to get several options regarding OT wiring? Or is that a stupid idea? Maybe because of additional metal and wiring attached to the OTs?
BTW: almost no more hum after installing Filament upgrade! I'm amazed!
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Using several binding posts would it be possible to get several options regarding OT wiring? Or is that a stupid idea? Maybe because of additional metal and wiring attached to the OTs?
There are a couple of ways to wind the secondary of an output transformer. The low cost option is to wind a single winding and just tap it at 4, 8, and 16 Ohms. This allows for three impedance taps on three separate binding posts, but you leave a lot of unused copper on the secondary when you use the 4 and 8 Ohm taps, which impairs coupling between the primary and secondary .
Our transformers require a little more effort to rewire for different taps, as the secondaries are wired in lower impedance sections to improve coupling between primary and secondary at all impedances, and therefore impedance switching is more complicated than just adding binding posts.
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I didn't know that as the few tube kits I built so far all are the other less sophisticated types. Thank you very much!