Bottlehead Forum
Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: ebag4 on April 04, 2016, 06:53:00 AM
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With the various threads noting tubes that aren't built to the 300B spec, does anyone have a list of tubes that are? A list of tubes that are suitable for the Kaiju with and without the DC filament supply would be very helpful to those looking to try other tubes but are new to the 300B.
Thanks,
Ed
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JJ's although current spec is 1.3
Katatsuki
All of the Sophia tubes I think. Or at least the so called mesh and standard 300
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The KR 300B balloon claims to be a WE standard replacement, however the spec says the filament draws 1.9 amps. I read where PJ stated the 300b spec is 1.2 amps, I also read where PJ stated he wouldn't run a tube that drew more than 1.4 amps in the Paramount. Am I missing the point or does the KR draw too much to be a drop in WE replacement and therefore too much to use in the Kaiju?
Thanks,
Ed
Edit: I have now seen another webpage that shows the filament current at 1.2, which would seem to make more sense.
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Adjustments can be made for small changes in the filament current. The risk is that the regulator chip may overheat if too much current is drawn, especially if the power line voltage is also high. We have not determined how far you can deviate from the standard 1.2 amps without risking failure of the chip, so the risk is yours.
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What are the critical parameters other than filament current and voltage? What would you recommend regarding the tube listed below for AC and DC filament use?
Royal Princessâ„¢ 300B
Nominal operating conditions and parameters:
Filament voltage
5,0 V *
Nominal filament current
1,2 A
Plate voltage
300 V
Grid voltage (AC filament)
61 V **
Grid voltage (DC filament)
58 V ***
Plate current (AC filament)
60 mA
Plate current (DC filament)
62,5 mA
Grid to plate transconductance
5700 Ω
Amplification factor
3.85
Grid current
0.05 µA
Plate resistance
700 Ω
Limiting Operation conditions for safe operation-nor simultaneous ratings:
Maximum plate voltage
450 V
Maximum plate dissipation
40 W
Maximum plate current of average tube for fixed grid bias
70 mA
Maximum plate current for manually adjusted grid or self-biasing circuit
100 mA
* - AC filament supply or DC filament supply.
** - AC filament supply is used. The grid and plate returns should be connected to a center tap on the secondary of the filament transformer.
*** - DC filament supply is used. The grid and platter returns are connected to the negative end of the filament.
Thanks,
Ed
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Only the filament voltage and current are critical - almost all "300B" tubes will have acceptable values for the other parameters.
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Thanks Paul, does the Kaiju comply with the parameters listed below for the base build and when the DC filament board is added?:
** - AC filament supply is used. The grid and plate returns should be connected to a center tap on the secondary of the filament transformer.
*** - DC filament supply is used. The grid and platter returns are connected to the negative end of the filament.
Thanks,
Ed
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No. We use a "hum pot" which produces an adjustable center tap. In the case of AC heating, this allows correction of imperfectly filament geometry. For DC heating, the defects (if any) of the regulator chip are cancelled.
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hey Ed - FYI, I spent way too much time researching tubes. I understand that you are now in that process. FWIW, there seemed to be a lot of feedback about Sophia's being unreliable and not outlasting the warranty so that is why I avoided them. but who knows, some really like them.
Check out the Elrog's, they seem to get great reviews but take a while to get. EML has a basic 300b that is in spec to Western Electric 300b. However, it is not hard to set your Kaiju up for whatever tube you choose (within reason I guess). Measure your current voltages relative to your house voltage and see where you stand now. Filament voltage seems pretty standard at 5 volts. I had to add resistors in parallel to get mine to within 4% (recommended by EML). Most tube manufacturers seem to recommend 5% but EML wants 4%. The plate dissipation in my Kaiju ended up being just under 26 watts which is fine.
Paul is super helpful and I am sure can help you get whatever tube you choose working well. Check out a thread called "300b tube offering depressing" on SET Asylum. Started by Gordon Rankin, very interesting comments.
Good luck with your search, I look forward to hearing your experiences.
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hey Ed - FYI, I spent way too much time researching tubes. I understand that you are now in that process. FWIW, there seemed to be a lot of feedback about Sophia's being unreliable and not outlasting the warranty so that is why I avoided them. but who knows, some really like them.
Check out the Elrog's, they seem to get great reviews but take a while to get. EML has a basic 300b that is in spec to Western Electric 300b. However, it is not hard to set your Kaiju up for whatever tube you choose (within reason I guess). Measure your current voltages relative to your house voltage and see where you stand now. Filament voltage seems pretty standard at 5 volts. I had to add resistors in parallel to get mine to within 4% (recommended by EML). Most tube manufacturers seem to recommend 5% but EML wants 4%. The plate dissipation in my Kaiju ended up being just under 26 watts which is fine.
Paul is super helpful and I am sure can help you get whatever tube you choose working well. Check out a thread called "300b tube offering depressing" on SET Asylum. Started by Gordon Rankin, very interesting comments.
Good luck with your search, I look forward to hearing your experiences.
Thanks Drew, yes, I am hunting for 300B's now. A lot of varying opinions on the same tubes, it is difficult to really make any decision based on those opinions. Of course with tubes I don't think we have much of a choice, pick one and hope for the best. I was very interested in the Elrogs, however their reliability has been poor per the reports I have read, unfortunately that opinion has almost been unanimous, they are too expensive to take that risk, at least for me at this time.
I am still considering the EMLs as well, just trying to determine what I can drop into my Kaiju and what may need adjustments prior to trying.
How are you liking the EML's?
Best,
Ed
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Hi Ed - The EML's are really quite a step up from the Sovtek's. They seem to be very well manufactured. So far so good. Of course, I have not had them long so I can't say much about their longevity although they seem to get very good reviews (with the exception of one or two very old complaints) It is clear that people were trying to fit them into amps that were not appropriately biased and probably burning out the tubes.
It is not difficult to get them to spec in the Kaiju at all. The standard 300b is probably plug and play although you might need to fine tune the filament voltage because it draws a bit more current (1.3) This easily done by soldering 4 resistors in parallel over the existing 51 ohm, I already have the values in my thread. the plate dissipation will most certainly be fine, well under the maximum of 40 watts. The XLS is a powerhouse and probably not the right choice in the Kaiju. The Mesh will work with some fine adjustments to the filament voltage. The mesh is supposed to have a different sound characteristic from the standard, more delicate, maybe more like a 2a3 which is what I was looking for. Some prefer the standard.
If you decide on the EML, I am sure you can get plenty of help setting them up, I'll be happy to share any of my experience with you. I can't speak for Paul but I bet he will be very helpful although most of the info is already up on my thread. Why don't you post all of your measurements so we can see where you are with stock tubes.
Having said all this, I am really not trying to sway you in a certain direction, everyone's system and tastes are different. So far, I am really happy with the EML (with the exception of the dealer).
OH, make sure to set your hum balance before you install the DC regulator and mark the settings. You won't be able to tell much after you install the DC regulator.
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I picked up a lightly used pair of Sophia Royal Princess 300B. I'll give them a spin. Buying used should afford me the ability to try more tubes until I land on a pair I want to stay with. These should be plug and play, I will wait on the DC filament until I hear these on AC. Hopefully have them early next week.
Best,
Ed
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good plan! let me know how they work out.
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good plan! let me know how they work out.
Haha...I hope so ;D.
Thanks,
Ed
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I have picked up a pair of Elrog 300Bs (realizing of course they are not a true 300B) after reading where a couple of members have had decent luck with the tube. Is the Kaiju and Paramount circuit similar enough that mods for the Paramount would apply to the Kaiju? I am still looking for what those mods might have been. Any insight is appreciated.
Best,
Ed
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The Paramount and Kaiju circuits are basically the same - the big difference is in Kaiju's larger plate choke and output transformer, which sets the parafeed capacitance. That capacitor, and the 0.1uF 630v interstage capacitor are (in my opinion, of course!) the best place to experiment with boutique components. I have Auricaps for parafeed in my personal Paramounts.