kevin gilmore Posted January 11, 2016 Author Report Posted January 11, 2016 go ahead and try other compatible tubes. whats the worst that can happen, fried tubes or blown parts. i have tried kt88, 6550 and 6l6, all end up the same way with G3 toasted. 1
xianghao Posted January 11, 2016 Report Posted January 11, 2016 i have ordered 4 X 20B-V4 for GG. Does anyone want to buy it ? Maybe a Group buy can get nice price.
nopants Posted January 11, 2016 Report Posted January 11, 2016 I'd be interested if the price cut's good, though I imagine it'll still be prohibitively expensive. Have you contacted them about it already?
xianghao Posted January 12, 2016 Report Posted January 12, 2016 10 hours ago, nopants said: I'd be interested if the price cut's good, though I imagine it'll still be prohibitively expensive. Have you contacted them about it already? Yes.if we order at least 10pics,it can be a low price.
JimL Posted January 12, 2016 Report Posted January 12, 2016 So to expand on Dr. GIlmore's point. With few exceptions, tube amplifiers use output transformers. An audio output transformer with a very high turns ratio is more difficult to design and build, so for output tubes you want a relatively moderate voltage (say 300-550 volts) with relatively high current (say 80-150 mA). That way a moderate turns ratio will supply a reasonable output voltage with adequate current. For a stat headphone amp, on the other hand, you want a high voltage to supply enough voltage swing, but you don't need nearly as much current (10-20 mA is enough). As spritzer has noted, you seldom if ever approach the full voltage swing that a stat amp is capable of - enough to fry the diaphragms in all likelihood. But having that large voltage swing means that at tolerable dB levels, the outputs are staying well away from the voltage limits where device linearity goes to pot.
JoaMat Posted January 12, 2016 Report Posted January 12, 2016 Rebuilt a Blue Hawaii to Grounded Grid - seems very promising.
JoaMat Posted February 14, 2016 Report Posted February 14, 2016 Continued the rebuilt. Emission Labs DHT Tubes, EML 20B-V4. To the left is variac. Its purpose is to set the two small transformers to appropriate voltage for the filament. 6
sorenb Posted February 14, 2016 Report Posted February 14, 2016 1 hour ago, JoaMat said: Continued the rebuilt. Emission Labs DHT Tubes, EML 20B-V4. To the left is variac. Its purpose is to set the two small transformers to appropriate voltage for the filament. not much O'Hara ...
JoaMat Posted February 14, 2016 Report Posted February 14, 2016 You are right. Even when completely dark the tubes can be barely seen. Very disappointing, but the sound is OOOK!!! Maybe I should turn up the variac, it’s only at 67% percent...
Kerry Posted February 15, 2016 Report Posted February 15, 2016 Sweet Very curious about your thoughts on how it sounds.
joehpj Posted February 15, 2016 Report Posted February 15, 2016 Please compare GG to other mafia designs. Like the tubes a lot.
JoaMat Posted February 16, 2016 Report Posted February 16, 2016 On 2016-02-15 at 1:21 AM, nopants said: any ac hum problems? I can’t hear any AC hum – doesn’t mean that there isn’t any though. The filament transformer gives [email protected] out. In order to reduce voltage for tube heating (5.0V +/-5%) I’ve put wire wound resistors in series with heater. Below shows the small board with terminals and resistors mounted to Kevin’s main board on two stand offs. For info I followed this link and bought some SiTubes filament supplies. They work OK for a quarter of an hour or so than the voltage drops to a few tenths of a volt. After some cooling down they are fit for fight again. I should have red data sheet. Maybe this would do if you really want DC heating. Probably overkill??
joehpj Posted February 16, 2016 Report Posted February 16, 2016 (edited) I wonder if we can use thermistor for the job, Lower the inrush current and thus prolong the heater's life. And also add time delay for HV. but but but I don't know how to calculate. Edited February 16, 2016 by joehpj
JoaMat Posted February 16, 2016 Report Posted February 16, 2016 I’m actually reading the information Emission Labs sent me with the tubes. Regarding filament they say: “The filament voltage must be exactly as specified, under all circumstances. Slow-start filament electronics taking longer than 10 seconds, are not allowed, otherwise this may damage the tubes” “Stand-by mode should not be used with directly heated tubes.
JoaMat Posted February 17, 2016 Report Posted February 17, 2016 Here is a Blue Hawaii I built a couple of years ago. Just removed the EL34 (left channel) and put the EML 20B-V4 tall base in place. Held my breath, closed my eyes, pulled the trigger and…. it works
JoaMat Posted February 17, 2016 Report Posted February 17, 2016 Life is short. Would T2 accept EML 20B-V4 tall base? Yes, she does! For how long? 1
nopants Posted February 18, 2016 Report Posted February 18, 2016 that was what I was planning to ask, seems like the dht is a straight sub for the el34 for most of the designs
kevin gilmore Posted February 18, 2016 Author Report Posted February 18, 2016 don't let any of the idiots over there know about this, the first thing that will happen is that someone will plug the tubes into a bhse directly and destroy $2k in tubes and probably trash the rest of the thing. these dht's have virtually identical curves to 6ca7 in triode mode. 2
nopants Posted February 18, 2016 Report Posted February 18, 2016 yeah the price of the tubes is kind of a problem, I wonder how they compare though. hybrid dht sounds too interesting to not try.
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now