Hi Giaime...from this post I understand that you don't own Morgan Jones 3rd edition of valve amplifiers!? The crystal palace driver stage does exactly what you want (would also make a good driver for a PP EL36).
Erik
Hi Giaime,
I feel the book has to be read more than once to get the most value. Not everything, but there is a lot in there.
-Chris
Yes! I second that.
I feel the book has to be read more than once to get the most value. Not everything, but there is a lot in there.
-Chris
No, it isn't RDH4, but it is the most practical book in my collection. Anyone who has soldered a tube socket should own one. My humble opinion, that is. Maybe someone could organize a group buy for those without a copy.anatech said:
------> Giaime: I saw a copy @ RS ... I can't remember the price but I guess it should be as expensive as a quartet of EL36 can be (LOL)
Ciao
Ciao
Yeah, considered that I almost had a fight with the shop guy... maybe I told this story to you? 
Does anybody know if a 4th Edition is looming on the horizon?
If you look at it, Morgan's quite consistent on his release gaps- 1995, 1999, 2003.
Based on this, a new one *might* arrive in 2007.
How about The Tube Amp Book (Spiral-bound)
by Aspen Pittman? Is this on the same caliber as Morgan's?
If you look at it, Morgan's quite consistent on his release gaps- 1995, 1999, 2003.
Based on this, a new one *might* arrive in 2007.
How about The Tube Amp Book (Spiral-bound)
by Aspen Pittman? Is this on the same caliber as Morgan's?
Tony said:
OK, he owes me a beer. 😉
From what I understand, the 4th is in the works, but won't be appearing anytime soon. Honestly, I don't think there's any other contemporary book to compare, and I came to the book with a deep sense of skepticism. "Valve Amplifiers" is not as broad and deep as RDH4, but it's got a lot of new stuff RDH4 didn't have AND it's written in a very accessible style. Jones has a real talent for teaching.
I have only read some brief snippets on the web. Morgan Jones has been publishing since 1951. You would do well to buy the 3rd edition at a reasonable price... while you still can... there may be no 4th edition.
🙁
🙁
SY said:
in my youth, about 7 or 8 years ago, i developed an LED enlarging head to replace the Beseler/Minolta 45a which used pulsed xenon flash-tubes -- this when high output blues were just getting rolling. each LED string likes its own current limiter -- whether it's a simple resistor or a programmed current source. this was confirmed by an Agilent guy -- (probably an Avago engineer now) and probably in their application notes somewhere. I get about 1 inquiry a month looking for a purchase -- such is the state of wet chemistry photography that it isn't worth the effort. for my application i programmed the surface mount LM317's so that the intensity could be pulse-width modulated as well as "wrenched" by the current limiter. Jim Williams has much more rigorous ideas in his paper on current sources for diode lasers.
LED's can also go a little wonky when they are in close proximity to each other and heat themselves up -- just like any other semiconductor device. they also have a little junction capacitance but even with an array like this shouldn't be a problem (unless you are pulsing them which certainly isn't the case in this application).
Well, I am at the beginning stage of working with high output UV LED's -- they do some really nifty stuff with photo-initiators and cross linking polymers. but I keep ripping up and remaking a Pilot EL84 amp so this might be the next iteration.
Oh, you might want to bypass the 20uF cap in the Maida regulator with a Wima film unit and put a 1n4007 to provide a discharge return path across the LM317, and specify the 56k resistor as 2W.
Yes, the 56k should indeed be 2W or more (I used a 3W)- I'll add that to the schematic.
Protection diodes and the like are harmless, but really not needed in this reg circuit. I've used this a few dozen times in various amps without a single failure. Likewise, Joe Curcio (the guy I stole it from) has a few hundred of these out in the field without any issues. The bypass cap doesn't really do much, unless you bring it directly from output to ground, in which case its discharge will certainly kill the reg without a protection diode.
The combination of the electrolytic and the series resistor keeps the dynamic impedance pretty low well past the point where you need it; at the same time, the series R really smooths out the regulator response to transient current demands. When I was experimenting with this reg some years back, I connected a load across it which would change current draw periodically (a square wave driving a power bipolar with the collector load sized for the max current). The RC combo gave the least remarkable regulator response. It's a Good Trick which I was very happy to appropriate.
Protection diodes and the like are harmless, but really not needed in this reg circuit. I've used this a few dozen times in various amps without a single failure. Likewise, Joe Curcio (the guy I stole it from) has a few hundred of these out in the field without any issues. The bypass cap doesn't really do much, unless you bring it directly from output to ground, in which case its discharge will certainly kill the reg without a protection diode.
The combination of the electrolytic and the series resistor keeps the dynamic impedance pretty low well past the point where you need it; at the same time, the series R really smooths out the regulator response to transient current demands. When I was experimenting with this reg some years back, I connected a load across it which would change current draw periodically (a square wave driving a power bipolar with the collector load sized for the max current). The RC combo gave the least remarkable regulator response. It's a Good Trick which I was very happy to appropriate.
Great article Stuart...really an interesting reading.
For the SE lovers...what do you think about an El84 PSE, pentode connected, red string bias and shunt feedback? I've got an OT that can work with something like this...ok sorry for the OT
Another question...which the el84 plate voltage with your OT?
You said me the same thing last year...and I've got it. One of the best advice that I've ever listened to 😀
And Giaime...you can buy it in Padova...libreria progetto 😉
Mark
For the SE lovers...what do you think about an El84 PSE, pentode connected, red string bias and shunt feedback? I've got an OT that can work with something like this...ok sorry for the OT
Another question...which the el84 plate voltage with your OT?
SY said:
You said me the same thing last year...and I've got it. One of the best advice that I've ever listened to 😀
And Giaime...you can buy it in Padova...libreria progetto 😉
Mark
With the Dyncao power transformer, I get about 340V at idle, dropping to about 320V under full drive.
No reason at all not to use LEDs to bias an SE amp. It should work fine, other than the fact that it's an SE amp.
No reason at all not to use LEDs to bias an SE amp. It should work fine, other than the fact that it's an SE amp.
SY,
I just woke up to this thread, not having time to read them all. Nice article in Bas’ webzine! Hey, that boy can write, but we knew that!
I have a humble little Dyna SCA-35 amp that I got for next to nothing, still sitting on the shelf only partially refurbished. I thought it might be a decent basis for a secondary lab/workshop system. I was already converting it to all triode front-end, ripping out the tone controls - the usual stuff - but I think I will use some of your tips, especially the LED array, which ought to look appealingly odd beaming up through the perforated top cover. I will probably keep it in ultra-linear mode though. Given the humbleness of this little Dyna, I’ll need to learn the Kanji symbols for “unworthy little piece of junk”.
Can you tell us more about those “lost nights long ago in Amsterdam” that inspired the “red light district” name? We promise we won’t tell your wife!
I just woke up to this thread, not having time to read them all. Nice article in Bas’ webzine! Hey, that boy can write, but we knew that!
I have a humble little Dyna SCA-35 amp that I got for next to nothing, still sitting on the shelf only partially refurbished. I thought it might be a decent basis for a secondary lab/workshop system. I was already converting it to all triode front-end, ripping out the tone controls - the usual stuff - but I think I will use some of your tips, especially the LED array, which ought to look appealingly odd beaming up through the perforated top cover. I will probably keep it in ultra-linear mode though. Given the humbleness of this little Dyna, I’ll need to learn the Kanji symbols for “unworthy little piece of junk”.
Can you tell us more about those “lost nights long ago in Amsterdam” that inspired the “red light district” name? We promise we won’t tell your wife!