Today I received 2 DeForest DL5 tubes.
I swapped out a Cunningham CX301-A Harrison Plant, long glass bulb in my amp for the DL5 (120H choke loaded , 120V anode ,ballery biased with -8V on the grid.)
Sounds wonderful! Better than the 01A in many respects. I will go back to the O1A and do more comparisons to see if I can decide on a favorite.
It is (~mildy) microphonic , a tad more than the 01A.
I highly recommend this tube😃
Here are some pics
Today I got to try the DL5 again.
If it wasn't so microphonic , I would used this tube over a Cunningham CX301-A because it does the upper mid/treble better than the 01A.
If it wasn't so microphonic , I would used this tube over a Cunningham CX301-A because it does the upper mid/treble better than the 01A.
Does this tube have anything to do with the original DL5 on isolantite base, produced from 1927 to 1928 or thereabouts, by the inventor of the triode, Lee DeForest? Or is it just a copy by some company using the same name?
Hi Gruesome, yep, it's the origional DL5 from the inventor of the triode Lee DeForest - I'd love to get some non microphonic. It's an amazing tube.
Has it got any mica in the top support ?
I gather the permeability of the glass is so low it's not much of an issue. More likely an issue would be out gassing of the internal elements and glass/metal seal. There are plenty of 01a's and other low power types still about perhaps because they made plenty but also maybe because they don't run that hot.
I read the suggestion that Mica can out-gas and may be the reason some people prefer globes to shouldered types, but I haven't seen any proof that it's the mica.
There are ways of helping to reduce the microphonics; what have you tried so far.
I gather the permeability of the glass is so low it's not much of an issue. More likely an issue would be out gassing of the internal elements and glass/metal seal. There are plenty of 01a's and other low power types still about perhaps because they made plenty but also maybe because they don't run that hot.
I read the suggestion that Mica can out-gas and may be the reason some people prefer globes to shouldered types, but I haven't seen any proof that it's the mica.
There are ways of helping to reduce the microphonics; what have you tried so far.
I don't know, that's why I'm asking. I also read that DeForest initially produced tubes with quite a bit of residual atmosphere -supposedly they were famous for their (gas, not glass envelope) glow- and did not understand the details of the amplification mechanism, and whether having bad vacuum (by later standards) was essential for it. Again, that's what I read. Supposedly bad vacuum limits the linearity and amplification factor of an amplifier tube.
Are these DL5 already 'real' vacuum tubes, or are they more like his original limited vacuum tubes? Do they glow when operating?
Before I saw your post, all I knew was that a Lee DeForest supposedly had invented 'vacuum tubes' (the vacuum triode), but I had no idea he had a production company.
So, I guess this is not like having one incredibly precious and rare prototype, too valuable to use, instead there's still plenty of these production tubes around? Similar to industrially produced pocket watches maybe. What do these go for, if I may ask?
Apparently the deForest company wasn't big into datasheets.... the first real audiophiles ;-)
See http://www.r-type.org/exhib/aaa0104.htm and http://www.r-type.org/articles/art-277.htm . (DL-5 = DV-5 with different base).
See http://www.r-type.org/exhib/aaa0104.htm and http://www.r-type.org/articles/art-277.htm . (DL-5 = DV-5 with different base).
Answering my own vacuum question: if the vacuum was bad, the getter deposition in the top half of the tube would have changed from silvery metallic to white. The presence of the getter also indicates that at this point deForest made real vacuum tubes.
Depends, they could have backfilled with Argon to get a non-oxidizing gas fill. Does this tube glow? What color?
It's a sad loss that some of these historical type tubes haven't been tested on a curve tracer to record what was achieved back then. Lots of uTracers around these days.
I have a Tektronix 576 Curve tracer here, it does have some low power max settings like 0.1 Watt, 0.5 Watt and 2.2 Watt. I'll have to confess that I'm usually using it on the 10 Watt or 50 Watt max settings for TV tubes. (there is a 220 Watt max setting too! ) Tough buggers these TV tubes. Can't kill them and they were a $1 each. Boxes of hundreds around.
I have a Tektronix 576 Curve tracer here, it does have some low power max settings like 0.1 Watt, 0.5 Watt and 2.2 Watt. I'll have to confess that I'm usually using it on the 10 Watt or 50 Watt max settings for TV tubes. (there is a 220 Watt max setting too! ) Tough buggers these TV tubes. Can't kill them and they were a $1 each. Boxes of hundreds around.
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Magnesium, if thats what they used is slower at changing colour. The milky grey is more apparent on the inside than the outside surface.
Wouldn't Argon stop it from being anything more than just a detector tube. DL5 should be a vacuum type.
Wouldn't Argon stop it from being anything more than just a detector tube. DL5 should be a vacuum type.
According to this website that Gruesome linked to, many of the early DeForest Audion tubes used a gas fill (low pressure) to get better amplifying performance. ( ion assisted conduction I guess )
http://www.r-type.org/articles/art-277.htm
http://www.r-type.org/articles/art-277.htm
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I've been busy 😁
To the person who asked about (on) filament color, my DL5 is the same bright yellow/orange color as my 801A, e.g. TT filament.
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I thought the opposite, i.e. the statement from deForest (the person or the company, not sure what I read) was they could not be used for power gain, only for demodulation (rectification). I'm not sure how ions (which would travel from the anode to the cathode, and dump their energy on that smaller electrode) would help in either case.