bitrex wrote: ------------------> > Tangentially related - the audio sine wave oscillator I've been using > for several years is a solid state box labeled "LofTech"; manufactured > by "Phoenix Audio Labs, Manchester, CT". > > It's mostly full of LM13600s and TL074s with date codes from the middle > of 1986. I don't have a THD analyzer so I can't say what its specs are > now in that regard; visually at least the sines it puts out look math > textbook perfect on a scope. The brochure claims a maximum THD of 0.5% > > Unfortunately frequency stability isn't good - it's very drifty with > time and temperature; sometimes 3-5 Hz up and down over time just > sitting in a shop at room temperature, which is annoying. The brochure > scan online doesn't say anything about drift specs so I don't know if > that's normal for the product's design or if it should be serviced. >** See link: http://www.barryrudolph.com/recall/manuals/loftts1.pdf The unit has a single pot that sweeps the audio band, assuming it is a carbon track type, frequency stability WILL be poor. Firstly, the track has a large tempco plus the wiper will have some drift after setting. So it is not faulty. My bench oscillator use a dual gang WW pot with hundreds of turns plus it only covers a decade range. A rotary switch choses which one of five starting at 2Hz. Drift is very small. The all valve one I mentioned also has low drift, once it fully warms up, as the frequency determining bits are an air capacitor and MF resistors. .... Phil
The HP Original for sale
Started by ●July 2, 2017
Reply by ●July 3, 20172017-07-03
Reply by ●July 3, 20172017-07-03
bitrex wrote: -----------------> > Tangentially related - the audio sine wave oscillator I've been using > for several years is a solid state box labeled "LofTech"; manufactured > by "Phoenix Audio Labs, Manchester, CT". > > It's mostly full of LM13600s and TL074s with date codes from the middle > of 1986. I don't have a THD analyzer so I can't say what its specs are > now in that regard; visually at least the sines it puts out look math > textbook perfect on a scope. The brochure claims a maximum THD of 0.5% > > Unfortunately frequency stability isn't good - it's very drifty with > time and temperature; sometimes 3-5 Hz up and down over time just > sitting in a shop at room temperature, which is annoying. The brochure > scan online doesn't say anything about drift specs so I don't know if > that's normal for the product's design or if it should be serviced. > > I managed to find a schematic: > > <http://www.ka-electronics.com/images/jpg/Loftec_TS1.jpg> >** The schem shows a form of VCO with a linear to log converter - reminds me a lot of a Moog Synth. It will drift with temp etc .... ..... Phil
Reply by ●July 4, 20172017-07-04
On 07/03/2017 01:40 PM, Cursitor Doom wrote:> On Sun, 02 Jul 2017 15:15:25 -0700, pcdhobbs wrote: > >> The 200C isn't the original 1939 model. It was the last tube instrument >> HP sold (CRTs and PMTs apart) and was in their 1985 catalogue. (Yes, I >> have one.) ;) > > And I've probably got one, too. :P >Still waiting to see your list! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●July 4, 20172017-07-04
On 07/03/2017 09:54 PM, Phil Allison wrote:> bitrex wrote: > > ------------------ > >> >> Tangentially related - the audio sine wave oscillator I've been using >> for several years is a solid state box labeled "LofTech"; manufactured >> by "Phoenix Audio Labs, Manchester, CT". >> >> It's mostly full of LM13600s and TL074s with date codes from the middle >> of 1986. I don't have a THD analyzer so I can't say what its specs are >> now in that regard; visually at least the sines it puts out look math >> textbook perfect on a scope. The brochure claims a maximum THD of 0.5% >> >> Unfortunately frequency stability isn't good - it's very drifty with >> time and temperature; sometimes 3-5 Hz up and down over time just >> sitting in a shop at room temperature, which is annoying. The brochure >> scan online doesn't say anything about drift specs so I don't know if >> that's normal for the product's design or if it should be serviced. >> > > ** See link: > > http://www.barryrudolph.com/recall/manuals/loftts1.pdf > > The unit has a single pot that sweeps the audio band, assuming it is a carbon track type, frequency stability WILL be poor. > > Firstly, the track has a large tempco plus the wiper will have some drift after setting. So it is not faulty. > > My bench oscillator use a dual gang WW pot with hundreds of turns plus it only covers a decade range. A rotary switch choses which one of five starting at 2Hz. Drift is very small. > > The all valve one I mentioned also has low drift, once it fully warms up, as the frequency determining bits are an air capacitor and MF resistors. > > > > .... Phil >Got it, thanks. Probably time to invest in something a little better.
Reply by ●July 4, 20172017-07-04
On 07/03/2017 10:52 PM, Phil Allison wrote:> bitrex wrote: > > ----------------- > >> >> Tangentially related - the audio sine wave oscillator I've been using >> for several years is a solid state box labeled "LofTech"; manufactured >> by "Phoenix Audio Labs, Manchester, CT". >> >> It's mostly full of LM13600s and TL074s with date codes from the middle >> of 1986. I don't have a THD analyzer so I can't say what its specs are >> now in that regard; visually at least the sines it puts out look math >> textbook perfect on a scope. The brochure claims a maximum THD of 0.5% >> >> Unfortunately frequency stability isn't good - it's very drifty with >> time and temperature; sometimes 3-5 Hz up and down over time just >> sitting in a shop at room temperature, which is annoying. The brochure >> scan online doesn't say anything about drift specs so I don't know if >> that's normal for the product's design or if it should be serviced. >> >> I managed to find a schematic: >> >> <http://www.ka-electronics.com/images/jpg/Loftec_TS1.jpg> >> > > ** The schem shows a form of VCO with a linear to log converter - reminds me a lot of a Moog Synth. > > It will drift with temp etc .... > > > ..... Phil >Engineers probably worked for years to design clever "DCOs" which frequency-locked analog oscillators to a temperature stable reference clock, divided down under microprocessor control. Now musicians want the drift back. The drift sounds "organic."
Reply by ●July 4, 20172017-07-04
>Engineers probably worked for years to design clever "DCOs" which >frequency-locked analog oscillators to a temperature stable reference >clock, divided down under microprocessor control.Way before microprocessors, there were "top octave generators", strings of dividers running off a strategically-chosen crystal. They were too accurate, so they sounded thin. Cheers Phil Hobbs
Reply by ●July 4, 20172017-07-04
On Mon, 3 Jul 2017 17:40:13 -0000 (UTC), Cursitor Doom <curd@notformail.com> wrote:>On Sun, 02 Jul 2017 15:15:25 -0700, pcdhobbs wrote: > >> The 200C isn't the original 1939 model. It was the last tube instrument >> HP sold (CRTs and PMTs apart) and was in their 1985 catalogue. (Yes, I >> have one.) ;)The 200CD was the last all tube instrument that HP made. <http://hpmemoryproject.org/wa_pages/wall_a_page_01.htm> "The HP200CD was a serious competitor in the HP longest product life contest. It remained in the Hewlett-Packard Test and Measurement catalog until 1985, a full 33 years which is rare in the electronics industry. Last, but not least, the 200CD was the last fully vacuum tube instrument produced by HP." There were some later instruments that still contained a few tubes. I don't recall the numbers.>And I've probably got one, too. :POnly one? I've got eight HP catalogs: <http://www.LearnByDestroying.com/jeffl/crud/HP-Catalogs.jpg> Most catalogs have been scanned and are available online at: <http://www.hparchive.com/hp_catalogs.htm> (2.2MB) <http://www.hparchive.com/Catalogs/HP-Catalog-1943-First-Plus.pdf> (32MB) The first catalog (1943) has some info on the 200C and 200D oscillators: <http://www.hparchive.com/Catalogs/HP-Catalog-1943-First.pdf> -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●July 4, 20172017-07-04
<http://www.LearnByDestroying.com/jeffl/crud/HP-Catalogs.jpg> I'm pretty sure CD and I were both talking about having an HP200C, not just the catalogue. Mine is actually the slightly newer 200CD, which was the last tube model they made. Cheers Phil Hobbs
Reply by ●July 4, 20172017-07-04
On Mon, 3 Jul 2017 10:35:54 +0300, the renowned Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:>On 3.7.17 04:46, bitrex wrote: >> On 07/02/2017 06:15 PM, pcdhobbs@gmail.com wrote: >>> The 200C isn't the original 1939 model. It was the last tube >>> instrument HP sold (CRTs and PMTs apart) and was in their 1985 >>> catalogue. (Yes, I have one.) ;) >>> >>> Cheers >>> >>> Phil Hobbs >>> >> >> Wow, that late? I'm trying to think of other 1930s era industrial >> designs that had such a long life cycle. GG1 locomotives? Iowa class >> battleships? GM straight six? > >DC3 / C47 from Douglas Aircraft.They're currently being refitted with modern turboprops.. Basler. https://en.wikipedia.org/wiki/Basler_BT-67 https://upload.wikimedia.org/wikipedia/commons/2/24/Basler_south_pole.jpg Beautiful aircraft! --sp -- Best regards, Spehro Pefhany
Reply by ●July 4, 20172017-07-04
On Tue, 04 Jul 2017 14:58:42 -0700, pcdhobbs wrote:> <http://www.LearnByDestroying.com/jeffl/crud/HP-Catalogs.jpg> > > I'm pretty sure CD and I were both talking about having an HP200C, not > just the catalogue. Mine is actually the slightly newer 200CD, which was > the last tube model they made.I think I'm right in saying the only HP sig gen I have is an old analogue one (probably Wien Bridge internals) that only covers 10hz to 512Mhz IIRC. It's a joy to use because it's so simple, unlike some of the others which require considerable re-familiarisation with every time I break one of them out in anger. This wonderful simplicity is why it gets used more than any other sig gen I own unless its limited range makes it unsuitable for the task. Sorry, Phil, but that list will probably never get written; I just don't have enough time to itemise everything.
