HP Oscillators
 

https://www.hpmemoryproject.org/wb_p...b_page_10a.htm

Just looking at a few at the moment and found this quite useful.

Re: HP Oscillators
 

The original 200 was based on octal valves and a light bulb.
The 200C and 200D were an update to miniature valves and a smaller cabinet. These were kept in production for a long time because nothing else matched their voltage output.

651s are good units... up to 10MHz as well but not the lowest distortion. FETs, but still a variable capacitor Wien bridge. Nice construction.

239 is the highest performance, distortion-wise. Was also combined witha distortion meter as 339A. In a way, that was the precursor to the 8903. G-J and myself both use 8903s

All of these things havefuller explanations in the HPJ

David

Re: HP Oscillators
 

Magic stuff thanks for the heads up with the 8903 as i am currently mulling on the buying of one and that's great to hear there held to such high order, greatly appreciated.:thumbsup:

Re: HP Oscillators
 

The 8903 was in production for a long time, sort of overlooked for a model update. Audio Precision grabbed the audio test market.... their systems were essentially just PCs with extra-good soundcards and some software. Only relatively recently has HP entered that field with anew box, designed in Penang with some help from an ex-colleague of mine.

THe 8903 has a B model with some improvements. Watch out for the optional weighting filters if you need specific ones.

Any distortion meter tells you how bad your problem is, but you need spectrum analysis to get clues as to where to go hunting.

I built a stupidly OTT amplifier for my lounge. I had to build custom test gear to measure it! Completely pointless, but nice to do something daft to prove a point.

David

Re: HP Oscillators
 

Many thanks for the advice David-yes its a real tricky one as I have AC Volt meters Qty 2 made by Kenwood and use a National Distortion meter and some Farnell's for oscillators and frequency counters and scope as and when. But would be great to get more focused on a one way package but not wanting to go the pc route at all even with fancy sound cards etc-really not my thing! The hang up would be the cost to introduce a Spectrum analyser as budget cant get to that at this stage but thought the 8903B etc might be a good start to use and learn from. Its not for lab works or R&D but is useful to be able to have some idea whats going on before and after repair and note the results.

Re: HP Oscillators
 

THe 8903 automates the tuning of the notch, so you get a distortion figure not influenced by the operator skill in notching out the fundamental. They are very easy to use.

Also, they can express the result as signal to noise ratio and SINAD in dB, and measure output RMS voltage. Quite a useful combination.

With a distortion meter notching the fundamental, you can put a very basic low cost spectrum analyser (even a consumer soundcard) on the residual signal output from the distortion meter.... this lets you get away with a cheap analyser or PC software, and get all the clues extracted. Rather than an FFT analyser, I have an old 3580A a very trad bit of HP gear BUT it has an extremely sensitive input and can see signals below a microvolt. Classic and classic...AND it has a tracking generator built in for plotting frequency responses... and it does logarithmic sweep for good measure.

The FFT analyser is faster, and goes to 100kHz, but the old 3580 can do some things it can't.

David

Re: HP Oscillators
 

Again sincerest thanks for the heads up on my endeavour's toward the thoughts on a purchase of a HP but can I ask is the A or the B the one to consider as I have been offered a B model at a very budget friendly price but shall take a look at a 3580 in due course. That's great advice with the Spectrum analyser would be great to have one and learn from but I think i could learn a great deal already from using the A or B and then take it a stage further in latter days:)Also being easy to use is a welcome note as the manual seems quite daunting initially even after all these years its like 'How much work':-D
Anyway advices greatly a[appreciated and very much on the way to putting pay to the purchase hopefully toward the end of this month all being well.:)

Re: HP Oscillators
 

8903B has a bit more versatile inputs and a couple of other fairly minor enhancements, but the B replaced the A, it wasn't a case of one model being for different markets simultaneously with the other. So a B model will be newer than an A, and can do everything the A can, plus a little bit more.

I've used both versions pretty heavily over the last dozen years at work. Either did what I needed. I was developing new transceivers to meet aviation certification specs.

It'll get you going, and think about a spectrum analyser for later. An analyser will show you further things, but isn't quite a true alternative to a distortion meter. The analogue analyser will show you harmonic amplitudes but not their phases, so you can't just add them to get total distortion. The FFT analyser can, but by then it's working like a soundcard and software, it's only the packaging which is different.

Come to think of it, I have two audio spectrum analysers, the other one only goes down to 200Hz, but it does go up to 22GHz. The R&D project name for that thing was "Doomsday Box"! Bill used one when he was developing what later became the early Linn amplifiers.

David

Re: HP Oscillators
 

There is also the tektronix AA501 D/A + SG505 osc + frame, as an alternative to the HP8903 D/A, BUT it is really small and a total :censored: to work on. Sadly neither will be cheap. I use the tek with an HP3585A S/A but I bought these when the price was a lot lower.

I see you don't like the FFT computer route but it would be MUCH cheaper than the D/A + S/A alternative and can be made more 'robust' by using a front end, eg Jan Didden's 'auto-ranger'. Its a pity there is no analogue FT analyser, until you get to infa-red (?) :)

dc

Re: HP Oscillators
 

Just to add the AWA G232 and G233 which are both very low distortion (.001%) oscillators and I use them with a pair of AWA F242 automatic distortion analysers along with an HP8903A and a HP3580A.

John

Re: HP Oscillators
 

I use my trusty HP 209A, output amplitude essentially flat between 20Hz to 200kHz and great for checking RIAA amplifier characteristics.