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Deltec / DPA

Martin, if possible bring the Deltran transport next time you pop round, it would be very interesting to compare it against my stock Apollo-R! One of the annoyances of Deltec going under is I’ll not be able to source the board even if there was space in the Rega to fit it. Even so I’m curious as to how much of a performance gain is to be had.
 
I'll do that, Tony.

Similarly if you end up down this way, see what you make of the various combos that I can probably put together, into either Impulse H2s or Quad 989s.
 
Just for amusement sake - here is a Deltec DPA50S (last board revision - no smt emitter resistors but 3w wirewounds from new, the 8 upstanding parts just visible) on a torture test. I'd offered a look-over & fix for a concerned chap on the 'wam: sorted a couple of damaged fuseholders, reset bias & offset and ran it up...

The scope (and a DVM not in shot) is showing 70v pk-pk @1Khz & just short of clipping* into 4.7ohms on the heatsink (taken from a dead Creek 4040) I played with it that way for some time (with the dummy load in a bowl of water,which got...rather hot), and no change. That's 132w RMS...

DPA50Sfix.JPG



*- i.e. I couldn't see distortion on the admittedly crappy test-laptop in use then, it was still in the noise floor.
 
Tony L said:
Martin, if possible bring the Deltran transport next time you pop round, it would be very interesting to compare it against my stock Apollo-R! One of the annoyances of Deltec going under is I’ll not be able to source the board even if there was space in the Rega to fit it. Even so I’m curious as to how much of a performance gain is to be had.
Click to expand...

I'm pretty sure Chevron audio still offer Deltran upgrades for compatable CD players/transports.
 
Hi Copperjacket,

I'm not entirely sure the green/white was consistently one way round - so here is how the output cables are wired, should let you check for yourself:

50Scablesketch.gif


Note though - the power amp is inverting.
 
+ve signal impulse in, gives -ve impulse out.
It's an artifact of the design; it's not remotely important, unless you are an 'absolute phase' nut [ in which case - it still won't make a difference, but you'll drive yourself up the wall worrying about such things ;) ]
 
martin clark said:
Just for amusement sake - here is a Deltec DPA50S (last board revision - no smt emitter resistors but 3w wirewounds from new, the 8 upstanding parts just visible) on a torture test. I'd offered a look-over & fix for a concerned chap on the 'wam: sorted a couple of damaged fuseholders, reset bias & offset and ran it up...

The scope (and a DVM not in shot) is showing 70v pk-pk @1Khz & just short of clipping* into 4.7ohms on the heatsink (taken from a dead Creek 4040) I played with it that way for some time (with the dummy load in a bowl of water,which got...rather hot), and no change. That's 132w RMS...

DPA50Sfix.JPG



*- i.e. I couldn't see distortion on the admittedly crappy test-laptop in use then, it was still in the noise floor.
Click to expand...

Nice scope there Martin:) I've got a few Tek scopes and mainly use a 465 but spent ages a couple of years ago fixing up a 475 I was given 10 years before that. After about 4 days working on it I had virtually everything working fine but there were certain positions on the timebase that did weird things and it seemed to be getting worse... When I properly stripped the switch assembly I found several of the gold plated contacts missing, broken or twisted and someone had had a go at soldering them back in place... along with a small scrap of paper in the screened box just saying "sorry"!!

Ah well I may come across a replacement board some day...
 
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That Tek475A is just one of the nicest things to use. gobs of bandwidth if desired (>300Mhz) and it still just works / it's easy to get what you want out of a proper interface with a switch & a fine-adjust for almost everything. The only thing I keep meaning to do is clean the trace-finder switch. And buy or build more & different probes...

When this thing was new, a tad over 40yrs ago, the list price was comparable to what my parents then paid for the house they still live in (and the huge garden with it...) !
 
They're lovely things yes:) As you will know the 465 is identical in appearance and controls etc but 100MHz bandwidth. It still bugs me that my 475 (non "A") is not going to be fully working for the foreseeable future...
I also have a 466 analogue storage scope, 2215 (a low moment for Tek), a TDS210 digital scope (I never use it), and maybe the star of my Tek collection in many ways... A 453 which I got as virtually NOS... mint, not even any dust inside. It had a fault on the switching matrix for Alt/Chop and I believe it was probably put in abeyance due to this after maybe 6 months use for decades until I got it and fixed it.
The prices were indeed incredible! The 453 was £2000 in 1969 IIRC from seeing old price lists... and that's 50MHz (my HP 8558B spectrum analyser was about the cost of 2 houses new:eek: I got it for £600 about 8-10 years ago...) I'd like a 454 100MHz if one crops up at the right price... in some ways I'd say these are actually better than the 46* series which replaced them.
Still yearn for one of the big valve jobbies though (some have >100 valves!) but when ever they are for sale they seem to be in London, Sussex etc and I'm in Newcastle and car-less... for obvious reasons they are always "buyer collects only"!
 
We have one of the scopes in Martin's pic at MOSI for working on the SSEM replica. It's a lovely thing and I'm really only in the earliest stages of learning how to use it (others on the team have considerable electronics knowledge). I keep meaning to find a nice simple scope to have at home and better learn my way round what they do, but haven't a clue what models to look out for.
 
Tony L said:
We have one of the scopes in Martin's pic at MOSI for working on the SSEM replica. It's a lovely thing and I'm really only in the earliest stages of learning how to use it (others on the team have considerable electronics knowledge). I keep meaning to find a nice simple scope to have at home and better learn my way round what they do, but haven't a clue what models to look out for.
Click to expand...

Tek scopes are a bit special, especially the top of the range valve ones, and in many ways the pinnacle of human endeavour in analogue electronic engineering. They combine science, engineering, art and craftsmanship in a way which is unequalled by anything else... and that's a fairly common opinion on them, not just mine.

What sort of spec are you looking for and do you want modern or something vintage and nice?
 
Quite fancy something nice and vintage. Something that would teach me the basics, could show audio waves etc. I don't really fancy a modern digital thing! Don't want to pay a fortune though, say a couple of hundred quid for something nice, well laid out and fully working if not the highest spec. A good learning tool.
 
martin clark said:
+ve signal impulse in, gives -ve impulse out.
It's an artifact of the design; it's not remotely important, unless you are an 'absolute phase' nut [ in which case - it still won't make a difference, but you'll drive yourself up the wall worrying about such things ;) ]
Click to expand...
Thank you - I think!
 
Tony L said:
Quite fancy something nice and vintage. Something that would teach me the basics, could show audio waves etc. I don't really fancy a modern digital thing! Don't want to pay a fortune though, say a couple of hundred quid for something nice, well laid out and fully working if not the highest spec. A good learning tool.
Click to expand...

Don't know about fully working as it's certainly vintage but something like this could be ideal... and from Tek's all valve days. http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=122992907819
 
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