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Deltec / DPA

Tony L said:
... They made a series of mains filters called ‘The Power’ or something that were intended to isolate the DACs and preamps. Little black metal boxes with an IEC in and out. No idea what exactly was in them.
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I had 4 of these when I ran an all dpa system in the early 2000s (you know, one of these systems that I ought never to have sold ...) - they were I believe primarily RF filters and assembled with 14 inductors -some hand wound - and 15 or so capacitors. Very effective.
 
Sorry - just home from a break - but re: 'the good thump:



NO, more simply - it's daft to switch a whole system at one time and expect silence!

If the the signal source(s) aren't on-line before the poweramp is coming up, you will get a thump! This the same regardless of approach - it's no different than always turning-on your power-amp after your pre. Ditto- reverso at turn-off.

Nothing to do with DPA (or any other) source. The Theta might have either some short-output until on/ fast-dropout relays, quite possible - or a crap psu. Also quite possible.

But - switching everything on/off by one mains switch and expecting silent behaviour IS daft. You have no control over where transient LF offsets occur, and to slot something, anything , new into your concatenation of the things (products) you enjoy, and always expect silence if you treat the assemblage like that - ain't ever going to work. Sorry.

BTW - you can buy 'power sequencers ' from places like Canford Audio, that will enable you to do so safely, utterly reliably, for not much money : )
 
OK Martin, but there’s something not right. If I leave it on but not playing for a while, say another hour or two, and then play a track, it starts with a thump. Once there was a thump just when a track changed. It’s too noisy for me at the moment, I’ve taken it out of the system.
 
mandryka said:
OK Martin, but there’s something not right. If I leave it on but not playing for a while, say another hour or two, and then play a track, it starts with a thump. Once there was a thump just when a track changed. It’s too noisy for me at the moment, I’ve taken it out of the system.
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What are you using as a digital source? If a computer solution could the DPA be having trouble locking after it waking from sleep or whatever?
 
Tony L said:
What are you using as a digital source? If a computer solution could the DPA be having trouble locking after it waking from sleep or whatever?
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Well that thought prompted me to do a bit more investigation. I put the Deltec back, and swapped the Rasberry Pi/ HifiBerry for an old Squeezebox classic, and it seems much much quieter. I'm going to alert @Man in a van to this because I think he's experienced in this sort of thing.
 
Are you hooked up optically or with coax? Might be worth trying optical as it may well be a grounding thing with a switch-mode computer source. The DPA is likely only expecting a CD transport upstream. Streaming didn’t exist back when it was made.
 
I know I’ve got a bit of coax somewhere, and I’ve started to turn the whole house upside down to find it. Will report back when it turns up!

Thanks to Martin I’ve set things up so that the amp gets turned on and off in the right order, and that has dealt with the transients problem. It’s a shame that smart sockets can’t be programmed to act like power sequencers. (By the way, Canford Audio seem to have stopped selling them.)

My real reason for posting is to say how well the amp sounds with my Conrad Johnson solid state and SP1s. It’s like seasoning in cooking - like I’ve added just the right amount of salt to the sound. I expect this is system specific, and in other contexts it may not work so well, it just takes perseverance and trial and error to find the right set up for a hi fi I guess.
 
Photo of an DPA-ad from the past. The PDM One Series 2 and the QED digital reference are my favorite dacs. Both have so-called Philips Bitstream chip sets, 7350 and 7323 respectively. I use old cd and dvd players from Philips and Pioneer as transports. They read the discs fast and play all CDs unlike some modern players i have tried.

nWdOM45.jpg
 
This is memory lane : difficult to find in Australia at the time ( '90-3 ) . I think just a DAC was imported by someone . Were asking $2000 at the time which was the same as Meridian's imported DAC 203b . They both sounded detailed , but the Meridian was readily available from a full range importer who could be trusted to be available . Deltec was an unknown . Nine hundred quid equivalent in Oz at the time ........ 32% sales tax and 30% import duty . Mad taxation days of years gone by .
 
martin clark said:
Sorry - just home from a break - but re: 'the good thump:


........... it's no different than always turning-on your power-amp after your pre. Ditto- reverso at turn-off.

....
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Guitarists have great difficulty in understanding this concept : unplugging guitars , switching badly designed pedals on/off all whilst the amp is cranked.
And of course we've now got computer controlled cars that really do not like the circuit to the battery being made from the red-side.
 
Svein said:
Photo of an DPA-ad from the past. The PDM One Series 2 and the QED digital reference are my favorite dacs. ..."

I have one of these in the classifieds if anyone is interested - I agree Svein, a very nice little DAC.
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I don't suppose anyone has traced out the DSP50S or DPA50S circuit have they?
I was comparing a Chord Mojo to a DPA PDM1.2 on my much loved DSP50S and enthusiastically switching inputs which seems to have killed it slightly. It's now blowing fuses in the IEC socket and is mute via the pre output. I did managed to hear an output through the tape output before the 2nd fuse went so hoping it's not completely dead and could yet be resurrected...

 
@deltaunit - I hope I can probably help you with this - I've various versions & serviced them :)

I also have an example of that version of the pre-amp I'll need to pull out of storage to compare; let me have a think. I DO think it'll be a trivial issue to resolve; tbh - it'll likely be a very simple thing like a cooked rectifier as a result of a dead reservoir cap (there are a few typical age-related issues with these)

Likely - quite straight-forward to sort-out, & fix for a long life yet : ) Feel free to PM me with close-up pics meanwhile - I'd be very happy to help.

PS - whereabouts are you (via PM if you prefer)
 
It looks like it might have an IEC socket with integral mains filter. I've seen quite a few of those go bad, especially the Schurter branded ones. There's a X2 capacitor inside them that goes bang. Worth checking.

And I see a whole load of tantalum caps that are potentially problematic too.
 
sq225917 said:
Lol those tants are all just dying to explode...
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Don't tell me they start off yellow and turn orange when they start to blow!

martin clark said:
it'll likely be a very simple thing like a cooked rectifier as a result of a dead reservoir cap (there are a few typical age-related issues with these)

Likely - quite straight-forward to sort-out, & fix for a long life yet : ) Feel free to PM me with close-up pics meanwhile - I'd be very happy to help.

PS - whereabouts are you (via PM if you prefer)
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Thanks Martin, will PM you with some detailed shots. Up in Macclesfield, Cheshire these days. Used to be in Bristol which wouldn't have been too far from you...

It's actually been back to Jez for a new selector switch and I'm pretty sure he also replaced electrolytics at the same time so they should be ok (he didn't tell me what he thought of it but it seems he liked the volume pot, if not all of the tants in there).

I've ordered some fuses so waiting on those to arrive atm. Didn't see anything obviously blown.

Mike P said:
It looks like it might have an IEC socket with integral mains filter. I've seen quite a few of those go bad, especially the Schurter branded ones. There's a X2 capacitor inside them that goes bang. Worth checking.

And I see a whole load of tantalum caps that are potentially problematic too.
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Thanks Mike. Couldn't see anything obvious hiding behind the sheath.

 
deltaunit said:
Don't tell me they start off yellow and turn orange when they start to blow!



Thanks Martin, will PM you with some detailed shots. Up in Macclesfield, Cheshire these days. Used to be in Bristol which wouldn't have been too far from you...

It's actually been back to Jez for a new selector switch and I'm pretty sure he also replaced electrolytics at the same time so they should be ok (he didn't tell me what he thought of it but it seems he liked the volume pot, if not all of the tants in there).

I've ordered some fuses so waiting on those to arrive atm. Didn't see anything obviously blown.



Thanks Mike. Couldn't see anything obvious hiding behind the sheath.

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Ah I was wrong about the filter then, sorry. The protective sheath made it look the right shape for one of those IEC socket filters.
 
+1, as I noted via pm conversation ongoing - it's very likely a lost diode in the (tiny!) rectifier.
I've both spares, and a mint example in the dpa -accumulation, to compare parts values with. NB the blown mains fuse value is ..63mA: scope for damage, is inherently limited.

Moves are afoot : )
 
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