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Deltec / DPA

davidsrsb said:
I have never heard of Tube Technology. I must have had this magazine 20 years and never noticed the DPA connection
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They were quite a big player in UK valve amps in the 90's and 00's... I'm surprised you haven't heard of them to be honest! They collapsed when the owners wife died in tragic circumstances and he never recovered from the grief and depression... basically had a breakdown and left customers, dealers and suppliers in the lurch... all AFAIK and IIRC etc! I cold called them in person once when living darn sarf to see if they were hiring any design engineers and had a long chat and a few coffees with the owner Zia... nothing doing... this was a few years before the tragedy.
 
I left the UK in 1997 and access to the HiFi press became very erratic. This was long before PFM etc, so it was easy to miss out.
I was interested in Rob Watts designs back then, but had not then come across John Westlake.

Ah I see, Zia Faruqi, later with Manley.
The HiFi industry keeps seeing the same few faces popping up
 
A little update.
I did replace the UA9637 but the LB remain totally silent. Recently I got similar symptoms with my BiggerBit, it mute the sound for seconds or sometimes a minute during playback and is ok again with varying intervals. It still works most of the time though. Tom/DPA_SERVICE diagnosed it to be the relay that was probably worn after more than 20 years. I replaced the relay on the Little Bit as a first test and it's working perfectly again - magic after almost two years in silence. And it sounds better than I remember too.
I hope for the same result when i do the bigger bit :)
Thanks to Tom/DPA for all help.

Pic of the LB before swapping the relay:
40396540453_6561f2eb0d_b.jpg
 
In the Enlightenment dac there are 25 (if I counted right) 33uf/40v capacitors. Any benefits replacing them with up to date equivalent capacitors?
 
At 25yrs+ old - perhaps, and only if you feel like the effort.

33uF electrolytic capacitors won't be doing anything timing or precision related, so these days, 47uF will probably fit, and a convenient standard value. Don't choose 'low-esr' types on the output of any voltage regulators. Something like Panasonic FC parts, in 47uF/50v would likely be worth looking at for all: I'm sure others will have suggestions for such things too.


(no need to worry too much either way: DPA local decoupling strategies remain pretty good at HF... SMT parts and all that)
 
The best 'upgrade' that you can give the Enlightenment DAC, is to replace the heatsink on the 317 voltage regulator with something a bit more robust. And yes Panasonic FC are exactly what I used in my recap.
 
Would a Bigger Bit DAC make sense with a Denon DCD-2560 as transport instead of as a full player? They are from the same period early 90's. The DCD-2560 sports 4x AD1862's on its own.
 
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.
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Can you please tell me what is the bias in DPA50s? Should be measured as a voltage between the measuring points T1/T2, T3/T4?
 
Leonid - with the amplifier off, you should measure about 5.6 ohms between TP1 & TP2, and TP3 & TP4 (i.e. you can verify they are connected across the 5.6ohm/3w power resistors on the board)

Then, with the amplifier powered-up, you should see 350mv DC (+/-10mV) between each pair of test points - there is a (10R) small pot to adjust. In my experience thee amplifiers generally hold bias settings quite reliably.
 
Interesting about the 203; I have an early 206 (16 bit), which I added a Bitstream 203 onto. Since then I have had a system hiatus, and have not been able to listen to it for a while, and did not have the chance to really compare with and without the 203, however, that should change soon. Where should I go these days to have the 203 upgraded to a DAC7, if I feel that the bitstream version actually adds little extra?
 
I think the PDM1-2 with SAA7350 is way better than the similar priced Bigger Bit with the DAC7 system. Both dacs existed the same time. The PDM1-2 has dual power supplies and the DH-OA32 op-amps in the output stage which may tell why it sounds more neutral, detailed and articulated than the BB.
 
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