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Gieseler Audio

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Gieseler Audio last won the day on August 31 2017

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About Gieseler Audio

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    Gold Coast
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    Australia

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  1. Gieseler Audio

    PDX DAC project

    Hey just another angle on this. The PDX has around 200v across the SPPP output stage - 100v across each tube section. (ECC88 is a dual triode) Now rawl99 (who builds the killer dac) assures me that around 75v is the sweet spot for this tube so Ben why don’t you try reducing the HT a bit & see if it sounds even better. From memory there is a 1k resistor is series with the anode of the top tube section so just try increasing this a bit until you get about 150v total across both tubes. Say try 1.5k etc. Please be careful in the HT area - leave it switched off for for at least ten minutes & check the voltage across the filter caps before making any changes. Apparently the ECC88 sounds a lot sweeter & more relalaxed at 75v vs 100v.
  2. Gieseler Audio

    PDX DAC project

    Richardo - PDX upgrade - actually that is quite a good idea considering the first few veroboard PDX’s (very embarrassing) & the first generation PCB’s all used PCM1704’s on plug in adaptor boards. Very easy to remove & plug into a new dedicated design. After that they were mounted directly on the PCB in a densely populated layout so difficult to remove without damage. Unfortunately (or fortunately) my resources are taxed to the max these days with new products I’m about to release so I’m not keen on upgrade or repair work. Certainly nothing to stop someone else taking it on though - zenelectro?? Ben unfortunately NOS PCM1704K’s from reliable sources are commanding big dollars these days ($250 - $300 each) That would make any new design with them not particularly good value for money. However if I’m totally blown away with my little prototype I may consider doing a small production run with the few I have left. I still have a soft spot for the PCM1704 so I’d much rather build something with them rather than just sell the chips.
  3. Gieseler Audio

    PDX DAC project

    Hey guys this is getting me all motivated with the PCM1704k again. I have a JLsounds I2S over USB board lying around & it certainly looks dead easy to couple it to a pair of PCM1704K’s. CAD up a PCB with lots of ultra low noise regs for everything - disable the clocks on the JLsounds & clock it from pair of Crystek Femto clocks I also happen to have lying around. Now just the IV stage & output to decide on. Maybe just the Burr Brown data sheet circuit with a OPA627/OPA2134, also lying around ha ha - lots of stuff lying around in my parts hoard that’s for sure. On second thoughts maybe not the OPA2134 - must be something better to replace that with now. Forgot to mention that I also have about ten brand spanking new PCM1704K’s as well. Open to offers!
  4. Gieseler Audio

    Gieseler DAC Reviews & Impressions

    Actually it is not looking very straight forward unfortunately. I had a close look at it today & none of the femto clocks I had came even close to fitting on the Amanero pcb. Looks like a daughter board is the only way to go. The good thing is as I will have more room I can add a couple of ultra low noise regulators to power each clock - two needed. Independent low noise PSU for each clock is definately a good way to go.
  5. Gieseler Audio

    Multi DC Output LPS

    My pleasure
  6. Gieseler Audio

    Multi DC Output LPS

    Compass - unfortunately those voltages you want are not do- able with the current suitable transformers I use. Linear series regulated PSU's need the AC input to DC output voltages fairly closely matched other wise there is a heat problem. vagabond - yes it would be possible but the 15v output would be limited to 1A The planed PSU would have dual XLR outputs - each output could be set to 9v, 12v or 15v The 9v & 12v would be rated at 1.8A but only 1A on the 15v output.
  7. Just be careful with audio style DAC’s on a AV system. You often get sync problems with speech & with a Audio/hifi style DAC there is no option to adjust that delay which normal AV gear has.
  8. Gieseler Audio

    Gieseler DAC Reviews & Impressions

    Hi John, yes currently working on that at the moment. I have some Crystek Femto clocks but they are about double the size of the ones on the Amanero so not a drop in replacement unfortunately. Crystek do make ones in the correct size but they don’t have an enable (remote on pin) I need that option to be compatible with the Amanero control circuitry. I have two options. 1. Use the correct larger size clocks but mounted on a small daughter board. 2. Use the right size drop in clocks & add extra control circuitry to be compatible with the Amanero Ah - life was not meant to be easy!
  9. Gieseler Audio

    Gieseler DAC Reviews & Impressions

    Hi Omera, I currently have a 3-input Gross in stock & lead time on a USB only unit is about a week. PM & I can give you some more info. Regards Clay
  10. Gieseler Audio

    Multi DC Output LPS

    Compass - OK let me look into it a bit more - those voltages may be possible if I use a different transformer. vagabond - OK I will look into those voltages as well & do a update tomorrow.
  11. Gieseler Audio

    Multi DC Output LPS

    Hi Guys, well with all this interest in multi output PSU's it has got me thinking that it would be worthwhile to have another crack at it. To keep maximum performance I would build two fully independent PSU's (with independent bridge rectifiers) but on the same PCB. By using independent bridge rectifiers the PSU's will be fully isolated with respect to DC from each other. Then the whole combo would be run from a high current common transformer. (12v 6A AC) Also there would be none of the disadvantages I talked with Andy about as it is a full dual PSU but with a common Transformer. The case would be old Klein DAC size (160mm x 160mm x 55mm). The unit would have two separate XLR outputs each with an "external adjustable" output of 5v, 7v & 9v. Current would be 2A per output at any voltage. Cost - roughly $500. Not a huge saving vs separate units but a lot neater in the rack. Well what do you think? It would be based on one of my brand new single PSU designs which will be released in the next few weeks. Sorry just noticed Compass wanted 12v & 19v so this would not be of much use.
  12. Gieseler Audio

    Multi DC Output LPS

    Andy both 1 & 2 will add a small amount of separation to the common supply but both methods have a negative impact. With a high quality PSU it will have a very low output impedance - say 10 to 50 milliohms. Then you add 10 OHMS in series. That is a massive increase in output impedance so performance goes way down. Voltage will sag a bit (depending on current draw) & regulation will go down significantly. The same with diodes. An average diode measures about five to seven (DC) ohms. Using two diodes (one on - & one on + ) for a pseudo type of galvinac isolation you have now added 10 to 14 ohms of series to your PSU - very bad. Also voltage drop across each diode is .6/.7v so your voltage has gone down by 1.2/1.4v. Now there are diodes with lower forward voltage drop (resistance) but they will still seriously degrade the performance of a modern high performance regulator if used on the output. Think of a high end CD player with two seperate transformers - one for digital & one for analogue. That method is often used in a company’s top model vs a single transformer in the lower models. Hope that helps.
  13. Gieseler Audio

    PDX DAC project

    That PDX originally had a on board LDR output level antenuator & the four trimmers you see were for calibration/balance setup. The antenuator has since been bypassed so the trimmers are now out of circuit and inoperative. The tube bias was about 10 ma & fixed by the SRPP stage resistor values.
  14. Gieseler Audio

    Multi DC Output LPS

    Hi Andy, independent PSU’s always work/sound better. Probably because you have eliminated any supply rail coupling between the devices via the PSU. RE seperate PSU for left & right channels. That does not actually improve the sound quality but does help improve the separation & can improve/widen the soundstage. On my latest DAC I tried replacing the single 5v regulator supplying the analogue section of the DAC chip with dual regulators - one for each channel. It was not a big change but definitely seem to widen the soundstage & improved the left/right separation.
  15. Gieseler Audio

    Preamplifier owners thread

    Oh well that's great the ext transformer is ok. Actually I must have used about 200+ of the 9v units & haven't had a failure - touch wood! That's good you have it sorted - unusual for a fuse to blow but may have just been a power surge.
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