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Buffalo II & transformers

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I use Belleson mini they are really good. But take care if not done right they are oscillating. Burned a sabre chip

I have seen oscillations in other also "recommended" shunt regulators... I personally do not like to have regulators at such oscillations edge working domain. Think that the components get aged somehow, or it may modify its parameters with ambient temperature. Any small instability of the regulator circuits, can (uncontrolled) produce unexpected anomalies at any time...
ADM7151 is a very stable device, no any oscillations whatsoever on its whole working domain, and provide the lowest noise on marked right now...
It is my last choice... with excellent results.
 
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These are my regulators....
 

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Hoping for some insight into my implementation of a transformer output for my buffalo III in stereo mode.
I read the 622 posts and it seems easy enough so I tried using a pair of Jensen JT-11P-1 transformers in place of the legato I have been using. First I hooked it directly to the dacs output and then tried the attached schematic. Same problem both ways. The music plays but there is a high frequency sort of pulse tone. Not sure where to go.
Thanks,
Evan

Just so I'm clear the two 330r resistors go to the dacs ground pin between the differential outputs.
 

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Hoping for some insight into my implementation of a transformer output for my buffalo III in stereo mode.
I read the 622 posts and it seems easy enough so I tried using a pair of Jensen JT-11P-1 transformers in place of the legato I have been using. First I hooked it directly to the dacs output and then tried the attached schematic. Same problem both ways. The music plays but there is a high frequency sort of pulse tone. Not sure where to go.
Thanks,
Evan

Just so I'm clear the two 330r resistors go to the dacs ground pin between the differential outputs.

Hello Evan,

I took a different approach and used a high primary inductance transformer (Lundahl LL1676) on the DAC output, with no ground connection on the primary side. With the high primary inductance there's no need to worry at all about the output impedance of the DAC. That feeds a DHT tube output stage. It sounds fantastic - highly detailed but not at all harsh.

Feel free to stop by and have a listen if you'd like to check it out.

Bob
 
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Bob,
Thanks for Checking in. I used the Jensen transformers because I had them on hand. Ended up with 680r from each leg of the primary to ground. Any lower gave up too much gain in my system. No pramp here just a buffer.


Turns out the hum problem was grounding. The whole dac system was floating...no connection to ground at all. Worked fine with the ivyIII as the output for the dac not so for the transformers as the output. I tied the dac power supply to ground and voila no hum at all. The output transformer secondaries are still not connected to ground. The sound going from active to passive changed a bit....but not much. Maybe a bit of distortion has crept in...sounds more direct. Much simpler this way. I doubt I'll go back.

We'll have to make a time to give your system a listen
Thanks,
Evan
 
Brian,
I can scope before and after the transformers this week. Sorry for the poor photo. Hard to do in place. I used a right angle header under the board hooking the +- output of the DAC to the transformers. The resistors to ground can be plugged/unplugged easily enough. Subjectively grounding the power supply has worked. No noize-humm-buzz. The sound is very close to what it was running through the ivyIII.
Thanks,
E
 

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May I ask about an update ? Is the common wisdom:

A. Joe's approach: Use a 3 ohm resistor network at the primary to give a really low impedance, attach a 1:20/1:30 xfr, and finally let it work into a tube-output stage like a 45 or a 801a ?

or

B. use a 60 ohm resisor at from grid to ground as i/v resistor and have a direct signal which does not go through a xfr at all ?

I am running B. with a differential Amp/LTP of 801A currently...in combination with a dual mono-BIII setup. I want a voltage swing of 16vpp as I can drive with this my 300B PP with only one additional stage.

Anyone tried both ?

Best Regards
 
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That's sounds about right. Unlike other delta-sigma DACs, the 9018 can work into almost any impedance, even a short (no point doing that). This means a great deal of latitude as to what can be done, experimentation etc. But keep in mind, the transformer does like to see a low impedance on the input/Primary side, so I would not use anything higher that 100R there, and maybe listen to improvements if you lower it, although final output will be lower. But have fun playing around with it.
.
 
Hoping for some insight into my implementation of a transformer output for my buffalo III in stereo mode.
I read the 622 posts and it seems easy enough so I tried using a pair of Jensen JT-11P-1 transformers in place of the legato I have been using. First I hooked it directly to the dacs output and then tried the attached schematic. Same problem both ways. The music plays but there is a high frequency sort of pulse tone. Not sure where to go.
Thanks,
Evan

Just so I'm clear the two 330r resistors go to the dacs ground pin between the differential outputs.

To be honest, this confuses me a bit....was the whole point not to get really down in impedance to bring the DACs into current mode....and now 330R ? What for ? We are here in voltage mode, no ?
 
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