noDAC DHT output stage

[Hearinspace]

Thanks !

 

[merlin el mago]

You're welcome.

@ abraxalito
Done the filter yesterday and enjoyed all the evening & night listening music, a big thanks again.

About step up transformers I guess I need 1:1.27 my calculations:

0.56Vrms = 1.58Vpp
0.71Vrms = 2Vpp

So I need to increase 0.15Vrms to reach the 2Vpp, it's OK.

Also I need an OPT with primary impedance of 50 Ohm & a secondary of 63.5 Ohm

Are my calculations OK?

 

[merlin el mago]

Nobody?

 

[Tjj226]

You're welcome.

@ abraxalito
Done the filter yesterday and enjoyed all the evening & night listening music, a big thanks again.

About step up transformers I guess I need 1:1.27 my calculations:

0.56Vrms = 1.58Vpp
0.71Vrms = 2Vpp

So I need to increase 0.15Vrms to reach the 2Vpp, it's OK.

Also I need an OPT with primary impedance of 50 Ohm & a secondary of 63.5 Ohm

Are my calculations OK?

Are you sure you want 2vpp? Most digital signal sources are 2v RMS.

I would just go with a plain old 1:2 step up transformer. That would give you 1v rms out.

 

[merlin el mago]

I'm sorry yes for 2Vrms, so I will need 1:4 ratio, primary 50 ohms & secondary 200 ohms, that's?

 

[U130421]

The impedance ratio is the square of the transformer's winding ratio . Most ready made transformers for audio are 600 ohms . What you need is 600:10k . See on Aliexpress .

 

[merlin el mago]

The impedance ratio is the square of the transformer's winding ratio . Most ready made transformers for audio are 600 ohms . What you need is 600:10k . See on Aliexpress .

Yes I forgot thanks, I need a primary impedance of 50 ohms because is the output impedance of Amanero and the input/output impedance of the 4th order low pass filter so I need a custom made OPT 50:833 ohms 1:16 ratio?

What have I to look for: Line input transformer or Step-up MC transformer?

 

[merlin el mago]

@ abraxalito
I want to use the 1:1 OPT for a gain of 6dB (attached pic), could still use your filter without modification?

 

[merlin el mago]

Still looking for DHT analog stage advice, after looking for I saw 3A5 that Ale Moglia praised for "small signal amplification"

"A very nice result I think. THD of 0.03% is outstanding for small signal indeed. Look at how close H3 is to H2, interesting to see that."

Ale Moglia schematic:

Now I'm using 5687 triode SE with hybrid mu-follower from Ale Moglia and it have more gain than the phono preamp MM Valve Itch, so a little less gain than 5687 fit perfect the gain.

Can you suggest other possibilities?

 

[woodturner-fran]

I have started down the same path as you @merlin el mago

3a5 output stage advice

I have been testing out various supplies - and have been listening for a bit trying to decide whether to continue or go down a different route. 3a5 are certainly microphonic, and I think a regulated B+ and coleman type heaters will be needed. I hope to get looking at it again this week.

I'd be interested to hear your thoughts.

 

[merlin el mago]

Thanks Fran, I follow your thread.

 

[minhaj]

merlin....I give you one cheap solution. You can have 3a5 in parafeed config-resistor loaded 3a5 output via 10k:600ohms line transformer. Gain should be 3x. Coupling cap should be 4.7uf. For filament you can use 317 voltage regulator followed by 317 CCS for 220ma. I use it (with 15k:600 for about 2.5x gain) as my preamp with wonderful sound.

Regards

 

[merlin el mago]

minhaj that's a great idea to try before to buy Rod Coleman regs. once I tried 317 CCS as anode load and didn't liked.

Cheers

 

[ra7]

Hi Merlin, Others,

I'm trying to learn about the no DAC solution and have seen some threads here. My current DAC, ADI-2 Pro, also outputs a DSD direct stream that I believe bypasses the DAC. However, I want to explore other solutions. I am trying to understand how other solutions work. Looking at post 9, it seems an Amanero USB transport can be used with the filter shown to get the output. Am I understanding that correctly? Is anything else needed?

Thanks for the help!

 

[merlin el mago]

It all depends the filter order?

The filter at post 9 it's a 4th LPF with a characteristic impedance of 1.5K not ideal for Amanero with a output impedance of 50R.

 

[ra7]

Okay, but apart from the filter order, is anything else needed? What other solutions exist? Thanks!

 

[merlin el mago]

The characteristic impedance of filter must match the output impedance of the filter, the LPF order & cutoff it's up to you. BTW I use 4th order LPF with characteristic impedance of 50 ohms.