Thank you very much Johnny C-Hing for the pictures and the schematic....by looking at the pictures and the drawing, I don't think I have the knowhow to put the stuff together. I guess I will just buy something that is assembled or upgrade my pre-amp in year or so.

Thanks again.

The input RC are 1K ohm and 0.01uF.

Picture 2

Picture

Here's the schematic:-

Hi Johnnykmtang C-Hing....do you mind post pictures and schematic of your device? I am interested in making one.

I recently acquired a OKTO DAC 8 that has XLR output only but my Audio Research SP6 has single-ended input only. I made a pair of XLR to RCA cables and it works but I know the transformer option is the way to go and recommended by OKTO which is why I would like to make one especially you mentioned it is not that difficult.

Down the road I plan to update the pre-amp but before I have money to do so, I think your device is a good solution. Thank you very much in advance.

Nice
Thanks for the insight BenYC

My transformers are 1:1 (600 ohm:600 ohm).

Passive or active is very system depending. I am using quite efficient horns with active crossovers, thus I don't need much gain from pre. For me, no noise is much prioritized.

Thanks BenYC
Are your transformers 1:1?
My passive pre has an active buffer stage with +3dB I can engage and I agree with you when in active mode the bass is more authoritative and the soundstage is much 'closer', at the same sound volume level.
But then I also wonder could the active stage 'coloured' the sound?
May be the passive sound was meant to be what was recorded?
The passive sound is bigger, more relaxed and recessed, which is what I prefer.

I guess it's more setup related. My potentiometer calls for 2 interstage transformers in order to get the 100 db adjustment scale accurate.

In my previous experience using other passive pre with just one transformer, the volume knob had too much correlation with the bass quality. At lower volume, bass was severely lacking.... Needed to turn up much to sound ok normal. I ended up switching back to using active pre. Now I am back to passive again but no more problem this time.

(I listen at late night. Passive has the quietness that matches my priority better.)

Hi BenYC
I see
Thought only the Zout changes as the volume changes and worst Zout is at -6dB.
Zin should remain the same?
My DAC Zout is 3ohm so low enough to drive anything.
I am using 2 step downs in parallel after the passive preamp to lower the Zout as I am connecting to a pair of active speakers and a pair of subwoofers

#28

When hooking dac directly to potentiometer, when volume change the resistance/impedance changed. How importance is this depends on each setup. Thus I suggest to try.

I uses 2 for each channel as stated.

Hi BenYC

What is the rationale of using a transformer before the pot please?

Speaking of which I was using a transformer before the passive preamp but somehow after changing the DAC it significantly shifted the soundstage to one side and I could not figure out why.

So now I am just connecting the DAC to the passive preamp directly.

A side note.

If using transformers for passive pre, it worths trying to use 2 transformers per channel.

Source ＞ transformer ＞ potentiometer ＞ transformer ＞ amp

Here's the datasheet from Jensen transformer. Good reference for XLR to SE conversion.

https://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-11p-1bn.pdf

Yes, the line transformer can be used for either step up, step down, or 1:1.

The very nice thing it is the perfect adaptor for Balanced-SE or SE-Balanced.

Johnny

#22
Thanks for the advice
I do use transformers (Jensen) in my system.
Reason being I use a passive preamp and in order to ensure the impedance bridging I am using a 2:1 step down for the main speakers and another output from the preamp to a 4:1 step down for the 2 subwoofers.

#23
Despite so I still have plenty of gain (DAC 4.6V balanced out 3ohm Zout) and only using around third of the volume control.

Johnny hing

睇見你的分享忽然間有個wonder

Anyone.. Using a step down, let's say.. A DAC having quite high XLR output let's say. 4V range or even higher

Step it down to 1V to 2V range, and feed to a true balance pre amp?

I do wonder.. Is it a true balance system having better dynamic or overall lower noise hence people enjoy it more..?

I have a complicate feeling, I do not know why I enjoy a true balance set up, was it because of better dynamic etc... Or sense of ownership affected my own perception... I never sure..

I had some grest time for single end system, the aspect of better 3D feeling

I had some great time from some balance system.. Too

Such tranformer seem great for some MC SUT application, especially for some above 0.5mv but below 1mv

Thx for sharing

Hi MichaelWittmann,

Well, it isn't difficult to build the XLR/RCA box. Just few tools that you would need. Soldering Iron, cordless drill, step bit, and small files.

By the way, I can post some more pictures how it look inside the box and the schematic if anyone interested.

Maybe you can ask someone at R33 for help.

I bought the Hammond line transformer from Mouser for about C$110 each. Price is quite reasonable.

Johnny

最後修改時間: 2024-07-11 14:57:44

Ah yes
Sorry misread it was the impedance 2.4k:40k which is ~16 times and turns ratio 1:4
Nice work
I wish I am hands on like you and some others here then I can DIY