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Mini-Me phono preamp
Mini-Me phono preamp
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Old 5th June 2019, 04:45 PM   #121
Boydk is offline Boydk  Denmark
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Still agree with you
Except the dac output is reduced to around 15-20mV and then amplified thorugh the 6N16.... Only because I like it´s sound. Bass is tight, treble is "silky" in lack of a better word, and the mid´s are to die for... nothing less
That´s the whole reason I started messin´ with the Mini-Me in the first place... I´m in love with the way 6N16B-V reproduces the whole audio spectrum
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Old 5th June 2019, 04:58 PM   #122
Koifarm is offline Koifarm  Netherlands
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Nice, i did the same with my pcm1794 dac in my shanling cd-t100se player . About 150mv at I/V resistor and then srpp 6n6p tube stage. That i liked more then all the opamps and filtering witch there was origenal.

Last edited by Koifarm; 5th June 2019 at 05:00 PM.
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Old 5th June 2019, 05:05 PM   #123
Boydk is offline Boydk  Denmark
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Avoid opamps at any cost when possible
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Old 12th July 2019, 03:10 PM   #124
Jacky01 is offline Jacky01  Germany
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Hi Ronny, hi all,

this is my version of the Mini-Me.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

It`s a combination of 3 parts:
a smal PCB with the tubes and anode resistors, kathode resistors and R1, R20, R21;
the voltage supply, for each chanal one;
and the RIAA network with the coupling capacitors;

There is one problem:
one chanal has less than 0,3mV hum, but the other one has around 18-20mV!

I changed the tubes from left to right, than I changed the voltage supply from left to right, the hum ist still at the same chanal.
At least I changed the part with the RIAA network and the coupling capacitors from left to right and now the hum is at the other chanal.
So, this part makes the problem. I build an other part but the problem is still there.

May be someone has an idea??

Jacky
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Old 12th July 2019, 06:14 PM   #125
Koifarm is offline Koifarm  Netherlands
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Connections between the tubestages and riaa network should be as short as possible. Your layout does not have that.

Have you measure humm with shorted input?

Sometimes it works better when the heater supply is floating.
Disconnect ground heatersupply and ground anodesupply and place between the two grounds a 1uf nonpolar capacitor.
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Old 12th July 2019, 07:27 PM   #126
Jacky01 is offline Jacky01  Germany
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Hi,
thanks for your answer.
Yes input was shorted.

Connections between the tubestages and riaa network should be as short as possible. Your layout does not have that.

Ok, that`s right. But the connections at both channals have the same size. and the hum of one channal is about a factor 100 of the other.

Sometimes it works better when the heater supply is floating.
Disconnect ground heatersupply and ground anodesupply and place between the two grounds a 1uf nonpolar capacitor.


I will test it.

Jacky
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Old 19th July 2019, 11:04 AM   #127
Boydk is offline Boydk  Denmark
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Hi Jacky....
Agree with Koifarm. You really gave yourself quite a challenge, dismantling the different sections of this phonoamp instead of keeping all parts as close together as possible with a sensible layout for ground, supply´s & signal traces.
Let´s hear how it goes

Anyone else assembled this yet?? Pictures and listening impressions would be highly appreciated
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Old 20th July 2019, 11:43 PM   #128
Jazid is offline Jazid  United Kingdom
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Sorry for no reply, I have got stuck with work/life and a distraction of MC SUT loading into the phono. Have made a board for ultra low impedance carts but now want to incorporate settings for higher impedance carts as well Mini-Me phono preamp
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Old 23rd July 2019, 11:52 AM   #129
Kay Pirinha is offline Kay Pirinha  Germany
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I didn't read the whole thread, so I'm not sure if this yet has been discussed:
As for the schematics in post #1, I would not recommend to omit R1 if you opt for an impedance selector switch. A grid leak resistor is mandatory for any tube! So I'd chose, say, 1M for R1 and recalculate the selectable resistors to match the desired total resistance values.
Best regards!
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Old 23rd July 2019, 08:46 PM   #130
Jazid is offline Jazid  United Kingdom
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Thanks for the info, appreciated, but rest assured I would never build a circuit without a grid leak!
I am using a zobel in parallel with the 47k load and optimising, and now have a series of capacitors and resistors that give the flexibility to optimise my three SUTs. Measuring their performance and optimisation has been instructive for me, but I have yet to judge them against the real world, ie music...
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