Purifi 1ET7040SA Tube preamp

[Koifarm]

 

[Carl_Huff]

The new Purifi 1ET7040SA Class-D module has a new 54 pin connector so previous 1ET400A pre amp boards would not optimal fit.
My previous 1ET400A board(36 pin) i have adjusted for the 1ET7040SA(54 pin) but new board is downward compatible with 1ET400A(and NC500).
Previous thread: https://www.diyaudio.com/community/...urifi-1et400a-amps.379211/page-3#post-7046086

Koifarm, I am impressed with the projects that you have been posting. I plan to build them all. Please keep them coming.

 

[platon.rado]

Thanks Koifarm,

 

[Koifarm]

There was a trace missing from VDR +(H3) to pin 17(H2).
I have corrected the files in post 1.

 

[platon.rado]

Super,Thank you very much

 

[NEXTLEVEL5]

Wow, this is very impressive? Does it give it that typical tube like sound coming from the amp when used? Do you sell these?

Thanks

 

[Koifarm]

No it give no typical SE tube sound, but I experience a less wider soundstage were voices coming more foreward. It is less analitical as with a opamp input buffer.
I do not sell these PCB's.. With the gerberfiles in post 1 you can let fabricate them yourself.

 

[bisouxxx]

Hi,

So with your tube buffer you did experience a less wider soundstage ? 🤔

 

[Koifarm]

Sorry for my bad english. I meant a bit wider soundstage.

 

[bisouxxx]

Much better 😅 I started to order all the parts to build your 7040 tube buffer . Still trugling with the 7040 L pins connector .also,regards resistors , 1/4w or 1/5w ones are needed ? Regarding the caps, special brand/ model/type advised ? Like pins distances, diameter, voltage etc ...

Is this smps connector OK :
https://a.aliexpress.com/_EJaSFVr

Is this jack xlr compatible with your board ? :
https://a.aliexpress.com/_EJqaRTT

Are these ceramic tube support compatible with your board ?:
https://a.aliexpress.com/_EuqPtRL


Also, regarding the tube smps, I ordered the amie express one, but Read in the comments an other caps 470uf350v is needed to remove an eventual hummm noise. What do you think?
Sorry for all my questions 😅

That's the smps I ordered , 2, one for each buffer board right ?
https://a.aliexpress.com/_EJPLthn

Also, if I manage to get 7040 purifi amplifier boards, which smps do you advise ? The standard smps1200a700?

Thank you again
Emmanuel

 

[Koifarm]

Resistors are 1/4 or 1/2 Watt except the ones noted 3Watt in the schematic. Also in the schematic the minimun voltage of the capacitors. About sizes look at the PCB layout, PCB is 100 x 160mm.

The SMPS does not stated the output current. You need minimal 3.5A heater current and at least 100mA for the anode supply of the two boards. Normally one smps is enough. Just try the smps, you can always use an extra filter.

https://www.diyaudio.com/community/...-follower-or-srpp.388295/page-10#post-7271674

The tube socket are right.

 

[bisouxxx]

Yep I had already seen your extra filter that's why I asked you, thanks a lot,
I'm not finding the 3lignes black 90degrees connector fleeting the 7040 on aliexpress 😒

 

[Koifarm]

The 54 pin i have seen only at farnell, digikey or rs online. It is not a common part and expensive.

 

[bisouxxx]

👍 I will Check

 

[bisouxxx]

I still don't understand how your board can gain xxx without op amp while other tube amps has 1,2,3 op amps to ride the input power needed by the purifi boards ... Is that because of the tubes ?

 

[Koifarm]

The tubes have a selectable voltage gain of 3x or 9x. When input is single ended use 9x gain, for balanced input use 3x gain.

 

[bisouxxx]

Thank you .

I will check the caps diameters and pins spacing on the pcb 👍 which caps quality /type do you advise ? For the 4 big ones I will try to find mundorf or staff like that in audiophonics .

Do you think those jack xlr are compatible with your board ? :
https://a.aliexpress.com/_EJqaRTT

 

[bisouxxx]

I'm really sorry to bother you...
I have almost buy everything , just some doubts about :

C1/c11 100nF. Which voltage and type ? (aluminium oil mkp...)

C2/c12 10uf/400v you advise mkp but they doesn't fit your pcb at all. On the picture of your board they look like big tube cap like in the speaker filter .

What are d2/d3 Led???

Is it possible to modify the pcb to write in white X3/X9 on both sides of the J3 connector to know which side to move the button to get x3 or x9 gain depending on the balanced/unbalance input.or maybe it's possible to use wires and a normal small switch on the back of the amplifier close to the jack/xlr socket to select the input type directly ?

Thanks again for your help 👍

Regards, Emmanuel

 

[Koifarm]

I used for the 100nf and 10uf capacitors MKP type 400v from solen but caps and clarity or obbligato also have mkp capacitors who will fit.

When using origenal dip switch the on position is marked on the switch. In the schematic you can see that on is 3x gain and off is 9 x gain.
Using an extern switch is also possible but the change of interference will be higher.

Led d2 and d3 have double function, they show amp on signal is high and light up the bottom of the tube with a blue glow.

 

[bisouxxx]

Hello,
Waouu thanks for tour answer again!
I saw the mkp caps after writing you, sorry.
I didn't understood the leds were the blue ones under the tubes 😂 what are their characteristics ?
Won't use the external switch because of the possible interferences 👍
Regarding the purifi 7040, a different smps power unit than the smps1200a400 1et400a is needed , no problem with compatibility with the buffer board right?
Regarding C4 I read you use a different value, from 470 to 1000uF to implement the starting time from 11 to 20 seconds . Will do the same if you confirm this 👍
Regarding the external filter for the smps power unit for the tubes, do you have a gerber for the pcb? Any advise for the inductors ?

Thank you, Emmanuel