Universal PCB for Purifi 1ET400A amps

[_henry_]

C4 of the mute timing circuit i changed from 470uf to 1000uf because of the short time. Tubes are not hot enough after 11 sec witch results in a popping on noise. Now it is about 20 sec.

hi @Koifarm
if i want to extend the muting to 30secs, what value should i use for the cap?
im testing linear psu, it only stable at 27secs or so and causing the nc500 to go into protection.

We are using R21-22k, R22-1k and BC547 per schematic.

thank you

 

[Koifarm]

Did you already test. If yes, with witch capacitor value at what was the time?
Or just try 1500uf.

 

[_henry_]

with C4 1000uf and R21 22k, it is 12seconds now.

 

[_henry_]

@Koifarm
to be clear,
so following the schematic
im using
KEMET EC2-5NU relay
R21 - 22k
Q1 is BC547
C4 is 1000uf/16v

the relay made the click sound at 6 secs actually.

i tried 2200uf, it still the same 6second.

thanks

 

[Koifarm]

6 sec is to fast. Then try to higher R21 to 56k or 100k.

 

[_henry_]

I tried 47k still 6secs, however 100k didnt trigger the relay, waited for 3mins.

 

[Koifarm]

I just discovered a mixup of R21 and R22 on the board text. R21 on the board is R22 in the schematic. And R22 on the board is R21 on the schematic. Thats why the delay did not function right.

 

[_henry_]

thanks @Koifarm

 

[bisouxxx]

Thank you for the clarification 👍
Do you confirm 6.35mm MONO jacks (not stereo) has to be used for unbalnaced rca signal on the neutrik NCJ6FAH

 

[Koifarm]

Yes, use the mono adapters.

 

[dvb projekt]

@Koifarm

Very interesting thread!
Are there any updates to your project? BTW, what are you thingking of the way VTV is going?
Any pro-/con- to your design from your pov?

Description​

The outstanding quality of Class D amps has many customers switching to Class D from vacuum tubes. This actually describes me. I have been a lifelong tube amplifier enthusiast. So I developed the VTV Custom Tube Buffer for those looking for a warmer and more tube-like presentation that showcases smooth, warm mids along with a holographic sound stage—– the VTV Custom Tube Buffer is now available!​

Designed by Andrew Sparks of Sparkos labs, the buffer features a direct coupled dual triode driving a four transistor Wilson current mirror. The output of the current mirror feeds an I to V converter stage featuring a discrete opamp (of your choice). The board is compatible with almost any dual (or two single) opamps.​

There are NO capacitors in the signal path.​

The VTV Tube Buffer is compatible with all NCore and Purifi models and installs just like the standard VTV Custom Buffer.​

Features:​

–Fully powered by the SMPS Power supply.​

–Accepts 6922, 6DJ8 or E88C vacuum tube. Opamp choice is also flexible.​

–Board includes Genalex Gold Lion 6922 Gold Pin tube​

–High-end Sparkos low noise 15V regulators. Vast improvement in noise over standard 7815 and 7915 in the stock Hypex/Purifi buffers​

 

[bisouxxx]

Good day.
I finally had some times to assemble the tubes buffer boards, 2caps are missing then play 😅
Will let you know.

Regards

 

[Koifarm]

About the VTV I have no opinion because it is to expensive for me.

I use the purifi modules without a buffer. This fits my experience "less is more". When I need some gain then I keep it as simple as possible.
But most important is to listen if you like the sound.

 

[bisouxxx]

Input impedance is quit high. RCA is 100k and XLR is 200k. No problem for any source.

If required you can define the impedance by changing R1 and R11.

Good day
About the input impedance, 100k/200k for tube, why are the input R values different between the tube and mono buffer? (tube 10k/100k and mono 100ohms/10k)
Do you know what is the current drained by the mono buffer aop version ?
Also, when diminuing the value of r7/r8 on the mono, I lost a lot of basses (which was too much with 25k instead of 3.3k) do you know why the feedback R influe on the basses?

Thank you again

 

[Koifarm]

Tube and opamp version have same input impedance of 100k single ended and 200k balanced.
The monobuffer drains about average 10mA but varies with used opamp.
Changing R7/R8 from 25k to 3k3 has a lot. of influence, and more when C1 to C4 is 100n and not 100p.

 

[bisouxxx]

The 100 pico caps should arrive tomorrow 👌 so I hope to be able to test both mono and tubes buffers tomorrow

 

[bisouxxx]

I'm trying to find out what is the effect of the R value of feedback on the sound ? Does it change the sound frequency response and dynamic ?
Thanks

 

[bisouxxx]

Koifarm,

What's the purpose of the connector H1 on the tuber buffer board ?
Also, is it possible to arrange the gain on the tube buffer board as on the mini buffer one with R6?
Thank you again

 

[Koifarm]

The connector has Left(+), ground and right(-)signal out. For test or measurements. Or use the PCB as stand alone preamp.

You can not adjust gain of the tube buffer with just one resistor. But by changing R10/20 you can change gain

https://www.diyaudio.com/community/...c85-6922-6dj8-etc-mu-follower-or-srpp.388295/

 

[bisouxxx]

Good day, I'm a bit disappointed .
Just plug the tubes buffers , less come in after 4 seconds, but not sound at all 😭😭😭 I don't understand why .all looks good !!!
The new mono buffers work very nice now with the 100pF c1...c4 👍