6J1 tube upgrade

[ginetto61]

It took me long you are very right. But i have understood now that this is not the right tube for my needs. I am moving to the 6N3 tube now with the SainSmart unit i ordered
I really do not understand why they have used smd in a tube unit ... and the pot at the output.
When all other designers do differently there must be a good reason not to follow the mainstream ... a very good one that i fail to see
I like what tubes give to the sound. I am dragged more into the music and the sound is more relaxing. A possible issue could be the driving ability with solid state power amps with low Z input.
Thanks a lot again for the very helpful support. I was intrigued by the sound ... now that i understand that a better sound can be obtained i want that.

 

[FlaCharlie]

You are right. But i get confused when for instance in the case of the FX audio i like the sound and then knowledged people trounce the design quite brutally. I am not saying that they are wrong actually i am pretty sure they are right. But how can i be sure that a schematic is well calculated and can provide great performance ? a leap of faith ? usually there are no measurements to support those claims ... and then measurements tell very little ... so my complete confusion.

The FX sounds better than you would expect, considering its flaws. But it's not difficult to put something together that sounds much better.

For a tube newbie it is difficult to figure out whether a particular design is well thought out or not. Asking for advice on these forums can help but, particularly on this forum, sometimes the comments are hard to understand because so many of the posters here are used to discussing things in highly technical terms and they assume that others have the same high level of expertise.

A buffer is, however, a very simple circuit. The design I suggested in the link is simple and every detail is explained so that a newbie can understand it. It's the website of the guy who posts here under the name Sodacose. If you were building it and had questions, I'm sure he is available. That's an important factor to consider.

I doubt there is any support available for builders of the SainSmart, either from the seller or from the designer, whoever that might be.

A quite complex design and still flawed that one of the FX audio ... my guess is that for some reasons they have wanted to keep voltages low. With a negative impact on performance. And even with more adequate voltages the tubes chosen are not the best available. Maybe they are very cheap

The FX design is all about low cost of production. A PS that runs off a wall wart and uses SMD parts on a board that is assembled by machines is much cheaper to produce.

The tube types were chosen for the same reason. They are not in current production. There were huge stocks available at super low prices because, until these preamps were developed, there were no commercial products that still used them. From a manufacturer's point of view, they are perfect.

But the fact that a design even so flawed can sounds pretty good excites me and provides me with the motivation to go further. That is better tube ... better design ... maybe not the ultimate buffer but a very decent one.

The sound quality of the FX is reasonable enough and the super low price creates a huge potential market. A growing number of people are curious about tube audio and this is a great entry level device. Of course, tube newbies don't have any other reference points to compare to the FX. But if it gets more people interested in tubes, that's great.

... for now i can hope to assemble/mod something already tested and with all instructions.

I have bought one. I am going to use just RO1 and take the signal out of the cathode before R5 I guess could even take out R02 ?
Therefore R01 will work as a plain buffer.

That will not work.

Compare the SainSmart schematic to the buffer in the link I posted. You will see that they are completely different.

Neither one of the sections is configured as a buffer (they are dual triodes, so what you're seeing in the schematic is a single tube). They both take the signal from the plate, not the cathode. You can't just disconnect the second section of the 6N3 and run a jumper wire from the first section to the output.

You would need to completely redesign the circuit.

Now, if this was built using point to point wiring it wouldn't be too hard to modify but with a circuit board it's not so easy. It will require additional parts in different values. How will you mount those additional parts? You can't just drop them into the existing holes in the board because the traces don't go where you need them to go.

That's why you're better off building something than trying to modify a totally different design into a buffer.

I really do not understand why they have used smd in a tube unit ... and the pot at the output.
When all other designers do differently there must be a good reason not to follow the mainstream ... a very good one that i fail to see

Again, the use of SMD parts is all about keeping production costs down. As I recall, one poster in that thread said his unit used regular sized parts. Who knows what will come in yours.

My technical knowledge is not so great so I don't know why they used a pot on the output. The pot at the output was discussed in the thread that has the schematic. You should read it again.

It seems to create problems. Apparently it affects the feedback loop - something else that will make it more difficult to modify the SainSmart board. And who knows why they thought it should have feedback at all in a preamp. The person who posted those comments about the shortcomings of this design posts here under the same name, rongon. His technical knowledge is obviously much deeper than mine.

Bottom line . . . you'll be much better off building a simple circuit that is designed from the start as a true buffer. The one in the link I posted is as simple as it gets.

Instead, you're going to be trying to hack apart a totally different circuit and make a buffer out of it. You're wasting your time and money using this approach.

 

[ginetto61]

The FX sounds better than you would expect, considering its flaws. But it's not difficult to put something together that sounds much better ... A buffer is, however, a very simple circuit ... The FX design is all about low cost of production. A PS that runs off a wall wart and uses SMD parts on a board that is assembled by machines is much cheaper to produce... The tube types were chosen for the same reason. They are not in current production. There were huge stocks available at super low prices because, until these preamps were developed, there were no commercial products that still used them. From a manufacturer's point of view, they are perfect...

Hi perfect i understand the idea. To propose simple units very cheap and with a musical sound. I think they have centered the objective.
But i am leaving the unit. I would like something pretty definitive

That will not work.

Sorry. You mean that if i take the signal out directly from the cathode pins on the 1st tube that will not act as a buffer ? i intend to use just the 1st tube and take out everything else I will leave it even without volume control. Just a plain buffer. And i will have to add just two output 4uF caps soldered to the cathode pins of the 1st tube and prune out what is not needed. I do not need voltage gain at all. I just need a buffer able to drive 10k Zin power amps.

Compare the SainSmart schematic to the buffer in the link I posted. You will see that they are completely different.

i do not question that for sure. Very different design. I agree.

Neither one of the sections is configured as a buffer (they are dual triodes, so what you're seeing in the schematic is a single tube). They both take the signal from the plate, not the cathode... You would need to completely redesign the circuit.

for this i want to take the signal out from cathode pins directly ... that are pin 2 (one channel) and pin 8 (the other channel)
I will have just to soldered two of these ... one for each pin

Moreover i wonder if i could do the same in any tube preamp kit i can found around ? just take out the signal from the cathode pins on the 1st tube ... possibly a 12au7 at this point ... maybe swapping it for a 12bh7 ? i will check if the power supply is up to the task of course

Now, if this was built using point to point wiring it wouldn't be too hard to modify but with a circuit board it's not so easy. It will require additional parts in different values. How will you mount those additional parts? You can't just drop them into the existing holes in the board because the traces don't go where you need them to go.

my intention is to try first if it works and how it sounds. If it sounds ok then i can also buy a new case and put all in it
I have already bought some silicone sheets that should isolate the pcb from the metallic case ... i have to check the specs because of the high voltages on the board.

That's why you're better off building something than trying to modify a totally different design into a buffer.

i really would like to start from a pcb ... that would facilitate the task
And i guess one tube should be enough

Again, the use of SMD parts is all about keeping production costs down. As I recall, one poster in that thread said his unit used regular sized parts. Who knows what will come in yours.

i will open and take pics ... i really hope they will be regular size. SMD is a pita.

My technical knowledge is not so great so I don't know why they used a pot on the output. The pot at the output was discussed in the thread that has the schematic. You should read it again. It seems to create problems ...

the fact that almost no preamp use this solution is more than enough for me
A silly solution that can create huge Z out issues ...
A good pot will be completely transparent ... orders of magnitude more transparent than any circuit. Silly solution.

Bottom line . . . you'll be much better off building a simple circuit that is designed from the start as a true buffer. The one in the link I posted is as simple as it gets.
Instead, you're going to be trying to hack apart a totally different circuit and make a buffer out of it. You're wasting your time and money using this approach.

Thanks a lot but again any preamp kit will work in my mind as a buffer just taking the signal out directly from the cathode pins ... adding of course a dc coupling cap.
Regarding this after measuring the actual voltages on the cathode pins i am thinking to use high quality electrolytic like 100uF bypassed with 0.1uF plastic cap. Millennia use this solution in their ultra-transparent SOTA mic preamps. If it is good for them ...

 

[Yatsushiro]

 

[JMFahey]

Those are the flies

 

[batteryman]

Here's a useful website: The Valve Wizard -Cathode Follower


The above page is AC coupled cathode follower buffers

 

[ginetto61]

Hi thanks for the very kind and helpful link
My very basic and maybe trivial question is that any tube in any design can work as cathode follower if i take the signal out of its cathode
Some advantages of cf are a lower Zout and a good psrr if i got it right
It would be a handy solution to provide more musicality to an all solid state chain

 

[FlaCharlie]

Those are the flies

Cause of death: Dehydration

 

[batteryman]

Yes, 100% negative feedback so like an op-amp buffer with -ve input connected to the output.


Saying it will add musicality is inviting a debate over which tube to use, because like op-amps, everyone has their favourite.

 

[ginetto61]

Yes, 100% negative feedback so like an op-amp buffer with -ve input connected to the output

Thanks a lot ! i am very uneducated in electronics but i had that feeling
This is very important to me ... i have ideas
I feel that just one tube can bring some light in my dark playback system ...

Saying it will add musicality is inviting a debate over which tube to use, because like op-amps, everyone has their favourite

i see. I will stay basic as a start. I know of much more complex schematic of buffer like the white cathode follower ?
New Adventures in the White Cathode Follower
Better to be basic at the beginning
Thanks a lot again.
Kind regards, gino

 

[Wavebourn]

6N3 is a copy of a Soviet 6N3P tube that was used in transmitters and receivers. 6J1P and 6N3P were the cheapest and most common tubes in radio communications for government. China used in their railways copies of Soviet railway transceivers ЖР3-М so warehouses were full of 6J1 and 6N3 tubes. So, they have surplus of them and use in their kits, while much better tubes are available.

 

[ginetto61]

6N3 is a copy of a Soviet 6N3P tube that was used in transmitters and receivers. 6J1P and 6N3P were the cheapest and most common tubes in radio communications for government. China used in their railways copies of Soviet railway transceivers ЖР3-М so warehouses were full of 6J1 and 6N3 tubes. So, they have surplus of them and use in their kits, while much better tubes are available.

Hi thanks a lot for the very interesting information.
One thing that from a beginner pov i do not like is to find schematic that are not true to the actual unit. They are just confusing simple minds.
What i intend to do is to sacrifice one of the three FX audio 01 units i have to try to use it as a plain buffer, taking the signal directly from the cathode pin ... and listen. I really like what this cheap, limited badly implemented tube is giving to the sound. A lot actually. I am watching tv serials ... the voice are not very thick (they say palpable) but they are very natural. It is impressive.
I am more involved in the listening.
Moreover i am waiting for a 6N3 unit and intend to do exactly the same. Use it as a buffer taking out even the volume control placed weirdly at the output
I understand that this choice can trigger many issues. I have never seen a preamp with a volume control at the output. There is always some kind of buffering after the pot. Always.

 

[FlaCharlie]

What i intend to do is to sacrifice one of the three FX audio 01 units i have to try to use it as a plain buffer, taking the signal directly from the cathode pin ... and listen.

Moreover i am waiting for a 6N3 unit and intend to do exactly the same.

I just saw this suggested in another thread. It seems to be exactly what you're after in that it is actually a buffer, it can use 12BH7s and it runs off a 12v wall wart. The designer is widely recognized for his expertise.

ACF 12Vac Tube Stereo Buffer

Or, go ahead with your current plan which is to hack up the FX and/or SainSmart and try to make them into a buffer by implementing only part of a real buffer circuit.

Good luck.

 

[ginetto61]

I just saw this suggested in another thread. It seems to be exactly what you're after in that it is actually a buffer, it can use 12BH7s and it runs off a 12v wall wart. The designer is widely recognized for his expertise.
ACF 12Vac Tube Stereo Buffer

Hi ! yes ... this is exactly what i am thinking. Thank you for the very useful link. And the reason to go for this kind of design is contained in the description very well

... many solid-state audio devices just sound too cold and brittle on their own. Adding a tube-based buffer can help humanize the sound, perhaps due to harmonic enrichment...

i have this exact feeling not only with music but also watching movies. The voices are more real, natural, human. I am quite intrigued by this.

Or, go ahead with your current plan which is to hack up the FX and/or SainSmart and try to make them into a buffer by implementing only part of a real buffer circuit.
Good luck.

i understand you deem this kit superior to what can be obtained from a FX audio o Sainsmart converted to buffer ?
The mod will cost me almost nothing. And they are already completed unit.
I have in mind the idea that a buffer is less critical than a preamp sound wise.
One thing is sure ... after this try i will get one of this kit.
I would be just curious to see a schematic of its power supply sextupler ?

The power supply is internal to the 12Vac ACF PCB and receives its power from an external transformer, usually a 12Vac wallwart. The 12Vac voltage runs through an elaborate sextupler circuit that develops both a high-voltage B+ and a DC heater voltage. The sextupler creates a raw DC voltage of about 94Vdc from a 12Vac wallwart.

for the isolation no problem. I am already using 12VDC wallwarts without ground (one from Apple and one that comes with sky tv decoder)
Thanks a lot again.

 

[vendetta]

tube01 schematic :

 

[batteryman]

I'm waiting for a ready built 12v AC powered buffer based on Musical Fidelity to arrive.


6J1 Valve Pre-amp Tube PreAmplifier Kit Assembled Board Audio Musical Fidelity | eBay


This is similar to the design listed in post no 73 I think.


MyOldVintageHifi: DIY - Tube Buffer (***Updated#2***)

 

[RumblePirate]

Hello guys, I have a serious issue from diy 6j1 preamp. First time I had no issues what so ever. Second time I assembled another board, I am getting heart beat like sounds from it, even with inputs disconnected. Using similar 12vac 3 amp power supply as before. Frequency of the beats is like 1/1-2 seconds, and it is consistently full volume beats. Haven't modified the board any way stop far. Both tubes are flowing and heating as well. Help will be appreciated

 

[batteryman]

It could be a form of 'motor boating' - a low frequency instability. Often due to feedback - try re routing the input and output wiring.


Motorboating; what is it, 'why?', and how to fix it? | Audiokarma Home Audio Stereo Discussion Forums

 

[ginetto61]

I'm waiting for a ready built 12v AC powered buffer based on Musical Fidelity to arrive ...

Hi ! may i ask you how did you select this one ? there are many to choose from and i am quite lost
As a start asa i will find the time i would like to try also the Tube-01 wired as buffer and listen. I really do not need Vgain ... just some nice tube tone

 

[batteryman]

I chose this module because I assumed that the seller was being honest in stating it was based on the Musical Fidelity tube buffer, and because I did not want to build one from scratch.


I also liked the idea of it being powered by 12v AC thus avoiding having to construct a high voltage supply.


It is not due to be delivered until the end of the month then I will be able comment further.