Chinese board 6L6 KT88 is it worth???

[giorgos]

Tube SE 6L6 EL34 KT88 Amplifier Stereo PCB | eBay

I was looking to this chinese boards for tube amplifiers.
As i posted before im new to amplifiers and want to make something simple for starting.Thinking for KT88 for final to get more watts.

Will be this good according to the schematic?or i will throw to the bucket my money.Please remember that i want something good to sound but without toooooo much money,tubes,weight etc.
something to build for the start.
i prefer to give money for good OT.

Thanks
George

 

[DF96]

It is a simple SET circuit, which might be better built using point-point wiring. Don't expect amazing sound. The PCB makes no provision for adding grid stoppers, which are sometimes necessary.

 

[giorgos]

so,because the simplicity of the circuit you are telling me not to use board.

 

[rmyauck]

This site would be well worth looking at. He has a forum in this site with lots of support, and his PCB's are well liked and have so been popular over the last several years because of the sonics also.

Tubelab | Dedicated to advancing the state of the art in affordable high end audio.

 

[DanHat]

Two things you might consider.


DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier


Tubelab SSE | Tubelab


I have built the Tubelab simple SE and it is an excellent amp.

 

[azazello]

There isn't possibility use chock to decrease hmmm. /You can cut track between two el. caps after rectifier and connect chock/.

 

[rmyauck]

If you want to do P2P others to consider which I think are favored sonically over Michael's just posted above. Kegger has a few different variations for different driver tubes if you search SEUL amps with google.

Another KT88 SE-UL build - AudioKarma.org Home Audio Stereo Discussion Forums

KT88, (ect) Single ended amp, SEUL - Page 3 - AudioKarma.org Home Audio Stereo Discussion Forums

 

[sreten]

Hi,

Forget those boards.

8 W Singe End, EL34 amplifier designed by Claus Byrith, Royal Academy of Music in Aarhus, Denmark. | Lundahl Transformers

For my money the best designed and documented budget SE amplifier out there.

You need a similar tapped output transformer for a genuine 8W of SE output.

rgds, sreten.

 

[jazbo8]

so,because the simplicity of the circuit you are telling me not to use board.

The price also seems high for what you get, please consider supporting regular forum contributors like those mentioned above, why give money to the Chinese factories?😉

 

[costis_n]

This kind of circuit has very few parts. Use something like this

And you can easy try other capacitors etc etc

 

[soundbrigade]

There hasn't happened much in here, but I hope I will stir things up a little. As there's a thread about PCBs for 6L6, EL34, KT88, KT120 ..., I prefer filing my own suggestions and concerns in this thread.

Recently, I purchased this bare PCB from China. It's a sturdy double-sided PCB with goldplated solder pads. It steams quality really.
The design is for a SE-amp using any power pentode/beam-tetrode like 6L6 ... KT120, 807, GU50 ... you name it. Driver is a 6SL7 SRPP/mu-follower OR a 6SN7.
Even as there's a pretty nice schematic and a BOM I run into a few road bumps, that I haven't managed to clear out with the supplier.
One issue is a discrepancy between the schematic for the PSU and what's actually laid out on the PCB and another are some small changes obviously made here and there and that not all components on the PCB are marked with a designator.
One general question - it is suggested that I use a 270 Ohm 50W cathode resistor for a 6L6 (SE) @ 100mA (or propably less). But a 5,5W resistor ought to be enough.
Guess I will have to send another message to the supplier asking for a new and updated schematics. Of course I will get a (good) result following the markings on the PCB, but it will be difficult to make modifications.

The main idea was to fix something "simple" to be able to "listen through" a number of 6L6-like tubes from Russia and China I've got and when finished with that, use the board for either a pair of GU50 or 807.

So simply, has anyone tried this PCB and has any advice. Whenever I get answers from China or has made some progress myslef, I'll be back.

 

[jazbo8]

270 Ohm 50W cathode resistor for a 6L6 (SE) @ 100mA (or propably less). But a 5,5W resistor ought to be enough.

It might just be a typo, 50W?! Where would that even fit in the chassis? If you did the math yourself, you already know the answer...

 

[soundbrigade]

I did the mat (or at least had a sneak view at the answers) and knew that 5W was enough.
On the other hand, the KT88 would require a 25W resistor... 🙄

Let's se if I have a copy of the board somewhere. Oh, am I stupid or just dumb?? There's pic of the PCB on the sellers eBay-site. The two big square holes (there are four actually) were meant for the BIG resistors, the other for cathode caps.

 

[DF96]

It steams quality really.

Some Chinese suppliers are good at "steaming quality" but, as you found, not so good at delivering quality. Why do you want gold-plated solder pads?

 

[soundbrigade]

This WAS of good quality, but the supplier had made modifications that didn't show up on the schematics, thus causing confusion.

Why I choose a gold-plated PCB?! Well, it looked smart in that black color, else any metal will work and I was prepared to pay the xtra Euros for the color.

 

[wdecho]

Two things you might consider.


DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier


Tubelab SSE | Tubelab


I have built the Tubelab simple SE and it is an excellent amp.

I second this motion. The circuit is so simple with such few parts why spend money on a board. My first SET was a simple spud amp but either one of these is just one more tube per channel and I am sure they will sound much better. Many builds have been done with Tubelab boards with tons of support and information on this forum.

 

[cl1238]

There hasn't happened much in here, but I hope I will stir things up a little. As there's a thread about PCBs for 6L6, EL34, KT88, KT120 ..., I prefer filing my own suggestions and concerns in this thread.

Recently, I purchased this bare PCB from China. It's a sturdy double-sided PCB with goldplated solder pads. It steams quality really.
The design is for a SE-amp using any power pentode/beam-tetrode like 6L6 ... KT120, 807, GU50 ... you name it. Driver is a 6SL7 SRPP/mu-follower OR a 6SN7.
Even as there's a pretty nice schematic and a BOM I run into a few road bumps, that I haven't managed to clear out with the supplier.
One issue is a discrepancy between the schematic for the PSU and what's actually laid out on the PCB and another are some small changes obviously made here and there and that not all components on the PCB are marked with a designator.
One general question - it is suggested that I use a 270 Ohm 50W cathode resistor for a 6L6 (SE) @ 100mA (or propably less). But a 5,5W resistor ought to be enough.
Guess I will have to send another message to the supplier asking for a new and updated schematics. Of course I will get a (good) result following the markings on the PCB, but it will be difficult to make modifications.

The main idea was to fix something "simple" to be able to "listen through" a number of 6L6-like tubes from Russia and China I've got and when finished with that, use the board for either a pair of GU50 or 807.

So simply, has anyone tried this PCB and has any advice. Whenever I get answers from China or has made some progress myslef, I'll be back.

Hi, I bought the same pcb from same supplier. Not sure if you get the same schematic, mine shown 150 ohm 25w, but base on calculation, a 5w is more than enough. Also there are 2 track missing, where the vendor said only connect necessary. Some sp also in reverse between the 2 channel

 

[soundbrigade]

Thanks for input!

Got this answer a few days ago, asking about modifications för 6L6:

was only revise a litter.R29 2.2UF/400V caps not connect,if connect will addion current.i was test the board.R27 change to 82k R30 change TO 22k c13 change 1UF/630V R25 change to 10k.other no problem.

The black PCB makes it difficult to trace the tracks if necessary.

 

[cl1238]

Hi, SB
My PCB did not have label & I trace it & label it myself. Please note C17 one side on PCB has no connection which should be Gnd. Connection between +ve C15 & R27/R30 is missing on PCB.
Numbering (on PCB) of sp5 & sp6 (2 & 3) are in reverse compare with the schematic.
Pin 2 of V4 has no connection to Pin1 of SP5.

I'm still waiting some 2W/3W resistors before I can finish, so still have not test the amp. I'll be using EL34B hence I change the output tube cathode R to 330, if the result is not satisfy, I'll use 220.

Please confirm if you are receiving the same schematic.
Thanks

 

[soundbrigade]

Thanks for your info. Will look into this ASAP. I still have to order components I didn't find in my drawers.

Btww, the SP? is a kind of switch or what? That was something that could be clarified in the BOM.

PeDIYtube has developed some various tube amps with PCBs and I got the board for the Clementine. There are also good info how to use it för 6L6. Had an idea of using that PCB, but it's always a mess order stuff from USA (delivery time, postage costs, delivery time ...).
Clementine