• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Single-ended 6N2 / 6P1 schematics advice needed

matose

matose

New Member
Hello all diy-ers,

I bought one diy tube amp from Ebay and I don’t really trust the chinese schematics they send me and I need a second opinion about it. It uses Chinese 6Z4 in parallel for rectifying AC to DC and 6N2 + 2 x 6P1 for the final stage. I will use Sylvania 6C4 NOS instead of 6Z4, Voskhod 6N2P NOS instead of Chinese 6N2 and Svetlana OTK 6P1P-EV NOS (EL82) instead of Chinese 6P1 - already ordered and on the way!

The resistors and transformers they sent in the package are fine for a first tube build, but the capacitors look fake and low quality (will order some from eBay after the final schematics). Will replace the potentiometer with japanese ALPS dual 100k and a bigger aluminum knob.

How can this schematics be modified for the best sound? I only want SE triode connection for the amp, so I’m not interested in other solutions. I prefer to stick to 6N2 and 6P1 regarding the tubes but I’m open to try other solution using better tubes that work at the same voltage (250v): EL84, EL86. I could really appreciate an answer from you if you have the time!

Output transformers (measured): primary (335-336 ohm), secondary1 (2-2.1 ohm), secondary2 (2.5-2.6 ohm)

Thanks a lot,
matose
 

Attachments

  • schema_tubeamp.jpg
    schema_tubeamp.jpg
    48.3 KB · Views: 113
  • tubeamp2.jpg
    tubeamp2.jpg
    138.7 KB · Views: 98
Register to hide this ad
This circuit does not seem to be "triode" connected. Main concern will be screen grid connected directly to power supply. It does not look right. I think original circuit calls for tetrode connection. I would use separate voltage regulator for screen grid and have voltage there BELOW plate (as it should be). If you still want to use TRIODE connection - connect screen grid to plate through resistor of few hundred ohms. But you will be able to get about 1 watt of audio power in that circuit.
 
So what will be your suggestion in that case? Speakers are JM Lab Laureate with 91dB sensitivity so 1W is pretty low :)
I don't want to invest in a new transformer to use the KT88, so what options do I have if I want 2-3W and triode connection? Maybe EL84 / 6P14P with plate running at ~270v?
 
If you suspect fake caps I would order from Mouser, Digikey or even Partconexion instead. They dont cost that much and you will be sure to get the real deal.
 
matose said:
So what will be your suggestion in that case? Speakers are JM Lab Laureate with 91dB sensitivity so 1W is pretty low :)
I don't want to invest in a new transformer to use the KT88, so what options do I have if I want 2-3W and triode connection? Maybe EL84 / 6P14P with plate running at ~270v?
Click to expand...

For 91 dB/W speakers you need at least 10-15 watts of power. Single ended is not going to happen. You may be able to get close to 10W is use KT90 in tetrode mode. If you want to use triodes, then 845, 211 or GM70 tubes is what you should look for, but with 1000 volts at plate they are not for a a novice DIY. With EL84 tubes - you may try to get about 8W in push-pull UL. But you will need new transformer anyway.

With what you have now - make headphone amp. Components and circuit are very appropriate for that (with small mods). But you will need to add choke in power supply.
 
Last edited:
After some more reading I will be building the RH EL84 v2 amp, you have the schematics attached. For starters I will use the JJ 12AT7 / ECC81 for pre and JJ EL84 for the finals.
The only thing different will be the rectifiers. I will be using two General Electric 6203 tubes in parallel for a maximum current of 140mA and a 4uF motor run cap (from the 6203 datasheet).
Please let me know if you have any comments, thanks!
 

Attachments

  • RH84 - rev2 CLC.png
    RH84 - rev2 CLC.png
    39.5 KB · Views: 53
  • RH84 - rev2.png
    RH84 - rev2.png
    168.9 KB · Views: 59
amp schematic looks solid, maybe use a 6ca4 for the rectifier and electrolytics caps for the filters, would probably only need one rectifier tube for single ended EL-84 amp.
 
matose said:
After some more reading I will be building the RH EL84 v2 amp, you have the schematics attached. For starters I will use the JJ 12AT7 / ECC81 for pre and JJ EL84 for the finals.
The only thing different will be the rectifiers. I will be using two General Electric 6203 tubes in parallel for a maximum current of 140mA and a 4uF motor run cap (from the 6203 datasheet).
Please let me know if you have any comments, thanks!
Click to expand...

This circuit will work. But my comment about 1W of power is still valid
 
You must log in or register to reply here.
Back
Top Bottom