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Chinese 6N2 / 6P1 schematics advice needed

matose

Member
2016-05-04 4:37 pm
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
 

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artosalo

Member
2010-02-16 9:00 am
How can this schematics be modified for the best sound?

The person who can do that has invented something unprecedented.
Unfortunately "good sound" varies a lot between different listener, days, mood etc,.

The schematic looks OK. That circuit is a basic pentode connected SE-amplifier.
In power supply is one mistake. The first capacitor after the rectifier may not be 220 uF. This big capacitor will ruin the rectifier very quickly.
Usually first cap is from 22 to 47 uF.
 

matose

Member
2016-05-04 4:37 pm
Thanks a lot for the feedback guys
Hmm... what should I do to convert it to triode mode?
Also, I see that EL86 runs at the same voltage and have better specs and power. Should I search eBay for these. It will make a difference or will the 6P1P-EV will be enough?

Other tweaks of tips I should be aware before I start building. I have experience in electronics but very little in tubes, that's why I ask the specialists here.
 
Remember that these aren't "designer's designs" if you get what I mean, but product of a bunch of Chinese entrepreneurs who get together and think : "what can we make to sell to American customers and make some money?" so they typically read some Forum to know what may sell ;) , google some schematic, order the parts from their low cost suppliers and offer the kit (or finished product) on EBay .

Don't expect much from such products.

Besides , you paid ..... how much? :rolleyes:

They can't even write English !!!!!! :rolleyes:

I bet if you quote them what artosalo wrote
In power supply is one mistake. The first capacitor after the rectifier may not be 220 uF. This big capacitor will ruin the rectifier very quickly.
Usually first cap is from 22 to 47 uF.
they'll look at you glassy eyed and answer: ".... huh? " :D
 

pcan

Member
Paid Member
2015-12-31 4:57 pm
6C4 is a triode, it is not a substitute for the 6Z4 rectifier. According to the 6Z4 datasheet, the maximum value of first capacitor is 8uF, so there is definitely a error in the power supply schematic. I guess that both filter capacitors should be 22uF. 220uF is typical for silicon rectifiers.
 

pcan

Member
Paid Member
2015-12-31 4:57 pm
Let's say they sent two capacitors with 220uF stamped outside. The real capacity should be measured. I also buy bargain electronic parts from China and not everything is what it looks to be, big capacitors are one of the most suspect parts (I don't buy them from China anymore). But I guess it's a mistake. Most 6N2/6P1 kits have silicon rectifier with 220uF capacitors. A untrained seller may have just put in the bag the usual part.
 

matose

Member
2016-05-04 4:37 pm
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!
 

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