Help with tube amp

[Jarryd]

I just purchased a Chinese preamp from aliexpress, can someone tell me the tube equivalent I can upgrade too. Here's the product name

JBH 6j4 ( EF94 ) 6p6p ( 6v6 ) Tube Pre-amplifier HIFI EXQUIS best sound high density bass preamp finished product

 

[Lingwendil]

EF94 and 6V6GT/6V6/6V6G will work. Not much more we can do without the schematic though.

 

[JonSnell Electronic]

The title on the aliexpress suggests the equivalents;
"This tube pre-amp use some very welknow tubes:
Chinese 6j4 can be replace directly by europ EF94 tube or US 6AU6
Chinese 6p6p can be replce directly by 6v6"
Not sure I would trust them as the spelling is not that good ...
Good luck.

 

[Jarryd]

I ordered it shall post the schematic here after delivery. @lingwendil can you post a source for these tubes?

 

[kodabmx]

I'd use Soviet 6P6S in place of the Chinese 6P6P.

 

[Jarryd]

this is the schematic. can you guys help me with some optimum choices

 

[Jarryd]

6V6GTMP-SOV Tube, Beam Power Amplifier, Matched Pair, Sovtek
6X5WGT Tube, mil version 6x5gt Full Wave High Vacuum Rectifier

6AU6 Tube, 6AU6 /6AU6WC, Sharp-Cutoff RF Pentode USA branded - planning to get a pair. will they be matched?

 

[kodabmx]

6P6S = 6V6 = 6AY5 = 587 tube. Tetrode. Reflector plant ― Hi-End vacuum tubes, sockets, capacitors, nixie. Retail and wholesale to worldwide.
6C5S / 6X5GT / EZ35 tube - RECTIFIER tubes - Tubes-Store.com
6J4P / EF94 / 6AU6 tube - OTHER tubes - Tubes-Store.com


All good choices.

 

[Jarryd]

Do I need to match the 6j4's? Or just go ahead and order a ransom pair

 

[kodabmx]

It won't hurt, but won't make much of a difference, either.

 

[Jarryd]

What are the parts that I could change part for the tubes for better SQ?

 

[fringy75]

Adding a headphone output

Hi.


I have the same chinese pre-amp and to be honest it works pretty well for the price.


I would like to ask the experts here if it is possible to add an output for headphones which are 30 ohm.


Thank you 🙂

 

[rayma]

That circuit would need a buffer to drive 30R loads. Your power amp would be a better driver.

 

[fringy75]

That circuit would need a buffer to drive 30R loads. Your power amp would be a better driver.

Thank you for the quick reply. Unfortunately, this drives an active speaker setup, so I will be best to add a headphone amp to the chain 🙂

 

[nimo]

Found another thread here, looks like the same preamp...
6j4+6p6 hifi preamplifier kit!

Anyway, based on the schematics 2 post up, can someone help me identify the feedback resistor? I only see a single 24k...assume that is the one? Current gain level means my volume knob at 7 o'clock is pretty loud. 9 o'clock will make ears bleed.

Could anyone help with advice on what would be the ideal feedback resistor value so i get the most volume fine tuning without messing up the sound?