Dear forum People,
I found your forum after a long internet search. I want information from you for free, this is very important. I thank each and every one of you.
I have a Axe FX 2 pre--amp. I want to use with a power amp in my Apartment. Almost all guitar Power amps has a lot of power. Then I found Chinese Hi-Fi Power amps. I'm using it and I'm Happy with it.
Except one thing. Since the amplifier is a hi-fi amplifier, it lowers the Gain. I'm sharing some pictures from inside the amplifier here. How do I release the preamp and Power amp tubes of this amp? I want to remove the gain resistor in the power amp and preamp. I plugged ecc83 into the preamp with a converter, the gain is stil low again. A double triode probably needs to be made.
I mean, it is reducing the gain. For example, hi-gain amps from Axe FX come to speaker like rock amp
The circuit elements inside the amplifier are not too many or complicated. If you describe to me which legs to lift and which connections to make, I can achieve this.
Best Regards,
Hail from Germany.
I found your forum after a long internet search. I want information from you for free, this is very important. I thank each and every one of you.
I have a Axe FX 2 pre--amp. I want to use with a power amp in my Apartment. Almost all guitar Power amps has a lot of power. Then I found Chinese Hi-Fi Power amps. I'm using it and I'm Happy with it.
Except one thing. Since the amplifier is a hi-fi amplifier, it lowers the Gain. I'm sharing some pictures from inside the amplifier here. How do I release the preamp and Power amp tubes of this amp? I want to remove the gain resistor in the power amp and preamp. I plugged ecc83 into the preamp with a converter, the gain is stil low again. A double triode probably needs to be made.
I mean, it is reducing the gain. For example, hi-gain amps from Axe FX come to speaker like rock amp
The circuit elements inside the amplifier are not too many or complicated. If you describe to me which legs to lift and which connections to make, I can achieve this.Best Regards,
Hail from Germany.
Last edited:
Tidbits I found, similar to these schermatics?
"6N9P, the Chinese equivalent of 6SL7" "SET" "stock 5U4 tube"
https://external-preview.redd.it/iG...bp&s=524dfaf359fcf30da4ce34678690a8e5bd98ba70
https://www.diyaudio.com/forums/att...2065d1446321547-douk-el34-amp-kit-dj040_-.jpg
"6N9P, the Chinese equivalent of 6SL7" "SET" "stock 5U4 tube"
https://external-preview.redd.it/iG...bp&s=524dfaf359fcf30da4ce34678690a8e5bd98ba70
https://www.diyaudio.com/forums/att...2065d1446321547-douk-el34-amp-kit-dj040_-.jpg
Thank you, i will try
Is Schematic necessary in this case? I never thought it would be like this.
If the amp you have even comes close to matching one of those schematics, there is no leg you can lift or connection you can make to get more gain. There is no gain resistor to lift. The circuit shows one output stage and one driver stage, no additional gain stages. Any guitar amp will have at least one extra gain stage and often several more than that.Dear forum People,
I found your forum after a long internet search. I want information from you for free, this is very important. I thank each and every one of you.
I have a Axe FX 2 pre--amp. I want to use with a power amp in my Apartment. Almost all guitar Power amps has a lot of power. Then I found Chinese Hi-Fi Power amps. I'm using it and I'm Happy with it.
Except one thing. Since the amplifier is a hi-fi amplifier, it lowers the Gain. I'm sharing some pictures from inside the amplifier here. How do I release the preamp and Power amp tubes of this amp? I want to remove the gain resistor in the power amp and preamp. I plugged ecc83 into the preamp with a converter, the gain is stil low again. A double triode probably needs to be made.
I mean, it is reducing the gain. For example, hi-gain amps from Axe FX come to speaker like rock amp
Best Regards,
Hail from Germany
Sinan.
I grabbed this line from the FX 2 user manual. The FX 2 itself has no gain so you are expecting to get all the gain between your guitar and speakers from two stages. Not going to happen.
"Designed for Unity Gain The Axe-Fx II uses digitally controlled potentiometers to operate as a unity-gain device irrespective of the input trim controls. Simply set the input trims with the LED input meters and you are done. Another benefit of this technique is that Amp and Drive blocks are unaffected by trim settings."
I can't tell how the driver tube is wired from the pictures, and I don't have the time and patience to reverse engineer an amp from a few pictures. The driver tube mentioned in this thread is the 6SL7 or Chinese equivalent. The schematics show either a 6SL7 or a 12AT7. Both are very similar dual triodes. These could simply be wired in parallel in your amp. It's hard to tell from the pictures. It may be possible to use them individually if they are indeed wired in parallel. In that case you would need to completely rewire the two driver tubes and add the additional parts to build another gain stage.
Both of those schematics show a 2K ohm feedback resistor that goes from the output transformer secondary to the input tube. It does reduce the gain somewhat while also reducing distortion. see if it is present in your amp. Lifting one end of that resistor might give you a little more gain, at least it's an easy experiment to try.
Both of those schematics show a 2K ohm feedback resistor that goes from the output transformer secondary to the input tube. It does reduce the gain somewhat while also reducing distortion. see if it is present in your amp. Lifting one end of that resistor might give you a little more gain, at least it's an easy experiment to try.
I will try those changes, thank you @JonSnell Electronic .
But maybe it is not correct, there is nothing like red-black-red-golden (2k)
But maybe it is not correct, there is nothing like red-black-red-golden (2k)
No, you want to take the resistor out of the circuit, not replace it with a wire.
I looked up the schematics so you could use them as a basis to determine what is in your amplifier. You should be able to print or draw output the schematic and then see where it is different from yours. You would use a ohm meter to determine connections and resistances. Doing it the first time will seem confusing but by the time you are finished it will not seem all that hard. As you go through the schematic, draw out the layout and mark the part values on it. As you go through it use a yellow (or whatever color you like) marker to highlight every wire or part you have checked (on the drawings, not the amp .
I looked up the schematics so you could use them as a basis to determine what is in your amplifier. You should be able to print or draw output the schematic and then see where it is different from yours. You would use a ohm meter to determine connections and resistances. Doing it the first time will seem confusing but by the time you are finished it will not seem all that hard. As you go through the schematic, draw out the layout and mark the part values on it. As you go through it use a yellow (or whatever color you like) marker to highlight every wire or part you have checked (on the drawings, not the amp
.Hey Kaelthas,
A quick look at the FX-2 manual tells me that it DOES have gain, as most multi-fx boxes do. It lists Boost and Gain functions, as well as what added gain you'd get from the amp modeling.
Have you tried those functions with your tube Hifi amp??
If that's still not enough gain for you, buy yourself an inexpensive boost pedal. Cheap and easy.
Plug it between your guitar and the FX-2. I've done this with small Hifi amps and it's easy to make my old Telecaster scream.
A quick look at the FX-2 manual tells me that it DOES have gain, as most multi-fx boxes do. It lists Boost and Gain functions, as well as what added gain you'd get from the amp modeling.
Have you tried those functions with your tube Hifi amp??
If that's still not enough gain for you, buy yourself an inexpensive boost pedal. Cheap and easy.
Plug it between your guitar and the FX-2. I've done this with small Hifi amps and it's easy to make my old Telecaster scream.
Sinan There was no problem with your amp. You are just using your fx2 wrong. Set it to output line signal. (Turn up master volume?) Maybe you have to do it for every preset its got?
Try to repair what you did to the amp except the input jacks if you prefer those instead of the original.
Are you using a guitar speaker on the amp? Then just go ahead and play turning up output level on processor and turn of speaker simulation. -Amp dont need more gain.
If you play through HiFi or monitor speakers, you have to engage cabinet simulation for each program number in fx's sound banks.
Cheers!
Try to repair what you did to the amp except the input jacks if you prefer those instead of the original.
Are you using a guitar speaker on the amp? Then just go ahead and play turning up output level on processor and turn of speaker simulation. -Amp dont need more gain.
If you play through HiFi or monitor speakers, you have to engage cabinet simulation for each program number in fx's sound banks.
Cheers!
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Thank you for Answers.
Don't hate me
I've noticed something. Axe fx changes Parameters itself, it reduced the gain .
I changed the battery inside the Axe Fx. There is no problem right now.
Now, I have some other Problems. The Tube power amp sounds dark. I will change volume Pot with 500k and will add 100uf bright cap.
Don't hate me
I've noticed something. Axe fx changes Parameters itself, it reduced the gain .
I changed the battery inside the Axe Fx. There is no problem right now.
Now, I have some other Problems. The Tube power amp sounds dark. I will change volume Pot with 500k and will add 100uf bright cap.
A few years ago I have bought (and modified) two amplifiers identical to this one. It is also called BL02 and it is still sold with with several brand names. The schematic is pretty basic: 6N9p voltage amplifier followed by EL34 power stage. The 6N9P section are connected in parallel. There is another popular low-cost amplifier similar to this one with the same tube complement but a different connection of the 6N9P. It is clearly geared towards internal Chinese market, TaoBao price is very low and this is the correct price range that should be paid for this entry-level amplifier. My suggestion to anyone thinking to modify it is to start by upgrading the electrical safety and bring it to minimum western standards.
1. Replace with a double insulated wire rated for mains voltage the red/black low-voltage speaker wire from the mains IDC connector to the power switch. It is the wire at the top Of the chassis on the first picture of this thread.
2. Check the wire connecting the ground terminal of the IDC mains connector to the chassis. It is factory connected to one of the tiny M3 screws that secure the plastic IDC connector body. This is a code violation, the wire must be connected to a transformer mounting bolt and secured with a double nut ot equivalent methods.
3. Check the mains fuse and replace it with a slow-blow 1A fuse with UL/CE safety markings. It was a unmarked 2A on my amplifiers.
4. UL/CE safety markings and voltage ratings are also missing from the cheap power switch. It would be advisable to replace it.
The power transformer is not compliant with the CE regulations, and it is rated for 220V instead of 230. It is rather small so it heats up greatly, but it seems to be up to the job anyway.
Then, the amplifier requires some changes to avoid a premature demise:
1. Add a insulated grommet on the chassis holes for the bundle of wires connecting the primary side of the output transformers. On both my amplifiers, and on the one at picture 1 of this tread, the neat looking heat shrink insulation has been removed to speed up the assembly so the sharp inox metal chassis is cutting trough the wire insulations on both transformers.
2. The first two electrolytic filter capacitors, the one directly connected at pin 2 of the rectifier tube and the following one after the 10 ohm 1W resistor, are exceeding the 5Z3P rectifier tube rating (100+100uF). They must be replaced with 33uF parts. The hum is coming from magnetic coupling between the 4H filter choke and the output transformer that sits directly above with the same orientation. They tried to mitigate this novice mistake by heawy capacitive filtering of the HT supply voltage before passing it to the choke, basically relegating this component to a decorative role. This will greatly decrease the life of the rectifier tube. If the humming from the right channel is unbearable after the capacitor replacement, the choke should be rotated (easier said than done on a inox chassis). On a standard low-efficiency bookshelf speaker the hum is tolerable.
Regarding the dark tone, this is expected due to the removal of the 2K feedback resistors. The amplifier does not reach full audio bandwidth even with feedback; without feedback the top and bottom end are further reduced. Try to rewire the EL34 as triode, but this will decrease the gain. The B+ on this amplifier is only 310V.
The resistor between control grid and ground at the input 6N9P is 470k and there is no coupling capacitor at the input. If you replace the original 100k volume potentiometer with a 500K guitar type potentiometer, you may remove the 470K resistor to increase the audio signal slightly. A coupling capacitor at the input may be useful to avoid damage to the 6N9P and the volume potentiometer if a DC voltage is applied at the input. A better idea would be to rewire this tube completely as 2 stages guitar type.
1. Replace with a double insulated wire rated for mains voltage the red/black low-voltage speaker wire from the mains IDC connector to the power switch. It is the wire at the top Of the chassis on the first picture of this thread.
2. Check the wire connecting the ground terminal of the IDC mains connector to the chassis. It is factory connected to one of the tiny M3 screws that secure the plastic IDC connector body. This is a code violation, the wire must be connected to a transformer mounting bolt and secured with a double nut ot equivalent methods.
3. Check the mains fuse and replace it with a slow-blow 1A fuse with UL/CE safety markings. It was a unmarked 2A on my amplifiers.
4. UL/CE safety markings and voltage ratings are also missing from the cheap power switch. It would be advisable to replace it.
The power transformer is not compliant with the CE regulations, and it is rated for 220V instead of 230. It is rather small so it heats up greatly, but it seems to be up to the job anyway.
Then, the amplifier requires some changes to avoid a premature demise:
1. Add a insulated grommet on the chassis holes for the bundle of wires connecting the primary side of the output transformers. On both my amplifiers, and on the one at picture 1 of this tread, the neat looking heat shrink insulation has been removed to speed up the assembly so the sharp inox metal chassis is cutting trough the wire insulations on both transformers.
2. The first two electrolytic filter capacitors, the one directly connected at pin 2 of the rectifier tube and the following one after the 10 ohm 1W resistor, are exceeding the 5Z3P rectifier tube rating (100+100uF). They must be replaced with 33uF parts. The hum is coming from magnetic coupling between the 4H filter choke and the output transformer that sits directly above with the same orientation. They tried to mitigate this novice mistake by heawy capacitive filtering of the HT supply voltage before passing it to the choke, basically relegating this component to a decorative role. This will greatly decrease the life of the rectifier tube. If the humming from the right channel is unbearable after the capacitor replacement, the choke should be rotated (easier said than done on a inox chassis). On a standard low-efficiency bookshelf speaker the hum is tolerable.
Regarding the dark tone, this is expected due to the removal of the 2K feedback resistors. The amplifier does not reach full audio bandwidth even with feedback; without feedback the top and bottom end are further reduced. Try to rewire the EL34 as triode, but this will decrease the gain. The B+ on this amplifier is only 310V.
The resistor between control grid and ground at the input 6N9P is 470k and there is no coupling capacitor at the input. If you replace the original 100k volume potentiometer with a 500K guitar type potentiometer, you may remove the 470K resistor to increase the audio signal slightly. A coupling capacitor at the input may be useful to avoid damage to the 6N9P and the volume potentiometer if a DC voltage is applied at the input. A better idea would be to rewire this tube completely as 2 stages guitar type.
Looking for EL 34 tubes for a Leben amplifier. Not ready to spend the dollars needed for NOS. Any suggestions on currently produced options for EL 34?Dear forum People,
I found your forum after a long internet search. I want information from you for free, this is very important. I thank each and every one of you.
I have a Axe FX 2 pre--amp. I want to use with a power amp in my Apartment. Almost all guitar Power amps has a lot of power. Then I found Chinese Hi-Fi Power amps. I'm using it and I'm Happy with it.
Except one thing. Since the amplifier is a hi-fi amplifier, it lowers the Gain. I'm sharing some pictures from inside the amplifier here. How do I release the preamp and Power amp tubes of this amp? I want to remove the gain resistor in the power amp and preamp. I plugged ecc83 into the preamp with a converter, the gain is stil low again. A double triode probably needs to be made.
View attachment 1283922 View attachment 1283923 View attachment 1283924 View attachment 1283925 View attachment 1283926 View attachment 1283927 View attachment 1283928
I mean, it is reducing the gain. For example, hi-gain amps from Axe FX come to speaker like rock amp
Best Regards,
Hail from Germany.