I bought this nice china made amp
It sounds nice and has some power, I believe this is the make and mode / info
REISONG Boyuu A9 EL34 single-ended pure class A tube amplifier EL34Bx2 6N9Px2 5Z3PJx1 D version
I’d like to know what tubes a can roll in it, does it self bias or do I have to do that and if so, how. Here’s some more specs
Specifications:
Output Power: 12W * 2 (ultra-linear connection).
Frequency Response: 20Hz - 28KHz.
Output impedance: 4ohm, 8ohm
Total Harmonic Distortion: ≤ 1% (1kHz).
Input Sensitivity: 750MV.
Input impedance: 100KΩ (two input signals)
Dimensions (W × D × H): 310 × 220 × 160mm.
SNR: 88dB.
voltage amplification tube: 6N9PJ × 2.
power output tube: Shuguang EL34B × 2.
rectifier tube: 5Z3PJ × 1.
Power Transformers: new imported 0.35, stacked thick 60MM (96-60).
Output transformer core: 0.35 new imported audio-specific piece
Output Block: high-end export-oriented base
Power Supply Voltage: AC 100V - 240V / 50Hz-60Hz (100V, 110V, 120V, 230V, 240V version will take 2-7 work days to order), 220V version is in stock.
Package includes: Amplifierx1PC, Power Cordx1PC
A9 technology
Power transformer: The same imported 0.35 iron core, the same neat and beautiful, the same multiple composite vacuum dipping paint.
Chassis: The same sinking design, the same surface without a screw, the same perfect.
Output transformer: high with plate
Power line: Double high voltage full wave tube rectifier 315V+315V, imported iron core for power inductor, dispatch type power supply filter, imported Phillips/ruby power filter.
Amplified line: It adopts the Japanese SUN classic line improvement. Each channel adopts two three-stage tube parallel common-acoustic amplification, featuring high output voltage and large driving current. The sound is full and fast, and the high-pitched sound is smooth and smooth.
A9 materials
Power transformer: using 96-60 large power core design power of 200W, high flux thick silicon steel imported 0.35. Oxygen-free copper enameled wire using domestic manufacturers layered tightly wound, with very low load current characteristic, no vibration, no buzz.
Output transformer: divided into segments of tightly wound, using the Japanese ultra-thin electrically insulating paper of pure wood (thickness of only 0.06MM, withstand voltage 2000V).
Capacitance: Imported hifi capacitors do filtering (Netherlands, Philips, Japan ELNA, Japan Ruby, etc.). Coupling using the Netherlands Philips tonic special grade audio capacitors, transparent sound elegant.
D version:
Power transformer 96-60.
Audio dedicated output transformer (76-40)
Shuguang export type EL34B tube A class output.
The new 6N9PJ is amplified in parallel and the force is twice that of the normal line.
Manual welding.
View attachment 1
View attachment 1
View attachment 1
It sounds nice and has some power, I believe this is the make and mode / info
REISONG Boyuu A9 EL34 single-ended pure class A tube amplifier EL34Bx2 6N9Px2 5Z3PJx1 D version
I’d like to know what tubes a can roll in it, does it self bias or do I have to do that and if so, how. Here’s some more specs
Specifications:
Output Power: 12W * 2 (ultra-linear connection).
Frequency Response: 20Hz - 28KHz.
Output impedance: 4ohm, 8ohm
Total Harmonic Distortion: ≤ 1% (1kHz).
Input Sensitivity: 750MV.
Input impedance: 100KΩ (two input signals)
Dimensions (W × D × H): 310 × 220 × 160mm.
SNR: 88dB.
voltage amplification tube: 6N9PJ × 2.
power output tube: Shuguang EL34B × 2.
rectifier tube: 5Z3PJ × 1.
Power Transformers: new imported 0.35, stacked thick 60MM (96-60).
Output transformer core: 0.35 new imported audio-specific piece
Output Block: high-end export-oriented base
Power Supply Voltage: AC 100V - 240V / 50Hz-60Hz (100V, 110V, 120V, 230V, 240V version will take 2-7 work days to order), 220V version is in stock.
Package includes: Amplifierx1PC, Power Cordx1PC
A9 technology
Power transformer: The same imported 0.35 iron core, the same neat and beautiful, the same multiple composite vacuum dipping paint.
Chassis: The same sinking design, the same surface without a screw, the same perfect.
Output transformer: high with plate
Power line: Double high voltage full wave tube rectifier 315V+315V, imported iron core for power inductor, dispatch type power supply filter, imported Phillips/ruby power filter.
Amplified line: It adopts the Japanese SUN classic line improvement. Each channel adopts two three-stage tube parallel common-acoustic amplification, featuring high output voltage and large driving current. The sound is full and fast, and the high-pitched sound is smooth and smooth.
A9 materials
Power transformer: using 96-60 large power core design power of 200W, high flux thick silicon steel imported 0.35. Oxygen-free copper enameled wire using domestic manufacturers layered tightly wound, with very low load current characteristic, no vibration, no buzz.
Output transformer: divided into segments of tightly wound, using the Japanese ultra-thin electrically insulating paper of pure wood (thickness of only 0.06MM, withstand voltage 2000V).
Capacitance: Imported hifi capacitors do filtering (Netherlands, Philips, Japan ELNA, Japan Ruby, etc.). Coupling using the Netherlands Philips tonic special grade audio capacitors, transparent sound elegant.
D version:
Power transformer 96-60.
Audio dedicated output transformer (76-40)
Shuguang export type EL34B tube A class output.
The new 6N9PJ is amplified in parallel and the force is twice that of the normal line.
Manual welding.
View attachment 1
View attachment 1
View attachment 1
Are you able to make some basic measurements (using DMM, oscilloscope, spectrum analyzer, etc.)?
You would then be able to make objective measurements and share these with us for serious comments. Of course you can try to rely on your ears only, but I’m sure proper measurement can improve your system even further. It’s hard to comment on your personal hearing
.
Regards, Gerrit
You would then be able to make objective measurements and share these with us for serious comments. Of course you can try to rely on your ears only, but I’m sure proper measurement can improve your system even further. It’s hard to comment on your personal hearing
.Regards, Gerrit
The amp is self biasing. I would not plug anything other than EL34s into it. From examining the photos available online of what the inside looks like, it's ultra-linear single ended with no feedback. That would make for poor damping and high distortion. Tube rolling won't fix that. Triode strapping the output tubes would likely help ameliorate these issues.
Are you able to make some basic measurements (using DMM, oscilloscope, spectrum analyzer, etc.)?
You would then be able to make objective measurements and share these with us for serious comments. Of course you can try to rely on your ears only, but I’m sure proper measurement can improve your system even further. It’s hard to comment on your personal hearing
Regards, Gerrit
I do have a scope, and meters and a umk mic. Just need some guidance of how to do some measurements with a scope and so on
All the info you seek is in the other thread you posted in. Maybe spend a few minutes and look thru it.
jeff
@carlthess40 :
You have a choice here : use it ( and replace with similar tubes when the supplied
burns out) - or spend a lot of money on other look-alike tubes and in the end junk
your amp in the dustbin.
You have a choice here : use it ( and replace with similar tubes when the supplied
burns out) - or spend a lot of money on other look-alike tubes and in the end junk
your amp in the dustbin.
EL34
It may give you some insight what you want to achieve rolling with different brand EL34.
This shop inform some EL34 characteristics and sound quality on the guitar amp pov.
Vacuum Tube - EL34B, Valve Art
SKU: T-EL34B-VA Item ID: 004851 Starting at: $13.15
Octal power tube (Max Plate Watts = 25W) EL34B(with shadow grid) is a high performance improved version of pentode EL34A to solve the problem of overheated No. 2 Grid. Maximum anode dissipation is 25W and output power of single tube is over 10W in A1 amplification mode. When used in AB1 mode, two tubes can output over 35W. It can substitute 6CA7.
== == = = = =
Vacuum Tube - E34L, JJ Electronics
SKU: T-E34L-JJ Item ID: 004827 Starting at: $13.95
The JJ Electronic E34L adds more power to a standard EL34 due to its higher grid voltage rating. This increase gives the tube more headroom and a tighter response on the low end. The wide frequency response of this tube offers excellent harmonics that work in a variety of genres ranging from the cleanest cleans to rich and aggressive breakup.
== === = = = = =
EL34, JJ Electronics
SKU: T-EL34-JJ Item ID: 004841 Starting at: $13.95
The JJ Electronic EL34 is another classic from JJ. This tube features a rugged construction leading to an incredibly reliable EL34 with astonishing tone. Overall the sound is nicely balanced with tight lows, a rich and dynamic mid range and clear highs. The JJ EL34 is a great replacement for guitar amplifiers and stereo amps as well.
=== = === = = =
EL34 II, JJ Electronics, Pentode
SKU: T-EL34II-JJ Item ID: 039636 Starting at: $16.00
The JJ Electronic EL34 II is a different construction of the classic EL34 tube that offers a different tonal palette than the original. This tube has a more compact plate structure than standard EL34. The JJ EL34 II has an increased low to low-mid end with plenty of headroom to spare. This tube has a thick and tight bass response. The mids are balanced and harmonically rich with pleasantly smooth highs. The JJ EL34 II is stronger than the original but not harsh sounding in any way. When overdriven, this tube has a warm and dynamic distortion that rivals many vintage tubes.
=== = = = = ===
Vacuum Tube - 6CA7, JJ Electronics
SKU: T-6CA7-JJ Item ID: 004661 Starting at: $16.45
The JJ Electronic 6CA7 is a true to form reproduction of a classic tube that will work in most EL34 amps. The 6CA7 is often considered the American cousin to the British EL34. Sonically, this tube is closer to a 6L6 than an EL34 but without the sometimes harsh high end of the 6L6. The JJ 6CA7 offers warm highs with punchy articulate mids and tight lows. Wielding even more power than a KT77, this tube is a great choice for people looking for a change in their EL34 amp’s tone or want to push their levels that much further.
= == = = = ==== =
EL34 Electro-Harmonix
SKU: T-EL34-EH Item ID: 004840 Starting at: $17.95
Most common power pentode found in British amplifiers such as Marshall, Hiwatt, Laney, and Sound City. The EL34EH defines the classic British rock sound of the 1960s and 1970s.
== ==== = = = == =
E34L JJ Electronics, Blue Glass
SKU: T-E34L-BL-JJ Item ID: 004828 Starting at: $18.95
The JJ Electronic E34L adds more power to a standard EL34 due to its higher grid voltage rating. This increase gives the tube more headroom and a tighter response on the low end. The wide frequency response of this tube offers excellent harmonics that work in a variety of genres ranging from the cleanest cleans to rich and aggressive breakup (guitar).
== = = = = ====
Vacuum Tube - 6CA7, Electro-Harmonix Big Bottle
SKU: T-6CA7-EH Item ID: 004660
List Price: $25.25 Starting at: $19.95
Electro-Harmonix 6CA7 Vacuum Tube Big bottle beam-tetrode version of EL34. Perfect EL34 replacement for Musicman amplifiers.
= == = = = = ====
Vacuum Tube - KT77, JJ Electronics
SKU: T-KT77-JJ Item ID: 004874 Starting at: $19.95
IThe JJ Electronic KT77 is a reproduction of the original tubes that captures the sound that made the KT77 famous. In their typical fashion, JJ has built this tube in a solid construction that is robust and highly reliable. This tube has more headroom than a typical EL34. The low end is fat and defines with detailed and responsive mids and smooth highs. This is an excellent tube for adding more power to the sound of an EL34 amp.
== = = = = ====
EL34B TAD Tube Amp Doctor
SKU: T-EL34B-TAD-X Item ID: 004849 Starting at: $21.25
Octal power tube (Max Plate Watts = 25W)
Sensational new high-gain EL34 tube with a very dynamic tone. An authentic remake of the British Mullard EL34. The clear and harmonic open top end allows for great clean tone and at the same time the TAD EL34B-STR offers incredibly powerful mids and equally powerful bass. The golden control grid and especially large cooling grids guarantee maximum stability and reliability. Consequently, this EL34 provides a maximum of gain and dynamic response.
= == = = = ====
EL34B, Tung-Sol Reissue
SKU: T-EL34B-TUNG Item ID: 004850 Starting at: $24.70
Higher impedance design with increased touch responsiveness and a unique clipping characteristic with a hint of the 6L6 sound. Made in Saratov, Russia.
=== = = = = = =
EL34 Groove Tubes Matched Pair
SKU: T-EL34M-MP-GT Item ID: 004852 Price: $47.00
Octal power tube (Max Plate Watts = 25W) The GT EL34 is based on the original Mullard® EL34 of the '60s - the stock tube in all early Marshall® and Hiwatt® amps. Mullard produced it for about 15 years, and this is a faithful reproduction of the classic XF2 dual-getter version. It has a big, fat and well-defined tone and really “wakes up" reissue amps to perform like the originals. As close as you can get to vintage Marshall® power tube heaven.
==== = = = = =
E34L Groove Tubes Matched Pair
SKU: T-E34L-S-MP-GT Item ID: 004829 Price: $55.00
Octal power tube (Max Plate Watts = 25W) EXCLUSIVE GT design. The heat wings attached to the plate give this version of the original EL34 15 - 20 percent more power. Interchanges in any EL34 application and stays tight and robust all the way up to full power. Highly dynamic, big low end and runs cooler for longer life. Amazing headroom, killer tone and all of the great features and characteristics of the EL34 design.
== = == === = ==
Vacuum Tube - 6CA7 / EL34, Mullard, Pentode
SKU: T-6CA7_EL34-M Item ID: 007479 Price: $179.90
The 6CA7 is a power pentode of the glass octal type. This tube is suitable for all applications which require peak powers of up to 11 watts from a single tube or up to 100 watts from two tubes in the normal push-pull arrangement. It is equally suitable for domestic amplifiers and public address equipment.
=== === = ==
EL34 Mullard Reissue
SKU: T-EL34-MUL Item ID: 004843 Starting at: $23.25
Copy of the XF2 Mullard EL34 of the 60s. The perfect power tube for the Dynaco ST-70 or vintage Marshall amplifiers. the best current production EL34 available Made in Saratov, Russia.
It may give you some insight what you want to achieve rolling with different brand EL34.
This shop inform some EL34 characteristics and sound quality on the guitar amp pov.
Vacuum Tube - EL34B, Valve Art
SKU: T-EL34B-VA Item ID: 004851 Starting at: $13.15
Octal power tube (Max Plate Watts = 25W) EL34B(with shadow grid) is a high performance improved version of pentode EL34A to solve the problem of overheated No. 2 Grid. Maximum anode dissipation is 25W and output power of single tube is over 10W in A1 amplification mode. When used in AB1 mode, two tubes can output over 35W. It can substitute 6CA7.
== == = = = =
Vacuum Tube - E34L, JJ Electronics
SKU: T-E34L-JJ Item ID: 004827 Starting at: $13.95
The JJ Electronic E34L adds more power to a standard EL34 due to its higher grid voltage rating. This increase gives the tube more headroom and a tighter response on the low end. The wide frequency response of this tube offers excellent harmonics that work in a variety of genres ranging from the cleanest cleans to rich and aggressive breakup.
== === = = = = =
EL34, JJ Electronics
SKU: T-EL34-JJ Item ID: 004841 Starting at: $13.95
The JJ Electronic EL34 is another classic from JJ. This tube features a rugged construction leading to an incredibly reliable EL34 with astonishing tone. Overall the sound is nicely balanced with tight lows, a rich and dynamic mid range and clear highs. The JJ EL34 is a great replacement for guitar amplifiers and stereo amps as well.
=== = === = = =
EL34 II, JJ Electronics, Pentode
SKU: T-EL34II-JJ Item ID: 039636 Starting at: $16.00
The JJ Electronic EL34 II is a different construction of the classic EL34 tube that offers a different tonal palette than the original. This tube has a more compact plate structure than standard EL34. The JJ EL34 II has an increased low to low-mid end with plenty of headroom to spare. This tube has a thick and tight bass response. The mids are balanced and harmonically rich with pleasantly smooth highs. The JJ EL34 II is stronger than the original but not harsh sounding in any way. When overdriven, this tube has a warm and dynamic distortion that rivals many vintage tubes.
=== = = = = ===
Vacuum Tube - 6CA7, JJ Electronics
SKU: T-6CA7-JJ Item ID: 004661 Starting at: $16.45
The JJ Electronic 6CA7 is a true to form reproduction of a classic tube that will work in most EL34 amps. The 6CA7 is often considered the American cousin to the British EL34. Sonically, this tube is closer to a 6L6 than an EL34 but without the sometimes harsh high end of the 6L6. The JJ 6CA7 offers warm highs with punchy articulate mids and tight lows. Wielding even more power than a KT77, this tube is a great choice for people looking for a change in their EL34 amp’s tone or want to push their levels that much further.
= == = = = ==== =
EL34 Electro-Harmonix
SKU: T-EL34-EH Item ID: 004840 Starting at: $17.95
Most common power pentode found in British amplifiers such as Marshall, Hiwatt, Laney, and Sound City. The EL34EH defines the classic British rock sound of the 1960s and 1970s.
== ==== = = = == =
E34L JJ Electronics, Blue Glass
SKU: T-E34L-BL-JJ Item ID: 004828 Starting at: $18.95
The JJ Electronic E34L adds more power to a standard EL34 due to its higher grid voltage rating. This increase gives the tube more headroom and a tighter response on the low end. The wide frequency response of this tube offers excellent harmonics that work in a variety of genres ranging from the cleanest cleans to rich and aggressive breakup (guitar).
== = = = = ====
Vacuum Tube - 6CA7, Electro-Harmonix Big Bottle
SKU: T-6CA7-EH Item ID: 004660
List Price: $25.25 Starting at: $19.95
Electro-Harmonix 6CA7 Vacuum Tube Big bottle beam-tetrode version of EL34. Perfect EL34 replacement for Musicman amplifiers.
= == = = = = ====
Vacuum Tube - KT77, JJ Electronics
SKU: T-KT77-JJ Item ID: 004874 Starting at: $19.95
IThe JJ Electronic KT77 is a reproduction of the original tubes that captures the sound that made the KT77 famous. In their typical fashion, JJ has built this tube in a solid construction that is robust and highly reliable. This tube has more headroom than a typical EL34. The low end is fat and defines with detailed and responsive mids and smooth highs. This is an excellent tube for adding more power to the sound of an EL34 amp.
== = = = = ====
EL34B TAD Tube Amp Doctor
SKU: T-EL34B-TAD-X Item ID: 004849 Starting at: $21.25
Octal power tube (Max Plate Watts = 25W)
Sensational new high-gain EL34 tube with a very dynamic tone. An authentic remake of the British Mullard EL34. The clear and harmonic open top end allows for great clean tone and at the same time the TAD EL34B-STR offers incredibly powerful mids and equally powerful bass. The golden control grid and especially large cooling grids guarantee maximum stability and reliability. Consequently, this EL34 provides a maximum of gain and dynamic response.
= == = = = ====
EL34B, Tung-Sol Reissue
SKU: T-EL34B-TUNG Item ID: 004850 Starting at: $24.70
Higher impedance design with increased touch responsiveness and a unique clipping characteristic with a hint of the 6L6 sound. Made in Saratov, Russia.
=== = = = = = =
EL34 Groove Tubes Matched Pair
SKU: T-EL34M-MP-GT Item ID: 004852 Price: $47.00
Octal power tube (Max Plate Watts = 25W) The GT EL34 is based on the original Mullard® EL34 of the '60s - the stock tube in all early Marshall® and Hiwatt® amps. Mullard produced it for about 15 years, and this is a faithful reproduction of the classic XF2 dual-getter version. It has a big, fat and well-defined tone and really “wakes up" reissue amps to perform like the originals. As close as you can get to vintage Marshall® power tube heaven.
==== = = = = =
E34L Groove Tubes Matched Pair
SKU: T-E34L-S-MP-GT Item ID: 004829 Price: $55.00
Octal power tube (Max Plate Watts = 25W) EXCLUSIVE GT design. The heat wings attached to the plate give this version of the original EL34 15 - 20 percent more power. Interchanges in any EL34 application and stays tight and robust all the way up to full power. Highly dynamic, big low end and runs cooler for longer life. Amazing headroom, killer tone and all of the great features and characteristics of the EL34 design.
== = == === = ==
Vacuum Tube - 6CA7 / EL34, Mullard, Pentode
SKU: T-6CA7_EL34-M Item ID: 007479 Price: $179.90
The 6CA7 is a power pentode of the glass octal type. This tube is suitable for all applications which require peak powers of up to 11 watts from a single tube or up to 100 watts from two tubes in the normal push-pull arrangement. It is equally suitable for domestic amplifiers and public address equipment.
=== === = ==
EL34 Mullard Reissue
SKU: T-EL34-MUL Item ID: 004843 Starting at: $23.25
Copy of the XF2 Mullard EL34 of the 60s. The perfect power tube for the Dynaco ST-70 or vintage Marshall amplifiers. the best current production EL34 available Made in Saratov, Russia.
Last edited:
I use Klipsch and horn speakers
So I’m looking for very nice midrange and female vocals. The low end will be handled with a diy horn loaded subs on SS amps
I will be using a dsp with the subs and can do so with the tube amp
I know I’m not going to be even in the same Country as a Macintosh or some other brand of Tube Amp. I know this is near the bottom of the food chain and I just wanted to try to achieve the most I can with what I have. I’m not looking for any voodoo magic or anything like that. Just wanted to know from people with tons more knowledge than I do on what tubes I can put in it and not burn up the board. And then , I can use my own ears to hear what I like.
So I’m looking for very nice midrange and female vocals. The low end will be handled with a diy horn loaded subs on SS amps
I will be using a dsp with the subs and can do so with the tube amp
I know I’m not going to be even in the same Country as a Macintosh or some other brand of Tube Amp. I know this is near the bottom of the food chain and I just wanted to try to achieve the most I can with what I have. I’m not looking for any voodoo magic or anything like that. Just wanted to know from people with tons more knowledge than I do on what tubes I can put in it and not burn up the board. And then , I can use my own ears to hear what I like.
Test the tubes ok first somehow before you plug in. Different brand as listed should be ok unless they are defective. The power transformer is 200VA, it's enough to handle some differences at least as posted here: Boyuu EL34 A9 Tube Amp.
It's self biased with // 2x1000 ohms or 500 ohms non-inductive wire wound type, 6 watts.
It's self biased with // 2x1000 ohms or 500 ohms non-inductive wire wound type, 6 watts.
Attachments
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Valve/Tube rolling in Boyuu A9/A10
Hi - a slightly old post, and maybe you've got rid of the amp by now....?
Anyway, to answer your question:
The power valves (EL34B supplied) are 'fixed bias', ie it's detrmined by the 2x1000 ohm resistors in parallel giving a 500 ohm bias resistor. The bias current will vary slightly depending on what the DC voltage is (B+), which in turn depends on mains voltage and voltage drop across the rectifier. UK mains in ~230vac, but could be 240 or 220 and within spec.
You can drop in other valve rectifiers, the GZ34 will give the least voltage drop and therefore a higher B+. You can also plug in a solid state rectifier, with on time delay, which will give you the highest B+ voltage.
Other valves to try? EL34 (ie not B), 6CA7, KT77, 6P3P, 350C will all drop in and run with the as supplied fixed bias.
The 6N2 Chinese valves supplied may be substituted with Russian 6N2P-EV, but don't try to put in 12AX7 or ECC83 as a modificaion is required to the heater wiring (or use an adaptor).
I'll add that I tried ALL of the above in my A10 and perceived little, if any, differences. That was my aged 60 ears and not by any measurements.
The A10 is a lovely little performer and great value for money. If you have the 'scaffold' version (rather than PCB) you can easily upgrade caps, change resistor values and of course change valves.
Good luck!
Hi - a slightly old post, and maybe you've got rid of the amp by now....?
Anyway, to answer your question:
The power valves (EL34B supplied) are 'fixed bias', ie it's detrmined by the 2x1000 ohm resistors in parallel giving a 500 ohm bias resistor. The bias current will vary slightly depending on what the DC voltage is (B+), which in turn depends on mains voltage and voltage drop across the rectifier. UK mains in ~230vac, but could be 240 or 220 and within spec.
You can drop in other valve rectifiers, the GZ34 will give the least voltage drop and therefore a higher B+. You can also plug in a solid state rectifier, with on time delay, which will give you the highest B+ voltage.
Other valves to try? EL34 (ie not B), 6CA7, KT77, 6P3P, 350C will all drop in and run with the as supplied fixed bias.
The 6N2 Chinese valves supplied may be substituted with Russian 6N2P-EV, but don't try to put in 12AX7 or ECC83 as a modificaion is required to the heater wiring (or use an adaptor).
I'll add that I tried ALL of the above in my A10 and perceived little, if any, differences. That was my aged 60 ears and not by any measurements.
The A10 is a lovely little performer and great value for money. If you have the 'scaffold' version (rather than PCB) you can easily upgrade caps, change resistor values and of course change valves.
Good luck!
@Mission720,
At what operating point did you use 6P3P in a circuit designed for EL34B? My experience with 6P3P-EV is that the bias resistor must be increased to ensure the current remains as designed for EL34B. 6P3P is less robust, so even more caution should be used.
carlthess would have a hard time shoving a noval 6N2P-EV into the front octal socket.
Carl, just get a good NOS American 6SL7 for that socket.Yeah, it's a thread that's over a year old so who knows what the OP ended up doing with his amp. Perhaps he will post an update.
However, you're confused about the term "fixed bias". Fixed bias is when a negative voltage is applied to the grid of the tube from a negative supply of some sort and in most cases it is adjustable. In a fixed bias scheme, the cathode is grounded.
Bias created by a resistor between the cathode and ground is known as cathode bias or sometimes self-bias.
The A9 / A10 / A12 series SE EL34 amps seem to be quite popular, especially with tube newbies. The main difference between them seems to be the choice of input tube.
I believe the A9 uses an octal equivalent to the 6SL7, while the A10 uses the 6N2 and the newer A12 uses 12AX7s. They are relatively similar electrically but can't be interchanged.
They may be inexpensive but they are hardly lovely little performers. They have serious deficiencies. There's a recent thread which describes the problems in detail.
Reisong A12 review.
Her YouTube video series which addresses the issues is still in progress. She describes the stock amp as a "hot mess".
Boyuurange Reisong A12: Technical Review - YouTube
Earlier, she posted a "quick fix" that involves a simple tube swap.
Boyuurange Reisong A12: Quick Fix Tube Swap - YouTube
Just today, she posted some mods that go a step further toward improving the amp.
Boyuurange Reisong A12: Initial Modification Results = Win! - YouTube
Owners and prospective buyers should check out her entire series on these amps, which includes some other videos which I did not link.
I saw the YouTube vids, great advice. I commented on one of them re. Cascode. I ran the A10 with no mods whatsoever with EL34, KT77, 6CA7, 350C and 63P3. With the 500 Ohm bias it wasn't ideal for each option I tried but to my ears there was little difference. You get what you pay for, and great as a starter and base to mod.
What I want is a source for the potted output transformers: I have a bare A10 chassis which I want to populate. Any clues?