Single ended el34 schematic. EL34 Single-ended Class A tube amplifier KIT .

Single ended el34 schematic Choke 10H 250mA B-060. I've wired in a tone stack by-pass, using a 2p3p switch, that puts it into a tweed style tone set up. EL34 SE ultralinear schematic . Since a pentode has very high plate you can also use this same circuit with any number of pentodes or beam tetrodes. And now I want to try something different. You can see the bias pot for the EL34 protruding south, just to the right of the EL34 tube socket (above). Aiqin EL34 output trans questions: Schematic fo the amp 2. It seems to me that I could use the Hoffman 6V6 turret board and modify it slightly for a single-ended EL34 instead of the push-pull 6V6s. png. Re: Single ended EL34 guidance needed. Higher power can be obtained with very large This RIAA with same amplifier using EL34 Single Ended Amplifier on 18th Feb 2019 For KT88,6550,EL156,EL34 and KT120,KT90,6L6GC schematic diagram The people who made the amplifiers I made Let's celebrate the brave amp The original schematic has a 250 Ohm resistor here. This simple single-ended amp project by Pete Millett is a great performer and a very well documented project that was immediately adopted by many DIY'er's. The transformer I plan on using has dual 330VAC secondaries. I found a schematic at angela for a se el34 amp that looks do-able for me and I have a fair supply of el34's around. 2013-11-28 9:07 pm #6 2013-11-28 9:07 pm Class A single-ended amplifier to reduce distortion; EL34 vacuum tube amplifier brings you exquisite & refined music, particularly ideal for vocal music & chords; Bass is surging strong, middle frequency is soft and mellow, high frequency is crisp and clear, strong power and clear resolution The schematic has a center tapped Ultra Linear transformer. com capacitor per each output tube on the gates and a 10 ohm 1/2W resistor on each cathode to measure the current of a single tube. I would want to use a pair of 82 Heresy's I have and a Pas 3 or older H-K for EL34/6L6GC UL Mini Single Ended Amplifier's schematic replaced power transformer more big one finally connected as Triode with EL34, KT88/6550 sound like EL156/KT88 SE Amplifier triode connection. The power supply uses a 5U4G tube rectifier and a C-L-C filter. Top. C. Accessories price:$28. FWIW, I like the EL34 as a single ended output stage. 1955 schematic for a 3W stereo single-ended tube amplifier based on the EL84 tube and Mullard 3-3 design. All my audio projects I worked with were single ended triodes which puts out 2watts maximum. I already have the acrylic plexiglass for the custom chassis and have begun assembly, and now I'm looking for a good schematic for a single-ended EL34 or KT88 stereo amp. This is the improved Push-Pull Mullard EL34 tube amplifier circuit. 1 of 2 Go to page I am not proficient at reading schematics so I will need to study that some more. What I’m doing now is mating that preamp to an SE EL34. The schematic is quite close to Tubelab's SimpleSE, but at a lower voltage and current. I would like to build a EL34 single ended amp. Accessories price:$69. The problem is I just can't find any schematics Single-Ended 6550 Tube Amp Schematic with 12DW7 Driver Stage. 00. In this way each EL34 will have a load of only 2300 * 4 = 9200ohm. You find the instructions and original schematics here: https: Looking at the plate current vs plate voltage curve with grid voltage plots, the EL34 is pretty linear EL34 wired triode Single Ended Amplifier 4W rms EL32 Triode Connection Single Ended Amplifier Transformer are PMF-7WS(Noguchi Transformer Co Tokyo Japan). Managed to get it working 4years later, due to budget constraints. I do like the apparently simplicity and minimal number of components. He drew this circuit around 1992. A DIY Single-Ended (SE) Tube Amplifier Project that is compatible with KT88 / 6L6 / EL34 / 6CA7 tubes. Single-ended amps are usually fairly low power (less Yes I think that's the book, although I found the schematic here EL34 Single-Ended (SE) Tube Amplifier Schematic EL-34. There are various schematics online, but they all seem to come from people with problems. The 470 ohm cathode resistor sets bias at a 75mA which is only about 68% of the maximum plate dissipation so expect long tube life with this amp. 14. Single-ended amps are usually fairly low power (less than 15W say) and are invariably cathode-biased. The power supply uses a 5U4-GB dual rectifier tube. 7K ohm impedance primary. Hiya Chaps, Just been given 4 Mullard EL34's by a friend. single ended: The PDF of the single ended HIFI output trans by hammond 3. SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier Project (6N1P driver) by Alex Gendrano; I'd like to find a known good schematic using 6H8C and EL34 and build it using that. but normaly will be get 8W rms by penthode Ok built the amp from schematics above had to mod a few parts so I could use 6N3C as well as I can use EL34 power tubes seems to have a good sound, I got rid of feedback didn't make any difference I tried the 6SL7 EL34 from schematics on page 1 but just didn't like the output was low and damp. 2x 10 W single ended DIY kit ECC83-2xEL34 I have the same fuzzy schematic and because not all resistors had colour code rings, it was hard to really know which R had to go where. 247 KB · Views: 882 E. Power Supply. Output power will be about 5W. Schematic is from Build your own Audio diy single-ended Diy single-ended kt88 / 6l6 / el34 / 6ca7 tube amplifier, Remarks - diy. 5Wrms with 6550/KT88. EL34 Single Ended Amplifier on 2022 specially use for EL34 and KT88 if possible to use 6L6GC Single Ended EL34 schematic. i built 2 of those cheap Chinese EL34 kits using the schematic that uses both triodes of the 6sl7 tubes ( where plates and cathodes are tied . same circuit can be use for EL34 single ended amplifier only 2 parts need replace ,Power Trans and Out Re: HoSo56 Single Ended KT66, 2x5879, Ghetto UL--Put in a MidBoost « Reply #79 on: November 24, 2013, 07:25:07 pm » I did the separation of the mid pot from the tone stack this afternoon. The preamp is pretty much nailed down. Mikael Abdellah KT88 Single-Ended Tube Amplifier Schematic. this transformer is universal transformer. -User Name -Password From many months I This schematic is copied due to copyright, but most of it is the circuit designed by him. I built that amp with a way to externally adjust the cathode resistor. 6P27S (Cyrillic: 6П27C )" (EL34. affect the sound - sure. Ended single el34 schematic amplifier kt88 6550 se 300b cathode drive transformer ul audio amplifiers show here. The KT88 kagliostro shared was the first non hifi ultra linear type I have seen. The first is a high voltage transformer made for a 300B single. Yeah, it's analog and it's awesome! The AE1 uses a dual-triode 12AT7 as the driver stage, which is a medium-gain tube. The end result today is that customers My next planned move is to remove the output transformer and temporarily transplant it on a known good single ended EL34 amplifier I have on the bench now (same 3. KT88_EL34_SE_UL_400V_M1_adj. It has been suggested to me that single ended might be a good first building project. appreciate the answers. Z used in his Carmen Ghia (and also found in the Watkins Dominator)there were quite a few threads/posts on this on the sewatt forum. Anyone done that? A schematic would be apriciated 🙂 The thing is, I wanted to build a PP amp but i got 2 output transformers(for SE aplication), 2 ECC83 nad 4 EL34 for free. A 6N1P dual triode is used to drive the output stage. Please login or register. just I will show you 6550 SE Amplifier I'm not expert enough to say what should change, but it seems to me that for a single ended amplifier of this topology the last thing that should be needed is global feedback. (ECC85). EL34 Single-ended Class A tube amplifier KIT A schematic is not a kit, but allows point to point wiring, and easy modification versus a Printed Circuit board. Point to Point gives a lot of flexibility. since you have the unit, and those pics aren't very revealing, only you can verify the schematic. 3K on 8ohm load. Schematic by Michel Leluaux from "L'Audiophile" (April 92). Finished my second "PriestyAMP" project, a single ended amp based on a Blackface Champ aa764. Don't wait to be asked. After all of the playing around settled on The plate and cathode resistor values for the 6SL7 I got from the Angela super single ended schematic and the el34 values are fairly generic. El34 Push Pull Amplifier Schematic. EL34 SE-3. JUST DO IT! I EL34 Single-Ended 3. The use of a single tube in the output stage of the power amplifier is commonly referred to as a “single-ended” design. Hi All, Recently I purchased Douk Audio’s EL34 Single-ended Class A tube amplifier kit: EL34 Single-ended Class A tube amplifier KIT for power stereo audio HIFI DIY | eBay. I have such an amp with a 5965 driver and it's very musical. very clear but output transformer are small 7 Wrms so I got around 6. 5k EL34 : G1 to heater 10 pF 6550 : G1 to heater 15 pF 300B : G1 to filament 9 pF and the end of Nov 2006 I built up the other type of 6550 Single Ended Amplifier cathode chork loaded drived amplifier. same circuit can be use for EL34 single ended amplifier only 2 parts need replace ,Power Trans and Out Hoffman Amplifiers Tube Amp Forum, Single ended EL84. Joined 2012. PP EL34 Tube Amp Schematic by Mullard with Dynaco A420 (EF86, 6CG7 input) - [50 Watts, PP, Class-AB1] Legend: PP = Push-Pull, SE = Single-Ended, SET = Single-Ended Triode, SIPP = Self-Inverting Push-Pull, UL = Ultra-Linear Hello guys, Imlooking for a good single ended EL84 schematic. The complete schematic to implement the separated grid voltage could be found here. This design was chosen for its relative simplicity compared to the more This is schematic diagram for compatible single ended amplifier on 2024 Google helped me a couple month ago by Google content ans teach me how increase any way thanks Mr Google. Would greatly appreciate your input. Most are triode or ultra-linear. Two years ago I built a pair of "Statements" loudspeakers from the Hobby Hifi magazine - 95db efficiency, two ways with a 15" PA Monacor Ever since building the 2W single ended tube amplifier, I wanted to build something better, something that is considered a good amplifier among tube amplifier enthusiast. G. What's going on with the 100 ohm resistors on pin 2-7 (heaters) for the EL34? Typo, or am i just missing something? Here's the old thread over on DiyAudio. In combination with the screen resistor of 1k, this gives just about 12W of dissipation in the EL84 NEW Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization. For simplicity & aesthetics I prefer diode rectification in the power supply. nigelwright7557 said: In my experience of valve amp design I have never found DC heaters to help with noise. SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier Project with 6N1P driver - Alex Gendrano - (Project) SE KT88 Schematic for an 8 Watt Single Ended Tube Amplifier. EL34 Single Ended Amplifier on 2022 specially A schematic of the SE KT88 tube amplifier that I have built is shown below in Figure 1. Designing a single ended amp around a single tube is a gratifying challenge. Hi, Has anyone ever listened to or built a single ended el34 amp. Best SE KT66 schematic? . Edcor Seemingly most appropriate transformer. Global negative feedback. For the power output stage, the EL34 is a classic tube used in many high performance amplifier circuits. I will be happy with bigger power. The preamplifier tube is a 6N1P, but the 6DJ8 / ECC88 / E88CC family of tubes can be used instead. I need a bit of help, though, figuring out splicing the preamp from the Plexi 6V6 into a single-ended EL34. 2020-05-05 3:40 am #1 2020-05-05 3:40 am #1 Hi all, I have been in a journey of learning with my first tube amp, since 2012. Logged The schematic ended up just showing the KT 88. Best SE KT66 schematic? Thread starter Junk Audio; Start date 2013-11-28 2:22 pm; Status Not open for further replies. « Reply #5 on: October 14, 2016, 08:54:21 am » You have the tube, now spec out your iron so you have an idea of B+, impedance, drive requirements for the 34, get the PA section drawn up, or copied, then you can stitch about any pre section to your PA. Parts count will be low, complexity minimised. you can use that schematic - simply trace the wires in the unit to verify the schematic. It has the following design features I incorporated: - Adjustable Cathode Bias - Fan Cooling - Foot-switchable "Turbo Knob" feedback lift boost I like your schematic. I find the Edcore transformers to be pretty good value and quality for the money, but I recommend a 3. The schematic diagram is incorrect, in the grid of El34 the bias voltage is negative. the amplifier schematic, for details. Member. 2017-11-07 10:17 pm Good schematic for SE EL34/KT88 amp | Audiokarma Home Audio Stereo Discussion Forums . Welcome To the Hoffman Amplifiers Forum January 01, 2025, 08:06:34 pm: Welcome, Guest. 4 KB · Views: Single-Ended vs Push-Pull As I mentioned previously, push-pull (P-P which provides the E-linear feedback. The schematic is from the book "Build your This little monster delivers about 8+8w using a pair of EL34 SE in ultralinear mode. This feature allows you to connect your Bluetooth-enabled devices, such as a phone, to the amplifier. 1. 25 Single Ended 6V6/EL34/KT66/6550/KT88 Amp 06-06-2010, 10:41 PM. The Dutch Phillips company really had their stuff together when they designed that baby back in the 50's. Eli Duttman. This is schematic diagram for compatible single ended amplifier on 2024 Google helped me a couple month ago by Google content ans teach me how increase any way thanks Mr Google. The 6SN7 has a CCS plate load, and I just put both sides in parallel for simplicity. Download 1955-1A schematic in PDF. It uses much of the preamp of a Clubman, but with single and parallel inputs to v1 and a volume control added between 1v and v2, after the tone controls. Is your output transformer single ended? Or push/pull? A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. I've seen many applications of 6v6 tubes for single ended UL with moderately low output powers (5W OPT), that's why I'm Why single ended in the first place?Build a plexi in push-pull class A with two EL34's. Just tested them, and they are all good (AVO Mk3). The LL1627/185mA have a primary inductance of 9H and the EL34 have a nominal plate resistance about 910ohm and four 910 / 4 I'm getting ambitious and want a winter project for after Christmas. Diy Single Ended Se Kt88 6l6 El34 China-hifi-Audio online store Oldchen EL34 Tube Amplifier HIFI Single-ended Class A handmade scaffolding Amp - Oldchen EL34 Tube Amplifier HIFI Single-ended Class A handmade scaffolding Amp LaoChen 100% Brand New This price does not include the tube cover, if you need it, you can +$17 purchase a black protective cover or +$22 purchase a stainless steel protective cover . The EL34 is probably the best performing tube I have ever used in an ultra-linear circuit, be it push pull or single ended. It was last replied to over 3 years ago. Single-ended amps are usually fairly low power (less ST With Bluetooth : refers to the standard larger black amplifier that comes equipped with a Bluetooth 5. The power supply is solid state. pdf: Edcor gives a lot less info about their output transformers it seems, this is their website In looking at most single-ended plexi designs, the master volume is directly in front of the EL34. For additional information, pictures and schematics, see the complete page of Alex's DIY KT88 Single Ended (SE) Tube Amplifier project. Joined 2013. Not a bad buy with a sturdy and well thought out chassis. 2020-12-23 1:28 pm #9 2020-12-23 1:28 pm @andyjevans I'm thinking of building an single ended UL. DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier . Nothing particularly strange. Back to EL34 main page. Figure 1: Single-Ended (SE) KT88 Tube Amplifier Schematic with 6N1P driver stage. com the modified schematic is introduced on page 18 of the thread. EL34 Single-Ended 3. The amplifier section is generally the same Schematic. Attachments. My EL34 in Single Ended Triode Mode - Design. This design Which Silk Audio single ended output transformer? You can use the EL34 in Pentode mode, Triode Wired mode, and Ultra Linear mode. Most use Does anyone have a proven good schematic using 6H8C (6SN7) driver tubes and single-ended EL34 outputs EL34 Single-ended Class A tube amplifier KIT A schematic is not a kit, but allows point to point wiring, and easy modification versus a Printed Circuit board. Back to Top From the schematic and the pictures below you'll note that lugs one and eight are linked together and that a short length of yellow wire connects to the one end of the 880 ohm 25W cathode and the last of which runs through an EL34 pentode tube. GIF. I hope others have better luck them me on the 6SL7 An EL34 operating in single ended mode is only capable of 12w. 20. SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier Project with 6N1P driver - Alex Gendrano - (Project) SE KT88 The AE1 is a single-ended Class A amplifier using a design that is simple but rooted in a rich history of high fidelity audio. I have 5k output transformers made for el84 in pentode. The single ended amps I have built around this tube all have no feedback and all sound great. The power section is based on an Allen class act, as that was the only single ended EL34 amp I've seen a schematic for. Fun amp. I got rid of feedback didn't make any difference I tried the 6SL7 EL34 from schematics on page 1 but just didn't like the output was low and damp. I tried the 12E1, 6L6, I’m working on some ideas for a single ended EL34 amp and have a few questions. and small transformer so does not get good low edge. Junk Audio. So i tought why not try to Help Needed for Single Ended 6SN7+KT88 chinese schematic. My Supply voltage is a bit higher so I choose 470 Ohms to set the bias current at 32mA. Wikipedia) This circuit diagram My wish is to build a new amplifier - also single ended with a bit more power. I can The Dutch Phillips company designed this tube for audio applications in the 50's and specifically for an ultra-linear type loading. I tried the 12E1, 6L6, EL34, 807, and a few Recently I purchased Douk Audio’s EL34 Single-ended Class A tube amplifier kit: EL34 Single-ended Class A tube amplifier KIT for power stereo audio HIFI DIY | eBay. This is just my opinion, but I consider the EL34 THE best audio tube ever produced. 3V using a LT1085 voltage regulator. EL32/6Y6G Triode connection Single Ended Amplifier Schematic diagram 6Y6G SE Amplifier Hi Jordan, I'm not sure if this fits into the category of "ultralinear", but in one of my heavily modded valve juniors (single-ended EL84) I installed a conjunctive (corrective) filter similar to what Dr. Additionally, you can find the data sheets for each of these components. 5k primary impedence), to check if the issue does After you build a stereo single ended EL34 amp, you can make it into a push pull EL34 mono-block and duplicate it. SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier The EL34 contributes an early-Marshall soft crunch at high levels, but with the better harmonic distortion spectrum shape (more second harmonic and less higher-order harmonics) that you get with a single-ended topology with no feedback. 1; 2; Next. 0 module. EL34 Single-Ended (SE) Tube Amplifier Schematic with EF86 input stage. The schematic shows a transformer with 230VAC secondary and solid state rectification for the B+ supply, with B1=278V and 268V at the EL34 anode. circuit diagram says: May 26, 2011 at 1:43 am. However, it came win NO documentation of any kind. Thread starter Tibetan; Start date 2023-01-16 6:40 am; Status Not open for further replies. If you want to do simple, then use an LM334 current sink, a 12AY7 Schematic Diagram E34L/EL34 Single Ended Amplifier Note:EL34 single ended amplifier will be get 10W rms by good condition of power supply and good Audio Out Put Transformer. here is a schematic for the Knight Kit 60 Watt stereo basic amp: Whether you build a single-ended or push-pull amp, you are right to choose the best components, but perhaps even more important is to pick the right topology and Oldchen Silver EL34 Tube Single-Ended Amplifier HIFI EXQUIS Class A Point to Point Bluetooth 5 OC34 LaoChen Lamp Amp - OldChen - Oldchen Silver EL34 Tube Single-Ended Amplifier 6SN7 5u4g - Label: New - Category: Single-ended el34 amp - Price: $ 228. Max 7W rms input. It is basically the same as an ordinary gain stage, but instead of a load resistor we use an output transformer. Accessories price:$35. Reactions: stenak. Circuit Diagram This area is a growing library of the schematics, wiring diagrams and technical photos. Shuguang EL34-B (EL34B EL34) Vacuum Tube. Thread starter cognac; Start date 2020-05-05 3:40 am; Jump to Latest C. All tubes are included, and the Bluetooth antenna is installed on the right side of the amplifier. Hammond output transf. Amplifier. 12AX in a tube. Its well drawn EL34 tubes can be used in place of the KT88 valves. To bias it Class A simply use a plate voltage of about 250v and drive the crap out of the EL34's current-wise. The single-ended amplifier circuit uses a 6550 high power tetrode vacuum tube in the output stage. For the output transformers I chose the Lundahl LL1627/185mA with secondaries connected in B configuration to have a primary load impedence of 2. The single-ended (SE) power output stage is the simplest form of power amplifier. the schematic is from the Dynaco Super Fidelity Output Transformers catalog. After looking at several ideas from other guys’ posts here and in AX84 I’ve come up with the hand drawn schematic attached. I have found lots of single ended EL34 and 6L6 amp ideas. the new EL34 Parallel Single Ended by Andrea Ciuffoli - 2004 contact me for any problem or question: webmaster@audiodesignguide. Post by Andy Le Blanc » Wed May 17, Many thanks for the help - I've decided to go with the SRPP 6SN7 EL34 circuit. Single-Ended 6550 Tube Amp Schematic with 12DW7 Driver Stage. Single-Ended (SE) EL34 Tube Amplifier Schematic with EF86 input stage. DIY Audio Projects Forum: FAQ: Last visit was: 02 Jan 2025 9:52 pm: Mullard EL34 Push-Pull Tube Amplifier Schematic Like: - Even my later model Sunn 200S, that had 6550 output tubes, ended up sounding better with the EL34. Power 6W. The filament supply is regulated at 6. What I’m doing I already have the acrylic plexiglass for the custom chassis and have begun assembly, and now I'm looking for a good schematic for a single-ended EL34 or KT88 stereo Figure 1: Power Supply Schematic and the last of which runs through an EL34 pentode tube. This parts list provides the manufacturer and part number for all of the electronic components that were used to build this device. Joined 2004. Tube amp Schematics index page There are over 3500 Tube amp schematics and other types of schematics in the EL34World Schematic library. However, The single-ended (SE) power output stage is the simplest form of power amplifier. jpg. 1, the amplifier schematic, for details. I plan on using the 5Z3P for rectification, and will have Mullard EL34 Push-Pull Tube Amp Schematic with Dynaco A420 Transformers. Most Silk single ended output I’m working on some ideas for a single ended EL34 amp and have a few questions. Shuguang 6SN7GT (6SN7) Match Pair. the easiest thing to do is to unsolder the first cap and replace it. The amplifier circuit shown uses the Dynaco A420 audio output transformers which have a primary impedance of 6600 ohms. 100% plate dissipation. I only get 3W undistorted on my scope, then one half of the wave collapses. Prev Next EL34 SE V Single-end Tube Amplifier 10W+10W Kit (Stereo) Order Code: AM002378; Brand: Analog Metric; Looks like straightforward pentode mode single ended el34 with cathode bias. That would not have an air gap, and single ended amplifiers need an output transformer that has an air gap. That would be 50% Ultra Linear (there are few 50% tap UL output transformers). Also with socket for EL84. The tone stack is a brown face Fender type and I adjusted the capacitor values to suit my tastes. anytime you change a part, there is a change in SQ, Basically, it is a single ended EL34 amp (though a pair of EL34's is the one thing I don't have, so that could change) with a 6SN7 as the driver. If you see a problem with any of the schematics, please email me so I Hello! After a first happy ecl82 spud-amp SE build, well first of all I learned a lot, but now I'd like to take that information and make a similar but better built amp, maybe a bit more powerful too. This is a custom-made transformer with a large capacity transformer as the power transformer. Peavey wiring schematicsTube vacuum socket wiring valve power amplifier diagram schematics electronics output audio guitar diy pinouts amp radio data number projects 13+ el34 world schematicsAnd show you schematic here. I hope they did not "simplify" (cheat) by using a center tapped push pull transformer. the bias circuit is incorrect. 5k called) had developed a wide product range covering all areas of two channel audio: a single-ended 300B product line, an EL34 classAB and single-ended product line, digital to analog converters, pre-amplifiers, Phono stages, and Audio Note (UK) speaker kits. bepone Single ended EL34 amp design. With a number of different KT88 tube amplifiers we have had good results using new production JJ KT88 Blue Glass and Genalex - Gold Lion KT88 tubes. There is also a huge library of effects and solid state schematics. cognac. gingertube. provided beast schematic will humm enough to be annoying, with SE power supply must be CLC or CRC before anodes. The output thansformer is rated 2300ohm and can be used to build a lot of project using famous tubes, like 2A3 and 300B. Higher power can be obtained with very large EL34/KT88/KT-120 and 6L6 Single Ended Amplifier for Chile Model as Gen 3 This circuit configuration is like before, it is a circuit that was tested more than 10 years ago. Refer to Fig. Bas This schematic is copied due to copyright, but most of it is the circuit designed by him. Reactions: Bill Ferris and StepheK. Jean Hiraga's single-ended KT88 tube amplifier schematic with 12AX7 (ECC83) tube input stage. lqgho htjo xfn iahug zweazkx jftnpzq fxkih onz hiciv kdweoqmx