Parafeed Output Transformers

5k load for 45. Very low output impedance means it can even drive a pair of sensitive speakers. Welcome! Need support, you got it. , but they make output transformers necessary with higher DC capability in the primary winding or the use of the parafeed design together with a choke load. Hi Nattawut, a T pad attenuator acts like a constant impedance device, not a constantly resistive element. The second one is called the output coil. Western Electric 171c Output Transformer For A 124b Tube Amplifier. Is there a way to use a PP tranny for SE operation. Both Parafeed chokes are oneElectron, and the output trannies are Magnequest EXO-50 pinstriped nickel and iron - see a pattern here?. Cheers !!! Posted by Nattawut Uamkruea at 11:00 AM. the transformer design. The size of our anode choke alone is already bigger than many output transformers of competing amps. Since the topology is parafeed and no DC current is passing thru C2 or the output transformer, each tube operating point is stable and predictable irrespective of switch position. Having built two OTL amplifiers before I wanted to avoid the largish output capacitor and planned to build it as Parafeed amplifier. Transformer DY28 Radio part Radio Instruments Ltd RI. For sale by owner are train transformers, Lionel, Marx, AF, LGB, Marklin and more, mostly variable AC voltage output (027, O gage and Marklin HO), some with variable DC voltage output (for N, HO, G gage). The topology is fully balanced, open loop (no gNFB) amp with parafeed transformer output. In order to obtain the full output power each supply transformer should be rated at 40VAC - 0 - 40VAC at 640VA. we associate with audio, 300b, EL34, 2a3 and so on have been designed. Anode chokes, interstage, headphone and line output transformers. pr 1950's era Peerless S-265-Q 20-20 series huge potted output transformers W-E SE Parafeed,tube output transformers,a pair, with solid silver secondary/s NOS NIB Triad S-34X Output Transformer 4000ohmCT 30-20000CPS 7. If you are using line transformers for outputs, I'm pretty sure they are not gapped. For my dream preamp, we finally decided to use the parafeed circuit -> see below. The fully transformer-coupled (input and output) spud/parafeed design, utilizing a single 6S45pi tube for both voltage and current gain, is pretty unique and not something that I've seen from any other major headphone manufacturer. Established in 1989, MagneQuest has been building the finest vacuum tube audio transformers for nearly 25 years, yet our roots run much further back, to the heyday of transformer design. The meters show 248 volts across the KT-88, -21 volts on its grid. 3k5 output transformers are often seen used in 2A3 schematics and trade a little output power for slightly lower distortion. For sizing, on the 1st picture, the desk lamp measure 12 inch it was during construction. Ht is around 260 volts from a 6X4 tube rectifier, (great compression when amp is flat out). R7 is essential as the two pass resistors are 600 ohm too because in this case the three resistive elements are chosen to ensure that the input impedance and output impedance match the load impedance which forms part of the attenuator network. Luckily I found some information about an Aikido Parafeed on the internet and, for the first time, I had the amplifier on a breadboard first for testing and evaluating!. Ship weight 4. Prestigious moving coil transformer, 1:16 or 1:32. MIKE OF MAGNEQUEST'S GENIUS & DOC BOTTLEHEAD'S 2A3 PARAFEED. 1uF cap would have been fine at 7Hz. Thank you for your interest in my vacuum tube based circuits: DG300B, Novar Spud, 6LU8 Spud, and Universal Filament Regulator. This current does not pass through the transformer; rather the transformer is connected to the plate in parallel with the current source. The price was right at about $34 for the pair as of this writing and they're a perfect fit. The plate chokes for the EL84 is custom wound, 35H @ 50ma plate chokes. The pre was tested and performs dead flat from 20Hz to 25Khz. Any of my search term words; All of my search term words. If the load is 32Ω, the transformer is configured in 12:1, so the total load presented to the stage is about 5,184Ω. Thanks Rob. Both methods eliminate DC current imbalance in the windings. 5k load for 45. 6gf7 amplifier instruction. 6c33c Set Schematic It is a very interesting idea to apply 6C33C tubes operating at the utmost level of they set the tubes at 0,6 A at idle so they must use a low supply voltage under. I contrast, the parafeed topology keeps the inductor (choke), but forgoes the shunting capacitor to ground, relying on the inductors high inductance to shield the triode's plate and the output transformer's primary from the ripple. Designs to 100 watts. While I can't guarantee or imply you should try - 9000 Ohm Primary, 16LB transformer with 30W Core, excellent 20-20KHz frequency response, very wide Bandwidth from 7Hz-50KHz; this transformer may be a very good candidate for the Parafeed Single Ended Output Circuit for tubes such as 845 and 211 Triodes. SE 35, there are 8 output tubes for 2 channels and nobody enjoys 8 bias adjustments. A transformer usually consists of two coils of wire wound on the same core. The power supply's output voltage always decreases as more current is drawn. Parafeed and Sakuma principle. Most parafeed amps have a plate choke. For a lot of headphones a 0. Cheers !!! Posted by Nattawut Uamkruea at 11:00 AM. The DAC can do only 1Vrms maximum due to the TTL output logic. 600ma per side of the O. For the first time ever, all of Beetho. SE 35, there are 8 output tubes for 2 channels and nobody enjoys 8 bias adjustments. In response to requests from our customers for quality transformers with which to drive output valves these carefully designed and built products have been assembled. The size of our anode choke alone is already bigger than many output transformers of competing amps. High voltage designs. 'il Monstro' DIY low-voltage 845:845 parafeed amplifier (282 pounds, 5 watts). Tubes do only voltage amplification. Turns ratio: 5. A parafeed transformer is somewhat easier. More about our products. The combination of cap and transformer in the output and the DC biasing require some extra design considerations, but the payoff is worth it. Single-ended, pseudo dual-mono, direct-coupled, parafeed circuit with Magnequest Plate Chokes and Output transformers. Since the topology is parafeed and no DC current is passing thru C2 or the output transformer, each tube operating point is stable and predictable irrespective of switch position. Kt88 Single Ended Schematic Read/Download Find out more about Single-Ended (SE) KT88 / 6550 Tube Amplifier Schematic, like comments, which Stumblers liked it, how many Stumbles it got, who added it. The transformer has no internal Faraday shield or magnetic shield housing. A transformer usually consists of two coils of wire wound on the same core. Where I don't want to slog through in a half-understood language, I use Google's translation page. Input and parafeed line output. Interstage, headphone and line output transformers. I tried a parafeed with toroidal too. The parafeed circuit is also a 1930's invention to keep the DC on the output plate of the tube out of the output transformer without using a cap or transformer directly in the signal path, thus allowing for a much smaller transformer. By using an output or signal transformer with a suitable turns ratio, class-A amplifier efficiencies reaching 40% are possible with most commercially available Class-A type power amplifiers being of. Prestigious moving coil transformer, 1:16 or 1:32. 65k ohm so you can DIYing the 2A3, KT88, 6336, 6528, 6C33C SE Parafeed amplifier. One of the songs he played was by Johnny Hodges. Output trannys contribute most of the distortion in a valve amp and have a limited bandwidth. Yet we build our tube headphone amps with giant M6 cores that take no advantage of the low level signal w. The output stage may be configured for either a 300B tube or 2A3 tube using cathode bias. We agree that time when people will want better will come sooner or later. "The "parafeed" (parallel feed) uses a large choke to provide the DC voltage to the anode (of the power tube, bold characters are mine). For sale a pair of used excellent Lundahl LL1627 PPZ parafeed output transformers. Thanks for A2A… The Transformers are electromagnetic devices that transfer electrical energy from one circuit to another by principle of mutual induction. Output Impedance Switch Kit for S. This is a 20 Watts, 5000 Ohm to 0-4-8-16 PP transformer, It accepts up to 90mA common current and a 9mA unbalance. High level input, 1+1 : 2+2 :. High voltage designs. This makes it practical to return the parafeed output transformer to the cathode even if the output transformer is not rated to operate with a DC voltage between the primary and the core or secondary. Ref: SE transformers,a pair, secondary/s silver solid with Parafeed,tube output SE Parafeed,tube output transformers,a pair, with solid silver secondary/s. Direct coupling is near impossible for 845. The output transformer I'm going to use has a max dc current of 806ma per side and my current draw is approx. Hi Nattawut, a T pad attenuator acts like a constant impedance device, not a constantly resistive element. 'il Monstro' DIY low-voltage 845:845 parafeed amplifier (282 pounds, 5 watts). The cathode-follower stage provides a low output resistance for driving the output transformer. The sound is very rewarding. Established in 1989, MagneQuest has been building the finest vacuum tube audio transformers for nearly 25 years, yet our roots run much further back, to the heyday of transformer design. Note that you cannot use them like a standard SE transformer since they do not have an air gap and cannot tolerate much DC. We normally design for an LF -3 dB point at 20 Hz maximum. For sizing, on the 1st picture, the desk lamp measure 12 inch it was during construction. Distribution transformers are rated between 3 and 500 KVA with 601 volts or more. Complete specs are available on Lundahl website. The question is how do you decide when saturation is going to be a real problem. Our team has searched all over a huge group at awesome asking prices. One of the songs he played was by Johnny Hodges. To reduce magnetic. Welcome to CAM, a classifieds site for used audio and hifi. High level input, 1+1 : 2+2 :. mismatchs (5K to 16 ohm, used as 2. We agree that time when people will want better will come sooner or later. (grin) KRK 11/27/2005. The transformer for the supply should be matched to the expected power you wish to obtain from the amp. A very nice sounding mid/upper class Tube amplifier. Audio transformer for tube preamp line output LL1930 LL1930 is designed to be a line output transformer for tube preamp parafeed output applications. required winding it. The Parafeed have roughly twice the inductance as compared to standard products, but for that can take zero DC current. A single-ended triode (SET) is a vacuum tube electronic amplifier that uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. This was further enhanced with a parafeed design, where the tube is loaded by an inductor (or choke) and the output transformer is coupled to the tube with a capacitor. Or share your ideas and. This choke must be large in value, and provides a relatively high impedance at audio frequencies. The following table shows the recommended transformer voltage and VA rating for a single channel - either use two transformers or a single unit with twice the VA rating shown for stereo. REDDI vs P15 Poll Time. 7μF Clarity Cap ESAs were used as the parafeed caps. For sale a pair of used excellent Lundahl LL1627 PPZ parafeed output transformers. Most parafeed amps have a plate choke. Would that be fine to use them, considering the 'standard' seems to be 5K. The primary coil or input coil is connected to supply side while secondary coil supplies power to load. The price was right at about $34 for the pair as of this writing and they're a perfect fit. i have been reading and reading again about the 1:1 bifilar plate choke as 1:1 output transformer without need of parafeed coupling cap but i can't understand how it works. I'm thinking this might be a problem. Get the best deal for Amplifier Parts & Components from the largest online selection at eBay. The secret behind the Zen Triode output transformers is that they are patterned after the older Peerless iron that was hand-scramble-wound for ultra wide bandwidth and flat response. driver tube must have high voltage and current capable. The low output impedance of both versions provides robust performance into just about any preamplifier or power amplifier. Resistors provide bias, negative feedback, and give the FET a bit of 'plate resistance' like a triode to lower output impedance. Would that be fine to use them, considering the 'standard' seems to be 5K. NEW PAIR NIB UTC LS-35 Output Transformers EL34 2A3 300B 6B4G Push Pull Tube AMP. SE Parafeed,tube output transformers,a pair, with solid silver secondary/s For the 300B, etc KB tubes, etc, and other audio power output tubes. The meters show 248 volts across the KT-88, -21 volts on its grid. GM70 amplifier with Fiat transformers started on September 15 st, 2009 BEWARE! This is an expert-only project because the high power supply voltage, about 1KV. RIAA correction is still part of the input pentodes' plate load being dc-coupled to the next stage. I use quality film caps for cathode bypassing and the parafeed caps. Document Revision History Rev 1. In response to requests from our customers for quality transformers with which to drive output valves these carefully designed and built products have been assembled. 6 watt) will fit. Any more than that, and a Spud-Single Ended vs. It differs from the Crack in that way as the Crack is an output transformerless (OTL) amp. $1150 and up. The transformer for the supply should be matched to the expected power you wish to obtain from the amp. It should be noted, however, that the disinctions between film. 600ma per side of the O. Our history runs deeper than any other audio transformer maker in the world. Transformers used between the record medium and loudspeakers. This choke must be large in value, and provides a relatively high impedance at audio frequencies. Earle, as a designer of valve amps do you have any comments on the effect of connecting speakers with a low impedance of only 2 ohms to an amp designed for an 8 or 4 ohm output? Obviously, DIY or commercially built I'd rather not damage the output transformers or output valves by doing something stupid that could be avoided. One can use a step down direct feed line output transformer, such as LL1671/30mA. Pair of UTC LS-6L3 Push Pull Output Transformer or 845/211 Parafeed Single Ended. This low impedance is the driving point for the primary of the output transformer TR3a. Audio transformer for tube preamp line output LL1930 LL1930 is designed to be a line output transformer for tube preamp parafeed output applications. Single-Ended Output Transformers. 1 300B/2A3 Monoblocks Pair Kit Read more; Quickie 1. Get the best deals on Vintage Tube Output Transformer when you shop the largest online selection at eBay SE Parafeed,tube output transformers,a pair, with solid. The price was right at about $34 for the pair as of this writing and they're a perfect fit. Another choice would be to use a parafeed line output transformer , such as Jensen JT-10k61-1M. Goto page 1, 2 Next Forum Index->. Thanks Rob. I tried a parafeed with toroidal too. Classic Tube Output Audio Transformer Overview - Hammond Mfg. 4% similar) These transformers have all cobalt lams and brass channel frames. Home > Tube Amplifier Kit > Power Amplifier Kit > 2A3 SE. For sale by owner are train transformers, Lionel, Marx, AF, LGB, Marklin and more, mostly variable AC voltage output (027, O gage and Marklin HO), some with variable DC voltage output (for N, HO, G gage). Steve Bench covers various outputs using no DC, such as RC coupled and Parafeed, ect. It has stereo unbalanced inputs and parafeed transformer coupled outputs. Layout wasn't my best but at 5000 volts DC supply, you need lots of room around for safety and heat dissipation was around 1800 Watts All tube are choke loaded on magnequest iron! (parafeed circuit). Parafeed transformers are a non-catalog product, and JACMUSIC supplies those on customer order, at no extra costs. Western Electric 171c Output Transformer For A 124b Tube Amplifier. Pair of UTC LS-6L3 Push Pull Output Transformer or 845/211 Parafeed Single Ended. Due to the dwindling sales of these circuits, and to my efforts to position Neurochrome as a state-of-the-art solid-state DIY circuit manufacturer and vendor, I have decided to discontinue my vacuum tube circuits. com High performance audio transformers for audiophile applications from Lundahl Transformers. Ungapped transformers are unsuitable for most SE use. The Admiral output transformer is a bit larger than the original Magnavox OPT, ( probably because the two secondary windings, 16 and 8 ohm) and it's crowding the 12AX7. Unlike many designs relying on the reservoir capacitors to supply peak currents, I prefer to have the raw power available from the transformer resulting in much faster transients. which uses custom wound Electra-Print output transformers, which render it no longer a Less-pressivo (more on this later). Just another OTL Headphone Amplifier It started out as a replacement headphone amp (you know, for work) and got lost along the way. Toight like a toiger bass. IV/DAC ΜC TRANSFORMER –Power Amplifier input 142,60 S-9570 METAΣΧΗΜΑΤΙΣΤΗΣ MC 9570 SOWTER 1:10 MU METAL ( 76% Nickel core ) 179,60. The parafeed output is shown in its AC form below (Figure 1). The pre was tested and performs dead flat from 20Hz to 25Khz. In our case, the direct opposite is true. For this SE 300B triode tube amplifier build I have used premium parts throughout, Lundahl audio output transformers and a DIY chassis. In the past, parallel-feed designs were used to minimize costs and weight. Parafeed cap. The primary coil or input coil is connected to supply side while secondary coil supplies power to load. There is a hole in the commercial market with regards to low level (<2V rms out) high ratio small core output transformers. Push Pull: The Fight of the Century by Eddie Vaughn meister will fall to the oor convulsing, ears covered, at the thought of putting anything extra in the signal path to contaminate the. Here's the. Single-ended, pseudo dual-mono, direct-coupled, parafeed circuit with Magnequest Plate Chokes and Output transformers. All of this is output through magnificient Magnequest S240 Push-Pull output transformers. A small transformer loaded tube SET amplifier drives the RIAA transformer system,and the RIAA equalization curve is achieved within 0. ok I'm going back and forth on this I know the advantage of parafeed is to keep the output transformer from saturation. The stock 3:1 Class B Driver Iron was changed to a UTC Linear Standard LS-21. They are huge 200w units and were salvaged from another project. The output impedance of the gyrator is 1/gm. It would be a mistake to condemn it on technical grounds. This is called a bridged parallel feed or parafeed configuration. There's even enough room for the clever homebrewer to drill holes to squeeze in some parafeed output transformers. A single-ended triode (SET) is a vacuum tube electronic amplifier that uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. All if in perfect shape, as new, about a year or so old. - Tung-Sol Round Plate 6SN7 with high quality tube socket adapter. The output stage This is a transformer-coupled triode stage, using the E280F supertube. I chose to do this later under pages 33 & 34. Parafeed (parallel feed) is a clever way to reduce the demands on the output transformer by shunting the DC plate voltage through a capacitor. 6c33c Set Schematic It is a very interesting idea to apply 6C33C tubes operating at the utmost level of they set the tubes at 0,6 A at idle so they must use a low supply voltage under. All of the line output transformers I have ever seen need some kind of load, but its not so much for transient response as for flat frequency response. 30 Watt Audio Power Amplifier Schematic Including Preamp, Tone Controls, Reg dc Power Supply, 18 Watt into 8 Ohm - 30W into 4 Ohm loads This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. Years ago I had bought a Neumann module which was part of a tube lathe system. US Patent 1,422,653: Electrical transformer for regulating or varying the voltage of the current supplied therefrom by Edmund Berry, July 11, 1922. Transformers will always have their place. Backup - Monarchy SM70 Single-ended zero-feedback MOSFET amp: Preamplifier (or None if Integrated): 'Not-so-matic' DIY parafeed globe 27 with Altec 15095 output transformers. From Bottlehead: "Parabee is short for parallel feed 300B. Transformer winding is an extension of the fitting and turning industry. The power supply’s output voltage always decreases as more current is drawn. 2 ratio tap for 300 ohm headphones with the same output impedance means a damping factor of about 20. The Magnetics begin with the well-tried and quiet Hammond 373BX Classic Series power transformer, separate Hammond chokes for each side, separate filament transformer then finish up with Magnequest BCP-15 Plate Chokes and Robin Hood Nickel Pin-striped Parafeed output transformers. The parafeed output is shown in its AC form below (Figure 1). IV/DAC ΜC TRANSFORMER –Power Amplifier input 142,60 S-9570 METAΣΧΗΜΑΤΙΣΤΗΣ MC 9570 SOWTER 1:10 MU METAL ( 76% Nickel core ) 179,60. I've read online that designing your own output trannies is next to impossible due to the advanced technowizardry that goes on in them. Home > Tube Amplifier Kit > Power Amplifier Kit > 2A3 SE. smooth, clean, extended, and dynamic. The final output transformer is a 1:4 Guanella Transmission Line Transformer (1:2 turns ratio) So the voltage at the primary of the final transformer will be ½ that of the secondary and the current will be double that of the secondary. Single secondary SE output transformers available with primary and secondary impedances of your choice (within reasonable working values). The capacitor between the tubes is the parafeed cap, and a UTC output transformer is on the right. Does this mean that I could wind my own super-duper-mega-deluxe output trannie for my pseudo-champ with 4-8-16 ohm taps. Any of my search term words; All of my search term words. CM-27101 Parameter Conditions Typ. It should be noted, however, that the disinctions between film. Can be reconfigured for 112A or 6SN7 tubes in a few minutes. Joe Aigner's test version of a 5687 based line stage with two kinds of output transformers (using parafeed and ultrapath circuits to choose from, so it was a great way to compare both concepts. The secret behind the Zen Triode output transformers is that they are patterned after the older Peerless iron that was hand-scramble-wound for ultra wide bandwidth and flat response. The new design reaches an even higher level of sonic pleasure and quiet operation. Hi All, I have an abundance of 6sn7 family tubes and I wish to make a headphone amplifier using ONLY the 6sn7 throughout. This allows flexibility and further reduces costs. Lundahl transformers tube amplifier transformers are built in our dual coil single C-core style. Interstage, headphone and line output transformers. With your B+ limits you'll need to use a parafeed choke or a higher voltage power transformer. parafeed) output, a topology championed for use in modern single ended amplifiers by Bottlehead and MagneQuest. Even without a lot of tinkering or changing of parts, it sounded better than my single feed amp. smooth, clean, extended, and dynamic. The key design parameters are the reflected load impedance, power rating and lowest full power frequency. All of the line output transformers I have ever seen need some kind of load, but its not so much for transient response as for flat frequency response. For the 300B, etc KB tubes, etc, and other audio power output tubes. The short circuit from the top of the plate choke to ground represents the ac short that is provided by the dc power supply output capacitors and low impedance of the PSU. Tuesday Tube : RE144UX Telefunken Will using in next preamplifier parafeed with line output transformer. Here is the schematic of the amplifier and except for the parafeed topology is fairly typical of 6E5P - 6C33C amplifiers. MagneQuest/Peerless Forum. Single-ended, pseudo dual-mono, direct-coupled, parafeed circuit with Magnequest Plate Chokes and Output transformers. In order to use them in conventional transformers, the size must be increased and - more important - the air gap must be increased so that the permeability advantage disappears. I am building a single ended amp 5Y3, 6V6GT, 12AX7 and have a nice 10watt push pull output transformer off a hi-fi amp. In parallel feed, the usual air-gapped output transformer is divided into an air-gapped plate choke and an output transformer with interleaved core laminations. Hi Nattawut, a T pad attenuator acts like a constant impedance device, not a constantly resistive element. Electra print, parafeed, output transformer and load choke. Phew! Note that Ultrapath or Parafeed is of course, optional. Description: Paper layer wound output transformer that was actually replicated from a '50s original transformer!This is a must for the purist that wants the most accurate type replica for any 5E3 type project or for a. This is a 20 Watts, 5000 Ohm to 0-4-8-16 PP transformer, It accepts up to 90mA common current and a 9mA unbalance. Whether stepping down for low voltage electrical equipment or creating a custom wiring project that requires a current transformer, today's industrial and technology companies need reliable transformers for a wide range of projects. Uses a 230V primary, 9V secondary Talema 30VA mains toroidal transformer as the audio output transformer (OPT). Got a idea about preamp, which was based on parafeed µ-metal transformers. If not shown, inquire. - Tung-Sol Round Plate 6SN7 with high quality tube socket adapter. The topology is fully balanced, open loop (no gNFB) amp with parafeed transformer output. 65k ohm so you can DIYing the 2A3, KT88, 6336, 6528, 6C33C SE Parafeed amplifier. 15: 6DN7: Mr. They are huge 200w units and were salvaged from another project. This is a pair of EXO-050 (5K - good for 45, 50, 211, 811, 845, GM-70, etc…) parafeed output transformers, with 2, 8 and 16 ohns output taps. I do think that it's highly inaccurate to characterize line output transformers, as a group, as requiring a substantial or specific load on the secondary to acheive proper transient response. The output tube grid gets the goodness of a grid choke with low DC impedance to ground but high AC isolation, and the signal path is much more direct than a typical interstage transformer. Description: Pantheon Audio is a full-line Magnequest transformer distributor. Transformer DY28 Radio part Radio Instruments Ltd RI. The third ( output) stage, is a transformer-coupled triode stage, using the E280F supertube. For more details and a schematic, see the EF86 / EL84 Parafeed amp thread. For the first time ever, all of Beetho. A single-ended triode (SET) vacuum tube electronic amplifier uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. The transformer works to transform the high impedance, high voltage, and low current signal at the tube's plate to a low impedance, low voltage, high current signal at the output. NEW PAIR NIB UTC LS-35 Output Transformers EL34 2A3 300B 6B4G Push Pull Tube AMP. Circuit Topology As for circuit topology, SE (single%ended) has the reputa- tion of being the transparency and "directness" champ,. Based on the successful Torpedo planform, the Torpedo III is also of parafeed design, but differs in the unique differential amplification stage prior to the output transformers. If you have the patience (not an easy mod) its a definate upgrade. Would that be fine to use them, considering the 'standard' seems to be 5K. Reply Delete. 96 Pair of UTC LS-6L3 Push Pull Output Transformer or 845/211 Parafeed Single Ended. 47uF coupling caps to the output tubes could have been smaller; the -3dB point for the. Got a idea about preamp, which was based on parafeed µ-metal transformers. The cathode-follower stage provides a low output resistance for driving the output transformer. For the parafeed push-pull, I used this schematic with lightbulbs substituted for the DN2540 as resistors. I just completed eplacing the stock output transformers in my Moondogs with Magnequest Cobalt EXO-36 / EXO-03 transformer / inductor combinations. The grid resistor for each tube ensures that the bias is set correctly for each tube. The parafeed output is shown in its AC form below (Figure 1). The output transformers were Antek 2212 toroids. Think of it as two single-ended parafeed amplifiers sharing a common output transformer. The parafeed (parallel feed) design solves the problem of DC current in the output transformer but has its own issues. SE 35, there are 8 output tubes for 2 channels and nobody enjoys 8 bias adjustments. Fill in your output transformer specifications Type - Select - SE output PP output SE parafeed output SE interstage PP interstage SE line level PP line level Core material FeSi iron-silicon C-core Amorphous Nanocrystalline Advice me. It is available (parafeed). Probably have to do a bit of "data mining" to find out any details Yellow_Light_Colorz_PDT_02 The chief advantage is that parafeed gets the DC current out of the OPT primary, so amy problems with core saturation become a moot point. Is there a way to use a PP tranny for SE operation. Push-pull transformers connect two tubes in an arrangement that creates two equal and opposite currents, which cancel each other out (in a perfect amplifier). Be careful, it can kill you! Keep always one hand (better if it is the left hand) behind your back. Example (again from audiophilery), vacuum tube output transformers (single ended output type) typically satisfy the 20-20kHz frequency range, while handling an equivalent amount of DC as signal (i. Thanks Rob. The output transformer is a standard 4500ohm/8ohm unit, it needs to be of very high quality (>40H), and possibly very low secondary winding DC resistance. For sale a couple of Magnequest nickel 3K output transformers for parafeed single ended 2A3 or 300B amplifiers. From the Bottlehead site: The two stage zero feedback RC coupled circuit uses parallel feed (a. 1:1 bifilar output to remove the parafeed coupling cap. The ESAs are the same size as the SAs but with slightly nicer specs and tighter tolerances. The parafeed is effectively acting as a distortion generator in comparison, which isn't a bad thing at all in itself but personally I would forgo the mess of parasitics involved with transformers unless it offers a specific sound you like. SE Parafeed,tube output transformers,a pair, with. The upgrade transformer comes with 4,8 and 16 ohm taps for easy matching to most speakers. rather than plain old iron. 6c33c Set Schematic It is a very interesting idea to apply 6C33C tubes operating at the utmost level of they set the tubes at 0,6 A at idle so they must use a low supply voltage under. A wide variety of output transformers options are available to you, such as power, audio, and current. Mains transformers. Western Electric 171c Output Transformer For A 124b Tube Amplifier. The traditional output configuration is an output capacitor feeding a step-down transformer to provide lower output impedance. Consider the CCS as infinite impedance but in parallel with the load reflected by the output transformer, so the Rload above is just that reflected by the OPT (about 4200 ohms with 32 ohm HPs). In facts we have the same power supply ripple rejection qualities than in parafeed setup and some will consider the SRPP a parafeed cousin with an active load in place of the cumbersome anode choke. This choke must be large in value, and provides a relatively high impedance at audio frequencies. The question is how do you decide when saturation is going to be a real problem. The Raleigh Audio Line Stage is a state-of-the-art differential vacuum tube gain stage with integral power supply. I'll have to do a little hogging on the mounting holes to get the OPT a bit more away from the tube. Having built two OTL amplifiers before I wanted to avoid the largish output capacitor and planned to build it as Parafeed amplifier. 5 squared, divided by four. Interstage, headphone and line output transformers. Here you see endstage wired as triode, driving output transformer directly. Cheap Output Transformers The output transformer in a valve guitar amplifier is perhaps the most difficult component to obtain if you are building, or to replace in repair, but there may be an answer closer than you think. The parafeed circuit is also a 1930's invention to keep the DC on the output plate of the tube out of the output transformer without using a cap or transformer directly in the signal path, thus allowing for a much smaller transformer. 47uF coupling caps to the output tubes could have been smaller; the -3dB point for the. Found 200 records in Search of Tube DIY Asylum. Because of this difference, single-ended output transformers need to have an air gap to prevent current saturation (a bad thing), but push-pull output transformers do not. I have done a similar amp using 6as7/6080 power tubes and using Talema toroidal mains transformer as OPT for the parafeed, and I find the sound nice.