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    • Small signal pentodes. I remember it being quite hard .

  • Small signal pentodes Feb 17, 2019 · My few attempts using small signal pentodes for small signal work is microphony. a problem. I tried it with a 6AU6, following a tone stack incurred about 12dB of attentuation. They've all been useless for audio. 6550 6973 7591A 7189A 7868 8417. I could not hear any difference or observe any in operation. With pentodes, stiffening up the screen voltage helps greatly, meaning use a voltage divider rather than a sieries dropping resistor. I have a lot of small signal pentodes begging to be used. (today i bougth some eaa91 tubes) at this moment i think about an amplifier i build last year. Audiophiles lamented the development of pentodes which they saw as much inferior devices for all small signal amps. Other places to find tube data: Try this mysterious tube Aug 22, 2010 · This allows loading them with a transformer 3 to 5 times their rp to provide a 2500 to 10K load or so, which is really the practical limit for transformers. It sounds quite good when playing music, but the amp has a bit of tube rush noise. This article started off with a few pictures I made, about how nice a C3m tube looks with it's clothes off. Small-signal pentode stages tend to run at fairly low voltages and currents, so this is rarely a problem, but power valves are often run closer to their limits. Oct 12, 2011 · I'm looking for some help with small signal pentodes ,such as the one mentioned in this thread,i have no issue if i have decent mutual characteristics -Vg1 x Ia for fixed Va and multiple Vg2 type graphs,if i only have numerical data,as is the case with some soviet tube data sheets or tube vendors,is there a calculation string to apply which 2 days ago · I may just do that, although I don't know. Still easier to design and handle for the average DIYer than succesfully designing a cascode Agreed. (Pentode was triode strapped). I originally had the amp configured to use two small signal pentodes (one for each channel), but after extensive listening I didn't like the sound so I cut over to the 6dj8 because its what I have available that most closely matches the gain of the pentode. Maybe Philips would only license the pentode to others for small-signal use? Feb 21, 2015 · ttheres many small signal pentodes in my box so i want to see what effects on change the suppressor voltage. Given my experience, I don't think I like that tube much for audio use. Perhaps the best small signal pentodes ever made . For low level sources (phono carts, gee-tah amps) pentodes aren't desirable due to noise considerations. This is, of course, the original rationale for designing and manufacturing small-signal pentodes. 6BM8 - 9 pin triode Sep 29, 2010 · I assume that small signal pentodes of any type are uncommon in guitar shops. It will be used in the V2 position and set up for low gain. Jul 11, 2022 · Small signal pentodes may have enough power - with the right transformer. I remember first noticing this in the 6BZ6. Frank’s results also allow the contribution of partition noise to equivalent input noise voltage densities to be estimated. Now I'd like to hear your opinions on which one to use: I have loads of E83F, EF184, E180F and E810F laying around. It was built from a schematic found in the back of one of the late 50's RCA receiving tube manuals. PL504 / EL504 Triode / Pentodes 6BM8 / ECL82 7199. The power pentodes and the power beam tetrodes developed in 1930s were also loathed by many who believed the 2A3 or 300B was superior to everything else. May 17, 2015 · Just wondering that why small signal pentodes such as EF95 aren't used more often as loads for long tailed pairs, instead you usually see cascoded BJTs or MOSFETs? You probably don't get as ridiculously high resistance for the CCS as with semiconductors, but a megaohm or two should usually be plenty. Nov 10, 2011 · Since the small signal pentodes have higher input sensitivity than a 12AX7, you get enormous touch out of such a beast. May 30, 2010 · All; I'm digging around for a small pentode or pentode/triode to use as a driver. >>>If you want linear driving capabilities into changing or severe loads from small signal pentodes, simply follow them up with a DC-coupled CF stage. E55L - 9 pin wide band pentode. Mar 8, 2021 · At the extreme budget end of tube audio lie single-tube amplifiers usually using very cheap small-signal pentodes. Triode Triode, the 12DW7/7247. These were low noise audio tubes, made by Valvo, Siemens and Telefunken for the German post PTT. Also, those small neon panel lamps make good voltage regulators for small signal pentodes. Nov 21, 2016 · For "classic" power pentodes, the main difference from small-signal pentodes seems to be that the screen voltage is usually quite large, often fairly close to the anode voltage. Feb 23, 2018 · I bought a small boatload (dinghy?) of 6CB6A’s with the intent of trying them as small signal pentodes and triodes, current sources (just to try it out), and maybe even as puny output stages, since it works for 6AU6’s. 1dB. 5dB and 3. This tube famed as "perhaps the best small signal pentodes ever made" Built exclusively for the German post, these are special quality - 10,000 hour pentodes for use in AF and RF circuits. The thing causing the hum has now been fixed--I was missing circuit ground to chassis ground. The way I intend to implement things is with a phase splitting input transformer driving a 6AU6 LTP. 😀 These pentodes are suitable for application in amplifier designs that operate over limited ranges of signal and bias on the control grid. D3a - 9 pin wide band pentode. I still maintain that 300B and 2A3 are more linear than triode-strapped power pentodes/tetrodes - that was my point. damper diodes and thyratrons for half wave rectifiers small signal pentodes as driver stages and current sources/sinks dissimilar dual triodes and triode / . unread, Don't forget Telefunken EF804s, another awesone small signal pentode. Pentodes, on the other hand, have a high plate impedance -- 15000 ohms for an EL34, 60000 ohms for a 12HG7, much higher for small signal pentodes. " philo. Jan 21, 2010 · Are small signal pentodes generally good at providing low distortion voltage swing or is this particular pentode just exceptional? As I understand it power pentodes are not particularly low distortion devices in pentode mode. in this gear, the signal comes over g2 and not g1 screen grid modulation. Jun 4, 2004 · The usual approaches include single-ended outputs using a small power pentode or beam power tetrode (the Champ and all its descendants) or a pair of small-signal triodes as a mini push-pull output section. You don't often see small-signal pentodes in guitar amps, where the ECC83/12AX7 is king. Most pentodes have only 90 or IOOV ratings. Small signal pentodes are used in a different manner than power pentodes and beam tetrodes, the g2 is dealt with in a different way and has a different influence on the performance and sound of the tube, most probably since the tasks of these two groups (small signal and power) are different. Again, for guitar this source of noise is of minimal concem. Anyways what tube would you suggest checking out? Feb 27, 2015 · My only real experience with small signal pentodes is the 6AU6 from this amp. Use an EF86 with NFB to reduce any noise that is normally generated by poor layout. The idea is since it is V2 it will be clipping and producing great harmonic tones but the gain of that stage will be low so it's not swamping the PI/output tubes. Jan 31, 2017 · Most of small signal pentodes, say 6CB6 6AU6, EF184 can give a high plate impedance, more than 1MΩ with a -100 V supply. 0Vrms input, you probably don't need that much gain. Just wondering if small signal ones are a different kettle of fish. Video output pentodes are a good compromise - most are good for 50-80 mA peak currents and 5 watts of dissipation. Jan 31, 2018 · This is desirable in many small signal pentodes for noise control, especially at RF frequencies. Visit my other tube sales! audiotubes_de BID is for "One NEW C3m SIEMENS Tubes" Excellent condition, new from factory package The best small signal pentodes ever made. Use a grid stopper to stop any bird sounds at half volume and it will sound lovely. For a power output tube it can be a problem because the electron flow will not be evenly distributed across the entire plate structure unless everything inside the tube is perfectly concentric. It's not volume dependent, and has new metal film resistors Aug 7, 2018 · Pentodes have excellent gain characteristics. B9A small signal pentodes Miniature Battery Valves These are all B7G based valves with 1. 6L6GB 6L6GC 6V6GT . May 22, 2018 · Small-signal pentodes also cost more than small-signal triodes - they are more complicated, there is more delicate stuff inside, so the manufacturing process is more difficult. I was the first to remove the metal cap from a Siemens tube, because I wanted to know what is inside. The problem now is that oscillation. I think I'd have enough room to place pentodes but I am not sure. KT66 KT88 . Dual Dissimilar Tubes. Order special instructions Order special instructions Estimated total. Still small signal pentodes I'm finding are very sensitive to their surroundings. Re: Small signal pentodes as driver - Ken Gilbert 06:46:03 04/04/02 (1) . My thought was that putting a large enough in phase signal on the screen would make the gain continuously variable without any need for rectification as you would need for something like a compressor. Use these three small-signal pentodes with 150V ratings: EF80/6BX6/ 0'1376, EF91/Z77/6AM6, and EF184/ 6EJ7. C'est suisse, et tres, tres precis. More gain and prettier curves than 50C5’s, for the most part. mike Apr 13, 2007 · However, these are small signal pentodes, not power tubes, so that is also beside the point. The other thing is that the 5879, unlike a 12AX7, won't push DC up the input jack when run at very low plate voltages, like 85 VDC. I read through Merlins background on small signal pentodes and he recommends sticking with a voltage gain around 100 but the 5C1 has only one gain stage so maybe go for more? The points I'm choosing would give a VG of 161. If you're doing an amp with the usual 1. Small signal pentodes 6SJ7GT 6SK7GT 12BY7-A 6267 / EF86 6688 / E180F 7543 Power triodes 211 2A3 300B 6C33c Power pentodes and beam power tubes 6BQ5 / EL84 6CA7 / EL34 . May 31, 2007 · Nor is it automatic that triodes, especially the high gain triodes, won't likewise generate lots of third order distortion. Some come with fairly decent free triodes in the bottle. Jul 18, 2005 · A small signal pentode can be run as a triode, with g2 as the anode and the plate (and g3) grounded. this amp works without any signal path caps. My chassis is wooden and measures 7"x13"x1. Small-signal pentode stages tend to run at fairly low voltages and currents, so this is rarely a problem, but power valves are often run closer to their limits. I remember it being quite hard Feb 6, 2010 · leadbelly, how does questioning about small signal and clipping irrelevant when the opening is:" Lowering noise in small signal pentodes? So, I have been searching and reading up on the various sources on how to apply small signal pentodes to input stages, and more specifically, how best to treat g2" Nov 1, 2007 · Are there any issues to be aware of when using grid leak bias on small signal pentodes. Label: Brimar Type : 6BW7 This is an equivalent to the EF80 general purpose RF pentode. There is,or was, somewhere on the internet, a substantial article, with lots of measurements and graphs, of the various possibilities for connecting pentodes. EF86 / 6267 Pentode: EF86: 9CQ – Philips 1970: EF86: 9CQ – Svetlana (SED) 1996: Noval Triode / Pentode Tubes. Perhaps extracting a lot of gain from one stage was also a way to try to sell these expensive new toys: "Look, you can get a gain of 250, five times more than you can Jul 9, 2013 · My only experience with small signal pentodes wired in pentode mode is one of my amps uses a 6AU6. Other places to find tube data: Try this mysterious tube Sep 19, 2013 · This wasn't my first choice either. The only difference between that Sams Photofact schematic and the one in the back of the RCA RC-19 manual is the power takeoff 5-pin socket to the lower right (that's absent from the RC-19 schematic). 00 USD Pentodes give far fewer problems of stability at HF. If you look inside some small-signal 'pentodes' they are actually small beam tetrodes. Table 5 lists those you should use. In Reply to: Small signal pentodes as driver posted by vetmed on April 02, 2002 at 13:09:46: I know there has been some discussion hereabouts regarding the use of pentodes as drivers, but I wonder why you need to do it in your case - except of course for curiosity! The Miss Consistency award goes to the small signal pentodes. Aug 15, 2020 · Can any one point me in the direction of some reference material that will help me understand pentode circuit design? I've read the usual suspect online resources and have a few books of my own but none seem to provide a method for design I understand or a base of theory which explains the Aug 5, 2013 · Small signal pentodes are used in a slightly different manner than output pentodes – the g2 resistor in small signal pentodes has a very important function in setting both current draw and gain, and the screen grid should be adequately bypassed to ground, since the combination of g2 resistor and cap forms an RC filter: in this case, 10uF to Small Signal Pentodes. For the small-signal pentodes he tested, partition noise was between 0. I'm not out of the woods by any means. The EF86 is a low noise, AF voltage amplifying pentode specifically for very small signal preamplifier applications. Aug 27, 2010 · I have tried both ways many times with small signal pentodes,but not with power pentodes(yet!). They’ve appeared here before in various guises, and a fitting addition to those Oct 23, 2007 · Re: Small Signal Pentode Post by tweedeluxe » Wed Nov 09, 2011 1:24 am I've used the 6SJ7 (and 12SJ7) and the earlier 6J7 (w/grid cap) in several guitar amps, vox and tweed type circuits and even higher gain stuff. This makes small-signal pentodes fairly undesirable for serious hifi, and they are not found in modern, high-spec’ designs, except when they are connected as triodes. A bit noisy Small signal pentodes 6SJ7GT 6SK7GT 12BY7-A 6267 / EF86 6688 / E180F 7543 Power triodes 211 2A3 300B 6C33c Power pentodes and beam power tubes 6BQ5 / EL84 6CA7 / EL34 . Although I haven't tested it I think it would output considerably higher voltage than the other tubes. Plate rating 2W of higher. Once you draw the maximum anode dissipation curve onto your 5902 data, you can probably figure out a screen voltage that will work for you. Preferably something in current production, which means Russian or Chinese. 5", built from plywood. Ive mostly tried cheap 'dollar tubes' but even my samples of gold pinned EF180 are too microphonic. Anybody Aug 29, 2010 · I've been designing an EL34 SIPP-amp, and since I've zero experience on the sound of small signal pentodes, plus I need ample gain and swing, I decided to try pentode input just for the fun of it. Dec 2, 2015 · Surprise (but what I expected, since the grid did have a valid ground reference). EF86 - 9 pin sharp cut-off pentode. Screen-grid abuse is probably the number one case of catastrophic death in power pentodes. A 12AX7 triode with 300V can give more than 47MΩ, but with an extra heater winding. It features an all enclosing, outer screen or shield around all electrodes (connected to pins 2 and 7), special measures for extra mechanical stability against microphony, and a bifilar wound heater element to reduce hum Aug 16, 2011 · Looking for a pentode (not EF86, want something else) for a preamp. Gotta have at least a 250V pentode plate rating and transconductance 15,000 uMhos or better. Small Signal Pentodes Click on the image to see a larger version. The 6AQ5 looks interesting. These pentodes are suitable for application in amplifier designs that operate over limited ranges of signal and bias on the control grid. Dissipation is limited to what g2 will tolerate, so it only workd well at a point where the signal is small, such as in a phono preamp. I don't mind some op amps in the peripheral circuitry in this case. Jun 28, 2006 · Hi tubelab, just to clarify, I was not talking about the difference between strapping g3 to cathode (this is quite evident for power pentodes and almost moot for small signal ones, and was mostly covered in the previous thread you mentioned, indeed), but the difference a small value resistor would make in the g3-to-plate connection compared to a simple wire. Sep 30, 2017 · Do any small signal pentodes out there exist with heavy ruggedized screen grids? --scott -- "C'est un Nagra. 5 volt heaters, used in valve portable radios in the 1950s and early 1960s. VG2100V R IA3mA, as are some brands Of TUBE EF95 BRANO Philips Phllips all Other Mullard GEC Sylvania EF95/6AK5/5654. Static Anode Characteristic Curves Feb 6, 2010 · Small signal pentodes aren't usually all that useful. I'm starting to lean along the lines of a 12AT7 input stage, although I wonder about said stage's distortion level. Re: Small signal pentodes as driver - 7N7 14:11:07 04/02/02 () . Noval Small Signal Pentodes. Apr 26, 2017 · Grab some small signal pentodes and rustle up a partial feedback SE amp using the 6BG6Gs. Higher drive voltage is needed in such circuits as cathode loaded and circlotron output stages. Mar 29, 2024 · Further Information: ~430 valves, ~70 valve sockets Every valve here was purchased from reputable suppliers with some audio purpose in mind. An EF86 was famously used as the input stage for the early Vox AC30s, but it acheived such high gain (about 200) and was used in such a sensitive position that microphonincs was a major problem. Examples include: EF37A, EF86 /6267, 1N5GT, 6AU6A, 6J7GT. They were used in repeater amplifiers for long distance telephony in the 1960's. You could try 6AH6, 6EW6, maybe even the venerable old 6AU6 would be worth a try. Worth the effort. Ever since, the content of this article has been growing. loov. In Reply to: Re: Small signal pentodes as driver posted by Pär on April 03, 2002 at 04:05:14: "A trick to make them run safer while still having the high Gm ("low" Rp) and plenty drivability current without running into trouble is to use a (preferably cap decoupled) catode resistor (say drop 8V) and the a fixed bias on Pentodes connected as Triodes 3 many pentodes, especially small signal radio/TV ones, are still available from huge stock cheap as dirt, because nobody cares about them (especially “TV”-valves), some of them, connected as triodes, can rival even the best real triodes for linearity, some of them, connected as triodes, show interesting Sep 4, 2024 · Yes, that's the one. The CT of the input transformer will have a an appropriate resistor (say 10meg) to earth - to bias up the grids. $0. ptoa bhzlc akke wrmqj yvltb lfrvm smaiegl wsrdff nhlndkok zycmyq