| phn |
This just hit me. I knew of their existence. I just never cared about them. I don't really care about them now, either. But I thought it could be fun to ask. I googled and searched here for "7-pin." I didn't come up with any relevant hits. (From Google I learned that lots of dealers carry 7-pin sockets.) I'm sure this has been here. But since I don't know which, if any, 7-pin tubes are popular, or even used, I don't know what to search for.
I looked into these tiny tubes and they seem to have specs similar to those of "space-age" novals. They look pretty impressive. Some are designed for VHF, some for audio. They also have relatively low maximum voltage rating. I don't know if the latter is good or bad.
Anyway, has anyone here had any experience with these? |
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| wfmali |
EL95 - fine tube, runs pretty hot, though. AB with 10k Raa in UL43% should give you about 7W. They are on my radar screen as well.
Marcus |
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| frank754 |
Well, taking a look at an old RCA tube manual will give some hints.
The 6AV6 is the exact equivalent of 1/2 a 12AX7, and can be used this way, in spite of it having 2 tiny diode plates (which can safely be ignored). These diode plates were used in the 12AV6 version of "all-american 5" radios as the detector & AVC.
Other than that, I've seen circuits using the 6AQ5A (pentode power tube), 6AU6A,
6C4 (half of a 12AU7), the 6CB6A in some voltage regulators,
6J6A,
the 6X4 (power supplies), etc.
In a lot of old Scott hi-fi equipment you'll see tubes like the 6AU6, 6X4, and 6BQ7A (the latter is actually a 9 pin). |
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| Poindexter |
I'll check in. I've just started looking at them, and the progress so far is:
I have a power amp that uses a singly-driven diff-amp to drive a pair of (various) outputs in PP. Some guys here are aware of it:
http://www.audiotropic.net/Projects/machine1.html
Until recently, I used the 5965 / 7062 / E180CC for the input tube(s), because it has the best gain with the lowest RP I could find, making it suitable for this service almost uniquely. There are complications. It's a computer tube, and so not fabulously linear (varies by brand, some are not so bad), and since it's only really specced at full on saturation and cutoff, they tend to be somewhat wayward in between. Especially in regard to the two devices in the single bottle. Since I'm using them as a diff-amp, I need pretty close matching between sections, a requirement that is currently putting about 60% of my tubes in the circular file.
A few months ago, I went looking for a replacement, and one of the criteria was that it had to be a single triode, to get around the sections-in-an-envelope predicament. I came upon a bunch of the 7-pin minis you have been looking at (I bet), all called 'VHF amplifiers'. I went researching with the vendors, and came upon a poster girl.
The 6GK5. There are half a dozen near equivalents, but they all have the same chars; two thirds the rp of the 5965, and more than twice the gm, and so a mu of ~65, instead of ~45. Plus, of course, they completely sidestep the section matching problem. The kicker? They're widely available in bulk nests (look on eBay) for $250/hundred (Mullard) or $150/hundred (Hitachi). The vendors will kiss you where the sun don't shine, you take a C of these things off their hands, I have several hundred; thus I divulge.
I now have a breadboard 6V6 amp up with these, and it sounds noticeably better than the 5965 version. I'm gonna keep my 5965s for past client servicing, and these little darlin's are going in ALL the future amps.
Was that an okay report?
Aloha,
Poinz |
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| frank754 |
Actually, you can design a good amp, using the 6X4 (full wave rectifier) for the power supply, a few pairs of 6AV6's (or others), and 6AQ5A's for the output stage. The 6AQ5's are actually touted as having the same characteristics as the 6V6's, providing you keep and eye on the max voltage (etc) specs and don't push them too hard.
So an all 7-pin amp should be fairly easy to set up, and very close, component wise to combo 9 pin/octal designs, at least in the 10-12 watt or so push-pull designs. You'll just need a few more tubes, as most are not dual-element. |
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| ray_moth |
| 6AU6 (or 6AU6A) is quite often used in audio, either as a pentode voltage amplifier or as a CCS. It can also perform very well strapped as a triode. |
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| rdf |
| 9002 triode, the 7-pin equivalent of a 955 acorn. Dirt cheap, nicely linear CCS loaded. |
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| mach1 |
I'll second the 9002 and add the 8532.
pm |
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| phn |
Yeah, it was the low Rp, high mu tubes, like the EC900, that caught my attention. They aren't quite the Western Electric 417A and 437A. But an Rp of 7-8k and mu of 70-80 isn't too shabby. Tube matching could be a problem, I guess. Though not as severe as the 437A.
Edit: Error correction. |
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| Eli Duttman |
| The 6AV6 (1/2 a 'X7) has already been mentioned. The 6AB4 is 1/2 a 'T7. |
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| soundbrigade |
Rectifier 6X4.
I am about to build a tiny 6AQ5/EL95PP wich is said to be a littlebrother to 6AQ5/EL84.
I have a bunch of 7-pin pentodes for "painful STC-experiments".
What I don't like is the small 7-pin socket, but on the other hand I go for these kind of tubes because of the size - less is more. |
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| Eli Duttman |
| quote: | Originally posted by soundbrigade
Rectifier 6X4.
I am about to build a tiny 6AQ5/EL95PP wich is said to be a littlebrother to 6AQ5/EL84.
I have a bunch of 7-pin pentodes for "painful STC-experiments".
What I don't like is the small 7-pin socket, but on the other hand I go for these kind of tubes because of the size - less is more. |
Magnus,
EL84 = 6BQ5 EL90 = 6AQ5 EL95 = 6DL5
The 70 mA. a 6X4/EZ90 yields is certainly enough for a monoblock PP 6DL5 amp. Use 2 with paralleled plates for a stereoblock.
BTW, you could build an all 7 pin "El Cheapo". Matching up pairs of 6AB4s for the splitter/driver is a way. A 2nd way is 6J6/ECC91 as the splitter/driver mated to a line stage with gain. |
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| Runco990 |
Speaking of small tubes, has anyone looked at this: http://www.impamp.com/
Interesting.... I'd love to play with one, but too steep for me. I have some very tiny tubes in my geiger counter, but never thought of audio.
Marc |
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| Klimon |
They claim "10-20KHz +0/-2dB"; is this anywhere near possible with that miniature size opts, even with truckloads of gNFB??
Simon |
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| Runco990 |
I'm also wondering about the speaker demo. Is it even possible to get that low an oscillation through an OPT??
Marc |
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| rdf |
| I have, but it was a Hammond 1628SE. Each tranny probably weighs as much a three iMPAMPs. |
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| soundbrigade |
I wanted to test this variation for 6AQ5: Cathode-coupled Paraphase
BTW - I always forget but there is a sort of EL84/6BQ5 with top anode and that is sturdier built than a "normal" EL84. I think it was a 7-pin tube but I may be wrong. |
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| aletheian |
| quote: | Originally posted by ray_moth
6AU6 (or 6AU6A) is quite often used in audio, either as a pentode voltage amplifier or as a CCS. It can also perform very well strapped as a triode. |
Yes, they are plentiful as dirt and work well in a lot of applications... one of my favs. One trick that I picked up on this board... i THINK from you ray_moth... ground the plate so that it acts as a sheild, and run it in triode mode with G2 as the plate. I have tried it with a few 6au6 and it works great. I don't know if there are any caveats to running it this way, but it seems to work alltogether better than regular triode mode. |
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| soundbrigade |
| To aletheian: how about it's parameters when doing like that?? A pentode is often used (trioded) as they have better gain. |
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| DSP_Geek |
| quote: | Originally posted by Klimon
They claim "10-20KHz +0/-2dB"; is this anywhere near possible with that miniature size opts, even with truckloads of gNFB?? |
Sure, it only has 1 watt output per channel. Look at Hammond type 125ASE in http://www.hammondmfg.com/125SE.htm - at 3 watts it's not much bigger than the transformers shown in the picture. |
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| aletheian |
HEY THAT"S HET ONE! Good catch! |
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| Zen Mod |
EC900 is mentioned
PC900 must be even cheaper everywhere |
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| ray_moth |
The caveats for running a 6AU6 as a triode with grounded plate and grid 2 acting as the sole anode are:
1. Don't exceed the maximum grid 2 dissipation of 650 mw, and
2. Only use it with small signals, e.g. in a preamp, to avoid poor linearity.
I used it successfully like this in a preamp stage following a James-type tone stack, which has an attenuation factor of 12dB, thus the signal was very small. |
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| poynton |
| quote: | Originally posted by Runco990
Speaking of small tubes, has anyone looked at this: http://www.impamp.com/
|
Any idea what tubes are used. ?
I think 6021 from the video but for output??
Wire-ended pentodes ? [type numbers ?]
Andy |
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| Eusebius |
| I'll recommend the 3A5 - cheapest good sounding DHT, and a double at that. I bought 100 really cheap - they're slightly bright but very detailed and have that genuine DHT sound. You need a good filament supply as always with DHTs. I use them in diff pairs to reduce mcrophonics, and put a couple of cheap plumbers rubber rings on each. Definitely one to try out for peanuts, since the really good DHTs are getting scarce and going up in price. |
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| Runco990 |
| quote: | Originally posted by poynton
Any idea what tubes are used. ?
I think 6021 from the video but for output??
Wire-ended pentodes ? [type numbers ?]
Andy |
It's a philips 6021 dual triode tube. If you click on the main pic, you'll get to a few videos that explain the amp and the tubes.
Marc |
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| andrew_whitham |
the problem with this thread is that you worry may be you havent got enough before the prices go north...
or is that me?
letting the cat out what about the ec91? this will, at the moment, be my input stage. Unless its the 6AT6 :)
and If I might be a little bold I didnt think the 6AU7 was that special from the plate curves. Am I missing something? - The triode curves are the first place I look no-matter-what If they arent evenly spaced then :dead: And it didn't make my list.
should we (I) consider other factors? but for me if there's not good intrinsic linearity then consider something else. this is why the *sn7 are so well regarded, and the 300B (OK I have to admit it curves nice...)
Andy |
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| aletheian |
| quote: | Originally posted by poynton
Any idea what tubes are used. ?
I think 6021 from the video but for output??
Wire-ended pentodes ? [type numbers ?]
Andy |
I think there is a lengthy thread on this board somewhere... and the inventor even pops his head in to add some info. |
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| Klimon |
| quote: | | Sure, it only has 1 watt output per channel. Look at Hammond type 125ASE in http://www.hammondmfg.com/125SE.htm - at 3 watts it's not much bigger than the transformers shown in the picture. |
True but the hammond is only spec'd for 100hz -1db
Simon |
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| DSP_Geek |
| quote: | Originally posted by Klimon
True but the hammond is only spec'd for 100hz -1db
|
That's outside the negative feedback loop. Closing the loop will bring that down an octave or two. |
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| Poindexter |
NFB is poison. Besides, now we're down 1dB at 25Hz. Big deal.
I have iron on my bench right now that is down less than 1dB (ref 1KHz) at less than 10Hz. These from Mikey (MQ), and my Thai pal Kittipol at SACThailand.
C'mon, guys, we're supposed to be pushing the envelope here, not promoting mediocricity. Everybody here has already seen mediocracy.
I lurk here to get eddjakated. C'mon,eddjakate me.
Aloha,
Poinz |
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| DSP_Geek |
| quote: | Originally posted by Poindexter
NFB is poison. Besides, now we're down 1dB at 25Hz. Big deal.
I have iron on my bench right now that is down less than 1dB (ref 1KHz) at less than 10Hz. These from Mikey (MQ), and my Thai pal Kittipol at SACThailand.
C'mon, guys, we're supposed to be pushing the envelope here, not promoting mediocricity. Everybody here has already seen mediocracy. |
*shrug* I'm just pointing out the transformers on the impamp aren't unreasonably small by comparing them with existing stock.
Besides, I have a few envelope-expanders in construction here, but I won't mention them until such time as they're ready for public consumption. Suffice it to say prototype tests are not unpromising, although the cats run and hide when I crank up some full power runs. |
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| phn |
You don't eddjakate people by talking about 10Hz, -1db and no NFB SET in the same sentence. With minimal Miller capacitance and impedance you should be very happy if you get 20Hz, -1db.
Who says the tiny thing does not use feedback? |
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| Poindexter |
Sorry about the tone of that post; it came out a lot harsher than I thought. I thought we were going to be talking about cool undiscovered devices, but it seems to have wandered a bit.
Another one I'm looking at right now is the 6T4, a lowish mu single triode. I want to replace the 6AQ5 in the preamp with it (or something) if possible because I have to select the power tubes so carefully for microphonics in the low signal application. The 6T4 has chars very much like the 6AQ5 (rp=2K, S=5.5, mu=11), only it's a lower power device (3.5W), uses a lot less heater, is about half the physical size (which is sort of a marketing disadvantage, actually), and they turn out to be pretty much completely unmicrophonic.
All is not completely well in duckburg, in the breadboard they're okay but not great, a little creamy and bland. I'll be fooling with the OP and load, maybe they'll wake up. Available; Jack was glad to scare me up a hundred RCAs from his stash, cheap.
Further research seems indicated, doesn't it always?
Aloha,
Poinz |
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| aletheian |
| quote: | Originally posted by DSP_Geek
*shrug* I'm just pointing out the transformers on the impamp aren't unreasonably small by comparing them with existing stock. |
I am fairly sure that they use a 15W Fender guitar amp output transformer. |
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| aletheian |
| quote: | Originally posted by phn
You don't eddjakate people by talking about 10Hz, -1db and no NFB SET in the same sentence. With minimal Miller capacitance and impedance you should be very happy if you get 20Hz, -1db.
Who says the tiny thing does not use feedback? |
"...there are no capacitors in the audio path (all DC-coupled) except two tiny ones in the negative feedback loop of the input to deter RF oscillation -- Zachary Vex" |
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| Poindexter |
The Machine isn't SET, but it's all triode, zero NFB, and takes a pretty high load on the outputs as well, 8-10K. Last one I made for a client had 10K Silk outputs and 0.33uF Mundorf Silver/Oils, and was down 1dB at 10Hz and 39KHz.
Since the grid circuit resistors on the outputs are 100K, this will define the -3dB point of delivery of signal to the outputs at 4.7Hz, so who knows where the inductance of the OT actually falls off? Now, these are PP trannies, and presumably very lightly gapped if at all, but it certainly points out the doability of the solution.
That guy sure has a cool thing in that handfull of amp though, if it sounds like anything at all.
Aloha,
Poinz |
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| aletheian |
| quote: | Originally posted by Poindexter
The Machine isn't SET, but it's all triode, zero NFB, and takes a pretty high load on the outputs as well, 8-10K. Last one I made for a client had 10K Silk outputs and 0.33uF Mundorf Silver/Oils, and was down 1dB at 10Hz and 39KHz. |
WHOA! Not to thread-jack, but 5965? interesting choice. i have only seen them DIY-ed in studio compressors and whatnot because of the cutoff charactaristic. I have always wanted to tinker with remote cutoff triodes at bend the transfer function a bit to see what kind of interesting harmonic spectrum I could milk from it... |
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| jean-paul |
Just saw this thread. I want to get rid of my stock of NOS/NIB 6AQ5. They're french army types of the Cifte brand and/or RTT. New in box, made in the sixties. I also have some Sylvania 8532W left.
If someone is interested make me an offer per PM.
Sorry for spamming ! :cannotbe: |
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| Poindexter |
Aletheian, the 5965 is not specced as a remote cutoff device. It's a computer tube, and so the specs are pretty loose. Some are very nonlinear, having a sort-of remote cutoff characteristic, and some are better. I used it at the time because it was the only (or only available) duotriode that had a high enough gm and low enough rp to do the job here, the constraint being the rather low grid circuit resistance rating of the 6V6 when negative-supply biased. Andy Evans in Blighty did some taste tests on various types; he ended up liking the pinch-waist Mullards best, I never found any. Best I found was RCA three-mica 5965, followed by RCA two-mica and orange-label Amperex 7062, then white-label Mullard / Amperex / Philips E180CC.
A lot of the nonlinearity of this tube type is 2nd order, and it's being used here in a diff-amp, which nulls most of this out. They can actually sound very good, but they got 'discovered', they're getting harder to find, and getting good pairs and quads is a bear because they test so scattery.
I think this may be a problem in adapting all sorts of oscillators (6T4), VHF amps (6GK5), sweep and pass tubes, all of that stuff, for audio. It isn't that they're categorically bad, but a lot of things like microphonicity, noise, linearity, tight specs, just weren't cared about, so you takes your chances. For me so far, the 6GK is a definite winner, the jury is still out on the 6T4.
Aloha,
Poinz |
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| aletheian |
| Ah... you are right... not at all the tube that I was thinking of. i should check the data sheets before i post HA! |
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| Eli Duttman |
| quote: | | A lot of the nonlinearity of this tube type is 2nd order |
That works to advantage in a PP amp, where even order distortion products from the "finals" are cancelled. Look at the NET distortion spectrum. Jim McShane correctly points out that a "waterfall" net HD spectrum is desireable. The 12AT7/ECC81 is skewed even more towards 2nd order HD than the 5965 and it sounds damned good as a differential splitter. Don't put a 'T7 in a SE amp. YUCK! |
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| aletheian |
| quote: | Originally posted by Eli Duttman
That works to advantage in a PP amp, where even order distortion products from the "finals" are cancelled. Look at the NET distortion spectrum. Jim McShane correctly points out that a "waterfall" net HD spectrum is desireable. The 12AT7/ECC81 is skewed even more towards 2nd order HD than the 5965 and it sounds damned good as a differential splitter. Don't put a 'T7 in a SE amp. YUCK! |
Good call. I am experimenting right now with a 12at7 LTPI/CCS DC coupled into a PP el84 A1 output. On paper and on a sim it looks good. I wanted to try it since i rarely use 'AT7 since it has been easier for me to get better sound out of more exotic tubes. |
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| Miles Prower |
| quote: | Originally posted by Poindexter
NFB is poison. Besides, now we're down 1dB at 25Hz. Big deal. |
| quote: | | C'mon, guys, we're supposed to be pushing the envelope here, not promoting mediocricity. Everybody here has already seen mediocracy. |
Just because there are all too many yutzes out there doing poor open loop designs and hiding their mistakes behind enormous amounts of gNFB does not mean that it's "poison", just misused and abused.
NFB (local and global) is essential to get good performance from any SS amp, and from pentodes. I've done both, and NFB certainly helps improve the sound considerably, but only if you don't overdo it. The judicious use of NFB will make a good sounding SET sound even better. Furthermore NFB also helps in making performance less dependent on each component.
| quote: |
I lurk here to get eddjakated. C'mon,eddjakate me.
Aloha,
Poinz |
I just did. :D
The question is: will you learn from it? |
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| Dave Cigna |
| quote: | Originally posted by Miles Prower
The judicious use of NFB will make a good sounding SET sound even better. |
My suggestion to anyone (everyone) is to build an amp that you know will perform well without NFB, then go ahead and experiment by adding a little at a time to see if it improves the sound to your ears.
I think it really is a subjective thing, depends a lot on the rest of your system and you're listening habits. You might find a little helps tighten things up a bit. You might find more brings fun and dynamics. Then go back and try none at all again to see what it cost you ...
-- Dave |
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| Eli Duttman |
| quote: | | My suggestion to anyone (everyone) is to build an amp that you know will perform well without NFB, then go ahead and experiment by adding a little at a time to see if it improves the sound to your ears. |
GOOD ADVICE! NFB is tool, not a crutch. To get good results, the circuit must be reasonably linear open loop. Watch the phase shifts. A max. of 2 caps. can be in loop's signal path and only 1 is safer. Phase shift oscillators are something all of us can do without. :( |
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| jerluwoo |
| Just my 2 cents but I've found the small 6J6 tubes to sound excellent. They also have a rather low plate resistence so it doesnt take a large amount of voltage to get a good bias current. |
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| w5jag |
| quote: | [i]
BTW - I always forget but there is a sort of EL84/6BQ5 with top anode and that is sturdier built than a "normal" EL84. I think it was a 7-pin tube but I may be wrong. [/B] |
7757 is probably what you are thinking of. It is a plate cap variant of 6094 which is an ultra rugged 6AQ5/6005. IIRC, 6094 and 7757 are 9 pin. 6AQ5/6005 is a 7 pin tube. |
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| Poindexter |
w5jag, where you come up with this obscure toob stoof? For me, plate caps put me in liability land, but that's a great data point.
jerluwoo, thanx for the 6J6 reference. I'm talking to my vendor right now about a C of them ($1.50/ea at that buy). It's a dedicated diff-amp device, but that's me!
Aloha,
Poinz |
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| ray_moth |
| It's sometimes necessary to 'tune' the amount of NFB you need based on the behavior of your speakers. Too little NFB can give woolly bass, esp. with pentodes, while too much can sound a bit dead. |
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| Poindexter |
jerluwoo, what kind of 6J6s you like? My guy has RCA, GE, Sylvania in inventories big enough to get good matching. Usually I would just try RCA first, since they're almost always good, but I wonder if you (or anybody else around here) has a read on which ones are the luxe.
Cool device, by the way; just the sort of thing I was hoping to find in this thread. The single cathode limits possible applications, of course, but I want to make a diff-amp out of them anyway. so hey!
Mahalo,
Poinz |
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| soundbrigade |
Aittle late but anyway ...
Throw in a few pics of a 6AQ5-PP amp I finished today. The tubes look peculiar - slim and very high.
 |
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| phn |
| A note of warning. Beware that many of these 7-pin tubes seem to clip at around 1V p-p. Most novals seem to handle twice that, with the likes of the 12B4 being able to handle much higher input voltage. |
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| frank754 |
| Very nice looking result, the little tubes can do a good job and save space as well. |
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| jerluwoo |
| The 6j6s i have are rebadged to eico meant as replacements for oscilliscopes. Had about ten of them so i havnt tried any other brands. I posted a scematic of a very good sounding little hybrid amp here in the tubes section using them. Good little tubes i think. I found only 1 out of the ten that was microphonic. |
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| Ciscokid |
Hi,
Just found this thread! I built this 6AU6==>6AQ5 SE amp a couple years ago using OPTs and other parts from an old Sony R2R. I use it at work with eMac IPOD :) Very nice sounding.
Regards,
dg |
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| soundbrigade |
SE: Liten men fin
DE: Klein aber fein
EN: Small but beautiful |
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| poynton |
| quote: | Originally posted by Ciscokid
Hi,
Just found this thread! I built this 6AU6==>6AQ5 SE amp a couple years ago using OPTs and other parts from an old Sony R2R. I use it at work with eMac IPOD :) Very nice sounding.
Regards,
dg |
It looks good on the outside. What's it like on the inside?
Andy |
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| Poindexter |
Here's the P O C breadboard of the Machine, with the 5965s replaced by 6GK5s
There's no goin' back; the 6GK5 has 60% more gain, 30% more drive (lower rp), no section-matching predicament, and sounds noticeably better than the 5965. More spacious, more juicy, more see-through.
Hau'oli i Maui,
Poinz |
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| Ciscokid |
| quote: | Originally posted by poynton
It looks good on the outside. What's it like on the inside?
Andy |
Hey Andy, Thanks for the complement! Here is a link to some early construction photos! I really need to bring the amp home and shoot a few more completed (relative :) ) pictures.
My 6AQ5 amp.
Hope this helps!
dg |
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| mach1 |
| quote: | | There's no goin' back; the 6GK5 has 60% more gain, 30% more drive (lower rp), no section-matching predicament, and sounds noticeably better than the 5965. More spacious, more juicy, more see-through. |
Poinz,
Where are you running them ?
pm |
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| Poindexter |
Hundred volts, 4mA. Constraints of the resistive plate loading. I'd like to go up to 4.5mA, but then the voltage is so low I might get unacceptable distortion on max swing.
Interesting thing; I load the common tail with the IXYS chip CCS to minimize heat inside the chassis. It works a treat (very quiet, and dynamic resistance of the tail up in the hundreds of kilohms), and with a serendipitous side effect; I can reach into the space between the OTs and adjust the OP of the front end with the twist of a screwdriver on the pot. Less current, sound a little brighter. More current, sound fuller. At least in this situation. In the EL34 amp, I'll have another hundred volts of PS to work with, and so can explore this further. So far though, very succesful breadboard; I can't go back to the old amp, the sound is just too, um, opaque.
Aloha,
Poinz |
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| mach1 |
| quote: | | Hundred volts, 4mA. Constraints of the resistive plate loading. I'd like to go up to 4.5mA, but then the voltage is so low I might get unacceptable distortion on max swing. |
Looking at the plate curves, it seems you are using plate resistors around 47k. Personally, I would have been tempted to go for something a lot lower (say 22k) and shoot for around 110Vp at 7.5mA, letting any additional H2 cancel. Ri is around 7K2 here, so 22k Rp appears ok.
You have got me tempted to break out my stash of 4GK5s and start breadboarding LTPs. I currently use them as the second tube in my phono amp, where they work well in a grid leak config fed by a 2.5mA CCS.
BTW: your breadboards are better finished than my amps.
pm |
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| unclejed613 |
| found a full carton (24 or so) ck5073 triodes at a milsurp store, dirt cheap. these are submini tubes about 1.5 inch L x 0.3 inch dia. electronics guy at the milsurp store said they have more cartons of them in the attic. looks like it would make a nice project, such as a guitar preamp or tube fuzz......... also saw a radiosonde module using 5073's as a UHF oscillator and RF amp..... downloaded the spec sheet on them, and they have very low Cgp (1.2pf). i plan on assembling a tube op amp with them to test with.... |
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| Wavebourn |
I have a bunch of 12at6 tubes:
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| piffpaff |
| quote: | Originally posted by Eli Duttman
GOOD ADVICE! NFB is tool, not a crutch. To get good results, the circuit must be reasonably linear open loop. Watch the phase shifts. A max. of 2 caps. can be in loop's signal path and only 1 is safer. Phase shift oscillators are something all of us can do without. :( |
What do you people think about the negative feedback in this circuit (using the 6AU6)?
http://www.tuberadios.com/temp/headphone1.jpg
From this thread:
http://www.diyaudio.com/forums/show...?postid=1169738 |
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| Eli Duttman |
A response is in the linked thread.
Let's hold thread-jacking down. |
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| kuroguy |
| quote: | Originally posted by Ciscokid
Hey Andy, Thanks for the complement! Here is a link to some early construction photos! I really need to bring the amp home and shoot a few more completed (relative :) ) pictures.
My 6AQ5 amp.
Hope this helps!
dg |
You got a schematic for that amp? |
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| Ciscokid |
Hi,
My site lists two circuits (click on the amp), one using Hashimoto iron and the other circuit from an old RadioTronics article. I believe I followed the older article and omited the tone control and NFB circuit. Not 100%, I would have to open it up and see exactly what I did.. However, I must say this is a very sweet sounding amp I use in the office.
Kind regards,
Danny
My Site |
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| kuroguy |
| Here's a view of the amp I'm building. Anything look familiar? I used the chassis from an old Intel Network Attached Storage. This amp is entirely from salvage parts. |
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| Ciscokid |
Very nice! I still have my meters. How do/did you plan on hooking them into the circuit? Any shots of the underside?
Regards,
Danny |
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| kuroguy |
| It isn't wired yet, but I'm using the output trannies from the recorder. I plan to wire them to the 600 ohm outputs with 10K pots as voltage dividers and a 100K pot in series just like it was in the recorder schematic. |
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| Ciscokid |
Cool! I am using the 8 ohm for speakers and had thought about using the 600 ohm connections for driving a sub but have not hooked it up as of yet. Keep us posted of your progress..
Thanks,
ck |
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| 7N7 |
An excellent 7-pin valve is GEC's A2134.
A 9W pentode with good gm, it makes a super driver when triode-strapped and indeed might make an interesting small p-p amplifier. Usually found as CV2179 and (I think) CV 4062.
Why two CV numbers? All CV 4xxx types are ruggedised for the military.
7N7 |
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| sam8888ysl |
I ever built 2 6AQ5 PP AMP for my friends
only 2 6J6 and 4 6AQ5
P out= 10W+ 10W
sounds quite well |
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| sam8888ysl |
6J6 5844 is a quite well and cheap tube
low plate resiste, mod mu
u can pall them works like 5842 |
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| Graeme |
Hi,
Re 7N7's comments re A2134 ~
An excellent tube with the classical oval-anode structure. This is perhaps more available as the N78 or CV2179. Data via Franks site is astonishing - a PP pair as triodes can achieve 6 watts output when provided with HT of 350v - that's better than EL84s and lower distortion too. (See MJ -III - page 395) Generally GEC branded, but I have examples branded- Mullard.
EF91 - RF pentode, sharp-cut-off, high conductance. (Seek labels as 6AM6, 6064, M8083, CV4014....located by sleuthing Avionic-repair depots. Provides a useful triode-connection with mu around 70......
M8082. (CV4063) A darling oval-anode SQ output pentode by Mullard. In 6AU6-size glass and a Pa figure of 4.75 watt. Curves via Franks site reveal a very linear triode connection with a mu ~ 12. There's been many an application running through my mind - pre and line-amp output stages, differential driver stages, and even a sardine-can sized power amplifier.....Yes, I scored heavily at the same Avionic repair shop..........
Poinz.....
You're breaking my heart!! I have just bought all these 7062/E180CC tubes and here you are galloping off in another direction. I am still sticking with the 7236 for the output tube, despite the increased drive swing....no thread-break intended.
Regards,
Graeme |
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| 7N7 |
| quote: | Originally posted by Graeme
Hi,
Re 7N7's comments re A2134 ~
An excellent tube with the classical oval-anode structure. This is perhaps more available as the N78 or CV2179. Data via Franks site is astonishing - a PP pair as triodes can achieve 6 watts output when provided with HT of 350v - that's better than EL84s and lower distortion too. (See MJ -III - page 395) Generally GEC branded, but I have examples branded- Mullard.
[...]
Graeme |
Graeme,
N78 is not the same valve as A2134; A2134 is rated at a higher voltage.
See A2134 and N78
7N7 |
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| Graeme |
7N7,
Sorry about that!!
The Marconi data sheets are confusing. Sheet for A2134 states this is commercial equivalent to CV2179. Visually, construction appears identical to the N78.......
Confusion abounds - you say the A2134 enjoys a higher voltage to that for the N78 - yet triode curves for the former are provided to 300v, whilst for the latter they are provided to 500v....Bias values are very different - the N78 figures are significantly lower.
Both very interesting tubes nevertheless.
Regards,
Graeme |
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| 7N7 |
Yes Graeme,
I know what you mean; it has been said to me that G.E.C. were not unknown for being a little "economical with the actualité "!
And it is not unusual to see makers' curves extending to absurd voltages and currents!
I used to have quite a lot of CV2179s and 4062s. At that time too, I had an AVO 163 valve tester and they all tested very well.
As I said before, as triodes they make excellent drivers for large valves; for a while I drove a pair of triode-strapped 813s with them, whilst at the same time using another as a line-stage.
Versatile!
7N7 |
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| kuroguy |
| quote: | Originally posted by Ciscokid
Very nice! I still have my meters. How do/did you plan on hooking them into the circuit? Any shots of the underside?
Regards,
Danny |
Here's one with the tubes and panel lit up and one of the underside. Not completely wired, but got the filaments and pilot lights and most of the wiring from the secondaries of the output transformers to the terminals. |
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| kuroguy |
| the other picture |
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| Ciscokid |
Ohhh.. All that room :)
Also, I noticed that you are using the original POT. I did the same thing at first but found the unit to be defective. I tried cleaning and that helped some but the sound would degrade after a little bit of use so I replaced with a 100k from my parts box and sound really opened up.
ck |
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| kuroguy |
| Here's my new 6AU6/6AQ5 with 6CA4 rectification. Has a small buzz I need to hunt down, but I'm pretty happy with these little tubes. |
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