D-MAN Posted September 28, 2004 Share Posted September 28, 2004 ---------------- On 9/27/2004 10:39:08 PM DeanG wrote: Cleaner than the Klipschorn -- definitely. ---------------- Sheesh! what Klipschorn have you been listening to? Dean, you MIGHT need to get out more... DM Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 28, 2004 Share Posted September 28, 2004 ---------------- On 9/27/2004 10:39:38 PM mike stehr wrote: Anyone have some Sovtek 2A3's they may wanna part with? ---------------- Mike, I have an extra pair for ya...email me Quote Link to comment Share on other sites More sharing options...
mike stehr Posted September 28, 2004 Share Posted September 28, 2004 ---------------- On 9/28/2004 5:05:31 PM Erik Mandaville wrote: Mike: 360VDC is not so bad, really. The 'true' voltage is taken between anode and cathode, which in this case is likely to put you more in the range of 320VDC + or - a bit. That's a little high for vintage tubes, but most current production examples can handle that easily. *Which examples? I can only think of Sovtek. KR? If you still want to lower your plate voltage to the spec of 250 for a single-ended amp, use Ohm's law and drop the voltage as needed. *I don't know about dropping around 100 volts through a resistor. Though it would work, I geuss it wouldn't be too big of a deal.. I don't know what kind of filter you've got -- choke or cap input to filter, but if it's a capacitor, lower it a couple of uf to start out. *It's a CLC. I have a oil input cap that the clamp is mounted from underneath. I would have to find a lower value oil capacitor that size, or just use a axial 'lytic underneath. I would rather stick with the oil input cap. Or I could find another PS transformer with 600 volts on the secondary. I had one but I swapped it for the higher voltage one I have now. You'll be surprised at the reactance and the subsequent result on B+. Double check your bias, though.... Right. I've noodled with the Duncan PS program to notice how much you can vary the voltage by changing the capacitance. It would be the way to drop voltage over a resistor, considering how much drop. IMO. You should be able to work this out! Well, I'll beat up some Sovtek 2A3's until find another old television PS at a yard sale somewhere...... Mike. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 28, 2004 Share Posted September 28, 2004 David forgot to call me with his news ........ Luther so which amps did he buy ??? Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted September 28, 2004 Share Posted September 28, 2004 You don't have to drop the voltage 100 volts. You're thinking of B+ on the plate alone, Mike, but need to consider the fact that you are dealing with plate to cathode voltage. For example the Welborne Moondog schematic has 350VDC B+ on the plate -- 10 volts higher than what you have. Subtract about 50 of that for 300 volts plate-to-cathode, and your overall voltage across the tube is 300. That's 50 more than the RCA spec for the 2A3. Try a 1Kohm power resistor for the cathode bias and see what you get. If you dropped 100 volts through a power resistor, you'd be too low. I wouldn't use an electrolytic to replace the oil capacitor. Depending on what rectifier you're using, I'm thinking in the range of maybe 3-10uf at 600+ volts. A good candidate for this would be a high voltage Solen. Quote Link to comment Share on other sites More sharing options...
seti Posted September 28, 2004 Share Posted September 28, 2004 ---------------- On 9/28/2004 5:24:38 PM Myhamish wrote: Tube amps, RF-7's and a neat dram of Lagavulin. You got my attention. I'm coming over with Sheepdip in hand. I had a good look through your site and am amazed at your attention to build detail (great site too) Congratulations. I bet it sounds incredible. Slainte Mhath. Hamish ---------------- no no no bring the lagavulin, sheepdip, and twins to my house Quote Link to comment Share on other sites More sharing options...
Deang Posted September 28, 2004 Share Posted September 28, 2004 D-man, I should clarify that statement a little: I was specifically thinking of the treble region when I made the statement. Of course, whenever I think of the RF-7, I automatically think of my modded RF-7s. Overall, the K-horns sound better, but it's not the kind of dusting that many would think it is, or what some others say it is. Quote Link to comment Share on other sites More sharing options...
leok Posted September 29, 2004 Share Posted September 29, 2004 2A3 parafeed SET and RF-7s is a nice combination. Have you tried using the 4 Ohm output tap. I prefer it. Leo Quote Link to comment Share on other sites More sharing options...
JohnWhite Posted September 29, 2004 Share Posted September 29, 2004 ---------------- On 9/28/2004 11:26:13 AM sunnysal wrote: I love the wood case for the bottlehead amps, nice job!...the magazine isolation system may not be optimal however, lol. tony ---------------- That really all depends on what magazine is being used for isolation hehe Quote Link to comment Share on other sites More sharing options...
sunnysal Posted September 29, 2004 Share Posted September 29, 2004 something with lots of "padding"? wink, wink, nudge, nudge...tony Quote Link to comment Share on other sites More sharing options...
Dylanl Posted September 29, 2004 Share Posted September 29, 2004 What difference would you find if the speakers were set to 4ohms vs. 8ohms. I have never tried this with my amps but others say they can hear a difference. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted September 30, 2004 Share Posted September 30, 2004 Hi, Dylan: It simply has to do with the most appropriate impedance relationship between the power amplifier and speaker voice coil. Output transformers are needed on tube amps, because there is a marked difference in impedance between the plate/s of the output tube/s and the overall impedance of the loudspeaker. Where the output stage of an amp (plate)might measure in the thousands of Ohms, speaker impedances are much lower -- and these are the familiar references to speaker impedances of 4,8, or sometimes 16 ohms. A transformer is an impedance matching device that helps these two very different impedances work together for the most efficient transfer of power from an amplifier to the speaker. Tube amplifiers can often have difficulty powering speakers with lower impedances, and some people have found they prefer the sound of using the 4 ohm connection on the output transformer (called the 4 ohm 'tap')with an 8 Ohm loudspeaker. In order to avoid possible stress on the amplifier, it's probably better to not use an 8 ohm-output amplifier for extended periods with speakers that have lower impedances, which would be the case for a 4 ohm speaker. In order to try this, you will need to know if your amp is capable of being wired or reconfigured for a 4 ohm load (speaker). Most vintage amps have multiple taps for 4,8,and 16 ohms on the back of the amp, and the user simply uses the most appropriate of the 3, with the negative speaker lead remaining on the 'common' connection. Sometimes the connection needs to be reconfigured internally, which requires some experience with soldering, as well as knowledge of the proper color coding of the secondary connections on the amplifier's output transformer. A transformer has what is referred to as a ' primary' and a 'secondary.' The best secondary connection is what is used to match the transformer to the speaker being used. An 8 ohm tap on the transformer secondary is thus used for an 8 ohm speaker. Any difference in sound is probably a little subjective, and the change, if there indeed is one, may not necessarily be for the better. It just depends on what you like. I hope this helps a bit! Erik Quote Link to comment Share on other sites More sharing options...
sheltie dave Posted September 30, 2004 Share Posted September 30, 2004 Mike, throw out some specs you may want for the PS tranny. Right now, I am working at a steel mill built in 1942, and I probably have access to about 3000 different transformers. Heck, if the electrician is on his game for the day, I would bet we could get you exactly what you want... Quote Link to comment Share on other sites More sharing options...
leok Posted September 30, 2004 Share Posted September 30, 2004 Dylanl, I find that using a lower tube amp output impedance results in less impact of speaker impedance-vs-frequency variation on the sound. This is particularly important with no-feedback designs where output voltage swing is reduced in frequency regions where the amp sees a lower impedance load. Tubes I've checked also produce lower distortion when driving loads of somewhat higher impedance than that specified for max power output. Leo Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted September 30, 2004 Author Share Posted September 30, 2004 8 ohm speakers on the 4ohm tap will get less power (about 2dB), but damping will be better and distortion lower. 4 ohm speakers on the 8 ohm tap, naturally, will get more power (about 2dB) but at higher distortion and with a lower damping factor. If you wire an 4 ohm resistor in series with an 4 ohm speaker to make a 8 ohm load, the power will be reduced even more (3dB relative to matched), and the damping will be terrible - not recommended. If you wire a 8 ohm resistor in parallel with a 8 ohm speaker, the power will be reduced more (3dB) but the damping will be improved. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted September 30, 2004 Share Posted September 30, 2004 I would like to edit (my) technical mumbo-jumbo, and simply encourage experimentation. You would do fine using one tap or the other, and it's nice to have the option of changing back to the 'correct' output impedance setting if so desired. Have fun, Erik Quote Link to comment Share on other sites More sharing options...
texas42 Posted October 1, 2004 Share Posted October 1, 2004 Sorry, I've been too busy listening to post lately . The "magazine" vibration absorbers are a new invention actually and is highly dependent on the type of magazine (I use stereophile and Sound and Vision). Actually...with the sharp points on the amps and the nice Cherry finish of my RF-7s that was the quickest thing we could think of to put them on. Was a spur of the moment thing and not a long term fix, I assure you... The SETs definitely have an immediacy to them that is alluring. Luther really did a nice job on these Paramours and they sound as good as they look. They also seem to really compliment what the RF-7s do best. I recently picked up a pair of big Klipsch Epic CF-4s so will have to see how they sound with them as well. I'm guessing they would also do very well. So much to listen to, so little time.... Regards, Dave ---------------- On 9/28/2004 4:27:50 PM Wardsweb wrote: ---------------- On 9/28/2004 2:18:50 PM Daddy Dee wrote: Wardsweb, Yes, the 2A3's do sound sweet. Is this a Bottlehead amp? Not Paramours, though, right? ---------------- Yes, these are indeed Bottlehead Paramour 2A3. While close to the kit build they are modified and a whole lot of attention to detail. You can see the entire build on my web site: Wardsweb's Paramour Construction Site By the way, these are not my speakers, but a friend of mine who I was expecting to chime in here about his system. ---------------- Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted October 2, 2004 Author Share Posted October 2, 2004 Wow, only took you about a week to tear yourself away long enough to log on. I still need to bring by the custom 2A3 stereo SET I did. I found out the problem was not in the amp but in the source I was using. DOH! Quote Link to comment Share on other sites More sharing options...
nblis Posted October 3, 2004 Share Posted October 3, 2004 Wardsweb: That's a really nice setup. What kind of music do you listen to? I'm interested in moving to a SET amp and Klipsch speakers, but I'm wondering if the RF-7 (or Cornwalls or Fortes) have problems reproducing female vocals? In addition, I am wondering if such a setup (say 2a3 with the RF-7) could handle something with a lot of bass? I listen to stuff from classical (Bach organ) to rock!!!! Any thoughts would be appreciated. Noel Quote Link to comment Share on other sites More sharing options...
Parrot Posted October 3, 2004 Share Posted October 3, 2004 Noel, A low-powered amp is a poor choice for properly reproducing the lower bass frequencies. Quote Link to comment Share on other sites More sharing options...
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