Dale W Posted May 4, 2004 Share Posted May 4, 2004 Is there a method of determining what db level of line attenuator to try using between the amps and pre-amp ? Harrison laboratory makes these in 3db 6db and 12db there around the $25.00 mark for a pair, not to bad of a price but i still don't want to order and try all 3 before deciding on my needs. I'm trying to pad a bit between my mark III's and pre-amp so i can get a bit more range out of the pre-amp , 9 o'clock position and the room is finished as far as carrying on a conversation , plus i don't start coming on board untill the 7 o'clock position . So as you can see i have a bit to much gain and very little room between no sound and a room full of it. Is there a method of figuring how the attenuators will effect the volume range ? or is this a hit and miss science. PS : I don't want to open up the pre-amp and resistor pad it as future plans may call for this JFL design to be moved to another system . Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 For anyone who might have missed the build of this lovly 6SN7 SRPP Tube rectified sweetheart, heres one last view . Quote Link to comment Share on other sites More sharing options...
3dzapper Posted May 4, 2004 Share Posted May 4, 2004 3db will cut the output to 1/2, 6db to 1/4, 12db to 1/8. In an audio tapered pot the largest change in resistance is right where you are sitting. 3db (IMHO) won't get you much. My question then would 12db be too much? You are putting them on the input correct? A cheaper solution would be to put a resistor in series with the pot. Perhaps 50k with a 100k pot. Experiment. My ramblings. Rick Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 RICK : Between the pre-amp and amps so i'd be dampening the signal prior to amplification. Craig and i talked about this on the phone not to long ago and if memory serves me right, the 12 db was his thought as well . JFL sent me a sketch for resistor padding but i've got other plans for this pre-amp in the not to distant future so that option i'll ignore right now. Thanks for now Quote Link to comment Share on other sites More sharing options...
3dzapper Posted May 4, 2004 Share Posted May 4, 2004 Yes Dale before. If you do it after you run a large chance of driving the tubes into saturation or into a non-linear region of their range. By placing the attenuation in front of them you are applying a lower signal and can stay in that preferred linear range. Rick Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 Guess i'll shoot for the 12db ones and see what results they bring . Last option would be back to " The ice box " ( nickname for JFL workshop ) for a step attenuator vs the volume pot i've got now . Little bit more of a job then i feel comfortable doing myself right now . Quote Link to comment Share on other sites More sharing options...
NOSValves Posted May 4, 2004 Share Posted May 4, 2004 Dale, Glad to see you posting again keep it up. I'm heading to White River, Ontario on the 21st for plenty of Labbatt's and Walleyes & Pike ! Man do I need the break and some good old Canadian fresh air and hospitality ! Craig Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 Good for you craig !! Everyone needs a break once in awhile . Fishing should be good , water is still cold so that swampy taste has yet to settle in . I personaly pan fry with a tad of butter and some lemon pepper spice , yum yum We did a bit of perch fishing just before freeze up last year , before pan frying on the open fire we crushed up a bag of salt and vinager potato chips and rolled the fillets in the chip crumbs . Makes and excellent breading !!! HA !!!! Your going to have to make a trip way the frick up north some day and we'll do some arctic char or steelhead fishing . Personally i hardly fish anymore because the posession limits are so low now , turns out to be more of a drinking and social outing . Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 4, 2004 Share Posted May 4, 2004 Dale: You can try padding the input v.s. the output or the preamp. Those inline resistors in an RCA jack might add enough impedance to the output of the preamp to possibly cause some loss of high frequency detail. They will certainly attenuate the signal, but maybe (or maybe not)at the compromise of some transient speed and detail. They are easy things to use, though! Reducing the input signal into the preamp can achieve the same thing. For example, if you have a volume control with a value of 100K ohms, adding a 100K ohm series resistor between the poles of the selector switch and the volume pot will provide about 6dbs of attenuation. This is just more of a hassle, and maybe I shouldn't even have brought it up! Adding the inline resistor between the preamp and amps could also have the added benefit of quieting a little extra noise -- if that is any concern at all. E edit: Oops! sorry Dale, I just saw your footnote and the explanation why you wouldn't want to do what I mentioned above. But! I just thought of something that might be really interesting (to me anyway): You could try those inline jacks on the INPUT to the preamp -- maybe where your CD is connected. You could experiment between the two to see which sounds best. Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 Thanks Erik : Thats pretty much par with the advise i've been getting from a few different sources . All in all it's just a temp fix of a larger issue but 100% reversable in just 1 minute , simple plug and unplug . Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 4, 2004 Share Posted May 4, 2004 Dale: Who sells those? I've seen them on occasion, but was never interested enough at the time to pay attention. But they really could be useful! Thanks for bringing up this up! Quote Link to comment Share on other sites More sharing options...
Marvel Posted May 4, 2004 Share Posted May 4, 2004 Dale, I will hype the freebie little program I use again. I is a pad calculator, and allows you three variables. Input Z, Output Z, and the amount of attenuation in db. It will do balanced and unbalanced pads. Six resistors total for a stereo cable. You can try some different ones and see what works best/ sounds best. Pretty cheap (although not attractive) and you can try first with those Radio Shack parts. Make it beautiful after you get it to work. I've found it useful to connect devices where I need to do a funny impedance match. I can email you the program, as it is very small. Or tell me the values you want and I'll email or post the schematic. Marvel Marvel Quote Link to comment Share on other sites More sharing options...
Dflip Posted May 4, 2004 Share Posted May 4, 2004 Here is a link to the website for the company. It describes the product. http://www.hlabs.com/technical/crossovers/ They also have an ebay store: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=14978&item=3074430392 This is a link to a company that sells the product. There are probably others. http://www.headphone.com/layout.php?topicID=3&subTopicID=31&productID=0060220005 Quote Link to comment Share on other sites More sharing options...
Q-Man Posted May 4, 2004 Share Posted May 4, 2004 I have an old Phase Linear 4000 pre amp. I havn't used it in many years. It has a cool feature on it, this feature is a -20 db switch. I used to use this pre amp in my stereo days with a 100 watt per channel power amp and a pair of LaScalas. It was designed so one could get the volume control near the 12 o'clock position where the pre amp is susposed to sound better and offer better control. Most of the time I had the -20db switch on and my volume control knob would be in the 10 o'clock position. I remember that when I wanted it loud that I would walk up to the pre amp and turn the switch to normal. Then it would almost blast me out of the room. I used to like to tell people to move the switch to off when listening to music. The sudden and powerfull increase in volume would scare the heck out of them. I think the 12db one may be the one that you want. Quote Link to comment Share on other sites More sharing options...
greg928gts Posted May 4, 2004 Share Posted May 4, 2004 Dale, what about a remote passive volume attenuator? I use a Creek OBH-10 in several of my systems with great results. It only cuts volume, it doesn't add. I find them to be totally transparent in passing the signal through. You get the benefit of remote volume and mute as well. I'll send you one to try out if you're interested, I have 5 of them! Any word on that other thing? Anxiously awaiting is putting it mildly. Greg Quote Link to comment Share on other sites More sharing options...
Dale W Posted May 4, 2004 Author Share Posted May 4, 2004 ERIK : Partsexpress Marvel : thank you for the offer , i might take you up on it. Dflip: thank you for the links Qman : ( my hero as well ) Yes 12db is pretty much what we all have been thinking . PS : I've got a line on some EV-1 cornerhorn clones that i want to 311-90 and 2404h so i may bend your ear on johns crossover in the future Greg : The parts from jeff are finished and if it's allright with you i'll ship those back to him , the others should be ready to pickup as soon as i get a free moment, i'll E-mail you before i ship anything. On a much more personal note, thanks for all the support guy's , it's sure nice to be back chatting with you all again. This has been a real trying few weeks latly , first off my uncle was sent home with a never ending persription for morphine and the bad news of cancer in the lungs throat and well ------ everywhere else too he's 58 . Two days later his mom ( my grandma ) fell and broke her hip , she's 95 years old this june and this is the first thing ever to happen to her . Work is work and my 2 kids are very demanding this time of year so no personal time for Dale latly. Cheers for now and thanks to everyone once again . DALE Quote Link to comment Share on other sites More sharing options...
LOADEDTUNES Posted May 4, 2004 Share Posted May 4, 2004 Dale : When others are in there time of need our true character seems to surface , i know you'll handle things in your normal manner . Hope all is well with you . Judgeing by your comments on the above posts about not fooling with the pre amp , does this mean your moving ahead with another tube amp project ?? Maybe a SET ? Quote Link to comment Share on other sites More sharing options...
minn_male42 Posted May 5, 2004 Share Posted May 5, 2004 a simple 10k pot inline will do the trick..... mono pots run about $3.00 each.... a stereo pot is about $5.00.... should be available at radio shack.... it allows you to adjust the input level infinitely.... not a set level like your inline pads.... Quote Link to comment Share on other sites More sharing options...
Marvel Posted May 5, 2004 Share Posted May 5, 2004 A simple 10k pot will also change your impedance. This is why a pad will work better, and can be used to match the input and output impedance. How much do three resistors cost you? It will take almost the same amount of time to make the pads. Marvel Quote Link to comment Share on other sites More sharing options...
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