AX84 BBS Recent Posts as of Sun, Nov 23rd, 2014 @ 00:59:33 http://ax84.com Amp Parts and KitsDoberman Music Products, LLC offers a variety of parts and kitshttp://shop.dobermanamps.com RE: What should I do with my Peavey Classic 30?(by Darren Porter) Well I used the JJ's in my core 20W Push Pull build. I really like the amp a lot. It's fixed biased. The designs I am thinking of doing for this project are both cathode biased. Either a dumblish design from el34world or an 18-watt variant of some sort. Maybe an SIII/TMB. If I use 6V6's I'll have to drill-out the socket holes unless I can find or build build my own 9-pin to octal adapter of some sort. With this power supply only giving 330-ish volts I'm thinking an SIII might be the way to go. Sat, 22 Nov 2014 23:45:46 -0500 http://ax84.com/bbs/dm.php?id=487524 RE: favorite tone stack(by Kursad K) <div class="quoteblock" >On 11/22/2014 @ 13:44, The Tone Surgeon wrote : yeah, I see what your saying but it does let you voice your amp alittle... even if it is flawed -- </div> It's not flawed, but just works for a different purpose than its label. KursadSat, 22 Nov 2014 23:31:17 -0500 http://ax84.com/bbs/dm.php?id=487523 RE: Tube rectifier in a SE amp?(by sajyho) <div class="quoteblock" >On 11/22/2014 @ 13:23, trobbins wrote : You could put a doubler on the PT. If you use 'not so huge' doubler filter caps, then although the ripple will be highish, the rectifier hash will be less of a concern. You can then use a subsequent LC or RC filter to get the final voltage and low ripple you are after. : : Your doubler C may end up being quite low, like 4uF, in which case it is better to use a poly cap (eg. with a 275VAC rating). As there will be negligible sag, due to class A, then the filter values will be easy to tune to give the HT voltage aimed for. -- </div> Thank you man, you opened a new door for me. I'll give it a try soon...Sat, 22 Nov 2014 23:17:29 -0500 http://ax84.com/bbs/dm.php?id=487522 RE: Dual Concentric 1 meg Pots?(by Joseph P Befumo) I would be interested -- I actually have several on hand that I bought not all that long ago, but now the source appears to have dried up. Do you have a time frame in mind? Sat, 22 Nov 2014 22:38:07 -0500 http://ax84.com/bbs/dm.php?id=487521 RE: What should I do with my Peavey Classic 30?(by Ken Graves) 330 will do fine, though most are run a bit higher. Just curious, what brand are those 6V6s? I ask because modern JJs are extremely rugged and can take abuse that other tubes would fold under and come out smiling. I think it's because they not actually a normal 6V6 but their design yields the same figures. Can't recall exactly where I read that. I have a single ended amp with one in it and it really sings when pushed (read 'screams'). Will your design have them cathode biased or fixed? Sat, 22 Nov 2014 22:08:38 -0500 http://ax84.com/bbs/dm.php?id=487520 RE: mic preamp hum(by Paul Fawcett) Is that Hammond input transformer in a mu-metal shielded can? The 1500 ohm secondary impedance of the 140NEX is rather lower than is ideal for feeding a tube grid. Really you want something like the 15K secondary impedance of the Jensen JT-115K-E series, or if you suspect you have a problem with radiated noise, the JT-115K-E60 series which is in *two* mu-metal cans. As pointed out in the accompanying comments, you really want even higher than 15K, but there starts to be issued with bandwidth <a href="http://www.jensen-transformers.com/transformers/mic-input/ " target="newwin1416722377">[link]</a> If you do decide to try a different IT, take a look also at offerings from cinemag and Sowter UK.Sat, 22 Nov 2014 20:41:46 -0500 http://ax84.com/bbs/dm.php?id=487519 RE: trouble shooting some unwanted distortion(by cameron nicklaus) well, I think I may have answered one of my own questions...when I grounded the grid of the triode that I was seeing signal on it went away. So maybe my assumption that it was picking up signal through that air was correct? maybe not ;) Sat, 22 Nov 2014 18:14:51 -0500 http://ax84.com/bbs/dm.php?id=487518 trouble shooting some unwanted distortion(by cameron nicklaus) man oh man I'm stumped. this is a straight up PR clone...It sounded fine except for when I record it I hear a bit of distortion even at relatively low volumes. I almost can't detect it when just listening in the room but it's pretty obvious through a mic. This may end up being a bunch of questions in one... first off, does anyone have any tips for trouble shooting distortion with a scope? I have a decent one but I'm a bit inexperienced at using it. I can dial in a wave on the screen and can put a sine wave through the amp and see when the wave begins to change shape but I can't recreate the type of distortion I'm hearing with a sine wave...it seems to stay normal way beyond the volume I hear distortion with a guitar at. to try to figure out where it's coming from I bypassed all the gain stages and took the line running into the first gain stage and ran it straight into the phase inverter. so basically; guitar-input jack-gain stage that precedes the cathodyne PI. one really curious thing (that may have nothing to do with anything); at one point the tone stack and the triode after the tone stack was bypassed but I still saw signal on the plate of that triode....so nothing wired to the grid of the triode but still saw AC signal on the plate...how is that possible? would the grid pick up enough just through the air? I had guitar signal coming out of the amp...I thought that, if I disconnected the wire going from the volume pot into that second triode, it would kill the signal? any thoughts or suggestions of things to try would really help!!! Sat, 22 Nov 2014 18:14:51 -0500 http://ax84.com/bbs/dm.php?id=487517 RE: What should I do with my Peavey Classic 30?(by Darren Porter) <div class="quoteblock" >On 11/21/2014 @ 21:12, Ken Graves wrote : Yeah, I'd gut it and go for something you're dreaming about. The PT could be of use even if you're thinking lower wattage. Just my take. (kinda wish I had such an amp to play with) -- </div> You think 330V plate is enough to drive a pair of 6V6 satisfactorily?Sat, 22 Nov 2014 14:47:15 -0500 http://ax84.com/bbs/dm.php?id=487516 RE: favorite tone stack(by The Tone Surgeon) yeah, I see what your saying but it does let you voice your amp alittle... even if it is flawedSat, 22 Nov 2014 13:44:29 -0500 http://ax84.com/bbs/dm.php?id=487515 RE: Tube rectifier in a SE amp?(by trobbins) Oh, and PSUD2 is your best friend here :-)Sat, 22 Nov 2014 13:25:03 -0500 http://ax84.com/bbs/dm.php?id=487514 RE: Tube rectifier in a SE amp?(by trobbins) You could put a doubler on the PT. If you use 'not so huge' doubler filter caps, then although the ripple will be highish, the rectifier hash will be less of a concern. You can then use a subsequent LC or RC filter to get the final voltage and low ripple you are after. Your doubler C may end up being quite low, like 4uF, in which case it is better to use a poly cap (eg. with a 275VAC rating). As there will be negligible sag, due to class A, then the filter values will be easy to tune to give the HT voltage aimed for.Sat, 22 Nov 2014 13:23:53 -0500 http://ax84.com/bbs/dm.php?id=487513 3 Speakers - What to do?(by David E) Hi folks, been a long time. What might I do with three speakers salvaged from an old (solid state) organ? Probably 8 ohms impedance each. I kinda want to build a tweed deluxe, but I haven't built anything for a looong time. <a href="https://www.flickr.com/photos/eggend_houston/15666849580/" target="newwin1416722377">[link]</a> Sat, 22 Nov 2014 12:32:54 -0500 http://ax84.com/bbs/dm.php?id=487512 RE: favorite tone stack(by Kursad K) <div class="quoteblock" >On 11/22/2014 @ 11:08, The Tone Surgeon wrote : Hi im fairly new around here and I was just wondering which tone stacks are your favorite. : : personally iv always liked the simple tmb controld of my p.o.s. solid state Marshall. but I really don't have alot of experience in the matter. -- </div> Personally I dislike them all. They are usually ineffective and not a tool for looking for different sounds, they only work for balancing overall tone for playability or to match it to something else. An amp usually has a characteristic tone that never changes regardless of the tonestack adjustment. KursadSat, 22 Nov 2014 12:24:59 -0500 http://ax84.com/bbs/dm.php?id=487511 RE: High pitched oscillation problem(by Kursad K) <div class="quoteblock" >On 11/22/2014 @ 04:21, steve25 wrote : Don't rule out a low level Sinus infection as they are super hard you kill off with any kind of antibiotics, even taking them for a long time, and lest not get into the digestive problems from that! : : I have found improvement in my ringing by flushing my sinus twice a day with diluted Hydrogen peroxcide. -- </div> I have a long time sinus infection problem, it's chronic:) Antibiotics can improve the situation for a few weeks, then it returns, but never gets too bad (that's the usual character of sinus infections, they are terrible only when they are acute). Apparently medical practice changes from country to country. My wife is a medical doctor and she said she has never heard of the usage of diluted hydrogen peroxcide to treat sinus infections. Not that it does not make sense, it does (at least to me). Kursad Sat, 22 Nov 2014 12:09:46 -0500 http://ax84.com/bbs/dm.php?id=487510 RE: Tube wah (Eric Barbour/Peter Belov)(by Kursad K) <div class="quoteblock" >On 11/22/2014 @ 10:51, The Tone Surgeon wrote : well I have alot of.learning to do first.. if someone else wants to build  it also id help where I could in the design but im still pretty green to designing things : : maybe someday -- </div> OK, if you someday decide the proceed, this link includes pot values of several midi expression pedals that you may buy (they are usually cheap). <a href="http://www.korgforums.com/forum/phpBB2/viewtopic.php?t=77351 " target="newwin1416722377">[link]</a> The relevant part is as follows: Bespeco VM18L - 20k Boss FV-500 - 10k linear (expression pot) Boss EV-5 - 10k linear Boss EV-7 - 10k linear ("extra range" pot adds up to 50k ohms) Boss FV-50L - 50k linear Ernie Ball VP jr. (active) - 25k log Ernie Ball VP jr. (passive) - 250k log Korg EXP-2 - 50k linear Kurzweil CC-1 - 20k linear Line6 EX-1 - 10k linear Mission EP-L6 - 10k linear Moog EP-2 - 50k linear (reducable) M-Audio EX-P - 10k linear Pigtronix EP-1 - 20k Proel Volume Pedal - 100k linear Roland RV-5 - 10k linear TC Electronic X1 - 25k log You'll need to find a compatible circuit that has a pot with the same value that controls the center frequency of a band pass filter. Kursad Sat, 22 Nov 2014 11:50:59 -0500 http://ax84.com/bbs/dm.php?id=487509 favorite tone stack(by The Tone Surgeon) Hi im fairly new around here and I was just wondering which tone stacks are your favorite. personally iv always liked the simple tmb controld of my p.o.s. solid state Marshall. but I really don't have alot of experience in the matter.Sat, 22 Nov 2014 23:31:17 -0500 http://ax84.com/bbs/dm.php?id=487508 RE: Tube wah (Eric Barbour/Peter Belov)(by The Tone Surgeon) well I have alot of.learning to do first.. if someone else wants to build  it also id help where I could in the design but im still pretty green to designing things maybe somedaySat, 22 Nov 2014 10:51:43 -0500 http://ax84.com/bbs/dm.php?id=487507 RE: Tube rectifier in a SE amp?(by sajyho) <div class="quoteblock" >On 11/22/2014 @ 05:29, mac dilard wrote : Take a look at a Fender Champ. I think the 290 plate voltage is a little low. It will work for sure but 6V6's like around 340 volts. -- </div>You're right man, unfortunately I have only a PT with 220Vac secondaries, so I guess I have to rebias the 6V6!Sat, 22 Nov 2014 10:03:56 -0500 http://ax84.com/bbs/dm.php?id=487506 RE: Added Merlin's "Scale Control" to my Simple/20WPP(by Dave C) If you have the first edition of Merlin's pre-amp book, scale control can be found in chapter 8 that deals with the long tail pair phase inverter .. figure 8.22.Sat, 22 Nov 2014 09:57:48 -0500 http://ax84.com/bbs/dm.php?id=487505 RE: rhythm/lead switch question(by Ken Graves) That might work fine - it would be interesting to play with. I notice I didn't make it very clear in my earlier post: with the lead kicked in the two ganged pots are connected in parallel. That's what makes it work so well. I look forward to hearing your results. If it works better than what I've got I might just have to some (more) modding to it.Sat, 22 Nov 2014 09:55:41 -0500 http://ax84.com/bbs/dm.php?id=487504 RE: Tube wah (Eric Barbour/Peter Belov)(by Kursad K) <div class="quoteblock" >On 11/22/2014 @ 09:33, The Tone Surgeon wrote : interesting exciting stuff :-).... I'm wanting to build a wah... but it probably won't have tubes In it. : : at least not the first one lol -- </div> I am sure a variant of the circuit that Stephen posted can be built with op-amps or transistors. KursadSat, 22 Nov 2014 09:35:15 -0500 http://ax84.com/bbs/dm.php?id=487503 RE: Tube wah (Eric Barbour/Peter Belov)(by The Tone Surgeon) interesting exciting stuff :-).... I'm wanting to build a wah... but it probably won't have tubes In it. at least not the first one lolSat, 22 Nov 2014 09:33:48 -0500 http://ax84.com/bbs/dm.php?id=487502 RE: What should I do with my Peavey Classic 30?(by Darren Porter) <div class="quoteblock" >On 11/22/2014 @ 05:37, mac dilard wrote : Try that amp with another set of speakers. You just might like it. The Peavey Classic 30 and Classic 50 are really tough amps. You can't hardly tear one up and Peavey still supports them. You ought to run that amp on flee bay before you tear it up. There are some folks that really like the Classic 30 and Classic 50 amps. -- </div> I have tried different speakers and I still don't like it. I just do NOT like the dirty channel. That is the number one complaint about this amp. I know they are popular and I could probably get an OK amount for it but I think I'd rather reuse the iron, chassis and cabinet for a personalized practice/small gig amp. Sat, 22 Nov 2014 07:51:18 -0500 http://ax84.com/bbs/dm.php?id=487501 RE: Added Merlin's "Scale Control" to my Simple/20WPP(by Darren Porter) <div class="quoteblock" >On 11/22/2014 @ 06:54, SX4Amps wrote : Which one of Merlin's book is this in? : -- </div> This one: <a href="http://www.valvewizard.co.uk/Book1.html" target="newwin1416722377">[link]</a> Sat, 22 Nov 2014 07:47:06 -0500 http://ax84.com/bbs/dm.php?id=487500