Jump to content


JamesPeters

Member
  • Posts

    39
  • Joined

  • Last visited

    Never

About JamesPeters

  • Birthday 01/19/2022

Converted

  • homepage
    petersamps.com
  • occupation
    amp designer/builder
  • Location
    Calgary, Canada
  1. You're right. Well, I'm taking step #1 tomorrow, and that's getting the metal shop that makes my chassis to do all the drilling on the chassis. It's far too time consuming for me, more than anything else so far that I do on the amps. I'd originally thought I should leave the drilling until later in case I wanted to make changes on individual amps, or start a new design...but that's just not practical at all (and I have enough sales now to justify letting them do the drilling). I tell ya, if we did get "quantity orders" it would sure make Mark happy too. I handed him his pay for the enclosures and I think he got an idea how this could turn into something really big. Later!
  2. Hey Myles. This forum doesn't normally move that quickly, so I must've forgotten to check back. "The guy that I listen to and learn from", oh come on! I'm just some bum who's making amps... (This isn't going to turn into a "you're the best" / "no, you're the best" type of thing, is it? ) Wow, "shipping in quantity"...hadn't thought about that yet. I'm just rounding out my first ten orders this week. So far that in itself has been almost incredible for me, to have that much interest in less than two weeks since my site has been "complete" with the purchase page. I'm still working full time as the manager of a service center (for a vending machine company), and before I go full-on amp building I have to at least make sure the center is ready to move ahead without me. I've been there 5 years now and have been treated well, so I figure the least they deserve is that they're taken care of before I move on. There have been a few changes there recently and I've had to hire and train again, so I'm not quite ready to take the plunge yet. For now I'll just sell the amps from my site, or locally. Speaking of which, I have an interview today with a local paper--Mark (my friend who's making my enclosures, and soon speaker cabs) and I are going to try to get the point across to Calgary that we're "in business", something that has been almost ignored here so far (which is really weird considering that I have 9 orders from the last two weeks from the USA!) Anyway, one step at a time I guess. Man, a review in Guitar Player...that would rock! I'll keep you posted (no pun intended!) as to my "gearing up" progress. I'll probably be staying at my current job for the next couple months anyway to make sure things are going well. In the meantime, I want to see if I can get to know guitarists in Calgary and get the grassroots thing going on. I'd almost not feel comfortable selling lots to the USA before having "paid my dues" locally...call me naive I guess. Talk to you later!
  3. Just happened to read this (as I learn so much from Myles, I tend to follow this thread! ) With single-ended class A, it's a "non-issue". There's nothing to match a tube with (it's only one tube in the poweramp). As for other amps that work in class A other than single-ended, it shouldn't be as critical as class A/B amps--because the multitude of tubes (whatever number) are supposed to be amplifying signal "simultaneously all the time" (which isn't necessarily true either, but you know). Class A/B amps have tubes that share the responsibility of amplifying the signal, and there's the critical crossover point which should be a smooth transition (where one tube or pair of tubes "lets the other pair" take over the other half of the signal). That's a big part of it. There's also the response curve of the tubes to consider, as class A/B amps have little current draw when no signal is present on the power tubes' grids, but ramp up to higher current draw when there is signal present there. Class A, generally speaking, has a more or less constant current draw going on. Exactly how this all sounds, that's harder to describe. Just felt like throwing my two cents in I guess.
  4. Oh man, I could only imagine someone saying that to me--I think I'd split my sides! Ok, I got a few clips up...I have a couple more hours of stupid noodling to go through before I put the rest up, but I had to get something up--too many people were asking for clips for me to leave it until "I had the time" (which the way it's going this week, may never happen, lol!) Catch you later!
  5. Hey Myles, how goes? Yeah, I tend to ramble sometimes...the typing almost gets ahead of my train of thought! Good thing to clear up the "standby on / standby off"--I remember being confused by the standby switch a few years back. "Turn standby on", someone would say, and I'd be like, "Umm, you mean use 'standby', so that the amp doesn't make any noise?" A little like saying the phrase "Close the lights" (a french-canadian thing you might hear sometimes)--the first thing I think of is "closing the circuit", which means turning the lights on. The amp is doing very well--that's part of the reason I've delayed launching petersamps.com for the last week. I got tweaking again--there goes the week! But I found a touch more subtlety while getting more gain yet...then in the end had to back off the gain somewhat because on its loudest settings it would get feedback. I know that's not the end of the world or anything, but part of the idea behind this amp was that no matter what setting I used on the dials/switches, I'd always find it "useable". I'm glad I spent the time, because I like the amp a lot more now than I did even a couple weeks ago. Some people can't quite put their finger on what's different if I don't crank the gain, but some people on the other hand consider it a drastic improvement. Now, I just have to MP3 the new clips (I have maybe a couple hours before bed tonight yet--long days at work!), paste the updated text, and get a couple pics pages going. Work work work! Talk to you later!
  6. Hey GTO, mind if I butt in? The standby switch is used to break the connection of the high voltage in the amp. That would leave only the filament heater supply of the tubes powered when the power is on (and the standby is off). The whole deal with that is to let the tubes heat enough to be able to handle their operation. It takes between 30-90 seconds (depending on the tube) to fully heat the tube's filaments to a normal operating temperature. If the tubes filaments aren't hot enough, what can happen is that if signal hits the grid of the tube it starts going about doing its thing...and electrons get stripped off the cathode ("cathode stripping"), resulting in premature tube wear. Keeping standby off for the first couple minutes the amp is on, then turning standby on, will help keep your tubes healthy longer. If your amp doesn't have a standby, then it's advisable to not play your guitar until the amp has been on a couple minutes. If the amp has a tube rectifier, those take a while to get the high voltage up to proper range, so in reality standby may not be needed on any amp with a tube rectifier. I'd still use the standby though if it's on the amp, since you're not "rushing" to start playing before the tubes are good and ready. Powering down, it might probably be just as good to shut the standby off first until signal is gone...although I'm not sure if this matters or not since if you powered down while signal is on, it takes the tubes' filaments a while to cool. The issue of shutting off with/without standby gets thrown around a lot, but nothing significant has come of the discussions as far as I know. One guy I know said he puts it on standby for a few minutes before shutting off, to let the tubes cool...but the logic in this seems flawed--if the tubes get that much hotter from the high voltage being on the plates, then how significant a difference is it if you remove the plate voltage first, then remove the filament supply later. I mean, do your tubes really cool more evenly by doing this? It seems unlikely. Oh well. That's all I got!
  7. Thanks again for the tips, Myles. I do think that the 6550 drawing 72mA instead of 70, through the 125DSE, is plenty fine though. To be honest, it's not a "wonderful" sound in the amp anyway--I think the EL34 is nicest, and the 6L6s/5881s have nice definition and are more than adequate for "metal" music. The 6550 is more abrupt and unforgiving with dynamics in the higher gain settings--kinda like solid-state that way (but not really, you know what I mean). I'm going to sell the amp with the 125DSE by default, and if someone absolutely wants reliability with a 6550 then I'll just put in a 15W 125ESE--they're the same price anyway! Talk to you later.
  8. Ok, just tested the 6550 in it (Svetlana 6550C, and 6550B--that I got from the guy who's making my enclosures...leftovers from his Ampeg SVT when he switched to KT88s as it were). The current draw slightly exceeds the spec for both the power tranny and the output tranny, but just by a hair. 72mA plate current--2mA "extra" for the 70mA rated OT (Hammond 125DSE), and 7mA "extra" for the Hammond 269EX PT (rated at 65mA, so that's not much extra anyway). Given that these Hammond trannies have been known to withstand considerably worse abuse, I'd say it's a go for the 6550. (The trannies didn't even get warm, and I was actually using a 125CSE OT rated for 60mA max. for the test, just to know for sure if the 125DSE would be safe--call me paranoid! ) Oh yeah, and the heater current draw is still 300mA below what the filament supply is rated for (2.2A instead of 2.5A), so that's a gimme. The 6550 has a fairly nice sound in this amp, all things considered, which being biased this cold I found surprising (72mA, for a tube which "normally" should see about 140-150mA at this plate voltage--222V B+). It's total heavy metal at this point--really high headroom so the preamp gain "crackle" comes through a lot. It's more forceful and not as bouncy as the 5881, so the envelope is more "square" and abrupt. Not exactly what I had intended the amp to be used for, but hey I'll take it! Actually, since the plate voltage is browned out that extra amount, it still has a nice warmth to it. I like the woody overtones of 6550s usually--I'll have to check it out my amp cranked with a less overdriven preamp sound, to hear if I can really take advantage of that or not at this bias point/B+. (Hmm, I wonder what triode mode will sound like...) Talk to you later!
  9. Ok, but you're beginning to make me blush!
  10. Oh, the Sovteks are shorter? Right on; those are the ones in stock at the music store anyway. In any case, if I did have to change the height it would've been more than I wanted to--I'd have to leave at least an inch from the top of the tube to the underside of the top of the enclosure (so the tubes don't smack against the enclosure when you're removing them!) I had looked up the tallest tube that I had planned to use with the amp, the 6CA7 (EL34 equivalent), and based the measurement on its longest overall length plus one inch or so for clearance. I'd almost forgotten about that... But I'm still going to try the KT88 and 6550 in it soon. And, if that Sovtek KT66 fits, then for sure I'm giving it a test.
  11. Thanks Myles. I did find a few KT66's locally...apparently they're the larger ones--I'm going to pick them up in a couple days anyway and try them. Fortunately for me, to make them work in my amps all I have to do is change enclosure measurements slightly, before the enclosure is made...if I need to that is.
  12. Oh hey I just realised--that's a honkin' tall tube! I may have to change the dimensions of the amp to allow it to fit. What's your KT66 measure--both seated depth (not including the pins, after the bottom of the base) and overall length?
  13. Thanks Lance! KT66 you say...ok I just looked at some data sheets and I think it's a go. I'll have to actually get my hands on one to test, to make sure it doesn't draw too much current--but I honestly think it'll be fine. (Now, where can I get a KT66... ) I'll see if I can scrounge one somewhere in town. If you like, I can email you when I find out--it might be up to a week depending on if they're any KT66 tubes in stock or not.
  14. Thanks for the tip Myles, and for the props! I'll have to ask about any discounts I can get for tubes...but somehow I doubt I'm going to get any special treatment just yet. Noone really knows me yet, so it's not like I'm some really famous amp guru that they'd already know about. I'll still ask them though--hopefully those discounts won't involve having to buy in large quantities (because I still can't afford to do that, at least not yet). Yeah, once I heard the amp at 250V B+ I knew that was part of the sound. The higher powered one coming soon (3CP2) will stick to 250V B+, which made my transformer choices a little narrower...but I'm not going any higher in B+ if I can avoid it. I'll do 1500 on the primary parallel class A, which will do: 2 x EL34, 2 x 6L6, or 1 x 6550. Another bonus of sticking with that low a B+ is that all my components, wires, etc. are much higher rated than what they need to be--part of my concern with the amps was to keep the design "bulletproof", and this helps a lot.
  15. Thanks Myles! Yeah about the preamp tube thing--I just wanted to clear up a basic misconception that was going around, that my amp (in the pictures) couldn't possibly be getting that amount of pregain. I'm going to avoid a more technical explanation, for the sake of not hurting people's brains! So, silicone the wires down, you say? Got lots of silicone, no problem there! As for the board--I don't have any problem leaving it as-is. As it is, the layout is pretty high gain and low-noise (higher gain and lower noise than I had before), and a fair number of components are wired right to the sockets to help keep the noise down. The board itself doesn't take me that long to make; more of the time is spent wiring things to and from it to be honest. Thanks for the suggestion though, because if I ever do get into any kind of steady production I may have to look into that (everything that can save me time will be helpful). I'm also trying not to incur any additional costs at this point, since I have very few orders at this point and I'm dead broke from buying parts (and other things happening in my life right now). With any luck that'll change soon enough; I'm optimistic. The 3CP1 I'm selling for $480 USD (plus shipping of course), and that's without tubes though. Being that I've had tubes break in shipping before, I'd rather not ship them with the amp. That, and I get no deals whatsoever on tubes, and truth be told it seems that most places in the US seem to sell them for cheaper than here in Canada anyway. That price, I'm trying to keep that low for the first while anyway. I can forsee the price increasing somewhat (especially if I let a distributor carry it, then I'll have to raise prices to allow their "cut"). I'm going to try to do all the sales myself though, through the Internet or word of mouth...or advertising etc.--I'd really like to be able to offer an amp like this at a very reasonable price. The output section is honestly optimized for all three tube types--EL34, 6L6/5881, and 6V6. Since I'm using the Hammond 125DSE, I can run 2500 or 5000 ohms on the primary depending on the tap and the secondary load, which works out perfectly for designing the amp around tube data sheet "typical operating conditions" examples. So, with the EL34 or 6L6/5881, I'm using 2500 on the primary, and with 6V6 I'm using 5000 on the primary. The 6L6/5881 also works right within "typical operating conditions" at 5000 ohms on the primary as it turns out, making it the "wild card" tube in this design--it'll work at 4, 8 or 16 ohms whereas the EL34 is only 4/8 ohms, and the 6V6 is only 8/16 ohms. The 6L6 is actually starting to become my favorite tube in this amp. The bias points for the power tubes are dead-on what's considered to be the "normal operating conditions" for single-ended class A at the B+ the amp runs at (which is 250V), right from tube data sheet examples. The plate voltages are slightly lower when using a 6L6 or EL34 (like maybe 240 or so), and with a 6V6 it runs at an even 250V. I messed around with cathode resistor values to hear what it would sound like biased hotter or colder, and honestly it sounds best for all three tubes right where it is now anyway. If I run the 6550 in there, it would be really biased cold, but it would run with only a marginal mismatch of the primary impedance compared to "typical operating conditions" mentioned in the datasheet examples (2500 ohms primary instead of the 1500 ohms recommended for that B+). The bias current would be really low, but I know a guy using an AX84 high octane (which I helped him build) who says his is running fine, not drawing more than 65mA plate current (well within spec of the 125DSE), and sounds really neat. I plan to try that out soon too. Hey, feel free to ask any more questions if you like, or email me directly. I'll get to you later on in the next day or two with stuff for a link from your site--thanks for the offer! I'll link you back too.
×
×
  • Create New...