jane said:
This is a very common misconception. The Vox AC's are all class AB, the marketing people either lied, or just didn't know the difference. (Kinda like Mesa!) Here's a study which shows this: http://www.aikenamps.com/VoxAC30classA_2.html
For a small SE guitar amp I like the sound of the Hammond 125CSE over the Edcor for one reason, all of the different secondary taps. This allows you to pick the impedance that gives you the sound that you want regardless of what the tube manual says. I have built amps that use a switch that allows the use of different taps. Don't flip the switch while playing!
Using a P-P transformer for SE will cause the transformer to saturate on strong bass notes if it is not oversized. If you push the amp into clipping and transformer saturation a lot the tube current will increase dramatically leading to short tube life (especially with the EL-84). It does sound different in a distorted kind of way. If you try this, crank the amp to eleven and wail on it while watching the screen grid wires in the output tube. If they glow to the music, something bad will happen eventually.
For a small (5 watt or so) guitar amp I use the Allied Electronics 6K56VG power transformer. It is $38 and puts out about 320 volts using a tube rectifier. For bigger amps (50 watt P-P) I use their 6K7VG. $43, about 410 volts with a tube rect, and over 450 with SS. www.alliedelec.com
I use a switch to flip between tube and SS rectifiers (like the Mesa dual rectifier). A true class A SE amplifier does indeed draw a constant (average) current during operation from idle up to the power limit. I have observed this on many SE audiophile HiFi amps. As soon as the amp distorts, you are no longer in class A and the current becomes dynamic. In a guitar amp situation pure class A happens only in textbooks. Just try putting an old analog current meter in series with the output tube and playing the guitar. The needle dances wildly.
In a guitar amp there is a difference between tube and SS rectifiers, and a noticible difference between different tube types. I have been known to use a 5Y3 in place of a 5U4 in a 40 watt P-P amp to get a long sustain on overdriven notes. The poor tube really doesn't like it, so I don't do it often, but I am still using the same crusty old RCA 5Y3.
I was going to point to the link to my "turbo champ" amplifier schematic on my web site, until I realized that the link is broken. It is a Champ based design that I did a few years ago, but the concepts can be applied to many designs.
This should be the first weekend that I have free in over a month, so I will try to fix the web site.
Using a P-P transformer for SE will cause the transformer to saturate on strong bass notes if it is not oversized. If you push the amp into clipping and transformer saturation a lot the tube current will increase dramatically leading to short tube life (especially with the EL-84). It does sound different in a distorted kind of way. If you try this, crank the amp to eleven and wail on it while watching the screen grid wires in the output tube. If they glow to the music, something bad will happen eventually.
For a small (5 watt or so) guitar amp I use the Allied Electronics 6K56VG power transformer. It is $38 and puts out about 320 volts using a tube rectifier. For bigger amps (50 watt P-P) I use their 6K7VG. $43, about 410 volts with a tube rect, and over 450 with SS. www.alliedelec.com
I use a switch to flip between tube and SS rectifiers (like the Mesa dual rectifier). A true class A SE amplifier does indeed draw a constant (average) current during operation from idle up to the power limit. I have observed this on many SE audiophile HiFi amps. As soon as the amp distorts, you are no longer in class A and the current becomes dynamic. In a guitar amp situation pure class A happens only in textbooks. Just try putting an old analog current meter in series with the output tube and playing the guitar. The needle dances wildly.
In a guitar amp there is a difference between tube and SS rectifiers, and a noticible difference between different tube types. I have been known to use a 5Y3 in place of a 5U4 in a 40 watt P-P amp to get a long sustain on overdriven notes. The poor tube really doesn't like it, so I don't do it often, but I am still using the same crusty old RCA 5Y3.
I was going to point to the link to my "turbo champ" amplifier schematic on my web site, until I realized that the link is broken. It is a Champ based design that I did a few years ago, but the concepts can be applied to many designs.
This should be the first weekend that I have free in over a month, so I will try to fix the web site.
Those Allied Transformers are G R E A T !
I had one a bit back, mine is discontinued model. Looking at them you could swear they are actually Hammonds. Rock solid construction and great performance.
kevinkr:
I agree,
Though we all can pretty much agree that it can be done slightly cheaper, and the end results will vary some.
Following the AX84 P1 to the letter really does offer a high success percentage factor. A lot of guys spent a great deal of time on that AX84 project and the majority of guys who have built them have been very happy.
Lord knows I tend to stray from the box a bit to often, And my posts end up being about "how can I fix this" 90% of the time.
Though I have gotten a little better
🙄
Trout
<snickers> I want to build a turbo champ 😀
It's pretty easy to tell how much change in current to expect. Just look at the data sheets. They almost always list zero-signal current and max-signal current in the chart of typical operation. Don't forget to include screen current along with plate current.
well I think your right, I'm going to stick with the hammonds. For a few reasons: they have already been designed into the amp and would make it easier for me, they have multi-taps for different ipeadances , and their reasonably priced and not to mention have been around for years and years 🙄
I think I oughta stick straight to the book for now since this is my first real build, even though I know enough to make small modifications and stuff , I'd like it to turn out ok the first time 😉
I'm still trying to decide weather or not to use a tube or ss rectifier... I might just go with a tube rectifier since it wont raise the price too much, and it looks kinda cool to 😛
I think I oughta stick straight to the book for now since this is my first real build, even though I know enough to make small modifications and stuff , I'd like it to turn out ok the first time 😉
I'm still trying to decide weather or not to use a tube or ss rectifier... I might just go with a tube rectifier since it wont raise the price too much, and it looks kinda cool to 😛
Cost savings
Find an old guitar amp & convert it to what you want. If you can not afford a $25 audio transformer, you may never complete the 'from the ground up' project in a timely manner.
Find an old guitar amp & convert it to what you want. If you can not afford a $25 audio transformer, you may never complete the 'from the ground up' project in a timely manner.
finding an old guitar amp would be next to impossible for a low price that I can afford. I'm going to make $50 a week orders I think, that should get it done fairly quick and allow me to take my time on each part of it and not rush it 😉 I can afford it, I just want to see how cheaply I can make this with decent parts. But I'm still sticking w/ the hammonds..
caps, resistors
ok, I'm ordering the parts now. I've decided to build the p1 high octane. I have a few questions...
Orange Drops , Mallory 150's, or cheap poly caps?
Filter caps: 40uf ok? Does it matter what brand? Was thinking atomlytics... Btw what do you think about ordering a multicap? Not much price difference... might be awkward mounting.
Resistors: Carbon comp ( I've heard they tend to wander off their values as they get old) Carbon film , or metal oxide?
I went ahead and got the hammond 125dse OPT, and 269ex PT.
ok, I'm ordering the parts now. I've decided to build the p1 high octane. I have a few questions...
Orange Drops , Mallory 150's, or cheap poly caps?
Filter caps: 40uf ok? Does it matter what brand? Was thinking atomlytics... Btw what do you think about ordering a multicap? Not much price difference... might be awkward mounting.
Resistors: Carbon comp ( I've heard they tend to wander off their values as they get old) Carbon film , or metal oxide?
I went ahead and got the hammond 125dse OPT, and 269ex PT.
On A Budget?
I get all my guitar amp caps from Justradios.com.
http://www.justradios.com/
Great prices and fast delivery. 😀
I get all my guitar amp caps from Justradios.com.
http://www.justradios.com/
Great prices and fast delivery. 😀
You can indeed find old amplifiers for cheap. Something like an old Traynor Bassmate can be had for not much and is very sturdy, has lots of room inside, and is darn friendly to experimentation. And fi you are going to rebuild to your own specs, who cares if it was a sucky amp in its former life. An empty shell is an empty shell.
The beauty of an old amp is that even if you gut the thing to build your own circuits, the transformers a realready there and mounted, the sockets are all mounted and already have the heaters wired. And many of the parts on the part board can stay the same. Chancces are an old amp will have 100k plate loads for the 12AX7s for example. Many circuits you might try to duplicate also have 100k plate loads, as an example. For that matter, the front panel will be drilled and labelled for the controls. Most of the controls can probably be retained for their original function too.
DOn't worry about carbon comps wandering. Do you really think the value of the resistors in it will still be a big issue to you 20 years from now?
My personal advice for a first amp build project is not to worry about the esoterica. It is sorta like building a back yard go-kart and worrying about the suspension performance at 100mph.
Once you have some experience building and working in the amp circuits, then is the time to start worrying about the very subtle differences in brands of cap.
The beauty of an old amp is that even if you gut the thing to build your own circuits, the transformers a realready there and mounted, the sockets are all mounted and already have the heaters wired. And many of the parts on the part board can stay the same. Chancces are an old amp will have 100k plate loads for the 12AX7s for example. Many circuits you might try to duplicate also have 100k plate loads, as an example. For that matter, the front panel will be drilled and labelled for the controls. Most of the controls can probably be retained for their original function too.
DOn't worry about carbon comps wandering. Do you really think the value of the resistors in it will still be a big issue to you 20 years from now?
My personal advice for a first amp build project is not to worry about the esoterica. It is sorta like building a back yard go-kart and worrying about the suspension performance at 100mph.
Once you have some experience building and working in the amp circuits, then is the time to start worrying about the very subtle differences in brands of cap.
My first go cart was built out of an old 60's MTD lawnmower completly stripped down. Had solid bearings in the front and that booger would get up to 30mph running from a pushmower engine w/o a gov'ner! 😀
I think you have a good point about the resistors...
but I'd still like to know what your reccomend ( like for the ones that need to be 1w. I was thinking metal oxide)
Also, its not much of a price difference between mallory 150's and cheap poly's, and its also not much of a difference in price between orange drops and mustard caps. The over all cost is a factor of a few dollars, so I'm willing to experiment.
Just would like to know your personal preferences on coupling caps/ tone stack caps?
BTW, I'm trying to order this in one or two orders , and combine shipping. I'm ordering from www.tubesandmore.com and tubedepot.com. Most of the parts from tubesandmore, a few odd cap values and the tube sockets from the tubestore. If I have enough left over I might just throw in a Jensen c10R😎 😉
If you're going to build an AX84 project, how come you don't ask such question son the AX84 forum?
I thought there was a target budget based on the original topic/posts. Originally, transformer price was an issue.
Enzo has a great point on grabbing an old amp, Even if it needs gutted and switched to a circuit you wish to duplicate.
Though Mallorys caps are fairly priced and of reasonable quality, I still use the CDE caps just radios sells, Reason? I buy a lot, regularly, .10cents here and .35cents there adds up quick.
Genuine sprague orange drops will be close to mallorys in cost. But Genuine Phillips Mustard Caps?? If you have a source that is competitive in cost to Mallory, PLEASE tell me where.
The Guys on ebay pay up the yingyang for those things to clone and restore old Marshalls.
If you want the amp to sound like the clips posted on the AX84 site, I would follow the playbook they already have posted on that site.
As Merlinb mentioned, they have a forum there specifcally on those amps, Most of the contributing designers are very helpful and very active on that forum.
Though I admit, When it comes to anything Tube Audio, I feel the guys here are Cream of The Crop.
Trout
Others that read this & have a few bucks
An amp for 5-6 watts would be a pair of PP 6V6GT triode connected into a vintage Jensen Alnico P12N. So sweet sounding with some Mullard 12AX7 long plates, it would about outplay any clean amp.........
You said Marshall? Use the Bogen amp first input preamp tube design with that wierd volume pot configuration. I never seen a guitar amp schematic with that design.
Yep, that is why some of the old Bogan amps shock many guitarists with that articulate crunch at all volume levels (not a mud slinger here).
An amp for 5-6 watts would be a pair of PP 6V6GT triode connected into a vintage Jensen Alnico P12N. So sweet sounding with some Mullard 12AX7 long plates, it would about outplay any clean amp.........
You said Marshall? Use the Bogen amp first input preamp tube design with that wierd volume pot configuration. I never seen a guitar amp schematic with that design.
Yep, that is why some of the old Bogan amps shock many guitarists with that articulate crunch at all volume levels (not a mud slinger here).
well I recently made some money cleaning, repairing, setting up and doing some MAJOR rewiring of several stereo systems my neighbor has. I now have about $210 to spend and I already have a cabinet built.
so far I have prices around $170 minus the jacks and knobs.
Merlinb
didn't check to see if they had a forum, thanks!
Trout: here are the mustard caps http://www.tubedepot.com/sozo.html
Their not NOS, their repros but supposed to come within .1% of the originals. Kind of pricey but around the range of the orange drops, and for a small amp like this not much of an investment.
forgive me I seem to be having a brain fart... what are cde caps?😕
so far I have prices around $170 minus the jacks and knobs.
Merlinb
didn't check to see if they had a forum, thanks!
Trout: here are the mustard caps http://www.tubedepot.com/sozo.html
Their not NOS, their repros but supposed to come within .1% of the originals. Kind of pricey but around the range of the orange drops, and for a small amp like this not much of an investment.
forgive me I seem to be having a brain fart... what are cde caps?😕
ThSpeakerDude88 said:
It's a bloody good forum too, much better in design, and for usable answers! (on guitar applications that is)
Oh yeah, like the originals were ultra-high quality super-caps! 🙄 And like you could tell the differenc between a Marshall loaded with Mullard Mustards, and one with bog-standard polystyrenes.
Those are not Phillips Mustard caps, Though Sozo makes a decent cap, (I bought them once), and agree with Merlinb, They are not of any better sounding,
EXACTLY correct!
BUT what I am saying is, Die hard Marshall amp guys (which I am not) Pay dearly for Real NOS Mustard Caps. If I found a big cache of them especially in the common Marshall or Hiwatt amp values, I would have them instantly listed on ebay cash in on their value, Then use the cash for The Mallorys or CDE's., Take the extra earned cash, and soak it into the best iron I could afford and still take my women out to dinner.
Example: I got 4 NOS in package Sprague Bumble Bee .022uf/400V caps,
I listed them in the gibson guitar section on ebay, Got $197.50 for 4 caps that IMHO had little value to me. I got them in a huge box of old junk for 3 bucks at a public auction.
Will those make the guys guitar " Sound" better? I doubt it.
Trout
geez man I need to look for stuff like that! 🙄
Ok seriously, why would you pay for old capacitors? Their values would have drifted and / or they would not have as much life in them because of age. New capacitors have much tighter tolerances than most old ones and are made better. Plus the added bonus of being new.... duh
🙄
I feel sorry for people that pay that much money for something like that.
All things aside, if they really don't sound much different I will get the orange drops or the mallorys . I did read somewhere that the mallory's have a slight high end roll off to them that gives the amp a champ like sound... but again that could be hype, what do you think?
I think the choice is down to mallory vs sprague. I'm not just doing it for the sound ( I know thats all that really matters) but also looks- I will be entering this in the county fair for my electronics project this year and want it to be "show" nice. I might add a plexiglass window on the back wood panel that covers the bottom of the chassis. I like to make my circuits look as good as the external stuff 😉
BTW I will get the digital camera out and take some pics of the cab soon!
Ok seriously, why would you pay for old capacitors? Their values would have drifted and / or they would not have as much life in them because of age. New capacitors have much tighter tolerances than most old ones and are made better. Plus the added bonus of being new.... duh
🙄
I feel sorry for people that pay that much money for something like that.
All things aside, if they really don't sound much different I will get the orange drops or the mallorys . I did read somewhere that the mallory's have a slight high end roll off to them that gives the amp a champ like sound... but again that could be hype, what do you think?
I think the choice is down to mallory vs sprague. I'm not just doing it for the sound ( I know thats all that really matters) but also looks- I will be entering this in the county fair for my electronics project this year and want it to be "show" nice. I might add a plexiglass window on the back wood panel that covers the bottom of the chassis. I like to make my circuits look as good as the external stuff 😉
BTW I will get the digital camera out and take some pics of the cab soon!
Perfect Example,
http://cgi.ebay.com/2-x-SPRAGUE-BUM...5QQihZ008QQcategoryZ71573QQrdZ1QQcmdZViewItem
And those were USED lol Item number: 9729042295
142.50 for 2 used caps.
I personally did not like using orange drops(though I do occasionally use Nos spragues). They do sound a bit different and the lead locations are weird lol. Mallory and CDE are so much alike I would not be surprised if the same company is rolling them both.
Trout
http://cgi.ebay.com/2-x-SPRAGUE-BUM...5QQihZ008QQcategoryZ71573QQrdZ1QQcmdZViewItem
And those were USED lol Item number: 9729042295
142.50 for 2 used caps.
I personally did not like using orange drops(though I do occasionally use Nos spragues). They do sound a bit different and the lead locations are weird lol. Mallory and CDE are so much alike I would not be surprised if the same company is rolling them both.
Trout
http://www.tubedepot.com/vinoip.html
looky lol 😛
CDE makes black cats am I right?
Really stuck on this one here... oranges or bananas? I'd like to go with the mallorys because their smaller and easier to mount, but I don't know which sound best.. you know I could always get half of them orange drops and half mallorys, because the hi octane uses I think 4 .022 uf caps, two in the tone stack and two coupling caps. I could always swap them around.
looky lol 😛
CDE makes black cats am I right?
Really stuck on this one here... oranges or bananas? I'd like to go with the mallorys because their smaller and easier to mount, but I don't know which sound best.. you know I could always get half of them orange drops and half mallorys, because the hi octane uses I think 4 .022 uf caps, two in the tone stack and two coupling caps. I could always swap them around.
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