should I go for broke?

[MitchK]

Hey everyone I'm building a jcm800 2203 clone, it will be my first amp that I'm building and my question is this, I was on antique electronics and I was just going to buy the PT and OTs they have as well as just JJ electrolytics, and mallory or orange drop signal caps, basically all the cheaper stuff because its my first amp and who knows whats going to happen, but at the same time looking over things the price difference between going with maybe CE electrolytics instead of JJ and something else for the signal caps (maybe those sozo caps that metroamp have or solen fast?) isn't really that much more maybe 100 difference in total if I go all out. I've also been looking at MM transformers. If all goes well I am planning on buiding a few of these for some friends and if I buy 5 transformers from them the discount isn't that bad maybe end up paying twice as much for the MM transformers than the generic ones www.tubesandmore.com have.

What do you think, would it be worth it? paying maybe 700 instead of 400, do you think I'll come out with an increase in quality that will warrant the extra spending? and also would you recommend that I first focus on spenidng more on the PT/OT than the caps?

[Tom Phillips]

Hi Mitch,
Ambitious project for a first build but doable if you have the basic skills. In reality a 2203 isn’t much more work than a Deluxe, just bigger iron and a few other parts. My first build was a 6G14 Showman and I hand wound the PT on a core salvaged from an old TV. I made lots of mistakes, but I learned a lot, corrected all the problems and eventually went on to gig with the amp and build many more.
I would recommend putting your extra money into the transformers first. you may do well to look into the Obsolete Electronics output transformer. JJs and Mallory 150 signal caps should sound fine. In addition to costing more, the exotic caps may not even sound as good to you. That debate can really open up a can of worms. You can probably find lots of discussion already posted on the merits of various signal caps. Note: “Orang drop” is a family of several different types of construction. Some better than others for a guitar amp.

If this is your first build, there will be lots to learn but there is lots of help available. Sounds like you can spare the cash for the good iron. Then you can always experiment with the caps.

Have fun,
Tom

[Bill Durham]

build stuff

Mitch

I just built an amp using the Sozos and I'm pretty happy with the tone. You can buy them directly from Sozo, might be a little cheaper than Metro. I spent about 35 bucks on signal caps, which would have been probably less than 20 for Mallory 150s..was it worth it...who knows!
BD

[MitchK]

hmm tom thats pretty interesting about winding your on transformer, its something I've always thought I'd try down the road but I suppose it wouldn't actually be all that hard if you had a core. did you do that for the OT aswell? can you recommend any resources on making transformers? I'd be really interested in this just because, as much as I do plan to go for broke on building an amp sometime I'd kinda like to just start off with a test run for cheap.

[markbul]

http://geek.scorpiorising.ca/windingtransformers.html

[Enzo]

I would suggest actually building and making 100% this amp before planning the next ones you will build for friends. FInd out what snags there will be before "saving" money on a bulk transformer buy. I would also worry about esoteric caps and stuff once you have refined your design. it is a lot more important to decide between .022 or .047 caps for tone than it is between sozo and solen.

In other words make the car run good before concerning yourself with the thickness of the chrome on the hubcaps.

[Tom Phillips]

PT Winding

Mitch,
Yes it was interesting winding my own transformer. The driving factor was cost and I had lots of time to spare compared to today. I only wound the PT and my resource was an old radio armature’s handbook that had a section on winding transformers. I see that just about all the information from that section is included in the web page that markbul refers to above. (http://geek.scorpiorising.ca/windingtransformers.html) In fact I see that several of the figures in the article are credited to The American Radio Relay League. At least one two them are the same as used in my book

I started by disassembling a PT salvaged from an old tube type TV. These used to be readily available as they were tossed out behind TV repair shops. (Some of you can guess how this dates me) I started with a PT that had the primary wound on the bottom of the bobbin so I just unwound down to the original primary and added my secondaries on top. I designed the HV winding to be used with a full wave bridge rectifier. That reduced the number of turns by half. It was a lot of work which I have not repeated since but I still think of doing it again some day. Let me know if you decide to go for it.

Regards,
Tom

[Enzo]

Nothing wrong with stripping old TV chassis. That is how I got started back in the 1950s. the hard part was convincing my dad it was OK to go out in the trash behind the Tv repair shop and grab the dead chassis carcasses. I carefully disassembled all the parts. I am sure some of those old resistors are still mixed in my parts bins.

To this day I cannot throw out an old VCR or cassette deck without stripping it all apart. I save the metric screws. Yeah, that's the reason.

[MitchK]

I designed the HV winding to be used with a full wave bridge rectifier. That reduced the number of turns by half.

THis really through me off can you explain what you mean by this? how does using a bridge rectifier change the # of windings you'd need?

This information is amazing! I read that article and its soooooo interesting. I think I'll definitley take a stab at building my own transformers, its infact somthing I've always wanted to look into but figured it would be harder. i'm very keen on the recycling aspect of it too

A piece of information that I feel I should through out here. and actually is a bit of a question for me I'm wondering about efficiency etc. Torriods are more effcient i'm told and I notice Diezel amps use them in some of the models and i always wanted to look into them, but my question is this a similar issue to say capacitor quality where using very high quality caps that might be great for audiophile applications aren't so hot for building nitty gritty guitar amps?

either way the info I wanted to share is that there is a guy named bill muller (www.mullerpower.com) who is a member of the alternative energy community who has discovered a material that is basically just black sand left over from gold minig that he calls Amorphous Polycrystalline Ferrite that I guess is extremely magnetically efficient, doens't make eddy currents, elminates hysteresis, can de-magnetize almost instantly etc, and is a choice material for cores. it would be interesting to experiment with this material as a core material for a guitar or stereo amp transformer and hopefully when i'm a bit more experienced I'll get my hands on some and try it out.

[Enzo]

I think what he had in mind was that if you have a 300VAC winding running to a full bridge, it would be equivalent to a 600VAC center tapped winding feeding a dual rectifier with the CT grounded. SO by changing from CT to full bridge, he reduced the voltage the transformer needed to produce, hence the number of turns on the secondary. At least that us how I read it.

[Tom Phillips]

Full Wave Bridge

Re: "...by changing from CT to full bridge, he reduced the voltage the transformer needed to produce, hence the number of turns on the secondary."

Yes, that's exactly why I used the FW bridge. The laws of physics still apply Mitch so you don't get something for nothing. I had to use larger gauge wire but that was well worth the reduction in turns I had to wind. There are good web tutorials out there but I can't seem to find any at the moment.

Toroids are an option. There are pros & cons. Sorry that I must get going on a project so don't have time to get into it now. Check out the following link. The company sells kits and instructions that allow you to wind your own toroid PT. There's lots of other good info on their site too.
http://www.toroid.com/standard_trans...ormer_kits.htm

Cheers,
Tom

[Bill Durham]

toroids

One thing I have heard about them is they can produce a huge spike when turned on if the AC is out of phase to the source AC from previously being on. I hope that made sense! This is how it was explained to me from a friend that was winding toroids for solid state power amps. If the source AC was going negative at the time when you turned the amp on, and the AC was going positive when it was turned off...the toroid would generate a big spike into the rest of the power supply. Somehow the core of the toroid would store the phase or something. Anyway, you had to allow for that possibility when you designed the components that followed.

FWIW
BD

[Tom Phillips]

Line surge when torioid PT is switched on

BD,

My understanding is that the core remembers the phase of the AC line signal when the power was last turned off. If the phase of the AC line is different when the power is next turned on, then the toroid transformer draws a large surge of current from the line supply. This happens momentarily at turn on. The scenario is basically what you described except I don't think there is a spike generated out the secondary.

I have seen a few forum discussions on this subject. I guess that some people have experienced nuisance fuse blowing. I have never had that problem. So go figure. Overall, I don't think it's a big problem.

Regards,
Tom

[Bill Durham]

toroid xformer

Tom,

yeah, what you said!

I think that there is some physical stuff too when the AC is out of phase with the toroid when you turn on.. like a pretty big shake of your equipment.

I could be wrong though

BD

[Ray Ivers]

Tom,

Here's what Plitron has to say on the toroid-inrush-current subject:

---

"Inrush Current

The high remanence of grain oriented silicon steel, lack of air gaps, and the excellent magnetic properties of toroidal transformers can cause a high magnetizing current on turn on, limited only by the low impedance of the primary winding. However, the duration of the inrush current is rarely longer than a half a cycle."


Ray