s.s. power amp, for re-amping 1 W. tube amp.

[tonequester]

tonequester here,


Greetings to all ! I have been looking for a s.s. amp kit that I coiuld be able to re-amp a 1 W. tube amp through for increased volume. I've found a few and benefited from much input from the forum. none of the kits so far has "made the grade",for one reason or another. I believe that I may have stumbled onto the right kit and would appreciate any input, advice, or opinions on the subject. The kit Are sold ny Xkitz.com. They supply a power supply kit as well, leaving me only to locate a suitable transformer. The amp kit is model XAMP-M1,Audio Ampifier,50W,Mono,with Optional filter(this IS included). Input Impedance-51K, Power supply-6V--26V. It is "driven" by
Low Power JFET Input OP-Amps--TL062, and TL064. Heat sinks are provided. One of the important things about the kit for my use is the flexible audio input, Line-Level(for guitaretc.)' and Speaker level for boosting the power of any other audio source. A 40 component build. it includes a clipping indicator L.E.D., and one can customize the Pre-amp Filter frequency. It comes pre-set for flat response which suits my purpose. It uses very little power. it can actually operate it at reasonable volume for over 12 hours on a single 9V. battery. The power supply kit is model XAPS-50, regulated D.C, power supply, with either variable or fixed output-depending on assembly option. The output voltage is 3V.--36V. It includes large filter caps for clean output, and is a beginner level kit of 14 components. I will need to locate a transformer to with a 26 V.A.C. secondary, rated at 50VA. That's most of what I have. More can be found at Xkits.com. The two kits, plus tax add up to $42.41 not including shipping, or the transformer.
It's a little more power than I had originally planned for, but would certainly take care of my needs without having to push the finished unit. the price is also a little higher than I planned to spend, but there are not as many 20-30 W. kits, In mono out there. At least this one even mentions it's use with guitar. any and all feed-back is very welcome and appreciated ! Thanks, tonequester. (OH, I know there might still be need for attenuation and matching of Z, and am working on this also.)

[Austin]

Ewww... Solid state....

[tonequester]

tonequester here.


Hey Austin ! Bro'....I didn't mean to "tork" you out. Believe me, there is no more dedicated tube man in the state of Kansas than yours truly. This whole s.s. thing is more experimental, and a learning thing for me than anything else. I'm not really even expecting acceptable results. If everything does somehow work out to my satisfaction that my tone is intact at a higher volume, no one will be more surprised than me. What I'm trying to cobble up here is basically a very portable substitute to mikeing up to a P.A. It's something to experiment with "on the cheap". I'm still doing my first all tube build. you'll have to pardon me for going the kit route on my first build, but I can do it reasonably cheap, plus I lack the knowlege and experience of almost everybody else on this forum. The kit's going to be very low powered, although it should be twice as loud as my practice "tuber". It will be the exact type of amp that I've always wanted to have : Class A,cathode biased, S.S., and I do love those EL-84's. I am definitely headed towards a build of an all tube, hand wired, 50-60 W. head, to run a 4X10 or 12" cab. I have to stay busy being "retired", so I'm taking my time in saving for that one, even as I build other stuff to continue to gain knowlege and experience. I want to be in "peak shape" when I tackle the "amp of my dreams". If I screw something up, I want it to be $40.00 worth of s.s., rather than hundreds on my honey to be. When i get there, you can bet I'll be turning to guys like you for plenty of input as how to maximize my results. you seem not only to have much knowlege and esperience, but like I used to be back when I was working, a master of scrapping, scrounging, and generally locating the good stuff, at good prices and even free. My hats off to you and all the others like you on this forum. I will say this, even when I just practice, it's tubes all the way. When my Blackstar was in the shop, all I had was an old Fender 15W. s.s. practice amp(a throw away at that). I almost gave up practicing because I couldn't stand the horrible tone. TUBES RULE !!! Always have....always will ! Have a great day, brother in arms ! tonequester.

[loudthud]

I looked at the schematic for that XAMP-M1 and it can maybe make 12W at 8 ohms. The rail voltage is limited by the rating of the TL072 driving a pair of TIP 31/32 transistors (36V). There is no short circuit protection. The heatsinks are very small, you would have to use a fan for any serious use.

Link to amp manual: http://www.xkitz.com/documentation/X...str_Manual.pdf

Link to PS manual: http://www.xkitz.com/documentation/X...str_Manual.pdf

Link to Vellman kit I suggest: Velleman, Inc.

Use the Vellman kit with a 36VCT 100VA transformer and the power will be about 25 to 30W at 8 ohms.

[tonequester]

Greetings loudthud.


I just went over the manuals for the XAMP-M-1 which i downloaded earlier today. I hadn't had the chance to check them out thoroughly earlier. I have to say i now have misgivings about the circuit also. it "irks" me that they even advertised it as being suitable for guitar use. Of course I'm doing something a little more radical than just run a guitar straight through it. I have to keep that in mind. I had trouble with the Velleman site the other day. I don't know if the site was down. or my side was screwy. My server is notorious for being overloaded and I have trouble at times from my end. I just checked the thread and it gave me the whole kit selection. Are you refering to the K4003, 2 X 30W. amp kit ? You've got alot more experience judging what can be done with a particular circuit than I have. I didn't see anything in mono configuration that had much power advertised. I'm sure that a 2 X mono
circuit could be configured to output one channel, I just have never had any experience with it. If I could go with this kit, and use a 36VCT 100VA transformer, 25-30W.@8 Ohms would fit the bill. If I'm on to the wrong kit, please give me a holler so I get this straight. From what I have gathered Velleman is a very well respected outfit. Thanks for checking up on me. I appreciate and respect your opinions on this. tonequester. P.S. I'll download whatever they have on the K4003 as I double check the site to see if I'm missing something.

[tonequester]

tonequester here again.


loudthud, this time when I used the link to Velleman, a different page appeared. It showed the K8060 Discrete Power Amplifier/ 200W. At $38.20 no problem.
I assume THIS is the amp you had in mind. The description sounds excellent. I take it that using the 36vct/100va supply instead of the recommended 2 X 25-30 vac/120va supply
will work o.k. I located your recommended transformer at Mouser for $27.57(Hammond). The pre-drilled heat-sink HSVM100 called for will beg a little further searching the web for a good deal. I've found it for-$38.39(more than the kit), and for $23.95 with a quick search. I downloaded the schematic and the parts placement pages for now, to look over. I have to say it's going to be more expensive than I had thought, but this kit is obviously "head and shoulders" above anything I've yet seen. If the whole idea works out to plan, I would rather be "well built"
than under-built. Just being a Velleman gives me re-assurance. I gotta hand it to you, you sure can pick 'em ! Sorry about the confusion before. I don't know why this kit didn't come up the first time. I got the home page I believe, and this kit is not listed under "kits" when selected from that page. The only thing I saw that remotely looked usable was the 2 x 30W. kit I mentioned earlier, and I must admit now that I had my doubts about that one. I hope I'm "on the right page" now. Thanks for all of your help and patience. tonequester.

[loudthud]

It's the K8060. Single channel called "200 Watt". The design uses +/- 40V rails which would give about 70 watts at 8 ohms. It uses a single pair of TIP142/TIP147 output transistors. With +/- 25V rails (from a 36VCT transformer) should give 25W to 30W at 8 ohms.

[R.G.]

A couple of observations:
- re-amping a small tube amp through a SS amp is no better or worse than the semi-universal practice of miking a small stage amp and sending it through the PA.
- for powers up to 50-60W, it is hard to do better than a $5.00 LM3886 power amp module and a handful of parts. They're quite reliable, self protecting, and also widely used in the DIY amp builder community. There are many small kits/PCBs.
- kits for amps with 200-1000 (not a typo...) using discrete parts and lots of heat sinking are available; in the LM3886 and these kits, the truism that the power supply costs most of the money comes home with a vengeance

[tonequester]

Greetings loudthud.

Tonequester here. I am glad that I'm finally on "your page" concerning this kit build. I am making my final order of parts which will complete my "over-haul" of my
guitar. When I get the parts this next week, I should have it done in a couple of days. This s.s. kit is my next project. I had originally espected it to run me perhaps $30.00-$40.00.
I now realize that this was way off mark. The kit and transformer will run me $65.77, not including shipping. Building a good enclosure, in the manner of an amp head will no doubt run another $20.00. I'm wondering your opinion on using a "home-made" heat-sink, in combination with a muffin fan to save a good $20.00 on the recommended heat sink. I have located
fans in the $5.00 range which use between 2-5ma. I don't know if it would be as effective, and I don't know how critical the 2-5ma would be to the circuit. These are d..c. fans at different voltages.I do have access to a brother who is a metal working expert, with access to necessary tooling and lots of metal, including aluminum. In any case, it will take me a couple of weeks to gather the funds to place the kit order and the transformer order, so I can start the build. Being at the end of the month I am always looking forward to my monthly check on the 3rd.
If you can find time, mull over the heat-sink/muffin fan thing. I have to also come up with some extra cash to build the attenuation circuit that Chuck H was good enough to supply me. it consists of a 50W. x 30 Ohm power resistor, potentiometer, and panel meter. I can either make it stand alone, or incorporate it into the input of the amp. I will be taking the input from the tube amps speaker output. Once again, I truly appreciate the time that you have given in posting, plus the time you have spent checking out leads for me, not to even mention giving my project the benefit of your expertise. Sincerely, tonequester.

[R.G.]

IMHO, getting a large passive heat sink will be a better option. there is a guy who's been selling heat sink extrusion on ebay for several years now. He'll sell you a foot of 8? 9? wide fins-on-one-side stuff for about $30, and may IIRC cut that into a couple of 6" long slabs for you for a nominal fee. This big a sink will keep any reasonably-sized power amp cool. Also, with a biggish finned sink available, you can make the attenuator be metal-housed power resistors mounted to the second heat sink slab and do a good cooling job on it, also without a fan.

[R.G.]

So I went and looked and he's no longer selling on ebay.
However, here are some great alternatives:
A couple of these:
heat sinks

One of these perhaps band-sawn across the fins:
wide, flat heat sink

Or go look at the sinks in the Antek store - and their power transformers.
Antek store

[tonequester]

tonequester here.


Greetings RG, and good to "meet" you here on the forum ! Thanks for the inside tip. I'll check it out. I never thought about the laod resistor, but it makes perfect sense
to provide cooling for it as well. I appreciate your interest and your quick response. All the best to you and your projects. tonequester.

[Tom Phillips]

Tonequester,
Another source for heat sinks is old 1960's & 1970's Hi Fi amps and receivers. I am talking off brands here that are usually just tossed out when they stop working or someone finally gets around to cleaning out their old junk.
They will often have one to four heat sinks similar to the one shown in RG's first link. They can be found sitting on the curb with the trash, in thrift stores which may eventually mark them down to $1 or less just to get rid of them and at fundraiser bazaars run by the local Ham club. Tip: At the end of the fundraiser bazaars they often announce that everything left (except for a few select items) is free, take it now or it's going in the dumpster.
Tom

[tonequester]

tonequester here.


Hey Tom ! Good to hear from you. It's a good idea on the heat sink. With the size of my family, I might do well to call around and see if one of them has something, I also know several thrift stores in my area I can check. I myself, never had an amp with such a big heat-sink. I once had a 200W. Sansui amp but the heat-sinks weren't half that size. It finally "blew" a channel. It was an open power transistor, the first electronic thing I had ever fixed(with much advice by a nice tech). Ironically, the real problem, according to the tech was
that Sansuis were notorious for their poor heat-sinking. He told me how to check it, and where to get the part. $18.00 and an hours worth of work and I had a like new stereo amp. After a
similar experience with a Fender Princeton, I was hooked for life. My only regret...no schooling when I was young and able. This forum and folks like you are helping me bridge the gap.
Thanks for the multiple tips on heat-sink procurement. Sincerely, tonequester.