Advice needed on first cab build. Smaa single speaker type.

[überfuzz]

If we cut to the chase, it seems you're looking for an economy class amplifier to build. Scavenge the local craigs list and see if you can find one or two amplifiers in non working order. This way you'll have more then enough to tinker with and you'll probably end up with something nice.

[tonequester]

tonequester here.



Greetings uberfuzz. Thanks for the reply. I hadn't even given Craig's list a thought in this matter. One never knows 'til they try. I'll check it out to be sure.
I'ts nice to make your aquaintance of the forum. Thanks for the tip and have a great day ! tonequester.

[überfuzz]

Greetings uberfuzz. Thanks for the reply. I hadn't even given Craig's list a thought in this matter. One never knows 'til they try. I'll check it out to be sure.
I'ts nice to make your aquaintance of the forum. Thanks for the tip and have a great day ! tonequester.

Well, you probably have your priorities sorted. I always keep an eye out for amplifiers with an owner that has given up on them. But on the other hand, a kit is a sure way to get everything needed in one blow. Good luck with your first build!

[tonequester]

tonequester here,


Greetings Chuck. I hope that all will excuse me if this isn't a proper way to post. This concerns what has been bantered about on this topic. I have found out how to receive personal messages on the forum, but as yet, have not figured out how to send one. Anyway, I have found the s.s. kit amp that I am going to build. Thanks to loudthud, I will be ordering a Velleman kit, model-K8060,Discrete power amp, 200W. Loudthud has taken the time to "tweak" the circuit, with a ct transformer rated A.C. to 36v.a.c., 100VA. The circuit is based on Epitaxial Darlington transistors. The 200W. is misleading. That's "music power"@4 Ohms. It's 100W. RMS@4 Ohms. I will be using 8 Ohm speakers. By the time I buy the kit, the transformer ,the heat-sink(more expensive than the kit), and what is needed for a decent enclosure, I'll be going over the $100.00 mark easily. However, it should be very robust, and suit my needs. I am still going to utilize the attenuation circuit with panel meter that Chuck H has been good enough to outline for me. The first part of this circuit is a load resistor(power type)
which Chuck suggested in value as being 22 Ohms/50W. I am wondering about the 50 W. value. i have finally received my HT-1R from the shop(brand new), and this time they saw fit to provide me with a proper manual. I now know that it's 1 W. output is RMS. So I guess my first question is, would one need the load resistor to be rated as high as 50 W. Please,pardon my ignorance in this. I have never done this complex a project(for me). I also wonder if/how the s.s. amps own input impedance figures into this. I ASSUME it doesn't. I think that I am right in thinking that a decent panel meter would not constitute a load worth worrying about. I have always wanted to take the output of the HT-1R directly from the speaker output. One reason for this is that the speaker out jack on the back of the tube amp is rated 4-16 Ohms. It seems to me that there must be considerable difference in that output and the signal from the speaker wires. If anyone has any opinions on my ponderings, as I get the cash together to begin, I would appreciate hearing them. The attenuation circuit is basically tube amp input to load resistor,
then governed by a potentiometer, through the panel meter, through a diode protection circuit, and finally into the s.s. amps first stage. Thanks to loudthud, and Chuck H, as well as many others who have given me advice concerning this project. Best Wishes to Everybody !!! tonequester. P.S. The thumbnail of Chuck H's attenuation circuit can be found in this collection of post and replies under Chuck H-"I think your talking about the Ultimate...".

[Chuck H]

Ok.... That amp is only a power amp. So any volume control must happen to the signal your putting into it. That is, there is no pre amp for processing like EQ and volume. Now...

Of course you don't need a 50W resistor for your little amp. But, is this project ALWAYS going to be exclusive to your 1W amp??? The resistor rating assumes not. My idea was that you could plug the speaker output from almost ANY amp into your new project and then use it as either an amplifier OR an attenuator. In other words, you could plug in your HT-1R and make your HT-1R a 70W amp OR plug in a 50W amp and make it a 1W amp if you wished. In light of the "discrete" nature of the amp your going to build, you could take another route. Build the power amp as planned, but also build an interface box. As it happens, panel meters operate on wattage. And the input to your power amp is only dependent on voltage. Setting up a meter to detect voltages in the mV range would require another amplifier. Albiet a simple one. But it complicates the project. So the interface box might be an easier, less expensive and in light of the amp your going to build, more versitile. You could run the interface into effects or EQ's and such as well as feed any other device besides your new power amp. I think this could be a very useful tube amp tool for a tinkering musician.

The "clip indicator" isn't really a clip indicator, but rather an indication of when the amount of signal leaving the interface is likely to clip the input of another device. So you would adjust "voltage divider 1" by turning up the sensitivity until the clip indicator blinks and then back down the sensitivity little. After that the volume control (which is another voltage divider) can manage the signal strength appropriately from zero signal up to the selected output (line or low). The protection circuit would be set up to clip any voltage above about 2VAC for 'line level' and 500mVAC for 'low level. Obviously this will still allow you to clip the input of a following device. But it will abate gross mistakes.

I could even work up a schem with circuits and values if you like. I actually have fun with that sort of thing. The parts should be very affordable.

[tonequester]

tonequester here.


Hi Chuck ! I was in no doubt that the 50W. resistor was needed. I would have sent you a personal message, but I haven't figured that out yet, here on the forum. I just found out that I had some personal messages. I hope that it wasn't a problem to post this way. I'll figure out the personal message thing a.s.a.p. I was short sited on the resistors value.
I had not given thought to the possibilities, but I get it now and it is a great idea. The interface box block diagram makes good sense. I'd be very willing to send you $20.00 for your design.
Your time is worth it and more. I can see that the circuit wouldn't have to be expensive. I do plan to build a "life-time amp" at some time, after I do the simple MOD 102 kit build. I figure that if I do a good job on that, I might even be able to sell it off and put the money towards a more complicated build. I'm kind of into "one step at a time" these days, and I always have to consider saving up the cash for what I will eventually wish to build. If the s.s. thing works out as I hope, it might well be a part of the picture with my "life-time" build. If you don't want the twenty, you could donate it to the forum.....always a good investment. This "project" has taken on a life of it's own. This has happened to me before. What I don't lack in imagination, I do in knowlege. You and a few others have been quite good to me and my schemes on this forum in sharing what you know. I print off all of your replies and thumbnails for reference and study.
I would be a lot easier to work with if I wasn't so new to the whole computing thing. I hope to catch onto the forums "extras" in time, and get myself set up to be able to share photos of
the projects that I complete with the help of the forum. My last order for the upgrade/modification of my guitar is in. The next project is the s.s.amp and the interface box. Please take your own time in designing your circuit. Time is one thing(God willing) that I DO have. For the average performing guitarist, the "clip indicator" could be a real winner. Most of the player's I've met over the years have less on the ball electronics wise than I do. That's one of the main reasons that I got into it to begin with, and continue to make the attempt to learn more. You, loudthud, JM, and some others have made that much easier than it was before I joined this forum. If you are not a design engineer, or an electronics teacher of some sort, you should be. Maybe you were, or are. Chuck H works for me. Give me a holler when you wish, by whatever means, I always get the message. Well, you know what I mean. I believe that this project is SET ! It ain't built yet, but I will say that assembly is one area where I am at my best. They actually used to pay me to do some of that. I wish I'd had you there to tell me just exactly
why and what I was assembling. Thanks for all of your ideas, advice, and those excellent block diagrams. My best wishes for you. sincerely tonequester.

[Chuck H]

Most of the player's I've met over the years have less on the ball electronics wise than I do. That's one of the main reasons that I got into it to begin with, and continue to make the attempt to learn more.

That's one of the failings of being an amp designer. You REALLY need to dumb down the function, operation and intuition needed to operate the amp. We have posters here that have built a few amps already, have a basic knowledge of electronics, and still don't understand why their BF clone farts out with the bass above 2 when they overdrive the amp?!? BECAUSE THERE'S TOO MUCH BASS. If you turn the bass down you can still get the same bottom end in the final EQ because too much bass just clips off and sounds flabby. Because the amps I build are basically vintage style "hot rods" all souped up to get high gain when needed I have, on more than one occasion, had to explain their operation to people that are use to channel switcher types. For example, with a vintage style amp that is clipping hard the EQ controls cease to be EQ controls. They begin to act more like distortion character controls. This is because any adjustment they make to the wave form is lost because these controls are ahead of some clipping stages. Any final EQ balance in a vintage style amp is a matter of the cabinet, the speaker, the OT, what type of power tubes are used and their operating conditions, etc. The "tone controls" do almost nothing to the amps final frequency balance once the amp is clipping hard. But, believe it or not, A LOT of otherwise knowledgeable people don't get this concept. Non tech players that never used vintage amps are utterly confused by it.

This has been the lynch pin in marketing my designs. What use to be common knowledge, understood or not, for amp operation is now specialized knowledge that modern players don't want to bother with. It's much easier to buy a digital sampling amp that will give you 90% of the tone, more versitility, easier operation and one third the cost!!! Hell, I practically talked myself into one just now! But I gotta have that last 10%. When people who've bought my amps first heard them they felt the same way. I just hope the crazy cranks in the world, like you, me and the other posters here, can keep enough of a niche going that the ideals don't fade away. I do see positive things in the market. Kids and noobs line up to buy cheap Chinese made tube amps (that actually sound really good most of the time). Sad to see the industry leave our shores. But that's our own fault, and another story. But it does speak about the sensibilities of the new players. That they would still often choose tube amps.

No, I'm not a designer outside of those designs I make for myself and the odd custom order. When I say odd I mean it. I don't build professionally and have sold less than a dozen amps that cost more than average and I never made a dime. I did do a little design work with one big cootie in the industry and even presented one year at NAMM. Those doors are still open but I'm not involved in current projects. So I'm just a guy that likes the way amps sound and is always trying to learn why they sound like they do and how to make them sound the way I want them too.

[Steve Conner]

Chuck, that is absolutely true , I think the way to design a vintage amp is to choose the speaker, cabinet, tubes, OT and so on for the tone you want, and then just have a volume control and nothing else, like the Brian May AC30.

I appreciate you taking the time to help tonequester out, however given the budget constraints, I'd have to question the need for an expensive panel meter in the attenuator? The output is going straight to a solid-state power amp with no gain control, so the attenuator's output control is effectively the master volume, and you can set it by ear.

If I was looking for some kind of metering, it would be a clip indicator for the SS power amp, but I'd probably end up ignoring it too. I found that I could clip the SS power amp quite a bit in a setup like this with no major bad effect on the tone.

[J M Fahey]

Hi tonequester.
Just checked your Velleman kit.
EXCELLENT choice.
Why do I say so with capital letters? ...
Because I know it very well, it's basically the same as my own 100W power amp, which I have been using successfully for over 40 years now (first with 2N3055 outputs, then switched to TIPs) and know very well what it can and cannot do.
1) it's really 100W/4 ohms or 70/8 as they say.
2) use a transformer of *maximum* 30+30VAC .
If you go a little lower, so much the better. (say 28+28 or 27+27)
You still have more power than you need anyway, and it's safer.
"Old time" transistors were always built over spec, competition was based on quality.
Today competition is cut throat based on price, amd even the "good" brands (ON, ST, Fairchild) which I use now meet the specs and just that.
Up to 10 years ago I run these transistors with beefy +/- 45V rails with no problems at all and they were 90W into 8 ... then had to lower to +/-42 ... +/-40 ... now I'm running about +/-38 or 39 .
Anyway, you will have the power of a moden Bandit, a Marshall/Laney/Crate "80W" SS amp, you can play anywhere along any drummer, which is the real yardstick to mneasure performance.
Now you ust need to sell that speaker to a Rhodes fan, buy a new car and with the spare money buy a new peaker

[Chuck H]

+1 on nixing the panel meter. The one I used on my last project (that used one) was a real cheapy ($22). But it was set up to detect wattage, not voltage. A meter for that would be MUCH more expensive OR another small amp would need to be designed just to run the meter. Either way it's overkill for this project. The only reeason I thought it would be a good idea is that it would instantly identify the useful level whether using a 1W amp or a 50W amp. 'cause there's A LOT of variable there. But I like the new idea better anyway. and it uses a simple LED. The "protection circuit" will keep any user from putting 20VAC into an amp input and I expect the resulting sound should be indication enough without blowing anything up. That, and the LED lighting up.

[tonequester]

tonequester here.

G'day Chuck ! I guess that were both a little odd-ball. However, given that we are so about THIS subject, I believe that a little thought outside the box is appropriate.
My experience with the musicians I've know over the years is that they are much more in the know concerning their musicianship, than with their own equipment. Presently, I'm lucky enough to know a few that readily admit this. I'm not nearly as knowlegeable as I would like to be, and admit that. However, I do my best to learn about even their equipment. I've known those that didn't care to know anything about their amp besides how much power it had(no concept even of RMS or "music power"), and where the volume control was. They were also usually not too concerned whether they were in tune or not. I fully understand your 10%. It's the same thing that I have always sought. I have been lucky enough to here my share of vintage amps, when they weren't even called vintage. I've also heard the Line 6's of the world, which claim to have captured the 10%, but don't deliver(to these ears). This project has come a long way since the first post. I've got 20+ pages printed off, and another 6 hand-written. I believe I will continue to do this until the amp is built. The title : The Evolution of a
Novel Approach to Electric Guitar Amplification. I feel that everybody who has contributed with their replies has done me a great service, which I can only hope to re-pay. Whether it's music, or electronic's, often the "odd-ball" has been the one who has made the difference between success and failure. I'm on the same page as you are, even if I'm not yet up to your level of expertise. you have made that possible with your ability to explain that which is not easy to explain, nor always easy to understand. You and several others on the forum are odd only in
their passion for music/electronic's. It's not everybody's "cup of tea". I drink it by the gallons ! I believe that you do as well ! I am sure glad that you are here where you belong, for the wanna be's like me to benefit. Have a great day Chuck. tonequester.

[tonequester]

tonequester here.


Greetings Steve. thanks for the reply to the post. Also, it's good of you to be mindful of my budget constraints. At times, I get so into a project that I forget them.
I hadn't gotten around to seeking a panel meter, so have no idea about their cost. Chuck H is in agreement with you and I see no problem with some type of indicator light/L.E.D..
I must also admit that in principle, i am in agreement with your thoughts about just how an amp should be designed. I've shunned the normal passive tone controls on guitar and amps alike almost from the start. Perhaps an odd reason for this is that I just don't like subtracting from the signal in that manner. it's just one of those gut things, I guess. I was willing to try something different, that "sounded" like it might ADD something to the end sound(Q-filter). After doing a little study on your opinion of that particular "circuit', I now realize that it's just
the same old tweeking by subtraction. One less switch, one less knob to fool with while you try to play. The idea of designing for tone instead of altering what you have created, whatever you have created seems pretty sensible to me. One thing that I will admit to being fond of with regards to adjustment on the fly, is the change, mid-solo, of pick-ups for tonal effect.
I've always admired Leslie West for doing this fairly often, and I try to emulate him in this regard, typically the shift from bridge to neck. Best wishes to you and your projects. Thanks for your continued interest and replies. tonequester.

[tonequester]

tonequester here.


Greetings JM. I'm happy to know that your opinion of the kit is a good one, and based on personal experience, as well as your over-all knowlege of the subject.
I am printing off your reply as well to add to my documentation of the evolving project. Your perception about being able to "hang' with a drummer is indisputable, and nothing quite ruins a
song like a domineering drummer, whatever the root cause. It's a relief to know that I won't have to worry about being underpowered, even in the future. I'm e-mailing "Rhoads" about the
"vintage" speaker and if I can get enough to buy the heat-sink for the power amp I'll be happy. The new car can wait. after-all, I have an amp to build. remembering the old Camel commercials, to paraphrase......I'd walk a Hell of a lot farther than a mile for my tone. Great hearing from you on this. Best wishes" Argentina Way". tonequester.

[tonequester]

tonequester here.


Chuck, as for me... I am always sure to turn volume completely down, before plugging in. I even check the polarity of unfamiliar outlets. I don't even fire that HT-1R up without checking it all out. My first amp, the Princeton, did not have a stand-by switch, and I quickly learned to hate that" pop"when turning on with the volkume up. I do like the protection circuit idea, and I am one to pay attention to L.E.D.'s being lit or not. It seems that all opinions are that the direction of the evolution of the project is proceeding well.
I have to give credit here to loudthud, for his nixing of my last choice of kit, and his subsequent choice of the Velleman kit. he pointed to a lack of "robustness' in my last choice, and felt that this Velleman would be very reliabile. It's hard to fail when one has as much help as I've had on this forum. thanks to all ! tonequester.

[tonequester]

tonequester here.



Greetings JM. I have a few questions/thoughts concerning the K8060 kit/amp if you should get the time. With your personal eus and experience with this type of amp
I feel you would give me the best info coincerning said amp. I've been studying the data sheets that I've downloaded for all semi-conductors used. I must admit that I have Zero experience with the Darlington "pair". So I'm trying to get up to speed on it's basic functions, advantages , and disadvantages(if any). I had to look up the definition of epitaxial just to get started.
I ran across a review of the kit, it's assembly, and it's performance entitled : A very good home-made velleman K8060 discrete power amplifier(2 X 100 W rms) and a stereo set-up. This
article @www.spannare.se/k8060.html. Over-all I think it was a very positive review. I know that it is not the exact same application as what iIintend for my amp, but bear with me and my lack of knowlege. He(author) recommends the mnodification of using 4700uf filkter capacitors, instead of the stock 3300uf caps. Did you do this on your build ? He also claims that a 10 k
log pot is better than the 47 k log pot shown in the manual. What is your opinion of this. There is also mention made that a separate RCA switch is necessary for many signal sources.
Would this apply to my situation, inputting low power tube amp,via "attenuator adaptor" to the box. This perhaps would be best addressed with the output connection design of the
"attenuator". I'm basically getting together a list of "accessory parts" for the kit, and wish to be able to start "shopping around" for them. His main concern with the build itself, seemed to be the care that must be taken and the time involved installing the heat-sink.