[TV MAN]

Hey all! With winter rapidly approaching I'm getting set up to finish a few projects and start a few. While waiting on parts for the Emerson TV, I finished a Zenith radio and ended up with a bare spot on the bench. Then I saw it - my chi-fi amp kit. Yes, I have several different ones for different goals, but this one I bought mainly for the chassis and parts. It was cheap and gave me a lot of the parts I wanted to do something of my own creation. To buy the individual parts and have a chassis punched, etc etc would cost a lot more and this gives me a ready made chassis, power supply and all the little gizmos that add up quickly.

To begin with, the kit was an eBay find for about $150 +-. Just a simple single ended kit with a couple 6BQ5 (china versions) finals and double triode driver. Simple power trans with bridge. I havent been really happy with the past kit I built - it lacks something but not sure just what, so this one is getting scrapped and I'm building my own design. Will it work? Shoot, I don't know - if not, I'll yank the parts and try again with a different design, or trial and error until I get something decent. It's just a basic PP amp circuit and my goal is a 15  watt monoblock. I want to keep it simple. Probably the most complicated thing will be an adjustable bias supply so I can set it for the right current if I want to try some different bulbs. Honestly, there aren't many more parts if I'd do a cathode bias, but it's a little harder to adjust.

This is actually on my bucket list. To build my own design. This is JUST an experiment. I have several output trannys to try, and may even dabble with some sweep tubes, but for now, I axed the china tubes in favor of some 6V6s and a 6U8 or 6GH8. (I've seen quite a few 6GH8s be noisy), but seen 6U8s in organs and other musical instruments. Speaking of organs (organ donors?? ), I have a tranny from a Hammond organ I'm going to try (6V6), a couple cheap eBay finds and something from Musical Power Supplys I have coming. The latter are ultra linear and will probably be my final choice, but again, this is an experiment. Sure, there are numerous threads in DIY, Carma, and so on about this, but this is my compilation. I really couldn't find a diagram I really liked (I'm more traditional), so I drew something up using ideas from several diagrams.

Alright, so here's what I did and where I am. I'm using the power trans/supply from the kit. The trans "says" .2a on a 230v B+ with a bridge, 3A on the filament, couple 330 caps and 100 ohm resistor. Should be in the 300v B+ range to work with that. I'll send that to the output trans, come off that with a 5h choke and 47mf cap to supply the G2 and driver. If I use the ultra linear, then it'll only supply the driver. I had to enlarge 2 of the tube holes to accept the octal sockets. Forget a cheap big box store step bit, this baby is stainless, so that was a FAIL, ended up using a burr and die grinder. Got that done. Sure, I could have used the 6BQ5s, but this gives me more options to swap tubes around with anything from a 6F6 to a KT90 (well, maybe not that big, but more options anyway). 9 pins really limit. Need to get a good step bit for the future. The biggest problem was the vent holes around the tubes, but I found the sockets I used fit the holes already there perfectly, and gives me a lot of available positions for the sockets. I used the top mount sockets to cover my redneck engineering.

My goal with this? Well, I'm not really an audiophool, but I want something that sounds really good. I'm sick of those cheap bluetooth speakers, squeaky phones, and crappy radios you get nowdays. I want to try my own design, use new production, readily available, economical parts (unless something special is needed), and build up to something better. Oh, this isn't my 1st crack at this. I built an amp back when I was in junior high, using a schematic found in an old radio book and parts I had around. Once I got the bugs worked out, it really sounded pretty good, but it was just built on a flat piece of metal robbed from some old cable TV strip amps. Done a few kits, and sure, could get my Dynas out, but ... So now, I try again. At least this will be good for some entertainment. If it smokes, it smokes, if it blows something, it blows it, if it works, it works. If it fails, it fails. Stay tuned for the fireworks!

   
   

[morzh]

Tim

From what I heard about the Chi-Fi small amp kits, they do work, and they work well enough.
A son of an old late friend from Russia picked some up, built them and was fairly pleased with the results.
This said, something in us, old-timers, has that idiosyncrasy towards all things Chinese, plus I do allow for the quality of the components, both tubes and the transformers, to be no necessarily at the very top.
Used with good sensitive speakers, I am sure most of us would not be able to tell the difference between these and any hi-end at the small power output. And even with those of us who used to have very good hearing (me, I was diagnosed with the "golden ear" (absolute hearing) when I was 8), the age does not improve upon it.
So most of it will be in our head and soul, both the decent enough sound quality and the satisfaction from "look what I've built!".

I own a McIntosh 375 and EICO HF22 as the output amps, and two McIntosh C22, one original and one today's build as the pre-amps.
Together with 2 pairs of Klipsch Cornwalls.
I have to say, I enjoy listening to them.
But if you ask my honest answer to whether or not I will be able top tell it from my old Kenwood run-of-the-mill solid state 1992 rack system, I won't lie to you - I dunno. I thought I heard the difference when I used Klipsches instead of the Kenwood towers, but that was 8 years ago. And even then I did not hear the difference between the amp, when hooked to the Klipsches.

So. Enjoy the process. This is what I enjoy most. The process. Of design, building, restoration, and hearing the result.
To me, this is the goal.
And, if you study your literature on the tube amps well, and spend the necessari minimum on good transformer and the tubes, it might actually be competitive.

Mike

[TV MAN]

I've built several china HiFi kits and the single ended one (have a thread on it) worked and sounded pretty good. I built another using PP pentodes (have a thread on that one too) and it works ok, but just seems to lack something. I really cant lay my finger on what it is. I have pretty good hearing but I'm not so super picky that I look to hear certain sounds from a scratchy record. I can hear the horizontal running in a TV and many can't. I do like clean, hum/distortion, hiss free sound and I just never was satisfied with the run of the mill solid state stuff. I really learned that when I picked up a pair of Dynas from a stereo store years ago. It sounded so different, so much cleaner. I use a Pat 4 (Dynaco) with my single ended amp and bose speakers, and I do attest that it sounded really good. Much better than I expected. It quit tho and I haven't gotten into it yet to see why. I use the same Dyna Pat 4 with this PP amp, but it might need some new caps and driver transistors. Had to replace those on my 1st one. Sure, I can revamp my Mk 3 or st70 amps and crank on and may in the future, but I am going to experiment some with a pair of my own and see what happens. Not cheap but not big bucks either. I actually think I might do a different design on each one and see which one I like better. I really need to revamp my Pas 2 because I know it is a super good sounding preamp. I also have a nice "Sound Valves" preamp. So, the experiment is on! Let's see some smoke, sparks and have some fun!

[morzh]

I also heard that small 3-4W Class A (SE) amps sound pretty good.
And, paired with a sensitive speaker (well, Klipsch again, 102dB - 105dB) that could be clean and loud.

[Arran]

I wonder if a Greenlee chassis/knockout punch would work on Chicom grade stainless steel? I have some step drills somewhere but never figured that they would work on anything harder then mild steel. One thing that you could try, if you need more B+ for the power outputs from the supply with the kit is a full wave voltage doubler, A friend of mine has a 1960s era guitar amp where they did that.
Regards
Arran

[radiorich]

hello Tim,
Yes, I also want to build one too and I have those Greenlee punches .
I want to build an amp from scratch .
Sincerely Richard

[RodB]

Stainless is very soft and delicate. I think your Greenlee punch would work fine as long as the gauge is reasonable. Those punches are hardened steel. Let us know how it goes.

[morzh]

They were selling a single Klipsch "Heresy" during the auction in my town tonight.
No one bought it.
Had it been 2 of them, I might be tempted. The price was good.

But for one amp....


BTW they were selling two 50W1 McIntoshes today. I ma not sure why I did not bid. I always wanted them, and the price was right.

[TV MAN]

Actually, that stainless is some pretty hard stuff. It does scratch easy, but to drill, it's pretty tough.Kinda like a sink... I'd thought about a chassis punch but with the vent holes, figured I'd bend it. When I get the OP trannys in I'll drill holes to mount. I'd thought of trying it as it is with the single pentodes, but really bought them to do a hybrid using the power supply & chassis with my own amp design. I almost gave up when I measured the socket holes. Thought I could put a wafer socket under to use a pair of octals, but felt that put the chassis too close to the tube pins and might carbon track or arc. So I hogged things out. I have a pair of Warfedale 70 speakers I've been using (from Ron).

I noted with the PP amp kit I built that it really likes to clip on the heavier bass, and it seems the highs are a little dry. Could be in my preamp, (I know I need to recap and replace a couple driver trans) or I could just be punching it too hard. Anyway, even with the mods I'm doing with the kit, the 6V6 tubes would work as the kit intended if I desire to go that way. I'm doing one at a time to fiddle with things and tweak stuff until I either get it sounding like the way I want or see smoke . The 6V6's heaters only pull .45a, while the pentodes with the kit draw almost double. Plenty of P trans filament power, but figure less pull from the tubes would free up a little more B+ current.

Arran, I'd considered a doubler, but with things as they are, that should put my plate supply right at 300-310v, which according to the tube manual is where they like to run. I'm sure a few more volts wouldn't upset them too much.

[TV MAN]

Mike, if this experiment is a fail, I'll use the other amp kit as designed and hook up a pair of bookshelf speakers to use in my office. I do have another amp build experiment or two in the wings to build regardless if this is a success or failure. Either way, I think this will be a fun little build.

[morzh]

My very first tube build (I was...17?) using PCBs and EL84 ended up with me recieving a shock from B+.
Almost immediately I decided to switch to transistors.
And up 'till 12 or so years ago I did not touch tubes much.

[TV MAN]

Mike, that is so funny! I was the exact opposite! I experimented with a Radio shack transistor course, and decided tubes were the way to go after I smoked a couple transistors
I used what I could find sitting out in the trash when I was younger. Back then, it wasn't uncommon to see an old record player, radio or TV sitting out on trash day. I had a wire basket on the handlebars of my bike (caught flack over it too) and brought home some really cool stuff! Really tho, what sold me on the tube stuff was that after getting a really nice transistor rack system (separates) and not liking all the computer hiss, noises and all that stuff, found an old Dynakit 70 and Pas3 in a stereo store for a couple hundred (yeah, I just dated it), took it home and hooked things up and was totally wowed! Noooooo comparison! Bought another 70 later same place for just a shade over 100 and set them up as monoblocks. Loved it! So, yeah, those tube electrons flow through my veins, and yeah, I've been zapped a few times. Try tapping the shunt regulator on a Zenith TV with a lead pencil

[MrFixr55]

@TV Man, try tapping the plate cap of any shunt reg with a lead pencil. Or are the zeniths uninsulated? It's been too long. the fact that I made it to adulthood alive and with all of my limbs, eyesight and some of my grey matter is proof of the existence of a benevolent, loving God!

Yeah, I used to scrounge. Still do. Until the flat panel TVs came out, I had purchased only one new TV in my life, an RCA Dimensia. Still have it. The others were all street finds. People made fun of us "recyclers" back in the day. Today, it is not uncommon to see a Beemer or Benz stop, and someone pick up a nice street find.

As far as tubes vs xistors, try to find a serious rock guitarist with a solid state amp.

[morzh]

I absolutely attribute my reaching 63 to God's benevolence, but this apart, it has never occurred to me to tap anything electrical with a led pencil.
Of course it did occur to me to stick my head into a machining center that was 1/2 second from decapitating me, but...have I already mention God's love and benevolence?

[462ron]

LOL@ MrFixr. I remember an encounter with my first tube radio.. I think I have posted this before. Back when I knew just enough to be dangerous some 55+ years ago as a young teenager, I found an old floor model radio at the curb. My friend and I dragged it to his house down in the cellar. We put the chassis and speaker on the table. My friend had his arm lying across the back of the speaker while at the same time reached for the bare metal volume control.it picked him up and threw him against the wall. I know now that he was in contact with either a wire on the output transformer or field coil. He was hit with a healthy 300V B+. Luckily he wasn’t hurt or worse. His mom heard the commotion and when she heard what happened we were barred from the basement and told to get rid of the radio. I continued on to this day with my interest in radio, my friend was cured and never bothered since. Good times!

Ron