"Also...Has anyone actually tried 6GY5 in the circuit yet? "
These are all equivalent tubes spec wise to the 6GY5, maybe someone has tried one of these.
6KE6 21KA6 21JV6 21HB5 21JZ6 (and other filament V's)
These are all equivalent tubes spec wise to the 6GY5, maybe someone has tried one of these.
6KE6 21KA6 21JV6 21HB5 21JZ6 (and other filament V's)
I bought a box full of them but haven't tried them yet. Search the thread for 16GY5 since they are on the dollar menu at ESRC and at least one builder was going to try them. Quite a while back though.
I see no reason why they wouldn't work since every sweep tube that I have tried has worked in this board and I have tried a bunch. Getting 25 WPC from a 4.4 K OPT should be easy with any of them, you will just need to avoid turning it up all the way since I think 50 WPC or more is possible. Do your transformers have a 4 ohm tap? If so put your 8 ohm speakers on the 4 ohm tap to get an 8.8 K OPT. Try it both ways and see which sounds the best for you.
Yep, thing is I'm stuck with my Snell Aiii monsters and they are 4 ohms. I keep trying to get something else in there to displace them but I keep coming back to them. They are a really, really decent speaker when fed the right stuff. I just finished modifying my Magnavox 9303 today (beefed up PS, separate G2 power, better coupling caps...) and hooked it back up to them. Better than pre-mod but still definitely short of what the Snells are capable of. My friend's Pilot SA-260 was noticeably better with them and I have a feeling that there is still further to go beyond that. I'm more convinced now that whatever else is going on I will realize a benefit from having more power going to these 86-87db sensitivity speakers.
I have some Stancor iron sitting in a non-working Knight integrated EL34 PP amp. When that amp worked it didn't impress me. I could yank that iron and go to work on a 5-20 sort of thing but I have a feeling I'm better off fixing it (if I can) and flipping it so I can get some big iron of my choice.
Frankly I want to build this amp. I'm thinking I can just do it now with the iron I have and get some bigger stuff when I've got the means to. I know I'm going to have a very difficult time in keeping myself from turning it up despite my undersized OPTs. Is there a chance that they'll be fine at 50W? If (when) they aren't, are we talking simply degraded sonics or melting/smoking/destruction?
Oh yea, was just asking about 6GY5 because as I read through the thread it sounded like a few folks had marked it as a potentially being a bit more interesting than some others. Cliffhangers for geeks...
I have some Stancor iron sitting in a non-working Knight integrated EL34 PP amp. When that amp worked it didn't impress me. I could yank that iron and go to work on a 5-20 sort of thing but I have a feeling I'm better off fixing it (if I can) and flipping it so I can get some big iron of my choice.
Frankly I want to build this amp. I'm thinking I can just do it now with the iron I have and get some bigger stuff when I've got the means to. I know I'm going to have a very difficult time in keeping myself from turning it up despite my undersized OPTs. Is there a chance that they'll be fine at 50W? If (when) they aren't, are we talking simply degraded sonics or melting/smoking/destruction?
Oh yea, was just asking about 6GY5 because as I read through the thread it sounded like a few folks had marked it as a potentially being a bit more interesting than some others. Cliffhangers for geeks...
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Zap!
So I went to power up my DCPP. ZAP! Something arc'd to the aluminum plate on the top. My best guess is the Q2 for the ripple filter arc'd since only a mica separates it from the plate. The Fuji mosfet I used does not have an insulated package. I shut off the amp immediately and now I'm afraid to turn it back on.
Anyone have a suggestion why this would happen? The humidity in the room is quite high. Is my Q2 dead? Solar flares? Magic amp gnomes? Unfortunate spider making a home in the chassis?
So I went to power up my DCPP. ZAP! Something arc'd to the aluminum plate on the top. My best guess is the Q2 for the ripple filter arc'd since only a mica separates it from the plate. The Fuji mosfet I used does not have an insulated package. I shut off the amp immediately and now I'm afraid to turn it back on.
Anyone have a suggestion why this would happen? The humidity in the room is quite high. Is my Q2 dead? Solar flares? Magic amp gnomes? Unfortunate spider making a home in the chassis?
If you heard a snap, there should be evidence of the cause somewhere. If it were my amp I would dissasemble it and look it over carefully for evidence. Even if it still works, it's likely to do it again sooner or later.
The mica insulator is a possibility. If it broke down there should be a black mark on the aluminum. Other possibilities are blown resistors, capacitors and the mosfet itself. If it made a noise there has to be evidence of the zap somewhere. When one of my amps blows up, it's usually obvious. There is a black stain on the board where a part used to be.
I have no knowledge of your specific OPT's but if they weigh 4.6 pounds they should do more than 25 watts without smoke. The OPT's that are currently in my 125 WPC amp only weigh about 5 pounds each. I bought a lot of them about 10 years ago, and I am not afraid to blow them up. So far I have fried only one. That was in a guitar amp running at full crank when the speaker got disconnected. Yep, fire and smoke occured and a tube socket, a 6L6, and a few resistors got fried too.
In a more normal situation distortion will become obvious long before amp damage should occur. Any OPT does not have a fixed power rating. They ALL will pass far more power at 1KHz than they will at say 20 Hz. My 5 pounders were rated at "80 watts" for guitar amp use from 80 Hz to 4 KHz. I have seen them distort at 25 watts and 30 Hz when fed by EL84's in a Simple P-P amp, and I have seen them pass 50 watts cleanly at 30 Hz when fed by 6HJ5's in the red board. I have seen these same transformers crank out over 200 watts at 1 KHz when fed by 6LW6's on 750 volts!
The OPT will distort first on the low bass frequencies because the core becomes saturated. An OPT converts electrical energy to magnetic energy and then back to electrical energy. At some point the iron core can not accept any more magnetic energy and saturation occurs. Any more input does not result in more output. Attempt at applying more input causes the current through the output tubes to go up rapidly. Repeated attempts at this can cause output tube meltdown followed by other blown parts, possibly including the OPT. However the amp will sound terrible at this point, and most normal people will turn it down. Guitar players are not considered normal audiophiles.
Saturation is HIGHLY frequency dependent. As I indicated above an OPT may be happy at 200 watts on 1KHz, but may saturate at 30 watts or so at 30 Hz. So if you are going to rattle the walls with rap noise, don't build this, get a solid state thumper and use the tube amp for the mids and highs. If you play music that is not overly bass heavy at reasonable power levels, try it.
The saturation limit is also dependent on the impedance characteristics of your speakers. I can't hit saturation on my Yamaha speakers before I set them on fire because their impedance is something like 20 ohms below 50 Hz. I can hear saturation on my Silver Iris but it is rock concert loud before it happens. They are 96db efficient 15 inch coaxials.
Yes there was a black mark on the aluminum, but no indication where it came from. I seem to have made a stupid mistake too. I powered up the amp without having one of the channels connected to speakers. Not good.
So I wired up the speakers and after a visual inspection I fired it up again. It played for about a minute and then sparks and smoke. Sound was gone, and I hit the power switch quickly. At least I know the transformers are OK. I'm guessing Q2 gave up the ghost.
I suppose a lazy fix would be to slap on a spare 6H choke and bypass the gyrator altogether. Mosfets don't like me.
So I wired up the speakers and after a visual inspection I fired it up again. It played for about a minute and then sparks and smoke. Sound was gone, and I hit the power switch quickly. At least I know the transformers are OK. I'm guessing Q2 gave up the ghost.
I suppose a lazy fix would be to slap on a spare 6H choke and bypass the gyrator altogether. Mosfets don't like me.
I completed the 6HJ5/6GU5 version with two Antek AS-2T230s; one for board power, one for OPT plate connection. Antek AN-0240 for the bias.
It works fine except now I have about 750mV 120Hz hum on the speaker connections. I jumper clipped the whole circuit together just sitting on the workbench to test before mounting everything in a chassis. There was a barely audible hum. I did not measure the level because I thought it was due to the birdnest wiring and would go away when installed in the chassis.
I used the power supply configuration shown in post #637. I attached it here for reference. I am using 500uF caps instead of 600uF. I jumpered in a 100uF cap but it made no difference. The lower FWB shown in the drawing is the 2 redboard diodes with 2 additional diodes to form the bridge. The bias transformer I am using has a CT so no additional diodes needed for the bias supply.
Any ideas where I might be getting the high level 120Hz hum?
Edit: The board voltage measures 315V, plate voltage 630V.
It works fine except now I have about 750mV 120Hz hum on the speaker connections. I jumper clipped the whole circuit together just sitting on the workbench to test before mounting everything in a chassis. There was a barely audible hum. I did not measure the level because I thought it was due to the birdnest wiring and would go away when installed in the chassis.
I used the power supply configuration shown in post #637. I attached it here for reference. I am using 500uF caps instead of 600uF. I jumpered in a 100uF cap but it made no difference. The lower FWB shown in the drawing is the 2 redboard diodes with 2 additional diodes to form the bridge. The bias transformer I am using has a CT so no additional diodes needed for the bias supply.
Any ideas where I might be getting the high level 120Hz hum?
Edit: The board voltage measures 315V, plate voltage 630V.
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I was going to mention this when you posted pics of your chassis, but I didn't want to discourage you. The buzz is likely being picked up off of your steel chassis. Try shorting the inputs at the PCB and at your RCA jacks. Any difference?
I have an old project I am trying to finish and get off of my bench. It's an old amp that my dad built in the 60s, which uses a large steel chassis. It lacked a power transformer, but the recent "discovery" of these Anteks gave me the chance to get it working again much more cheaply than I expected. I found out the hard way that stuffing one of these Anteks under a chassis creates a serious hum problem that has been quite challenging to overcome. The chassis is spewing all kind of noise picked up from the toroid. Pulling the transformer away reduces it significantly. Just moving the shielded input cables around shows how big the field around the transformer is. I got mine before the AS models came out, so my chassis is energized with HF junk off the power lines too.
Besides the usual tricks, I've also:
- Constructed a shield around the toroid.
- Put suppressor caps on the rectifiers, even though they are UF diodes.
- Changed my star grounding scheme to a bizarre setup that was found experimentally (I believe I am shorting out some of the chassis currents).
- Move the RCA jacks from the back of the chassis to the top, very close to the input tube.
Each one took a good chunk out. The suppressors in particular turned the 120Hz buzz into normal 60Hz hum. I could see the spikes on the scope with the probe held in free air near the transformer. I don't know if you will have to go through these lengths, as my amp currently has a lot more gain than it needs.
I have an old project I am trying to finish and get off of my bench. It's an old amp that my dad built in the 60s, which uses a large steel chassis. It lacked a power transformer, but the recent "discovery" of these Anteks gave me the chance to get it working again much more cheaply than I expected. I found out the hard way that stuffing one of these Anteks under a chassis creates a serious hum problem that has been quite challenging to overcome. The chassis is spewing all kind of noise picked up from the toroid. Pulling the transformer away reduces it significantly. Just moving the shielded input cables around shows how big the field around the transformer is. I got mine before the AS models came out, so my chassis is energized with HF junk off the power lines too.
Besides the usual tricks, I've also:
- Constructed a shield around the toroid.
- Put suppressor caps on the rectifiers, even though they are UF diodes.
- Changed my star grounding scheme to a bizarre setup that was found experimentally (I believe I am shorting out some of the chassis currents).
- Move the RCA jacks from the back of the chassis to the top, very close to the input tube.
Each one took a good chunk out. The suppressors in particular turned the 120Hz buzz into normal 60Hz hum. I could see the spikes on the scope with the probe held in free air near the transformer. I don't know if you will have to go through these lengths, as my amp currently has a lot more gain than it needs.
Thanks for the reply. Yeah, I was kind of thinking that might have something to do with it. Another strike against a steel chassis, although it was free. I did try shorting the inputs at the board with no change. I'll do some troubleshooting when I'm at the shop tomorrow.
Any insights into your bizarre experimental grounding scheme?
So, what is the highest power level up to with this amp now. I haven't been online for a while so I lost track of it. What is the tube used with that power output too?
Nick
Nick
6HJ5/6GU5 with more then 600v b+ and 3.3k primaries nets 135watts for anything but a sign wave.
Make sure that you have at least 20 volts across the regulator fet. If it is in drop out you will have hum.
The 125 to 135 WPC level is a stable build that a few people have duplicated. As stated 6HJ5's or 6HD5's and 600+ volts on their plates with a 3.3K ohm OPT is the recipe for that. Cranking it to full tilt with music for indefinite time periods causes no problems for the amp, but your ears, neighbors and speakers are all going to be upset. Running the amp at 125 watts into a dummy load with a sine wave tone is not an issue as long as the test time is kept to a minute or so. Extended test time will cause a pale red glow in the output tubes. Any 25 watt or larger sweep tube should be OK at this power level.
I decided to explore the upper limits of the power spectrum using an external bench power supply that goes to 650 volts at 1.7 amps and some 35 watt sweep tubes. I used 35LR6's because I have a bunch of them and I got them cheap. The amp makes 250 WPC in this configuration with the power supply maxed and a 2500 ohm load. I cranked some music through it for a couple days and tested it with sine waves. It is about the same as the 125 WPC version. 5 minutes of sine wave testing provokes a pale glow, music does not.
In a moment of temporary insanity I wired both channels in parallel through a common OPT set for 1250 ohms. The combination made 504 watts at 5% distortion, and 525 watts at clipping. At this level the power supply was making this deadly sounding buzz and the bench lights would dim as I cranked it up. I decided that I had pushed the limits enough since my OPT's are rated for 400 watts and they are irreplaceable on my budget. So unless someone out there is a bit crazier than me, the limit stands at 525 watts from one red board! All of my exploits are scattered throughout the thread.
I do have some 40 watt tubes, and some 50 watt 4D32's but I need a bigger power supply. Then I need a bigger wall outlet to plug it into........
how about this for a traffo? 3 1/2 inch stack of 2 inch center leg core. rated at about 750VA...
An externally hosted image should be here but it was not working when we last tested it.
I have a 600 volt to 120 volt industrial control transformer rated at 1KVA. It puts out about 575 volts when hooked up backwards. It makes over 700 volts of B+ into a bridge rectifier and cap input filter. There are at least 3 of the 400VA Anteks around here somewhere I could wire together.
The most expensive tubes that I have bought in years were the 4D32's that you pointed out. I try to stay under $10 and tend toward $1 tubes. I collected over 100 $1 sweep tubes at the Dayton hamfest this year, and got 45 35LR6's for $3 each last year. The 4D32's were $25 each. I could wire 8 of the 35LR6's together for the same money and have over 300 watts of dissipation capability. Someday I would like to find the time to actually build some of this stuff.
I have 3 red boards. One is the original that is used for the experiments that got us here. The second is a completely working 125 WPC amp that gets used often. It is still mounted on a piece of plywood in the living room. Sherri will be coming home soon, so I guess I need to make a chassis for it. The third will be used to make another unique amp. I haven't fully decided on what yet.
hey Geroge, that's my signature that you reacted to......😀 will change it shortly......😀
i have a quad of QE08-200 tubes rated 100watt plate diss, the innards shows 3 cathodes, grids and screens wired in parallel covered by a single set of plates...since i have more of the 4D32's they are my choice tubes right now.....
i am building 2 sets of OPT's based on BudP's suggestions....
the 22k grid leak resistor guidelines indicate that mosfet followers are the way to go......
i have a quad of QE08-200 tubes rated 100watt plate diss, the innards shows 3 cathodes, grids and screens wired in parallel covered by a single set of plates...since i have more of the 4D32's they are my choice tubes right now.....
i am building 2 sets of OPT's based on BudP's suggestions....
the 22k grid leak resistor guidelines indicate that mosfet followers are the way to go......
Yeah, I know, but I couldn't resist..........
Beware, the light you see could be the warm glow of a thoriated filament, or the cold headlight of an oncomming train!
Yeah, I figured that out. I did however test each tube in a SE amp with 100K grid resistors. No issues were seen but I didn't push the tubes hard. Two were bad, one glowed bright purple, one had completely gone to air. Seller replaced both.
Never heard of that one.
I have several used 833A's. I abused one in SE several years back extracting about 200 watts from it. I don't see myself building anything with them, so they will probably wind up on Ebay.
I resolved the hum issue. It was the shielded input wires after all in proximity to the toroids. I re-routed them and now I'm down to 4mV hum on the speaker terminals. Not too bad.
One problem. I was checking and verifiying voltages, probe slipped, Q2 & D9 blown up. Oh well could be worse.
i knew you'd say that......😀
i guess i will have to set up a test jig to find out condition of my tubes then....but visually they seem okay.....i had this experience with 6C33 tubes wherein the filaments tested open the first time, i had to use sandpaper to clean up the pins and then they worked....
that was my reaction too the first time those were offered to me...but a look here convinced me to take them in......http://frank.pocnet.net/sheets/084/4/4D32.pdf
they are offered at about $150 each in the net....i got it for just under $30.....
Both of my defective tubes did NOT pass the visual test. One had no getter spot at all. The other had a faint white spot where a getter should be. I emailed the seller about this and he said that he would replace the tubes if they were indeed defective. I decided to wire them into an SSE board and crank them up. All the tubes with shiney silver spots work just fine. I came to the conclusion that these tubes don't like SE class A operation, but I didn't try too hard.
I posted my experiments in a thread in the Tubelab forum. A ham radio operator replied that problems with air leaks in late production Ratheon 4D32's are well documented in Collins radio forums. Plugging a gassy 4D32 into a vintage Collins transmitter causes some expensive fried parts. In my case it just looked cool and made rude frying sounds in the speaker.