itsmejto said:
Well, no brag...just fact. I've been collecting old tube amps for many years. In the early 80's these were available through flea markets, house sales and newspaper advertisments for about 50 to 100 dollars. Of course this was before the resurgence in tubes became popular. And back then the name brand recognition was not as big as MacIntosh or Fisher. And I also have an affinity for Ampex and Nagra tape machines as well.
Victor
They were watts of plate dissipation in a single ended amp with no signal present, just DC dissipation. I have tested a lot of tubes at or above their rated dissipation. I look for glow on the plate and screen grid in a dark room. I run the EH KT88 in my SimpleSE at 400 volts (plate to cathode) and 100 mA. There is no visible glow in a dark room. I have also got a big Antek toroid and I have used it to "test" my amp at 525 volts of B+ which puts about 450 across the tube. Some tubes were beginning to glow at 100 mA and all were glowing at 115 mA, some brightly.
I have built hundreds tube amps over the past 40 years. Not all of them have been successful. Many of the failures came from stuffing too much heat into too small of a package. Not only will you have problems with component and tube lifetime, there will be issues with thermally related drift and possible runaway. Component values change with time and temperature. This can lead to an amp that can behave very differently after it has been on for a while.
I may be known for turning things up too far, but that is how you find the limits. Once you know the limits, you can go there with your own stuff, but something that you are going to sell to a possible tube newbie shouldn't run at the limit.
I am not telling you what to do. You can build what ever you want. If you intend to build amps and sell them successfully, they better work, and keep working for a long while. That is why I test my designs at conditions far beyond where any customer may use them. I over design them, and they last.
Thanks. I haven't had any time to work on it this year, but I plan to take it further some day. I have received several positive emails, but I also got a few that were really negative. I think that I really rattled some of the "sandophobic" crowd with that one!
Brett said:
Hi Brett,
That was the 2007 winning entry from an anual contest at Texas A&M University calling for the most appropriate definition of a contemporary term.
Holy mackerel... a Studer A80! What a machine! Sniff is right. I've never owned one and never will. Too much $$$ and no room.
We all know tube chassis get hot, always have, always will.
That's why there are high temperature components available for under chassis use. Some use cooling fans and extend the life and safety of these. I'm sure this thing will require some forced cooling and a well ventilated shelf. but to say the chassis is just too small may be a matter of opinion if you have seen some other high powered amps of yesteryear. Especially those used in enclosed wooden cabinets.
I considder this chassis to be large enough if the parts all fit. Afer all it's not rocket science.
Maybe a computer controlled air conditioning system would be advisable !!!!
The're tubes guys, hot is what they do.
That's why there are high temperature components available for under chassis use. Some use cooling fans and extend the life and safety of these. I'm sure this thing will require some forced cooling and a well ventilated shelf. but to say the chassis is just too small may be a matter of opinion if you have seen some other high powered amps of yesteryear. Especially those used in enclosed wooden cabinets.
I considder this chassis to be large enough if the parts all fit. Afer all it's not rocket science.
Maybe a computer controlled air conditioning system would be advisable !!!!
The're tubes guys, hot is what they do.
itsmejto said:
All of the electrolytics in those old wood encased amps failed. From heat. And that's certainly not the only thing that happened to those old amps, I've seen the insulation melted out of a transformer or two along the way. The tubes have minimum mounting distances from each other - not just "if they fit." Without even flipping to the datasheet, I feel confident in saying the ST70 chassis is too tight for KT88s running at max dissipation. And that's not even taking in to account that they don't make them like they used to.
It doesn't matter what you put it on ebay starting at... you could put it on there for a penny and that doesn't make you a better person for selling this to some one... it's going to sell for hundreds of dollars to someone wanting a reliable amp for their stereo - someone hoping to get "the sound" without having to shell out audiophile store prices. As long as you are selling it to an unsuspecting individual, you are not going to get any props here. And yes that is all it boils down to. If you had said my latest crazy project for me (my barn, my car, my anything...) people would be saying... crank it up... but you are deliberating taking advantage of the ignorance of ebay... and it's not ok. People will not want to help you do that.
itsmejto said:
Why stop at one? Can't you fit two in there...?
An externally hosted image should be here but it was not working when we last tested it.
HollowState said:
We carry VAC (Valve Amplification Company) here at the shop... the Phi Beta 110 integrated amp reliably gets 110w/ch (MEASURED!) at the outputs, with a pair of KT88s per side.
Even in near constant use (one person who has one from us, uses it like 10 hours a DAY) tubes have lasted in excess of 3 years. That's like 7500 hours so far...
Of course, Kevin Hayes is a pretty talented designer, who knows where the limits are... and this is a $22000 (TWENTY TWO THOUSAND dollar amp)... and no, I wouldn't expect the KT88s to last as long as they would in a Citation II or Dynaco MK3... but 7500+ hours out of modern production (EH) KT88s is not bad...
However- if I was the original poster, I'd be inclined to run something in screen-drive mode (6AV5/6JE6 or something like that), to get that kind of power in that small of a space. At least then, the tubes would be idling at close to Class B, which would SEVERELY reduce the heat under normal circumstances. Would at least give them half a chance of surviving in that cramped of a space...
Regards,
Gordon.
Wish I could take credit for it, but alas it is not mine. The gentleman's name is Jeff Davison. I'm not sure if he posts here. You can find the rest of the photos and read more about it here:
http://www.diytube.com/phpBB2/viewtopic.php?t=1289
http://www.diytube.com/phpBB2/viewtopic.php?t=1289
Wow !!!
That'll give some of the guys here a heart attack.
Nice job, very nice, but wait for all the negativity to come back on it.
PostPosted: Fri Jan 12, 2007 4:19 pm Post subject: Finished the wiring, another 10 lbs stuffed in a 2 lb bag Reply with quote
Now on to testing....
Anyway...thanks for all your help here in the forum.
Details:
Edcor 60 output transformers
2 Toroid Corp tube power transformers
Corcom power entry module with filter
2 C.Chong capacitor boards
Mapletree "Special Red" driver board.
Soundtastic Dyna ST-70 chassis
Dynakit cover.
Lotsa NOS RCA tubes
Object was to do a true dual mono 60 wpc amp with ST-70 wrapings as I like the nostalic style and form factor.
I was going to upgrade all the components on a stock ST-70 I got on eBay, but decided just to start from scratch with all new bits (NOS for the tubes)
I've grown to love solder fumes Yellow_Light_Colorz_PDT_15
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=2.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=4.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=5.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=7.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=10.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=12.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=15.jpg
That'll give some of the guys here a heart attack.
Nice job, very nice, but wait for all the negativity to come back on it.
PostPosted: Fri Jan 12, 2007 4:19 pm Post subject: Finished the wiring, another 10 lbs stuffed in a 2 lb bag Reply with quote
Now on to testing....
Anyway...thanks for all your help here in the forum.
Details:
Edcor 60 output transformers
2 Toroid Corp tube power transformers
Corcom power entry module with filter
2 C.Chong capacitor boards
Mapletree "Special Red" driver board.
Soundtastic Dyna ST-70 chassis
Dynakit cover.
Lotsa NOS RCA tubes
Object was to do a true dual mono 60 wpc amp with ST-70 wrapings as I like the nostalic style and form factor.
I was going to upgrade all the components on a stock ST-70 I got on eBay, but decided just to start from scratch with all new bits (NOS for the tubes)
I've grown to love solder fumes Yellow_Light_Colorz_PDT_15
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=2.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=4.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=5.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=7.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=10.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=12.jpg
http://s130.photobucket.com/albums/p280/jeffdavison/ST-70/?action=view¤t=15.jpg
Ty_Bower said:
Quite frankly I don't know why.
All that time and money (some expensive parts in that amp) all to turn around and save $50 on a chassis by stuffing it in a ST70. Not to mention how much the life of the amp as a whole has been shortened.
And then there is the aesthetics, the ST70 wasn't exactly ever a great looking amp - much less like this.
Since you were already at Antek, why didn't either of you get one of the great Parmetal amp cases they sell!! Doh!? Or two and make a set of monoblocks? They even have a
ebay store!!
itsmejto said:
If nostalgia was the motive, you should keep it original or very close.
I would like to point out that 1. The first thing I said no one was deliberately trying to be mean. and 2. You haven't listened to *ANY* of the criticism here, despite the fact it's valid criticism.
No one cares if that was an amp for your own use, the fact is you said, "I'm building it to sell on ebay - screw the sucker that gets it." Basically, more or less that was the gist of your post. It was clear, I'm doing this for my own fun to see if I can, who cares who ends up with the thing and has to maintain it...
All the "negativity" has been most valid - you stuck a chevy 350 in a yugo of sorts - again to dupe someone with no tube experience.
Let me be really clear about that: it's lame.
Tube amps at their worst are lethal. You have a responsibility to design and engineer safe and reliable equipment - whether you currently realize it or not.
And then that's not even getting to the fact you would have been better off restoring the ST70 and building your 80watt amp separate. The additional financial cost would have been minimal and this entire thread would have been avoided.
Seems that you really enjoy knocking other builders if it doesn't suit your standards. Now your'e complaining about someone elses build.
Perhaps you didn't read the bit about the weener safety resistor.
And as you are so concerned about me selling it on Ebay in this condition, to some poor unsuspecting person, did it ever cross your mind that someone might even want one like this ?
Besides which, I'd never sell it to someone who didn't know exactly what they are buying. (weener resistor included, no charge)
BTW, I also owned a Yugo.
For $3200.00 it was a great car.
Wish it had a v8 though.
Perhaps you didn't read the bit about the weener safety resistor.
And as you are so concerned about me selling it on Ebay in this condition, to some poor unsuspecting person, did it ever cross your mind that someone might even want one like this ?
Besides which, I'd never sell it to someone who didn't know exactly what they are buying. (weener resistor included, no charge)
BTW, I also owned a Yugo.
For $3200.00 it was a great car.
Wish it had a v8 though.
I guess I'm being naive. Buyer beware they say. As said already, "don't buy amp on ebay."
Shame you've not gotten anything out of this... you just keep taking it personally... which as i said and said again... is your fault and yours alone. You got this by saying you want to pawn it off on someone.. and no, it didn't occur to me (or any one else) that someone might want that.
People like you don't belong in DIY - even if you have the technical skills. When you can't take safety and common sense as a precursor to the greed for more power and you willingly ignore someone else's well being, you are dangerous, and we don't need people like you.
And again, just cause I think the amp looks bad - had nothing to do with my concerns. It was entirely the fact you are involving a 3rd unknowing party - and as such, no smart remarks or like minded build photos will redeem you.
So, let me say it again, I DON'T CARE what you do. I (and the others) only care cause your monstrosity is intended for someone else... an unsuspecting buyer. That is still lame.
What next? Advertise laptop computers for sale and then not ever send anything? After all, maybe someone WANTED to get ripped off...
Shame you've not gotten anything out of this... you just keep taking it personally... which as i said and said again... is your fault and yours alone. You got this by saying you want to pawn it off on someone.. and no, it didn't occur to me (or any one else) that someone might want that.
People like you don't belong in DIY - even if you have the technical skills. When you can't take safety and common sense as a precursor to the greed for more power and you willingly ignore someone else's well being, you are dangerous, and we don't need people like you.
And again, just cause I think the amp looks bad - had nothing to do with my concerns. It was entirely the fact you are involving a 3rd unknowing party - and as such, no smart remarks or like minded build photos will redeem you.
So, let me say it again, I DON'T CARE what you do. I (and the others) only care cause your monstrosity is intended for someone else... an unsuspecting buyer. That is still lame.
What next? Advertise laptop computers for sale and then not ever send anything? After all, maybe someone WANTED to get ripped off...
That would be interesting. 350 in a Vega, common. 350 in a Chevette, highly unstable at speed due to the short weelbase. 350 in a Supra, cool, my friend drove it daily for years till he got a Cadillac. It was well designed (by a felow engineer) and built. Building high powered cars requires rules, common sense, careful planning. Fortunately any NHRA sanctioned track will enforce those rules so that risk to humans is minimized.
High voltage electronics caries similar risks. There are several pages on my web site explaining those risks. At least my customers know what they are getting into.
I'm not even going to comment on the amp again, but:
I read about the weener "safety" resistor, please enlighten me as to what is does, and how you hook it up?
Been there, built that. The hotest thing on the bench was the 500 watt load resistor.
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