I am sorry if I came across as not wanting to listen! Not the case. I was torn by what you were saying and what a man that has been designing and building the worlds most beloved amps since the 60's. What to do?
Your best friend says your wife is cheating on you, you ask the wife. "hell no" now who do you believe??
WO
Your best friend says your wife is cheating on you, you ask the wife. "hell no" now who do you believe??
WO
Anyway, my sincere apologies for being so negative.
As I said, I wish you luck. We actually do want you to succeed. This is after all your dream. Maybe your experiments could be a lesson to us all too. Nothing ventured nothing gained. Since you already have most of the parts at hand, perhaps you can try it out. But as loren put it, maybe you need to review how you'd like to get it done. Sometimes we do jump into the deep end and we can either swim or sink. AS we have ALL assured you, we wish for you to swim
Regarding your rhetorical question at the end.. it does matter if your best friend is after your wife
As I said, I wish you luck. We actually do want you to succeed. This is after all your dream. Maybe your experiments could be a lesson to us all too. Nothing ventured nothing gained. Since you already have most of the parts at hand, perhaps you can try it out. But as loren put it, maybe you need to review how you'd like to get it done. Sometimes we do jump into the deep end and we can either swim or sink. AS we have ALL assured you, we wish for you to swim
Regarding your rhetorical question at the end.. it does matter if your best friend is after your wife
The man has been building guitar amps.
That is why he continually recommends that stuff to you. It's what he knows to recommend when you ask. How could he possibly recommend otherwise?
I can imagine you asking him: "Can this amp be used for a stereo?" He'd say "sure". I'd bet he never told you it would be the best sounding HIFI amp you ever heard.
It might sound OK, as you'll only ever use less that a watt. It might sound like crap. But, you admit you don't care what it sounds like, it's just for the "wow factor". So, why worry about it?
That is why he continually recommends that stuff to you. It's what he knows to recommend when you ask. How could he possibly recommend otherwise?
I can imagine you asking him: "Can this amp be used for a stereo?" He'd say "sure". I'd bet he never told you it would be the best sounding HIFI amp you ever heard.
It might sound OK, as you'll only ever use less that a watt. It might sound like crap. But, you admit you don't care what it sounds like, it's just for the "wow factor". So, why worry about it?
2 guy's are out for a walk in the neighborhood, One looks over and see a dog in a yard licking himself, Looks over at his buddy and say's "I sure wish I could do that. " Friend replies,
"I would try and pet him first!"
WO
"I would try and pet him first!"
WO
Anyway, my sincere apologies for being so negative.
As I said, I wish you luck. We actually do want you to succeed. This is after all your dream. Maybe your experiments could be a lesson to us all too. Nothing ventured nothing gained. Since you already have most of the parts at hand, perhaps you can try it out. But as loren put it, maybe you need to review how you'd like to get it done. Sometimes we do jump into the deep end and we can either swim or sink. AS we have ALL assured you, we wish for you to swim
Regarding your rhetorical question at the end.. it does matter if your best friend is after your wife
I never said anything about not caring about the quality of the music it produces?? I am not trying to throw my $$ out the window?
WO
WO
Do you really think he has only built guitar amps? And that he does not understand the differences between the Guitar amp and HI-FI. You sure are not giving this man any credit for his years in tubes amd amp design.
WO
WO
Last edited:
His expertise is with guitar amps. It's like asking a pediatrist to help you with with tonsillitis.
Here are my first recommendations.
I would use the OPTs you have, but run them with two KT88s instead of four. This better matches the OPT impedance.
If they don't work out, you can trade/sell them for something better.
Use the 6550s as starter tubes. You may want to consider trying KT88s or even KT120s as an experiment later.
For the power transformer the first thing that comes to mind is the 378CX by Hammond. It's big and weighty. It will be enough to run both channels, but ideally I would build two mono blocks because you can always rip it up or modify it and have plenty of transformer power left.
As for a schematic, I am thinking of the Mullard as the easiest and safest to build. You will not be able to go the Ultrlinear route, but that is not that big of a loss.
I would build these with the idea of making changes as time goes on. You may want to swap tubes, circuitry, and transformers as you see fit. Making the mechanical chassis reconfigurable will make changes possible.
With two KT88/6550s per channel you will have more than enough power (and heat) to drive your speakers to insane volumes.
Execute the design in a nice package and you will have plenty of WOW factor and the satisfaction that you not only have nice eye candy, but something that performs very well.
Can someone suggest a good schematic?
You also need to start designing a power supply.
What electronics knowledge do you have?
Since you have the OTs already, I would not abandon the project. Just be aware that the power will be reduced from the 160 Watt spec for a 30 Hz or 20 Hz response, which is typically spec'd for Hi-Fi. You will have plenty of power anyway. The fact they are rated at 160 Watt and not 200 Watt tells me it is an honest rating with no Crest factor fudging. (in fact it indicates the Edcors are fudged upward by 25%) The high freq. spec is fine, obviously they are interleaved wound (unlike many guitar amp OTs). So you do have good OTs, just a little off the goal/mark stated earlier for 4 tubes, 200 Watt.
The 5 K Zpri should work fine with a pair of tubes. But seems too low for a quad of the usual suspects. The lack of UL taps can be overcome by either global feedback or local feedback (to lower the output Z for the speaker damping factor and for lower distortion). Local Schade (output plate to grid resistive) feedback has been quite popular here lately, check out the Pete Millett Red Board (Engineer's Amp) thread Tubelab mentioned earlier (post #16). You can't go wrong with that design.
http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html
On the power xfmr., I would check to see what its specs are before buying. The (2nd) schematic that you posted has the 12.5 lb'er OT in it, but is using a voltage doubler power xfmr. In fact, it's the 15 lb'er $15 boat anchor xfmr (Ebay) that was making the rounds here earlier for the Millett amp. But you may prefer to go with a more conventional non-doubler power transformer.
The 5 K Zpri should work fine with a pair of tubes. But seems too low for a quad of the usual suspects. The lack of UL taps can be overcome by either global feedback or local feedback (to lower the output Z for the speaker damping factor and for lower distortion). Local Schade (output plate to grid resistive) feedback has been quite popular here lately, check out the Pete Millett Red Board (Engineer's Amp) thread Tubelab mentioned earlier (post #16). You can't go wrong with that design.
http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html
On the power xfmr., I would check to see what its specs are before buying. The (2nd) schematic that you posted has the 12.5 lb'er OT in it, but is using a voltage doubler power xfmr. In fact, it's the 15 lb'er $15 boat anchor xfmr (Ebay) that was making the rounds here earlier for the Millett amp. But you may prefer to go with a more conventional non-doubler power transformer.
Last edited:
I have seen this before too.
I can understand. I currently have a 250 watt tube amp connected to my 96 db horn speakers. It sounds real good too. The neighbors love it! Yes, the average power output will be in the 1 watt range and many big amps don't do 1 watt well. You need one that does.
Yes, I build big nasty amps sometimes, but the ones that I design for other people to build are "simple" so that a first time builder can get them to work. The biggest one makes 10 to 30 WPC.
I offered my opinion about a design created by another EE that can be cranked into the desired power range relatively easilly in a previous post....Yes, I am recommending someone elses design....because It has withstood the Tubelab torture test up to 250 WPC, and several people have built it at various power levels.
I can state that I am an Electrical Engineer and I am writing this from my desk in the lab at a Motorola plant where I have worked for 38 years. I have been building audio amps for a bit longer than that, tube and solid state, guitar and HiFi. I have offered my opinion twice in this thread with no response so I didn't look back much, but I will try again.
First let me state an opinion that I have found to be true over the past 25 years or so.
The probability of success in a construction project goes down as the complexity and power level goes up. This is true for audio amps, RF amps, and automobile engines (all things that I have built and blown up).
The probability of success in these endeavors goes up as the skill and experience level of the builder goes up.
The cost and skill to repair a minor build error goes way up as the power level increases. A little oops in a 100 HP engine or 10 watt amp may cause a blown fuse or a blown head gasket. A little oops in a 700 HP Nascar engine will send a rod through the block scrapping the entire $40K engine, and a little oops at 700 volts can set an OPT on fire, shatter tubes, and KILL the builder!
There have been threads on this forum discussing amplifier builds in the 100 WPC to 500 WPC range, but search and search hard.....How many of these threads resulted in a BUILT, WORKING AMP? Not many.
I am not trying to scare you off, I am just explaining reality from my perspective. There is no quicker way to kill the enjoyment of a new hobby than to spend a bunch of money on something, flip the switch and watch it smoke. It then sits in the corner for a year or so and gets sold on Ebay.....
NOW, from the other side of the coin, I am the kind on guy who will build something that has little probability of success, and a good possibility of blowing up, and with fire extinguisher in hand flip the switch and watch....sometimes from behind a thick piece of Lexan. I have just learned to do it cheaply. That includes searching for bargain OPT's.
Many of my succesful HiFi amps use OPT's that were designed for guitar amps. I got a bunch cheap on Ebay about 10 years ago for building guitar amps. They were rated for "80 watts from 80 Hz to 4 KHz", yeah that sucks, but..... I bought a few took one apart and found NO interleaving whatsoever, again that sucks, but...... I tested them. I took a vintage Scott HiFi amp got it connected it up and listened for a while, then wired two of my bargain transformers into it and listened some more. Wait...I am hearing the cymbals and other high frequency sounds very clearly. How can this be with a 4KHz transformer. So I built a HiFi amp with a pair of those transformers and some 6550's. It sounded good, real good. And the frequency response measured 25 Hz to 25 KHz at 30 WPC too. I sold that amp, and more like it and that's how Tubelab got started. So you can make a good HiFi amp with a guitar amp transformer.....
Can you make a good HiFi amp with the guitar amp transformers that YOU have? I don't know. I looked at them about a year ago, went to the Risson web site, and Googled around a bit, and decided not to spend my money on a pair. I have NOT seen any evidence of a succesful HiFi design built with them. Now, if you succeed, I will go buy some before the feeding frenzy drives the price up. As I mentioned in a previous post, another forum member whose measurements I trust has measured those transformers and found them to me about 7000 ohms, not 5000. So the first thing that needs to be done is to find out if your transformers will work, and how much power you can squeeze through them and maintain HiFi.
The schematic fragment that you posted shows 700 volts of B+ to give 160 watts using these OPT's. You will need around 600 volts or more to get 100 watts. I am currently getting 125WPC with 600 volts and a 3300 ohm transformer. The 6550's being made in Russia and China today will likely fail at the 600+ volt level. They will certainly not take 700 volts! The Fender schematic calls for "special design" 6550's. I'm guessing that you can't get these at Sam Ash anymore. I am not sure about the KT120's since some users report failures and since they aren't cheap, I'm not trying them.
I have found that bargain OPT's work best when presented with a very low driving impedance. This usually means triodes, but triodes at 100+ WPC don't come cheap. We can emulate triodes by using local feedback on a pentode as discovered by Schade back in the 1930's. So we need a big pentode that can eat 700 volts and smile.
Tony, you convinced me to get some. I haven't really cranked them up yet, but they are rated for only 600 volts. To get 120 WPC you need 3500 ohm transformers.
So, what type of tube will work here? The sweep tube made by the zillions for color TV sets. The wimpiest are rated for 660 volts (not enough) and the big guys go for 990 volts (now were talking). They also have peak current capabilities of over an amp for big fat bass notes, and were designed for operation several hours a day at full power.
What kind of circuit uses TV tubes and Schade feedback, and has been known to crank out gobs of power, and has been built by dozens of builders at power levels from 18 WPC to 125 WPC? I, don't know but it's been mentioned here twice before.
Will it work with your OPT's. Yes, I am certain that you can build a red board, connect your OPT's and get sound. The quality of the sound and the amount of power can't be easilly determined since nobody has an ACCURATE assesment of those OPT's in a HiFi environment yet. You can always use different OPT's if you don't like the result. I can tell you that I am cranking 125 WPC out of my red board using the same little guitar amp OPT's that I got on Ebay 10 years ago. I have pictures of a nice unclipped sine wave at 70 watts and 40 Hz flowing through them while driven by the red board. The same OPT's saturate at 30 watts and 40 Hz when driven by EL84's.
You don't want that much power with Khorns, 1 watt will bring into great listening Db level. You are going to waste a lot of power and it won't sound as good at low volume as a properly setup low wattage amp (these speakers are made for efficiency). The best I have heard through heritage klipsch speakers are nosvalves VRD's made by Craig Otsby. They are 5AR4 rectified direct coupled 60 watt monoblocks that are built to run lots of different output tubes (very loud for 60 watts and can't believe the bass authority). Although good luck trying to get a schematic from Craig. I would try to build an amp around the speaker for best results, and I would stay away from "high power"
Last edited:
Try this proven circuit. www.diytube.com/phpBB2/viewtopic.php?t=4760
On the diytube.com site under diy hifi under " Koren Local Hero & Mods"
In his tests it works well with Pentodes and has no Global NFB. If you run at 40W/CH you shoud get a very good bandwidth out of your OPT just like Gregg is in the thread using Dynaco A-431 Mark III OPT transformers designed for 60W/CH. He is getting 11HZ to 46KHZ at Full Power (40 Watts)
As mentioned the more power you run through those OPT transformers the less bandwidth you'll get.
That should work nice for your speakers. I'm sure your 6550 tubes would work too if B+ is kept reasonable. Shouldn't be hard to do and he is selling boards too.
If that doesn't work maybe you could build a Killer guitar amp and get your money back or more!
On the diytube.com site under diy hifi under " Koren Local Hero & Mods"
In his tests it works well with Pentodes and has no Global NFB. If you run at 40W/CH you shoud get a very good bandwidth out of your OPT just like Gregg is in the thread using Dynaco A-431 Mark III OPT transformers designed for 60W/CH. He is getting 11HZ to 46KHZ at Full Power (40 Watts)
As mentioned the more power you run through those OPT transformers the less bandwidth you'll get.
That should work nice for your speakers. I'm sure your 6550 tubes would work too if B+ is kept reasonable. Shouldn't be hard to do and he is selling boards too.
If that doesn't work maybe you could build a Killer guitar amp and get your money back or more!
Last edited:
"Try this proven circuit. diytube.com :: View topic - Koren Local Hero and Mods
On the diytube.com site under diy hifi under " Koren Local Hero & Mods" "
Nice driver local CFB design. Puts more gain in the local feedback loop than the usual plate to grid Schade scheme. I think I would go for something with more gm than that 12AU7 though. To reduce the drive requirement of the splitter. With better linearity than a 12AU7 too.
On the diytube.com site under diy hifi under " Koren Local Hero & Mods" "
Nice driver local CFB design. Puts more gain in the local feedback loop than the usual plate to grid Schade scheme. I think I would go for something with more gm than that 12AU7 though. To reduce the drive requirement of the splitter. With better linearity than a 12AU7 too.
Last edited:
With the appropriate circuit one can get around that problem........just requires experience.
richy
I would love to learn more. I would suspect that there must still be an advantage to the UL winding over circuity?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.