As some of you may have seen, I am looking to build a subwoofer amp to replace my current s/s piece. I am strongly considering a pair of 833's in p-p config. Sounds good on paper...but one BIG problem...TRANSFO'S !
I think I can come up with b+ from some older RF amp parts...I'll have to dig... but output is going to be a problem!
Any work arounds? Any alternatives?
Also...concerning a project like this (I have build a good deal of RF amps...and no what they cost..but am not familiar to much with AF). Is a $5-7k budget realistic for something like this?
Thanks
Dennis
I think I can come up with b+ from some older RF amp parts...I'll have to dig... but output is going to be a problem!
Any work arounds? Any alternatives?
Also...concerning a project like this (I have build a good deal of RF amps...and no what they cost..but am not familiar to much with AF). Is a $5-7k budget realistic for something like this?
Thanks
Dennis
A friend of mine had a custom xformer much like what you're looking for made by Peter Dahl.
Plitron also was in the running for that job, and seemed perfectly willing and able to supply one fairly reasonably. Apparently this is about the size of unit where it starts to make sense to use a toroid from an expense point of view, the savings from raw materials beginning to counteract the cost of thre complex winding.
You just have to love the 833s.
By the way, how are you planning on driving them?
Plitron also was in the running for that job, and seemed perfectly willing and able to supply one fairly reasonably. Apparently this is about the size of unit where it starts to make sense to use a toroid from an expense point of view, the savings from raw materials beginning to counteract the cost of thre complex winding.
You just have to love the 833s.
By the way, how are you planning on driving them?
Although their site doesn't list any P-P circuits for the 833, Lancroft used to offer push pull transformers for the tube. Currently their site is "under construction" but still offers some S.E. 833 circuits (among others).
http://www.users.bigpond.com/triode/
There was a company a while back called Shoreline (I think) that offered 833 monoblocks for some ridiculous amount, around 40K.
Personally, going through all the trouble of dealing with potentially lethal voltages and expense seems a bit extreme for a subwoofer amp, but hey, bragging rights don't come cheap!
http://www.users.bigpond.com/triode/
There was a company a while back called Shoreline (I think) that offered 833 monoblocks for some ridiculous amount, around 40K.
Personally, going through all the trouble of dealing with potentially lethal voltages and expense seems a bit extreme for a subwoofer amp, but hey, bragging rights don't come cheap!
I think I would be inclined to try cathode coupling the output tubes. The driver requirements would be extreme but could be handled by an interstage xfmer also used as phase splitter driven by a conventional P-P power amp. The benefit from throwing away voltage gain in the output stage would be in greatly simplifying the requirements of the output transformer. No high voltage on it and the turns ratio would be small so good HF response is possible at low cost. Output Z would be low even before negative FB was applied for good driver control. Heck, since you don't need HF response you might find a power transformer that would work as an output transformer. A toroidal power xfmer could give you full range fidelity and I might even have one.
Thanx for the inspiration to come up with this idea! That can be project number 4,018.
Thanx for the inspiration to come up with this idea!
That can be project number 4,018.
Everything I currently am working on is tube. It seems "out of place" to have a solid state fired sub. Also....believe it or not, after hearing a larger vtl piece firing a pair of Adire's...I am convinced...by all means that was the most acurate reproduction of low frequency I have every heard.
I have also played around with the idea of OTL. The biggest problem with the circuit design though is going to be compensating for the great impedence change on the newer large x-max pieces.
The driver stage is not of concern currently. But I would like to use RF tubes to stay with the theme...maybe some 811's or 813's... Only because this is what I have.
Thanks
Dennis
I have also played around with the idea of OTL. The biggest problem with the circuit design though is going to be compensating for the great impedence change on the newer large x-max pieces.
The driver stage is not of concern currently. But I would like to use RF tubes to stay with the theme...maybe some 811's or 813's... Only because this is what I have.
Thanks
Dennis
A few preliminary questions need to be answered:
- feedback?
- class of operation?
- power output?
Then you can start to consider the yin/yang part.
Since this is a SUB amp only, you can forget about the HF response from your output iron. Pretty much. You want major inductance for LF capability. Big *** core...
Cathode coupling the output stage is a definite possibility if only because you might find suitable iron more readily it makes it a plus.
The B+ required on an 833 is *very high.*
The 813 is a better choice for a big tube - as are 845s and 211s, both of which can be run in Class AB with appropriate bias. 811 will do ~150watts for a pair no problem and drive pretty easy.
Build a bridged pair of 811s and you've got a ton of power without too much big iron and too much expense, modest B+ requirements.
Not as much sex as a bigger bottle... but still it is a DHT!
Keep in mind that a non feedback tube amp will sound rather different than a feedback tube amp in the bass region...
I'd stay far away from Plitron for output iron in general - they're not so good with DC imbalances, eh? Just my observation of their specs...
Oh, if you use LP as a source, definitely HP the amp's stages @ ~8-10Hz... keep the subsonics out of the iron.
_-_-bear
- feedback?
- class of operation?
- power output?
Then you can start to consider the yin/yang part.
Since this is a SUB amp only, you can forget about the HF response from your output iron. Pretty much. You want major inductance for LF capability. Big *** core...
Cathode coupling the output stage is a definite possibility if only because you might find suitable iron more readily it makes it a plus.
The B+ required on an 833 is *very high.*
The 813 is a better choice for a big tube - as are 845s and 211s, both of which can be run in Class AB with appropriate bias. 811 will do ~150watts for a pair no problem and drive pretty easy.
Build a bridged pair of 811s and you've got a ton of power without too much big iron and too much expense, modest B+ requirements.
Not as much sex as a bigger bottle... but still it is a DHT!
Keep in mind that a non feedback tube amp will sound rather different than a feedback tube amp in the bass region...
I'd stay far away from Plitron for output iron in general - they're not so good with DC imbalances, eh? Just my observation of their specs...
Oh, if you use LP as a source, definitely HP the amp's stages @ ~8-10Hz... keep the subsonics out of the iron.
_-_-bear
transformer availability
Hi Sickss,
last year i finished my 833-amp. Not PP but SE. With a nice twist: ultra-parafeed.....in order to get rid of the massive amount of saturating DC in the OPT.
It is a full-range amp, and not just for the bass-region. Although the bass-output is immense. Talk about real authority here !
Jusy like you i was looking for a good transformer-supplier; if possible in the Netherlands so i good really SEE what the quality was. I had good experience with Heart (established Dutch firm.....doing this business now for 3 generations....very low profile).
They did almost all my transformers/coils for the project. And that's more than 30 pieces.
The output is an EI150-affair weighing in at 12 kg. Not because i needed that huge core (ultra-parafeed....no DC), but because i wanted a very well designed coupling between the 7 primaries/6 secondaries. With my 1400 V/200 mA that means large diameter copper.....large transformer.
Just for fun i inquired what a huge 833 PP-transformer will do:
- custom designed PP833;
- EI-180 transformer;
- stacked height=100mm;
- Armco 0.35 iron;
- combined 7-layer model (just like mine);
- isolation class 4 (kapton foil + Kraft-paper + vacuum impregnated;
- secondaries as 30 cm leads, etc, etc.
====== € 369 a piece ex VAT/shipping/etc.
Certainly not cheap.....but i can assure you that this is real quality.
I'll enclose some pictures.
About the rest of my design: A2-class (positive grid driven), 1400 V on plate, 5 K OPT, 100 Watt output, no feedback whatsoever.
The high voltage is not the most essential part.....take care of the 20 Ampere inrush for the filaments ! Seconds later it will stabilise to just 10 Ampere.......
And it does sound great !
Regards,
Reinout
Hi Sickss,
last year i finished my 833-amp. Not PP but SE. With a nice twist: ultra-parafeed.....in order to get rid of the massive amount of saturating DC in the OPT.
It is a full-range amp, and not just for the bass-region. Although the bass-output is immense. Talk about real authority here !
Jusy like you i was looking for a good transformer-supplier; if possible in the Netherlands so i good really SEE what the quality was. I had good experience with Heart (established Dutch firm.....doing this business now for 3 generations....very low profile).
They did almost all my transformers/coils for the project. And that's more than 30 pieces.
The output is an EI150-affair weighing in at 12 kg. Not because i needed that huge core (ultra-parafeed....no DC), but because i wanted a very well designed coupling between the 7 primaries/6 secondaries. With my 1400 V/200 mA that means large diameter copper.....large transformer.
Just for fun i inquired what a huge 833 PP-transformer will do:
- custom designed PP833;
- EI-180 transformer;
- stacked height=100mm;
- Armco 0.35 iron;
- combined 7-layer model (just like mine);
- isolation class 4 (kapton foil + Kraft-paper + vacuum impregnated;
- secondaries as 30 cm leads, etc, etc.
====== € 369 a piece ex VAT/shipping/etc.
Certainly not cheap.....but i can assure you that this is real quality.
I'll enclose some pictures.
About the rest of my design: A2-class (positive grid driven), 1400 V on plate, 5 K OPT, 100 Watt output, no feedback whatsoever.
The high voltage is not the most essential part.....take care of the 20 Ampere inrush for the filaments ! Seconds later it will stabilise to just 10 Ampere.......
And it does sound great !
Regards,
Reinout
Attachments
finished amp
Hi Sickss,
As promised a picture of my 833 amp. Not for only bass-output.
Your design: PP 833......what is the speaker you're going to drive. Or are you planning to power up a stadium ?!
Picture only one channel: upper part audioamp. Lower part the external power supply.
Reinout
Hi Sickss,
As promised a picture of my 833 amp. Not for only bass-output.
Your design: PP 833......what is the speaker you're going to drive. Or are you planning to power up a stadium ?!
Picture only one channel: upper part audioamp. Lower part the external power supply.
Reinout
Attachments
Thanks Reinout...I have already shot an email to heart.
The price you quoted ...is that NLG? the conversion should put it about 225 bucks if my math is right....I received a quote from a local source....about 3 times that amount! I hope they get back to me.
As far as output is concerned. I am currently dissipating 2200 watts into 3 subs, solid state. I could use a little more...and would love to get away from the clipping of the solid state amp.
I have used the 833 in RF....this is a very simple circuit design. I am not very familiar with controlling the output on a audio design. What would be the problems associated with OTL? Is their anyway to model this?
Also, how much lead time does heart normally need? I would like to get going on this ASAP.
I have included a link to the current subs I am using...this may change a great deal until the project is complete...but for now These are the most musical drivers I have found.
www.reaudio.com
((model 15 XXX)
Thanks for all the help!
Dennis
The price you quoted ...is that NLG? the conversion should put it about 225 bucks if my math is right....I received a quote from a local source....about 3 times that amount! I hope they get back to me.
As far as output is concerned. I am currently dissipating 2200 watts into 3 subs, solid state. I could use a little more...and would love to get away from the clipping of the solid state amp.
I have used the 833 in RF....this is a very simple circuit design. I am not very familiar with controlling the output on a audio design. What would be the problems associated with OTL? Is their anyway to model this?
Also, how much lead time does heart normally need? I would like to get going on this ASAP.
I have included a link to the current subs I am using...this may change a great deal until the project is complete...but for now These are the most musical drivers I have found.
www.reaudio.com
((model 15 XXX)
Thanks for all the help!
Dennis
Just curious, how loud is the music you are listening to? I have an SE 845 driving 89db speakers with plenty of headroom. What brand of sub needs 2200 watts of driving power? It sounds very inefficient to me.
What does anyone think about running some big triodes in class B for maximum power?
What does anyone think about running some big triodes in class B for maximum power?
tranny reply
Sorry Sickss,
just as Jeff Mai noted....it is in euro's. € 369 is (exchange rate 1.3 - ish) around $ 480 US. Certainly not cheap.....but i do hope you never thought that a 833-based amp was going to be cheap in the first place.
I can stand for the quality. To be honest i delivered special kapton-foil to the company to be used in this design. Normally the isolate primaries/secondaries with the good/classical Kraft paper. with their vacuum impregnation and 12 hours hardening (!) in an oven you get a real solid transformer. But the Kraft-paper is only good for 1 kV. In order to go to higher voltages.....they standard multiply the paper to come to the required isolation class. But that will take up much winding room....so less space for copper winding....so thinner wire (ratio's will be fixed)....so resistance.....AAAARRRRGGHHHH.
I bought a roll of Kapton-foil. Extremely thin....but good for 7.5 kV ! And ordered my transformers with a mixed combination of Kraft-paper + Kapton-foil. The foil for the isolation; the paper for soaking up the laquer which after the over treatment will be as hard as a rock.
When you want those trannies.....i'll "donate" the Kapton-foil for this project. It is bloody expensive but i like to see more 833-amps around.
Th picture shows the EI96-size interstage (interstage 300B to 833A) and the EI126 output transformer.
"Your" EI180 is twice the size......please do count in postage.....
Simple question from my side: i believe a EI150 will do nicely. large enough diameter copper; no DC (PP-design)......
Leadtime can be fast enough.....the company is not really promoting these products (there is much more money to be earned as importers/distributors of audio-gear) so if you want to proceed......i offer to be your middle-man. It works always better if there is some "pressure". No money involved !!!!!
If you want i'll find out the difference for my pricing (will be 369 without VAT) and your USA-pricing (can be without VAT ????).
Reinout
Sorry Sickss,
just as Jeff Mai noted....it is in euro's. € 369 is (exchange rate 1.3 - ish) around $ 480 US. Certainly not cheap.....but i do hope you never thought that a 833-based amp was going to be cheap in the first place.
I can stand for the quality. To be honest i delivered special kapton-foil to the company to be used in this design. Normally the isolate primaries/secondaries with the good/classical Kraft paper. with their vacuum impregnation and 12 hours hardening (!) in an oven you get a real solid transformer. But the Kraft-paper is only good for 1 kV. In order to go to higher voltages.....they standard multiply the paper to come to the required isolation class. But that will take up much winding room....so less space for copper winding....so thinner wire (ratio's will be fixed)....so resistance.....AAAARRRRGGHHHH.
I bought a roll of Kapton-foil. Extremely thin....but good for 7.5 kV ! And ordered my transformers with a mixed combination of Kraft-paper + Kapton-foil. The foil for the isolation; the paper for soaking up the laquer which after the over treatment will be as hard as a rock.
When you want those trannies.....i'll "donate" the Kapton-foil for this project. It is bloody expensive but i like to see more 833-amps around.
Th picture shows the EI96-size interstage (interstage 300B to 833A) and the EI126 output transformer.
"Your" EI180 is twice the size......please do count in postage.....
Simple question from my side: i believe a EI150 will do nicely. large enough diameter copper; no DC (PP-design)......
Leadtime can be fast enough.....the company is not really promoting these products (there is much more money to be earned as importers/distributors of audio-gear) so if you want to proceed......i offer to be your middle-man. It works always better if there is some "pressure". No money involved !!!!!
If you want i'll find out the difference for my pricing (will be 369 without VAT) and your USA-pricing (can be without VAT ????).
Reinout
Attachments
reinout,
That pricing is still very acceptable. I am hoping to keep a budget of 5-7K usd. If not...oh well, I believe it can be done for less than half...but I wany a nice looking piece also.
I will spend some more time this weekend modeling the output stage...Hopefully I can get moving on this next week. I will let you know. And I certainly appreciate your offer.
astouffer...very loud. and I am dissipating that power across 3 subs, not 1.
Still no response on a OTL design?
Thanks
Dennis
That pricing is still very acceptable. I am hoping to keep a budget of 5-7K usd. If not...oh well, I believe it can be done for less than half...but I wany a nice looking piece also.
I will spend some more time this weekend modeling the output stage...Hopefully I can get moving on this next week. I will let you know. And I certainly appreciate your offer.
astouffer...very loud. and I am dissipating that power across 3 subs, not 1.
Still no response on a OTL design?
Thanks
Dennis
OTL = Output Transformer Less
In other words there is nothing between the tube(s) and the load. If the load is 8 ohms, the output impedance needs to be 8 ohms or lower, or else the power transferred drops. The greater the mismatch the less power transferred.
An 833 is a very high plate Z tube, as apparently you already know.
The only possibility is to couple using the cathode, which then makes it unity gain, meaning you need to swing the grid a huge amount of volts - a design problem for sure.
And then the cathode probably won't be anywhere near as low a Z as you need...
The typical OTL is a "totem pole" arrangement using multiple tubes to acheive close to the requisite output impedance - and using feedback. Typically used are tubes like the 6336 and the Russian 6C33C.
But to get hundreds of watts, or even a hundred watts in OTL you need quite a large bank of tubes...
There are some variations in design that are worth considering if you are going to build an OTL, but I'd probably not opt for an OTL as a sub amp...
A suggestion for yuks - try putting a very large 1 or 2 ohm resistor in series with your subs and see if that makes them sound anything like they did with the tube amps that you liked with them? That will reduce the damping factor down to close to what a "normal" feedback type tube amp would have (on the order of <10) as opposed to the DF likely with your high power solid state amps which is >100 and maybe into the thousands...
_-_-bear
In other words there is nothing between the tube(s) and the load. If the load is 8 ohms, the output impedance needs to be 8 ohms or lower, or else the power transferred drops. The greater the mismatch the less power transferred.
An 833 is a very high plate Z tube, as apparently you already know.
The only possibility is to couple using the cathode, which then makes it unity gain, meaning you need to swing the grid a huge amount of volts - a design problem for sure.
And then the cathode probably won't be anywhere near as low a Z as you need...
The typical OTL is a "totem pole" arrangement using multiple tubes to acheive close to the requisite output impedance - and using feedback. Typically used are tubes like the 6336 and the Russian 6C33C.
But to get hundreds of watts, or even a hundred watts in OTL you need quite a large bank of tubes...
There are some variations in design that are worth considering if you are going to build an OTL, but I'd probably not opt for an OTL as a sub amp...
A suggestion for yuks - try putting a very large 1 or 2 ohm resistor in series with your subs and see if that makes them sound anything like they did with the tube amps that you liked with them? That will reduce the damping factor down to close to what a "normal" feedback type tube amp would have (on the order of <10) as opposed to the DF likely with your high power solid state amps which is >100 and maybe into the thousands...
_-_-bear
Re: Re: finished amp
There's a lot of info about this amp in another thread starting with this post:
http://www.diyaudio.com/forums/showthread.php?postid=328753#post328753
It's a fantastic effort!
bear said:
There's a lot of info about this amp in another thread starting with this post:
http://www.diyaudio.com/forums/showthread.php?postid=328753#post328753
It's a fantastic effort!
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