I feel its better to start a new thread since this amp isent very tubelab anymore.
I´m now using a circuit by Electra-print, a TDA2030 driving the grid of the 833A by a interstage transformer, im using a 230/24V transformer for this, however electra-print makes a special transformer just for this but i don´t have the 89 dollars it cost.
Here are a few pics:
Schematic:
Heres a video of a startup, tho with a tubeamp as driver, when replacing it with the ss driver, hum level went down alittle.
http://www.youtube.com/watch?v=zA1-IkewNtQ
I´m now using a circuit by Electra-print, a TDA2030 driving the grid of the 833A by a interstage transformer, im using a 230/24V transformer for this, however electra-print makes a special transformer just for this but i don´t have the 89 dollars it cost.
Here are a few pics:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Schematic:
An externally hosted image should be here but it was not working when we last tested it.
Heres a video of a startup, tho with a tubeamp as driver, when replacing it with the ss driver, hum level went down alittle.
http://www.youtube.com/watch?v=zA1-IkewNtQ
At least he had a go !
I looked at the video, the pics and the circuit and have to say well done in getting the beast to work; BUT a Microwave oven transformer as a SE OP trany AAA..R ! I can't deal with it.
I know it was free and your on a budget like me - but even if you wind your own on an old core, that would have been far better !
I cringe at using these doorstoppers even for a power transformer - because of the high leakage inductance, welded laminations; etc.
But if it works, maybe as a bass amp - then it's a start. Why a Solid state driver ? I can understand a computer case, at least with a prototype and maybe a Microwave tranny for the HV main Power supply.
But all in all - well done for having a go.
Cheers - Kimbal !
PS: - Before the days of microwave oven transformers - when I was 16yo and without any money - I built an 807 push pull amp as a guitar amp and used a standard power transformer from an old 5 valve tube AM radio as the Output Transformer. It sounded cr*p ! No highs and a very muddy bass. Audible distortion was not "too bad" on the mids and upper bass, but I had no Oscilloscope to really know for sure. Estimated power out was about 15 watts @ 20% distortion, if I was lucky.
The 285-0-285 volt @ 85 ma HT winding was connected across to the two 807 plates wire to the two op tubes with its C/T to the 400v B+ line. The 6.3 volt AC secondary was the 4 /8 ohm output; with all other windings left floating. Never again !
I looked at the video, the pics and the circuit and have to say well done in getting the beast to work; BUT a Microwave oven transformer as a SE OP trany AAA..R ! I can't deal with it.
I know it was free and your on a budget like me - but even if you wind your own on an old core, that would have been far better !
I cringe at using these doorstoppers even for a power transformer - because of the high leakage inductance, welded laminations; etc.
But if it works, maybe as a bass amp - then it's a start. Why a Solid state driver ? I can understand a computer case, at least with a prototype and maybe a Microwave tranny for the HV main Power supply.
But all in all - well done for having a go.
Cheers - Kimbal !
PS: - Before the days of microwave oven transformers - when I was 16yo and without any money - I built an 807 push pull amp as a guitar amp and used a standard power transformer from an old 5 valve tube AM radio as the Output Transformer. It sounded cr*p ! No highs and a very muddy bass. Audible distortion was not "too bad" on the mids and upper bass, but I had no Oscilloscope to really know for sure. Estimated power out was about 15 watts @ 20% distortion, if I was lucky.
The 285-0-285 volt @ 85 ma HT winding was connected across to the two 807 plates wire to the two op tubes with its C/T to the 400v B+ line. The 6.3 volt AC secondary was the 4 /8 ohm output; with all other windings left floating. Never again !
You may not believe it but this amp sound really good, and the freq response aint too bad either, and this is without any feedback what so ever, this rolloff is easily compensated for using an eq.
I used the electra-print ss driver because i dident have parts for a tube based driver, also after reading the electra-print tech blog about the opamp driver i thought it´d make the overall sound better since the TDA2030 driver will have a THD of 0.1% or less according to electra-print.
An externally hosted image should be here but it was not working when we last tested it.
I used the electra-print ss driver because i dident have parts for a tube based driver, also after reading the electra-print tech blog about the opamp driver i thought it´d make the overall sound better since the TDA2030 driver will have a THD of 0.1% or less according to electra-print.
I would like to know -
What sort of power output does this beast deliver ?
I assume the frequency response on the photobucket link was the green line ? What is you B+ rail and audio driver volts into the 833a ? A well designed SE 833 can deliever up to 150 watts RMS of audio into a speaker witha cherry red spot on the plate for normal operation. Does yours have any cherry red spot on the anode ?
It's interesting you say it sounds good, because some Australian tube audio hobbyists I emailed a couple of years ago said they were using a cheap $20 dollar line output audio transformer readily available in the local Altronic Electronics Shop; which gave a pretty good audible quality sound. I thought that was bad enough, but using a Microwave power transformer is really getting to the bottom of the bucket.
In the above project I quoted, the tubes driving the amp were 6CM5/ EL36. It may be of interest to some, but sorry it's not my way of doing things - but if it works as an alternative and you like the sound - OK go for it !
The full artical is as follows -
A Push-Pull Amplifier, featuring the 6CM5/EL36 and the Altronics-M1115 transformer.
The link is at >
http://home.alphalink.com.au/~cambie/6AN8amp/Grant_Wills_6CM5amp.htm
What sort of power output does this beast deliver ?
I assume the frequency response on the photobucket link was the green line ? What is you B+ rail and audio driver volts into the 833a ? A well designed SE 833 can deliever up to 150 watts RMS of audio into a speaker witha cherry red spot on the plate for normal operation. Does yours have any cherry red spot on the anode ?
It's interesting you say it sounds good, because some Australian tube audio hobbyists I emailed a couple of years ago said they were using a cheap $20 dollar line output audio transformer readily available in the local Altronic Electronics Shop; which gave a pretty good audible quality sound. I thought that was bad enough, but using a Microwave power transformer is really getting to the bottom of the bucket.
In the above project I quoted, the tubes driving the amp were 6CM5/ EL36. It may be of interest to some, but sorry it's not my way of doing things - but if it works as an alternative and you like the sound - OK go for it !
The full artical is as follows -
A Push-Pull Amplifier, featuring the 6CM5/EL36 and the Altronics-M1115 transformer.
The link is at >
http://home.alphalink.com.au/~cambie/6AN8amp/Grant_Wills_6CM5amp.htm
I have a orange spot on the plate, B+ is around 1500V i think, havent measured anything. This i think is alittle too much plate current so im gonna fiddle w the bias resistor to reduce plate glow to barely visible red. Judging from the color of the plate, maybe 100-150W, it dissipates around 800W in heat, 250-400W from the tube and another 400W from the transformers.
The TDA2030 driver puts out around 10V into the 24V winding of a lil 15VA donut on full volume, out on the secondary comes around 120V, atleast in theory.
The freq response in the pic is the white line, the green is THD vs freq, yes the THD look alittle funny, propably because the opt is held together with scotch tape and the fact that theres no interleaving in sight.
The original intention w this amp was to use it as a bass amp but it sounded so good that im reconsidering.
Someday when i have the money i consider ordering a opt from electra-print as well as that opamp drive transformer, maybe even a power transformer.
The TDA2030 driver puts out around 10V into the 24V winding of a lil 15VA donut on full volume, out on the secondary comes around 120V, atleast in theory.
The freq response in the pic is the white line, the green is THD vs freq, yes the THD look alittle funny, propably because the opt is held together with scotch tape and the fact that theres no interleaving in sight.
The original intention w this amp was to use it as a bass amp but it sounded so good that im reconsidering.
Someday when i have the money i consider ordering a opt from electra-print as well as that opamp drive transformer, maybe even a power transformer.
Tekko said:
If what you say is right, then I am impressed with the frequency response outcome.
As for tweeking the bias to reduce the red glow, this is not the best way to reduce plate dissipation; as you may slide the tube into it's nonlinear region and make it run in class B or C.
From memory anything around 1000 to 1200 volts for the plate voltage is fine (but higher is better) and around 100-150 ma quiescent plate current - assuming you have a good emmission 833A tube. Measure the voltage across the filament bias resistor and divide it by the resistance to get the plate / bias current. Just don't push the plate dissipation (plate volts divided by plate current for a triode) over 300 watts unless you use the 833 C or D which can take 450 watts. These have carbon anodes. But don't take these adjustment figures as the final word - check the data curves.
Yesterday i replaced the 230/24V donut with a 230/10V EI core transformer, due to the split bobbin design i lost everything above 1kHz so i tried the thing as a bass amd and oh my, this thing go so loud that the floor start vibrating, and the amp wasent even clipping yet.
In fact it worked so well that around 11pm two cops knocked on the door, but by then i had already turned it off.
In fact it worked so well that around 11pm two cops knocked on the door, but by then i had already turned it off.
Speaking of Cops coming to your door -
Back in the late 1970's when I was 18yo I built a real 1.2 kilowatt stereo amp ( 600 watts rms per channel ) with 24 output transistors in each channel ( 2N3055/MJ2955 ) running off a 15 amp split 90 volt power supply for each channel. I could run a radiator bar red or boil water with a sine wave signal with this beast.
Anyway I use to run it so loud playing - Black Sabbath, Deep Purple, and Jimi Hendrix, Judas Priest, etc; I had the police arrive at 4 pm in the afternoon (after school) one day to tell me to turn it off, as the neighbours complained during the day of the volume.
I also had my speakers catch on fire in my bedroom on another occasion with the same Amplifier - smoke belching out of the 8 1 inch dome tweeters when I was playing a new KISS record almost at full volume. The reapir cost was not cheap and the smoke was literally choking throughout the house. Alas my perents were not impressed.
At the time even my 200 watt RMS car amp I built then was so loud you could hear it across a football oval with the windows and doors shut on the vehicle. It pulled so much current from the alternator the car engine would run sluggish under load when I turned up the volume. Even these days my home made Amp would kick real *** compared to the crap on the market.
All in all the guys from my electronics class at TAFE college told me when they saw the sound gear at my house, their words were:-
"FAAARK ! Who needs drugs with a setup like this!" (Unquote).
Yes those were the days!
If you want to get into really big TUBE Amps then you may be interested in my information / post here as I am taking up a collection to buy a copy to share around>
http://www.diyaudio.com/forums/showthread.php?s=&threadid=143903
Back in the late 1970's when I was 18yo I built a real 1.2 kilowatt stereo amp ( 600 watts rms per channel ) with 24 output transistors in each channel ( 2N3055/MJ2955 ) running off a 15 amp split 90 volt power supply for each channel. I could run a radiator bar red or boil water with a sine wave signal with this beast.
Anyway I use to run it so loud playing - Black Sabbath, Deep Purple, and Jimi Hendrix, Judas Priest, etc; I had the police arrive at 4 pm in the afternoon (after school) one day to tell me to turn it off, as the neighbours complained during the day of the volume.
I also had my speakers catch on fire in my bedroom on another occasion with the same Amplifier - smoke belching out of the 8 1 inch dome tweeters when I was playing a new KISS record almost at full volume. The reapir cost was not cheap and the smoke was literally choking throughout the house. Alas my perents were not impressed.
At the time even my 200 watt RMS car amp I built then was so loud you could hear it across a football oval with the windows and doors shut on the vehicle. It pulled so much current from the alternator the car engine would run sluggish under load when I turned up the volume. Even these days my home made Amp would kick real *** compared to the crap on the market.
All in all the guys from my electronics class at TAFE college told me when they saw the sound gear at my house, their words were:-
"FAAARK ! Who needs drugs with a setup like this!" (Unquote).
Yes those were the days!
If you want to get into really big TUBE Amps then you may be interested in my information / post here as I am taking up a collection to buy a copy to share around>
http://www.diyaudio.com/forums/showthread.php?s=&threadid=143903
Speaking of BIG tubeamps, have you seen the 3kW amp using two 4-1000A´s ?
If no, here it is: http://www.audiophool.cjb.net/Misc/3Kpdf.pdf
Btw i did a freq response test on a 230/2x9V 20VA donut yesterday and found it has a FLAT freq response 20-20000Hz so this replaced the split bobbin EI core interstage transformer. I also crunched some numbers for a output transformer i think about winding.
If no, here it is: http://www.audiophool.cjb.net/Misc/3Kpdf.pdf
Btw i did a freq response test on a 230/2x9V 20VA donut yesterday and found it has a FLAT freq response 20-20000Hz so this replaced the split bobbin EI core interstage transformer. I also crunched some numbers for a output transformer i think about winding.
An externally hosted image should be here but it was not working when we last tested it.
Thanks for the data.
Yes I know of that 3 Kw amp from 1953/4 by Bereskin. Interesting design. A smaller almost identical artical was published just before the 3 Kw design. It was a 50 watt unit with 2x 807 tubes. Not so sure I like the choke at the input but even so.
Output transformer design is in both articals.
Yes I know of that 3 Kw amp from 1953/4 by Bereskin. Interesting design. A smaller almost identical artical was published just before the 3 Kw design. It was a 50 watt unit with 2x 807 tubes. Not so sure I like the choke at the input but even so.
Output transformer design is in both articals.
Don't be afraid to use fans; blower or muffin types. I realise acoustic noise and air flow are added engineering issues but you can minimize these problems with careful design.
Ideally a good air flow from a blower hose with a remote located fan would be ideal, but not very practical. If I owned my own home I would do this.
Though not done by the average DIY - the 833 I feel should be forced air cooled especially for Class A continous application.
Ideally a good air flow from a blower hose with a remote located fan would be ideal, but not very practical. If I owned my own home I would do this.
Though not done by the average DIY - the 833 I feel should be forced air cooled especially for Class A continous application.
Microwave tranny for SE output
I disagree with the idea that using a microwave tranny as audio op tranny is trolling the bottom. As Microwave trannies have to be made of the very best silicon steel in order to work at all. As they are run Hot at saturation. However if you measure the secondary inductance even with an 8 ohms load
in the 120 vac line , you will get a nice surprise. The cut off should be apx
30 hz or so for an se output with no modifications to the tranny other than
remove one end of the 2kv secondary from the case and insulate it and use
it for the plate lead instead. I am going to use a 6L6GC , should give apx
2222 ohms plate load and the 120vac will be 8 ohms. I don't what it will sound like until I try. But don't knock it until you have tried it.
I disagree with the idea that using a microwave tranny as audio op tranny is trolling the bottom. As Microwave trannies have to be made of the very best silicon steel in order to work at all. As they are run Hot at saturation. However if you measure the secondary inductance even with an 8 ohms load
in the 120 vac line , you will get a nice surprise. The cut off should be apx
30 hz or so for an se output with no modifications to the tranny other than
remove one end of the 2kv secondary from the case and insulate it and use
it for the plate lead instead. I am going to use a 6L6GC , should give apx
2222 ohms plate load and the 120vac will be 8 ohms. I don't what it will sound like until I try. But don't knock it until you have tried it.
I tried it. It sucked. The frequency response went from 60Hz to 140 Hz and there was ample distortion. Maybe the transformers that I used were junk, and your results may vary, but there is a lot of ground to make up. The experiment and a lot of other glowing tube experimentation is in the following thread. The MOT for OPT discussion starts around post #27.
http://www.diyaudio.com/forums/showthread.php?t=124527&highlight=simple
I built a "prototype" 833A amp a few years ago. I paid a transformer winder a decent sum of money to make me an OPT but it wouldn't do 20 Hz to 20 KHz, but it did make over 200 watts. I plugged my guitar preamp into it and annoyed the neighbors for a while and then took it apart. I never got around to building the final amp.
http://www.tubelab.com/833SE.htm
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