Does anyone know where I can get a schematic for the use of a 42 power pentode (from a 30's radio reciever) as a single ended amp?
I also have a 12AT7 I can use for a preamp, along with a slew of 12au6's , 12be6's, etc etc... yes I got them out of an old radio. I also got a nice usable 35c5 out of the small radio.
I also have a 12AT7 I can use for a preamp, along with a slew of 12au6's , 12be6's, etc etc... yes I got them out of an old radio. I also got a nice usable 35c5 out of the small radio.
Dear ThSpeakerDude88,
Check out this page for 42's datasheet.
http://frank.pocnet.net
With the datas included in the datasheet you will be able to design a simple class-A SE amp with that nice tube.
Regards,
Check out this page for 42's datasheet.
http://frank.pocnet.net
With the datas included in the datasheet you will be able to design a simple class-A SE amp with that nice tube.
Regards,
alright, thanks! I see that this tube is the same as a 6F6 (correct me if I'm wrong 
)
I guess 3 watts would be really great , but it looks like thats at a considerable amount of distortion. Maybe a push-pull AB2 setup would be best? Another thing to consider, If I'm going to use a class A/B setup, would different tubes be better?
I'd just like to order some extras to have around from ebay
) I guess 3 watts would be really great , but it looks like thats at a considerable amount of distortion. Maybe a push-pull AB2 setup would be best? Another thing to consider, If I'm going to use a class A/B setup, would different tubes be better?
I'd just like to order some extras to have around from ebay
I dropped the 42/6F6 from my "short list" quite some time ago due to the distortion problem. It may not be that big of a deal for a radio, but unacceptable for high end audio. You'd do much better with the 6V6. Similar power output, working voltages, and gain, but with a good deal less distortion. You could run the 6V6's as a class AB1, as pentodes with NFB. Or run them as triodes without NFB.
Either way, they'll sound a whole lot better.
ooo triode w/o nfb would be nice, although I would not have much power. I think I'll go with a 6L6 pp combo for 40 watts or a se for 10. What I'm really aiming at is a nice sounding 20 watt duL mono block setup. 20 watts would be easy in pp ab1 mode, but a class A SE 20 watt monoblock would requier a lot of power to run wouldnt it, not to mention be expensive?
A 20 watt SE triode amplifier built according to current audiophile criteria (2 X 300B per channel) would definitely be expensive, and would dissipate 80 to 150 watts per channel.
It would be possible to build a 20 WPC SE amplifier for much less money if you use parts that are less "in vogue". 3 X KT88 (triode wired) per channel would be cheaper, or 3 X TV sweep tubes, find cheap ones with sufficient screen grid ratings for triode operation.
I am partial to surplus transmitter tubes myself, or new Chinese 845's, 40 watts per channel, serious bass, the only drawback is the need for 1100 volts!
Diagram on my web site: http://www.tubelab.com/845SE.htm
It would be possible to build a 20 WPC SE amplifier for much less money if you use parts that are less "in vogue". 3 X KT88 (triode wired) per channel would be cheaper, or 3 X TV sweep tubes, find cheap ones with sufficient screen grid ratings for triode operation.
I am partial to surplus transmitter tubes myself, or new Chinese 845's, 40 watts per channel, serious bass, the only drawback is the need for 1100 volts!
Diagram on my web site: http://www.tubelab.com/845SE.htm
ok... I have been sucsessfully scared away from a high powered SE setup because of prices and insanly high voltages needed 
LOL
I think for my first design, I will try a typical push pull setup. I want something that will be relativly cheap to build, have a very good snr ratio , and obviously sound pretty nice. I may consider a much lower powered SE setup later, unless I can find a cheap tube that will do what I want it to do.
hmm...
how hard would 10 watts be? maybe 5 if that requiers too high of a plate voltage or is too 'spensive. I'm really just designing my first tube amp.. so I want something thats not gonna be expensive, but I dont want it to sound like total crud either!
LOL
I think for my first design, I will try a typical push pull setup. I want something that will be relativly cheap to build, have a very good snr ratio , and obviously sound pretty nice. I may consider a much lower powered SE setup later, unless I can find a cheap tube that will do what I want it to do.
hmm...
how hard would 10 watts be? maybe 5 if that requiers too high of a plate voltage or is too 'spensive. I'm really just designing my first tube amp.. so I want something thats not gonna be expensive, but I dont want it to sound like total crud either!
For a 15 Watt push pull amp it would be hard to beat a pair of 6BQ5's/EL84 tubes. This is probably the most common P-P amp design around, and plenty of schematics are on the web. For slightly more power there is the 6V6 P-P amp, also common and good sounding. Either of these would be relatively cheap to build.
If 5 watts is enough, a SE amp could be built with 6L6's, EL34's or KT-88's, one tube per channel. Simpler circuit than P-P, and no crazy voltages required. For a budget SE amp the Hammond 125CSE output transformer is hard to beat at $30.
If 5 watts is enough, a SE amp could be built with 6L6's, EL34's or KT-88's, one tube per channel. Simpler circuit than P-P, and no crazy voltages required. For a budget SE amp the Hammond 125CSE output transformer is hard to beat at $30.
sweet! just what my budjet wanted to hear
I think a single 6L6 or kt88 would be nice, I haven't seen an el34 I don't think.. will look up!
would a pp pair of 6L6 monoblocks sound good?
I know the 6V6's in pp make 19 watts, I believe the 6L6's can produce 40 watts, so 20 watts would be at considerably low distortion.
By the way, I have never heard a 'proper' tube amp, just the old radios that I mess with. How does their SNR compare to transistor amps? The chipamp I built has a SNR around 110 db, its dead silent when turned on, even at full volume , signal or no signal
can a tube amp come close to that, and if properly designed , will there be any hum?
I think a single 6L6 or kt88 would be nice, I haven't seen an el34 I don't think.. will look up!
would a pp pair of 6L6 monoblocks sound good?
I know the 6V6's in pp make 19 watts, I believe the 6L6's can produce 40 watts, so 20 watts would be at considerably low distortion.
By the way, I have never heard a 'proper' tube amp, just the old radios that I mess with. How does their SNR compare to transistor amps? The chipamp I built has a SNR around 110 db, its dead silent when turned on, even at full volume , signal or no signal
can a tube amp come close to that, and if properly designed , will there be any hum?
It is possible to build a tube amp with zero hum, if you use a good power supply, good physical isolation between the power supply and the amplifier, and (here is the controversial part) DC on the filaments. In practice all of this is usually not necessary depending on the sensitivity of your speakers. Usually a good power supply is all that is needed with a push pull amp and indirectly heated tubes.
Noise is another thing, it is nearly impossible to get the noise floor low enough to have a SNR in the 110db range, although mid 90's is possible, and generally good enough. My noise measurements are limited by the background noise from the computer which sets the measurement floor around -90db. I see no noise contribution when the amp is switched on. There is also 60, 120 and 180 Hz spikes from the computer that limit hum measurements to -75db. My TubelabSE (all DC filaments) does not raise the hum levels when switched on.
Noise is another thing, it is nearly impossible to get the noise floor low enough to have a SNR in the 110db range, although mid 90's is possible, and generally good enough. My noise measurements are limited by the background noise from the computer which sets the measurement floor around -90db. I see no noise contribution when the amp is switched on. There is also 60, 120 and 180 Hz spikes from the computer that limit hum measurements to -75db. My TubelabSE (all DC filaments) does not raise the hum levels when switched on.
"would a pp pair of 6L6 monoblocks sound good?"
Sure they would. However, keep in mind that 6L6s are more often used in guitar amps, which have quite different design criteria. A pair of 807 PP monoblocks would sound better.
"can a tube amp come close to that, and if properly designed , will there be any hum?"
You can certainly come quite close. What you need is a well filtered PS, and use DC on all the heaters (and make certain that you filter the heater supply very well as any residual AC is only going to make matters worse, not better.) and you can get rid of a lot of hum.
Sure they would. However, keep in mind that 6L6s are more often used in guitar amps, which have quite different design criteria. A pair of 807 PP monoblocks would sound better.
"can a tube amp come close to that, and if properly designed , will there be any hum?"
You can certainly come quite close. What you need is a well filtered PS, and use DC on all the heaters (and make certain that you filter the heater supply very well as any residual AC is only going to make matters worse, not better.) and you can get rid of a lot of hum.
Miles:
As I just pointed out in another thread the 807 was derived from the 6L6 and is a very similar tube. There were several tubes that were derived from the 6L6:
The 6BG6 was a 6L6 (i believe a 6L6GB) with a plate cap to increase the plate voltage rating so it could be used as a horizontal output tube.
The 807 was used in military applications as RF and audio amplifiers, it is a 6BG6 with a different base.
The 1625 is an 807 with a 12 volt filament and a different base to avoid accidental mix up. It was used in mobile applications.
If you find these tubes from the samp manufacturer and vintage, you will find that they sound similar.
The 6L6 today is primarilarly a guitar amp tube, but in its day it was the king of HiFi until the 6550, EL34, KT-88, 8417 and all of their step children came out.
As I just pointed out in another thread the 807 was derived from the 6L6 and is a very similar tube. There were several tubes that were derived from the 6L6:
The 6BG6 was a 6L6 (i believe a 6L6GB) with a plate cap to increase the plate voltage rating so it could be used as a horizontal output tube.
The 807 was used in military applications as RF and audio amplifiers, it is a 6BG6 with a different base.
The 1625 is an 807 with a 12 volt filament and a different base to avoid accidental mix up. It was used in mobile applications.
If you find these tubes from the samp manufacturer and vintage, you will find that they sound similar.
The 6L6 today is primarilarly a guitar amp tube, but in its day it was the king of HiFi until the 6550, EL34, KT-88, 8417 and all of their step children came out.
"As I just pointed out in another thread the 807 was derived from the 6L6 and is a very similar tube. There were several tubes that were derived from the 6L6".
This points out that there are some subtle differences. The 807 was designed primarily for efficiency, and thus uses lower screen voltages. Keeping the screen voltage down has the benefit of causing more electrons to head for the plate, so less power gets wasted in heating up the screen grid. It also has the additional benefit of enhancing linearity. To goose up the output power for consumer electronics, as a cost saving measure, tubes like the 6L6 use higher screen voltages. That gives a heavier plate current for any given Vpk, but also degrades linearity. The spec sheets verify this, in that the max Vsgsg for the 807 is less than half the max Vpp, whereas for the 6L6, it's more like 3/4ths.
If he's right, I would expect there to be some subtle differences, and that the 807 would sound better, especially if you go light on the NFB (which I intend to do).
This points out that there are some subtle differences. The 807 was designed primarily for efficiency, and thus uses lower screen voltages. Keeping the screen voltage down has the benefit of causing more electrons to head for the plate, so less power gets wasted in heating up the screen grid. It also has the additional benefit of enhancing linearity. To goose up the output power for consumer electronics, as a cost saving measure, tubes like the 6L6 use higher screen voltages. That gives a heavier plate current for any given Vpk, but also degrades linearity. The spec sheets verify this, in that the max Vsgsg for the 807 is less than half the max Vpp, whereas for the 6L6, it's more like 3/4ths.
If he's right, I would expect there to be some subtle differences, and that the 807 would sound better, especially if you go light on the NFB (which I intend to do).
I read this information, and have seen similar information in the past. This would imply that there were design differences between the individual variants of these tubes of similar construction. This was probably the case for tubes from the big suppliers before WWII. During the high production years of WWII, and the cost cutting era that followed, there were probably some compromises made that resulted in some vendors puting the same guts in all of these tubes.
I base my statements on my experience with my collection of about 100,000 tubes, about half of which is WWII era military surplus. These tubes were given to me (in exchange for a few days work). Unfortunately they were loose tubes (no individual boxes) that were all dumped randomly into large cardboard boxes. Many were broken. I have spent some time examining the insides of many of the broken ones. I had some interest in the 6L6 - 807 - 6BG6 - 1625 connection, so I checked some of these out. This was about a year ago, and I might have missed some details, but at the time I concluded that they were all the same. I am sure that I will find more broken 807's, so I will pay more attention to the screen grid wire spacing, and screen to cathode spacing. There may be an intended difference, that I missed, or there is a bigger variation between different vendors of 807's. There are several different vendors of 807's, many that I have never heard of.
This discussion has prompted me to re-visit this tube, especially since I have about 100 1625's and a good supply of 807's. I will have to check some out electrically, and see what happens. The data sheet says that a 1625 IS a 12 volt 807.
I base my statements on my experience with my collection of about 100,000 tubes, about half of which is WWII era military surplus. These tubes were given to me (in exchange for a few days work). Unfortunately they were loose tubes (no individual boxes) that were all dumped randomly into large cardboard boxes. Many were broken. I have spent some time examining the insides of many of the broken ones. I had some interest in the 6L6 - 807 - 6BG6 - 1625 connection, so I checked some of these out. This was about a year ago, and I might have missed some details, but at the time I concluded that they were all the same. I am sure that I will find more broken 807's, so I will pay more attention to the screen grid wire spacing, and screen to cathode spacing. There may be an intended difference, that I missed, or there is a bigger variation between different vendors of 807's. There are several different vendors of 807's, many that I have never heard of.
This discussion has prompted me to re-visit this tube, especially since I have about 100 1625's and a good supply of 807's. I will have to check some out electrically, and see what happens. The data sheet says that a 1625 IS a 12 volt 807.
6f6gt & El84
I built PP 6F6GT & they sounded good, but was triode connected. Me thinks the 6V6GT triode connected outplays the EL84 triode connected. EL84 is a good sounding tube, but only GE grey oval plate works for me. The GE embarrashed & handily outgunned Mullard EL84 with square getters.
I built PP 6F6GT & they sounded good, but was triode connected. Me thinks the 6V6GT triode connected outplays the EL84 triode connected. EL84 is a good sounding tube, but only GE grey oval plate works for me. The GE embarrashed & handily outgunned Mullard EL84 with square getters.
wow, the 6f6 in pp triode connected setup has considerably more power than a single tube in triode connection.
Single tube is .85 watts @ 6% THD
PP is 13 watts @ only 2%
how does the power go up so much when still in triode connection as pp?
with the pentode connection it only about doubles.
Single tube is .85 watts @ 6% THD
PP is 13 watts @ only 2%
how does the power go up so much when still in triode connection as pp?
with the pentode connection it only about doubles.
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