I like this 🙂
better 20a/30a for dht driver .....
send me mail I have nice pdf with lundhal at input 300b one tube
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hey Nico, thats great
with the greater output of a 300B-XLS, the losses could be made up by a strong preamp, and effective speakers
if a driver would be needed, that too would be possible later on, so I guess all in all a better choise
we should not forget which kind of speakers people have when using various designs
could be like night and day
110db horns using just 1watt, ofcouse 5watt from a single tube would work, and so on
well, I have learned a bit here
I reckon better to try a cheaper design first
I will look into minimal designs with flea power triodes, like ECC99
Dutchman DHT Rob has made a study he calls balance EL84(I know its not a triode)
His country man TriodeDick designed two PP amps with ECC99 in driver stage
Anastasia uses a single ecc99 input/driver, connected in what I think is LTP
Bill is a KT88 PP with ecc99 as a PP driver, I guess
I try to pick up bits and pieces here and there
And if lucky I may be able to put something together
cheers, and thanks
with the greater output of a 300B-XLS, the losses could be made up by a strong preamp, and effective speakers
if a driver would be needed, that too would be possible later on, so I guess all in all a better choise
we should not forget which kind of speakers people have when using various designs
could be like night and day
110db horns using just 1watt, ofcouse 5watt from a single tube would work, and so on
well, I have learned a bit here
I reckon better to try a cheaper design first
I will look into minimal designs with flea power triodes, like ECC99
Dutchman DHT Rob has made a study he calls balance EL84(I know its not a triode)
His country man TriodeDick designed two PP amps with ECC99 in driver stage
Anastasia uses a single ecc99 input/driver, connected in what I think is LTP
Bill is a KT88 PP with ecc99 as a PP driver, I guess
I try to pick up bits and pieces here and there
And if lucky I may be able to put something together
cheers, and thanks
Hey Tinitus
Hey Tinitus, one tube, one stage is very, very good….. but high quality iron is VERY expensive 🙁
This is other possibility, One tube + one mosfet, in a japanese web.
And the PS
And the web in japanese
ƒJƒXƒR�[ƒh’P’i‚XWƒVƒ“ƒOƒ‹ƒpƒ��[ƒAƒ“ƒv‚Ì�»�ì
regards Jaime
Hey Tinitus, one tube, one stage is very, very good….. but high quality iron is VERY expensive 🙁
This is other possibility, One tube + one mosfet, in a japanese web.
An externally hosted image should be here but it was not working when we last tested it.
And the PS
An externally hosted image should be here but it was not working when we last tested it.
And the web in japanese
ƒJƒXƒR�[ƒh’P’i‚XWƒVƒ“ƒOƒ‹ƒpƒ��[ƒAƒ“ƒv‚Ì�»�ì
regards Jaime
I have the eml300bxls with 6em7 as driver with 93db next driver will be 10Y I hopes...driver hard the 300b !
dht Rob is so nice 😉 vt52.com have some great low power amp.
is quite hard go up 93db with OB design...and $$$ but for me is the right way.
dht Rob is so nice 😉 vt52.com have some great low power amp.
is quite hard go up 93db with OB design...and $$$ but for me is the right way.
Hi Kevin,
Sorry to drag this old thread up. Would it be possible to drive a 300B with one of these 20B beasts??
-Raja
Sure, why not.. Mu is 20 which is a bit low for a single stage driver, so you might want another stage preceding it. (Maybe a 26 or some other low mu dht) Alternately a single 30A (mu of 32) might do it with choke loading if you don't mind a sensitivity of around 2Vrms for full output, and a much higher rp.. (Suitable for choke or CCS load, IT would not be a practical choice because of the high rp.)
2Vrms is right up my street. I might give the 30A a bash with choke loading then. Any ideas what kind of inductance I'd need for the plate choke??
Sorry to hound you 🙂
-Raja
Not a problem at all. I'd use either their output tubes or one of the KR 300B variants as this would obviously end up being a rather expensive amp to build. JJ also makes a pretty good 300B which is what I currently use in my own amps. A single triode connected D3A through the appropriate IT would probably do an excellent job at a much lower price point. (IT ratio of 1:1.5 would be interesting)
I'm running a choke loaded 6N1P~300B right now Kevin. It's just the curiosity of having a DHT driver that's niggling me at present. Currently using Electraprint plate chokes (I think they're the 100H ones).
-Raja
-Raja
hey, Kevin, since you brought up the D3a for my bass guitar amp, I was thinking about using IT too
but would be too costly for that particular project
but maybe good for another project
3kohm IT would be ok, yes ?
sounds like pretty much ideal for an IT
I recently had this amp build for me based on this tube using a step up transformer using the Lundahl LL7903 mic step up transformer. Ok, this was not a tried and tested proven formula but the idea intrigued me and I went ahead with it.
Anyone going for this build should not attempt so if using an input transformer for driver duties. Kevin was right that due to the Miller Capacitance of this tube, using so of this topology introduces nothing but severe distortion not to mention lack of any drive or decent volume to begin with. Not to mention introduction of more veiling to the sound. This is the first time I have had an implementation of an input transformer for any amp I had, maybe its the wrong tranny, what Kevin suggested of a 600:60k + 60k configuration that Sowter in UK offers but even then so can this even work in the first place?
He offered to help look at the circuit to correct it and while waiting and from ideas that he hinted here as well, I decided to put an active tube driver stage at the front and incorporated JEL's 76 DC 6SN7 CC driver stage in front of it to drive the grids of the EML 20B directly, not using any input tranny for any step up.
Remarkably this yielded a very decent sound with significant drive and one of the most airy and natural highs I have heard from many different DHT out there. The clipping distortion that I had earlier has disappeared completely with this implementation!
The tube is currently catahode biased but am expecting news from Kevin for further suggestions to make this better but he is right, using a tube stage in front of it is a much CORRECT method to drive this tube in particular.
Not a lot of bass from this tube not sure if its anything to do with the circuit topology I have adapted for it but am on the Hashimoto H20 14U OPT using the 14k primary impedance for this highish Rp tube, but am surprised how remarkable the high frequency response is on this configuration. But low bass response is not a trademark of this tube or this amp I have now, am currently using an REL 12 inch sub to fill in the lows, am seeing a severe lacking in anything below 80Hz.
Its funny how I had to profusely look at the whole thing and modify this to correct this in particular. Only thing good about this amp is that its remarkably quiet, perhaps the quietest I ever heard of any tube amps, absolutely no background noise, not even a hiss! Perhaps its because of the use of Rob Coleman's DHT heater modules that he configured for this project, using a CLC configuration before that using individual heater trannies may have something to do with it but else the voltage is to 2 decimal points stable when measured on my DMM.
Anyone going for this build should not attempt so if using an input transformer for driver duties. Kevin was right that due to the Miller Capacitance of this tube, using so of this topology introduces nothing but severe distortion not to mention lack of any drive or decent volume to begin with. Not to mention introduction of more veiling to the sound. This is the first time I have had an implementation of an input transformer for any amp I had, maybe its the wrong tranny, what Kevin suggested of a 600:60k + 60k configuration that Sowter in UK offers but even then so can this even work in the first place?
He offered to help look at the circuit to correct it and while waiting and from ideas that he hinted here as well, I decided to put an active tube driver stage at the front and incorporated JEL's 76 DC 6SN7 CC driver stage in front of it to drive the grids of the EML 20B directly, not using any input tranny for any step up.
Remarkably this yielded a very decent sound with significant drive and one of the most airy and natural highs I have heard from many different DHT out there. The clipping distortion that I had earlier has disappeared completely with this implementation!
The tube is currently catahode biased but am expecting news from Kevin for further suggestions to make this better but he is right, using a tube stage in front of it is a much CORRECT method to drive this tube in particular.
Not a lot of bass from this tube not sure if its anything to do with the circuit topology I have adapted for it but am on the Hashimoto H20 14U OPT using the 14k primary impedance for this highish Rp tube, but am surprised how remarkable the high frequency response is on this configuration. But low bass response is not a trademark of this tube or this amp I have now, am currently using an REL 12 inch sub to fill in the lows, am seeing a severe lacking in anything below 80Hz.
Its funny how I had to profusely look at the whole thing and modify this to correct this in particular. Only thing good about this amp is that its remarkably quiet, perhaps the quietest I ever heard of any tube amps, absolutely no background noise, not even a hiss! Perhaps its because of the use of Rob Coleman's DHT heater modules that he configured for this project, using a CLC configuration before that using individual heater trannies may have something to do with it but else the voltage is to 2 decimal points stable when measured on my DMM.
Mmmm . . . This must be the amp built for you?
Dixon Chen's 20B Stereo Amp, which is similar to this one?
Bob's EML 20B One Tube Single Ended Amp
some difference in the opinion of bass performance . . .
Dixon Chen's 20B Stereo Amp, which is similar to this one?
Bob's EML 20B One Tube Single Ended Amp
some difference in the opinion of bass performance . . .
This sort of circuit works well if you use the right tube to achieve the result. The E55L is an excellent candidate ( I have built one with an input choke using step up of 1:2). The choice of valve you have made seems far from ideal.
I also agree that an input choke will only work with a very meaty preamp - mine works with a 5687 in PP driving a step down transformer but it also works well with a SLCF preamp.
Basically, asking an input inductor to do your voltage gain is asking for trouble unless you have designed your whole system around the concept.
Shoog
I also agree that an input choke will only work with a very meaty preamp - mine works with a 5687 in PP driving a step down transformer but it also works well with a SLCF preamp.
Basically, asking an input inductor to do your voltage gain is asking for trouble unless you have designed your whole system around the concept.
Shoog
Shoog is correct.
You need a real high gm tube (I'm talking about 30mA/V and more) to get sufficent anode currents for speaker driving. Second, use a pentode ! I tried it with several paralled trioded PFL200 which resultet in an input capacity of about 2.3n thanks to miller effect. Sounds nasty. Next try is to use an input transformer, pentode mode and some pos+neg feedback to get the high output capacity down again. If everything fails, I will use triodes again and use a little sourcefollower direct coupled to the grid.
You need a real high gm tube (I'm talking about 30mA/V and more) to get sufficent anode currents for speaker driving. Second, use a pentode ! I tried it with several paralled trioded PFL200 which resultet in an input capacity of about 2.3n thanks to miller effect. Sounds nasty. Next try is to use an input transformer, pentode mode and some pos+neg feedback to get the high output capacity down again. If everything fails, I will use triodes again and use a little sourcefollower direct coupled to the grid.
Depends.
Grid-anode-capacity times amplification yields miller capacity per tube. This capacity tells you the 3db rolloff.
If you use a transformer in front of that you can get ringing etc.
Try it out, send a square wave through it and see how it behaves.
But the biggest problem is oscillation due to the gigantic gm you get. With values over 100mA/V you have to use ferrites and little unbypassed cathode resistors. Just a one inch wire on the grid and you built a powerful >100Mhz oscillator.
Grid-anode-capacity times amplification yields miller capacity per tube. This capacity tells you the 3db rolloff.
If you use a transformer in front of that you can get ringing etc.
Try it out, send a square wave through it and see how it behaves.
But the biggest problem is oscillation due to the gigantic gm you get. With values over 100mA/V you have to use ferrites and little unbypassed cathode resistors. Just a one inch wire on the grid and you built a powerful >100Mhz oscillator.
I had very good results with ferrites on all leads to my E55L project, not a sign of oscillation and I never used a single grid stopper resistor. I placed ferrites (single turn) on the g1, g2, g3 to cathode, and anode. I was a little surprised that it worked so well.
Shoog
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