Filenet,
The problem might be as 45 said . . . capacitance.
The wave shape reminds me of "dribble-up"
I looked at the LL1620 data sheet, set up for 11k 60mA primary:
The series primary connection is obvious:
B+ on Pin 8
Pin 2 - pin 5
Pin 7 - pin 3
Pin 1 - pin 6
Plate on pin 4
What is not obvious is which secondary connection chart are you using?
B?
Or C?
Thanks!
There is no Class B, ther is no Class AB, for a single ended output tube and output transformer.
A single ended 845 is either A1, or A2 (unless you enjoy to listening to hard clipping as a result of the 845 going into complete cut off).
The difference between without global negative feedback, and with global negative feedback is primarily:
Distortion
Damping Factor
Input to Output Gain
Wave-shape, ringing, etc.
You Should listen to the amplifier With, and Without, global negative feedback.
45 said things change w/ and w/o negative feedback . . . of course they do!
Changing from a non-inductive resistor to a Loudspeaker load makes lots of difference, from 20-20kHz, there are frequencies that are purely resistive load, inductive load, capacitive load; and at some frequencies load combinations of varying amounts of L, C, and R.
Eliptical Loads abound.
Have fun listening!
The problem might be as 45 said . . . capacitance.
The wave shape reminds me of "dribble-up"
I looked at the LL1620 data sheet, set up for 11k 60mA primary:
The series primary connection is obvious:
B+ on Pin 8
Pin 2 - pin 5
Pin 7 - pin 3
Pin 1 - pin 6
Plate on pin 4
What is not obvious is which secondary connection chart are you using?
B?
Or C?
Thanks!
There is no Class B, ther is no Class AB, for a single ended output tube and output transformer.
A single ended 845 is either A1, or A2 (unless you enjoy to listening to hard clipping as a result of the 845 going into complete cut off).
The difference between without global negative feedback, and with global negative feedback is primarily:
Distortion
Damping Factor
Input to Output Gain
Wave-shape, ringing, etc.
You Should listen to the amplifier With, and Without, global negative feedback.
45 said things change w/ and w/o negative feedback . . . of course they do!
Changing from a non-inductive resistor to a Loudspeaker load makes lots of difference, from 20-20kHz, there are frequencies that are purely resistive load, inductive load, capacitive load; and at some frequencies load combinations of varying amounts of L, C, and R.
Eliptical Loads abound.
Have fun listening!
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It is B (380VRMS divided by turns ratio (~38:1) = 10VRMS.
Obviously not class A2 which is for max output power and that is not the case here.
It is a weakish operated output tube (less than half of max dissipation) which is loaded with a marginal (13 watt) output transformer hoping for the best.
Obviously not class A2 which is for max output power and that is not the case here.
It is a weakish operated output tube (less than half of max dissipation) which is loaded with a marginal (13 watt) output transformer hoping for the best.
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Out of interest: why did you choose the 845 for output? With the operating points (800V and -125V bias) the dissipation is actually around 35-40 watts, not so much more than a 300B.
With your power supply you already have 400V.
When replacing 845 with 300B and changing the output transformer in 3k3 mode (possible?) you have a very slightly less powerful but more efficient (filament) amplifier.
With your power supply you already have 400V.
When replacing 845 with 300B and changing the output transformer in 3k3 mode (possible?) you have a very slightly less powerful but more efficient (filament) amplifier.
daanve,
I can not answer for filenet, but why not build 845 amplifiers, either that way, or modified somewhat for different performance.
If nothing else, an 845 is:
A very linear DHT
Has beautiful glass, and a very bright beautiful thoriated filament
Has both Steel Plate, and Carbon Plate versions.
Is a design that is something out of the long ago past.
Other than that, you tell me the reason.
Yes, I kind of wish I had a pair of SE 845 Mono-Blocks.
My main problems with 845 tubes are,
I would use 10VDC at 3.25A (no AC DHT filaments) . . .
And . . . The possibility of developing another Hernia.
I already have designed and built both 300B SE and PP amplifiers.
I may build 300B Se amplifiers again, I still have a pair of JJ 300B tubes.
I can not answer for filenet, but why not build 845 amplifiers, either that way, or modified somewhat for different performance.
If nothing else, an 845 is:
A very linear DHT
Has beautiful glass, and a very bright beautiful thoriated filament
Has both Steel Plate, and Carbon Plate versions.
Is a design that is something out of the long ago past.
Other than that, you tell me the reason.
Yes, I kind of wish I had a pair of SE 845 Mono-Blocks.
My main problems with 845 tubes are,
I would use 10VDC at 3.25A (no AC DHT filaments) . . .
And . . . The possibility of developing another Hernia.
I already have designed and built both 300B SE and PP amplifiers.
I may build 300B Se amplifiers again, I still have a pair of JJ 300B tubes.
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I had a pair of 845 bought 10 years ago, and reading Igor Popovich books, lighted my fire.
300B is an easy tube compared to 845.
300B is an easy tube compared to 845.
The 30 Hz reference is more technical/theorical than practical. It's just an initial paramenter to set the specs for the OPT but it doesn;t need to be strict. Certainly, I would not lose my sleep if max undistorted Pout is achieved down to 35Hz instead of 30Hz. Those clean 9.68 Vrms @30Hz already become 11.3V rms @35Hz and that means 16W clean power from such frequency up. With 11.5K primary load and about 800V/60mA I think 15-16W is quite optimal situation with 845. The amplifier as a whole only needs to be tuned and refined for this. Instead of messing with other power tubes and transformers I would invest time and resources to maximize the PSU and driver performance.
To get 15-16W out of 300B's one can only use very expensive variants it or go for PSE (to get even bit more power) but economically the 845 might (very likely) become convenient!
To get 15-16W out of 300B's one can only use very expensive variants it or go for PSE (to get even bit more power) but economically the 845 might (very likely) become convenient!
Yes, 13W at 30Hz. In reality 9.68V means 12W. But that figure becomes about 16W at 35Hz already. At 50Hz it's almost 33W! AC induction is less and less as you go up in frequency while the transformer (AC induction) headroom doesn't change.
Many ouput transformers are specified 30-40-50W but unfortunately more often there is no low frequency limit and that usually means the reference frequency is line frequency of 50-60Hz! It makes them equivalent or not much better than the Lundahl....
Lundhals are quite good at low frequency, including distortion figures. It has always been one of their strenghts.
Many ouput transformers are specified 30-40-50W but unfortunately more often there is no low frequency limit and that usually means the reference frequency is line frequency of 50-60Hz! It makes them equivalent or not much better than the Lundahl....
Lundhals are quite good at low frequency, including distortion figures. It has always been one of their strenghts.
We are talking about 2.5kg weight output transformer.
There are other opinions:
http://www.audiodesignguide.com/Claudio845/test_ver1.html
"On the first two plot we can see that the distortion level change with the frequency so probably the 9.5Vrms are a little too much for this transformer (Pout=9.5*9.5/8=11.3W)."
IMO these transformers good for low/er/ impedance tubes (for example 300B, up to 10W), at 3k3-6k range (lower primary turns), 60-80mA primary current, but 11k5/60mA (and the 120mApp swing) is problematic for it's core at LF.
But it's my opinion....
There are other opinions:
http://www.audiodesignguide.com/Claudio845/test_ver1.html
"On the first two plot we can see that the distortion level change with the frequency so probably the 9.5Vrms are a little too much for this transformer (Pout=9.5*9.5/8=11.3W)."
IMO these transformers good for low/er/ impedance tubes (for example 300B, up to 10W), at 3k3-6k range (lower primary turns), 60-80mA primary current, but 11k5/60mA (and the 120mApp swing) is problematic for it's core at LF.
But it's my opinion....
With -125V fixed bias, output power will be 10 watt at most (driver stage is not able to drive the 845 grid into A2), so what the output transformer is capable of at higher frequencies is not so relevant.
Filenet has initially been generous with measurements, but I still would like to see a 30 Hz waveform at 30 Hz/9,...VRMS. Cannot be so difficult?
Asking this because I had a Lundahl OPT in the past which did not meet the inductance specification.
Filenet has initially been generous with measurements, but I still would like to see a 30 Hz waveform at 30 Hz/9,...VRMS. Cannot be so difficult?
Asking this because I had a Lundahl OPT in the past which did not meet the inductance specification.
Yes, it just 2.5Kg but Lundahl have their own quality cores that can work without noticeable distortion up to 1.6T. Think of them more like toroidals in this respect. Do that with standard GOSS C-cores or, even worse, EI M6 laminations and you need to double up the weight of the core to get the same distortion figures at low frequency.
16W @35Hz is good enough for medium power 845/211 amp. I challenge anyone to tell me the difference between 16W @30Hz and 16W@ 35Hz. That's approx. the max A1 power you will get with 800V and 11.5K. Even less with 211.....
Below 40Hz, in the great majority of recordings the musical content drops very fast. I consider myself 30Hz the best compromise and 20Hz a total waste. 30Hz is a nominal target, if it doesn't meet it for few Hz it doesn't mean that it won't work and more importantly it doesn't mean lower practical/musical performance. The Lundahl LL1620 in the 11.5K configuration is more efficient and might bring better result than going for higher loss.
The 16W 845 amplifier at 10W will have a lot less distortion than 10W 300B. The latter could get close if you push the 300B harder while the 845, at 48W plate dissipation will last forever.
In my opinion the 300B PSE makes sense when I want 20-25W. For 15-16W I still prefer the 845 or even more the 211, despite the high plate voltage. With all the available high quality DC-link capacitors at affordable price the 211, especially, can also be economically more convenient.
filenet,
I agree.
you said: "300B is an easy tube compared to 845".
I thought I made that very obvious in my Post that immediately proceeded your post.
De Ja Vu all over again.
I agree.
you said: "300B is an easy tube compared to 845".
I thought I made that very obvious in my Post that immediately proceeded your post.
De Ja Vu all over again.
45,
I build mono-block amplifiers, not stereo amplifiers.
I do not mind the extra weight of EI laminations for both SE and PP, versus Lundahl transformers.
As long as the mono-block weight meets my recommendations for non-Hernia weight.
I did try different models of SE and PP Lundahl Interstage transformers.
I found that in order to get the high frequency square wave response I wanted, I had to load them down with either R or RC networks.
That puts a greater load on the tubes that drive them.
I no longer use Lundahl Interstage transformers; I lost patience; my personal preference. Others have been very successful with them, good.
If I get the time and inclinations, I would like to try a Lundahl PP output transformer; specifically designed for PP, not a want-to-be dual-purpose PP / SE output transformer.
I can just borrow one of my friend's extra Lundahl PP outputs, long enough to know if I want to order a pair for myself.
I hope it works easily and nicely for me.
Someday . . .
I build mono-block amplifiers, not stereo amplifiers.
I do not mind the extra weight of EI laminations for both SE and PP, versus Lundahl transformers.
As long as the mono-block weight meets my recommendations for non-Hernia weight.
I did try different models of SE and PP Lundahl Interstage transformers.
I found that in order to get the high frequency square wave response I wanted, I had to load them down with either R or RC networks.
That puts a greater load on the tubes that drive them.
I no longer use Lundahl Interstage transformers; I lost patience; my personal preference. Others have been very successful with them, good.
If I get the time and inclinations, I would like to try a Lundahl PP output transformer; specifically designed for PP, not a want-to-be dual-purpose PP / SE output transformer.
I can just borrow one of my friend's extra Lundahl PP outputs, long enough to know if I want to order a pair for myself.
I hope it works easily and nicely for me.
Someday . . .
@filenet : Very clean construction and elaborate schematic, congrats! Though, in order to keep the "vintage feeling" up to the end an interstage transformer will be more appropriate, it will also help with frequency response and help squeeze some more power with ease, AD1 has lower enough internal resistance for this operating mode.