Adding loudness compensation to tube preamp
- By emartine
- Tubes / Valves
- 6 Replies
Hello there. I am trying to add a compensation circuit very similar to the one explained here to a tube preamplifier based on a simple E88CC common cathode stage + cathode follower.
I am adding the compensation circuit between the balance and volume control. The thing is that I have high frequency attenuation.
Please see attachments.
If if bypass the balance control, the frequency response looks as it should in the LTspice simulation.
I believe this is an impedance mismatch problem but I cannot move the circuit after the cathode follower cause it works together with the volume control which is at the input.
NOTES: I dont want to move the volume after the cathode follower and also don't want to add another potentiometer for the compensation.
I also cannot use a four gang volume potentiometer.
I tried changing the balance pot value to a lower 10k, which seems to cure the problem but input impedance drops way too much to load sources properly.
Any ideas? THANK YOU!
I am adding the compensation circuit between the balance and volume control. The thing is that I have high frequency attenuation.
Please see attachments.
If if bypass the balance control, the frequency response looks as it should in the LTspice simulation.
I believe this is an impedance mismatch problem but I cannot move the circuit after the cathode follower cause it works together with the volume control which is at the input.
NOTES: I dont want to move the volume after the cathode follower and also don't want to add another potentiometer for the compensation.
I also cannot use a four gang volume potentiometer.
I tried changing the balance pot value to a lower 10k, which seems to cure the problem but input impedance drops way too much to load sources properly.
Any ideas? THANK YOU!
Air Coil Inductor replacing iron coil type
- By Tubenstein
- Multi-Way
- 19 Replies
I found a company in China is able to custom made air coil inductor with vary DCR. I want to use this air coil type to replace the iron coil in the crossover. Any comments?
Panasonic UB450 - discussions, upgrades
- By Coris
- Digital Source
- 10 Replies
In the last time I had the opportunity to examine and upgrade a Panasonic UB450. When one look at this device and know its price in shop, then one`s first thought hearing about upgrading it, is: what to upgrade to this cheap device?
Indeed, this device is a very cheap media player, meant to playback discs, streaming over the network, as playback for media files through the device USB port. The optical device is a cheap whole plastic item. Working well, but a little bit noisy. The chassis is made of a less 1mm thickness steel plate, with a cheap, whole plastic front panel. The whole device it consists of a small low-profile box.
Inside we find a small one main board, with all of necessary chips on it. A glued heatsink partially placed over the main processor as over the memory chips in central area of the board. No any analogue section for audio. Also, much unnecessary these days an such dedicated analogue audio section, when one is largely using video processors to get analogue audio quality out, or other similar solutions. A local analogue audio section it has its own advantages when about outputted quality sound, but in this case for cost effectiveness reasons, it was decided not to be implemented.
The power supply of the player is an external one, a small compact SMPS type, to be connected directly to the outlet.
Well, this cheap device, and out of the box, is indeed capable of a very good picture quality. It was my first surprise in using it. I own and use myself an UB9000. Comparing UB450 with UB9000 was very easy, and UB9000 is indeed surpassed by this new and cheap UB450. Not only similar picture quality out of the stock UB450, compared with an upgraded UB9000, but a much better user interface as well for UB450. Very fast Menu navigation. Much user-friendly interface. No hanging or freezing, as very annoying it happen in case of UB9000. Very fast loading and ready to playback for files residing on a USB stick. Lot of GB getting ready for use in around a second, while one should wait many teens of seconds for the same to happen on an UB9000. I have noted especially about the HDR functionality on this UB450. It really makes a difference, is very obvious and improving a lot the picture quality. One realises indeed what mean HDR improvement when using this UB450 device.
Initially I was myself sceptical about the results of an upgrade for a such cheap item. And what to upgrade more, for a such picture quality out of a stock UB450?
Then I proceeded to a close examination of the electronic design, firstly targeting to adapt the power supply approach for the use of an LPS. Mainly, it was about replacing the DC 12v main rail, provided by the original small SMPS box, with a linear analogue 12vDC solution. Not difficult task also.
Proceeding accordingly, and after using an improvised LPS circuit (see picture), I had another pleasant surprise. The use of a linear power supply it confirmed once more that it can improve a lot even an original high video quality. However, one cannot realise this difference, but only after an LPS it is providing power instead of an SMPS to the targeted digital circuitry or device. The difference is there, is obvious, and is pleasant. All pictures’ parameters are improved: brightness, contrast, colour, tonal range, finer details, noises level. Everything it get in fact better.
Then I decided that this upgrade is really worthy and it need an more professional approach. So, I designed an LPS which it will fit into the available place inside the small enclosure. I was initially appreciating that the heat generating by a such lower power LPS for this device, it may not represent an issue. Thinking it will be enough to dissipate the eventual heat through the metal parts around, bottom of the chassis and the tiny steel plate cover, with a passive ventilation. Well, I was enough wrong about the heat. Even low amount heat, the heatsink it could not be that big, and the dissipation effectiveness it was not good through the chassis bottom, and the cover. I improved the thermal contact, but not enough either. The inside temperature was rising against 60°C with passive ventilation. In the end I realised that the best ventilation solution is using a fan to force the air out of the small enclosure. The enclosure it was originally provided with ventilation holes, which it could be used for this forced ventilation approach. Choosing the right silent fan, powering it from an added dedicated regulator on LPS board. A large hole (fan dimension/diameter) should be carved into the bottom of the chassis, for the fan to effectively exhaust the hot air from inside, while fresh air coming through the original ventilation holes. This solution it was effective indeed, and the inside temperature went down to 45°. Reasonable result, and nothing it affected the original shape and visual aspect of the player. The fan is running fully silent, mounted on a good dumping material. I have also mounted new and higher dumping feet for the chassis.
I have placed on the LPS board also circuits for the two oscillators (upgrade) for the main processor and the video processor chip. The original clocking approach is using resonators connected to the inbuild clock generators inside the main processor and video chip. Classical cheap clocking design solution.
Well, this LPS placed inside the device enclosure it should be powered by a transformer which very obviously it has no place inside such small enclosure. An external nice and professional enclosure solution had to be adopted. HF and DC blocking filtering cells are also added to this external power solution.
For such a cheap tiny device, a such expensive LPS solution! Well, in the end I appreciated as worthy. The improvement gain in quality for picture and digital sound is remarkably high. In the end, the whole upgrade cost it exceeds by far the device selling price… However, as overall costs (device + upgrades) it still yet be lower than upgrading another type of player, as UB9000 or whatever. And the quality out of UB450, it exceeds what is possible being obtaining from a more expensive device (upgraded).
The overall conclusion: everything it worth for the final results.
Indeed, this device is a very cheap media player, meant to playback discs, streaming over the network, as playback for media files through the device USB port. The optical device is a cheap whole plastic item. Working well, but a little bit noisy. The chassis is made of a less 1mm thickness steel plate, with a cheap, whole plastic front panel. The whole device it consists of a small low-profile box.
Inside we find a small one main board, with all of necessary chips on it. A glued heatsink partially placed over the main processor as over the memory chips in central area of the board. No any analogue section for audio. Also, much unnecessary these days an such dedicated analogue audio section, when one is largely using video processors to get analogue audio quality out, or other similar solutions. A local analogue audio section it has its own advantages when about outputted quality sound, but in this case for cost effectiveness reasons, it was decided not to be implemented.
The power supply of the player is an external one, a small compact SMPS type, to be connected directly to the outlet.
Well, this cheap device, and out of the box, is indeed capable of a very good picture quality. It was my first surprise in using it. I own and use myself an UB9000. Comparing UB450 with UB9000 was very easy, and UB9000 is indeed surpassed by this new and cheap UB450. Not only similar picture quality out of the stock UB450, compared with an upgraded UB9000, but a much better user interface as well for UB450. Very fast Menu navigation. Much user-friendly interface. No hanging or freezing, as very annoying it happen in case of UB9000. Very fast loading and ready to playback for files residing on a USB stick. Lot of GB getting ready for use in around a second, while one should wait many teens of seconds for the same to happen on an UB9000. I have noted especially about the HDR functionality on this UB450. It really makes a difference, is very obvious and improving a lot the picture quality. One realises indeed what mean HDR improvement when using this UB450 device.
Initially I was myself sceptical about the results of an upgrade for a such cheap item. And what to upgrade more, for a such picture quality out of a stock UB450?
Then I proceeded to a close examination of the electronic design, firstly targeting to adapt the power supply approach for the use of an LPS. Mainly, it was about replacing the DC 12v main rail, provided by the original small SMPS box, with a linear analogue 12vDC solution. Not difficult task also.
Proceeding accordingly, and after using an improvised LPS circuit (see picture), I had another pleasant surprise. The use of a linear power supply it confirmed once more that it can improve a lot even an original high video quality. However, one cannot realise this difference, but only after an LPS it is providing power instead of an SMPS to the targeted digital circuitry or device. The difference is there, is obvious, and is pleasant. All pictures’ parameters are improved: brightness, contrast, colour, tonal range, finer details, noises level. Everything it get in fact better.
Then I decided that this upgrade is really worthy and it need an more professional approach. So, I designed an LPS which it will fit into the available place inside the small enclosure. I was initially appreciating that the heat generating by a such lower power LPS for this device, it may not represent an issue. Thinking it will be enough to dissipate the eventual heat through the metal parts around, bottom of the chassis and the tiny steel plate cover, with a passive ventilation. Well, I was enough wrong about the heat. Even low amount heat, the heatsink it could not be that big, and the dissipation effectiveness it was not good through the chassis bottom, and the cover. I improved the thermal contact, but not enough either. The inside temperature was rising against 60°C with passive ventilation. In the end I realised that the best ventilation solution is using a fan to force the air out of the small enclosure. The enclosure it was originally provided with ventilation holes, which it could be used for this forced ventilation approach. Choosing the right silent fan, powering it from an added dedicated regulator on LPS board. A large hole (fan dimension/diameter) should be carved into the bottom of the chassis, for the fan to effectively exhaust the hot air from inside, while fresh air coming through the original ventilation holes. This solution it was effective indeed, and the inside temperature went down to 45°. Reasonable result, and nothing it affected the original shape and visual aspect of the player. The fan is running fully silent, mounted on a good dumping material. I have also mounted new and higher dumping feet for the chassis.
I have placed on the LPS board also circuits for the two oscillators (upgrade) for the main processor and the video processor chip. The original clocking approach is using resonators connected to the inbuild clock generators inside the main processor and video chip. Classical cheap clocking design solution.
Well, this LPS placed inside the device enclosure it should be powered by a transformer which very obviously it has no place inside such small enclosure. An external nice and professional enclosure solution had to be adopted. HF and DC blocking filtering cells are also added to this external power solution.
For such a cheap tiny device, a such expensive LPS solution! Well, in the end I appreciated as worthy. The improvement gain in quality for picture and digital sound is remarkably high. In the end, the whole upgrade cost it exceeds by far the device selling price… However, as overall costs (device + upgrades) it still yet be lower than upgrading another type of player, as UB9000 or whatever. And the quality out of UB450, it exceeds what is possible being obtaining from a more expensive device (upgraded).
The overall conclusion: everything it worth for the final results.
The equivalent circuit of a pot with center tap
- By presscot
- Solid State
- 3 Replies
I'm seriously curious about the equivalent circuit of a potentiometer with center tap which is usually used to be a volume with loudness function. It contains 4 terminals where the 4th terminal is the center tap connection. However, most simulation software don't have the 4-terminal symbol as attached. So, I wonder whether we could draw the equivalent circuit by a regular potentiometer (only have 3 terminals) with additional resistor(s). Please advice
Opamp LF356, can I upgrade my preamp?
- By TheFinisher
- Chip Amps
- 42 Replies
Hi,
I have a Burmester 785 preamp that uses the lf356 op amp , as nobody seems interested in buying it I thought I’ll keep it and if possible upgrade the op amps but is that possible? I mean is there an improved newer op amp that I can simply install then use without having to make other modifications.
I have a Burmester 785 preamp that uses the lf356 op amp , as nobody seems interested in buying it I thought I’ll keep it and if possible upgrade the op amps but is that possible? I mean is there an improved newer op amp that I can simply install then use without having to make other modifications.
LJM L7 mosFET power supply
- By ffdisk11
- Power Supplies
- 0 Replies
Greeting from south korea
I recently bought an LJM L7 mosfet amplifier from Taobao
Is this adapter appropriate for this amplifier?
DC36V 1.5A
If not, please recommend an adapter.
I recently bought an LJM L7 mosfet amplifier from Taobao
Is this adapter appropriate for this amplifier?
DC36V 1.5A
If not, please recommend an adapter.
Discrepancy in Augspurger paper on Loudspeaker on Damped Pipes?
- By jlinkels
- Full Range
- 6 Replies
This is a question really for someone who has thoroughly gone thru this paper. It is a very detailed question. Not something which would invalidate any conclusion. I think it is an error. Strangely enough, Augspurger has published an update for this paper. But in this update he has copied the tables and figures verbatim.
My question is just out of interest, my speaker design does not depend on it, and perhaps no one would care.
The problem is in this table:
And this is fig 8a:
Augspurger uses a driver with Fs = 50 Hz for this.
According to the table Fs/Fp = 0.5 => Fp=Fs/0.5 = 100 Hz
F3/Fp=1 so F3 should be 100 Hz.
This is also what the table says, and completely in accordance.
But now for Fig 8b he changes the tuning of the pipe, and the resulting response should
be according to this figure:
Table: Fs/Fp = 0.33 => Fp = Fs/0.33 => Fp = 150 Hz
F3/Fp = 0.6 => F3 = Fp * 0.6 = 90 Hz
This is completely off.
It would be strange anyway, when the Fp is increased, F3 would decrease.
From the figure, it looks more like F3 = 60 Hz
I have modeled the first case in Hornresp, using Fs and Qts from the table, using
average values for a 4" driver for the unkown values. I know this is very vague but I did not
have any other information.
The outcome of Hornresp was totally comparable, differing only in some magnitudes of
peaks and minima. All frequencies and curve shape were spot on.
Then, when doing the same for Fig 8b from the table, the Hornresp result did not even
resemble anything. Until I changed Fs/Fp to 0.66 instead of Fs/Fp and then the curves
matched almost.
So, is this an error in this paper? Given the counter-intuitive increase of Fp resulting in
a decrease of F3. And in Table 1 of the same paper the author also decreases Fp for a
decrasing Fs.
But then again, this was a published and peer-reviewed article and has been cited for 24 years.
jlinkels
My question is just out of interest, my speaker design does not depend on it, and perhaps no one would care.
The problem is in this table:
And this is fig 8a:
Augspurger uses a driver with Fs = 50 Hz for this.
According to the table Fs/Fp = 0.5 => Fp=Fs/0.5 = 100 Hz
F3/Fp=1 so F3 should be 100 Hz.
This is also what the table says, and completely in accordance.
But now for Fig 8b he changes the tuning of the pipe, and the resulting response should
be according to this figure:
Table: Fs/Fp = 0.33 => Fp = Fs/0.33 => Fp = 150 Hz
F3/Fp = 0.6 => F3 = Fp * 0.6 = 90 Hz
This is completely off.
It would be strange anyway, when the Fp is increased, F3 would decrease.
From the figure, it looks more like F3 = 60 Hz
I have modeled the first case in Hornresp, using Fs and Qts from the table, using
average values for a 4" driver for the unkown values. I know this is very vague but I did not
have any other information.
The outcome of Hornresp was totally comparable, differing only in some magnitudes of
peaks and minima. All frequencies and curve shape were spot on.
Then, when doing the same for Fig 8b from the table, the Hornresp result did not even
resemble anything. Until I changed Fs/Fp to 0.66 instead of Fs/Fp and then the curves
matched almost.
So, is this an error in this paper? Given the counter-intuitive increase of Fp resulting in
a decrease of F3. And in Table 1 of the same paper the author also decreases Fp for a
decrasing Fs.
But then again, this was a published and peer-reviewed article and has been cited for 24 years.
jlinkels
Attachments
Introduction
- By abrombo
- Introductions
- 2 Replies
I have been making speakers since the 70's (I'm an old fart of 77). My current speaker systems are a CBT36K for my home theater and a LX521.4 for my personal listening. In my early days I've made many Heathkits also Dynaco Mark III, PAT 5, and a Luxman kit tube integrated amplifier. I now proselytize for active crossovers (I am using miniDSP Flex 8 in both systems). I preach the gospel of Linkwitz and Keele (obvious from my choice of speakers).
Hello, from Denmark
- By Rene jensen
- Introductions
- 3 Replies
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For Sale 4 way Crossover designed by Erno Boberly
Attachments
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Erno Xover Speaker Builder (2).jpg -
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Erno Xover Speaker Builder (5).jpg -
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Erno Xover Speaker Builder (8).jpg -
Erno Xover Speaker Builder (9).jpg -
Erno Xover Speaker Builder (10).jpg -
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Erno Xover Speaker Builder (12).jpg -
Erno Xover Speaker Builder (13).jpg -
Erno Xover Speaker Builder (14).jpg -
Erno Xover Speaker Builder (15).jpg -
Erno Xover Speaker Builder (16).jpg -
Erno Xover Speaker Builder (17).jpg -
Erno Xover Speaker Builder (18).jpg -
Erno Xover Speaker Builder (19).jpg -
Erno Xover Speaker Builder (20).jpg
For Sale Circuit basics lm3886 power amplifier. Working, one channel 6db down
- By gilbodavid
- Swap Meet
- 1 Replies
Nicely made amplifier. I don't know why one channel is quieter than the other. It may be just a wrong resister.
I bought this off a fellow diyauduo person who built it.
£75 Ono
I bought this off a fellow diyauduo person who built it.
£75 Ono
Looking for SEAS midrange driver
Hi
Last weekend I noticed issues with two midrange drivers on my Visonik concept 7 speakers.
There are four of them and two of them, both the upper driver of left/right channel makes a scraping noise (sometimes, under specific conditions). I think the voice coil might be deformed.
I think these are SEAS Excel drivers, but I don't find sufficient information on replacements or where to buy them.
Is anyone here able to help me identifiy these?
Greetings!
Last weekend I noticed issues with two midrange drivers on my Visonik concept 7 speakers.
There are four of them and two of them, both the upper driver of left/right channel makes a scraping noise (sometimes, under specific conditions). I think the voice coil might be deformed.
I think these are SEAS Excel drivers, but I don't find sufficient information on replacements or where to buy them.
Is anyone here able to help me identifiy these?
Greetings!
EL34 UL/Triode Switch
- By Ajay L
- Tubes / Valves
- 12 Replies
I've recently completed my first valve amp build and now would like to add an UL/Triode switch. Kindly take a look at my attached drawing and also the original schematic and tell me if the way I drew it is correct.
