5 Peaces of 6C41
These have been standing and glairing at me for at least 10 year now,so theya are NOS.
All 5 for 20 euro with 2 holders.
All 5 for 20 euro with 2 holders.
Attachments
6SN7 + 6SL7 suggested combination for Willsenton R8
- By raelman
- Tubes / Valves
- 10 Replies
Hello.
I have bought a Willsenton R8 amplifier.
I will use Genalex Gold Lion KT88 reissue power tubes and I'd like to know what kind of 6SN7 (x3) + 6SL7 (x2) shuold you reccomend me not expending more money in tubes than in the amp itself.
I have RCA 6SN7GTB that I could use... what 6SL7 for those?
Attached you will find schematic if it helps
thank you.
I have bought a Willsenton R8 amplifier.
I will use Genalex Gold Lion KT88 reissue power tubes and I'd like to know what kind of 6SN7 (x3) + 6SL7 (x2) shuold you reccomend me not expending more money in tubes than in the amp itself.
I have RCA 6SN7GTB that I could use... what 6SL7 for those?
Attached you will find schematic if it helps
thank you.
Measurements from MTM with tweeter waveguide
Here are a couple sets of measurements I obtained using SoundQueasy to measure the response of my latest speaker project. It's really an extensive overhaul of a previous design, using the same drivers but modifying the cabinets and adding an MCM waveguide to the tweeter. The drivers are oldies but goodies: ScanSpeak d2900-9300 textile tweeter, and two Vifa 5.5" P13WH-00-08 woofers. These are the same drivers Olson used in his original Ariel speaker design some of you may remember. For historical reasons my two woofers are rather widely spaced (sorry, I have no photo with me as I write this). Given the recent interest in waveguide-terminated tweeters I thought the measurements might be of interest to someone anyway.
The top set shows the total SPL, the woofers with their crossover in place, and the tweeter with its crossover in place. The slight downward tilt in the response was done on purpose because I didn't want an overly bright response. These graphs do not include any nearfield woofer measurements to extend the results to lower frequencies, so ignore the low frequency rolloff. (In case the scales are hard to read: there are 5 dB between neighboring pairs of horizontal grid lines.)
The lower set of measurements is from on axis (0 degrees) and then increasingly off axis in 15 degree increments (15, 30, and 45 degrees). All measurements were taken at about 1 meter, and at the height of the tweeter.
The glitch in the high frequency response around 10 KHz is a bit smaller in the other speaker, but otherwise the responses of the two speakers are nearly identical. Comparing waveguides I think I might have made one waveguide VERY slightly deeper than the other. I've verified by adding pieces of tape to the waveguide that little tiny changes in the tweeter's immediate environment induce significant changes in that 10 KHz range.
In spite of the glitch I was pleased by the controlled off-axis rolloff since that was one of my main design goals. Now I'll just have to learn how to make better use of SE's crossover optimization tools. I came up with these crossovers the old fashioned way: tweak-measure-tweak-measure...
Few
The top set shows the total SPL, the woofers with their crossover in place, and the tweeter with its crossover in place. The slight downward tilt in the response was done on purpose because I didn't want an overly bright response. These graphs do not include any nearfield woofer measurements to extend the results to lower frequencies, so ignore the low frequency rolloff. (In case the scales are hard to read: there are 5 dB between neighboring pairs of horizontal grid lines.)
The lower set of measurements is from on axis (0 degrees) and then increasingly off axis in 15 degree increments (15, 30, and 45 degrees). All measurements were taken at about 1 meter, and at the height of the tweeter.
The glitch in the high frequency response around 10 KHz is a bit smaller in the other speaker, but otherwise the responses of the two speakers are nearly identical. Comparing waveguides I think I might have made one waveguide VERY slightly deeper than the other. I've verified by adding pieces of tape to the waveguide that little tiny changes in the tweeter's immediate environment induce significant changes in that 10 KHz range.
In spite of the glitch I was pleased by the controlled off-axis rolloff since that was one of my main design goals. Now I'll just have to learn how to make better use of SE's crossover optimization tools. I came up with these crossovers the old fashioned way: tweak-measure-tweak-measure...
Few
VU meter works on preamp input put but not on output....
- By Badger777
- Construction Tips
- 17 Replies
Attachments
Why isn't there a dip at driver resonant frequecy (Fo) on frequency response graphs?
- By fairy25
- Full Range
- 2 Replies
Here is the frequency response graph of the Visaton's BG 17 driver, whose Fo = 120 Hz. The response rolls off from 200 Hz to 120 Hz which is understandable because of the rise in impedance.
However, shouldn't the response rises from 120 Hz to 75 Hz since impedance decreases from 22 Ohm to 10 Ohm?
RTi12 crossover measurements for left/right comparative
just aquired these old RTi12's.
In their place have been many varieties of speakers.
the rti12's sounded like they had remarkably bad imaging. from reading user comments these speakers should have decent imaging.
So i've taken some measurements. note am new to this so forgive errors / misunderstandings.
firstly had measured resistance at various points; the left speaker / side seemed to sound better. all seemed normal, variance between speakers at terminals is 0.2ohm iirc; variance between 7" drivers is 0.1 ohm. and no variance with mid/tweeter section of crossover (didn't measure that sections speakers individually)
from there measured with oscilloscope at various points and inputs.
first just to show "baseline" measures; again am new to this.
Pre-Amp with 1000hz input - both channels (Why is positive swing so much lower?)
Amp with 1000hz input - both channels (positive / negative differential not as big, which seems odd to me, given this is the amplified part lol, went back to verify not a connectivity issue and was not whats more both signals show this difference)
and finally Amp with zero input and both channels; note I had "zeroed" the charting with the leads not attached to anything. so this is a measure from that basis. and it sits in the negative side. perhaps that is measuring a DC voltage; subsequent-sorry am new to this and this is a "new perspective" to reading DC voltage for me. seeing electricity in graph over time..i.e thought a bit and realized just now lol can that be adjusted out? I only know of transistor bias adjustment. is there DC adjustment?
That said, imaged below is zero input measured at connection to midrange speaker; which shows balanced leads / zero voltage.
Anyways with that context for the crossover measurements....
The mids I think is the primary issue, below are most remarkable frequencies measured
Mid - 500hz
Compared to 700hz imaged below. The db difference is consistent at this freq. Which component of the cross over would most likely cause this?
Next is Mids - 1000hz (Subsequent - I just noticed left channel positive peaks higher than right, and vice-versa for the negative side. THAT must be the issue am hearing; left side piston stroke is more power and is reversed on right side...that would really mess with the directionality of the sound i figure? any ideas?)
Tweeters
had to change the oscilloscope timing for these frequencies
Tweeters - 2500hz for fun. is the crossover only cutting one side of the circuit, is that what am seeing?
And the amplitude gets crazy from 7500hz and up
5000hz
7500hz
and than 12500; no change in volume setting...
So with just the above, I don't think there is a timing issue. But certainly a crossover issue; and presumably given the age of these speakers and that there is apparently an electrolytic cap within, they're well overdue for a refresh and that will likely get the speakers back inline with each other.
I'd attribute me thinking phase issue at first because of how I didn't really notice much volume difference with up close listing comparatives. but suppose adding in room acoustics, slightly different amplitude, listened to at a normal distance could perhaps impacts sound like that.
Does that all seem reasonable? the difference in measurements between channels is likely due to the crossover. I did measure the drivers and crossover section for ohms and all seemed fine to me. variance of 0.1ohm on the 7"drivers; presume is non-issue. both side had that variance. and at speaker terminals the speakers are within 0.2 ohm iirc. only mean to compare the two speakers here; does not tell me at 35watts, 120hz (lol) what kind of difference there is between them.
what a fun thing, measuring like this. some surprising results. in particular what audessey does to the signal / wave lol a VERY interesting comparative there would be measured at signal & from microphone; see if audessey corrects and to what degree.
In their place have been many varieties of speakers.
the rti12's sounded like they had remarkably bad imaging. from reading user comments these speakers should have decent imaging.
So i've taken some measurements. note am new to this so forgive errors / misunderstandings.
firstly had measured resistance at various points; the left speaker / side seemed to sound better. all seemed normal, variance between speakers at terminals is 0.2ohm iirc; variance between 7" drivers is 0.1 ohm. and no variance with mid/tweeter section of crossover (didn't measure that sections speakers individually)
from there measured with oscilloscope at various points and inputs.
first just to show "baseline" measures; again am new to this.
Pre-Amp with 1000hz input - both channels (Why is positive swing so much lower?)
Amp with 1000hz input - both channels (positive / negative differential not as big, which seems odd to me, given this is the amplified part lol, went back to verify not a connectivity issue and was not whats more both signals show this difference)
and finally Amp with zero input and both channels; note I had "zeroed" the charting with the leads not attached to anything. so this is a measure from that basis. and it sits in the negative side. perhaps that is measuring a DC voltage; subsequent-sorry am new to this and this is a "new perspective" to reading DC voltage for me. seeing electricity in graph over time..i.e thought a bit and realized just now lol can that be adjusted out? I only know of transistor bias adjustment. is there DC adjustment?
That said, imaged below is zero input measured at connection to midrange speaker; which shows balanced leads / zero voltage.
Anyways with that context for the crossover measurements....
The mids I think is the primary issue, below are most remarkable frequencies measured
Mid - 500hz
Compared to 700hz imaged below. The db difference is consistent at this freq. Which component of the cross over would most likely cause this?
Next is Mids - 1000hz (Subsequent - I just noticed left channel positive peaks higher than right, and vice-versa for the negative side. THAT must be the issue am hearing; left side piston stroke is more power and is reversed on right side...that would really mess with the directionality of the sound i figure? any ideas?)
Tweeters
had to change the oscilloscope timing for these frequencies
Tweeters - 2500hz for fun. is the crossover only cutting one side of the circuit, is that what am seeing?
And the amplitude gets crazy from 7500hz and up
5000hz
7500hz
and than 12500; no change in volume setting...
So with just the above, I don't think there is a timing issue. But certainly a crossover issue; and presumably given the age of these speakers and that there is apparently an electrolytic cap within, they're well overdue for a refresh and that will likely get the speakers back inline with each other.
I'd attribute me thinking phase issue at first because of how I didn't really notice much volume difference with up close listing comparatives. but suppose adding in room acoustics, slightly different amplitude, listened to at a normal distance could perhaps impacts sound like that.
Does that all seem reasonable? the difference in measurements between channels is likely due to the crossover. I did measure the drivers and crossover section for ohms and all seemed fine to me. variance of 0.1ohm on the 7"drivers; presume is non-issue. both side had that variance. and at speaker terminals the speakers are within 0.2 ohm iirc. only mean to compare the two speakers here; does not tell me at 35watts, 120hz (lol) what kind of difference there is between them.
what a fun thing, measuring like this. some surprising results. in particular what audessey does to the signal / wave lol a VERY interesting comparative there would be measured at signal & from microphone; see if audessey corrects and to what degree.
Balancing the secondaries
- By kwadrofonik
- Power Supplies
- 4 Replies
Hi I'm working on a 2 channel Marantz amp. I moved the bridge rectifiers and main caps off the board to a discrete power supply, followed by 18ga shielded copper wires back to their original location where extra 2200uF caps are in their place. I've also installed a DAC module.
The amp has two sets of secondaries, one powering the transistors and the other powering everything else.
1. The original configuration has the 0V lines tied together at the main caps by a small wire. Was this an afterthought, or was it intentionally a wire rather than a board trace? Should I leave it there, should I move it to the new power supply (closer to the transformer), or should I remove it now that I've added more capacitance?
Before:
After:
2. I'm worried that I'm drawing too much current from the positive swing of the second secondary. Is this sub-optimal for the op-amps? Will they have too much of a negative bias thereby affecting sound?
I'd love to power the DAC with the negative swing but I would need a negative buck regulator which is rare, and I would also have to isolate the casing of the DAC module because it will still be 12V south of the "grounded" amp casing, creating a short.
Am I being stupid trying to use the amp's transformer and I should just add another switching power supply? The off-the-shelf ones are more noisy than the mini buck regulator I think.
Thanks!
The amp has two sets of secondaries, one powering the transistors and the other powering everything else.
1. The original configuration has the 0V lines tied together at the main caps by a small wire. Was this an afterthought, or was it intentionally a wire rather than a board trace? Should I leave it there, should I move it to the new power supply (closer to the transformer), or should I remove it now that I've added more capacitance?
Before:
After:
2. I'm worried that I'm drawing too much current from the positive swing of the second secondary. Is this sub-optimal for the op-amps? Will they have too much of a negative bias thereby affecting sound?
I'd love to power the DAC with the negative swing but I would need a negative buck regulator which is rare, and I would also have to isolate the casing of the DAC module because it will still be 12V south of the "grounded" amp casing, creating a short.
Am I being stupid trying to use the amp's transformer and I should just add another switching power supply? The off-the-shelf ones are more noisy than the mini buck regulator I think.
Thanks!
Armstrong 600 series balance potentiometer
- By harkonnen
- Solid State
- 4 Replies
[comment][/comment]Hello Forum!
This is my first post here - wooo!
I come to you with a problem. I have an Armstrong 625 receiver (I also have a 621) working 99% ok. The only problem is the balance. In the neutral point only left plays. As I go toward right left start fading, right nothing. When I am about 80% to the right, right starts playing loud (as it would play if it would be at that sport). I suspect since the unit was store in a damp area, the potentiometer is damaged (it also moves hard to the right than other potentiometers). How can I replace it? I look on the internet but I could not find any potentiometers for this specific units. I suspect is a common one. But I need to identify it.
Can you help me?
Ive attached a picture form internet, but it is similar to my unit (even tho this is 621, the part is the same)
Thank you!
Hk
This is my first post here - wooo!
I come to you with a problem. I have an Armstrong 625 receiver (I also have a 621) working 99% ok. The only problem is the balance. In the neutral point only left plays. As I go toward right left start fading, right nothing. When I am about 80% to the right, right starts playing loud (as it would play if it would be at that sport). I suspect since the unit was store in a damp area, the potentiometer is damaged (it also moves hard to the right than other potentiometers). How can I replace it? I look on the internet but I could not find any potentiometers for this specific units. I suspect is a common one. But I need to identify it.
Can you help me?
Ive attached a picture form internet, but it is similar to my unit (even tho this is 621, the part is the same)
Thank you!
Hk
Ring mount tube sockets on 2mm aluminium, will they fit?
- By nzoomed
- Tubes / Valves
- 14 Replies
Im looking at using this style of socket in my next build with a 2mm aluminium chassis.
Will they fit? Im guessing the thickness of the ring will make it too tight?
Any other suggestions? Im getting it laser cut, so shape is nothing to worry about with punches, etc.
Will they fit? Im guessing the thickness of the ring will make it too tight?
Any other suggestions? Im getting it laser cut, so shape is nothing to worry about with punches, etc.
Layout of Ethernet Isolators
- By TomJones
- Digital Source
- 135 Replies
Hello everybody,
Since I have noticed a very positive effect on the sound of several end devices through Ethernet isolators directly in front of the end devices when streaming music, I am currently working on their construction and building some myself.
Ethernet magnetics are used for isolation, which are also used for coupling with Ethernet end devices. These usually consist of a transformer with a common mode choke behind it. This reduces noise on the line, which is noticeable in the better sound.
Picture of the DeLock Isolator:
Here is picture and a circuit diagram of a typical 100BaseT transformer:
The center taps on the cable side are terminated with the Bob Smith termination: termination with 75Ohm resistor and 1000pF capacitor to ground.
The center taps on the PHY side of the transformer are integrated in the connection to the PHY.
As you can read here, the Bob Smith circuit is not without controversy: Why is Bob Smith termination for Ethernet recommended if it's wrong? - Electrical Engineering Stack Exchange
When using the Ethernet magnetics as an isolator, it is in the middle of the cable - so it has no PHY side.
Are there any suggestions as to whether the center taps should also be terminated with bob smith termination or whether not to terminat? Should one make the termination against earth?
Would really be grateful for any input.
Best regards,
Tom.
Since I have noticed a very positive effect on the sound of several end devices through Ethernet isolators directly in front of the end devices when streaming music, I am currently working on their construction and building some myself.
Ethernet magnetics are used for isolation, which are also used for coupling with Ethernet end devices. These usually consist of a transformer with a common mode choke behind it. This reduces noise on the line, which is noticeable in the better sound.
Picture of the DeLock Isolator:
Here is picture and a circuit diagram of a typical 100BaseT transformer:
The center taps on the cable side are terminated with the Bob Smith termination: termination with 75Ohm resistor and 1000pF capacitor to ground.
The center taps on the PHY side of the transformer are integrated in the connection to the PHY.
As you can read here, the Bob Smith circuit is not without controversy: Why is Bob Smith termination for Ethernet recommended if it's wrong? - Electrical Engineering Stack Exchange
When using the Ethernet magnetics as an isolator, it is in the middle of the cable - so it has no PHY side.
Are there any suggestions as to whether the center taps should also be terminated with bob smith termination or whether not to terminat? Should one make the termination against earth?
Would really be grateful for any input.
Best regards,
Tom.
Four lug capacitor replacement
Hi all,
I am using a NABU case from Nebraska Surplus to build another Pass B1 buffer. This will be my second with the NABU case, which comes with an 18v power supply.
Alas, the units date to the mid-1980s. The caps physically look good, but given their age and ease of replacement, it seems like a good idea to replace them.
The main filter cap is a Rubycon CE 69 W (22,000uf, 16v), which is listed as a snap-in capacitor.
The confusing part is that the cap has four lugs. One is clearly a dummy, two are clearly active, and one is?
The cap has a diameter of 40mm and the live lugs are not centered, but toward one side.
(Picture is not mine, but the cap illustrated is the same series):
The lug on the left-hand side (9:00 o'clock) is definitely a dummy used for support purposes.
My question is if I would I order a 3-lug replacement?
Thanks for any help you can give me!
I am using a NABU case from Nebraska Surplus to build another Pass B1 buffer. This will be my second with the NABU case, which comes with an 18v power supply.
Alas, the units date to the mid-1980s. The caps physically look good, but given their age and ease of replacement, it seems like a good idea to replace them.
The main filter cap is a Rubycon CE 69 W (22,000uf, 16v), which is listed as a snap-in capacitor.
The confusing part is that the cap has four lugs. One is clearly a dummy, two are clearly active, and one is?
The cap has a diameter of 40mm and the live lugs are not centered, but toward one side.
(Picture is not mine, but the cap illustrated is the same series):
The lug on the left-hand side (9:00 o'clock) is definitely a dummy used for support purposes.
My question is if I would I order a 3-lug replacement?
Thanks for any help you can give me!
Headphone amp for 32R cans
- By baudouin0
- Tubes / Valves
- 18 Replies
Since we were having a discussion on driving low impedance headphone which had poor SPL, I've put some an method of driving these. I have use an audio line level transformer say 6:1 to do the impedance conversion.
