Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Crack-a-two-a => Topic started by: XforceVesa2 on January 18, 2020, 06:21:08 PM
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Hello Community,
I've Build my Crackatwoa a few weeks ago and everything seems fine , except one thing.
I was the entire time unsure if my Crackatwoa actually has an channel Imbalance or not because I could swear that im Hearing the Left channel a little bit louder than the right channel and thought it was just my imagination.
But today I took measuring from my Headphone Cable (HD 600 the Cable is Detachable) and got the following measurements:
At my "normal" listening Volume I've got:
L = 0,22V
R = 0,21V
So it equals to (if I'm not mistaking) an Channel Imbalance of 0,4 dB.
I've took another measuremnt, this time with the Volume upt to 0dB(I have the TwoQuiet Stepped attenuator) and got these measurements:
L = 12,05V
R = 11,29V
So the channel Imbalance is 0,6 dB.
I hope you can help me with that Problem.
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Can you repeat the test but measure Q7 and Q9 instead (the amp can be off) just to ensure that the channel balance is OK coming out of the attenuator?
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I've measured Q7 and Q9 with the Volume set to max(0dB) and got the Following Measurements:
Q7 = 1,06V
Q9 = 1,08V
Edit: I've used for all my measurements a 60 HZ Test Tone.
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The attenuator balance looks good.
A problem like this is usually either a solder joint that isn't 100%, or just a bit of tube imbalance (in the 12AU7).
-PB
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Good to Know :D
Are there Input tubes out theres that have a little better Channel balance?
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It's a bit of a roll of the dice unless you pay a tube vendor for one that has been manually checked. You may also find that the imbalance fades a bit once the tube has been run in for 100 hours. This of course presumes that the tube is the issue and not a flaky solder joint. If it's a bad joint, then all 12AU7s will appear to have the same imbalance.
How are the OA/OB voltages on your center PC board?
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I've got at OA = 70,3 V and at OB = 73,2 V
Edit: I don't know if it could have to do with that problem but If I look at my Input tube it seems like that on the bottom part of that tube one side glow a little bit brighter than the other?
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12AU7 tubes are relatively cheap, even some NOS ones. There are NOS Sylvania made for Baldwin organs 12UA7 tubes on sale for $12.00 right here for example:
http://www.audiotubes.com/12au7.htm (http://www.audiotubes.com/12au7.htm)
Much further down on the same page they offer GE organ stock tubes for $9.00. Current production 12AU7 tubes cost roughly the same.
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The glow won't necessarily be even, and you have healthy voltages at OA and OB, so the tube is working nicely.
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I can swear that I can hear the Channel Imbalance(Left is a little bit Louder).
Are there any contacts in the Amp that I can measure too to find the "Possible" Problem?
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When the 12AU7 has amplified the signal, there is DC in the presence of the AC voltage. You could try measuring the AC voltage at pins 1 and 4 on the octal socket, but your meter may not resolve the AC on top of the DC all that well.
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I would measure this next Time.
Should I check all Solder joints in the Amp or only these near the Input and Power Tube?
During the Build I've checked almost all Solder Joint with my eyes and my multimeter(checked the connections from one solder joint to another with the Impedance check that its always shows 0.00 Ohms).
In the Input socket both leds are lit bright if the amp is On, only on the Larger PC Board I've noticed that the Leds on it doesn't lit so brightly like the Others Leds did.
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There is another way you can measure before you do a whole lot of work. This is going to be short, because I'm in a rush.
Do you have a soundcard in a computer? If, yes, then:
find online or create yourself a 1kHz signal at least 30 sec long / loop if shorter
play it back through soundcard and measure with AC rms meter - adjust - 0.77V or 0.5V are both good
install voltage divider in eros input - go for something like -40dBV or a bit more attenuation
play signal from soundcard into one channel of Eros at a time and use the same output on the soundcard for both Eros channels
that way you can be sure that what goes in is the same for both Eros channels
measure AC V rms at the output
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That is a good plan for the Eros, but this is a Crack-a-two-a.
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Could the Channel Imbalance have something to do with the Large PC Board as stated above?
What Channel Imbalance does the Crackatwoa normally have?
Are these Values that I have measured at the begin at this Thread a imbalance that normally Occur at this Amp?
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Could the Channel Imbalance have something to do with the Large PC Board as stated above?
What Channel Imbalance does the Crackatwoa normally have?
Are these Values that I have measured at the begin at this Thread a imbalance that normally Occur at this Amp?
A problem like this is usually either a solder joint that isn't 100%, or just a bit of tube imbalance (in the 12AU7).
As I mentioned before, channel balance is far more tube dependent than circuit dependent. Creating a spec for channel balance would require a sample of maybe 100 12AU7s to give an average expected channel balance along with the distribution of what was actually measured. This is one consequence of not having global feedback, if we put feedback around the amp I could make the channel balance less than 1/4 of a dB pretty easily.
Could the Channel Imbalance have something to do with the Large PC Board as stated above?
Which board is the large board? Can you post a photo of what you're seeing?
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I was and I still am in a rush. Sorry. Plan can be adapted to the Crackatwoa, skip the attenuation, set the volume control to a couple of different points, three or so, alternate channels at each setting.
I suggested buying another one or three reasonably priced 12AU7 tubes because the amplification factor of the Crackatwoa depends on that a lot.
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As I mentioned before, channel balance is far more tube dependent than circuit dependent. Creating a spec for channel balance would require a sample of maybe 100 12AU7s to give an average expected channel balance along with the distribution of what was actually measured. This is one consequence of not having global feedback, if we put feedback around the amp I could make the channel balance less than 1/4 of a dB pretty easily.
Which board is the large board? Can you post a photo of what you're seeing?
Ok I think I now understand what you meant :D
I have again took an Inspection of the Socket from the Input tube and couldn't find a problem.
The solder joints seemed fine, I have measured the impedance from one solder joint to another end e.g hold one probe of the multimeter against one pin and the other probe at the other end of the soldered wire, my reading was 0.00 Ohms, also the two LEDs on the Input socket lit bright when the amp is On.
I've meant the Low Current C4S Board.
I don't have a problem with the slight channel imbalance I was just worried that I've could made a mistake in the circuit and thats what I just wanted to be sure that there's no mistake in my cicruit :D
If the channel Imbalance comes from the Tube then I can live with that.
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If you have a large difference in LED brightness on the center low current C4S board, that would tend to indicate a possible soldering problem.
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I have uploaded 4 Pictures that shows the different leds on the circuit.
I've meant that all the LEDs in the Amp seems to lit equally except the LEDs on the Low Current Board(the four LEDs on this boards are equally less lit than the other LEDs in the Amp).
I hope that the pictures shows it better than what I try to explain what I mean(Its not my native language) :D
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Yes, the LEDs on the low current board aren't biased with as much current as the high current boards. The LEDs on the 9 pin socket also have more current flowing through them than the LEDs on the low current board, so all is normal.
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I've just swapped the 12AU7 Input Tube from my Crackatwoa with my other 12AU7 Input Tube from my Crack but the Channel Imbalance doesn't Dissapear, does that means that I must have a bad solder joint somewhere in my Amp?
Edit: The Crack seems to also have a Channel Imblanace (Left is a little bit Louder than right but its better than on the Crackatwoa). I've noticed that the channel balance was a little bit better as I've used the Power Tube from the Crack(But that doesn't make any sense? )
Edit 2: I think If my Previous Amp the Crack and my new Amp the Crackatwoa shows the same Phenomen I think it's very unlikely that I've probably made the same mistake the second time(Left a little bit louder), and I think it's actually more depent on the Tubes I'm using(Stock Tubes from Crack and Crackatwoa) as you have stated earlier in this Thread.
Edit 3: I've made new Measuremtns directly from the Headphone Cable with two Volume Settings as at the start of this Thread.
I've swapped the Stock Tube from the Crackatwoa with the Stock Tube from the Crack(seems to be a 6AS7 instead of a 6080).
At my "Normal" listening Volume I've got this Time:
L = 0,22 V
R = 0,208 V
So an Imbalance of 0,5 dB
At the max setting(0dB) I've got
L = 11,85 V
R = 11,2 V
So an Imbalance of 0,5 dB
The Strange thing is that in my Opinion the Channel Balance with the Stock Tube from the Crack(6AS7) is a little Better than the Balance from the Stock Powertube(6080) from the Crackatwoa.
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There is some opportunity for channel imbalance to creep in from the 6080, but it's less likely in my opinion.
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Since both amps show the same/similar imbalance when measuring from your headphone cable, you may want to rule out the cable as the cause of the problem. I'd try measuring from the rca outputs themselves. Alternatively, you could swap left and right cable plugs and see if the imbalance follows the cable.
cheers, Derek
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I've mad new measurments on the Crackatwoa and it seems like that the Channel Imbalance is at every Volume setting at about 0,5dB.
I've also made new measurements on the Crack with different Volume settings and it seems like that the Channel Imbalance on the Crack is a lot lower than on the Crackatwoa(only about 0,2dB).
I don't know what causes this Imbalance on the Crackatwoa as all solder joints seems to be ok :/
Edit: The strange thing is if I plug the Input Tube from the Crack in the Crackatwoa the Channel Imbalance seems to be going worse(about 0,6dB)
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Are these measurements on the Crack-a-two-a without headphones plugged in? If not, do be sure to give that a try too.
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Are these measurements on the Crack-a-two-a without headphones plugged in? If not, do be sure to give that a try too.
The Headphone wasn't plugged in during the measurements(Only the cable as the Headphone is detachable from the Headphone cable)
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I don't think I know any mastering engineers who can hear a .2dB differential. The average listener can typically make out 3dB, a practiced audiophile can maybe hear 1dB. Best I've ever seen measured was my old partner Paul Stubblebine who could make out .25dB. I used to be able to discern about .5dB. Don't know if I could these days.
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The thing is before I made these measurements, I've noticed the Imbalance while I heard music.
Later I've checked the Balance with a Stereo Perception Test from Audiocheck.net, they used a monoraul Recording of someone Knocking on the Door.
I could easily hear that the Left Side was louder than the right side, I've turned the Headphone around and heard clearly that this time the right side was Louder than the Left Side.
After that I decided to take measurements directly from the plugged in Headphone cable and could see that the left side has a little more Voltage than the right Side and that the Imbalance I've measured is around 0.5 dB :/
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You could try swapping the red and white wires at the headphone jack.
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You could try swapping the red and white wires at the headphone jack.
If you determine that the cable is not the source of the imbalance (i.e., slightly higher impedance on the right channel than on the left), is there any possibility that the imbalance is coming from your source? I could see this being the case if, for example, you were using your phone or computer as both your music source and the source of your test tone for taking voltage output measurements.
If the amp is in fact producing the imbalance, maybe some Kaiju-style PEC trimmer pots would be the way to go. Alternatively, maybe PB could figure what small resistor value is needed to knock down the left channel input and you could add that in series with the left signal volume pot wiring.
cheers, Derek
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If you determine that the cable is not the source of the imbalance (i.e., slightly higher impedance on the right channel than on the left), is there any possibility that the imbalance is coming from your source? I could see this being the case if, for example, you were using your phone or computer as both your music source and the source of your test tone for taking voltage output measurements.
If the amp is in fact producing the imbalance, maybe some Kaiju-style PEC trimmer pots would be the way to go. Alternatively, maybe PB could figure what small resistor value is needed to knock down the left channel input and you could add that in series with the left signal volume pot wiring.
cheers, Derek
I use as a Source the iFi Micro iDSD Black Label. The Crackatwoa is directly connected with the RCA LineOut from the iFi(the switch on the iFi for the LineOut is set to "Direct"(it's basically a passthrough) so that the Volume control from the iFi doesn't interfere with the RCA LineOut.
I've got the Following measurements directly from the RCA Output from the iFi:
L = 1,434V
R = 1,463V
So an imbalance of about 0,2dB
The strange thing here is that it seems like that the right side is louder than the Left side before it goes trough the amp. It's like that the channel in the amp gets inverted?
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I've took a new measurement this time Directly on the contacts U6 (Red whire) and U15 (White Wire) and got the following measurements:
Normal Listening Level:
White Wire = 0,22V
Red Wire = 0,209V
So an Imbalance of 0,5 dB(RAW Value = 0.445267)
At max Setting(0dB)
White Wire = 11,92V
Red Wire = 11,25V
So an Imbalance of 0,5dB(RAW Value = 0.502019)
From this contacts there goes a capacitor to the High Current Boards(I think the capacitator is there to decouple the AC Voltage from the DC Voltage?), could the Imbalance have something to do with the socket for the Shunt Tube or the High Current Board?(For the Red Wire, Right Channel)
Edit: I can't find any problem on the Shunt Socket and the High Current Board(Fort the Right channel, Red Wire) :/
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You could pull the shunt regulator tubes out completely and you'd most likely find no change in the channel balance.
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You could pull the shunt regulator tubes out completely and you'd most likely find no change in the channel balance.
As I can't find the cause of this Imbalance do you think it could help if I buy a 12AU7 from an seller that states thats an Balanced Matched Tube?
Like this one? : https://www.tubeampdoctor.com/en/12au7a/ecc82-tad-premium-selected-balanced
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It is certainly an option and could provide useful data.
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I've purchased one.
I hope that it could be a solution to this problem.
I report when I get my hands on this Tube and do a new measurement.
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When I got the new input Tube and the Balance didn't get better what measurements or checks could I also do?
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That was quick, you were able to buy a balance tested 12AU7 in 2 hours?
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That was quick, you were able to buy a balance tested 12AU7 in 2 hours?
It was more Like an what if? Question :)
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Holy smokes, take a chill pill, smoke a bowl or have a drink and relax.
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Holy smokes, take a chill pill, smoke a bowl or have a drink and relax.
Yeah, I think you're right. I'm a little bit impatient at the moment. Sorry for that.
I 'll report as stated above when my new Tube arrives and if this change something or not.
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Oh, I didn't understand that.
Let us know what happens when it arrives.
-PB
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Sooo I've got my new 12AU7A/ECC82 Input Tube today and got the Following Measurements:
At my "Normal" Listening Volume I've got the Following Measurements:
L = 0,239 V
R = 0,23 V
So an Imbalance of 0,3dB(RAW Value 0.333147)
I've done this time another measurement with The Volume set a little bit quieter than my Normal Listening Volume and got the following measurements:
L = 0,169 V
R= 0,163 V
So an Imbalance of 0,3dB(RAW Value 0.3139)
And the last measurement at max Volume:
L = 12,29 V
R = 12,15 V
So an Imbalance of only 0,1dB(RAW Value 0.099318) :O
If I compare this measurements with my first measurement it seems like that the Channel is now more in balance(The Imbalance is now more harder to hear).
It seems like that the possible cause of this "Issue" come from the Stock 12AU7.
The new 12AU7A/ECC82 was a little more expensive and the shop has stated that this Tube had an Balanced Output Test.
Is it normal that the Imbalance got fewer as I turn up the Volume even with the Twoquiet Stepped Attenuator as the measurements indicate?
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What's the channel balance of your source?
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What's the channel balance of your source?
I use as a Source the iFi Micro iDSD Black Label. The Crackatwoa is directly connected with the RCA LineOut from the iFi(the switch on the iFi for the LineOut is set to "Direct"(it's basically a passthrough) so that the Volume control from the iFi doesn't interfere with the RCA LineOut.
I've got the Following measurements directly from the RCA Output from the iFi:
L = 1,434V
R = 1,463V
So an imbalance of about 0,2dB
The strange thing here is that it seems like that the right side is louder than the Left side before it goes trough the amp. It's like that the channel in the amp gets inverted?
EDIT: Out of Curiosity I've did an hearing test to determine the Loudness differents between two channels via the Site Audiocheck.net what I'm able to hear.
The tests shows me that I can reliable tell a loudness different with 1dB but with 0.5dB I couldn't reliable tell if there's a channel Imbalance or not.
I've did a test with my other(cheap) Headphone and the strange thing here is that it seems like that on this Headphone(It's a Headphone with USB Plug that I'm using on my Main PC) the Left Side also to be seems louder than the right side and if I turn this headphone I can clearly hear that the right Side is louder than the Left side(This Headphone wasn't plugged in my Music PC nor in the Crackatowa). That all doesn't make sense ???
So technically I shouldn't be able to Hear this Channel Imbalance of 0.3dB as Doc. B stated ???
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The brain is a rather mysterious organ.
If you want to compensate for all of this, it's probably possible to adjust the resistor values on the coarse side that's louder to compensate, but that seems a little bit intense for what this is.
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Hey PB.
I am resisting the urge, Should I just relax?
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If the imbalance you're hearing still bugs you, you could consider replacing the stepped attenuators with the analog pots so you'll have the balance control and listen to that for awhile. Who knows, the sound may be agreeable.
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Ditto! or relax and enjoy. Or buy 0.1% tolerance passive parts and stress about something else about your life.
You have stated that your source has an imbalance so get real!
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Ditto! or relax and enjoy. Or buy 0.1% tolerance passive parts and stress about something else about your life.
You have stated that your source has an imbalance so get real!
It seems like that makes you a little stressed out as soon as I ask a Question. You always seems to answer me that I should e.g. relax, chill instead of giving me a normal Answer as the Other Users in this Forum did.
As I said I did a Hearing Test to determine if I'm even able to Hear this Channel imbalance(at the moment only 0.3dB). It seems like that I can only reliable tell a Difference with an imbalance of about 1dB what means that I can't tell a difference with 0.3dB.
I get it that the whole Thread is possible pointless as even an imbalance of 0.6dB I can't hear.(What I discovered at the Hearing Test)
Even as (in my opinion) your answers was a little bit rude, I think you've got a point with "relax and enjoy".
I would like to Thank the Forum for the patience to Answer my Questions and I think the best thing I can do with the Crackatwoa is simply to "relax and enjoy" the Sound of this Amp.
Out of Curiosity I have a last Question about the Amp. Does the L and R channel get inverted as it goes trough the Amp?
Just a little Edit: Sorry if some words or sentences that I write could be wrong interpreted as it's not my native language.
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Does the L and R channel get inverted as it goes trough the Amp?
Just to clarify, I think you are asking whether the amp swaps left and right signals - i.e., whether the left input signal appears on the right output rca jack, and vice versa? I assume you mean this because you've measured the channel imbalance of your source and found that it is opposite to the imbalance coming out of your C2A, and so your hypothesis is that the amp swaps left and right signals, thereby passing on the imbalance of your source. Do I have that correctly?
(I ask the above clarifying questions b/c in audio-speak the term "inverted" often refers to phase inversion - i.e., if you imagine a sine wave signal with a positive peak at time 1 and a negative peak at time 2, the inverted version of that sine wave would be flipped 180 degrees: a negative peak at time 1 and a positive peak at time 2. I don't think you are asking about phase inversion -- but please correct me if I am wrong).
Re whether left and right signals are swapped: I'm pretty sure that none of BH's amps swap left and right signals b/c (a) that would significantly change the presentation of music (e.g., horns that should be on the left are instead on the right), and (b) I can't imagine any circuit design reason/benefit to swapping signal sides. I think the only way for the signals to get swapped is by user/builder wiring error - my guess would be at the attenuators. So you might want to double-check your signal wiring.
cheers, Derek
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Just to clarify, I think you are asking whether the amp swaps left and right signals - i.e., whether the left input signal appears on the right output rca jack, and vice versa? I assume you mean this because you've measured the channel imbalance of your source and found that it is opposite to the imbalance coming out of your C2A, and so your hypothesis is that the amp swaps left and right signals, thereby passing on the imbalance of your source. Do I have that correctly?
(I ask the above clarifying questions b/c in audio-speak the term "inverted" often refers to phase inversion - i.e., if you imagine a sine wave signal with a positive peak at time 1 and a negative peak at time 2, the inverted version of that sine wave would be flipped 180 degrees: a negative peak at time 1 and a positive peak at time 2. I don't think you are asking about phase inversion -- but please correct me if I am wrong).
Re whether left and right signals are swapped: I'm pretty sure that none of BH's amps swap left and right signals b/c (a) that would significantly change the presentation of music (e.g., horns that should be on the left are instead on the right), and (b) I can't imagine any circuit design reason/benefit to swapping signal sides. I think the only way for the signals to get swapped is by user/builder wiring error - my guess would be at the attenuators. So you might want to double-check your signal wiring.
cheers, Derek
You've pretty Nailed what my intention for my Question was :D
I've tested if the Input signals could be swapped with a little test in the Speaker Configuration on the Operating System.
I've let for an example play only the Left Side and the Sound appears on the Left Side and vice versa, so It doesn't seems like that I have made an wiring mistake with the Left and Right Channel.
It was just a hypothesis as you have already stated :D
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The Crack and C2A are inverting, yes.
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I apologize if my posts seemed rude. My sense of humor is often misunderstood. Rest assured that I will keep my trap shut.
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I've made completely new Measurements as I got a new Source(RME ADI-2 DAC) and because I was just curious what measurements I get this Time.
First I measured the Source from the ADI 2 DAC and got the Following measurements:
L = 1,2136V
R = 1,2138V
So an "Imbalance" of 0.001424 dB, so basically a perfect Balanced Source :D
The next measurements I've made with Different Tube Setups.
The first measurements I've used as Input Tube The TAD 12AU7/ECC82 Tube and the Stock Tube from the Crack(6AS7) and got the following measurements(All of the Following measurements are made with my Normal Listening Volume):
L = 0,201V
R = 0,1903V
So an Imbalance of 0.5dB (RAW = 0.474923)
For the second measurement I've used as Input Tube the Stock Tube from the C2A(also a 12AU7/ECC82) and the Power Tube from the Crack(6AS7) and got this:
L = 0,186V
R = 0,172V
So an Imbalance of 0.7dB (RAW: 0.679647)
For the last Measurement I've used as Input Tube the TAD 12AU7/ECC82 Tube and the Stock Power Tube from the C2A(6080) and got this:
L = 0,205V
R = 0,1926V
So an Imbalance of 0.5dB (RAW = 0.541934 dB)
As I've said I did this measurements only because I was curious what would happen If I change the Source.
But I have only one Question, there's one thing I don't understand.
With my Old Source(Ifi Micro iDSD BL) I've got with my current Tube Setup(Input= TAD 12AU7/ECC82, Power = 6AS7(from Crack)) approximately an Imbalance of about 0.3dB( This Source had an Imbalance of about 0.2dB) but with my new Source(ADI-2 DAC(Perfectly Balanced)) and the same Tube Setup I've got an Imbalance of about 0.5dB.
So my Question is how is this even Possible as it seems to get "worse" with the new Source? ???
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If the amp has a slight channel imbalance favoring one channel and your source has a slight channel imbalance favoring the other channel...
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Further to PB's point, I think you found the probable explanation some time ago:
I've got the Following measurements directly from the RCA Output from the iFi:
L = 1,434V
R = 1,463V
So an imbalance of about 0,2dB
The strange thing here is that it seems like that the right side is louder than the Left side before it goes trough the amp.
So it looks like the IFI imbalance and the C2A imbalance partially cancelled out.
It would be an interesting experiment to trace the signal balance through the C2A to see where the imbalance pops up. You've already done some of that by testing the voltages that come out of the attenuator. You got 1.06V out of one side, and 1.08V out of the other. I don't know anything about decibel calculations, but using the following equation I found online, dB difference = 20*log(V1/V2), suggests this you've got a 0.16dB difference. If this calculation is correct, that's part of your answer. PB could probably figure out (or maybe you could) what value of resistor to add in series or parallel at the attenuator to get closer to a zero difference between channels. I don't have a Two-Quiet, so I can't be of any help here.
This is all kind of academic since your hearing test results suggest you won't be able to hear the channel imbalance in any event, but it could be a fun thing to track down and solve.
cheers, Derek
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Further to PB's point, I think you found the probable explanation some time ago:
So it looks like the IFI imbalance and the C2A imbalance partially cancelled out.
It would be an interesting experiment to trace the signal balance through the C2A to see where the imbalance pops up. You've already done some of that by testing the voltages that come out of the attenuator. You got 1.06V out of one side, and 1.08V out of the other. I don't know anything about decibel calculations, but using the following equation I found online, dB difference = 20*log(V1/V2), suggests this you've got a 0.16dB difference. If this calculation is correct, that's part of your answer. PB could probably figure out (or maybe you could) what value of resistor to add in series or parallel at the attenuator to get closer to a zero difference between channels. I don't have a Two-Quiet, so I can't be of any help here.
This is all kind of academic since your hearing test results suggest you won't be able to hear the channel imbalance in any event, but it could be a fun thing to track down and solve.
cheers, Derek
It's an interesting Idea but as It's only an Imbalance of 0.47 dB this step seems a little bit drastic as Paul has stated before :D
Just out of Curiosity what Channel Balance does the other Crack and C2A users on this Forum measure on their Headphone Jack? :D
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Just out of Curiosity what Channel Balance does the other Crack and C2A users on this Forum measure on their Headphone Jack? :D
You're the only one...
I did leave space in the layout to add feedback resistors, which would tighten up the channel balance.
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You're the only one...
I did leave space in the layout to add feedback resistors, which would tighten up the channel balance.
Ok..(I thought that some Imbalance is normal on this Amp(So I have misunderstood this)) :/
If I want to add feedback resistors in this circuit where must they placed?
Before I consider to add feedback resistors in this circuit, should I resolder the solder joints from the Input Tube Socket and from the High Current PC Boards?
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No, I meant that most builders wouldn't be bothered by half a dB of imbalance.
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No, I meant that most builders wouldn't be bothered by half a dB of imbalance.
Ok... now I got it.
As this is no real issue, this thread can be seen as Solved and I want to apologize for my nitpicking with the Channel Balance as I'm just waste your and my Time, to fix an Issue what's not an real issue.(As I have tested it for myself that I shouldn't be able to hear this Imbalance).