[Jay Compton]

Here are the results from today's measurements, lucky I only had to add one filter to get the results I wanted. Changing the tubes in my pre amp sure made a big difference in the two SPL's. The Reference Level is where I started today and the Tape Deck Level is the finished product, sounds great I am happy with the results. You can go back and look at the original SPL's that i had before the tube change to compare if you like, I think it's post #62.

 

[jtalden]

...sounds great I am happy with the results.

That's what counts - good adjustment.

FYI, The preamp alone could have been measured to directly see the impact of old vs new tubes.

 

[Jay Compton]

That's what counts - good adjustment.

FYI, The preamp alone could have been measured to directly see the impact of old vs new tubes.

Ok John,
How would I go about doing that?

 

[jtalden]

• Retain the analog cable from the soundcard output to the preamp input.
• Disable phantom power on the soundcard input.
• Connect the preamp output to the soundcard input instead of; Xilica/Speakers/Mic.
• Disable the mic correction file.
• set a low preamp gain level, check levels in REW and adjust the gain to a test level.
• Measure the channel
• Repeat using the other preamp channel.

This just confirms the proper response of the preamp using the new tubes and provides a baseline if you later suspect there is a problem, or want to confirm that its time to replace the tubes again.

 

[Jay Compton]

Hi John,
Ok I see where your going with this thanks, the reason for remeasuring was that after I changed the tubes in the pre amp I heard a dramatic difference in sound quality. The new tubes are so much more linear that it was staggering!!! Anyway it was like taking a blanket off the speakers, not that it sounded bad before because it didn't. The new sound is just that much better but it needed a touch of adjustment in the 6khz-10khz range, one filter correctly implemented worked like a charm...
Gonna listen to it this week as is and decide if it's good or needs more, my feeling is i am done!!!

 

[Jay Compton]

Hi John,
Here are the results from today's measurements, hopefully this is what you wanted. Left Channel, Right Channel, then both together, now this is exactly the same as when we finished the work last year only the tube change is different.

 

[jtalden]

Jay,
See the Impulse overlay chart below. The right and left channels have opposite polarity again. We had this problem before and you found the it was a TS rather than a TRS adaptor you were using if I remember correctly. The channels were actually the same polarity but the measuring system inverted the right channel measurement. This may be the problem again?

The "Both" SPL is suppressed and that is also indicative of the same issue.

 

[Jay Compton]

John,
Ok I will check the wires used I may have used the wrong ones but, I thought I through the other ones out so this wouldn't happen again. I will get back to you soon enough thanks brother.

Jay

 

[Jay Compton]

Hey John,
I am using the correct TRS connector, so I must have changed a setting in the interface without realizing. I am sure though that I didn't change anything I guess I messed up when checking the levels, I was having trouble at first. sorr man i need to go through the whole thing again to be sure I have it right. Weird sometime I get this stuff easy but when something goes wrong I am at a loss as to why...

 

[jtalden]

If you have any problem identifying the measurement problem, let us know what soundcard and wiring you are using for the measurements. I have forgotten your situation.

You can also just use the current Left and Right measurements to calculate the "Both" measurement. That will be the most reliable method anyway. If the mic is not centered perfectly using a sweep measurement for "Both", it will result in the high frequency not being shown accurately.

To combine them in REW first invert the right impulse. Then align the left and right impulses in time. [This 2nd step was not necessary this time as they are already aligned correctly by REW.] Then use REW Arithmetic A + B to get the correct result. The result of that is shown below. I also attached the modified mdat file.

View attachment Post-86ja.mdat

 

[Jay Compton]

Hi John,
I checked in the preferences and found a couple things different than what I remember, I won't know if that was the problem until tomorrow when I setup and measure the room. From the look of what you posted it looks like everything is as it should be? If what you posted is correct to me that looks like where I want to be? As I said it still sounds awesome other than maybe a slight bit hot on the HF end but, that may be due to the source material. Your advice after seeing your result would be to do what? Thanks.

 

[jtalden]

Jay,
The timing/phase rotation looks good - no reason to think there is a problem in that regard.
The SPL response of the 2 channels is very similar so no problems in that regard either.
The SPL of A + B is very similar to my preferred house curve:

There are no significant concerns. If you just want to make a small adjustment to both channels that may be worth a try you could make the EQ adjustment below. I would not think this would be a notable improvement it is just something to try if you are looking for a minor touchup.

Below is the same adjusted response, but using the psy smoothing instead of 1/24 octave. I like to look at the data with various levels of smoothing, but recently have been most influenced by psy smoothing recently.

If you want to address the Hot HF specifically, you can just adjust the house curve accordingly and reset your overall EQ to match. It's really not likely I can suggest effective changes for you. Your own experimentation of with house curve/EQ changes is best route to follow. Good luck!

 

[Jay Compton]

John,
Thanks so much for having a look much appreciated, after reading you post and seeing your earlier work with regard to inverting the right channel in the impulse window I feel like it is real good. I mean to me the channels individually look like what I consider a good match, only did I question it when I looked at both channels together. I am thinking that because the right channel was inverted that threw off that individual response? Once I saw your corrected response I felt like that's what it should be based on the left and right individual responses. I am gonna test some tomorrow to be sure my feeling now is that my TT is in need of a minor adjustment because it is where I am hearing the hot HF. Thanks again.

 

[Jay Compton]

Ok John,
I have tried everything I can think of and nothing I do will change the right channel back to a positive polarity!!! I am exhausted trying to figure this out with no ground gained. I will need your help to figure this out, send me a message and I will call you when you have time.

 

[jcmusic23]

I should have posted this a long time ago, anyway here it is in all it's glory a huge thanks to john for all his help!!!