Tube Rolling w/Crack
- Thread starter Dr. Toobz
- Start date
I see a general consensus about this, but wonder if there has been anything besides subjective analysis.cddc said:
I decided to have some fun last night and recorded the amp's output using two different tubes. One was an RCA 6080 that the kit came with, the other was a Sovtek 6AS7G.
Now this was using a mono guitar cable, so it's only comparing one channel.
I'm not even certain it works that way, but I believe the tip would touch the left channel, and the sleeve would touch the right channel, and the ground of the jack. The input jack is mono so it would only grab the left channel.
Anyway, I got the sovtek from here: https://www.partsconnexion.com/TUBESVT-68351.html
I was getting a new pot and knob already from that store, figured what the hell I'll try a new tube. I think it's new production, the description says new.
It sounded thinner at first, but after a while seemed to become fuller. It's pretty subjective though, more of a feeling like I said before.
So I recorded the amp playing a song with each tube, ran a frequency analysis. I've attached the picture.
The top line is the hold of the highest amp for a given frequency, the bottom is the average. I played the same song for the same amount of time on each.
It seems like the sovtek has slightly better seperation of frequency response? You can see at the very start there's a clear separation in the low end, where the RCA is smoother.
In general this seems to follow across the other frequencys, around 100 you can see the RCA is smoother again.
Anyway, not sure it means much but it was fun to do. I don't know much about this stuff really but it sure is neat.
From an objective standpoint, the sovtek solved a lot of microphonic issues I had with the RCA tube.
From a subjective standpoint, I swear the RCA still sounds a little richer, but I think it's in my head. The sovtek today seems very rich though... it's so subtle it's hard to tell.
I should get someone to help me do a blind test.
Attachments
For measurements like that, you want to use periodic noise that itself would have a flat frequency response. I'd also try to get the level up to about the 0 line. I would also do this with no headphones plugged in, and with the newer version of the Crack, you'd want a 1/4" to 1/8" adapter plugged in to defeat the shorting function of the output jack.
If the Crack was -60dB at 10kHz, we wouldn't sell very many
If the Crack was -60dB at 10kHz, we wouldn't sell very many
Hmm yes, I was looking for some frequency response test audio but couldn't find anything. I guess a noise that plays across all frequencies at the same level would work?Paul Birkeland said:For measurements like that, you want to use periodic noise that itself would have a flat frequency response. I'd also try to get the level up to about the 0 line. I would also do this with no headphones plugged in, and with the newer version of the Crack, you'd want a 1/4" to 1/8" adapter plugged in to defeat the shorting function of the output jack.
If the Crack was -60dB at 10kHz, we wouldn't sell very many
I'm clearly out of my element here...
I picked up a 1/4" TRS to 2 1/4" TS cable. My interface has 2 1/4" mono jacks for recording, this should allow me to record both channels out of the amp's headphone jack, no?
EDIT-
I found this page: https://www.audiocheck.net/testtones_highdefinitionaudio.php
"flat freq response" was the phrase I needed to find it. I'm guessing the white noise would work well for this purpose.
mcandmar
New member
Try Right Mark Audio Analyser (RMAA), does everything for you by playing a frequency sweep, and then measuring the response, distortion, noise floor etc.
Start with a loopback cable and get the level dialled in to 0db and you should be seeing very close to a flat frequency response, then put an amplifier in the loop, set the volume control for the same level and measure again. You can see in the example my cracks response was at the limit of my test setup, except the distortion was order of magnitudes higher, but in a nice tubey way
Download from here https://audio.rightmark.org/download.shtml , i prefer to use the older v5.5 of the software.
Start with a loopback cable and get the level dialled in to 0db and you should be seeing very close to a flat frequency response, then put an amplifier in the loop, set the volume control for the same level and measure again. You can see in the example my cracks response was at the limit of my test setup, except the distortion was order of magnitudes higher, but in a nice tubey way
Download from here https://audio.rightmark.org/download.shtml , i prefer to use the older v5.5 of the software.
Attachments
mcandmar said:Try Right Mark Audio Analyser (RMAA), does everything for you by playing a frequency sweep, and then measuring the response, distortion, noise floor etc.
Start with a loopback cable and get the level dialled in to 0db and you should be seeing very close to a flat frequency response, then put an amplifier in the loop, set the volume control for the same level and measure again. You can see in the example my cracks response was at the limit of my test setup, except the distortion was order of magnitudes higher, but in a nice tubey way
Download from here https://audio.rightmark.org/download.shtml , i prefer to use the older v5.5 of the software.
Oh cool, thanks!
jivex5k said:
Measuring and analyzing the output signal is too complicated to me. But several things I need to point out:
1. The Sovtek 6AS7G is not new production, they are NOS Russian tubes. Though I've never bought any Sovtek branded 6AS7G tubes, I have several Svetlana 6H13C tubes (Russian equivalent to 6AS7G), and they look identical to your Sovtek. I believe they are from the same Russian factory.
2. You paid too much for your Sovtek ($48
), Russian 6AS7G tubes normally cost $10 a pop plus shipping from Ukraine/Russia, that's what I paid.3. NOS Svetlana 6H13C/6AS7G is a decent tube for the price, large soundstage and good bass performance. For $10 I'd pick up a Svetlana 6H13C any day than a crappy RCA 6AS7G. IMHO RCA 6AS7G is the worst 6AS7G tube ever manufactured, muddy nothing but muddy ;D
greenneedle
New member
The adaptor I am using to put a 6sn7 in the 12AU7 socket has quite long pins so it doesn't seat flush like a 12AU7 does. Is there any problem with clipping 2mm off each pin so it will seat properly?
Well I was a bit bored today, searched around for some tubes for fun.
Picked up this bugle boy for 25 bucks: https://www.ebay.com/itm/254626346257
I started searching Mullards at first, was surprised to see them selling for around 500 bucks.
Crazy high prices, I'd rather spend that on SEX kit, or maybe some DIY synth stuff.
Eurorack stuff looks interesting, lots of DIY. Modular stuff sounds pretty good on this amp too, listening to some tracks right now. The highs, they're high but they are airy....? They aren't harsh, and modular stuff can get pretty freakin high pitched. The bass too... man, it really thumps on some songs in a really good way.
It would be a lot of fun to build my own synth and run it through the amp.
Picked up this bugle boy for 25 bucks: https://www.ebay.com/itm/254626346257
I started searching Mullards at first, was surprised to see them selling for around 500 bucks.
Crazy high prices, I'd rather spend that on SEX kit, or maybe some DIY synth stuff.
Eurorack stuff looks interesting, lots of DIY. Modular stuff sounds pretty good on this amp too, listening to some tracks right now. The highs, they're high but they are airy....? They aren't harsh, and modular stuff can get pretty freakin high pitched. The bass too... man, it really thumps on some songs in a really good way.
It would be a lot of fun to build my own synth and run it through the amp.
Here are some Mullard 12AU7s for under $50:
https://www.ebay.com/itm/1-x-12AU7A-ECC82-Mullard-Hammond-Tube-Very-Strong-Balanced-3-Available/283991231062?hash=item421f324a56:g:j2EAAOSwR6NfRuok
https://www.ebay.com/itm/Mullard-Hammond-12Au7A-Vacuum-Tube-Measured-100-90-Gm-on-Amplitrex-1967-Gf2/282981215782?hash=item41e2feae26:g:nfEAAOSw~19bCC5u
https://www.ebay.com/itm/1-x-12AU7A-ECC82-Mullard-Hammond-Tube-Very-Strong-Balanced-3-Available/283991231062?hash=item421f324a56:g:j2EAAOSwR6NfRuok
https://www.ebay.com/itm/Mullard-Hammond-12Au7A-Vacuum-Tube-Measured-100-90-Gm-on-Amplitrex-1967-Gf2/282981215782?hash=item41e2feae26:g:nfEAAOSw~19bCC5u
Colonl_Charisma
New member
Hi all,
I am wondering if changing the input tube makes a difference in the sound of the Crack. If it does what is the input tube that you all enjoy? I tried googling this question, but every thread and article seems to focus on the power tube.
I am wondering if changing the input tube makes a difference in the sound of the Crack. If it does what is the input tube that you all enjoy? I tried googling this question, but every thread and article seems to focus on the power tube.
IMO the 12AU7 makes the bigger difference.
Colonl_Charisma
New member
Thanks PB! That’s good to know.
Have been enjoying rolling 6SN7 tubes with an adaptor, I personally enjoy them a lot more than 12AU7! I have had a slight problem with one 6SN7 in particular and was wondering if anyone could explain what was going on.
my volume pot is aligned with 0 as 7 oclock. The tube produces loud, constant crackle in the right channel from 9 oclock to 4 oclock, but this crackle is barely audible from 7-9 oclock, and dead silent from 4-5 oclock (max volume). Once warmed up a bit, the crackling range is from 10oclock to 4 oclock.
I've never had a tube do this; the other 7 or so 6SN7s I've rolled into this adaptor have all been dead silent, with only one having a faint buzzing noise at the very max volume. I'm currently working around the situation by putting crack volume at max and -50dB on my DAC. I have tried reseating the tube and cleaning the pins. Any insight is appreciated!
my volume pot is aligned with 0 as 7 oclock. The tube produces loud, constant crackle in the right channel from 9 oclock to 4 oclock, but this crackle is barely audible from 7-9 oclock, and dead silent from 4-5 oclock (max volume). Once warmed up a bit, the crackling range is from 10oclock to 4 oclock.
I've never had a tube do this; the other 7 or so 6SN7s I've rolled into this adaptor have all been dead silent, with only one having a faint buzzing noise at the very max volume. I'm currently working around the situation by putting crack volume at max and -50dB on my DAC. I have tried reseating the tube and cleaning the pins. Any insight is appreciated!
Use a different tube.
Paul Birkeland said:
Hi PB, I have a question regarding the power output of 6080/6AS7 tubes. From datasheet 6080 tube has a max plate dissipation of 13W (vs only 3.5W out of 2A3 tube). So it seems 6080 has much higher power output than 2A3 does. But why 2A3 or 300B tubes are normally considered to be more powerful tubes than the 6080/6AS7 class?
I also read somewhere (couldn't remember where now) Crack outputs 0.3W into 300 ohms headphones. The number 0.3W is quite low compared to the max output of 13W from 6080 tubes, why so? Does that mean 6080 is not used up to its full potential, and a lot more juice can be squeezed out of it?
Thanks.
D
Deke609
Guest
That 13W figure in the datasheets refers to maximum "plate dissipation" -- i.e., the waste energy burned off as heat at the plate. Max power of the signal output of the tube will be a fraction of that figure. For example, the RCA datasheet for the 2A3 shows max. plate dissipation of 15W but max output power of 3.5W. I don;t know what the max output of the 6080 tube is, but it's a safe bet that it's nowhere near 13W.
cheers, Derek
cheers, Derek
