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Post by RC on Jun 23, 2006 13:04:29 GMT -7
Myles, My Maz Jr NR shipped with a JJ ECC83S in the V-1 & V-2, Sovtek 12AX7LPS in the V-3, a pair of GT EL84S #6, and a Sovtek 5AR4. I'm getting a lot more hissing out of this amp than what I'm sure is normal and the overall tone is kind of sterile or flat and one dimensional leaning toward harsh. I've tried a lot of deferent settings and guitars this week with it and I've not found anything you could describe as creamy or smooth. I think maybe one or more of the tubes didn't like the road trip out here in the back of the FedEx truck. If you could give me some ideas about what would cause the hissing and how to wake up the tone I would really appreciate it. First we need to find what may be an offending preamp tube. Grab a known good 12AX7 and try it in each position, one position at a time. If you had hum rather than hiss then it could be an output tube that died in transit. Myles, Here's what I've got. The V-3 Sovtek 12AX7lPS is dead it doesn't light or heat up at all. I'm curious what dose the V-3 do in the Maz. I also found that the JJ ECC83S in the V-1 was hissing a lot more than the one in the V-2. |
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Post by rcrecelius on Jun 26, 2006 7:17:56 GMT -7
Myles,
I took a stab at biasing my Z28 last week. With the original tubes, the bias was about 23mv on one tube but the other was 33-34mv. I thought that might be too much of a spread so I installed the new TungSol's. These also measured different but were much closer together...I set it so that the lowest tube was at 24mv, which put the other at about 29mv.
I only had one opportunity to play the amp this weekend under less than ideal conditions(whole band running off 1 100' ext cord to power the bass rig, 6ch PA head and my amp). It sounded good until we all started playing, then it seemed to overdrive a little too soon and the low end got flabby...I dont know if that was due to my bias setting or the power situation.
When setting bias, should you try to get the lower tube in spec or the higher one? I believe 24-28 is the suggested range but with 5mv difference between the two, one of them is going to be outside of that range.
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Post by myles on Jun 26, 2006 8:22:37 GMT -7
First we need to find what may be an offending preamp tube. Grab a known good 12AX7 and try it in each position, one position at a time. If you had hum rather than hiss then it could be an output tube that died in transit. Myles, Here's what I've got. The V-3 Sovtek 12AX7lPS is dead it doesn't light or heat up at all. I'm curious what dose the V-3 do in the Maz. I also found that the JJ ECC83S in the V-1 was hissing a lot more than the one in the V-2. If the amp plays the LPS is working. They do not get that hot and the heaters are encased so you do not see many of the tubes show visible light up. V3 is the phase inverter in the NR MAZ Jr or Sr. V1 will have more background noise as it is the first gain stage and is the most critical tube. |
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Post by myles on Jun 26, 2006 8:24:48 GMT -7
Myles, I took a stab at biasing my Z28 last week. With the original tubes, the bias was about 23mv on one tube but the other was 33-34mv. I thought that might be too much of a spread so I installed the new TungSol's. These also measured different but were much closer together...I set it so that the lowest tube was at 24mv, which put the other at about 29mv. I only had one opportunity to play the amp this weekend under less than ideal conditions(whole band running off 1 100' ext cord to power the bass rig, 6ch PA head and my amp). It sounded good until we all started playing, then it seemed to overdrive a little too soon and the low end got flabby...I dont know if that was due to my bias setting or the power situation. When setting bias, should you try to get the lower tube in spec or the higher one? I believe 24-28 is the suggested range but with 5mv difference between the two, one of them is going to be outside of that range. 5mA spread statically is okay but not that good of a match at almost 20% difference. I prefer 3mA spread at the most. If you can return the tubes for a new set under warranty this would be the option I would pick. With this sort of spread there will be a bit more hum in the output section, tube wear will be faster, and you will not have the sustain and balance this amp can provide. For bias I stay at 60% - 70% on the Z-28 375 V 14 W 40% 50% 60% 70% 80% 15 19 22 26 30 |
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Post by rcrecelius on Jun 26, 2006 9:19:36 GMT -7
Myles, I took a stab at biasing my Z28 last week. With the original tubes, the bias was about 23mv on one tube but the other was 33-34mv. I thought that might be too much of a spread so I installed the new TungSol's. These also measured different but were much closer together...I set it so that the lowest tube was at 24mv, which put the other at about 29mv. I only had one opportunity to play the amp this weekend under less than ideal conditions(whole band running off 1 100' ext cord to power the bass rig, 6ch PA head and my amp). It sounded good until we all started playing, then it seemed to overdrive a little too soon and the low end got flabby...I dont know if that was due to my bias setting or the power situation. When setting bias, should you try to get the lower tube in spec or the higher one? I believe 24-28 is the suggested range but with 5mv difference between the two, one of them is going to be outside of that range. 5mA spread statically is okay but not that good of a match at almost 20% difference. I prefer 3mA spread at the most. If you can return the tubes for a new set under warranty this would be the option I would pick. With this sort of spread there will be a bit more hum in the output section, tube wear will be faster, and you will not have the sustain and balance this amp can provide. For bias I stay at 60% - 70% on the Z-28 375 V 14 W 40% 50% 60% 70% 80% 15 19 22 26 30 Thanks for the input Myles. I will check again because I did do this in a bit of a hurry. BTW...when dealing with a spread like this(be it 3 or 5) do you set to the lowest tube or the highest? Also...does the PI play a part in these readings? |
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Post by rcrecelius on Jun 26, 2006 9:22:04 GMT -7
Myles,
Can you relate your % into how it affects your tone? For example, at 60% vs 80%, what is the difference in tone/feel?
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Post by myles on Jun 26, 2006 15:48:05 GMT -7
Myles, Can you relate your % into how it affects your tone? For example, at 60% vs 80%, what is the difference in tone/feel? hotter running tubes can sound harsh. it is a balance ... think of it as you would the idle on your car. |
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Post by rcrecelius on Jun 27, 2006 7:01:48 GMT -7
Ok...I'll try again with lower settings and post my results.
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Post by mike33 on Jun 30, 2006 4:28:23 GMT -7
Myles
What's the different between the GT-12AX7-R2 and the SAG-AX7-MPI for the V5 (PI).
Is one of them actually a Sovtek 12AX7LPS?
Which one you suggest? Do they "sound" different?
Thanks
Michael
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Post by rcrecelius on Jun 30, 2006 7:44:20 GMT -7
5mA spread statically is okay but not that good of a match at almost 20% difference. I prefer 3mA spread at the most. If you can return the tubes for a new set under warranty this would be the option I would pick. With this sort of spread there will be a bit more hum in the output section, tube wear will be faster, and you will not have the sustain and balance this amp can provide. For bias I stay at 60% - 70% on the Z-28 375 V 14 W 40% 50% 60% 70% 80% 15 19 22 26 30 Thanks for the input Myles. I will check again because I did do this in a bit of a hurry. BTW...when dealing with a spread like this(be it 3 or 5) do you set to the lowest tube or the highest? Also...does the PI play a part in these readings? I have the house to myself for a couple days so yesterday I pulled the chassis and started experimenting. Im not sure what I was doing wrong the other day but now Im only seeing a 1mv spread between the two tubes...cool.  I spent probably two hours messing with the bias, then play it for a while, changed PI a few times and played some more. I think I ended up with the bias set at 23.5/24.5 with a NOS 5751 in the PI. These Tungsols have a much more "Fendery" sound than the previous tubes...the amp has much more clarity now and it retains that clarity even when dimed with a boost in front. This was a great learning experience for me...to be able to dial it in myself was a good feeling...granted, I'm not about to start changing caps/resistors but it was cool to be able to make these simple changes...kinda makes me wonder how many old amps I got rid of that would have sounded wonderful with the proper bias! FWIW...The dealer I bought this amp from said when they played it there was a tube rattling so they stuck some new power tubes in before shipping it to me...I need to look at those and see what brand they were. Heck for all I know they may not have adjusted the bias when they installed those tubes. |
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Post by myles on Jun 30, 2006 8:30:52 GMT -7
Myles What's the different between the GT-12AX7-R2 and the SAG-AX7-MPI for the V5 (PI). Is one of them actually a Sovtek 12AX7LPS? Which one you suggest? Do they "sound" different? Thanks Michael The R2 from GT is the Sovtek 12AX7LPS. The SAG-AX7-MPI can be made with a lot of different 12AX7s as long as they are curve trace matched but for the last year or so they were made using the GT-12AX7M. If you look at an R2 and M side by side you will see they have the same long plate construction. I love these in phase inverters. They are so close that I use them both. Currently GT is either out of M's or really just getting stock back up so I do not know their status on the AX7-MPI and since these come out of my own SAG lab and have not seen any M's for a while in there I am not sure what is going on with the MPIs. |
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Post by douge on Jul 2, 2006 8:50:15 GMT -7
Myles
I have a Post on the 6545 Forum about Tubes/Bias. Would you please look at it??
I also emailed you at guitaramplifierblueprinting.com about it!
Thank You Very Much
Doug
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Post by myles on Jul 2, 2006 9:59:21 GMT -7
Myles I have a Post on the 6545 Forum about Tubes/Bias. Would you please look at it?? I also emailed you at guitaramplifierblueprinting.com about it! Thank You Very Much Doug Doug, If you emailed me at GAB I may have already answered it. I will look in the 6545 post here. |
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Post by Deleted on Jul 2, 2006 12:53:12 GMT -7
Hi Myles, I have had my new 212 Maz38 NR for a couple of weeks and I am wondering what are some tube changes you would recommend? Basically I am looking to upgrade tubes where I can. I know the GT EL-84s are great so it would probably be the preamp tubes I am looking at. NOS or new it does not matter. Thanks for your time.
Arun
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Post by janinedoubly on Jul 2, 2006 19:42:15 GMT -7
Myles, how's the JJ EF806 coming along? Any new updates? The guys at New Sensor are either tight lipped or un-informed about the status.
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Post by guitarboy02451 on Jul 3, 2006 8:28:42 GMT -7
Myles, I have a question about 'ghost notes'.
On one of my non-drz amps, I'm experiencing a ghost note when I play a b on the 9th fret 3rd string. When I play that single not, I get a ghost note of an entire ocatve down. Can you please tell me what is causing this?
Thanks! pg
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Post by myles on Jul 3, 2006 9:40:43 GMT -7
Hi Myles, I have had my new 212 Maz38 NR for a couple of weeks and I am wondering what are some tube changes you would recommend? Basically I am looking to upgrade tubes where I can. I know the GT EL-84s are great so it would probably be the preamp tubes I am looking at. NOS or new it does not matter. Thanks for your time. Arun Arun, It really all boils down to personal taste on preamp tubes but in your amp it is really V1 that has the most impact. V2 to a degree and the phase inverter for the feel of the amp more than the tone. |
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Post by myles on Jul 3, 2006 9:41:53 GMT -7
Myles, how's the JJ EF806 coming along? Any new updates? The guys at New Sensor are either tight lipped or un-informed about the status. I have not received samples yet. JJ is not part of New Sensor. They are different companies. |
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Post by myles on Jul 3, 2006 9:42:46 GMT -7
Myles, I have a question about 'ghost notes'. On one of my non-drz amps, I'm experiencing a ghost note when I play a b on the 9th fret 3rd string. When I play that single not, I get a ghost note of an entire ocatve down. Can you please tell me what is causing this? Thanks! pg You did not mention the amp or the age of the amp but this is typically filter caps. |
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Post by guitarboy02451 on Jul 3, 2006 10:42:44 GMT -7
Thanks Myles. The amp is a 96 Marshall JCM 900. It was re-biased and retubed last year.
Tubes: 3 GT12AX7M / 4 GT6l6R
pg
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Post by janinedoubly on Jul 3, 2006 20:35:41 GMT -7
Myles, yeah I'm aware of that :-) That's why I'm asking you, 'cause you are informed and very gracious about letting out important information. New Sensor can be sometimes, oh how shall we say, a bit too intense on the phone, or down right rude! :-)
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Post by guitarboy02451 on Jul 4, 2006 6:26:50 GMT -7
Myles, I have a question about 'ghost notes'. On one of my non-drz amps, I'm experiencing a ghost note when I play a b on the 9th fret 3rd string. When I play that single not, I get a ghost note of an entire ocatve down. Can you please tell me what is causing this? Thanks! pg You did not mention the amp or the age of the amp but this is typically filter caps. Myles, do you know how much a technician would charge to fix the filter caps? |
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Post by Deleted on Jul 5, 2006 0:53:30 GMT -7
Hi Myles, I have had my new 212 Maz38 NR for a couple of weeks and I am wondering what are some tube changes you would recommend? Basically I am looking to upgrade tubes where I can. I know the GT EL-84s are great so it would probably be the preamp tubes I am looking at. NOS or new it does not matter. Thanks for your time. Arun Arun, It really all boils down to personal taste on preamp tubes but in your amp it is really V1 that has the most impact. V2 to a degree and the phase inverter for the feel of the amp more than the tone. Myles I guess I would want to bring more openess and clarity without losing the depth of the amp's sound. Bringing out the amps more marshally qualities might be nice as well. I am not sure what my options are in terms of which tubes will give me what, especially in the NOS world. I think the 5751 might bring more of a fender sound? Any light you can shed on this would help. Thanks, Arun |
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Post by Deleted on Jul 5, 2006 0:55:49 GMT -7
Arun, It really all boils down to personal taste on preamp tubes but in your amp it is really V1 that has the most impact. V2 to a degree and the phase inverter for the feel of the amp more than the tone. Myles I guess I would want to bring more openess and clarity without losing the depth of the amp's sound. Bringing out the amps more marshally qualities might be nice as well. I am not sure what my options are in terms of which tubes will give me what, especially in the NOS world. I think the 5751 might bring more of a fender sound? Any light you can shed on this would help me a lot. I will do some research as well but if you know of some cool tube swaps let me know.  Thanks, Arun |
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Post by DaSkip on Jul 5, 2006 7:02:53 GMT -7
Ok, here s a list of all the tubes in my MAZ Jr with Reverb.
V1 - JJ ECC83 S
V2 - JJ ECC83 S
V3 - 12AT7 stamped China
V4 - Sovtek 12AX7WB
V5 - Sovtek 12 AX7LPS
V6 - GTEL84S 6
V7 - GTEL84S 6
V8 - Sovtek 5AR4
All these tubes tested good today. I see that they vary from the original types installed in V3, V4 and V5. What difference should I detect if I go with the original type tubes? Obviously, I bought this amp used and really like it but, if can sound better I'll replace some tubes if needed.
Thanks,
Skip
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Post by myles on Jul 5, 2006 8:55:47 GMT -7
Thanks Myles. The amp is a 96 Marshall JCM 900. It was re-biased and retubed last year. Tubes: 3 GT12AX7M / 4 GT6l6R pg I'd have a tech check the caps ... those blue LCRs have about a ten year life span and you may be in that realm of cap replacement. |
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Post by myles on Jul 5, 2006 9:00:25 GMT -7
Myles, yeah I'm aware of that :-) That's why I'm asking you, 'cause you are informed and very gracious about letting out important information. New Sensor can be sometimes, oh how shall we say, a bit too intense on the phone, or down right rude! :-) I generally try to give the entire story no matter who makes what. |
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Post by myles on Jul 5, 2006 9:01:46 GMT -7
You did not mention the amp or the age of the amp but this is typically filter caps. Myles, do you know how much a technician would charge to fix the filter caps? It really varies .... it should be about an hour of labor plus the parts charge. |
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Post by myles on Jul 5, 2006 9:03:06 GMT -7
Myles I guess I would want to bring more openess and clarity without losing the depth of the amp's sound. Bringing out the amps more marshally qualities might be nice as well. I am not sure what my options are in terms of which tubes will give me what, especially in the NOS world. I think the 5751 might bring more of a fender sound? Any light you can shed on this would help me a lot. I will do some research as well but if you know of some cool tube swaps let me know. Thanks, Arun It will not make your amp sound like a Fender. It will give a bit more clean headroom. |
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Post by myles on Jul 5, 2006 9:04:16 GMT -7
Ok, here s a list of all the tubes in my MAZ Jr with Reverb. V1 - JJ ECC83 S V2 - JJ ECC83 S V3 - 12AT7 stamped China V4 - Sovtek 12AX7WB V5 - Sovtek 12 AX7LPS V6 - GTEL84S 6 V7 - GTEL84S 6 V8 - Sovtek 5AR4 All these tubes tested good today. I see that they vary from the original types installed in V3, V4 and V5. What difference should I detect if I go with the original type tubes? Obviously, I bought this amp used and really like it but, if can sound better I'll replace some tubes if needed. Thanks, Skip Is there a question here? V1 and V2 have the most impact and their choices are really personal taste. Do you want the amp brighter? darker? more headroom? Look on my website as it gives a lot of info on tube characteristics. |
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