More discoveries with the Mansfield bias mod.

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Riff Blister

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So, last night I decided to try playing my Tele through my recently modded Stiletto.
Good lord did it ever sound good. I couldn't believe it.
Previously, I didn't like the way that guitar and my Strat (single coils in general) sounded with it. At least on any of the gain modes.
I think I only took my Strat once to a gig and I only used it with the Fat Clean mode for the few mellower songs that we played that night.
The more I use this amp now the more I appreciate the mod.
 
what do you think the mod has done for the fat clean channel?
 
I still haven't had a chance to play with the band. I'm not sure there is a band anymore! But I have played a couple of single coil guitars throught the Deuce since doing the mod. My Strat with Van Zandt Rock pickups was just too bright and sparkly. It reminded me of what I didn't like about the amp before I modded it. But when I switched to the inbetween pickup sounds things started to get nice again. I have a couple of guitars with Tom Anderson pickups. These are my faves. The Koa bodied guitar sounds fabulous (it always does) and I particularly like the split combined pickup settings. I recently put a pair of Andersons in my Jackson SLATQM which is a mahogany guitar. The bridge is an H3+. This is the killer wood/pickup combo in my opinion. Not only through the Deuce, but the Mark V and Marshall as well. Having said all this, Fat Clean for me has always sounded a bit muffled. At home I can use Tight Clean, but live I use the Tweed setting and back the volume off a bit for cleaner sounds. The Mod definitely dirtied up the clean channel in all 3 modes and it is now much easier to get them to break up. I suppose that was inevitable given how much hotter the valves are now running. One thing I did notice the first couple of times I played through the amp after doing the mod was that I got that 'Cooking' smell. As if the amp had just been used for the first time. Now that it has been used a few times, that doesn't happen.
 
At the risk of overstating my position...the Stiletto (my Stiletto Deuce Stage 1) before the bias mod was a dissapointment. It sounded cold, harsh, flat, jagged, thin and 'piercing'. I could tell that the brit 'voicing' was there...but it just wasn't making it through to the final sound level of the output stage.

I never expected super-cleans (or wanted them) in an EL-34 based amp. Fact; I was looking for an approximation of the EL-34 Brit tone my favorite amps of past years had...with the addition of the quality of Mesa construction, and the special 'new-fangled' features such as 'solo-boost', 'channel asignable power-level', 'channel assignable rectification', 'tweed/full-power variac', and multiple channel voicings.

SOUND OF TRUMPETS PLEASE...the new emporer has arrived.

That's what I sought and expexted with the Stiletto. That's NOT what I got initially.

Since installing the Mansfiels 'bias-mod'...that's what I now have! It sounds absolutely stunning with single-coils AND humbuckers. I sold my collectable JCM800 100-watt, channel switcher shortly after the Mansfield mod to my Stiletto. I can tweak my way to every tone the JCM ever offered; plus many more.

My only sore point is not the amp; but the places I play regularly. The Lonestar fits the venues better...but I pull out the Stiletto every chance I get. Absolutely delighted with it now.

Charles
 
I am basically in agreement with everything Charles says. Mine is also a Stage 1 Deuce. I unfortunately don't have the luxury or the need to keep both the Mark V and the Deuce. I also have a Marshall that I bought new 30 years ago and could never sell. So something has to go. I put the Mark on ebay, but got every idiot in the country explaining to me why it was too expensive. I also put a bunch of my guitars up for sale, but they are all Lefties, so difficult to get a buyer there. So inevitably I have to offer the Stiletto in an effort to reduce the amount of equipment I have sitting around the house just in case a band in need of a guitarist suddenly appears in the desolate musical abyss known as West Somerset. I listed it in the Boogie Classifieds and it is also on ebay UK.
 
thanks for the input guys! When I first got my ace I was puzzled why the level from clean to gain channel would drop drastically and I would not use the clean setting just use the crunch with very little gain. I recently re-tubed and wa la my clean channels are usable. I agree with Trev that the fat clean is a little dull and I was wondering if the mansfeild mod helped in that regard. When I bought my ace I was going a different direction and for the project I'm doing now this amp is probably not the right fit but I really really like it! Also want to say thanks to all for the great info on here. this is my first tube amp and Im learning a ton.
 
I would really like to check out this mod. I'm nervous though about voiding my warranty. Also, I'm not confident enough to do the repairs myself. So, I would definitely let a pro perform the mod, and teach me how to replace/bias the new tubes.

It's a great head as is, but I do agree that the EL34s could run hotter/sweeter.
 
Hi everybody, hope you can help me ..

I also have the Mansfield bias mod, but first before installing the mod, I was measuring with the Mansfield bias probe how 'cold' my amp was. What I found out was weird.

Clean modes (fat clean, tite clean) are stock biassed much higher then the overdrive modes, so In what mode have you set your amp when biassing with the Mansfield bias mod? (I don't want to blow my amp)

For example: with fat clean & tite clean I measure about 38 to 42 mA (depending on what tubes I installed)
and when I switch to channel 2, I measure about 30 to 31 mA. Much lowerer!!

I have the bias mod, and I really want to install it, but I'd like to know who also has experienced this, and how (in what mode) have you biassed your Stiletto, and how hot is it set ?

When I switch to tube rectification, It even gets lower --> about 18 mA.

Ps: I am for sure I measured it the right, because I've emaild John Mansfield himself, showing a photo from my amp hooked up to the bias probe etc. I've connected everything like John / the manual said.

Hope you can help me!! Thanks in advance!
 
alie123:

That's certainly some interesting results you got with your bias measurements! I'm interested in what tubes you had in the amp with the different measurements you recorded? (Mesa...what color?...after-market?)

I did my biasing on the settings (i.e. modes) which I will use. On channel-1; I only use the 'crunch' mode. On channel-2; I use either the other 'crunch'-mode or usually the 'tite-gain' mode. So for me the results were not a problem...and I never even checked out how the bias would play out on other modes.

It does present a dilema to those wishing to use the particular modes you prefer...however; it does not negate any benefit you might achieve by installing and using the 'bias-mod' to tailor your sound. You will just need to keep in mind at all times the differences you discovered between the various modes.

It would seem that if you are getting 38-42 on your clean modes...that you 'are-there' in the warm/hot range for those modes...but your 2nd channel IS runnung a 'tad-cold'.

It IS NORMAL for the bias readings to drop dramatically when engaging either spongy or switching to tube rectification. Since the rectification is channel assignable (tube or diodes)...perhaps you might try adjusting the channel-2 bias to 39 (on diode rectification) while setting channel-1 to (tube rectification). When you have channel-2 adjusted...take a reading on channel-1. With channel-2 set at 39mv...channel-1 would likely 'jump' up to about 52mv assuming BOTH channels were set for diode rectification...BUT...by having channel-1 set for tube rectification; you might find that the reading falls into the mid 30's range (very acceptable for clean modes).

Am I making sense...or making myself clear?

I'll repeat: With bias-kit installed....set channel-1 on tube rectification...set channel-2 on diode rectification. Now bias the amp with channel-2 engaged and adjust to about 39-40mv(ma) with probe. Now take a reading with channel-1 engaged. If it falls anywhere in lower mid 30's to high 30's...it should sound fine.

Hope this helps: Charles
 
Charles Reeder said:
alie123:

That's certainly some interesting results you got with your bias measurements! I'm interested in what tubes you had in the amp with the different measurements you recorded? (Mesa...what color?...after-market?)

I did my biasing on the settings (i.e. modes) which I will use. On channel-1; I only use the 'crunch' mode. On channel-2; I use either the other 'crunch'-mode or usually the 'tite-gain' mode. So for me the results were not a problem...and I never even checked out how the bias would play out on other modes.

It does present a dilema to those wishing to use the particular modes you prefer...however; it does not negate any benefit you might achieve by installing and using the 'bias-mod' to tailor your sound. You will just need to keep in mind at all times the differences you discovered between the various modes.

It would seem that if you are getting 38-42 on your clean modes...that you 'are-there' in the warm/hot range for those modes...but your 2nd channel IS runnung a 'tad-cold'.

It IS NORMAL for the bias readings to drop dramatically when engaging either spongy or switching to tube rectification. Since the rectification is channel assignable (tube or diodes)...perhaps you might try adjusting the channel-2 bias to 39 (on diode rectification) while setting channel-1 to (tube rectification). When you have channel-2 adjusted...take a reading on channel-1. With channel-2 set at 39mv...channel-1 would likely 'jump' up to about 52mv assuming BOTH channels were set for diode rectification...BUT...by having channel-1 set for tube rectification; you might find that the reading falls into the mid 30's range (very acceptable for clean modes).

Am I making sense...or making myself clear?

I'll repeat: With bias-kit installed....set channel-1 on tube rectification...set channel-2 on diode rectification. Now bias the amp with channel-2 engaged and adjust to about 39-40mv(ma) with probe. Now take a reading with channel-1 engaged. If it falls anywhere in lower mid 30's to high 30's...it should sound fine.

Hope this helps: Charles

Charles,

what channel was your amp set at when u biased it up to 39 mv?
 
Wow, thanks Charles! Your idea makes sense to me, indeed.
Good plan.

I've tried different tubes. These measurements were done with GT-EL34LS tubes (groove tubes) Rating 6 --> hot. Mesa 'accepts' Groove tubes in the ranges 3 to 6 or 7 If I'm right.. (can't remember exactly)

This were my measurements, all on BOLD power.
Channel1 - mode fat clean : 0,042 (diode)
Channel1 - mode tite clean : 0,041 (diode)
Channel1 - mode crunch : 0,031 / 0,032 (!!!!) --> This mode sounds incredible THIN/ICE picky / (diode)
Channel2 - mode crunch: 0,031 (also) (diode)
Channel2 - mode tite gain :0,031 (also) (diode)
Channel2 - mode fluid drive : 0,031 (also) (diode)

With tube rectificatin selected in the channel2, it was 0,018 mA -->this is very very low, isn't it?
Can't remember the tube rectification on channel one. :-( I have to measure again :)

I can set channel one on tube, and channel2 on diode, and bias my amp that way.
But what if I (or someone) switch over to channel one, diode setting?

Will my amp go up in flames, or will it blow? or is there a kind of security built-in so the amp can't go too hot? ?

Tonight I'm going to measure the tube setting on my clean channel!
 
I've found the papers where I wrote down some measurements with different tubes (SED winged C's. I wanted the measurements with the GT tubes, as described in my previous post, but I cannot do measurements at this time, because at this moment my amp is in the practise room of our band.

So, with the Winged C tubes (SED) I have other values offcourse, because the tubes aren't as hot as the GT's,

ch.1. fat clean - 38mA (diode) 21 / 22 mA (tube)
ch.1. tite clean - (same as above)
ch.1. crunch - 30 mA (diode) and 16 mA (tube)

ch2. all modes 30 mA on diode and 16 on tube.

Hope Charles, and all other amp guru´s have good tips and advice for me, !
thanks in advance!
 
I biased my Stiletto Stage 1 with the amp set at 50 watts; Crunch-Mode; Diode Rectification. I set it to 39ma. Noticed no difference on CHannel-2...Crunch or Tite Gain. Setting either channel to 100 watts; very slightly lowers the bias numbers for that channel.

Wouldn't want anyone to change my rectification from tube to diode on a fairly hot biased amp...but a few minutes play would more than likely only contribute to more rapid tube 'retirement'...not massive meltdown. Tell folks to keep their paws off your knobs and switches.

"Don't mess with my toot-toot! Don't mess with my toot-toot!"

As to this thread being useless without 'clips'....Well; I certainly hope someone with the means to post them who has done the Mansfield (or any other) 'Bias-Mod'...will feel motivated to post some clips, for those who need them.

However; the people who most seem to want (or need) this 'mod' seem to intuitively understand the differences pre-and-post-mod without the necessity of clips. Invariably; they had a particular 'sound-in their-heads' which was not being achieved pre-mod; and the descriptive language of the 'modders' swayed them.

Also; I have never gained any useful info from clips. This due to the low general quality (in my opinion) of the limitations of compressing a guitar signal into a playable recording over little speakers etc. Also; there are just WAY-TOO many variables at work as to the the rest of the equipment as well as the guitarist's intent, taste, style, as well as ability. Far too many variables for me to make a decision based on a clip.

Having said that; however; I am either crazy enough; or a big enough hypocrite to have initially purchased both my 1st Lonestar and my Stiletto NEVER having heard either one! So lambast my remarks on 'clips' if you will! I'll not tale humbrage!

I DO HOPE someone with the means WILL post some clips!

Charles
 
Charles Reeder said:
I biased my Stiletto Stage 1 with the amp set at 50 watts; Crunch-Mode; Diode Rectification. I set it to 39ma. Noticed no difference on CHannel-2...Crunch or Tite Gain. Setting either channel to 100 watts; very slightly lowers the bias numbers for that channel.


Charles

hmm interesting, according to this, and the data that Allie provided in the previous post, it seems that if you primarily run your amp in Channel 1 "Crunch" mode, and Channel 2 "tite gain" mode (both in diode), you will have no issues with the bias. However, if you flip your Channel 1 to "fat clean mode" you will likely be running your amp too hot. Have you ran your amp in this mode Charles? and if so, how does it sound?

My main issue now is that I like to run Channel 1 in "fat clean" mode and Channel 2 in "tite gain" mode, both in diode. Running it like this seems to have issues with a stable bias so it seems if you want to run your amp like this, you need to pick a middle ground bias, compensating for both channels. strange.
additional thoughts?

I'm planning on picking up a meter soon so I can measure my stock bias settings. I'll post them hopefully soon when I can.
 
alie123 said:
I've found the papers where I wrote down some measurements with different tubes (SED winged C's. I wanted the measurements with the GT tubes, as described in my previous post, but I cannot do measurements at this time, because at this moment my amp is in the practise room of our band.

So, with the Winged C tubes (SED) I have other values offcourse, because the tubes aren't as hot as the GT's,

ch.1. fat clean - 38mA (diode) 21 / 22 mA (tube)
ch.1. tite clean - (same as above)
ch.1. crunch - 30 mA (diode) and 16 mA (tube)

ch2. all modes 30 mA on diode and 16 on tube.

Hope Charles, and all other amp guru´s have good tips and advice for me, !
thanks in advance!


Alie, which of the two tubes (GT or SEDs) sound better to you?
 
Interesting indeed,

Biassing on channel 2 is a good plan if you leave channel 1 in crunch mode. But, like the question from inkwachemis, what if you like to have your 1st channel in clean mode. I'm really interested in this one..

Or maybe, I bias on channel2 - with diode rectifier, for having the best crunch/overdrive tones coming from channel2, and then you'll also have automatically the channel1-crunch mode also at the right bias. Then, if you want clean tones, you can select FAT or TITE clean mode, switch back to TUBE rectifier. Then your bias will be too low, i guess... But will clean 'tones' biassed too low also results in a horrible sound, or will this be useable ? Are clean tones less 'sensitive' for inproper bias setting ?

About the question from inkwachemis about which tubes I liked better.. I don't know. The GT tubes add a bit more warmth and added more bass in the sound. Because the ACE sounds very shrill/thin, these tubes are (in my opinion) at this moment the best choice, but I think that's mostly because the added bass makes my 'think' the sound is fuller and less shrill, but the shrill sound is still there, ..and I do not care for the extra added bass in the sound. I use this tube in my ACE now, but, .. Let my say, .. after I have installed the bias kit, I can use all types of EL34 tubes, and the first tube set I will bias, and use, are the SED tubes. I think they are very good... Also, reviews of this tube are good in general.

Maybe I will install the bias mod today or tomorrow, depending on the advices / ideas on the board :)
 
hi Everybode,

Wanted to let you know that today I installed the bias mod.
I biassed channel 2 at 39 mA. I have tested my amp at home, so not very loud, but the amp seems to be improved. Channel2 is still bright, but not harsh anymore, in my opinon. Cleans on channel 1 are also accaptable.

I biassed channel2 at 39 mA, on diode setting
When switching to tube, I´m at about 23 mA

Clean is at 29 mA with tube rectifier. When switching to diode, I´m around 49 mA.
When playing on diode on channel1, I think I like the sound a bit more, but 49 is too high I think.. The manual from Mansfield says not go above 85%

My baseplate voltage is around 470 V
So: when I compute: 25/470 * .85 = 45 mA maximum..
But I'm at about 49 mA. Can I use this mode, or will I blow my amp ?

At thursday evening, I will practise/jam with my band. I'll take my ACE with me, and Ill lete you know how it goes. If I have some time, maybe I can make a video from my amp at home, but like Charles wrote .. You have a little little bit an idea of how it sounds.
 
I just want to point out with the bias settings, nothing is really etched in stone. Most agree that somewhere around 85% is max. Alot of people won't go over 70%. The point is if running a little hotter sounds better to you and your tubes are not redplating then you should be ok. It would only shorten the life of the tubes some. The main thing is to make sure none of your tubes are glowing red. That would mean it's too hot. Thanks to all for being such a big help here. When Alie was emailing me his questions I referred him here since I didn't have a Stiletto in front of me to test readings. I knew he would get knowledgable answers to all of his questions. I have been monitoring this thread from the start and even learned some myself.

Thanks
John
 
Indeed, Thanks John. Then I'll keep it the way it's biassed now. I'm so curious how my Stiletto will sound tomorrow at loud volumes!!! I can't wait.. I have had patience for 2,5 years almost, so .. now it's time for good results finally.!!

Yes John, I'm lucky there are nice guys all around the Boogie board that also can give me some good tips and advices. That's the power of sharing info to each other. That's why I also post all the information I have on the board. Thanks for your service and advices also!
 

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