More discoveries with the Mansfield bias mod.

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Riff Blister
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More discoveries with the Mansfield bias mod.

Post by Riff Blister » Fri Sep 10, 2010 3:10 pm

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.
Stiletto Deuce II, with bias mod - 2x12 Recto Cabt. Scumback M75s inside
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dmain
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Re: More discoveries with the Mansfield bias mod.

Post by dmain » Sun Sep 12, 2010 1:18 pm

what do you think the mod has done for the fat clean channel?
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Trev57
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Re: More discoveries with the Mansfield bias mod.

Post by Trev57 » Mon Sep 13, 2010 2:31 am

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.
Last edited by Trev57 on Thu Sep 16, 2010 2:16 am, edited 1 time in total.

Charles Reeder
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Re: More discoveries with the Mansfield bias mod.

Post by Charles Reeder » Wed Sep 15, 2010 2:24 pm

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

Trev57
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Re: More discoveries with the Mansfield bias mod.

Post by Trev57 » Thu Sep 16, 2010 2:14 am

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.

dmain
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Re: More discoveries with the Mansfield bias mod.

Post by dmain » Thu Sep 16, 2010 11:39 am

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.
Hamer Special w/ P90's
Stiletto Ace 1x12 combo
Carvin V412 cab w/ Weber speakers
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jetdriver
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Re: More discoveries with the Mansfield bias mod.

Post by jetdriver » Sat Sep 18, 2010 9:05 am

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.
Mesa Royal Atlantic RA100
Past Boogies: 1984 Mark IIC+ short head, 1995 Dual Rec BlackFace, Stiletto Deuce II, Roadster
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alie123
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Re: More discoveries with the Mansfield bias mod.

Post by alie123 » Sun Sep 26, 2010 3:03 am

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!
Stiletto ACE, TA-15

Charles Reeder
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Re: More discoveries with the Mansfield bias mod.

Post by Charles Reeder » Tue Sep 28, 2010 1:09 pm

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

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inkwachemis
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Re: More discoveries with the Mansfield bias mod.

Post by inkwachemis » Tue Sep 28, 2010 6:23 pm

Charles Reeder wrote: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?
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alie123
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Re: More discoveries with the Mansfield bias mod.

Post by alie123 » Wed Sep 29, 2010 6:01 am

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!
Stiletto ACE, TA-15

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fbomb
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Re: More discoveries with the Mansfield bias mod.

Post by fbomb » Wed Sep 29, 2010 10:24 am

this thread is useless without clips :D
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Re: More discoveries with the Mansfield bias mod.

Post by alie123 » Wed Sep 29, 2010 2:20 pm

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!
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Charles Reeder
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Re: More discoveries with the Mansfield bias mod.

Post by Charles Reeder » Thu Sep 30, 2010 3:23 pm

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
Last edited by Charles Reeder on Fri Oct 01, 2010 3:04 pm, edited 1 time in total.

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inkwachemis
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Re: More discoveries with the Mansfield bias mod.

Post by inkwachemis » Thu Sep 30, 2010 5:31 pm

Charles Reeder wrote: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.
Mesa Stiletto Ace head
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