The Steel Guitar Forum

I just bought a 1970 twin from Darvin that has been blackfaced (see amps and accessories topic). I don't have the amp yet but would like to know a little more about the differences between the various models. I know the blackface twins ('63-'67) are rated at 85 watts, the early silverface twins ('68 to '72) at 100 watts, and the later twins at 135 watts, yet they all have the same basic tube configuration. Is it because the the plate voltages were increased or some other changes? I'm trying to learn more about tube amps and how these power increases were achieved. Thanks, Chuck

Chuck,

You pretty much have it nailed. The AB763, AA769 & AA270 TRs ran a plate voltage of 460 (85w), the master volume Twins boosted this to 470v (100w) and the 135w ultra linear Twin at 520v.

The 100 watt Twin appeared in 1972 with the master volume feature. There where other changes made during the BF to SF years but these amps remained pretty much the same untill the UL models of 1976.

Chuck, for what it's worth, I have a '68 Twin (first year Silverface but still pretty close to the Blackface circuit) that is rated for 85w. An amp tech tested my amp as putting out more like 70w. He told me that the transformers Fenders used were all over the place on what they actually put out. He said that he liked the sound of what he called the low output transformers. I have pretty standard tubes in it. Anyway, my low output Twin is plenty loud and sounds great.

Thanks guys. I'm anxiously awaiting my first twin equipped with a single 15" JBL. It should be sweet!

http://www.ampwares.com/amp.asp?id=114

http://www.ampwares.com/amp.asp?id=113

Chuck,

You will be a happy man when you get it. I have a '65 Twin with a 15" JBL that I used for fiddle for over 20 years. I don't think I ever ran the volume over 3, and I played big rooms with loud bands. This amp also sounds killer with my old Tele and my Shobud. It's the best all around amp I've ever seen. I've even used it to drive bass cabs and PA mains in a pinch, and was amazed at how well it performed.

Enjoy!

One thing to keep in mind, just as info, is that Twins are designed to "see" two 12" speakers in parallel. That's a 4 ohm load. The single 15" JBL that's been put in your Twin is more than likely 8 ohms. But that's OK.

I bought an early silver face twin in approx. 1967.
I ordered it with factory installed JBL speakers.
In fact, it came with the JBL emblem on the front.
It really is a hernia special but love the tone.

great amp, great purchase.

Twins were 85 watts all the way up to 71,( no MV )

72 up to around 76/77 100 watts (MV, no boost )

77 to 82 /135 watts, these had the non linear output transformers, MV and Boost.

There is a lot of excellent information floating around the web, start here.

http://www.ampwares.com/

Bottom line, 85 watts, 100 watts, 135 watts( with boost) they are all great amps. There is no looking or going back after acquiring a Fender Twin Reverb. Now, that being said, some prefer different speakers as there is so much variation of tone from various speakers. but the amp, the chassis, is what it's all about. Don't ever sell it, have it rebuilt again in 10 or 15 years and it will go another decade or two , then repeat again !

I have come to the opinion that the Fender Twin Reverb is the best combo amp ever made ! For every person that says it weighs too much there are two waiting to find one to buy !

t

Tony Prior wrote:
I have come to the opinion that the Fender Twin Reverb is the best combo amp ever made ! For every person that says it weighs too much there are two waiting to find one to buy !

t

Surely it is the most rented one by backline companies!! My best sounding rig for underarm guitar....two silverface twins with EVs in them. heavy as lead, but what a sound with my big gibson arch top in a B3 trio!!

My fav now is the super reverb.

Tony, my '71 twin is 100 watts--stamped on the back. 100 watt twins were from '68-'76, according to the ampwares link in your above post. Also, my '75 vibrosonic(100 watts) has a pull-boost master volume, and it's stock. Don't mean to argue, but-----------

James Morehead wrote:Tony, my '71 twin is 100 watts--stamped on the back. 100 watt twins were from '68-'76, according to the ampwares link in your above post. Also, my '75 vibrosonic(100 watts) has a pull-boost master volume, and it's stock. Don't mean to argue, but-----------

James, my 71 Twin also states 100 watts,it's wrong. Here is the page from the Fender Amp reference book, feel free to read the section on Twin reverbs. Twins are 85 watts thru 71, after 71, maybe 72..( cross over year ) up to and around 76 or 77 they are 100watts( MV amps) after that the non linear transformer models with BOOST took it up to 135 watts. Is it possible some of the mid 70 dates are not all accurate ? of course, but not for the NON MV amps...they are all very similar... MV models are what differentiate the 85 watts vs 100 watts. Non Linear transformer models differentiate 100 watts vs 135 watts, with pull BOOST. I didn't invent this, I am reading it.

The ampwares info with regard to 68 thru 77 is wrong, they flew right by the MV upgrade of 1972.

The image below is from the Fender Amp field guide, best $10 you can spend

Discussing a Vibrosonic has nothing to do with pre MV Twin reverbs, different amp, different deal all together. Totally different time lines. I have put the Vibrosonic info up as well, this amp was developed in 72, MV Twins were being built at this time, so..100watts...


Fender was in flux, making all sorts of changes , getting ready for new models, using the same parts for different era amps...They started the big changes by adding MV to the amps to compete with the overdrive amps of the 70's.

MV amps are 100 watts, NON MV TWINS are 85 watts, my 70 Twin said 85 watts ! My 71 rear panel says 100 watts..it's wrong, they are identical amps. Dual Showman Reverbs are listed as 100 watts,( TFL 5000 ) that's probably where the rear panels came from, my 71 DSR has 100 watt rear panel, that's probably why they used the same rear panel for the 71 Twin, one panel fits all. Nobody would notice until the invention of the internet !


glad to help !

t

Tony, Not much help--pretty confusing. Non master volume had little to do with 100 watts vs. 85 watts and is not a reliable way to determine wattage. The WATTAGE STAMPED ON THE BACK OF THE CHASSIS IS FAR MORE RELIABLE, in my experience. I don't know but what I read in the ampwares link we both put up as a reference, and the techs who have worked on my amps through the years have confirmed, so I take the field guide as the most reliable I've seen as of yet.

First off, the stamp on the back of the chassis is subjective to begin with---an amp with 85 watt stamped on the back chassis will yield approximately 65 watts "true output" and a 100 watt amp gives up about 85 watts true output. And depends on how it's measured-by what system. But this is not really what this thead is about anyways.

But the Ampwares field guide shows definately '68-'76 are 100 watt amps. They also say the blackfaced Twin Reverbs were from '63-'67, and are stated as 85 WATTS. http://www.ampwares.com/amp.asp?id=113 Perhaps, a few 85 watt chassis were used up past '68? Could be. Those green sheets you posted are very vague. For instance, the one you posted for the Vibrosonic is even mispelled as vibrAsonic mispelling it's own title, leading to confusion. (VibrAsonic and vibrOsonic are two different amps) One thing it does say, is that the vibrOsonic is nothing more than a twin with a 15" speaker. The green sheet you posted does not even TELL you that it has an 8 ohm output tranny, which IS the only difference between it and a twin, besides the speaker configuration, only to vary with year models, that went to ultralinear transformer(not "non linear, as you stated) in 1977.

The only difference in the Dual Showman Reverb, The Super Six, Quad Reverb and the Twin Reverb, is the faceplate, and the cabinet/speaker configuration for these one and the same chassis. Bias control changed through the years, too, other than that, these amps were pretty much the same chassis in a different wrapper.


The vibrosonic had the added difference of an 8 ohm transformer. Seems the facts are fuzzy when the pull boost apeared. My '75 vibro. has a pull boost. My '75 twin I had, the master volume did not pull boost. Go fgger. I think accuracy is important here. I stand by what I say, not trying to be controversial, but accuracy is important.

ok



here's an interesting read from wilkipedia with regard to BF and SF Twins.., very interesting is the last line !

http://en.wikipedia.org/wiki/Fender_Twin


----------------------------------------------

The rating of the amplifier's output power was also upgraded to 100 watts. Fender factory schematics show slightly higher voltage on the output tube plates when compared to the older AB763 circuit. Some say that this accounts for the higher output power. The power transformer part numbers for the AB763 and the later circuit designs are identical, being part number 022756 (125P34A); the specification of that part number did not change. The transformer output is rated at 640vCT at 450ma when its primary receives a 117v input. Other parts of the power supply are essentially the same, so some mystery surrounds the increase in power. One possible answer is voltage delivered to the amplifier from the wall plug. In North America, wall outlet power is considered to be 117V nominal, plus or minus 10 percent. Fender may have originally rated the amplifiers when plugged into the voltage available at their factory, which may have been as low as 105V. Maximum operating voltage would be about 127V. CBS might have decided to rate the amplifier's power at maximum input voltage, thus gaining an "upgrade" with no change, and at no cost whatsoever !

-----------------------------------------------------

Ok, here, this confirms what I said, from Wikipedia:
the Twin-Amp was replaced with the Twin Reverb-Amp in 1963.

[edit] Fender Twin Reverb
The Fender Twin Reverb is an all-tube guitar amplifier with two 12", 8 ohm speakers made by various suppliers. The more common speakers found in Fender Twin Reverbs include Jensen C12Ns, Oxford 12T6s, JBL D-120Fs (an upgrade at the factory), Utahs and, in later years, CTS and Eminence models. Some Twins were fitted with EVM 12L variant speakers known as EVM 12Fs. Unlike most Electrovoice speakers, they were fitted with metal dustcovers like the JBL D-120Fs. The Twin Reverb is frequently shortened in conversation to 'Fender Twin' or simply 'Twin', though it shouldn't be confused with the Tweed or Blonde era Twin amplifiers which had vastly different circuits and no reverb. The Fender Twin Reverb is considered a standard model for players seeking a clean sound, and it is especially known for the quality of its built-in spring reverb. All Twin Reverbs feature a solid state rectifier.

[edit] Blackface
The Twin Reverb was first introduced during the Blackface era of Fender amplifiers which was from 1963-1967. During this time the amplifier's output was rated at 85 watts into a 4ohm speaker load.

The so-called blackface amplifiers have black faceplates, black tolex covering on the cabinet, and neutral to slightly amber tinted silver sparkle grill cloth with a small ribbed rectangular pattern.

Twin Reverb amplifiers came standard with "tilt back legs" which allowed the amplifier to be tilted at an angle backwards, so the speakers faced at a more upward angle, promoting better distribution of their output to an audience when placed on a low stage.

The circuit used is commonly known as the AB763 circuit. Fender Twin Reverb amplifiers use four output tubes, of the 6L6GC type. They use six preamp tubes, consisting of four 7025/12AX7 types and two 12AT7 types. The 7025 is a lower noise version of the 12AX7.

The Fender Twin Reverb has two independent channels, labeled Normal and Vibrato. The controls have black skirted knobs numbered from 1-10.

The Normal channel has two inputs, a "bright" switch (which compensates for loss of brightness through the volume control when the control is set lower than about "6" on its 1-10 scale), a volume control, treble, middle and bass tone controls.

The Vibrato channel has a duplication of the same controls as the normal channel, plus the addition of reverb, vibrato speed and intensity controls. Reverb is accomplished with a tube/transformer driven low impedance spring reverb tank (made by the Hammond company) or its spin-off company Accutronics.[2] The addition of the reverb circuit requires an additional "gain" stage in the preamp, and as such, the Vibrato channel is capable of a bit more distortion when the volume is set high. Vibrato (tremolo) is accomplished with what is known as a "vibrato bug" by Fender amplifier repairmen. The vibrato bug is a four wire device consisting of a neon tube and light dependent variable resistor, packaged in a short section of black tubing. It resembles a water bug, with slender wispy legs. The tube generated vibrato (Hartley) oscillator pulsates the neon light, which varies the resistance on the resistive element. That variable resistance is applied to the audio signal on the Vibrato channel, creating a pulsating increase and decrease of that channels volume. The speed controls varies the rate of the oscillator. The depth control limits the amount of application the variable resistor has on the audio signal.

The front panel also has a bright red pilot light lens (better known as "pilot lamp jewel" for its multiple triangular-shaped facets), covering the pilot light (made by the Chicago Miniature Lamp Co.). Other colour schemes (amber, white, green, purple and blue) are also available.

Rear panel controls include a 2.5 amp "slo-blo" fuse, an accessory AC outlet, an earth ground selection switch, on/off and standby switches. Additionally there are two speaker output jacks, and jacks for footswitches to activate/deactivate the reverb and vibrato effects.

The black faceplates of the "blackface" era Twin Reverb will say either "Fender Electric Instruments" (FEI) or "Fender Musical Instruments", (FMI) depending on the date of manufacture. Those units made before the CBS take over of Fender in 1965, will be marked Fender Electric Instruments, and be worth a bit more on the collectors market.

[edit] Silverface
In 1968 the Fender amplifier line switched from the original black faceplate to a new brushed aluminum faceplate with light blue labels (except the Bronco, which has red) and changed the color of the grillcloth from silver grey to silver with sparkling blue threads embedded within it, ushering in the Silverface era. Other blackface cosmetic features were retained.

The first silverface Twins used the blackface AB763 circuit until May 1968, when Fender switched to the AC568. Since the tube complement was the same, Fender just used up their stock of printed tube charts saying AB763 until they ran out. Thus many silverface amps are mislabeled and this has created some confusion, causing some owners to think they have AB763 circuits when in fact they are AC568s.

The Twin Reverb, along with all other silverface models, had an aluminum frame (trim) surrounding the sparkling blue grillcloth from late 1967 to 1969. Early silverface amplifiers made between 1967 and 1968 had black lines on the brushed aluminum control plate, still retaining the '60s "tailed" design. This feature was offered on models produced prior to the "tailless" period in 1973. Some later models came with an unusual silver grillcloth with sparkling orange threads ("orange sparkle").

The rating of the amplifier's output power was also upgraded to 100 watts. Fender factory schematics show slightly higher voltage on the output tube plates when compared to the older AB763 circuit. Some say that this accounts for the higher output power. The power transformer part numbers for the AB763 and the later circuit designs are identical, being part number 022756 (125P34A); the specification of that part number did not change. The transformer output is rated at 640vCT at 450ma when its primary receives a 117v input. Other parts of the power supply are essentially the same, so some mystery surrounds the increase in power. One possible answer is voltage delivered to the amplifier from the wall plug. In North America, wall outlet power is considered to be 117V nominal, plus or minus 10 percent. Fender may have originally rated the amplifiers when plugged into the voltage available at their factory, which may have been as low as 105V. Maximum operating voltage would be about 127V. CBS might have decided to rate the amplifier's power at maximum input voltage, thus gaining an "upgrade" with no change, and at no cost whatsoever.

From about 1973 forward, a master volume with pull-boost (on a push-pull control) became a standard feature on all dual-channel silverfaced Fender models (usually known as "master volume" amps). Original master volume amps from late 1972 were made for a short time without that "pull boost" circuit on the master volume control.

Between 1977-1982 the power was increased to 135 watts. This increase was partly due to the output section being changed to the ultralinear topology, as different power transformer and power supply design resulted in much higher plate voltages. During that period CBS updated the "tailless" Fender amp logo with a new "Made in USA" script placed on the bottom side and replaced the sparkling blue grillcloth with a new silver grey grill with sparkling orange threads.

During the 1970s and to a point, the late 1960s, the American amplifier companies were all engaged in an undeclared "wattage war". Each manufacturer would rate and or produce amplifiers of increased power as a means of gaining market superiority (or the illusion thereof). American amplifier companies used a philosophy of bright clean tones and the elimination of distortion was a key design factor. Another problem facing the tube amplifiers of the day was the costly need to match the output tubes for proper balance of the circuit. Fender approached this problem with a modified output tube bias control which achieved balance at the expense of overall bias level. Between 1968 and 1973 other circuit features were used to achieve a sort of self balancing of the output, namely a combination of grid and cathode bias. All of these features were frowned upon by the musicians of that time, who generally preferred the more edgy tones of the original blackfaced amplifiers.

James it actually confirms nothing other than confusion, no facts, no detail, that's why I offered the link...

A rating change from 85 watts to 100 watts with the same chassis..that's why I linked it for all of us...

as quoted above , and correctly, this is the caveat..

CBS might have decided to rate the amplifier's power at maximum input line voltage, thus gaining an "upgrade" with no change, and at no cost whatsoever.

unquote

This is why for the past decade or so techs and those who are fanatic Fender people ( like me ) look at all NON MV chassis as 85 watts, because there was no change other than the words for marketing. If 100 watts is true then ALL Twins from 63 thru 77 are 100 watts because of the way the rating was back in the early days. I also recall growing up we called the home AC service 110ACv, now it's termed 117VAC, but nothing changed , did we actually get another 7 VAC from the electric company ?

The question is still the same, if 1963 thru 1967 chassis were rated at 85 watts and there was no change from 68 thru 77, how did they get 100 watts ? BF mods are not power related they are tone stack related. Good trick.

Easy answer, Fender was in trouble competing now with Marshall, Vox, Mesa and others...they upgraded the power rating to compete but they didn't make any change...marketing....

It doesn't much matter to me, 85 or 100, it's all the same at the end of the day, but I am an electronics tech, old school tube trained, I am still partially active but now only with older Fender amps, I see whats in front of me ,if two amps are identical, then they are identical in every way. I can't have a 1964 chassis in front of me that is basically identical to a 1970 chassis and somehow assume they are different now can I ? My Dual Showman Reverb is also rated at 100 watts, the main difference in that chassis and the early Twins is they added a 2nd bias circuit cap. So I am to assume that by adding a 2nd bias cap 15 output watts was gained to the circuit ? The fixed bias voltage remains the same.

Marketing...

Oh yeh, in 1967 the 427 Tri-power Corvette was rated at 435 HP, it was actually pushing well over 500...but GM wrote 435 so people could actually get it insured...There isn't anyone that had one of those beasts that didn't know it was well over 500 HP...Marketing...the words...


it's all good...your amps can be 100 watts, mine are 85 ! still the best combo amp ever made in my opinion and at todays prices the best amp value on the planet for those SF Twins.

t

[quote="James Morehead"]Ok, here, this confirms what I said, from Wikipedia:
the Twin-Amp was replaced with the Twin Reverb-Amp in 1963.


[edit] Blackface
The Twin Reverb was first introduced during the Blackface era of Fender amplifiers which was from 1963-1967. During this time the amplifier's output was rated at 85 watts into a 4ohm speaker load.

The circuit used is commonly known as the AB763 circuit.

The first silverface Twins used the blackface AB763 circuit until May 1968, when Fender switched to the AC568. Since the tube complement was the same,
"Fender just used up their stock of printed tube charts saying AB763 until they ran out. Thus many silverface amps are mislabeled and this has created some confusion, causing some owners to think they have AB763 circuits when in fact they are AC568s."

(Perhaps this is why you think they are all 85 watts, Tony?--NOTE: still mentions nothing about non master volume as having anything to do with or remotely related to 100 watt amps???)

THE RATING OF THE AMPLIFIER'S OUTPUT WAS ALSO UPGRADED TO 100 WATTS(1968). Fender factory schematics show slightly higher voltage on the output tube plates when compared to the older AB763 circuit. Some say that this accounts for the higher output power. The power transformer part numbers for the AB763 and the later circuit designs are identical, being part number 022756 (125P34A); the specification of that part number did not change. The transformer output is rated at 640vCT at 450ma when its primary receives a 117v input. Other parts of the power supply are essentially the same, so some mystery surrounds the increase in power. One possible answer is voltage delivered to the amplifier from the wall plug. In North America, wall outlet power is considered to be 117V nominal, plus or minus 10 percent. Fender may have originally rated the amplifiers when plugged into the voltage available at their factory, which may have been as low as 105V. Maximum operating voltage would be about 127V. CBS might have decided to rate the amplifier's power at maximum input voltage, thus gaining an "upgrade" with no change, and at no cost whatsoever.

From about 1973 forward, a master volume with pull-boost (on a push-pull control) became a standard feature on all dual-channel silverfaced Fender models (usually known as "master volume" amps). Original master volume amps from late 1972 were made for a short time without that "pull boost" circuit on the master volume control.

Between 1977-1982 the power was increased to 135 watts. This increase was partly due to the output section being changed to the ultralinear topology, as different power transformer and power supply design resulted in much higher plate voltages. During that period CBS updated the "tailless" Fender amp logo with a new "Made in USA" script placed on the bottom side and replaced the sparkling blue grillcloth with a new silver grey grill with sparkling orange threads.

Chuck, you are spot on with your opening post to your thread--you have it nailed. one thing to remember--running a 15" speaker of 8 ohms will drop in a 4 ohm amp will drop your power by about 30%, because of the mismatch. You won't hurt the amp, though.

Tony, your comment about tieing "non-master volume" to strictly 85 watts is contradictory. No where in any literature or history have I ever read once that "master-volume" ushered in the 100 watt models, or that 100 watt models were "marked" as having a master volume instead of non master volume. Sorry buddy. Your green paper you quoted is vague, and compared with reliable sources, is inaccurate--written in someones manual--definately not from Fender Company. I believe Fender Company. And let's not confuse this fact with the well known fact that 85w were a true 85w. or 100w were a true 100w--that was already stated early in this conversation as subjective. Moot point. Tony I know you feel strongly about this, but you have an assumption. The amp techs in MY past are also well qualified. I have deep respect for you, Tony.

I got better things to do than debate the obvious, so I'm out of here. Ya'll have fun! Chuck, enjoy your amp!!

It's right here, in the The Blue Book

85 watts until MV, then 100 watts, then Ultra Linear...

Wiklipeda stated there was no circuit differences with SF amps,68 thru 71) they are correct, Fender arbitrarily raised the wattage rating, it had nothing to do with AB763 vs AB568..to add an 18% output gain ( 15 watts ) would require a circuit change of some sort, of which they did not do.


My reference comes from several sources including the well used Blue Book of Guitar Amplifiers, which is what dealers use. I don't mean to argue but it appears we are arguing with the published books that dealers use ! And I use the same ones.

I also have great respect for you James, we can both go cut the lawn and those who are interested can draw there own conclusions, mine are from printed publications which are used daily.

I also know several techs who think changing caps in Fender amps should not be done unless the amp has a problem. I guess not all techs are equal ?

ok, off to the days journey, I love the debate !




page 176, Twin Reverbs

Ok, now y'all got me thinkin'........guess I need to go dig out my old Fender twin and see how many watts it is for fun! I know it sounded real nice as I replaced the two speakers with a grey basket 15" JBL years ago.
It's a 72/73 or so w/MV............I dunno

Great amp Kevin, turn it up so we can all hear it !

By the way , just as a general FYI for those who may seek to gain useless knowledge, AB763 means 2nd schematic drawing (B) July (7) 1963 , AB568 means, 2nd schematic drawing (B) May (5) 1968 . The major differences in those schematics were coupling cap changes and if memory serves me well possibly a grid resistor added. Fender was notorious for putting the AB763 tube chart /chassis labels in amp cabinets until they used them all up ! Many Twins, Band Masters, Supers etc..all had AB763 labels sometimes up to and including 68 and even 69 ! Both of my early amps , 64 Tremolux and 64 Band Master have AB763 tube chart labels just to offer some crazy perspective.


Happy 6V6/6L6 power to all...

t

I read somewhere that the rating on the back of the chassis was the recommended minimum speaker power handling capability, not the actual power output of the amp. They wanted a little margin for safety, so they made these ratings a little higher than the actual output of the amps. They all sound great for pedal steel, including the Super Twin and Super Twin Reverb at 180 watts (6 power tubes and the ultralinear transformer).

Never got over 80 watts on a rtest load out of a 100 watt Twin. I can get 100 watts on a test load with a 135 watt Twin. Considering the 6L6GC is a 30 watt tube and part of that is used for the screen grids nad not for the amps speaker power, a 135 watt rating out of 4 tubes is impossible.

but Ken you are testing in the real world, Fender rated the amps with a pencil and the highest possible rounding UP ! They probably used a 125-128 VAC source as the equation reference, whatever the max AC input that could be applied to the Xformer. Right there they can maybe get a 10 to 15% spec gain . Heck they probably used the Flux Capacitor theory for the reference !

I guess I'll sue for false advertising , I wonder if anyone is still alive that can receive a subpoena ?

Doesn't much matter, I used the 71 Twin last night and it rocked the joint....


220 , 221, whatever it takes...it's all good !

t

Forgive me, you guys with more savvy than me, or if I'm rehashing something that's already been coverered, but didn't Fender's earlier print ads say something like 85W.@.02%THD and then the later ones say 100W.@.05%THD. It looks like they were able to rate the amps higher by simply accepting more distortion. Does this even have any bearing on the discussion?

Ken Fox wrote:Never got over 80 watts on a rtest load out of a 100 watt Twin. I can get 100 watts on a test load with a 135 watt Twin. Considering the 6L6GC is a 30 watt tube and part of that is used for the screen grids nad not for the amps speaker power, a 135 watt rating out of 4 tubes is impossible.

Just out of curiosity Ken, what did you get out of the 85 watt chassis on a test load?