Points of interest.
An Integrated quad with KT88's and 6L6GC's for a stock 5150!!!!
A word about Integrated quads and a rebuttal for Roger Crimm
( I would also like the thank Roger Crimm for his endorsement of Eurotubes! Roger states on his personal website on his tech page, and I quote " Eurotubes - Don't buy tubes from this guy". Anyway, Thanks Roger! It goes to your integrity, and plenty of my customers have acknowledged this! )
Important info about using the E34L's in Triple X and JSX amps! Read here.
( You PV fanatics will want to go to the bottom of this page to
check out a PV collection )
Peavey Classic series amps.
The Classic series amps have got to be one of the best working man’s amps ever built. For a production made amp they are built well and sound great. My favorite is the 50-410 I like the quick response of the 10’s.These amps are fixed bias and use EL84 power tubes. They provide a crisp, warm tone when using tubes with a moderate natural plate current draw. If it’s a good blues tone your after then a fairly hot set of EL84’s will give a nice greasy tone with an early saturation. The drive channel is very good adding a nice smooth distortion when using good tubes. With the stock Chinese 12AX7’s or sovteks ( the new EH tubes included, as they are sovteks ) it has a nasty honk!
Peavey has started to use some of the JJ Electronic tubes and later JSX amps have been showing up with the JJ EL34's and even a few JJ ECC83S's!
If your looking
for Pawn shop treasures make sure you keep your eyes open for the discontinued
Rockmaster preamps and the coveted Classic 20
( there you go Lucky Mike! ) I have one of each of these in my collection.
The RM preamp is one of the nicest and most versatile preamps I've used for the
The Classic 20 is a gem for a small cheap combo. It's very much like the Fender Pro Jr. I recently
purchased a Weber AlNico P10N for my C20 ( I paid more for the Weber than
I paid for the C20! ) When the Weber arrived I realized it wouldn't fit!
The magnet on the P10N is huge! I had to take off the bell cover and remove
the speaker board from the amp and saw off 3/8" from the bottom of it to
drop the speaker down. Now the EL84's clear the magnet by 1/8". As for
the tone? It was very well worth the money and effort. The P10N is an excellent
speaker with a top end chime second to none. The bottom end is extended
and very tight and the breakup is oh so smooth!
Peavey Butcher, Ranger, Roadmaster, Triumph and Ultra amps.
These are all early Peavey amps that are 6L6 based and steadily progressed ending up with the Ultra and Ultra plus. These are all fixed bias amps and need warmer grades of tubes to sound good. They have plenty of gain for a classic rock and early metal styles and they are well built and roadworthy.
Peavey 5150 and 6505 amps.
The 5150 and the 6505 are the same amps and they have an insane amount of gain in the preamp section. I’m going to be very honest here and say right up front that I do not care for the 5150 heads in stock trim. The power tubes while running just under 500 plate volts are only drawing about 10 to 12 milliamps of plate current. This means the amp is producing what is called crossover distortion and can not produce a good warm clean tone to start with. It also causes the amp to be sluggish and lack dynamic response.
The 5150 combo and the Ultra combo are another story. For some reason PV got it right and although the combo amps are also fixed bias they are fixed MUCH warmer and I can supply you with power tubes that will get the bias between 38 to 42mA which is right where they belong with NO bias mod.
If you check a stock 5150 100 watt or an Ultra plus 100 watt head using an oscilloscope and a signal generator which is the classic old school method of biasing a tube amp, you can plainly see crossover distortion in the wave forms until you get to about 33 to 34 milliamps of plate current then the sine waves look perfect. I personally like them set at 40 to 42mA per tube. Now you 5150 players who have played or own the 5150 combo don't have this problem, for some reason the combo's are biased much warmer and with the correct grade of power tubes they will bias up to a very nice 38 to 40mA with no need to modify them. This is why most players who have tried both the head and the combo, like the clean tone and the combo's dynamic response better.
There are a lot of amp tech’s out there that have attended technical trade schools or have taken a couple college courses and have no real understanding of how and why vacuum tubes work. They for the most part have never read or studied any of the classic tube manuals but most of them will be very quick to say, "Bias? No, you don’t have to worry about that, it’s fixed bias." So if you’re looking for a tech to bias your amp properly and you get this answer say, "Gee thanks!" and quickly move on to the next tech because they obviously know nothing about tube amps.
In July of 1999 I retubed a 5150 for a local guy named Jeff Miesen, better known as Jeffytune on the Peavey forum. The Peavey amp forum used to be one of the only real open forums on the net, but unfortunately this changed the summer of 2001 and now if you post something that Peavey doesn't like your post will be deleted. This is unfortunate as I did enjoy this forum. Now back to that 5150. Jeff was real happy with the JJ Electronic 6L6’s and ECC83’s that we loaded his amp with, but I have to say I still didn’t care for it. I tried to convince Jeff to let one of the local tech’s I work with to bias his 5150 but he was leery and didn’t want to part with the $40.00. (He was probably saving for another Peavey amp!) A few weeks went by and I couldn’t take it any longer, I really wanted to hear for myself what a 5150 sounded like with the power tubes biased properly so I called Jeff and offered to pick up his 5150 and take it to one of my tech friends for a bias job, free of charge! Jeff said yes! Two days later I picked the amp up and brought it home. It now read about 34 to 35 mA on the plates which was just out of crossover distortion. I played his 5150 for about two hours at all different settings. I liked it! It now had a good warm clean tone and the dynamic response was much improved. I promptly called Jeff to come get his amp. After hearing it he was impressed, a total success!
In August of 2000 I decided to mod a 5150 using an idea I was going to use on a 100 watt Marshall. The mod consists of a split dual bias circuit allowing the amp to run all 6L6’s or a pair of KT88’s in the outside sockets and 6L6’s in the inside sockets or any combination of EL34’s, 6L6’s and KT88’s. I called it the 5150ex for experimental. I mounted the two bias pots on the back panel for easy access, reworked the front panel and hard wired in two milliamp meters, one for the two inner tubes and one for the two outer tubes.
I tried all of the above tube combinations at lots of different bias settings, this thing is a great test bed! My favorite combination is a pair of JJ E34L’s in the center sockets set at plate current draw of 44mA and a pair of JJ KT88’s drawing 65mA in the outer sockets. At these settings the amp makes 113 watts before any clipping. In stock trim a 5150 is well into clipping at 100 watts.
This amp gets run hard multiple times a week and has well over FOUR years on it now with NO problems what so ever.
The 5150 ex
is a beast! It also exhibits a very fat, warm clean tone. The distortion
in the clean channel alone is more than I need! The lead channel is just
simply over the top, way over the top! With it’s Zebra wood front panel
and snakeskin covering it’s not bad looking either! Just about every local
player that comes in for a retube wants to play it and I never say no because
it’s great to see and hear their reactions. The Marshall players seem to
be most impressed.
Peavey 5150 II and 6505+
The 5150 II and 6505+ are the same amps and fall into the love it or hate it category. I get calls and emails all the time from players who sold or traded their original 5150's off for the 5150 II or 6505+ and the question is always, "how do I get my 5150 II or 6505+ to have the balls my 5150 had?" Unfortunately the answer is you can't get there from here... The voicing on these amps is totally different than the original 5150 and Peavey choose to basically neuter the 5150 II. It simply does not have the low end grunt and raw sound that the original had. This is not bad, its just different and you will find plenty of players who love the 5150 II.
I'm questioned a lot as to the bias adjustment on the 5150 II and 6505+. This amp does have an adjustable bias but the available sweep is pretty narrow and the only way to get the power tubes out of crossover distortion is to lower the resistance to the circuit and once again this is a very easy mod and well worth it.
Inside the amp there is a small circuit board that has the bias trim pot mounted on it and the final bias resister which is a 12K 1/4 watt resister. All that's necessary is to replace that resister with a 6.8K 1/4 watt resister which will increase the window of available bias adjustment. A final bias setting of between 36 to 40mA of plate current per tube measured with a bias probe is a good setting. You only need to probe one tube, set the bias for it and you’re done.
The bias pot is located right next to the power tubes so if you use a short bias probe you don’t even have to remove the amp from the chassis. We have our own Eurotubes bias probes which can be used with any multimeter that will do this for 25.00
Peavey XXX , JSX and 3120 amps.
Enter the Triple X. Peavey was listening... The bias sweep on this amp can get either a quad of 6L6's or E34L's up to the proper bias level and if you really want to know what the bias is set at I would suggest you get a bias probe to check it with because the test points on the amp are measuring voltage and not plate current. I cannot stress enough how inaccurate the test points are! We just retubed a pair of JSX heads that were modded by Voodoo amps including the Mercury Magnetics VA-JSX-0 output trannys and because we get asked about the bias test points everyday we decided to document the readings for you. Running KT77's in the EL34 mode with a probe installed and the bias set to 36mA the test points measured 45 volts. Then we turned the bias down to a cold 20mA and the voltage at the test points read 48 volts. So a difference of 16 milliamps measured with a bias probe only showed a 3 volt difference at the test points!
An update 10/09/07 We just measured the bias on a XXX in the EL34 mode and with the bias set at 42 volts using the factory test points (Peavey recommends 42.5) the bias was a whopping 57mA which is over 100% of dissipation! You will burn up your tubes with all but the coldest grades of EL34's or KT77's. With the bias set to 45 volts at the factory test points the bias went way down to a very acceptable 37mA. So in this particular amp a variation of only 3 volts at the factory test points made an incredible 20mA difference in bias!!
Do NOT bias your XXX ,JSX or 3120 for any EL34 type tube including the JJ KT77's using the test points! The 55 volts that Peavey recommends at the test points for 6L6GC's is on the other hand, on the cool side but using the test points is so completely inaccurate we will not warrantee tubes to players who use the test points to bias these amps!
I just read a statement that was posted on the Peavey forum (yes, I was lurking...) and it stated that the bias on the XXX did not have enough range to get the power tubes too hot. This is not true!! There is plenty of adjustment especially in the EL34 mode to fry any tube!
Moral of the story? PLEASE do not rely on the test points to bias your amp! You will be lucky to get in the same neighborhood as the ballpark, let alone in the ballpark. These are not cheap amps and the bias is SO easy to set accurately that you owe it to yourself, your amp and your tone to do it right! There are short bias probes available on Ebay and from several other sources including our own Eurotubes bias probe for 25.00 so it's a VERY cheap tool, very accurate and very easy to use.
I have been asked by my XXX ,JSX and 3120 customers to do a bias video on these amps but it is so simple that I refer them to watching the Generic bias video I did on an 800 Marshall. The procedure is the same but when using a short bias probe you don't even have to take the amp out of the chassis. You ca see the video here, http://www.eurotubes.com/eurotubes-Generic-How-To-Bias-Video-Marshall.htm You don't need to measure the plate voltage you can simply bias EL34's, KT77's or 6L6's between 34 to 40mA. Most players like them right at 36 to 38mA.
We find more often than not that the JSX ,XXX and 3120 amps are hot in the EL34 mode and some are pretty cold in the 6L6 mode. So if you're biasing 6L6's and the bias will not get up above 34mA then adjust it down to about 20mA and put the amp in standby. Then set the bias select switch to the EL34 mode. YES YOU READ RIGHT! I said to put the bias switch into the EL34 mode if the bias will not exceed 34mA with 6L6's, or if you just want to run a little higher up to about 40mA. Then switch the amp back into the play mode and the bias will jump up from about 20mA to about 35mA and you will have plenty of adjustment to get even the coldest 6L6's biased properly. This is completely safe to do. Now for all you guys who do this and then ask us if you should switch back to the 6L6 mode the answer is NO, NO, NO!!! If you bias 6L6's in the EL34 mode then you MUST leave the amp in the EL34 mode.
The bias pot is located right next to the power tubes so if you use a short bias probe you don’t even have to remove the amp from the chassis. We have our own Eurotubes bias probes which can be used with any multimeter that will do this for 25.00 Here is a pic of a probe in one of the sockets of a XXX that shows the bias trim pot and selector.
The XXX, 3120 and JSX amps are quite similar with the JSX having a stronger mid and voiced differently in the high end. The XXX has the damping feature on the rear panel but we have found that the tight and medium settings are pretty useless for a big full sound, so you guys that have never tried the loose setting you should give it a shot. As far as the bias goes they are the same. As I mentioned above we had a pair of Voodoo modded JSX heads in (pictured below) and the difference seemed to be that they were a little tighter in general than a stock JSX and the definition was better in the mid and upper mid range which is what we expected from the Mercury Magnetics output tranny compared to the stock unit. The overall difference was subtle but noticeable over a stock JSX. The KT77's really shine in both the XXX and the JSX amps filling in the low end nicely while supplying a rich and harmonically complex mid. With standard EL34's these amps lack the low end that most players want now days.
We do get a lot of calls from JSX owners who are disappointed in the amp because they are playing scooped mid metal style so if you fall into this category then I recommend switching over to the JJ 6L6GC's for power because they have a bigger low end than EL34's and even more low end than the JJ KT77's and the mids are not as pushed.
Peavey Valve King
The Valve King series amps are a cheaply made chinese amp but they do fill a void for players who want to get into a high gain amp for cheap. None of my VK customers have reported problems with them and we get a lot of positive comments about the improvements with the JJ 6L6GC's and the ECC83S preamp tubes. If you're moving up from a solid state amp to a tube amp then the VK is a nice stepping stone on your way up.
If you're considering one of these amps I recommend playing one first and while you're at it, play a B52 AT100.
OK PV fans here is a picture of a guitar collection of an internet buddy and customer of mine that I've know for a number of years. You PV forum guys ( I miss you ) will know him as PVholic. I thought this needed to be posted simply because, well you'll see.
You know the old saying "Birds of a feather?" Well here's proof. This PV collection is owned by Ed Taylor who is ( yup, you guessed it ) a good friend of Charlie, alias Mr. PVholic.