Peavey Bravo Mods?

Discussion in 'Other Amps' started by RickyLee, Sep 26, 2010.

  1. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    9,512
    Likes Received:
    3,007
    Location:
    Riverside CA U.S.A.
    Anyone here an expert on the Peavey's? I am looking for some mods for the Bravo to give it a bit more clarity. I am already running it through a nice closed back 2X12, so there is no speaker issues. I have decent tubes in it as well. And I am getting ready to possibly mod it to an adjustable bias. I am thinking about installing a Standby switch as well.

    But the main issue I am having with this little beast, is it does not take boost pedals up front too well. The signal gets overloaded very easy when you hit the front with anything hot including a clean signal boost pedal.

    Besides the latency/delay in the channel switching, these little amps are quite cool.

    So some clarity mods or even tone stack mods would be appreciated.
     
  2. clutch71

    clutch71 Well-Known Member

    Joined:
    Sep 26, 2007
    Messages:
    1,483
    Likes Received:
    886
    Location:
    Columbus, Ohio
    I'd try asking around on the Peavey Forum. If memory serves though only a couple of guys have modified them. I do have a schematic if you need it.

    I have used OD's with them even though I feel they do not need it (post 5 with gain pulled out and pre on 5 good to go through a 4x12) 808 RI and TS-9. Neither pedal did what you described. Remember too that it's an active EQ. The pot your turning will effect the previous pot.

    Were you aware there is an issue with the loop on those things? Plug a patch cable into the send and return and see if that helps. It's also easy to overlook cleaning the input jacks and loop jacks....

    Something just sounds off based on what your describing and I know from previous posts(and forums for that matter) that your no stranger to the guts of an amp.

    Really curious to hear your thoughts on the amp....
     
  3. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    9,512
    Likes Received:
    3,007
    Location:
    Riverside CA U.S.A.
    Thanks for the reply. Yeah, we have been over quite a few different topics at the other Forum.

    :cheers:


    Hmmm, as for the FX loop on this thing? I did not know there was an issue with it. Would you know off hand what the issue is? I have ran my delay through the loop and it seemd to be OK.

    I actually have it sounding a bit better after I figured out the strange voltage drop I was getting on the plate of the EL84 V5. Did you see my post in the Workbench section on that?

    http://www.marshallforum.com/workbench/18868-low-plate-voltage-half-output-xfmr-primary.html


    I have not found much info on these amps on the net in regards to modding them and improving the tone. I know the tonestack is active. I did see a few old posts from a different forum that had info from a member here, Joey Voltage. (Joey, you out there??!!??)

    Joey Voltage and another fella there were the very knowledgeable guys on that forum regarding Peaveys among other things. I was gonna P.M. Joey here, but he is quite busy now and taking a break from the forum.

    Yeah, one of the reasons there's probably not much modding info on these, is due to them being such a pain in the Arse to work on. Everything is crammed quite tight in there and to pull the main PCB out looks to be a pain. I get concerned about those ribbon connectors and causing interemittent problems with solder joints and such when messing with these type of amps. Unless it is broken, I do not really like to pull the PCB's out.

    I did re-work the bias circuit in this Bravo to an adjustable dual independent circuit for each EL84 though. It will allow me to run all these odd mismatched EL84's I have on hand.
     
    Last edited: Oct 8, 2010
  4. cudamax2343

    cudamax2343 Active Member

    Joined:
    Mar 14, 2009
    Messages:
    800
    Likes Received:
    75
    Location:
    Outside of Chicago
    Here is something I found on the Internet

    Product: Peavey Bravo 112
    Price Paid: UNKNOWN
    Submitted 03/10/2009 at 04:27pm by kahelle hife
    Email: kahelle_hife13 at hotmail<dot>com

    Features : No Opinion

    Sound Quality : No Opinion

    Reliability : No Opinion

    Customer Support : No Opinion

    Overall Rating : No Opinion
    somewhat somehow HC refuse to let me write review. so here goes-----..
    this is my second bravo. a 1990 grey tolexed bravo 112 with all original including tubes.

    wasnt cheap like the previous black iv bought but was worth it.

    as usually, i changed the tubes to JJs, did my footswitch mod and put in a standby switch.
    ok, it wasnt me but it was there that the previous owner installed and that got the original tubes when he bought the amp 2 years ago.
    so basically, he had the amp stock and changed the tubes and added the standby switch.

    i also changed the original reverb tank as the tank was caput, gave too low signal, changed to a laney VC-30 tank. it was better effect. also shielded the tank with aluminuim foil underneath and pack it with a black bag and screwed it down.

    comparing to the balck amp i got for like 2-3 years ago (cant remember) is that my black amp is somewhat brighter clearer more hifi sounding and not as dark and bassy as this grey one.

    why? its coz iv changed all big/small electrolitic caps on the black amp along with the choke resistor. the choke is the wirewound 390 ohm 5 watt. in other words, its the huge resistor in the bravo if anyone cares.

    this changed the overall tone of the amp WITHOUT changing the behavior and character of it. both the grey and black has some familiarities its just the black is somewhat clearer now.
    the new caps needs burning up and so im burning the amp 24 hours now while writing the review. its out of its cabinet and idling with a load box. dont worry of this process. the amp wont fail. as long as the chassis is out of the box for full aircon. the PT is not even that hot.

    i even have a workaround for having a bias adjusment mod on this amp but im not sharing it yet. basically, it ables you to use EH power tubes in the amp without redplate. i dont know why its always like this on EH tubes as i have no problems with sovteks or JJs. meaning, EH tubes takes more current bias that the other tubes and suggesting modding the amp for bias to cool down the circuit if using cheap EH tubes.

    tip: if the amp has 365dcv or more on the b+ then you know that your amp is alright. if ever you see the amp has 360dcv in the b+ like you would on EH tubes then you`ll see red plate. more B+ less bias. less b+ more bias. making it hot biased.
     
  5. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    9,512
    Likes Received:
    3,007
    Location:
    Riverside CA U.S.A.
    Thanks for that. The fella says he changed the choke resistor - but what did he change it to? Another resistor? Or did he install a choke? LOL

    I am thinking about installing a choke in mine. That would be about the simplest mod you could do to one of these amps. And I have been figuring it should have a standby switch of course.
     
  6. clutch71

    clutch71 Well-Known Member

    Joined:
    Sep 26, 2007
    Messages:
    1,483
    Likes Received:
    886
    Location:
    Columbus, Ohio
    Check out the article under Chapter 6 on the tech notes about Stand By switches.

    Personally I always thought the Bravo was kind of cool for not having a stanby switch. Most people think they are solid state when in fact they are not.

    Peavey.com :: Tech Notes
     
  7. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    9,512
    Likes Received:
    3,007
    Location:
    Riverside CA U.S.A.
    I sent you a P.M.
     
  8. john rich

    john rich New Member

    Joined:
    May 8, 2011
    Messages:
    158
    Likes Received:
    21
    Location:
    Toronto, The Great White North
    Hi RickyLee,

    I have a Peavey Bravo 112 that needs a complete retubing (still has original tubes)

    Can you share how you re-worked the bias circuit to dual independent adjustable circuit?

    I too have a few mismatched EL84's I'll like to safely use with this amp.

    Cheers
     
  9. ck516

    ck516 New Member

    Joined:
    Sep 2, 2019
    Messages:
    4
    Likes Received:
    0
    NUMBER ONE...Peavey Bravo does not need a standby switch.
    Peavey provides an “AUTOMATIC STANDBY FEATURE” on its non-standby tube amps through the use of what are called “inrush current limiters". It limits current before heat up and after. An 'automatic' standby feature, if you will. I got my first Bravo in 1992, changed to JJ EL84 tubes in 2000 and only changed the power tubes a couple years ago. So 17 years on the JJ tubes. Not bad. The Peavey feature must work well. When I was playing 5 night s a week (1992-1996), I changed the power tubes once a year, just to be safe.

    NUMBER TWO...put the reverb can in a bag. Mine has a old 1960s Accutronics tank I found that was close to the original Peavey specs. ( Long (2 Spring) tank, medium decay, 600Ω in / 2,250Ω out. Input insulated/output grounded connectors.) Mine has the "Made by Beautiful Women in Janesville, Wisconsin." sticker on it.
    NUMBER THREE...change the reverb op amp to a modern "OPA2604AP" op amp. Clarity and dynamic range are both increased because of the op amp's very fast slew rate.

    Tube changes make big difference on the Bravo. The JJ EL84 is the standard power tube. Since Dr. Z, Anderson, Aguilar and a host of other great amp makers use them as standard, why change? I have yet to find any EL84 tubes that sound better and last. I use a Tung-Sol relabled Mullard in V1 (I normally use an RCA, but with the V30 speaker, this tube sounds best). V2 is GE 12AX7 and V3 is a balanced JJ ECC83. Speaker is 1992 British-made Celestion Vintage 30.

    I was experimenting with the tone stack, but it was easier to buy a graphic EQ pedal. PLUS, the pedal allows changes for different venues, guitars, pedal boards, etc.. A big plus.

    As for bias adjustment, that is up to you. Mine sounds great, so I see no reason to make a change of dubious use to me. After all, I ONLY use matched pairs. YMMV.
     
    Last edited: Oct 9, 2019
  10. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,371
    Likes Received:
    9,779
    Location:
    US of A
    Where are the inrush current limiters in the schematic?
     
  11. ck516

    ck516 New Member

    Joined:
    Sep 2, 2019
    Messages:
    4
    Likes Received:
    0
    According to the Peavey Tube Amp Tech, they are CR5 & CR6. An "intelligent thermistor-type 'diode'". They look like blocking diodes to me.
    But as I said, I have been playing the Tolex off my Bravo for about 17 years.
    Though the EL84 tubes get hot enough to remove your fingerprints, I have never
    had any power tube problems. YMMV.
     
    Last edited: Oct 9, 2019
  12. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,371
    Likes Received:
    9,779
    Location:
    US of A
    All I see there is output stage protection. That does not act as an automatic or temporary standby nor an inrush current limiter.

    Where does Peavey state that? Is it in a manual?
     
  13. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    13,811
    Likes Received:
    7,657
    Location:
    Start the reactor... Free Mars!
    Change C4 22 uF to .068 / 1uF / 2.2 uF (the + of the cap faces pin 3)
    .068 = British more low frequency roll-off, 1uF-2.2uF = slightly increased low end compared to .068.
    This stops the subsonic low frequency over-loading over-compressed lows / cleans up the muddiness of the input.
    If you like to see what the cap change affects the lows, use this calculator:
    https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor/

    2. Change R1 150K to 100K. This reduces the gain of the first stage input.

    3. If it's still too muddy try changing R13 to 4.7K or 10K. Reduces the sensitivity of V1B.

    PVBRAVOINPUTII.png
     
    Last edited: Oct 9, 2019
  14. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    13,811
    Likes Received:
    7,657
    Location:
    Start the reactor... Free Mars!
    Next I'm going to take out C3.
    C3 is there to kill the high frequencies and therefore it's also killing the Hiss noise.
    But I would rather have the high frequencies and more hiss, than killing the hiss with a 1000pf capacitor.
    Then I'm going to listen to it and see how that sounds.
    If the highs are too hissy I can always put it back in...but since I hate this type circuit I'll just leave out C3 permanently.

    PVBRAVOINPUTiii.png
     
  15. ck516

    ck516 New Member

    Joined:
    Sep 2, 2019
    Messages:
    4
    Likes Received:
    0
    I'll tell you what, CALL Peavey. 877-732-8391.
    Argue with the Tube Amp Techs.
    Personally, I don't care what you do.
    I stopped playing in bands because of the drama. Here we go again!

    By the way:Cathode Stripping: This term does not apply to the tubes used in guitar amps. This applies to cathode ray tubes, and only under limited applications.
    From Mike Zaite, Dr. Z amps.

    How easy it is to scare folks into doing things NOT needed.
     
    Last edited: Oct 9, 2019
  16. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,371
    Likes Received:
    9,779
    Location:
    US of A
    I am not being dramatic.
    However I can tell you amplifier companies had been placing diode protection there decades before the Bravo and other Peavey amplifiers whether with a STANDBY switch or not.
     
  17. ck516

    ck516 New Member

    Joined:
    Sep 2, 2019
    Messages:
    4
    Likes Received:
    0
    Standby Switches and Folklore
    Many guitar amps (too many) include a standby switch. This is meant to let the heaters warm up before the high voltage is switched on. Old books called it 'preheating'.
    But let's get one thing straight: a standby switch does not extend the life of the valves, in fact it is more likely to reduce their useful life. The valves do not care if you switch on the heaters and HT at the same time (with a couple of exceptions explained below). Now, I know what you're thinking, "but every guitar magazine in the land says the exact opposite?" Yes, they do, but guitar magazines know next to nothing about electronics, they just repeat the same old wives' tale each year.

    If standby switches really did have magical life-extending properties then we would expect to see it mentioned from time to time in proper textbooks and valve manuals, yet such discussion is conspicuous by its absence. Indeed, some texts explicitly exclude audio valves from discussion of similar pre-heating switches (mainly with regard to radio transmitters). Despite this, promotional materials glorifying the supposed effects of standby switches are often published (always on the internet and in non-technical magazines, never in real academic work) even by well-known guitar amp manufacturers, presumably with good-but-misguided intentions. So such myths become self propagating.

    You may have heard of 'cathode stripping', which is a specious argument wheeled out by standby-switch obsessives. In its purest form, cathode stripping occurs when particles of the oxide coating are physically torn from the surface of the cathode when it is exposed to a powerful electrostatic field from the anode. This would happen if the valve is operated at saturation, without a usual space-charge of electrons to protect it. Fortunately, this effect does not exist in receiving valves, even when operated at saturation, because it requires an electric field strength of at least 4MV/m (yes, 4 million volts per metre!). No guitar amp ever comes close to this.
    Another type of cathode stripping occurs when stray gas molecules in the valve become ionised by the electron stream. The positive ions will then be accelerated towards the more negative grid and cathode. If these manage to miss the grid then they may crash into the cathode, physically damaging its surface. The proper name for this process is cathode sputtering. Sputtering is a known problem in gas tubes and transmitting valves operating at kilovolt levels, near saturation. It doesn't occur to any significant degree in ordinary audio circuits. Note that even the RCA Transmitting Tubes Technical Manual No. 4, p65, states: “Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature” [My emphasis].
    Receiving valves are the small kind used in radio receivers, i.e audio valves like those in guitar amps, in case you were wondering.
    From an article from the Valve Wizard who is an Elctronics Engineer who has written many books about building and repairing valve guitar amps.


    Maybe NOW all you panderers of wives tales can STOP obsessing over placing a standby switch in the Bravo. Even if the Peavey Tech was a douche, it still WILL NOT matter if no standby switch.
    How easily people are taken in by snake oil salesmen. It is to laugh.
    As I have said, I have NOT changed my EL84 tubes in my bravo for 17 years with the SAME set of JJs EL84 power tubes. I played every weekend, almost for that period of time.
    You now know the truth so lighten up and get on with your lives.
     
  18. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    13,811
    Likes Received:
    7,657
    Location:
    Start the reactor... Free Mars!
    :lol:
    I love the beer break (standby) switch. I will use it all the time.
    I use it for testing I use it for playing and best of all I use it for beer break! :drunk:
    I love pre-heating! :applause: I will always preheat. I treasure my preheating time.
    No I don't believe that it will shorten the life of the tube.
    The standby was introduced for guitar amps with the advent of class AB output.
    The bias voltage wants to be on, before the B+ is turned on. This reduces the surge current for the output tubes.

    If Leo Fender thought this was a good idea, it's just fine with me. I will always use it.
    And you notice how long Fender amps last? The tubes last a really long time in those amps too.
     
    Last edited: Nov 10, 2019 at 10:37 PM
  19. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    22,371
    Likes Received:
    9,779
    Location:
    US of A
    I use the STANDBY too. If it is there it aint bad to use it. As @ampmadscientist said it comes in handy for testing sometimes.
    It is not necessary at all but under circumstances as mentioned like beer break and maybe tear down it could be worthwhile because you never know what some idiot might do around your equipment. Even walking by and tripping over a speaker cable pulling it out or breaking the damn thing. That could do electrical damage to the amplifier if totally powered ON for play.

    By the way electrons are stripped from the cathode during use so the so called "cathode stripping" term means nothing.
    The term plasma is being used in another thread about Plasma Cosmology. Plasma occurs here to were free range particles of charge float and fly around in the tube bottle/envelope until they find a home. Still they are free to roam another day depending on circumstance.

    Also to note, all of this is in transmitting tube manuals as well.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice