Peavey Nanovalve Mods

the Peavey Nanovalve and Mods for it.

(If you make modifications it is at your own risk with absolutely no liability acepted by the author of this page)

This page last updated: January 2nd 2010


Nanovalve front

Thanks to all who have read this page and got in touch with me to pass on other tips and modifications for this great value little amp.   As a result of mods and updates I’ve made, I’ve rearranged this page a little to make it easier to navigate.  So follow the links below to get to the parts which interest you most.   As ever,  I welcome comment and further suggestions for this amp.


As I’m mainly playing my guitar at home,  I decided I ought to get an amp/combo which is more decibel and neighbour friendly than my 40W Pignose G40V (It’s seriously loud!).  I looked around the shops and settled on one of the new 5W all valve combos which seem to be all the rage just now. At the time, a guitar shop not too far from me was selling the Peavey Nanovalve for the unbelievable price of £49.99.  I mean………..a full valve combo for under fifty quid??   There had to be a catch,  but no, other than this being the most basic of basic valve (tube) amps there was no catch.  So I bought one. (I’ve now got two….) The Nanovalve has got an input and a volume control,  what more do you need?  An album I listened to a lot, and still keep going back to, is Layla & Other Assorted Love Songs. It was apparently recorded using small Fender Champs.  So the sounds I’ve grown up with as my ideal were produced using Strats and small valve amps.  Out of the box, I can get close to the”Layla” sounds with the Nanovalve so I’m delighted with it.  However, it is a bit rough and buzzy so it will get modified over time.  Further down this page is information about modifying it.  I’ll add photos and perhaps sound clips at some time in the future. Photo’s are easy, recordings are a bit harder to do.  the pictures below show you what one looks like – if you haven’t seen one before.    All the pictures are linked to larger images.

a sort of front view of a Nanovalve a top view of a Nanovalve

This page will give you more information about these bargain basement little combos, and, over time, will hopefully let me build up a resource for modifying them further.  At this point I’d like to thank Trev Ridney of Tipton Amplification for his help and guidance with the mods I’ve done so far.

About the Peavey Nanovalve

I like the Nanovalve a lot. It is most definitely not a sophisticated point to point wired hand-built boutique valve amp.  It’s a single input, volume control only, 1×8 5W combo with everything packed into a very small size cabinet.  Budget is the best word to describe it.  It is though, fully capable of producing what I think is good tone, and might with simple mods be capable of great tone. Having said that,  winding it, or any other 5W valve amp to get full-on valve-crunchy goodness sounds is liable to be at volumes your family and neighbours won’t appreciate.

From it’s appearance it looks like it’s something Peavey made to go along with their Windsor range as it doesn’t look like the Valve King range at all.  It’s very clearly a budget amp and I’ve no doubt that if I was using it heavily for gigging I’d run into heat dissipation problems as the valves are directly mounted upside down on the PCB, with very little space around them.   Because the whole package is so small,  with the valve protection it doesn’t look like there will be a lot of chance for air to circulate around the valves.  As you can see from the pictures, there’s not much space at all between the pcb, the front panel and the case back.

This is a view of the Nanovalve opend up.  The external jack socket and the pentode/triode switch can be seen fairly well. This view shows just how tight the gap between the top/front panel, the pcb and the bottom metal casing is.  This picture shows the off/on switch. This picture shows the other end of the Nanovalve. You can see the input jack which is directly fitted to the pcb. Another slightly different view of the Nanovalve opened up. I’ve labelled the components I’ve changed in the larger image which you can click to.

Here’s the lowdown on it as it comes out the box :


If you’re looking for a clean jazz amp, then move along, this isn’t the amp you’re looking for.  This is a rock/blues amp.  It does a great AC/DC, Thin Lizzy, Gary Moore, ZZ Top, Guns’n’Roses rock tone.   Clean – hmm, not really.   Even playing Eagles type songs with it presents a slight challenge.  However, it does clean up quite a bit if you roll off your guitars volume.  Simple! Just like the old days!   It gives a good response to both my Stratovarious and my 335.  At room levels the sounds can be crystal clear and the Strat does what it should with a valve amp. It just sings.  My 335 sounds, well, hollow and full bodied in comparison to the Strat.  Think BB King and you’re there.  The amp responds to every change in nuance of playing, pickup selection, vol control on guitar, etc. In this aspect, it seems to be more responsive than my Pignose G40V. When the Nanovalve is flat out the overdriven crunch (before any modifications) is a bit harsh. (It’s also way louder than you need for domestic use).

I think a speaker change is definitely needed to smooth this out.  The speaker in it has no identifying marks whatsoever.  I then plugged my pedalboard into it. Using my UD-Stomp as a reverb pedal the Nanovalve is even better.  It responded to the pedal very well indeed. Throwing other pedals into the chain, each one sounded better than I’d heard them before.  So I’d give this 8/10 for sounds out the box and expect to get it to 10/10 with some small and easy mods (principally a better speaker.)


I took the back cover off to look at the valves, expecting to find a couple of cheapo Chinese tubes. I was pleasantly surprised to find an Electro Harmonix 12AX7EH and a Sovtek EL84/6BQ5.  I didn’t bother to replace them as I doubt if the JJ ECC83S I had ready to replace the preamp valve will sound much different.  (see below for an intersting update! I was wrong!)  So it’s got good valves to begin with, no changes needed there. (Update – now that I’ve got two Nanovalves, I will change the 12AX7 in one of them and do some A-B comparisons)  As the valves are mounted on the PCB it’s clearly been designed to a price, rather than for the ultimate in longevity and ease of modding.


Chinese presumably. Nothing at all marked on it.  If I didn’t have the circuit diagram I wouldn’t even know it’s impedance  (8 ohms if your interested).  I think it’s rough, but I’ve not changed it yet nor have I A-B’d it.

Modifying it

OK First Off……    SAFETY!!

This is a valve amplifier and contains very high voltages.  DO NOT attempt to make any modifications unless you are sure you know what you’re doing.  Your life has got to be worth more than the cost of getting an amp tech to make the mods for you.  There’s nothing nano about the voltages in this amp.  If in doubt, get a professional to help.

right,  having got the safety warning out the way on with the mod info….

Modding a Nanovalve is a bit of a challenge as there isn’t much space at all for any additional components. The attraction (to me) of it’s small size makes working on it a bit harder than on a “full size” amp.  It’s built on a PCB, which as I said above, has the valve sockets mounted on it.  I’ve got the full cct diagram, layout, parts list etc from Peavey, so that will help if I feel I need to “tune” the circuitry.  As it’s a 5W amp it still gets louder than I’d like in the house, so getting it into triode operation (hence lowering the power) is definitely to be done. I’m on the hunt for a cct diagram for a Champ (I’ve got Dan Torres book and think there’s one in it) to compare with the Nanovalve and see what the differences are.  My priorities for mods are : pentode/triode operation then a replacement speaker  (which will probably make the biggest difference in sounds).  After that, I’ll live with it for a while and see how it goes.

it’s been pointed out to me that the basic circuit design of the Nanovalve and the Peavey ValveKing Royal 8 are essentially the same, so it should be possible to modify the Nanovalve to make it into a VK Royal 8.  While this is feasible, it’s not something I’ve done yet as I don’t feel the need to add a tone control  – that’s what your guitar tone control’s for!    Also, now that I’ve added L-pad attenuators I don’t have the same need for a master volume control either.

Some comments on how you get into the Nanovalve to work on it.  

There are 4 screws on the back which hold back of the cabinet to the amp chassis and there are 4 screws which hold the valve protection grille in place.  I found that I needed to take out all of these screws to work on the amp pcb.    The two screws which hold the handle in place on the top of the cabinet actually also hold the amp chassis in place, so they need to be taken out.  They’re a bit of a fiddle when it’s time to put it all back together.  Having removed the back panel and the handle, the chassis can be slid out.  The chassis consists of two folded sheets of metal which are held together with three screws.

Once you’ve got the chassis out, you need to separate the two halves of it.  Undo the three screws and take the volume control knob, and volume pot nut/washer, input jack nut/washer off and then the PCB is accessible.

As they say in the best of Haynes manuals, re-assembly is simply a reversal of all the above steps!  I found locating the handle screws to be a bit of a nuisance.  But otherwise it was dead easy.

Fitting a Pentode/Triode Switch

As the output valve is an EL84 it can safely be run in triode mode, which lowers the power output.  It might be burning the valve out a bit faster, but that’s a small worry.

Here’s the diagram for the pentode/triode switch information which Trev Ridney sent to me.

A simple swap out of R9 for a 1K @ 1W value, a small SPDT switch, some wire and that’s it.  I located my switch on the valve protection grille at the back of the amp, so I didn’t even need to drill any holes either.   This can be seen in the photo here.

To wire up the switch I connected two wires to the pads on the bottom of the PCB for P5 and P6, with the 3rd wire being connected to one end of the replaced R9.

A side effect of changing the amp to triode mode is that the hum increases.  It’s probably too loud for recording wit, but I find I can live with it  (it’s not that loud, just louder than in pentode mode).  Another mod Trev suggested for the Nanovalve, to potentially reduce the hum in triode mode  is to increase C5 to a larger value, say 47uF @ 450V which *may* help. I bought this value of capacitor but unfortunately there isn’t enough space on the PCB to fit it.  So they hum…….

Speaker Changes

The stock speaker is poor – very poor indeed. Remember when you take it out to throw it as far away as you possibly can.  When I took the original speaker out I tried gently pressing it to see how much movement there was.  There is virtually no movement at all in the paper cone.  In fact the cone distorts as you push it rather than moving slightly in and out.  No wonder it sounds harsh!  Changing the speaker for any other 8ohm 8″ unit is a very highly recommended mod for the Nanovalve.

I’ve got two Nanovalves, with a different speaker in each. One has a Celestion PG8A and the other has a Jensen C8R.  The Jensen is a far more impressive speaker than the Celestion.  It’s far bigger speaker cage and has a larger magnet. it certainly looks much beefier than the Celestion

Celestion PG8A :  I’ve now changed the speaker for a Celestion PG8A.  Why did I choose this one?  Well I was finding it a little difficult to source 8″ speakers at what I considered to be a reasonable price.  I then found an online seller offering the Celestion Special 8 and the Celestion PG8A.  I’d never heard ofthe PG8A so I wrote to Dr Decibel at Celestion asking what the differences between the speakers was and this is his reply “They are very similar but the PG8 is a little smoother at the top end and tighter at the bottom end.”    So I bought a pair of them – as they were at half the price of the Special 8.    I’ve only tried it very briefly at domestic volumes but this is a major improvement to the Nanovalve.  Most definitely a modification worth doing.  I bought the PG8A for £7.99 each.  Fitting the Celestion was straightforward as it is very similar in size to the stock speaker.  Remove the 4 screws at the back of the cabinet and the two screws holding the handle on.  You can then remove the back panel and the amp chassis as a unit.   When refitting the back panel & amp chassis I discovered that the Celestion is actually slightly taller than the oem speaker.  This was a slight problem as it meant the valve protection cover no longer fitted back flush.  A simple bend of the valve protection guard such that it wasn’t at a right angle anymore cured this.

Jensen C8R :  I’ve now changed one of my Nanovalves to have a Jensen speaker.  This wasn’t quite as simple as fitting the Celestion as the Jensen isactually a bit larger than the Celestion.  The Jensen has a larger and more heavy duty speaker cage and a larger magnet.   It’s a very neat fit into the Nanovalve cabinet. As with fitting the Celestion,  the valve protection cover at the back needs to be “adjusted” to clear the magnet.  More so in the case of the Jensen speaker.

Although the Jensen is a beefier speaker than the Celestion, in practice I can’t hear much difference between them. Certainly, when the amps are running at anything like maximum there’s little noticable difference.

External Speaker Jack

Another dead easy mod, which I’ve so far only done on one of my Nanovalves is to fit an external speaker jack so that it can be used with a bigger cabinet. I’ve not drawn this one up, as it’s so easy.  I put a jack socket into the connection to the speaker, wired such that if it’s used then the connection to the internal speaker is disconnected.  A photo showing where I fitted the jack is here. One of my friends commented on this section of this page :

You’ll need to remember to watch the impedance of the cab you plug in. If it’s different from the ohmage of the normal speaker you risk blowing the transformer. It’s not as simple as just drilling a hole and adding a jack in parallel to the speaker. next you need to also remember that depending how you wire it you would add the internal speaker value on to it.  I.E. It’s an 8 ohm speaker and you have an 8 ohm 2×12 if your mod automatically cuts out the combo speaker then everything’s fine. (there’s a stereo jack from Maplin that can be wired to do this) if you don’t have it or a switch to cut the internal speaker out of the circuit then your going to have two 8’s in Parallel giving you 4 ohms or 16 depending how it’s wired.”

Wise words indeed.  The internal speaker is 8 ohms and the output transformers, like the rest of the amp, have been designed to a cost, so they don’t look overly robust or like they’ll tolerate an impedance mismatch for long.  I will get around to drawing this mod up because it’s quite simple.   Actually a really simple way of doing this, which doesn’t need any special kind of jack socket is simply to take the wires from the speaker to any old jack socket and fit a new lead to the speaker, with a jack plug on it.  et voila – when you want to use an external cabinet you simply unplug the internal speaker and plug in your external cab.

Valve Changes

I’ve been reading about valves and learning more about how they differ.  As a result I’ve now fitted the JJ ECC83S into one of my Nanovalves.  A non scientific A-B test is described below.  Also now on the look-out for Mullard EL84s to try them as output valves.  I found these reviews from Watford Valves to be interesting :  12AX7/ECC83   and EL84.    Swapping valves is simple.  It would probably be a good idea to check the voltages and the bias to each valve, but as I replaced like with like I’ve not done this.

12AX7 Changes

I’ve had time now to A-B my two Nanovalves.  One is stock and the other has the JJ valve installed. I used an A-B footswitch with both amps set at the same levels and played a series of riffs, chords and solos using several guitars for about half an hour or so.  It’s not exactly a lab conditions exhaustive test, but it did give a good test of the tones from the two amps. I also had my son come in an listen to the differences too.  A second set of ears is a handy thing to have!

What a pleasant surprise. There is a very audible difference,  I can’t really say which breaks up soonest, or which has the smoothest transition to overdrive, but the difference in overall tone is there.  The JJ gives a much fuller, richer tone. the EH is somehow thinner and more buzzy in comparison. It’s not that one is better than the other, just that they are different.   To try and characterise the differences isn’t easy, but the JJ gives the Nanovalve a more a bluesy rock tone and the EH is more of a metal harsher tone.  It’s not as pronounced as black vs white, but more light grey vs dark grey.  Your mileage may vary, but I prefer the tone from the JJ ECC83S over the Electro Harmonix 12AX7EH. I’ll be changing my second Nanovalve to a JJ ECC83S.  I’ll leave it stock for the time being though, to act as a reference point for future mods.

EL84 Changes

I’ve changed one of the Sovtek EL84s for a Mullard EL84.  Another move in a direction which I like.  The Mullard valve , much like the JJ ECC83S, makes the sound smoother.  if you’re after a more buesy/70’s rock sound then this is another change worth doing.   Again, I A-Bd the change against my stock Nanovalve and I prefer the changed one.   I’ve also now tried the Russian military spec version the 6P14P-EV/EB.  Although this might be moving into the realms of snake-oil as I didn’t really notice any marked difference in tone between the EL84 and the 6P14P.  I’ve left the 6P14P in my Nanovalves as it might be a little bit cleaner……… Of course if you try this your mileage may vary.

L-pad Attenuator mod

Even when running the NanoValve in triode mode it’s still a pretty loud amp if you want to get the classic rock tones of full-on valve overdrive.  There are several approaches which coold be adopted to tame it in the decibels stakes.  The choices are either to fit a power scaling kit ot to fit an L-pad attenuator.   Power Scaling works by lowering the B-voltage at the output stage and requires the fitting of additional components.  Power Scaling preserves the tone of the amp.  I’ve been in discusion with the guy who runs this websiteabout fitting one of his power scaling kits to a NanoValve and it is certainly electronicly possible.  I’ve not done this as I’m not sure how I’d find space for the additional components.  I’m sure they could fit, just that I’m not sure how to fit them.  Although Power Scaling is the technical ideal solution I’ve not gone down this road.  So, following email conversations with several others including Nick Reynolds  (see links section) I decided to see how the Nanovalve would sound with an L-pad attenuator fitted.

Ted Weber has info on L-pad attenuators on his site here.  There are a sites around which explains what an L-pad attenuator is and how it works.  Tone junkies are right to point out that an L-pad doesn’t provide an inductive load to the amp and thus can’t possibly offer the same frequency response and therefore tone as the amp starts with.  This is correct, but I’m happy to sacrifice a little high end frequency response in return for getting the full-on valve goodness as really low decibel levels.

Following a recommendation from Phil Taylor I bought my L-pad attenuators fromThe Electronics Shop it’s their item no. 962-110   LP-100-8 L Pad Attenuator. My thanks go to Phil for suggesting this supplier.

Fitting the L-pad attenuator

I didn’t want to do anything which would result in the L-pad protruding from the case of the Nanovalve so I fitted it to the rear valve cover.  The photos below show how this was done.  The third photo was sent to me by Phil Taylor of an alternative way of fitting the same L-pad attenuator.  He used the fitting and knob which is supplied with the L-pad.  As I carry mine about I wanted to avoid having it stick out the back of the amp.

As you can see I’ve fitted mine to the valve cover. Being lazy, instead of drilling another hole in the valve cover I removed the mains lead from it’s position and used the hole it had previously been in to mount the L-pad.

This is a view of the back of my Nanovalve.  You can see the external speaker output and the pentode/tride switch in this picture as well as the L-pad. This is a more close up view of the L-pad. There’s not much space between it and the output valve! This is an alternative way to fit the L-pad.

This is a great mod for this amp.  yes, the purists will say it sucks the tone but if Ted Weber is prepared to suggest it on his website, then I’m not so worried about it with this low powered amp. It certainly lets you get the AC/DC, Free. ZZ Top, Gary Moore, Thin Lizzy etc overdriven valve amp tones at living room levels.   Highly recomended and easy to do. A side effect of fitting the L-pad attenuator is that I don’t need the pentode/triode option anymore.

Links to other sources of info on Nanovalves.

for some reason, it doesn’t seem to be listed on the Peavey web site at all.

Harmony Central Reviews

Nick Reynolds blog.  He describes, with good pictures how he tamed his NanoValve by fitting an L-Pad Attenuator to it.  His approach was slightly different from mine as he used a larger L-pad attenuator which might not have fitted where I’ve fitted mine.

youTube clips of other peoples modified Nanovalves –  here (I’ve emailed the guy from France, hopefully he’ll send me the information on the mods he made and I will publish them here) and here. (although this is demo of a stock Nanovalve)

One thought on “Peavey Nanovalve Mods

  1. Rado


    I really liked your article on modding this nice little amp. I would also add the Jensen C8R, P8R or the CH8(known as ḾOD in the US) to the list of possible speaker replacements. I wanted to give you a heads-up – I did some mods on my NanoValve which you might want to check out. The more important ones – I installed a Master Volume and a VVR. You can find my modified schematic with the (I hope straightforward enough) instructions here:

    Samples and pics can be found here:

    I wouldn’t mind if you add them to your list of mods. Take care!



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