FAQ 2016-12-13T03:15:32+00:00

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How do I know if I need to send in the amp?

If you have been unable to troubleshoot and repair your amp with our phone/email assistance, we recommend you send the amp to us for service. If we feel a local tech can do the repair, we will work with him/her to be sure the problem is resolved.


Where do I send my amp?

Send to:
Two-Rock Amplifiers
Attn: Service RMA #
619 Martin Ave., Suite 6
Rohnert Park, CA 94928

Do I need an RMA#?

Yes you do! Please contact service and they will get all the shipping information and amplifier data needed to generate the RMA #. Please do not ship your item until you have been given the RMA #.

What do I include with my amp?

Please include a detailed note or a copy of emails exchanged with the service dept. about the issue with your amp. Include your return address and phone number. After your amp has arrived, we will notify you when the repair has been completed and the amp will ship back to you.


How do I know if my power tubes need replacement?

Replace your power tubes when:

  • amp loses volume
  • amp becomes noisy
  • certain functions become inop(example, no reverb, clean channel works, or no lead channel)
  • amp powers up, all tubes are lit, but no sound
  • amp is blowing the fuse

How do I know if my preamp tubes need replacement?

  • The tone is microphonic
  • The sound is cutting in and out
  • No sound is coming out at all
  • Sound is static

Which preamp tubes can I put in my amp?

The recommended tube types that you can use are:

  • Any 12AX7, 7025, 12AT7, 12AU7, or 12AY7 can be used in any position except the reverb driver tube.
  • For reverb driver, use 12AT7 or 5751

Which power tubes can I put in my amp?

This depends on the type of amp and the wattage range!

It is recommended to only use exact replacement tubes similar to what is installed at the factory. Be careful when deciding to install other types of 6L6, 6V6, or EL-34 based tubes. Not all have the same specs and some can’t handle the plate voltage of the amp.

Below is a list of comparable tube types:

6L6: 6L6GC, 7581, 5881

6V6: 6V6S, 6V6GT

EL-34: 6CA7



I get no sound out of my amp: Check your cable connections and then check the pre and power tubes.

The fuse keeps blowing: Most likely one of the power tubes has gone bad. If you have installed a new set and reset the bias and the fuse is still blowing please contact the service dept.

There is a crackling or “ocean” type static coming from the amp: Sound is being generated by one of the tubes. Easiest way to trouble shoot is to use a new tube for the preamp section. Swap one tube at a time. If noise goes away the tube you pulled is bad and can be discarded. If you go through all the preamp tubes and still have noise you will need to purchase a new set of output tubes and install them. Rebias and check. If noise is gone then you have found the bad tube.


What is the difference between the Small, Medium, and Large Combo’s?

The small combo was ultimately built around portability. That small compact design yields a very light weight pickup and go amp versus the larger and heavier medium and large combos. The tradeoff in the small combo is low end response and a slightly muffled middle frequency. As the cab size increase the bass response and dynamic range of the cabinet will improve.

Can I run 2 cabs at the same time on my one amp using different outputs?

The best way to plug multiple speakers in to one amp is to use either a parallel or series “Y” cable. A quick google search will yield shopping results. If using the parallel cable it will take two speaker loads and half the OHMs. In series it will double the OHMs.

EG: two 1×12 cabs rated at 8OHM. With both cabs running into the Y cable you will get a 4 ohm load. In combos you can take the internal speaker and plug it into the Y cable and add another speaker cabinet again creating a single load to insert in the correct speaker output jack on the amplifier.

Speaker Cabinet and Combo Wiring:

Care needs to be taken when installing new speakers or adding other manufactures cabinets to our amps. All of our amps that have reverb have a reverse phased output section. What this means is that the signal is in the negative swing as it leaves the amplifier. Traditional wiring of speakers takes the “+” positive terminal and connects it to the tip of the speaker jack, and the “-“ negative terminal and connects it to the sleeve of the speaker jack. When the speaker gets the signal in this configuration the speaker will push first and the pull. If the wiring of the cabinet is “Out of Phase” with the amp then the speaker will pull first and then push. We wire all our cabinets and combos that pair with our reverb amps with the “-“ speaker terminal going to the tip of the speaker jack and the “+” positive going to the sleeve. This way the signal that is in the negative swing as it leaves the amp see a negative polarity at the speaker. Causing it to push first and then pull. Making sure that the amplifier matches the cabinet will result in the amp/speakers working together. This will increase the dynamic range and tone of the system.

It will not hurt the amp to have the speaker running in an opposite polarity then the amp. It will just sound slightly muffled and not have the headroom. Amplifiers that have no reverb will want to be wired in the traditional manner.


Can I get mods done to my amp or change the wattage?

We don’t offer any mods in any way to our amps.

What speakers sound the best with your amps?

We have over the years tried many different speakers and have for the most part always used the Celestion 12-65 as our go to speaker. Starting in 2013 we switched are speaker choice the new Celestion Cremeback. We used this in our design process for that years models and found it to be even more musical then the 12-65.

There are many types of speakers out there and we fully endorse you as the end user to try them all and find the combination that works best for you.

What pedals should I use in the effects loop? And why is my loop killing my tone?

What pedals should I use in the effects loop? And why is my loop killing my tone?

Effects loops are best used when plugging in time based effects. EG: delay, chorus, reverb….. You do not want to use distortion/overdrive type based effects in the loop!

We offer three types of loops.

  1. Passive insertion point, half buffered, and fully buffered. A good understanding of pedal impedance and capacitive loss in cable length will help you to fully maximize the loop. It’s also a good idea to understand what buffers do and how they interact with your signal path. It’s worth noting that if you plug an effect into your amp and it sounds horrible it’s not the amp that sounds bad it’s the pedal killing the tone of the amp. There will be tradeoffs by adding effects into the signal path. The amp is always going to sound the fullest and most articulate with only a guitar plugged in.In the passive insertion point loops you will want to make sure that your pedal and or rack system are fully buffered on both the send and return. If you plan on plugging multiple pedals in the loop make sure to have a buffered pedal at the start of the chain and the end of the chain. If you find that the signal is getting clipped you will need to turn down the master volume. It is directly in front of the effects loop and unless your effect has an input level the master volume pot will acts as such.
  2. The half buffered loops are similar to the insertion point in all regards except that the return side of the signal chain has a buffer and a level control. This buffer will help reintroduce the signal back into the amplifier with little loss. The effect level control allows you to adjust how much signal is being reinserted back into the amplifier.
  3. The fully buffered loops will allow user to plug and play most effects systems with little or no tonal loss. The master volume now will have no impact on the signal hitting the pedal. This loop type has both a send and a return level.It is important to understand that “True-Bypass” pedals should not be used in the effects loop unless there are minimal cable runs, less than 1’, from the loop to the pedal. The high end loss of long cable runs while in bypass will kill the tone of the amp and lower the volume.

    It is always good to have buffers in the front and end of effect chains to minimize these losses of tone. “True-Bypass” pedals should be run in the middle of these chains. In instances when a fuzz or wah pedal want to see the guitar’s impedance these pedals can be run at the front of the chain.


My amp’s low end sounds great at low volumes, but when I turn it up, the tone gets flabby… what do I do?

Our circuit’s tone control section is extremely dynamic and it needs to be attacked in such a way to yield the best tone. As the amplifier increase in gain and volume more low end is generated. To minimize the “flub” as the volume increase turn down the bass.

Do your amps sound good at low volumes?

All Two-Rock amps are designed to perform best sonically when operated at 50 -90% of rated output. For any of the amps rated 50 watts or above they will not sound as full at the lower volumes as they would when they are pushed. Tubes like to be hit hard and saturated to get the best tone out of them. If you are using the amp for home use only or at low volumes you should look into the 22 watt or 35 watt versions.

What pickups and guitars sound the best with your amps?

All guitars, regardless of pickups, will sound best through a Two-Rock. Many TR amp users claim they are able to finally hear the true sonic characteristics of their various guitar/pickup combinations for the first time.

Do your amps work for acoustic guitars with pickups?

Yes, although we do not make an amp specifically for acoustic guitar amplification.

The tone bypass can be used as an adjustable boost by dong the following:

Turn the treble, mid, and bass controls all the way up. Now hit bypass. You’ll notice the amp doesn’t get louder(or gets very slightly louder) and has more mids. Now back off the tone controls gradually while switching in and out of bypass until you find that perfect level of boost.

Another method(if you just want 2 levels of clean and lead) is to insert a clean boost or volume pedal in the effects loop.