Since the very beginning, we have been making repairs and modifications of ESH amps as well as amps made by other manufacturers. To this day, we have helped thousands of domestic and international guitar players make their equipment sound either proper or, more specifically, the way they wanted it to sound in the first place. After all, not everyone is fully satisfied with the stock tone even when all seems to be working well. Many times, customers have been blown away by the result of our careful tuning, often saying that their amp never sounded that good, not even fresh from the box.

Making an amp sound its best in a part replacement or full restoration exercise requires deep knowledge. This includes careful selection of the tubes, exact setting of bias, and last but not least thorough familiarity with the parts’ sound characteristics. We have that and more – the educated opinions of and sincere feedback from those of our loyal, demanding customers who are music professionals playing different styles.

Prior to undertaking work on an amp, we consult the player about the kind of music they play, the guitar and other equipment they use and the sound they are looking for. This helps us better understand his/her actual needs and allows us to determine which parts or tubes would be best to change to maximize the amp’s potential for the player.

We repair and modify instrument tube amps from virtually all past and contemporary vendors from around the world including Fender®, Marshall®, Mesa/Boogie®, Peavey®, Soldano®, VOX®, Rivera®, Ampeg®, Bogner®, Crate®, Engl®, Laney® and many others.

Retubing and re-biasing

Tubes are the essential part of any tube amp; their health and sonic performance determines the overall sound and reliability of the tube rig more than anything else. Due to their nature, tubes wear out over time so they need to be periodically replaced.

Various vendors’ tubes are vastly different electrically, mechanically and sonically; also there is a lot of variance even between tubes coming from the same product line. Tubes can be (an often are) noisy, microphonic, they can hum, have insufficient gain, be poorly matched, deficiently burned-in or not working at all, even when sold as brand new and perfect. At the same time, every amp is different and even each tube position needs a tube with diverse properties. Hence, going to the shop, buying new tubes, putting them in and hoping for the best rarely works. Countless times, over and over again people fork out money and time only to learn the hard way that improper re-tubing will turn even the best of amps into a piece of unreliable, poorly sounding hardware.


Retubing (and, of course, consecutive re-biasing) is the most common job we do given it has to be done periodically on all tube amps, regardless of type and make. We use only the best tubes on the market today, which are then burned in for 48 hours, electrically and mechanically tested, measured, matched, properly set up in the amp and finally (and most importantly) tested sonically with regard of the sound required. Also, our extensive knowledge about various tubes’ characteristics helps us determine which tubes to use in each case. As for the re-biasing, we are doing it not only by numbers, but also by ear to be assured that the resulting sound is really top-notch.

In this regard, we strongly recommend that every player have at least one spare, custom-selected set of both preamp and power tubes (the latter of the same electrical properties as the ones currently fitted in the amp to avoid re-bias) at hand – especially when on tour – to prevent tinkering with the amp to identify the blown tube in the middle of the show. Instead, replace all tubes in a moment and play on as if nothing has happened.




When a repair has to be done, we always check the whole amp, not just replace one broken part as many possible defects are not evident to an untrained eye. Additionally, over time, we found many parts to break up periodically in the most common types of the amps; even if they seem OK for the time being, they would inevitably break in the future, so we always recommend to have them replaced too so as to maintain the amp’s reliability and sonic performance.

For repairs, we use only quality – sometimes even hard-to-find or boutique – components, whose properties will preserve the amp’s original sound best.

We are of help also when the cabinet or amp case repair – or full restoration – is requested. In extreme cases – i.e. should the amp or combo case be really damaged, the player wants to divide a hard-to-carry 2×12” tube combo into a separate head + box etc., we can even build a brand new cabinet(s) if need be. Naturally, we provide the standard cabinet and speaker repair service too.

Every time we consult the customer first to get to the best available solution in each particular case. Needless to say, we always return all original parts, including tubes, to the customer.

Fine tuning, modifications, upgrades

The players often ask for a modification of their equipment without understanding how much potential there is if the amp were serviced properly. Especially vintage equipment often looses its precious tone due to unprofessional repairs and modifications through the years. On a different note, many amp vendors change their amps’ circuitry over time, not visible to the average user, and usually just one of these versions (if any at all) sounds really good. Also, manufacturers often introduce different, mostly cheaper, worse sounding components after the initial batch to save cost. On the other hand, even the best parts will not help an amp with inherent design flaws.

So, before any actual tuning or modification, we always have to make the amp sound the way it was originally designed in the first place. No modification or tuning can help the amp which has bad tubes or broken and/or unreliable components in. Only when this is remedied and the sound of the amp is still far from the player’s expectations, will we proceed to mods.


Through modification, we can voice virtually any decent amp to the player’s specific needs, add a new channel(s) and/or effects loop(s), change dynamics, increase or lower the distortion level and so on. This is the “black magic” of what we do. We also frequently upgrade older ESH amps for players looking for the sound and/or features offered by our most recent products, thus preserving the value of their original investment.

Having said all this, please remember that not all modification requests are reasonable, viable or even doable (we still have to learn how to turn a low-cost Chinese unit into a well-sounding amp), so be ready to discuss and perhaps reconsider your requirements with us.

We always recommend to fine-tune amps no sooner than after at least one year of heavy usage (the more the better); only after this initial break-in do amps start sounding the way they were designed to.


Although often underestimated, cabling is a very important part of the signal path and its quality has a significant impact on the final sound. There is no excuse for a guitar player with a great guitar and high-end tube stack to use low-grade, unreliable cables as this will inevitably result in sub-par sound no matter how the amp is set. Additionally, bad speaker cabling can even damage your amp as all tube amps must ALWAYS be connected reliably to the load when switched on.

To preserve the sound quality and value of our products, we now offer a wide range of custom-built, high quality guitar, speaker, microphone and general-purpose cables made solely from time-proven, top-rated CORDIAL® instrument wires, KLOTZ® coaxial heavy-duty speaker wires and the original XLRs, SPEAKONs and jacks (straight, angled, switch-equipped etc.) by NEUTRIK®. We could even re-wire your whole pedalboard or rack for the best sound and the often neglected long-time reliability.

Additionally, all signal cables we make are color marked according to the recommended signal direction to guarantee that each cable always performs at its best.

Technical consultations

While the amp is the essential driver of the guitar rig, it has to work well with all the other parts of the signal chain: the guitar, enclosure, effect processor, cabling and so on. Should any of these possess or produce improper sonic qualities, the sound of the whole setup will be affected. Sometimes, diverse technical difficulties or missing features prevent the player from reaching full satisfaction.

We at ESH are all guitar players. We know how various amps can and should sound in the first place. And with thirty years in the professional guitar gear business, we offer players our extensive knowledge to assist them in their own quest for the ultimate sound.

Contact us with your requirements or with your dreams, and we will go out of our way to make them come true

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