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Avalon AD2055 Successfully modified for gain range & band on/off Recorders, Players & Tape Machines
Old 8th December 2012
  #1
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Avalon AD2055 Successfully modified for gain range & band on/off

Since this equalizer has been discussed a bit more than usual recently & it seems quite a few mastering people are using it, thought I'd post details of a modification that has really transformed it & made it much much better for mastering...

Robin Schmidt @ 2496 Mastering posted details of a mod a few years ago to half the gain range: https://www.gearslutz.com/board/3801146-post25.html Well this I can confirm the resistor mod works perfectly and is easy to do - just change eight resistors - very little disassembly.

For anyone who wants to take it a bit further as I have done you can install DPDT centre off toggle switches & simply solder the original resistors to one half of the switch and the double value resistors to the other half. This way you have centre position - band off, up position (or down, whatever you prefer) - standard gain range then down position on the switch is half gain range.

The more elaborate mod is a lot more work since the unit has to be completely disassembled which takes quite a while. Also, holes need to be drilled on the faceplate & the inner chassis requires large holes for the switch bodies to go through - quite a lot of metalwork. Don't be tempted to drill the inner chassis with the mainboards in place - the 2010 mkIV op amps don't like shorts - trust me

I can say though it was really worth it - the gain range alone transforms the EQ but band switches are also very helpful.
Noise wise it's actually less but IMD is slightly (very slightly in the low decimal places) higher - still less than most other equipment I measure since it is a purist design to start with. All other specs THD, phase distortion etc... are about the same. Usability - well now it's usable and not a figity nightmare to set/recall/add small amounts of gain. What's also great is that no re-trimming/re-calibration was required since the potentiometers are unchanged.

Hopefully some people find this useful.

Here are some pictures of the modification:
Attached Thumbnails
Avalon AD2055 Successfully modified for gain range & band on/off-1-img_4916.jpg   Avalon AD2055 Successfully modified for gain range & band on/off-1-img_4915.jpg   Avalon AD2055 Successfully modified for gain range & band on/off-1-img_4913.jpg  
Old 8th December 2012
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That is very cool! Awesome to see someone did the gain range mod (makes so much sense with that unit)... But adding the switches for both switchable range and band on/off is genius. I wonder: how does the unit sound with all bands off? I.e. how much of the general box tone comes from the pots in path?

-------

To make this thread a good archive resource, here's the basic 2055 gain range mod details from Avalon again:


To halve the 2055 Boost/Cut range by replacing resistors, for each channel:

- double the value of the following resistors (or get as close as possible to double the value):
Band1: R7 (18 kohm)
Band2: R40 (4,75 kohm)
Band3: R20 (4,75 kohm)
Band4: R44 (15 kohm)
- When you're done, IF NEEDED, re-calibrate unity by adjusting VR1 (Band1), VR2 (Band2), VR3 (Band3) and VR6 !!!! (Band 4). Do NOT touch the other VRs.


Charles, can you confirm those values were all correct?
Old 8th December 2012
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Hi

When all bands are switched out the hint of "electric" and "shimmer" in the high end (as you have used to describe it in the past) seems to go. When standard -even when all pots are at centre detent the unit has that character slightly in the high.

About those values - they are perfect, the only thing was that the two mid band resistor component designators are swapped so R40 is band 2 and R20 is band 3 - had to swap those two switches round in the end - same resistors so not a huge problem.
Old 8th December 2012
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Quote:
Originally Posted by CharlesCola View Post
Hi

When all bands are switched out the hint of "electric" and "shimmer" in the high end (as you have used to describe it in the past) seems to go. When standard -even when all pots are at centre detent the unit has that character slightly in the high.
That's very interesting. Might be one of the factors that contributes to the sound difference (to my ears) between the 2055 and 2077. I think you may have made yourself a very useful mod there

Quote:
About those values - they are perfect, the only thing was that the two mid band resistor component designators are swapped so R40 is band 2 and R20 is band 3 - had to swap those two switches round in the end - same resistors so not a huge problem.
Thanks, I'll change it around in the list above for better reference then.
Old 9th December 2012
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pmx
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Very cool mod! Didn't know about the gain mod, but this takes it a step further! I quite like the tone of the 2055 actually...
Old 9th December 2012
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Quote:
Originally Posted by 24-96 Mastering View Post
That's very interesting. Might be one of the factors that contributes to the sound difference (to my ears) between the 2055 and 2077. I think you may have made yourself a very useful mod there

Well, when using the high end a lot I feel sometimes not always to want that texture (electric, shimmer, sizzle etc...) it is quite a pronounced feel. Whether it is only the pots or what making this I do not know...

The actual passive high end from Avalon (also on the vt-747) is really very very nice - it seems also cleaner on the 747 i.e. less the electric sizzle and I can imagine totally refined on the 2077 - this is why I wish still one day for one of those ...

But overall the gain range alteration makes it usable in the meantime.
Old 19th May 2015
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Very cool thread

Do you know if the Freq and Q knobs are soldered on the PCB or not ? I can't see this on those pics.
Also would it be possible to add detented controls for those aswell ? For the mid bands I mean as the lows and highs appears to be switches.
Old 19th May 2015
  #8
I love the sound of the Avalon 2055!'
Old 20th May 2015
  #9
Gear Nut
 

+1

it is by no slim margin my favorite piece of outboard i have ever purchased. can't even imagine how the 2077 must sound.....but 13k??? i may never get the opportunity to try that one out and that's a shame.
Old 29th October 2018
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I would like to make a formal apology to the designer of the Avalon AD2055 - this was a disgraceful thing to do to such a beautifully designed piece of equipment. i would not recommend anyone to do this modification.
Old 29th October 2018
  #11
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??

I thought Avalon themselves gave the indication to do this mod..?

Quote:
Originally Posted by CharlesCola View Post
I would like to make a formal apology to the designer of the Avalon AD2055 - this was a disgraceful thing to do to such a beautifully designed piece of equipment. i would not recommend anyone to do this modification.
Old 29th October 2018
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I forgot about that, thank you for reminding me - it was Mike from Avalon who provided the details on resistor changes but the idea to add switches was mine - it wasn't right to drill the faceplate and inner chassis like that - it's so heavy duty and the inner chassis holes are rough. It also conflicts with the higher end AD2077EQ which has that functionality as standard.
Old 29th October 2018
  #13
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There's nothing wrong in modding a unit you own, IF you know what you're doing of course (sometimes you can do more damage than anything ie : opamps swapping for exemple). Now I agree with you that SHARING this kind of information, on modding a piece of gear wich is still in production, is something you should do with the agreement of the company itself
Old 29th October 2018
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Well I spent many years making incremental improvements to a Thermionic Culture Phoenix Compressor which I believe takes it to a completely different level. The main mod allows finer tuning of the harmonics to just how I like them. It's one of those subjective things i.e. you could do exactly the same mod but really the key is using a good analyser like ARTA to experiment with with different distribution of harmonics and the balance of 2nd and 3rd order harmonics to your taste.

Have you modified any of your gear?

Last edited by CharlesCola; 29th October 2018 at 08:47 PM..
Old 29th October 2018
  #15
I feel like you should be able to mod anything you own and share your result and recipe freely (if you want to) no matter what the designer would think about it.
Modding gear is not easy or safe, you loose warranty and the company could refuse to take it back for revision or simple fix (even unrelated to the mod).
To me it's part of the process of building your own chain, some piece doesn't really exist the way you want to so you start with a prduct which is close enough and then work around.

I don't dot much modding but one easy thing to do is changing weak power supply for better one.
For example, I replace the cheap PSU of my dangerous source (phone charger kind of thing) with a much bigger serial 8A PSU, the difference on low end transient was not subtle.
Old 30th October 2018
  #16
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Well I agree and disagree here

Quote:
Originally Posted by Saxnscratch View Post
I feel like you should be able to mod anything you own and share your result and recipe freely (if you want to) no matter what the designer would think about it.
Yes, IF you know what you are doing, indeed you should do what you feel "up to" and mod your gear the way you want.(and loosing warranty by doing so) BUT I disagree that you should share this information without the consent of the Designer and company if it's still a unit in production. If you were the designer trust me you wouldn't be happy to see someone spreading "false" information on a design you spend years working on. I remember a thread here, where the Buzz Audio REQ 2.2 was involved, saying that the regulators on it were making the unit sounding quite "bad", and that you could improve it with some new regulators. (wich in turns improved the sound). In the end NO ONE was able to prove this with a clear measurement showing the difference. And then, people started to slowly realise (hear) that the so called "improving mod" was sounding even worse than the original. And then someone was even offering this mod for sell ! (wtf)
If you share this kind of thing freely on forums without even talking to the engineer first, I believe this is an absolute disgrace and lack of respect to the gear and its designer.
Forums are SO quick at spreading words that are, in the end, absolutely untrue. If I listened to gearslutz, the Manley Vari mu was clearly a "bad sounding unit" that I should stay away from...


Quote:
Originally Posted by Saxnscratch View Post
Modding gear is not easy or safe, you loose warranty and the company could refuse to take it back for revision or simple fix (even unrelated to the mod).
To me it's part of the process of building your own chain, some piece doesn't really exist the way you want to so you start with a prduct which is close enough and then work around.
Agree, but again ONLY if you know what you're doing. As I said many times people do more bad than good by trying to mod their gear. And their not aware of this because they either don't have the proper knowledge or material to do the right measurements etc. Oscillation can go as high as 200 khz, 1 GHZ, etc, far from your "regular" audio spectrum analyser. Not to speak that some gears have lethal voltage within them and that you should be extremely carefull, and stay away from it if you don't know what you're doing.


Quote:
Originally Posted by Saxnscratch View Post
I don't dot much modding but one easy thing to do is changing weak power supply for better one.
For example, I replace the cheap PSU of my dangerous source (phone charger kind of thing) with a much bigger serial 8A PSU, the difference on low end transient was not subtle.
You mean the wall swtiched power supply plug ? Or directly removing and changing the power supply INTO the unit ?
Old 30th October 2018
  #17
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i say mod anything freely, and share the info freely, at your own discretion.

the gain pots on the 2055 have always been a problem,

as us mastering engineers like to make 0.5dB incremental changes,

especially on that HF sheen knob which sounds wonderful.

but stock, as it ships, it has a design flaw,

and the designer should be acutely aware of it,

perhaps even do a recall to fix the units for free.

mtcw, jt
Old 30th October 2018
  #18
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Mmm I disagree here Jerry, The 2055 is the "mixing" version and so no design flaws here. If you want to use that marvellous HF in 0.5 db increaments, than there's the 2077 wich is the Mastering version, precisely designed for this. Now it's expensive, and that's why Mike at Avalon gave the OP the mod procedure to do this on his unit. That's why you should always refer to the designer first.

Quote:
Originally Posted by Jerry Tubb View Post
i say mod anything freely, and share the info freely, at your own discretion.

the gain pots on the 2055 have always been a problem,

as us mastering engineers like to make 0.5dB incremental changes,

especially on that HF sheen knob which sounds wonderful.

but stock, as it ships, it has a design flaw,

and the designer should be acutely aware of it,

perhaps even do a recall to fix the units for free.

mtcw, jt
Old 30th October 2018
  #19
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the unik's Avatar
Quote:
Originally Posted by CharlesCola View Post
Well I spent many years making incremental improvements to a Thermionic Culture Phoenix Compressor which I believe takes it to a completely different level. The main mod allows finer tuning of the harmonics to just how I like them. It's one of those subjective things i.e. you could do exactly the same mod but really the key is using a good analyser like ARTA to experiment with with different distribution of harmonics and the balance of 2nd and 3rd order harmonics to your taste.

Have you modified any of your gear?
Yes I did, most of them actually. Sometimes succesfully, but most of the times not.
For Exemple my Klein & Hummel UE 400 came out very well on the aesthetic side of things (pic attached) but the circuitry is almost impossible to mod because of how it's designed (dual concentric centertapped linear pots as an exemple) and without compromising the sound of the unit itself. BUT redesigning that faceplate made the unit WAY more usable thanks to the bigger knobs and precise markings.
Attached Thumbnails
Avalon AD2055 Successfully modified for gain range & band on/off-k-h-ue-400-custom-mastering-version-down-view.jpg  
Old 30th October 2018
  #20
Quote:
Originally Posted by the unik View Post
Well I agree and disagree here



Yes, IF you know what you are doing, indeed you should do what you feel "up to" and mod your gear the way you want.(and loosing warranty by doing so) BUT I disagree that you should share this information without the consent of the Designer and company if it's still a unit in production. If you were the designer trust me you wouldn't be happy to see someone spreading "false" information on a design you spend years working on. I remember a thread here, where the Buzz Audio REQ 2.2 was involved, saying that the regulators on it were making the unit sounding quite "bad", and that you could improve it with some new regulators. (wich in turns improved the sound). In the end NO ONE was able to prove this with a clear measurement showing the difference. And then, people started to slowly realise (hear) that the so called "improving mod" was sounding even worse than the original. And then someone was even offering this mod for sell ! (wtf)
If you share this kind of thing freely on forums without even talking to the engineer first, I believe this is an absolute disgrace and lack of respect to the gear and its designer.
Forums are SO quick at spreading words that are, in the end, absolutely untrue. If I listened to gearslutz, the Manley Vari mu was clearly a "bad sounding unit" that I should stay away from...




Agree, but again ONLY if you know what you're doing. As I said many times people do more bad than good by trying to mod their gear. And their not aware of this because they either don't have the proper knowledge or material to do the right measurements etc. Oscillation can go as high as 200 khz, 1 GHZ, etc, far from your "regular" audio spectrum analyser. Not to speak that some gears have lethal voltage within them and that you should be extremely carefull, and stay away from it if you don't know what you're doing.




You mean the wall swtiched power supply plug ? Or directly removing and changing the power supply INTO the unit ?
I agree with a lot of what you said because for me, infos about modding gear found on the internet should be treat as any info found on the internet.

So now, if someone is ready to mod a 4k€ unit without any knowledge just because someone on the internet said so, it's a really stupid move.

To me, the right path of modding a gear is first having the need or the idea, then check on the internet if someone did it already while emailing the designer to get any insight from him and maybe the procedure (best case scenario).
Then doing the mod or ask a pro tech to do it.

I meant the wall switched PSU yes.
Old 30th October 2018
  #21
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I don't see the picture but I remember a conversation like this before.
Old 31st October 2018
  #22
I just wish Avalon was still making their EQs and Compressors.
Old 31st October 2018
  #23
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Quote:
Originally Posted by the unik View Post
Mmm I disagree here Jerry, The 2055 is the "mixing" version and so no design flaws here. If you want to use that marvellous HF in 0.5 db increaments, than there's the 2077 wich is the Mastering version, precisely designed for this. Now it's expensive, and that's why Mike at Avalon gave the OP the mod procedure to do this on his unit. That's why you should always refer to the designer first.
hmmmmmmmmmmmmmmmmm, then we agree to disagree!

the 2055 HF knob should have been 1dB steps instead of 3dB from jump street.

best, jt
Old 31st October 2018
  #24
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Or at least had a switch to choose...
Old 2nd November 2018
  #25
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I love the sound of my AD 2055. Wouldn't change a thing, its got the mojo. Just sending mixes through it makes them sound more polished. Its a great sounding EQ
Old 2nd November 2018
  #26
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The stock unit DB's step are 1/3/5/etc I don't see any design flaws for a "mixing" unit here...but anyway, knowing that you can mod the gain and that Mike gently gave the info on how to do it is a great thing, thing that not all companies would do
Old 3 weeks ago
  #27
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Hi, i have also made the gain mod and the avalon works fine in both mods. But i have a little different gain between left and right. Can anyone tell me which pot is for the gain to match both channels again?
Old 3 days ago
  #28
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Apologies for late response.

Being such a precision made EQ any differences must be down to the resistors used or the per band trim pots as detailed in the original thread (the discrete op amps are extremely well matched to each other) especially if the channels had matched gain before the mod: Avalon 2055 Boost/Cut Range Modification? -

Did you use 0.1% tolerance resistors?

To set the trim pots for equal per band gain for each channel Waves QClone is very useful when fed a loop with the EQ in the loop.

Hope this helps.
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