Wish "Deacy Amp" on Amp and Cab Blocks (Original Equipment and Circuit Diagram included)

F

frac-taro

Member
This is the summary of this request. Detailed explanations will be provided in the next post.

Request:
  • Addition of the "Deacy Amp" type within the Amp Block.
  • Inclusion of the "Speaker Impedance Curve" option within the Amp Block, featuring the measurement results of the speaker cabinet associated with the "Deacy Amp."
  • If feasible, Addition of the "Deacy Amp" speaker cabinet type to the selection of Factory IRs available in the Cab Block (Ideally, implementation as "Dyna-Cab").

Sourcing Original Equipment:
I possess a DIY kit replica of the "Deacy Amp" developed and sold by Knight Audio Technologies. Should it be agreeable to Fractal Audio Systems, I am willing to lend this replica for the duration required for development.
DA_Sample_2.jpg

Circuit Diagram:
Available, based on my guesswork from reliable sources:
DA_Schematic (guess).jpg

Note: There might be a delay in my next posts due to my lack of familiarity with the rules of this forum. I apologize in advance for any inconvenience this may cause. Your patience would be greatly appreciated.
 
I would like to propose the inclusion of a "Deacy Amp" simulation within the Amp Block of the AXE-FX III. The "Deacy Amp" holds significant historical importance, famously used by Brian May, and its simulation would undoubtedly enrich the AXE-FX III's offerings.
I understand that this request may involve considerable effort, and I appreciate your team's consideration. If any members of the forum support this request, even a simple "+1" acknowledgment would be greatly appreciated.

Here are the key elements of my request:
  • Addition of the "Deacy Amp" type within the Amp Block.
  • Inclusion of the "Speaker Impedance Curve" option within the Amp Block, featuring the measurement results of the speaker cabinet associated with the "Deacy Amp."
  • Addition of the "Deacy Amp" speaker cabinet type to the selection of Factory IRs available in the Cab Block (if feasible, implementation as "Dyna-Cab").
To facilitate the implementation of these features, I am prepared to provide assistance in sourcing the necessary equipment and circuit diagrams. Please find detailed information below:

<<Sourcing Original Equipment>>
I possess a DIY kit replica of the "Deacy Amp" developed and sold by Knight Audio Technologies. Should it be agreeable to Fractal Audio Systems, I am willing to lend this replica for the duration required for development. However, I kindly request that your company cover only the shipping costs associated with this arrangement.

I have confidence in the accuracy of this replica for several reasons:
  • Knight Audio Technologies oversees all maintenance of Brian May's amplifiers and equipment, thus ensuring access to the original "Deacy Amp."
  • The DIY kit I utilized was purchased from the following URL, which claims meticulous matching of parts with those of the original "Deacy Amp":
https://deacyamp.com/products/kat-kit-deacy-amp-board-and-components?variant=42577584783551
“Even the transformers are exactly the same specification as Brian’s.”
“And finally, we have even included the very rare and exceedingly hard to find vintage TO1-large can transistors that have all been individually tested and matched to ensure the amplifier performs perfectly.”
Click to expand...

<<Circuit Diagrams>>
As the original circuit diagram of the "Deacy Amp" is not publicly available, I have created a schematic based on information gleaned from publicly accessible sources. While I am not an electronics expert, I believe the sources used for creating this schematic to be reliable, drawing from verified information within Brian May's fan community.

In the next post, we will provide answers to 10 anticipated questions categorized as follows in the FAQ section:
I. Technical Feasibility
II. Appropriateness of the Request Content
III. Necessity to Implement This Request
IV. Presentation of This Request
 
<<FAQ vol.1>>

If you click on "Questions and Answers" of this post, you can see my answers for the following questions:

I. Technical Feasibility
  • Question 1: "Isn't Fractal's SPICE simulation lacking the necessary component models to simulate the Deacy Amp?"
  • Question 2: "The circuit diagram does not show detailed specifications of the transformers. Without reliable information on transformer specifications being publicly available, I believe implementation is impossible."
  • Question 3: "The Deacy Amp's speaker consists of a tweeter and woofer pair, with a crossover circuit included. Therefore, wouldn't it be challenging to accurately measure the Speaker Impedance Curve and IR?"
  • Question 4: "In recordings where Brian May used the Deacy Amp, room mics played a significant role. How can this be reproduced on the AXE-FX III?"
II. Appropriateness of the Request Content
  • Question 5: "The replica of the Deacy Amp from Knight Audio Technologies does not use the same design for speakers as the original, raising doubts about its accuracy as a replica. Why should this replica be used as a reference?"
  • Question 6: "The Deacy Amp is a small transistor amp. Therefore, wouldn't it be more appropriate to implement it in the Drive Block rather than the Amp Block?"

I. Technical Feasibility

Question 1: "Isn't Fractal's SPICE simulation lacking the necessary component models to simulate the Deacy Amp?"
Answer: As I am not an insider at Fractal, I cannot definitively answer whether their SPICE simulation covers the components necessary for simulating the Deacy Amp. Therefore, in the event that they are not available, I have explored the feasibility of creating models for these components.

The essential components for simulating the Deacy Amp are believed to be the AC125/AC126/AC128 transistors and two transformers. (In fact, among the electronic components included in the DIY kit replica of the Deacy Amp, aside from the transistor transistors, there were only common resistors and capacitors.)

For the AC125/AC126/AC128 transistors, SPICE models have been identified based on Valvo and Mullard datasheets and other publicly available nominal specifications at the following URL. While I cannot guarantee that the specifications of the transistors used in my replica match the nominal specifications, I believe they could serve as initial values for Fractal during development.
https://www.diystompboxes.com/smfforum/index.php?topic=78932.msg1207919#msg1207919

For information regarding the transformers, please refer to the answer to Question 2.

Question 2: "The circuit diagram does not show detailed specifications of the transformers. Without reliable information on transformer specifications being publicly available, I believe implementation is impossible."
Answer: As you mentioned, transformer is the Achilles' heel in reproducing the Deacy Amp, and it is anticipated to be exceedingly challenging, if not impossible. I must acknowledge that there is a possibility that Fractal may need to measure the transformers used in my replica ultimately.

The transformers used in the Deacy Amp are said to be the same as those used in the "Supersonic PR 80." (Since the original Deacy Amp was essentially developed from recycled materials, it is highly unlikely that John Deacon, the developer, modified or custom-ordered transformers at the time of development.)
Information about the transformers used in the "Supersonic PR 80" is documented in the following URLs. From what I can see, information regarding impedance and turns ratio is available.
https://groupdiy.com/threads/deacy-amp-transformers.78997/page-2
https://web.archive.org/web/20190417094749/http://oi48.tinypic.com/281rh1c.jpg
https://web.archive.org/web/20190417094814/http://oi48.tinypic.com/2lky25s.jpg

Question 3: "The Deacy Amp's speaker consists of a tweeter and woofer pair, with a crossover circuit included. Therefore, wouldn't it be challenging to accurately measure the Speaker Impedance Curve and IR?"
Answer: As I am not an expert in electronic engineering, I cannot provide a definitive answer to this question. However, since the Speaker Impedance Curve and IR currently included contain models of speaker cabinets with crossover circuits, I interpret that Fractal considers this issue manageable.
(For example, the "4 x 10 SV Bass" model for Speaker Impedance Curve and the "4x10 SV Bass HE 88" for Factory IR.)

Question 4: "In recordings where Brian May used the Deacy Amp, room mics played a significant role. How can this be reproduced on the AXE-FX III?"
Answer: Ideally, I would like Fractal to include a model of the Deacy Amp's speaker cabinet in the Factory Fullres IR. If this is challenging, I am considering sharing the IR of the ambience mic placed in the studio with the Deacy Amp, which I measured in the past, as a Free IR on this forum.

II. Appropriateness of the Request Content

Question 5: "The replica of the Deacy Amp from Knight Audio Technologies does not use the same design for speakers as the original, raising doubts about its accuracy as a replica. Why should this replica be used as a reference?"
Answer: Unfortunately, my replica does not feature the same Elac woofer-tweeter pair as the original Deacy. Instead, it utilizes a specially developed twin-cone speaker by Knight Audio Technologies, available at the following URL:
https://deacyamp.com/products/kat-dsp-6-5-tc-speaker-upgrade-for-vox-vbm-1-amplifier

One advantage of using this speaker as a reference is its ease of implementation in Dyna-Cab. With the woofer and tweeter arranged concentrically, it can cover all available mic positions with just one Cab type.
This speaker is highly regarded within Brian May's fan community, and concerns about its tone are minimal. Presumably, Knight Audio Technologies developed this speaker while matching it to the original Deacy Amp's speaker.

Question 6: "The Deacy Amp is a small transistor amp. Therefore, wouldn't it be more appropriate to implement it in the Drive Block rather than the Amp Block?"
Answer: The Deacy Amp is indeed an amplifier designed to be used directly with a speaker, and it is operated in that manner in practice. Therefore, interactions with the speaker are expected. To replicate these interactions, I believe that parameters available in the Speaker Tab of the Amp Block are necessary.
 
<<FAQ vol.2>>

If you click on "Questions and Answers" of this post, you can see my answers for the following questions:

III. Necessity to Implement This Request
  • Question 7: "Why is a dedicated model for the Deacy Amp necessary? Shouldn't it be possible to simulate a tone similar to the Deacy Amp by tweaking existing models in the Amp Block?"
  • Question 8: "Why should Fractal prioritize implementing the simulation of the Deacy Amp over those requests?"
  • Question 9: "Products like xxx have already released decent simulations of the Deacy Amp. Wouldn't it be better to use those?"
IV. Presentation of This Request
  • Question 10: "What is the intention behind such an unusually long post? It seems like you're trying to pressure Fractal into fulfilling your demands, which feels inappropriate."

III. Necessity to Implement This Request
Question 7: "Why is a dedicated model for the Deacy Amp necessary? Shouldn't it be possible to simulate a tone similar to the Deacy Amp by tweaking existing models in the Amp Block?"
Answer: Based on my experiments and research so far, I believe that a dedicated model for the Deacy Amp is necessary to accurately replicate its sound on the AXE-FX III.

In attempting to reproduce the Deacy Amp using the existing toolset on the AXE-FX III, I have explored various methods, but none have been able to faithfully recreate the Deacy Amp's sound to a satisfactory level. The closest approach I have found involved the following steps, but I still encountered issues with reproducibility:
<<Approach>>
  • Loading the IR of the Deacy Amp's speaker cabinet that I measured myself into the Cab Block.
  • Connecting two Drive Blocks in series, applying a Treble Booster to one and a Face Fuzz type to the other to generate distortion.
  • Selecting the "Class-A 30W" or "AC-20" type in the Amp Block, applying various adjustments to cut the bass frequencies, increasing the Hardness parameter to replicate transistor clipping, and adjusting the gain to an appropriate level.
Note: I did not utilize the Tone-Matching feature as it would limit tonal options.
<<Issues>>
  • Bass frequencies are still prominent. However, cutting the bass too much results in insufficient distortion.
  • The tone is not quite the same.

Regarding the question of whether there are decisive electronic engineering factors that prevent the reproduction of the Deacy Amp using the existing toolset on the AXE-FX III, as I am not an electronics expert, I cannot provide a definitive answer.
However, based on my understanding, certain characteristics present in the Deacy Amp's circuit are not available in the existing toolset of the AXE-FX III to the best of my knowledge, making it extremely challenging to replicate the Deacy Amp's sound:
  • The use of transformers between AC126 and AC128 in the circuit (likely a phase inversion circuit).
  • The output transformer being an auto-transformer, if one believes the description of the circuit based on the Supersonic PR 80 circuit used in creating the schematic.
  • The absence of a clear method to change vacuum tubes on the Amp Block to transistor characteristics.

Question 8: "Why should Fractal prioritize implementing the simulation of the Deacy Amp over those requests? There are already a significant number of requests for the Amp Block, some of which pertain to historically significant guitar amps but have not been implemented for a long time."
Answer: I defer to Fractal to make decisions regarding the go/no-go, priority, and order of the implementation of requests. However, I would like to share information that could serve as a reference for their decision-making process.

I expect Fractal evaluates requests based on both technical feasibility and business impact criteria. This would likely include factors such as the potential increase in sales of AXE-FX by implementing the Deacy Amp model, revenue growth from selling Dyna-Cab for Cab-Lab or IR Packs, as well as other metrics like market share and brand strength.
Unfortunately, I cannot directly estimate the above metrics. Instead, I will share information that could be used to estimate the potential demand for the Deacy Amp model:

1. The estimated global ownership of faithful replicas of the original Deacy Amp is around 300 units.
- According to the following sources, Knight Audio Technologies has sold approximately 250 replicas of the Deacy Amp (including DIY kits).
https://www.gbase.com/gear/knight-audio-deacy-brian-may-recording-amp-2010-black
Knight Audio Technologies Deacy Amp. A replica of Brain May's homemade recording amp, heard on countless Queen recordings. Only 150 of these were made.
Click to expand...
https://cdn.shopify.com/s/files/1/0...sembly_and_Test_Instructions.pdf?v=1659609148
The result of the three years’ work is 100 full sets of original vintage TO-1 transistors tested and fully matched in sets using an identical amplifier test unit.
Click to expand...
  • DoxyWorld (https://doxyworld.com/supersonic_pro.html) has also reportedly sold around 5 faithful replicas of the original Deacy Amp per year for the past 10 years. Additionally, there have been confirmed cases of individuals building their own replicas.
  • Please note that this 300 figure does not include potential demand.

2. The estimated user base for digital simulations of the Deacy Amp is over 1,000 individuals.
- On Amplitube's preset sharing platform (ToneNET), approximately 1,200 downloads of presets labeled "Deacy" have been observed (as of the posting date of this message).
https://www.tone.net/amplitube/search/?q=deacy

Note: In addition to the criteria listed above, Fractal's decision-making criteria may include “contribution to the technical roadmap." – in other words, for example, “whether implementing this request may have ripple effects across Fractal's entire platform?” Unfortunately, I cannot provide a clear answer to this point.

Question 9: "Products like xxx have already released decent simulations of the Deacy Amp. Wouldn't it be better to use those?"
Answer: Some guitar amp modeling platforms indeed offer models of the Deacy Amp. However, evaluating their performance often involves subjective factors, which may not lead to productive discussions. Therefore, I will refrain from discussing their performance here.

The reasons for requesting the simulation of the Deacy Amp on Fractal's platform, despite the availability of competing products, are as follows:
1. Continuous improvement for accuracy:
- Fractal consistently works on improving the absolute accuracy of its amp modeling algorithms through iterative updates. They have continuously discovered and implemented various "unknown" areas for improvement in the past and are expected to do the same in the future.
2. Significance of inheriting guitar history:
- Developing a full digital twin of the Deacy Amp is considered a highly meaningful project for inheriting an important legacy in guitar history for future generations. I believe that Fractal is best positioned to accomplish this project in the most optimal way.

IV. Presentation of This Request
Question 10: "What is the intention behind such an unusually long post? It seems like you're trying to pressure Fractal into fulfilling your demands, which feels inappropriate."
Answer: I apologize for the lengthiness of the post. There is absolutely no intention to pressure Fractal. I made this lengthy post to provide as much information as possible for Fractal to discuss and make informed decisions and alleviate any concerns they may have.
Even if Fractal decides not to implement this request despite my efforts, I will respect that decision. Furthermore, if additional information is needed, I am more than willing to cooperate to the best of my abilities.

This is the end of my posts. I apologize for the lengthiness of the post.

Disclaimer:
The accuracy of the information contained in my posts cannot be guaranteed. Additionally, please note that the development challenges outlined herein are merely illustrative and may not cover all aspects.
 
I remember Brian May telling in a recent interview that despite several attempts, nobody was able to capture the tone of deacy.
 
oacikgoz said:
I remember Brian May telling in a recent interview that despite several attempts, nobody was able to capture the tone of deacy.
Click to expand...
Thank you for your comment. I understand the point raised in the comment, which suggests that the replica of Knight Audio Technologies' Deacy Amp does not faithfully reproduce the tone of the original Deacy Amp, and thus may not be suitable as a reference for creating simulation models.

Only Brian knows his true intentions. However, based on the following information, it can be inferred that Brian believes Knight Audio Technologies' replica meets an acceptable level of accuracy to be used a substitute for the Deacy Amp:
- Guitar Interactive Magazine Issue 40 reported Brian's participation in a blind test between Knight Audio Technologies' replica and the original Deacy Amp, where Brian chose the replica as sounding like his original.
https://shop.brianmayguitars.co.uk/...itar Interactive - Super Special Rhapsody.pdf
(from page 118)
Eventually the finished replica was sat with Brian’s original Deacy, and Brian took part in a “blind” test, resulting in him choosing the replica when asked which one was his original!
Click to expand...

- Pete Malandrone, Brian's tour roadie, testified that Knight Audio Technologies' Deacy Amp replica is being used in gigs.
 
unix-guy said:
I didn't read every word but you certainly get an A for effort!

This has got to be the most detailed and thoroughly prepared request ever presented in a Wish.
Click to expand...
Thank you for your comment. I considered the decision-making process for Fractal Audio Systems regarding whether to add a model of an amplifier as akin to a judgment call on a kind of technological investment, especially in the case of such eccentric models. Therefore, I felt it important to provide as much information as possible that I would find necessary when making such judgments.
However, I don't believe every request needs to be as detailed as this one. Instead, I appreciate the atmosphere on this forum where everyone feels comfortable posting various requests casually.
 
frac-taro said:
Thank you for your comment. I understand the point raised in the comment, which suggests that the replica of Knight Audio Technologies' Deacy Amp does not faithfully reproduce the tone of the original Deacy Amp, and thus may not be suitable as a reference for creating simulation models.

Only Brian knows his true intentions. However, based on the following information, it can be inferred that Brian believes Knight Audio Technologies' replica meets an acceptable level of accuracy to be used a substitute for the Deacy Amp:
- Guitar Interactive Magazine Issue 40 reported Brian's participation in a blind test between Knight Audio Technologies' replica and the original Deacy Amp, where Brian chose the replica as sounding like his original.
https://shop.brianmayguitars.co.uk/user/reviews/pdf/2016-03 Guitar Interactive - Super Special Rhapsody.pdf
(from page 118)


- Pete Malandrone, Brian's tour roadie, testified that Knight Audio Technologies' Deacy Amp replica is being used in gigs.
Click to expand...

I realized one thing over several years, Brian May is not only great as a musician, he’s great in business :) to your point, he does mention explicitly that Knight Audio captured the tone in the clip below. Start around 2:00

 
Last edited:
One more thing, the only adjustment this amp has is “battery” power. Apparently Brian likes it with low battery. Knight Audio seems to have emulated this with a knob. Curious if it corresponds to one of the advanced power amp settings.
 
oacikgoz said:
One more thing, the only adjustment this amp has is “battery” power. Apparently Brian likes it with low battery. Knight Audio seems to have emulated this with a knob. Curious if it corresponds to one of the advanced power amp settings.
Click to expand...
I believe your point can be broken down into two concerns, and I'd like to answer each of them:

1. Is there a parameter equivalent to adjusting the supply voltage from the battery to the Deacy Amp?
I suspect the "Variac" parameter in the Power Supply tab might correspond to this.
https://wiki.fractalaudio.com/wiki/index.php?title=Amp_block#VARIAC
* There could be technical questions such as whether "Variac" parameter can adjust the voltage range of the battery or simulate voltage adjustment in a DC power supply. Unfortunately, I'm not adequately equipped to provide answers to these questions as my knowledge of the specifications of the "Variac" parameter is limited.

2. Is it possible to implement the Authentic mode of the Tone Control Display appropriately for "Deacy Amp" model, when the "Variac" parameter cannot be displayed there?
When implementing the model of the "Deacy Amp," I don't believe it's necessary to display the "Variac" parameter in the Authentic mode of the Tone Control Display.
  • The authentic implementation of "Authentic" mode for Deacy Amp model would be to have no control. In fact, it's after 2010s that adjustment of the supply voltage to the "Deacy Amp" becomes available to Brian thanks to Knight Audio Technologies' "Deacy Amp Battery Simulator."
  • Personally, I don't believe the "Deacy Amp" necessitates bold voltage adjustments to be functional. In fact, my preferred supply voltage is the nominal 9V of a PP9 battery.

I'm considering offering my 'Deacy Amp Battery Simulator' to Fractal so they can reproduce the behavior of voltage changes in the Deacy Amp.
 
frac-taro said:
I believe your point can be broken down into two concerns, and I'd like to answer each of them:

1. Is there a parameter equivalent to adjusting the supply voltage from the battery to the Deacy Amp?
I suspect the "Variac" parameter in the Power Supply tab might correspond to this.
https://wiki.fractalaudio.com/wiki/index.php?title=Amp_block#VARIAC
* There could be technical questions such as whether "Variac" parameter can adjust the voltage range of the battery or simulate voltage adjustment in a DC power supply. Unfortunately, I'm not adequately equipped to provide answers to these questions as my knowledge of the specifications of the "Variac" parameter is limited.

2. Is it possible to implement the Authentic mode of the Tone Control Display appropriately for "Deacy Amp" model, when the "Variac" parameter cannot be displayed there?
When implementing the model of the "Deacy Amp," I don't believe it's necessary to display the "Variac" parameter in the Authentic mode of the Tone Control Display.
  • The authentic implementation of "Authentic" mode for Deacy Amp model would be to have no control. In fact, it's after 2010s that adjustment of the supply voltage to the "Deacy Amp" becomes available to Brian thanks to Knight Audio Technologies' "Deacy Amp Battery Simulator."
  • Personally, I don't believe the "Deacy Amp" necessitates bold voltage adjustments to be functional. In fact, my preferred supply voltage is the nominal 9V of a PP9 battery.

I'm considering offering my 'Deacy Amp Battery Simulator' to Fractal so they can reproduce the behavior of voltage changes in the Deacy Amp.
Click to expand...
ChatGPT?
 
Here's a brief demo of my Deacy Amp replica for reference. My playing is not good at all, but I believe it can help assess whether the replica produces the correct sound.


oacikgoz said:
ChatGPT?
Click to expand...
As you pointed out, I'm using ChatGPT for the English translation. My proficiency in English is limited, and I thought using ChatGPT would reduce the risk of me misunderstanding or my posts conveying unintended meanings. I apologize if I seemed like a malicious bot or troll causing discomfort. I compose my posts in my native language and only use ChatGPT for translation purposes.
 
Would be a great addition but I'd dare to say this would be something where "there's something in analog that can't replicate on digital" discourse has the point. I use Amplitube Brian May for Deacy tone but it's just because it's the only Deacy sim available. Even with Cliff's past achievement, I'd still be surprised if he managed to implement a decent Deacy sim.
 
km 202257: "Even with Cliff's past achievement, I'd still be surprised if he managed to implement a decent Deacy sim."
FractalAudio: "Hold my beer guitar..."

Maybe? ;)
 
Peavey Herman said:
km 202257: "Even with Cliff's past achievement, I'd still be surprised if he managed to implement a decent Deacy sim."
FractalAudio: "Hold my beer guitar..."

Maybe? ;)
Click to expand...
You gotta learn how to use the quote feature on the forum, man ;)

I am suspecting maybe @km 202257 was trying some (not so) subtle reverse psychology in his post...
 
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