Hey Tommy, any plans to make a Class D preamp?

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jseipp

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #60 on: 12 Mar 2018, 10:14 pm »
I’ve been away from the boards for awhile and have been doing a little catch-up reading.  What strikes me about this thread and the current Kickstarter campaign is how responsive Digital Audio Company has been to their customers from the beginning of the Cherry Amplifier brand almost ten years ago and accelerating into the present.  I have participated in all four previous Kickstarters and have profited through an immense amount of musical enjoyment as a result. 

I am really impressed with the constructive communication that constitutes this thread and with how quickly it has resulted in the design of a new product intended to increase the flexibility of the DAC products already in use.  This Kickstarter campaign once again offers newcomers the opportunity to purchase existing products at a significant discount as well.  I’m probably most impressed with the additional focus on offering upgrades for products purchased through the years and across the entire range, adding to the value of DAC products as long-term investments in making customers’ music sound as fresh as possible.

The continual innovations introduced through the DAC website and through each Kickstarter campaign demonstrate what talented design work can accomplish when focused on the goal of sharing with customers the very best sound while avoiding unnecessary frills at prices that reflect the efficiency of direct sales.  What may not be obvious is the personal service Tommy and Digital Audio Company provide.  If anyone is curious about the products being offered via the Kickstarter campaign I highly recommend getting in touch with them and having any questions you may have answered.  You’ll find yourself speaking with a true music enthusiast who happens to build equipment that makes the pursuit of the best sound so very enjoyable.

No association with or incentive from the company, just a message intended to encourage anyone who is considering it to find out for themselves if the products currently on offer on Kickstarter are a fit for their systems.  When I’ve found the source of something truly special, it’s a pleasure to spread the word to others!   

AmpDesigner333

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #61 on: 13 Mar 2018, 03:19 am »
Reading all the previous posts, it looks like there is real interest in DPA, ADC, and continued growth over at Digital Amplifier Company! Glad to hear it because over all the years in this hobby and all the gear that passed though my hands, its Tommy's designs which have finally delivered the goods!  DACDAC's, STM's, and Maraschino's have all exceeded my expectations. And due to that, I'm sure that once the feature set and product function are worked out, the forthcoming DPA will set a new standard for transparency and performance in our systems.

My .02 is this.  As I get older, and things like retirement savings and children's educations continue to sap funds from my disposable income, it becomes increasing evident that simplifying the audio chain leads to saving money, and less chance of adding deleterious connections.  An example of this would be the now additional SPDIF cables required to connect the DPA. I have found audible benefit in using a Nordost Blue Heaven to drive my DACDAC's SPDIF.  If the DPA is a completely stand alone device then it adds considerably to the price for me to add another expensive SPDIF cable.  And once I've heard that it works, I cant un-hear it...  Same goes for those who tinker with outboard power supply upgrades. Everything but the amps in one box sure makes alot of sense to me.

So, my suggestion is a modular approach.  Thinking really off the wall ideas here.  Tommy has thus far been quite an innovator in not spending wastefully on casework, and keeping a family look to the product line.  Keeping functionality in separate boxes may also have a sonic benefit, but then the cabling issues arise.  My stake would land at an option to have the DPA, DACDAC, and good power supply in one fullsize chassis.  Obviously the boards themselves would remain the same, but the option to have everything in one case would really be a mature and cost effective move. Maybe current DACDAC users could enjoy an exchange or trade up program. we'd all want to do that for the forthcoming DACDAC-2 anyway. 

Otherwise, remote & physical volume knob (encoder)..... SPDIFon RCA & BNC & Toslink would be mandatory I think.

And Tommy... I think you are on to something with the 2nd SPDIF output.  It would be great to drive a subwoofer without fear and complication of the rca's on many subs grounding out the main amplifier inputs (as we've discussed).. Would it be possible to slightly bias one SPDIF output a little higher than the other?  I'm thinking here of a user with 2 DAC's and 4 Maraschinos, but the speakers/subs being driven are different sensitivities... Being able to boost or cut one output over the other could really lend better integration of subs for advanced users!
Regarding the second digital output (each is two channels), we plan to do almost exactly what you're saying, but can't promise any specifics until we have the hardware completed.  Code generation (VHDL) can happen during the PCB assembly lead time.  Individual functions (filters, interfaces, etc.) are already available from past projects.  Some of the processing we plan to do wouldn't be possible with a reasonably priced DSP or even matrix of DSPs.  This is one reason we're using an FPGA.  We can control every last bit precisely this way, removing potential glitches.  Thanks for your kind words!

-Tommy O

AmpDesigner333

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #62 on: 14 Mar 2018, 03:26 am »
One of the "stretch goals" of our current Kickstarter (http://kck.st/2CH4sLB) is to add USB and optical inputs to the DPA.  We haven't decided how many DPA orders will cover the added expense yet.

However, since inexpensive optical to coax converters are readily available, and we already make the Cherry USB, we are torn on this issue!  Here's where your opinion steers development like no place else....

Some have even asked for bluetooth (can't believe I just typed that word).  I have kids, and they love being able to "broadcast" their music to a decent audio system, even though BT's compression is certainly audible as witnessed by many comparisons with the STM ---- headphone jack (from a phone that still has one) vs BT is smack-you-in-the-face obvious for most music and even dialog.  Well, we have no plans to "go there" yet.  When is BT's next update?  Maybe when it's able to transmit stereo 24/96.  I'd be happy with lossless 16/44.  The Cherry BT is on hold indefinitely, but if we were to make something like that, it would have a digital output only, coax.

So, for now we wait to see the results of our Kickstarter.  Several of the "CUSTOM" rewards include the DPA.  We added some demo amps today, by the way.  Something in the rewards may shock you.  Hint: there's only ONE.  Thanks as always for taking the time to visit our circle.

AmpDesigner333

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #63 on: 26 Mar 2018, 02:28 am »
Only 20 hours left:
http://kck.st/2CH4sLB

We are over 440%!   Sooooo close to 500% where the Cherry DPA will get USB and optical inputs. This is what we call a "stretch goal". 

AmpDesigner333

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #64 on: 27 Mar 2018, 01:28 am »
Thanks to our awesome backers, we reached 511% !

So, as  promised, the Cherry DPA will include USB and optical inputs (coax too).

We are honored by the response and look forward to building a wonderful product.

-Tommy O  :D :D :D :D

AmpDesigner333

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #65 on: 14 May 2018, 09:15 pm »
Sorry if this is OT, and I'm pretty sure this would require an integrated amp due to EMI and such, but...

Will the industry eventually go the route of converting any type of input to PWM and then feeding that signal directly into a PWM amplifier?
In other words...analog/pcm/???--->pwm--->PWM--->filter--->speaker.

Just curious.

Mike
Mike,

I was reviewing this thread and saw your post.  Looks like your question wasn't addressed, so....

Performance would be limited by such a device because the PWM at signal level would only be applicable to open loop PWM amplification.  That would result is performance limitations, such as higher THD+N and significantly lower SNR.  We have developed open loop Class-D amplifiers in the past.  In fact, ST Microsystems built their Class-D chip set around open loop "direct digital" Class-D patents that I wrote in the 90s.  We went on to build improved designs, but none that could outperform our hybrid analog/digital modulation technique used in Cherry Amps.

We have tossed around the idea of a new digital-input-only amp for decades.  However, this would probably be using an all-digital version of our modulation technique with super-high-performance A/D converters used for multi-level feedback.  Our target SNR for such a device is 120dB.  Not an easy feat, but our current 130dB+ DAC DAC 2 HS driving a 120dB SNR MEGAschino (or much lower cost Stereo Maraschino) amp directly can achieve the same level of performance, and these products are available now.  We don't do things for the sake of novelty, so we would need to achieve some performance advantage over our current products in order to reconsider.

Thanks for your excellent question.

-Tommy O

AmpDesigner333

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Design Update
« Reply #66 on: 26 May 2018, 02:25 pm »
We have one more major item to decide on....  The display.  We picked one that's graphic and OLED, but we're not sure if there's a MOQ associated with this part.  Since it's a holiday weekend here, the answers will need to wait until next week.

So, we have 4 inputs: COAX1, COAX2, OPT, and USB.  There are two coax outputs.  We plan to use this for a sub crossover (augment/supplement, selectable frequency, selectable phase) and maybe our headphone algorithm....  Maybe.  We're wondering if this will "force us" into a digital headphone amp.  Hmmmmm.  Sounds like fun !

We are also thinking of using an analog volume pot to control the digital volume.  Any thoughts?  I'm partial to knobs, especially the single turn type.

You guys are the KEY to making this product!  The Cherry DPA is a collaborative effort!  My sincere thanks for any suggestions, as always (:

BruceSB

Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #67 on: 30 Nov 2018, 03:01 am »
No posts for a while.
I wonder if we can have an update on how things are coming along?
Maybe even a picture?
I also wonder about the possibility of replacing one of RCA analogue inputs to a balanced input?
Thinking that there a number of good phono preamps with balanced outputs & anyway balanced good anyway?!
Another possibility is an additional analogue input that is balanced but that increases the price!
Thanks.
Bruce

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #68 on: 30 Nov 2018, 11:26 pm »
No posts for a while.
I wonder if we can have an update on how things are coming along?
Maybe even a picture?
I also wonder about the possibility of replacing one of RCA analogue inputs to a balanced input?
Thinking that there a number of good phono preamps with balanced outputs & anyway balanced good anyway?!
Another possibility is an additional analogue input that is balanced but that increases the price!
Thanks.
Bruce
Bruce,

We are planning an update very soon, to be broadcast "on all channels"....

In the meantime, I should mention that the Cherry DPA is a DIGITAL ONLY product.  Digital Audio in and out.  The Cherry DPA allows input selection, volume control with gain, an IR remote, and several DSP functions.  It is meant to drive one or two Cherry DAC DACs (version 1 or 2, TL or HS), although other DACs can be used.  Systems with direct DAC-to-amp drive will be enabled by the Cherry DPA even for non-volume-controlled sources (like CD transports).  We plan to offer a Cherry ADC for conversion to digital (most likely single ended inputs), although products that can handle this function at low cost are out there currently.  I'm very excited about the Cherry DPA!  Thanks for your kind post.

-Tommy O

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Re: Hey Tommy, any plans to make a Class D preamp?
« Reply #69 on: 19 Dec 2018, 03:02 pm »
Update: We are working hard on the design, and plan for production early 2019.

New panels!