Amp Build Diary

[Passinwind]

[quote name='VTypeV4' timestamp='1414892464' post='2594495']
I'm reasonably happy understanding valve gear and it's details but Switch-mode supplies, multi-vibrator circuits and Class D amplifier operation is somewhere just beyond me at this time.
[/quote]

There's a pretty good technical thread on Talkbass by Bobby Baldwin, an amp engineer at Peavey who actually designs Class D amps from a white sheet: [url="http://www.talkbass.com/threads/class-d-illustrated-lots-of-pics.1083366/"]http://www.talkbass....f-pics.1083366/[/url]

I haven't taken the dive into that deep pool as far as DIY building just yet, but in time I hope to. I am definitely looking forward to seeing how Chienmortbb's builds evolve -- there are just so many compromises and tradeoffs involved with this sort of project, and at some point one just has to pay their money, make smoke, and see what happens. After I built my amp I revised both preamp circuit boards, and also designed a bespoke power supply, so it's not as if Chienmort will just be building up a known-good design from a blueprint, although we certainly both hope it will play out something like that. A good part of the end result will depend on his own choices and tweaks. I have tried to make my design pretty accommodating to modifications...we'll see how that goes.

Edited November 4, 2014 by Passinwind

[6v6]

[quote name='Passinwind' timestamp='1415130435' post='2597096']
so it's not as if Chienmort will just be building up a known-good design from a blueprint, although we certainly both hope it will play out something like that. A good part of the end result will depend on his own choices and tweaks. I have tried to make my design pretty accommodating to modifications...we'll see how that goes.
[/quote]

There have been references to your design but no links, for those of us who've not followed the TB threads closely (I had a quick look a the link from post #6 but didn't spot the schematic), can you share links to the design's you're referring to and have been collaborating on?

[Passinwind]

[quote name='6v6' timestamp='1415139554' post='2597224']
There have been references to your design but no links, for those of us who've not followed the TB threads closely (I had a quick look a the link from post #6 but didn't spot the schematic), can you share links to the design's you're referring to and have been collaborating on?
[/quote]

I'm not planning on posting an actual schematic at this time, but I will be happy to show build pics, component details, block diagrams, performance measurements, and modeled behavior of the various bits. Talkbass messed up their links quite badly with the software "upgrade" a few months ago, unfortunately.

This thread shows the evolution from a modified ESP (Rod Elliot) board to my own basic preamp design: [url="http://www.talkbass.com/threads/oh-no-another-diy-rack-preamp-thread.600314/"]http://www.talkbass....-thread.600314/[/url] . The beginning of the thread linked above details the added daughtercard incorporating a variable high pass filter and a one band fully parametric EQ. So there are 6 basic modules available thus far:[list=1]
[*]Input gain stage and active bass and midrange control, optimized for active basses
[*]Parametric equalizer
[*]Passive treble control, boost/cut
[*]Effects send/receive/aux input
[*]Variable high pass filter, 2nd order fixed + 2nd order variable
[*]Final gain stage/line driver
[/list]
Some of the modules can be placed in varying spots in the signal chain, but my first build is in the order listed. I made the PEQ and HPF modules bypassable by switches on the front panel. I think Chienmort is contemplating using a switchable mid frequency as well.

My website at www.passinwind.com has a basic overview of many of my more recent DIY builds as well, along with a few sound clips. There are also a few sound clips here: [url="https://soundcloud.com/passinwind/sets/diy-cab-preamp-demo-clips"]https://soundcloud.c...eamp-demo-clips[/url]

Edited November 4, 2014 by Passinwind

[Chienmortbb]

Yes my old HH amps had a mid centered on 650Hz and I have got used to that so the mid control will be switchable on mine. Now stevie has shown me how to put pictures up, I will start tomorrow but in the meantime I will elaborate on the stages of the "preamp".[list=1]
[*]Input gain stage and active bass and midrange control, optimized for active basses -[i] I will be modifying this to take passive basses although many passive basses have been played througn the preamp and I hear that they sound great.[/i]
[*]Parametric equalizer. [i]- This is a fully parametric EQ with contol over Frequency, Q, and Level[/i]. [i]The Semi-parametric EQs as fitted to many commercial amps have fixed Q.[/i]
[*]Passive treble control, boost/cut. [i]I believe that the The passive treble control is less noisy than an active one and more musical but [b]perhaps Charlie could comment.[/b][/i]
[*]Effects send/receive/aux input. - [i]Hopefully needs no explanation.[/i]
[*]Variable high pass filter, 2nd order fixed + 2nd order variable - [i]Think of a Thumpinator or FDeck's HPF. Has the dual purpose of controlling excessive cone movement below a cabinet's tuned frequency and also taking the "boom" out of those nasty rooms.[/i]
[*]Final gain stage/line driver - [i]The output stage to the Power Amp[/i] .
[/list]
More tomorrow.

Edited November 4, 2014 by Chienmortbb

[VTypeV4]

Fascinating, as is the link about Class D operation.. Top thread chaps!

[Passinwind]

[quote name='Chienmortbb' timestamp='1415144089' post='2597289']
[b]Passive treble control, boost/cut.[/b] [i]I believe that the The passive treble control is less noisy than an active one and more musical but perhaps Charlie could comment.[/i][/quote]

This is something I first worked out in one of my tube preamp builds a few years ago, and it's the closest thing to 'secret sauce' in my designs. It comes from some very old tube gear design manuals, and the fact that it's passive is only half the story, because its placement in a different stage than the bass and mid controls keeps it from interacting with those controls in potentially undesirable ways, intermodulation distortion and slew limiting for instance. Moving it back in the signal chain a few stages also keeps the earlier stages from further amplifying treble boost noise and potentially reduces distortion generated in those stages. As always, the devil's in the details though. I spent many hours in LTspice trying to find a workable solution, and was kind of shocked when it turned out to sound pretty good. My intention is that you can turn it all the way up if desired, and it still sounds fine, with very minimal hiss artifacts. When cranked it actually redacts to more or less a classic CD horn EQ in the 4K-12K zone, which works well with my DIY cabs that use pretty much pro audio caliber compression drivers. Here are the frequency response models from treble control full-down to full-up:




By standard marketing speak you might see this spec'ed as a +10dB shelving filter at 25K on the boost side, but as the graph shows, marketing speak often leaves a lot to be desired.

[quote][b]Variable high pass filter, 2nd order fixed + 2nd order variable[/b] - [i]Think of a Thumpinator or FDeck's HPF. Has the dual purpose of controlling excessive cone movement below a cabinet's tuned frequency and also taking the "boom" out of those nasty rooms.[/i][/quote]

Yes, both those purposes are part of the classic design brief. In my design I have also attempted to make the HPF and bass control highly interactive, but hopefully in an intuitive fashion. Here are some compound curves showing bass control boosted 1/8 turn clockwise and left there, then high pass control swept from full up (least cut) to full counterclockwise (most cut):




As you can see, peak bass boost can move between 42Hz and 240Hz, and many other curves are readily obtained as the bass control applies various boosts and cuts. Again, I was a bit surprised that I just did the model on my computer, built the circuit, and it measured and sounded fine right off the bat. I made a bit of a mess with the first circuit board design, but I am still pretty new at that aspect and fortunately I have pretty decent board rework skills learned over the years through a series of day jobs fixing and modding audio gear and other electronic widgets. Hopefully the new boards are glitch free, they seem to be from the little bit of testing I've done on my bench. Having someone else build up some of my designs should be very useful in refining my craft, which is the main point of doing DIY builds in my case.

Edited November 5, 2014 by Passinwind

[6v6]

[quote name='Passinwind' timestamp='1415142587' post='2597271']
I'm not planning on posting an actual schematic at this time, but I will be happy to show build pics, component details, block diagrams, performance measurements, and modeled behavior of the various bits.
[size=4][/quote][/size]

[size=4]Ok, fair enough.[/size]

[size=4]For me that devalues this thread quite a bit, because without specifics like schematics, it becomes a build commentary of an effectively private collaboration between you and [/size][size=4] Chienmortbb, rather than an actual build diary.[/size]

[size=4]That said, I'm sure the other details you mention will be interesting. [/size]

[LukeFRC]

[quote name='6v6' timestamp='1415269830' post='2598529']
[/size]

[size=4]Ok, fair enough.[/size]

[size=4]For me that devalues this thread quite a bit, because without specifics like schematics, it becomes a build commentary of an effectively private collaboration between you and [/size][size=4] Chienmortbb, rather than an actual build diary.[/size]

[size=4]That said, I'm sure the other details you mention will be interesting. [/size]
[/quote] equally though if I had a bill fitzmaurice cab build thread, bill himself might even join in but I dont think anyone would expect his design build plans provided for free....

[6v6]

[quote name='LukeFRC' timestamp='1415279944' post='2598689']
equally though if I had a bill fitzmaurice cab build thread, bill himself might even join in but I dont think anyone would expect his design build plans provided for free....
[/quote]

I never said anything about free - I'm just saying that unlike the 1x12 cab build diary this is supposed to be inspired by, if the key details of build specifics are private between only two thread participants, nobody can really benefit from the experience if they want to follow a similar path.

For example, if I read a BFM build thread and like it, I can just pay Bill for his plans - I'd have no problem, for example, paying Passinwind for a PCB if his design sounds nice, but that's not what's being proposed AIUI, perhaps I am misunderstanding.

Anyway - like I said, fair enough, I'm sure the pictures, graphs and random design musings will be most informative and interesting.

[Chienmortbb]

The case for the defence?
[IMG]http://i59.tinypic.com/2zhqdk5.jpg[/IMG]

Edited November 6, 2014 by Chienmortbb

[Passinwind]

[quote name='6v6' timestamp='1415269830' post='2598529']
[size=4]Ok, fair enough.[/size]

[size=4]For me that devalues this thread quite a bit, because without specifics like schematics, it becomes a build commentary of an effectively private collaboration between you and [/size][size=4] Chienmortbb, rather than an actual build diary.[/size]

[size=4]That said, I'm sure the other details you mention will be interesting. [/size]
[/quote]

This is Cheinmortsbb's thread and if he cares to post a schematic for whatever form his own builds eventually take (or even when he just gets to actually making smoke) we will jump off that bridge when we get to it. My boards and design are just a starting point, not a destination.

I was deeply involved in the fEARful cabinet R&D and early build threads, and frankly, that just became so tedious after a while. I build stuff for myself as a hobby to satisfy my own quirky needs, try to help a few friends along the way, and have zero interest in being like BFM or Greenboy or Rod Elliot. I'm new to the Basschat culture and have not seen the cab build thread yet, so I'll take a look at it presently. I sort of envisioned any role I might have in this thread as teaching how to catch a fish, not giving everyone a fish -- things like modeling your own circuits in LTspice and laying out circuit boards in KiCad, for instance. I'm not looking to sell anything BTW, but if Chienmort gets something worked up that others really want to build, I could help make that happen via open share circuit boards available straight from my board fabricator. You guys do realize how crazy-expensive this kind of thing is to build though, right?

Edited November 6, 2014 by Passinwind

[LukeFRC]

[quote name='6v6' timestamp='1415281370' post='2598711']
nobody can really benefit from the experience if they want to follow a similar path.

[/quote]
fair enough

[LukeFRC]

[quote name='Passinwind' timestamp='1415295476' post='2598946']
This is Cheinmortsbb's thread and if he cares to post a schematic for whatever form his own builds eventually take (or even when he just gets to actually making smoke) we will jump off that bridge when we get to it. My boards and design are just a starting point, not a destination.

I was deeply involved in the fEARful cabinet R&D and early build threads, and frankly, that just became so tedious after a while. I build stuff for myself as a hobby to satisfy my own quirky needs, try to help a few friends along the way, and have zero interest in being like BFM or Greenboy or Rod Elliot. I'm new to the Basschat culture and have not seen the cab build thread yet, so I'll take a look at it presently. I sort of envisioned any role I might have in this thread as teaching how to catch a fish, not giving everyone a fish -- things like modeling your own circuits in LTspice and laying out circuit boards in KiCad, for instance. I'm not looking to sell anything BTW, but if Chienmort gets something worked up that others really want to build, I could help make that happen via open share circuit boards available straight from my board fabricator. You guys do realize how crazy-expensive this kind of thing is to build though, right?
[/quote] just to say - it's good to have you around

[Passinwind]

[quote name='LukeFRC' timestamp='1415302584' post='2599081']
just to say - it's good to have you around
[/quote]

Thanks Luke. I have a ton to learn about this DIY affliction myself and just looking through Chienmort's eyes at module and parts suppliers outside of the US, import duties, etc., has been quite an eye opener.

I used the ICE 500ASP module in my last build, after gigging for several years with an OEM plate amp from SpeakerPower using the 1000ASP. You can find either of those modules fairly easily on a few DIY forums, but B&O give no tech support and it's a bit of a gamble at best. I like the looks of the 700 watt Hypex module powered my their 1200 watt SMPS a lot, but it is not cheap by any means.

Edited November 6, 2014 by Passinwind

[Passinwind]

[quote name='Chienmortbb' timestamp='1415285458' post='2598773']
The case for the defence?[/quote]

Looks roomy enough to work in easily, I like that. I'm currently doing a 1/2 rack size preamp-only build in this case:

[LukeFRC]

[quote name='Passinwind' timestamp='1415307197' post='2599139']
Thanks Luke. I have a ton to learn about this DIY affliction myself and just looking through Chienmort's eyes at module and parts suppliers outside of the US, import duties, etc., has been quite an eye opener.

I used the ICE 500ASP module in my last build, after gigging for several years with an OEM plate amp from SpeakerPower using the 1000ASP. You can find either of those modules fairly easily on a few DIY forums, but B&O give no tech support and it's a bit of a gamble at best. I like the looks of the 700 watt Hypex module powered my their 1200 watt SMPS a lot, but it is not cheap by any means.
[/quote] some of the moduals are cheaper to get I think if you buy a PA amp based around them and cannibalise it!

[Passinwind]

[quote name='LukeFRC' timestamp='1415308287' post='2599159']
some of the moduals are cheaper to get I think if you buy a PA amp based around them and cannibalise it!
[/quote]

Yep, especially if there is an OEM version and a separate DIY-friendly one, as is the case with Hypex. Someone on TB gutted a Genz amp and put in an older Eden front end, and I did consider just buying a G-K or Kustom and using the power module. It cost me around $300USD to get the 500ASP and all the needed wiring harnesses, back end inductive filters, etc. There's an old designer's manual for the ASP series that one can find online, which was hugely helpful. I used to do sanctioned warranty service for many brands of pro audio and musical instrument electronics, so I often at least know who to ask when something's clearly over my head, which happens fairly often.

Edited November 6, 2014 by Passinwind

[Chienmortbb]

Just to clear things up a little, this was never meant to be a build your own bass amp thread, I was just wanting to explain the thinking behind how I am going about specing my own home brew amp. It is a learning process and I thought others could learn along with me, just as I learnt from the 1 X 12 Cab build diary. If everyone is happy with that I will continue.

Edited November 6, 2014 by Chienmortbb

[6v6]

[quote name='Chienmortbb' timestamp='1415313987' post='2599228']
Just to clear things up a little, this was never meant to be a build your own bass amp thread, I was just wanting to explain the thinking behind how I am going about specing my own home brew amp. It is a learning process and I thought others could learn along with me, just as I learnt from the 1 X 12 Cab build diary. If everyone is happy with that I will continue.
[/quote]

Aww man, I feel bad now. [size=4]Apologies if my demands appear unreasonable - it wasn't my intention to derail this thread [/size] [size=4] [/size]

[size=4]H[/size][size=4]onestly, I thought my original request for details would result in a "sure, here's a link to the thread with the preamp schematic on TB", but if that's not the way this is going down, (again) fair enough.[/size]

[size=4]In my defence, I'm an engineer, and thus immediately want to discuss implementation specifics. That's my affliction though, I can't help it! [/size]

[size=4]Good luck with the build.[/size]

[Chienmortbb]

To be honest 6V6 I am glad you are on board. Charlie and I are both Electronic Engineers by trade and it is great to hear other opinions, even if you don't always agree with them initially. I will post a few more pictures of the case innards and the preamp PCBs tomorrow and I am close to choosing my power amp.

Edited November 7, 2014 by Chienmortbb

[Passinwind]

[quote name='6v6' timestamp='1415351689' post='2599415']
Aww man, I feel bad now. [size=4]Apologies if my demands appear unreasonable - it wasn't my intention to derail this thread [/size]

[size=4]H[/size][size=4]onestly, I thought my original request for details would result in a "sure, here's a link to the thread with the preamp schematic on TB", but if that's not the way this is going down, (again) fair enough.[/size]

[size=4]In my defence, I'm an engineer, and thus immediately want to discuss implementation specifics. That's my affliction though, I can't help it! [/size]
[/quote]

No hard feelings here, and I don't think your request is unreasonable at all. I first met Chienmort online when he wanted to know about exactly how I added a midrange control circuit to an older bass preamp build I did using Rod Elliot's Project 94 as a jump-off. Since there are really not a whole lot of good dedicated bass preamp DIY projects detailed online, my M.O. has often been to just steal circuit bits off commercial schematics, albeit usually with mods by the time I get something I'm happy with. That just might have something to do with my reluctance to post schematics of some of my builds...

I was schooled as a electronics technician actually, but a number of my day jobs over the years have made me hit the books pretty hard to go a little beyond that. It's often a fine line anyway, in my experience.

Edited November 8, 2014 by Passinwind

[Passinwind]

[quote name='Chienmortbb' timestamp='1415402080' post='2600106']
I will post a few more pictures of the case innards and the preamp PCBs tomorrow and I am close to choosing my power amp.
[/quote]

Do you hate me yet? Procuring parts has proven to be much more challenging for you than I ever would have expected, especially given that Wima is a German company and that getting most of their caps in the US couldn't be much easier.

I'm currently working through a test build of the new preamp circuit boards myself. Should be making noise within a few days. These boards cost me around $20 apiece for just the raw boards, but I have to buy three at a time from the vendor I'm using, who is more or less local to me:



The opamps going into in the top board are pretty expensive and won't get installed until the last minute, no point in roughing them up as things get shuffled around. I have set things up so stacking is easy, and also made a modular arrangement that allows reordering stages if desired. That allows options like having the high pass filter affect the EFX send, or not.

Edited December 11, 2014 by Passinwind

[LukeFRC]

Pretty

[Passinwind]

[quote name='LukeFRC' timestamp='1418327857' post='2629303']
Pretty
[/quote]

Thanks. Lots of people seem to dig the purple color, but that's actually the only option from this vendor.On my most recent tube preamp build I used [url="http://passinwind.com/Tech/PW6B_PCBs.JPG"]red audiophool resistors[/url], but they proved to be a little fragile during rework and are also far too expensive to use routinely as far as I'm concerned.

Edited December 12, 2014 by Passinwind

[Chienmortbb]

Thanks to passinwind for keeping this thread going. My wife has picked up a post op infection and we have both had Man Flu (her words not mine).

The PCBs are superb quality and although there are cheaper suppliers, OSH Park really have a quality product.

Since my last post I have chosen and purchsed the power unit.


I looked at all the usual candidates for an integrated Power Amp and Switched Mode Power Supply. As a recap my minimum spec was:[list=1]
[*]Power Output 250 Watts into 8 ohms at less than 1% distortion
[*]Power Output 500 Watts into 4 ohms at less than 1% distortion.
[/list]
The manufacturers looked at were:[list]
[*]ICEPower (B & O)
[*]Anaview/Abletec
[*]Connexelectronic
[*]BoYoHo
[/list]
ICEPower are probably the market leaders and supply to many manufacturers including Kustom for Bass Amps. ICE Power only supply OEM (Original Equipment Manufacturer). They are difficult to get in the UK and most of them for sale on EBAY are from the USA. As already outlined, import costs make the ICEPower very expensive in the UK.

Anaview are the power units for many too including Ashdown. They are available from Profusion in the UK but a price rise just before I ordered meant that I could not afford the Anaview unit I would have liked.

Connex Electronic are a small Chinese company that has built a very good reputation for quality and price in HiF circles. They have a few likely cndidates in their range but when I tried to order another item from them before, my order was refusd and my money refunded as I was blamed for a flame war against them started by another Brit. Connex products are distributed in Europe but none of the distributors stock the integrated modules.


BoHoYo are another Chinese Company, seemingly bigger than Connex and have a European Distributor in the Netherlands. Smart Audio.