This is a good status report from Rick, and he and I both appreciate the interest in this project. I am also anxious to receive the new boards with the soldered-on SOT-23 JFETs and evaluate it. Ditto the output board for the P230. I have a P230 just waiting for it.
I would like to underscore what Rick said about matching JFETs. The amplifier is quite forgiving of JFET matching, but it is desirable to keep the VAS bias current in an 8-12 mA range in this full complementary topology. Performance of the amplifier is virtually unaffected by VAS bias current in this range.
Ideally, blindly loaded JFETs will result in bias current that falls in this range. Moreover, I have devised a technique that can bring blindly loaded JFETs into spec for VAS bias current in the specified range, once again without degrading performance.
However, we decided that with pre-loaded JFETs soldered to the board (SOT-23 can be a PIA to solder or remove, as they are tiny), it would be best to do some rough binning of the JFET pairs to make life easier for the builder. It is important to note that the kind of JFET "matching" that is done is not for offset of one pair or the other by itself per se, but rather for the difference in offset between the N-channel and P-channel pairs. If both pairs had 10 mV offset in the same direction they would be perfectly matched in this sense and for this application.
Cheers,
Bob
OK, thanks Rick! I can understand your position, been there myself, will await further developments.
Bob, does this mean it's SOT-23 only, TO-71 is no longer an option? SOTs always pre-soldered? I'm kinda fond of the old-school metal cans, not for performance, but just for looks.
OTOH, am also comfortable soldering SMDs myself, it's part of the enjoyment!Sean
OK, thanks Rick! I can understand your position, been there myself, will await further developments.
Bob, does this mean it's SOT-23 only, TO-71 is no longer an option? SOTs always pre-soldered? I'm kinda fond of the old-school metal cans, not for performance, but just for looks.
Sean
Hi Sean,
The TO-71 is definitely still an option, just more expensive to buy. The board has through-holes for a socket or soldering of the TO-71 on the top of the board. The SOT-23 pads are on the bottom of the board. The SOTs will always come soldered with the board. Standard purchase is a board with the SOTs soldered on. I'm not sure what Rick's plans are for supplying boards without SOTs for use with the TO-71 devices.
Cheers,
Bob
I can offer boards only, easiest for me by far but you will be having to get parts from at least three suppliers. I think most would appreciate using a kit of parts that can not be bought at Mouser and have a link to a Mouser shopping cart for the bulk of the parts. The kit will only offer the jfets in Sot-23 soldered since I do not want to stock both jfet package types.
Last edited:
Thanks gentlemen, it's all clear now!
I can appreciate a "kit" of small parts for single source convenience, but I've never had a project that didn't require multiple sources, so I'm prepared for that.
I've put a lot of "kit" time in over the years (Eico, Knight, Heath, etc.), starting with tubes & point-to-point wiring thru etching my own PCBs for published schematics. The Haflers were a bit disappointing in that respect, not building so much as just assembling modules. I much prefer all DIY.
Looking forward!
Sean
Hi Sean,
It is a lot of time, lead forming, soldering, I just spent a good few hours pulling the components off the first prototype to transfer them over to a 2nd rev board. I have the time, so not an issue. I did not feel comfortable throwing out a board full of good components. Removing components from a board with plated thu holes, required me to use a small wire bridge to heat the leads up at the same time. The dip sockets, l used a hot air machine. Imo the hot air machine from Sparkfun was a much better investment over a dedicated de-soldering tool.
So I can say this project is as much fun as it is involved, I have done two DH-200’s that have been running for over a month of continuous operation each. I took pictures of every step in the process, so that I can share them on a google drive, with constructors. We put together very detailed build guides, theory of operation. We welcome feedback to improve these documents if we have overlooked or have not covered enough details. I can’t wait to get this out for interested participants.
Cheers Rick
It is a lot of time, lead forming, soldering, I just spent a good few hours pulling the components off the first prototype to transfer them over to a 2nd rev board. I have the time, so not an issue. I did not feel comfortable throwing out a board full of good components. Removing components from a board with plated thu holes, required me to use a small wire bridge to heat the leads up at the same time. The dip sockets, l used a hot air machine. Imo the hot air machine from Sparkfun was a much better investment over a dedicated de-soldering tool.
So I can say this project is as much fun as it is involved, I have done two DH-200’s that have been running for over a month of continuous operation each. I took pictures of every step in the process, so that I can share them on a google drive, with constructors. We put together very detailed build guides, theory of operation. We welcome feedback to improve these documents if we have overlooked or have not covered enough details. I can’t wait to get this out for interested participants.
Cheers Rick
Mono P230... too many ideas and options.
I bought and 'updated' my first XL600 with Musical Concepts new PA7 boards, also built it *true* dual mono. It sounds so fabulous, unparalleled driving my Maggies, which started an amplifier building and rebuilding frenzy... I started swapping boards and parts around, updated my "once DH" MC500 with a 2nd set of PA7 driver boards, making appreciable sonic gains at every turn. I cannibalized the Jensen 4-pole capped P230, in the front (image 1) it 'no longer exists' as shown is now one of the dual mono amps. It turned out that the 6 output versions greatly overshadowed any of the 200 / 220 versions I had built prior... with the speaker assortment that I have on hand... will admit to getting a little carried away... those here may truly understand this...
A virtue in owning a dozen assorted "Hafler amps", I can model so many concepts... compare them directly to one another. I have had ideas to build mono versions for some time (over 30 years) first had to pick a power supply, driver circuit and chassis which warranted such a build. The safest bet was to build two identical stereo amps (better, more preferred for resale prospects) than odd-ball mono Franken-amps... The initial idea was to use a stereo amp, simply pull the fuses from one channel and devote the entire supply to running only one channel... x2.
[long term] Ideally I would like to build separate pi filtered power supplies, rather than cramming what I really wanted into one (or 2) already compact chassis's. This build would (does) ultimately support proof of concept... whether, such madness was warranted... 4 chassis for stereo amps... those amazing vintage lateral Hitachi MOSFETS were driving me (mad) to the extremes and filling up my floor and listening rooms...
The second challenge was what 2 chassis's to cannibalize for such a project... I never really liked the asymmetrical layout of the P230 (or the XL-280, only had one of them) Positively ~ hated ~ the stock P230, it was a rats nest, which I bought to gut, needing to be cleaned out... So the (2) P230s became the sacrificial candidates. I went through many ideas and layouts, even drilling and mounting parts only to change my mind, so as not to duplicate other builds... I really wanted to try something different, wanted to experiment. I re-positioned the second pair of 5 way binding posts, while drilling and mounting toroid and P/S caps, with the chassis pan empty, in the event I will ever complete these as stereo versions. The 'OCD' perfectionist in me was satisfied. It took me a solid month to make up my mind...
Most of my listening and comparisons were the with Atma-Sphere OTL amp(s) and DH500 (based amps) with an honorable mention to the XL600, ...with that noisy fan... Very stiff competition for said concept amplifiers, in the idea, design and build phase... At a point, I had chassis's and parts laid out in a checkerboard (literally) on the floor to try and reason, the great many options. My biggest single obstacle (not joking) was cutting / shortening the power transformer wires... it was a commitment to this chassis and layout, with no going back. One other *key objective* was to position all AC on the opposite side of the chassis to the amplifier circuitry... I really like this layout and the way it turned.
Twin mono P230 amps are now gracing my sound system... I always start with the amplifier core (image 2) get that set, as it really [is the amp] and work my way outward to driver and output stage. It was not a matter of lower cost, or a build budget, it was about how close I could get to the dual mono, Jensen capped MC500 and the venerable Atma-Sphere MA1 amps...
Honestly, I have about 1,700-1,800.00 into these mono amps, they sound fantastic and are not even broken in yet! A 30+ year 'dream' manifests... and I will be selling some 'other' gear... cannot imagine selling these mono Franken-amps. The only thing, that I want to change or add, is Cardas Rhodium RCA and 5 way copper binding post (add another ~ 200.00)
A long post [sorry] It was a lot of work, long journey and story, the past 3-4 months, much of it 'in lock down' with the current global madness...
I bought and 'updated' my first XL600 with Musical Concepts new PA7 boards, also built it *true* dual mono. It sounds so fabulous, unparalleled driving my Maggies, which started an amplifier building and rebuilding frenzy... I started swapping boards and parts around, updated my "once DH" MC500 with a 2nd set of PA7 driver boards, making appreciable sonic gains at every turn. I cannibalized the Jensen 4-pole capped P230, in the front (image 1) it 'no longer exists' as shown is now one of the dual mono amps. It turned out that the 6 output versions greatly overshadowed any of the 200 / 220 versions I had built prior... with the speaker assortment that I have on hand... will admit to getting a little carried away... those here may truly understand this...
A virtue in owning a dozen assorted "Hafler amps", I can model so many concepts... compare them directly to one another. I have had ideas to build mono versions for some time (over 30 years) first had to pick a power supply, driver circuit and chassis which warranted such a build. The safest bet was to build two identical stereo amps (better, more preferred for resale prospects) than odd-ball mono Franken-amps... The initial idea was to use a stereo amp, simply pull the fuses from one channel and devote the entire supply to running only one channel... x2.
[long term] Ideally I would like to build separate pi filtered power supplies, rather than cramming what I really wanted into one (or 2) already compact chassis's. This build would (does) ultimately support proof of concept... whether, such madness was warranted... 4 chassis for stereo amps... those amazing vintage lateral Hitachi MOSFETS were driving me (mad) to the extremes and filling up my floor and listening rooms...
The second challenge was what 2 chassis's to cannibalize for such a project... I never really liked the asymmetrical layout of the P230 (or the XL-280, only had one of them) Positively ~ hated ~ the stock P230, it was a rats nest, which I bought to gut, needing to be cleaned out... So the (2) P230s became the sacrificial candidates. I went through many ideas and layouts, even drilling and mounting parts only to change my mind, so as not to duplicate other builds... I really wanted to try something different, wanted to experiment. I re-positioned the second pair of 5 way binding posts, while drilling and mounting toroid and P/S caps, with the chassis pan empty, in the event I will ever complete these as stereo versions. The 'OCD' perfectionist in me was satisfied. It took me a solid month to make up my mind...
Most of my listening and comparisons were the with Atma-Sphere OTL amp(s) and DH500 (based amps) with an honorable mention to the XL600, ...with that noisy fan... Very stiff competition for said concept amplifiers, in the idea, design and build phase... At a point, I had chassis's and parts laid out in a checkerboard (literally) on the floor to try and reason, the great many options. My biggest single obstacle (not joking) was cutting / shortening the power transformer wires... it was a commitment to this chassis and layout, with no going back. One other *key objective* was to position all AC on the opposite side of the chassis to the amplifier circuitry... I really like this layout and the way it turned.
Twin mono P230 amps are now gracing my sound system... I always start with the amplifier core (image 2) get that set, as it really [is the amp] and work my way outward to driver and output stage. It was not a matter of lower cost, or a build budget, it was about how close I could get to the dual mono, Jensen capped MC500 and the venerable Atma-Sphere MA1 amps...
Honestly, I have about 1,700-1,800.00 into these mono amps, they sound fantastic and are not even broken in yet! A 30+ year 'dream' manifests... and I will be selling some 'other' gear... cannot imagine selling these mono Franken-amps. The only thing, that I want to change or add, is Cardas Rhodium RCA and 5 way copper binding post (add another ~ 200.00)
A long post [sorry] It was a lot of work, long journey and story, the past 3-4 months, much of it 'in lock down' with the current global madness...
Attachments
Is that $200 for both channels or $100* to complete one* channel*? This* will make sense when you read the last paragraph.
Where in the frequency spectrum will they make that $200 difference or how does it affect the soundscape? I’m a staunch advocate for minimum connection resistance through most any means possible. (Looong story)
The various channels in my HT system are either bi-amped or tri-amped. Down the road* I’m not opposed to selective upgrades to some of the amps and some speaker BPs.
* have bigger fish to fry over the next ~12 months
Thanks in advance for your help and advice. Tony
Random pictures, as a build up to amps...
I really struggled to make up my mind. I did layout several ideas "in a checkerboard", on the floor, not all parts and amps are shown, I could not fit them into the frame. (Image 2) I was kind of modeling, external Pi filter notions, with the staggered caps. Kitty Roe Roe really likes the toroids, being the lady of the house; she has a say in things...
I have so many parts, stock pulls old and new, I will admit to supply chain concerns and that I have stock piled / hoarded many parts. I feel a confidence in having (on hand) some things which are hard to get... I think the cat at a point was even perplexed by the amassing of parts and clutter, as I was thinking near term and long term. I did not want to duplicate past efforts and honestly, I am building several amps for a few friends... swapping things around, while turning over a few of my PA4 boards and a few other parts. My head hurt on some night during this process...
At a point I considered, using 2 of the 3 stock power transformers with dual (higher voltage) secondaries, pulled from both the P230 and XL280, and building *separate front end supplies, but ruled that out... I wanted a clean chassis and aesthetic. More likely in 2 chassis model...
I ended up building with the 'new' Musical Concepts TP-202 that has the outer shield band and a static ground band, which conceptually fascinated me... I am glad I did, in spite of having already having bolted 2 stock power transformers in place. The TP-202s are that ~ amazing ~ I think a great portion the fundamental refinement in the amps I built and am enjoying so much, right out of the chute. The next month (break in) will be amazing... with all the new parts breaking in.
The last image (staged) not actually planned concept of an unrealistically stuffed chassis with 2 stock transformers and 4 caps (in a 69 position) was an homage to the mighty Mark Levinson ML3 that torqued my imagination so many years ago... it actually singularly started a lifetime of amplifier study and my building obsession... leading to this intense hobby and ways of spending time [and money] in retirement.
I really struggled to make up my mind. I did layout several ideas "in a checkerboard", on the floor, not all parts and amps are shown, I could not fit them into the frame. (Image 2) I was kind of modeling, external Pi filter notions, with the staggered caps. Kitty Roe Roe really likes the toroids, being the lady of the house; she has a say in things...
I have so many parts, stock pulls old and new, I will admit to supply chain concerns and that I have stock piled / hoarded many parts. I feel a confidence in having (on hand) some things which are hard to get... I think the cat at a point was even perplexed by the amassing of parts and clutter, as I was thinking near term and long term. I did not want to duplicate past efforts and honestly, I am building several amps for a few friends... swapping things around, while turning over a few of my PA4 boards and a few other parts. My head hurt on some night during this process...
At a point I considered, using 2 of the 3 stock power transformers with dual (higher voltage) secondaries, pulled from both the P230 and XL280, and building *separate front end supplies, but ruled that out... I wanted a clean chassis and aesthetic. More likely in 2 chassis model...
I ended up building with the 'new' Musical Concepts TP-202 that has the outer shield band and a static ground band, which conceptually fascinated me... I am glad I did, in spite of having already having bolted 2 stock power transformers in place. The TP-202s are that ~ amazing ~ I think a great portion the fundamental refinement in the amps I built and am enjoying so much, right out of the chute. The next month (break in) will be amazing... with all the new parts breaking in.
The last image (staged) not actually planned concept of an unrealistically stuffed chassis with 2 stock transformers and 4 caps (in a 69 position) was an homage to the mighty Mark Levinson ML3 that torqued my imagination so many years ago... it actually singularly started a lifetime of amplifier study and my building obsession... leading to this intense hobby and ways of spending time [and money] in retirement.
Attachments
~ for me ~ [of course, we each have different need and goals]
the Cardas are hard to beat, and most transparent...
Over long term (+20 years of) use. The Cardas, look [exactly] like the day I bought them. Are very much within (my) budget and means... inexpensive for the whole of my build... They are most transparent too... they come standard on my Atma-Sphere and Rowland gear...
(4) RCAs ~ 50.00-60.00
(4) 5-way binding posts ~140-150.00
(to complete, 2 stereo amps) or as shown.
from Parts Connextion (sp?)
I like the stock (15.00 each, at Mouser) Pomona 5WBP's, but have had the vinyl strip... in heavy use, in evaluation modes and with the beefy spades on the Kimber and Cardas cables I use...
My idea is 'to complete these amps' but not necessarily wire the unused channel, it is easier (for me) to do all of the work at once.
And / or, I can wire up two completely different driver circuit boards (as example, a set of Bobs boards) and only run one set, but have the abilities to 'quickly' switch, by simply popping out the fuses. For modeling evaluation purposes...
Hard to explain, I am tired...
**What do you (prefer) like and use Tony?
Last edited:
Hi Ozark,
I can see why you are exhausted, one heck of a lot of mod work, wonderful contribution to this thread. The king of Hafler mods.
Definitely would like to hear your impressions, on Bob’s DH-220C design. Send me a message, if you want to try it out.
I was thinking of designing a rectifier filter board, would appreciate your input. I have a few ideas, like using some newer ST FERDiodes. 35mm snap in ecaps. Some other possibilities, incorporate the supply fuses, so that I could make a “U” shaped pcb, to wrap around the transformer, add a soft-start relay, maybe even a protection ckt, could use the one from the DH-500 design, or the UPC1237 chip, have to evaluate how much pcb area is needed and is available.
Cheers
Rick
I can see why you are exhausted, one heck of a lot of mod work, wonderful contribution to this thread. The king of Hafler mods.
Definitely would like to hear your impressions, on Bob’s DH-220C design. Send me a message, if you want to try it out.
I was thinking of designing a rectifier filter board, would appreciate your input. I have a few ideas, like using some newer ST FERDiodes. 35mm snap in ecaps. Some other possibilities, incorporate the supply fuses, so that I could make a “U” shaped pcb, to wrap around the transformer, add a soft-start relay, maybe even a protection ckt, could use the one from the DH-500 design, or the UPC1237 chip, have to evaluate how much pcb area is needed and is available.
Cheers
Rick
Last edited:
I've been considering doing this cascoding to my 40 year old DH-200 which I just cracked open to evaluate for cap replacement etc. It was advertised as an easy upgrade that made a big difference for little relative effort. Do you have a photo of how it looked afterwards? Any advice would be helpful too.
Also, I noticed that one of the heatsink-mounted thermal breakers is looking a bit crispy. Does anyone know what the specs are of this device? The model seems to be discontinued and I cannot find out anything about it. It is identified as an Elmwood Senors 87-232 L167 80/J.
Thanks.
Last edited:
That is awesome!!!
I do like… That image gives me a brain tickle. Don't get me started, I am highly susceptible to influence… LOLS. I have long wanted to try some Exicons… but would 'have to kill another amp;’ toss MOSFETS to the side, so to say...
I would have thought, after buying and owning so many Hafler amps over the years, I would have encountered some dead MOSFETS (not a desire) simply something you are bound to see, buying 2nd hand gear off of eBay and CL…
These vintage MOSFETS are so remarkably robust, it is portion to why I have not used speaker protection fuses on the outputs, I have not seen failures. Not in my work, or direct experience.
Exicons are in my future, these lateral MOSFETS are going head to head with my OLT vaccum tube gear, at fractions of the cost...
I do like… That image gives me a brain tickle. Don't get me started, I am highly susceptible to influence… LOLS. I have long wanted to try some Exicons… but would 'have to kill another amp;’ toss MOSFETS to the side, so to say...
I would have thought, after buying and owning so many Hafler amps over the years, I would have encountered some dead MOSFETS (not a desire) simply something you are bound to see, buying 2nd hand gear off of eBay and CL…
These vintage MOSFETS are so remarkably robust, it is portion to why I have not used speaker protection fuses on the outputs, I have not seen failures. Not in my work, or direct experience.
Exicons are in my future, these lateral MOSFETS are going head to head with my OLT vaccum tube gear, at fractions of the cost...
Last edited:
Mutual interests...
Thanks Rick, I appreciate your grounded experience, understanding and comments. I have seriously thought of contributing some parts or possibly even an amplifier core to support your remarkable efforts, as shown. I appreciate your dedication and work, modeling these driver boards. Experience has proven the stock boards are simply too limited to rebuild and fuss with...
I have long wanted to work with and build discrete rectifiers, but will likely approach this in an external chassis model, as I reference earlier. I really want to get the (magnetics and noise) AC, rectification, etc. away and isolated from the audio circuitry.
I will message you o/l, to share some information and contact details, to see how we may possibly help each other. You touch on some key points and interests, I have also considered… KUDOS!
- - - -
I have pretty much kept to myself, after some others heavy handed posts. That is not why I am here… It is about sharing and building in the collective of the mind share about this passion and pursuit.
Thanks Rick, I appreciate your grounded experience, understanding and comments. I have seriously thought of contributing some parts or possibly even an amplifier core to support your remarkable efforts, as shown. I appreciate your dedication and work, modeling these driver boards. Experience has proven the stock boards are simply too limited to rebuild and fuss with...
I have long wanted to work with and build discrete rectifiers, but will likely approach this in an external chassis model, as I reference earlier. I really want to get the (magnetics and noise) AC, rectification, etc. away and isolated from the audio circuitry.
I will message you o/l, to share some information and contact details, to see how we may possibly help each other. You touch on some key points and interests, I have also considered… KUDOS!
- - - -
I have pretty much kept to myself, after some others heavy handed posts. That is not why I am here… It is about sharing and building in the collective of the mind share about this passion and pursuit.