PrestonTom Posted April 2, 2014 Share Posted April 2, 2014 ...... Yes, currently I cant move my right hand. I had carpal tunnel surgery at 7 am. Dave Best wishes for a speedy recovery! Quote Link to comment Share on other sites More sharing options...
jason str Posted April 2, 2014 Share Posted April 2, 2014 Hope you have a speedy recovery. Nice looking project you have going there. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 3, 2014 Share Posted April 3, 2014 Thanks guys, I am working on it. Quote Link to comment Share on other sites More sharing options...
beeker Posted April 3, 2014 Share Posted April 3, 2014 Thank you for giving an understanding to this amp. I had read up on it for the 1st time when i seen your pics. Missed your doggy though. Really nice thread, again. Never heard of this amplifier configuration/brand-makeup until your pics. Your pretty great with your projects Dave i really admire your work and enjoy your pics even though i dont understand some graphs completely. Thats what guys like you do. Very interesting. Cheers! Quote Link to comment Share on other sites More sharing options...
Fjd Posted April 3, 2014 Share Posted April 3, 2014 (edited) I received a PM from duder1982 that said "I have a set of the Pass F5 boards I am not going to use. I will give them to you if you start a thread about your build." I replied "yeah, sure, cool, awesome...." Nice build! Since you seem open-minded about understanding the strenghs & weaknesses of both tubes and SS designs, now that duder1982 started you down the path, either you owe it to yourself (or maybe duder owes it to you since he 'started it'?) to build another First Watt design to take advantage of either your DHT 300b SET or the other SEP (I think it is SEP or is it a PP?) amp that you have. For the power supply in your amplifier, did you follow the basic "First Watt" topology of 18+18V transformer, of at least 300VA, CRC filter with 8 15,000uF minimum of 25V capacitors and 8 (4 per rail) 0.47ohm 3W resistors? If so, since you used the DIY store PCBs for the F5 and the DIY store 4U deluxe case (I believe with the heat sinks that are pre-drilled) for most of the various First Watt iterations (i.e. Aleph J, F4, F5 and I believe a couple of the other PCBs sold through the store), you could even try a few other First Watt versions with minimal additional investment. I saw one recently that had very nice connectors to unplug the PCBs that contain the JFets and Mosfets that looks like it would save a lot of time re-wiring. Most seem to be using the Keratherm insulators too, while there is added cost each time you replace, I find them easy to work with. Note that duder's esoteric F5 turbos use different power supply specifications, but the basic First Watt designs I've referenced above are more interchangeable with the same power supply (but should check as there may be a couple of minor changes to look up) as they all typically use what I've detailed above. Therefore, you should not have to buy all new PS caps, a new transformer or the core resistors on the rails. I'm sure you are aware, but for those that may be interested, I've provided a few general descriptions of a few of the FW amplifiers below, along with a few of my impressions when used in my various systems; however, the amp that I personally find the most interesting is the F4 amplifier as it is very flexible in various implementations. I essentially use my DHT SET amplifiers as the "voltage gain stage" directly into the F4 and because the F4 is such a simple Push-Pull circuit with no feedback, a lot of the characteristics of the DHT SET amp that I find very favorable will come through. I think of it kind of like a "SET on steroids" in some ways, but also noting that it looses some of what DHT SET provides in those near-field lower-level listening sessions. Since the F4 is basically a refined power follower, it will essentially push the same voltage out that you send into it, but it will feed much more current through the load than the SET amp, if needed. There are various implementations of "adaptors" out there as the DHT SET output will need to be adapted to the RCA input of the F4. Also, due to the F4's high input impedance (47,000 ohms), a resistor (~ 20 ohm, 5 watt resistor, but some have used anywhere from about 15 ohm - 22 ohm depending on how they like the sound) is needed across the SET outputs since the SET only "sees" the F4 and not the speakers. On DHT SET amps with multiple taps (i.e. 4, 8 or 16 ohm) there seems to be some diversity on which tap sounds best; however, I suspect that is more related to system synergies. Essentially, you have a "component" approach to a quality tube gain-stage followed by a high-end design solid state buffer. I think you see scaled versions of this tube gain stage / solid state buffer concept in headphone amps for which the quality implementations seem to be very well-received; therefore, it seems to be a valid higher-end approach to try for speakers. If you get a chance, read the F4 manual, and with the various speaker implementations you have been involved with, the wheels in your imagination may just start to turn in differet ways than before regarding the flexibility of a SET and F4 in conjunction with your various speaker designs. For example, since the F4 is close to unity gain that should provide close level matching between top and bottom, there should be some opportunity to 'bi-amp' certain speakers using a quality DHT SET amp with the F4 amp. Note that in the diagram below, it is assumed that the crossover networks are incorporated into the woofer and mid/high end speakers. Link to the F4 manual. http://www.firstwatt.com/pdf/prod_f4_man.pdf After the amp was assembled, and initial biasing was done, I allowed it to warm up the recommended 2 hours before re-biasing. In the mean time I had plenty of time to audition the amp. Really a great sounding unit. The only down side of this amp I can find is that it requires a lot of drive to achieve full output power. Fortunately I had and Amps and Sound SSP - battery operated preamp on hand that will drive damn near anything. I listened to all of the favorites, and I have to give Mr Pass credit, this is a fine piece of gear. Watt is Nelsons motto? What does it matter how much power you have If the first watt sounds like ****. Just like having children, I've listened fairly extensively to the F3, F4, F5 & Aleph J and I think the First Watt amplifiers are all exellent when used within the intended design parameters within a system, but it is hard to pick a clear favorite. The Aleph J uses JFET devices for the front end of a two stage single-ended Class A amplifer with Mosfets for the output devices. To me, it has a nice relaxed, musical and warm presentation with a very nice amount of detail and can be used in a somewhat broad range of speakers on the higher efficiency side. The F3 (not currently supported in the DIY store) has very low distortion measures and an extememly low noise floor using the power JFETs in a single-stage, single-ended Class A circuit. To me this amp has a touch of the warmth with a very nice amount of detail, but will be limited in how it is used. I use mine for closer near-field, low-level listening on high efficient speakers. Several on the forum seem to have very successful implementations for the high frequency side of bi-amp implementations. The F5 is a push-pull Class A amplifier that uses JFETs on the front end and Mosfet outputs in a simple two-stage complementary circuit with a touch of feedback. I believe that the amplifer was meant to appeal to a broad range of people with more diverse systems that needed a more main stream amplifier that would fit in a large number of potential implementations, was simple in design, but quality in design, and provides exellent insight into just how capable a solid Class A design can perform. Also very low distortion measures and while the noise floor is extremely low, it is not quite as low as the F3 or F4. To me this amplifier is very fast and resolves a lot of detail; however, in my systems it doesn't have the 'warmth' that I'm looking for in a similar manner to the Aleph J. The F4 is a Class A "impedance converting" push-pull amplifier that has "current gain" but does not have any voltage gain and does not have any feedback. It 'mates' well with most components that can deliver the voltage gain needed to drive your speakers as it is essentially a very large high-quality buffer. Distortion is a little higher than the F5, but still very respectable and much lower than my DHT SET amps, but the noise floor is one of the lower that I've seen available. A very quiet amp and only the very narrow-focused F1J & F2J have lower measured specifications. To me, the F4 amp is the amp that I find most interesting given how it seems to pass through a significant portion of the characteristics that I find attractive in my DHT SET amp that is paired with it. I find the combination very musical and very resolving in details. To describe it another way, much like a much more-musical F5, but I believe this experience will be very "system dependent" and depends very much on synergies with your overall system and having a high-quality DHT SET (or whatever voltage gain device you find really compelling) driving the F4. Yes, currently I cant move my right hand. I had carpal tunnel surgery at 7 am. Dave Wishing you a speedy and complication-free recovery. Edited April 11, 2014 by Fjd Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 4, 2014 Share Posted April 4, 2014 Quite the post FJD, I will certainly consider that. Wishing you a speedy and complication-free recovery.Thanks, Dave Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 11, 2014 Share Posted April 11, 2014 I'm back at it. I Removed and tested the 2sk170 and 2sj74, both good. Started checking resistor values, none are burnt, but R11 measures 1.3M ohms, That might be an issue for a .47R. Replaced the resistor and re-biased the amp. All is working properly, sounds great except for a low level hum that only occurs with my preamps connected - some sort of ground loop I suspect. During biasing, I had an oscilloscope on the output, and was clear the trace was cleaner biased at 1.2mv. however my instructions mention biasing close to 0mv. In the end, I stopped tweaking at 0.4mv. Checked temp at both heat sinks, approximately 125 deg F. Listening test, this amp has only been running 8 hours and sounds great. I have been running this amp on my personal speaker design ( The Yields). These speakers utilize an Audio Nirvana Super 10 full range driver from 200+. Immediately I verified Mr. Pass's depiction of this amps characteristics, Bass is spot on, detail is amazing, and this amp is unforgiving of response spikes typically found in full range drivers. Nelson Pass quote. "F5: Dynamic, accurate, a little unforgiving. On speakers with peaks in the top end, it will reveal as too bright and annoying. On speakers with a slightly diminished top end, it adds a little sparkle, this in spite of being flat out at high as 500 KHz. Good control - if your speaker is a little boomy, it will tend to tighten it up. Overall, probably the most neutral of the FW amps. It will drive 4 ohm loads without particular issues. Oh, and it does sound very good." I could not agree more. Dave 1 Quote Link to comment Share on other sites More sharing options...
Lemon string Posted April 11, 2014 Share Posted April 11, 2014 Great Thread! Ive always wanted a first watt amp or to attempt a build myself. Who knows maybe someday? Looks great thanks for sharing. Quote Link to comment Share on other sites More sharing options...
eth2 Posted April 11, 2014 Share Posted April 11, 2014 (edited) Immediately I verified Mr. Pass's depiction of this amps characteristics, Bass is spot on, detail is amazing, and this amp is unforgiving of response spikes typically found in full range drivers. So when will you be selling it? Have I mentioned that I have a VAC PA90 for sale? It is "almost" silent (compared to a 747). Edited April 11, 2014 by eth2 Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 11, 2014 Share Posted April 11, 2014 It is "almost" silent (compared to a 747). Quite the comparison. Dave Quote Link to comment Share on other sites More sharing options...
eth2 Posted April 11, 2014 Share Posted April 11, 2014 Always look for the silver lining. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 11, 2014 Share Posted April 11, 2014 Now that amp has 15+ hours. Listening comparisons between my MC-2100 and this Pass F5. The F5 digs out every bit of detail from every track, and its imaging is glorious. The bass as I stated earlier is spot on, and the midrange is full and smooth. The major differences between the F5 and the MC-2100 is the F5 is more detailed, less forgiving of poor recordings, and the bass a bit tighter. The MC-2100 has a smoother rolled top end, much like a tube-amp. To sum it up: Both are great amps, and like everything else, they are speaker, environment, and user dependent. Dave Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 11, 2014 Share Posted April 11, 2014 (edited) Here is a shot of the F5 cleaned up the wiring , and got it up off the chassis. Edited April 11, 2014 by GotHover Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 11, 2014 Share Posted April 11, 2014 (edited) I wish you would sell this to ETH2 so he can put the ear muffs away. Edited April 11, 2014 by JL Sargent 2 Quote Link to comment Share on other sites More sharing options...
The Dude Posted April 11, 2014 Share Posted April 11, 2014 What is with the added board for the output wires, all so what kind of sheathing is that over power wires from the power supply to the output boards. Looks nice and clean. When you say less forgiving you mean more accurate. Thanks for the right up, sounds like a really nice amp. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 12, 2014 Share Posted April 12, 2014 What is with the added board for the output wires, all so what kind of sheathing is that over power wires from the power supply to the output boards. Looks nice and clean. The boards are just small pieces of Teflon to keep the wires from dragging on the chassis. The wires and insulators are from automotive oxygen sensors, the wire is PTFE insulated, silver plated stranded copper wire. The insulator is a high temp insulating tube. - My contribution to recycling. Dave 1 Quote Link to comment Share on other sites More sharing options...
eth2 Posted April 12, 2014 Share Posted April 12, 2014 I wish you would sell this to ETH2 so he can put the ear muffs away. I was think more of a trade for a "pristine" VAC amp. Hell, with all the work that has gone into the VAC by the Forum, I will take it to the grave with me. Just hope my trip to the grave is not hastened by the continuing ssstttrrreeess. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 13, 2014 Share Posted April 13, 2014 (edited) . Edited April 14, 2014 by GotHover Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 13, 2014 Share Posted April 13, 2014 (edited) All is working properly, sounds great except for a low level hum that only occurs with my preamps connected - some sort of ground loop I suspect. Alright, this hum has been bothering me, so I decided to tackle it today. The power supply board was the culprit. It was fairly simple, I just had to re-locate the grounds in a Star grounding configuration, no more noise. Edited April 13, 2014 by GotHover Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 14, 2014 Share Posted April 14, 2014 (edited) . Edited April 14, 2014 by GotHover Quote Link to comment Share on other sites More sharing options...
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