That's the one I have too, downloaded from FW site. Tnx.
And I also have the "dyaudio" version with bigger caps and single jfets, which simulates very well in ltspice.
200 is the theoretical limit where diminishing returns end.
But we dont need that much actually, and current delivery is as much important as DF.
I had time to experiment recently with various amp from very low to very high DF, and... it depends on the speakers. The way the XO is made has an influence on both DF and current demands.
F4 has 40 DF into 8 ohms (it halves on 4 Ohm). It is not much but it should be OK for many commercial speakers and even more DIY, especially if active driven directly as shown in the F4 manual.
Excessive DF will not sound right either, it tends to dry the sound excessively and overdampen a pair of speakers with already tight bass (such as TL like mines, closed boxes or OB for instance).
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LightDims Original Strength - Light Dimming LED covers and Light Dimming Sheets for Routers, Electronics and Appliances and more. Dims 50-80% of Light, in Minimal Packaging. - Ceiling Pendant Fixtures - Amazon.com
This works perfectly to dim blue leds and stick well to aluminum frontplates.
I have used it for those damn blue leds on other devices
For total cover, there is another version, which would look much better than electrical tape:
LightDims Black Out Edition - Light Blocking LED covers / Light Dimming Sheets for Routers, Electronics and Appliances and more. Blocks 100% of Light, in Retail Packaging. - Light Dims Led Light Blocker - Amazon.com
In the deep past I used result of punching: small black circles/pucks taken from typical puncher - instead of paper I used special stiff plastic tape with a glue layer. Such tapes ware used for embosing white text on tape. It was DYMO hand printing/embossing tool and tapes, variety of colours. The only problem was that the puncher sometimes makes a white border around the puck.
Black tape to completely suppress the light, red tape to slightly suppress too bright red LED.
Andrzej
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I am liking the concept of these "hot followers". Not sure why I didn't build one sooner. Well, actually I did with the BA-1 but I didn't fully flesh out the idea. It opens up a whole world of high gain SS and tube circuits that were a poor match with my previous medium and high gain amplifiers. I cleaned the dust off of my old Bottlehead Foreplay 2 and have that in front of my new F4's right now, really the first time I have been able to get a feel for what it sounds like. No mods on that really, just better output caps and DC filaments. Before it simply had "hair trigger" volume pots and throwing away most of the signal to ground. I added resistors to pad the input to make the volume pots use-able, but if I remember correctly it really affected the sound quality in a negative way. Obviously some poor system gain structure right there, so the thing just never got used.
This is one person's thoughts on the AKSA-Lender, the Nelson BA-3 and the Yaniger ImPasse preamps. The amps being used are a pair of bridged Pass designed F4. The F4 amps need a preamp with a larger output voltage than most preamps can deliver. The three listed above are capable of the necessary output.
My first DIY build began in 2014 was the BA-3 followed by one F4. I liked that combination so well I build another F4. The ImPasse was something I wanted to try and finally late last year purchased the boards and input transformers from Jack. Then Hugh delivers his AKSA-Lender preamp to the community and I wanted to try it also with the F4 amps.
Please keep in mind these are my thoughts using this three preamps and your listening experiences will vary, due to variances in the builds, your listening space and choice of speakers.
My BA-3 build uses a single toroidal transformer into a Salas shunt regulator. The BA-3 has genuine Toshiba transistors and I am using 10uf Mundorf SIO caps on the outputs with Goldpoint pot and selector. Using the P3 adjustment, the second harmonic has a negative phase. The AKSA-Lender was built from the BOM listing from that thread. I chose R9 for a more dominate second harmonic. Finally the ImPasse was also built using the BOM from that thread. I did do some tube rolling, started with Electro Harmonix and really didn't like the sound. Finally ended with some NOS RCA and Amperex tubes.
I am using a Pink Floyd song from their 1973 album "Dark Side of the Moon". That song is " The Great Gig in the Sky". The instruments are a piano, Hammond organ, pedal steel guitar, bass, and drums. The main vocals are supplied in an almost orgasmic way by Clare Torry. Her wailing reveals much about the preamps. Also I listened to the live version of Dave Brubeck's "Take Five" from the album "Concord on a Summer Night".
BA-3 preamp
A nice wide sound stage, with the pedal steel guitar coming more from the right side. Good depth with the vocal and drums coming from the rear. Cymbals are crisp. In the second set of vocals distinct sounding. The piano sounds very smooth and rounded. There is a nice sonic balance with the bass.
AKSA-Lender preamp
Also a wide sound stage. The pedal steel is not as defined as the BA-3. Cymbals have a nice sizzle. The Hammond organ is distinct and the vocals are more forward sounding. Drums are also very defined.
ImPasse preamp
Another wide sound stage. The piano and pedal steel are well defined. Vocal appears from upper left with the bass more defined. Cymbal also with nice sizzle sound. In the second set of vocals there is a nice balance with the piano. For me the vocals were not as clearly defined as the two solid stage preamps.
Finally the question would be which is best/sounds better, etc. For me there is a personal enjoyment when listening with each preamp at different times with different music. Ok, my order of preference would be the BA-3, AKSA-Lender, and ImPasse. I believe both solid state preamps have a slight edge over the tube preamp. Finally if you want to look at cost and versatility then the AKSA-Lender has both of the others beat for price and convenience. In my opinion it offers the most bang for the money.
So final thoughts, any of these preamps would be great with the Pass F4 amps. My wife and I for the past twenty years have been involved with retired racing greyhound adoption. In that adoption world, there is a catch phrase that is applicable to the DIY audio world. It is "they are like potato chips, it's hard to stop with only one". True for the greyhounds and so true for the DIY audio world. All I can say is build and enjoy.
Thanks
David
My first DIY build began in 2014 was the BA-3 followed by one F4. I liked that combination so well I build another F4. The ImPasse was something I wanted to try and finally late last year purchased the boards and input transformers from Jack. Then Hugh delivers his AKSA-Lender preamp to the community and I wanted to try it also with the F4 amps.
Please keep in mind these are my thoughts using this three preamps and your listening experiences will vary, due to variances in the builds, your listening space and choice of speakers.
My BA-3 build uses a single toroidal transformer into a Salas shunt regulator. The BA-3 has genuine Toshiba transistors and I am using 10uf Mundorf SIO caps on the outputs with Goldpoint pot and selector. Using the P3 adjustment, the second harmonic has a negative phase. The AKSA-Lender was built from the BOM listing from that thread. I chose R9 for a more dominate second harmonic. Finally the ImPasse was also built using the BOM from that thread. I did do some tube rolling, started with Electro Harmonix and really didn't like the sound. Finally ended with some NOS RCA and Amperex tubes.
I am using a Pink Floyd song from their 1973 album "Dark Side of the Moon". That song is " The Great Gig in the Sky". The instruments are a piano, Hammond organ, pedal steel guitar, bass, and drums. The main vocals are supplied in an almost orgasmic way by Clare Torry. Her wailing reveals much about the preamps. Also I listened to the live version of Dave Brubeck's "Take Five" from the album "Concord on a Summer Night".
BA-3 preamp
A nice wide sound stage, with the pedal steel guitar coming more from the right side. Good depth with the vocal and drums coming from the rear. Cymbals are crisp. In the second set of vocals distinct sounding. The piano sounds very smooth and rounded. There is a nice sonic balance with the bass.
AKSA-Lender preamp
Also a wide sound stage. The pedal steel is not as defined as the BA-3. Cymbals have a nice sizzle. The Hammond organ is distinct and the vocals are more forward sounding. Drums are also very defined.
ImPasse preamp
Another wide sound stage. The piano and pedal steel are well defined. Vocal appears from upper left with the bass more defined. Cymbal also with nice sizzle sound. In the second set of vocals there is a nice balance with the piano. For me the vocals were not as clearly defined as the two solid stage preamps.
Finally the question would be which is best/sounds better, etc. For me there is a personal enjoyment when listening with each preamp at different times with different music. Ok, my order of preference would be the BA-3, AKSA-Lender, and ImPasse. I believe both solid state preamps have a slight edge over the tube preamp. Finally if you want to look at cost and versatility then the AKSA-Lender has both of the others beat for price and convenience. In my opinion it offers the most bang for the money.
So final thoughts, any of these preamps would be great with the Pass F4 amps. My wife and I for the past twenty years have been involved with retired racing greyhound adoption. In that adoption world, there is a catch phrase that is applicable to the DIY audio world. It is "they are like potato chips, it's hard to stop with only one". True for the greyhounds and so true for the DIY audio world. All I can say is build and enjoy.
Thanks
David
How about front pair of matched jfets? Any plans of having those in the store again? Thanks...
If Linear is ever to produce enough to sell, yes, they will be back in the store. They would never be out of stock if it were up to us...
In the time being, this seller is selling genuine fets, he's an acquaintance of Nelson's, and a good source for genuine Toshiba Jfets.
Toshiba 2SJ74 + 2SK170 LAB MATCHED QUAD to 0.03mA AND 4mV (7ma range) | eBay
In the time being, this seller is selling genuine fets, he's an acquaintance of Nelson's, and a good source for genuine Toshiba Jfets.
Toshiba 2SJ74 + 2SK170 LAB MATCHED QUAD to 0.03mA AND 4mV (7ma range) | eBay
Hi David,
Thanks for this. Most of the time, we don't get real comparisons of real, high quality, DIY designs. I am aware of the effort it must have taken to build all three. Congratulations! You have three good pre's and the confidence to know what your choices mean. That is very cool.
Jac
Silly question, but from the thread i started-
I was hoping someone could advise, as I'm not super familiar with the scheme used to bias the F4.
I was hoping someone could advise, as I'm not super familiar with the scheme used to bias the F4.