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Old 16th April 2018, 05:46 PM   #4391
drpro is offline drpro  United States
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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
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Old 16th April 2018, 08:36 PM   #4392
adason is offline adason  United States
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Quote:
Originally Posted by Variac View Post
just an FYI:
we still sell the boards for the F-4 at the diyAudio Store

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How about front pair of matched jfets? Any plans of having those in the store again? Thanks...
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Old 16th April 2018, 09:33 PM   #4393
6L6 is offline 6L6  United States
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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
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Old 16th April 2018, 10:46 PM   #4394
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by 6L6 View Post
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
Of course, Nelson's credibility is much higher than mine, but I can confirm that I have purchased the same from this seller, measured them, and can confirm that they are both genuine and well matched.
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Old 17th April 2018, 02:54 PM   #4395
adason is offline adason  United States
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Thanks, good to know that.
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Old 17th April 2018, 04:21 PM   #4396
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by drpro View Post
This is one person's thoughts on the AKSA-Lender, the Nelson BA-3 and the Yaniger ImPasse 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.
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
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Old 17th April 2018, 05:30 PM   #4397
drpro is offline drpro  United States
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Thanks Jac l can not design them but can build them. Old Heathkit guy here!!

I am working on my thoughts for Michael’s Mofo. Stay tuned

David
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Old 19th April 2018, 06:35 PM   #4398
Lingwendil is online now Lingwendil  United States
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Silly question, but from the thread i started-

Quote:
Originally Posted by Lingwendil View Post
Just found that I have the lower reference voltage version of the TL431 on hand, the TLV431... Will it work in the F4? I'm assuming that it would need some parts value changes...
I was hoping someone could advise, as I'm not super familiar with the scheme used to bias the F4.
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Old 19th April 2018, 08:35 PM   #4399
Zen Mod is offline Zen Mod  Serbia
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considering that you're probably needing to order some more parts , just order regular TL431 ....... not worth banging da head ......
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Old 19th April 2018, 09:07 PM   #4400
Dennis Hui is offline Dennis Hui  Canada
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Short answer: What ZM said.

Slightly longer answer: It seems the TLV431 has a max regulated voltage of 6V. The F4 schematics,
with TL431 shows an adjustment range of around 7 to 9.4V and you probably need that to bias up the output mosfets.
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