I've been reading a lot about the diy F5 and so far I like what I've read. I like the philosophy behind First Watt. I'm about ready to hit check-out at the diyAudio Store but I have a few questions that I have been unable to answer through this forum/internet searches. Although its diy, it's still a significant investment to build one of these amps and I'd like to avoid a potential mismatch before I do. I plan to buy/build the F5 and the B1 based on the current version of the original plan. My system is vinyl only. I have a high quality front end: Goldring Ethos MC Cartridge and a TriChord Diablo phono preamp. My speakers are Harbeth shl5+. My amp is an old Yamaha M-40 paired with the passive Yamaha MVS-1.
Will the F5/B1 be an upgrade to my M-40/MVS-1?
Does anyone have experience pairing the First Watt F5 with the Harbeth shl5+ speakers?
How does the F5 compare with the dual mono version of ACA? Is this even a fair comparison?
Any advice will be very much appreciated, even if it means I'm better off heading in a different direction. Thank you in advance.
Will the F5/B1 be an upgrade to my M-40/MVS-1?
Does anyone have experience pairing the First Watt F5 with the Harbeth shl5+ speakers?
How does the F5 compare with the dual mono version of ACA? Is this even a fair comparison?
Any advice will be very much appreciated, even if it means I'm better off heading in a different direction. Thank you in advance.
You should know the F5 and most other FW stuff has quite a lot less gain than a typical amp, so you'll need to make that up somewhere.
The B1 Korg is a wonderful match with the F5. The F5 only has 15db gain so with lower sensitivity speakers then you might need more gain than the normal B1 (no gain) to drive to loud levels. Assuming you like it loud.
F5 will need an active preamp in that situation...especially w/phono. It will make sound w/a passive but you won't get the full experience.
Korg B1 is a good choice and inexpensive.
Korg B1 is a good choice and inexpensive.
Let’s do some math and help this guy out.
The Yamaha M-40 was famous in the ‘80s and it put out 120 watts/8 ohms with an input sensitivity of 1.07Vrms. That basically translates into 29dB of gain which is not unusual for the time.
With 86dB sensitive Harbeth speakers that have benign impedance and phase angles (see Stereophile measurements), I think the F5 will work nicely from a power output standpoint. That being said, the 15dB of overall gain will need to be brought up since the OP is used to 29dB. That leaves a few choices. I would aim for a preamp with at least 10dB gain and preferably more. So a minimum total of 26dB with both the F5 and preamp put together is a good goal.
The Korg B1 is available as a full kit and probably built easily by a newbie. Notice the OP just created his account on August 9 2021 (I apologize if I am assuming too much!). The Korg B1 has an overall gain of about 16dB. 16 + 15 = 31dB and with a phonostage as a source it is all the more important to have enough overall gain in the whole playback chain since phonostage outputs are typically less than 2V rms (not to mention the differences in playback volumes of different LPs). This becomes even more important with less sensitive speakers.
As to the sonics, I surmise the F5 will most likely crush the Yamaha with extreme prejudice. We won’t talk about the ACA and F5 in the same sentence ;-)
Best,
Anand.
The Yamaha M-40 was famous in the ‘80s and it put out 120 watts/8 ohms with an input sensitivity of 1.07Vrms. That basically translates into 29dB of gain which is not unusual for the time.
With 86dB sensitive Harbeth speakers that have benign impedance and phase angles (see Stereophile measurements), I think the F5 will work nicely from a power output standpoint. That being said, the 15dB of overall gain will need to be brought up since the OP is used to 29dB. That leaves a few choices. I would aim for a preamp with at least 10dB gain and preferably more. So a minimum total of 26dB with both the F5 and preamp put together is a good goal.
The Korg B1 is available as a full kit and probably built easily by a newbie. Notice the OP just created his account on August 9 2021 (I apologize if I am assuming too much!). The Korg B1 has an overall gain of about 16dB. 16 + 15 = 31dB and with a phonostage as a source it is all the more important to have enough overall gain in the whole playback chain since phonostage outputs are typically less than 2V rms (not to mention the differences in playback volumes of different LPs). This becomes even more important with less sensitive speakers.
As to the sonics, I surmise the F5 will most likely crush the Yamaha with extreme prejudice. We won’t talk about the ACA and F5 in the same sentence ;-)
Best,
Anand.
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This is great! Thanks guys. It seems I am wrong, which means I'm learning... I found a significant increase in sound quality after my last preamp died and rather than let my system sit idle while looking for a replacement, I plugged my phono stage directly into the m-40. What I found was that things sounded much better at a low volume than they did using a preamp (and better overall, especially after increasing the output gain of my phono stage). Thats when I found out about First Watt, after I did a little searching to find out if low level systems were a thing. Its also how I found this forum. So yes, I am new here and new to diy so this help is particularly useful to me at this point. I'm excited to finalize my order for the F5 and Korg B1 (and sell all my vintage gear).
Welcome!
We'll see you over one of the Korg B1 threads - I would suggest you build that first to get your feet wet.
Best,
Anand.
We'll see you over one of the Korg B1 threads - I would suggest you build that first to get your feet wet.
Best,
Anand.
Hi, something to consider (or not). I have a Korg B1 which I've tried between a Rega P3 turntable with an Ortofon 2M bronze MM cartridge, Rega Fono Mini phono stage, and an ACA, powering either some small Klipsch bookshelves or the Seas A26 Dynaco clone kit speakers. I've substituted in two different passive preamps in place of the Korg B1- a Schiit SYS (just a 10k audio taper pot) and a homebrew preamp using the Electra-Print PVA-2n 1:8 audio transformers and Jack Eliano's circuit, also with a 10k audio taper pot for gain control. Here are my impressions.
The Rega/Ortofon/Rega combination sounds fine with a passive preamp, best with the trafo preamp (louder, more detailed bass with zero perceived increase in distortion as volume goes up), and worst with the Korg B1. The Korg B1 simply sounds too 'record-y' in my system, with loss at the high and low end and more coloration in the midrange. My pet theory is that the RIAA equalization process seems sensitive to losses at the high and low end and is already quite optimal in this admittedly mid-level Rega system. Why the little trafos help the sound, I don't know, but they seem to. YMMV, your system is and will be higher end than mine, but it might be worth seeing if you can borrow a B1K to try before you commit.
The Rega/Ortofon/Rega combination sounds fine with a passive preamp, best with the trafo preamp (louder, more detailed bass with zero perceived increase in distortion as volume goes up), and worst with the Korg B1. The Korg B1 simply sounds too 'record-y' in my system, with loss at the high and low end and more coloration in the midrange. My pet theory is that the RIAA equalization process seems sensitive to losses at the high and low end and is already quite optimal in this admittedly mid-level Rega system. Why the little trafos help the sound, I don't know, but they seem to. YMMV, your system is and will be higher end than mine, but it might be worth seeing if you can borrow a B1K to try before you commit.
On sound it will surely crush the yamaha (which is not a bad amp at all on it's own), the question is can it be loud enough for you. The technical explenation is above, the decision is yours...
Possible you combined one power amp w/heavy 2nd harmonics (ACA) with a preamp with heavy 2nd harmonics (Korg) which resulted in too much 2nd harmonic distortion. Results will likely be different with a clean power amp like the F5 and the Korg B1. Also possible you didn't invert the polarity of the ACA when using the Korg?
It's worth remembering that the Korg is a bit of a novelty act. Some
love it, some don't. I gave one to a friend of mine, and he reports that
it is way too bright.
Does anyone have experience pairing the First Watt F5 with the Harbeth shl5+ speakers?
Yer good match I was told,
The agent in NZ sells Passlabs Firstwatt and Harbeth he reckons the F5 is a good match with Harbeth
Yer good match I was told,
The agent in NZ sells Passlabs Firstwatt and Harbeth he reckons the F5 is a good match with Harbeth
Yes, I'm aware of the 'one voice' hypothesis, but what I didn't mention out of brevity and relevance is that my B1K, tuned for negative 2nd harmonic with 9.5V of bias, sounds *great* when used between either of my two DACs and the ACA. I used it in this manner for a number of months. The B1K also helps the sound of my Sony CD player but nowhere near as much as the transformer-based passive preamp does. So to be clear, my commentary was specifically on the use of the B1K downstream of vinyl, per the OP's question, where I've have a very different experience than I've had downstream of digital sources.
While I didn't try inverting the polarity between the B1K and the ACA, I did once try inverting the polarity of the ACA at the speakers (in essence the reversing the polarity inversion inherent in the v1.8 wiring diagram), when the B1K was upstream of it. Doing so completely destroyed the soundstage, I felt like I was listening in mono.
It's worth remembering that the Korg is a bit of a novelty act. Some
love it, some don't. I gave one to a friend of mine, and he reports that
it is way too bright.
I appreciate that Mr. Pass, and thank you for designing and building it for us all. It's been a fun and educational item for me and it does in my experience improve the sound of my digital sources when also paired with an ACA.
What's interesting to me though is the observation that I like the sound of a transformer in the line stage. In comparison to the Nutube triode, it leads me to wonder how much of the 'tube sound' is from the tubes themselves or transformers in the signal path?
I should add, one of my DACs is "goofy" in that it has an output Z >500R per the manufacturer. The ACA has an input Z of 10k, and when you put a passive preamp with a 10k pot in it between the two, you're cutting the voltage the ACA gets in half as I understand it (I'm modeling the passive preamp + ACA as two 10K R resistances more or less in parallel at full volume). Maybe one reason this combination sounds better with the B1K in between is the much gentler input Z of ~50k that the B1K presents to this DAC, coupled with the much better output Z of 170R that the B1K presents to the ACA. So the perceived improvement in sound might not have much to do with the distortion characteristics of the NuTube in the middle of this impedance buffering.
I just had the same experience with my brother. He was using the BA-3 as preamp (P3 turned to about midpoint). I gave him the B1K to try and his first comment was that the Korg preamp was brighter. I found it to be exactly the opposite in my system.
Since you have recently tried your system phonostage direct without an intervening preamp, and you find that to be sonically “palatable”, a decent compromise with regards to balancing transparency and overall gain could be the ACP+:
ACP+ (Amp Camp Pre-Amp + Headphone Amp) – diyAudio Store
It’s 9dB gain with an output impedance of 0.8 ohms. It also doubles as a headamp. I personally love the “see through look” of the fully built ACP+. Building it in a plexiglass enclosure would be sweet.
The F5’s 15dB gain plus 9 dB from the ACP+ is 24dB which may be just right for you.
As you have realized, there is an important interplay between overall gain (after the source), sensitivity of speakers, listening position and adequate SPL capabilities at that listening position.
Now if you have a buddy that can build you a TVC preamp with some gain that might be best but I am keeping in mind that you are a diy newbie who has a finite budget and you are on the Pass subforum 😉
Best,
Anand.
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