Thanks, but I am afraid you are missing the point. I like the factory Aleph 3 very much and do not want to change it. I know Nelson has suggested improvements in the Aleph series (replacing the frontend 910 by ZVP or Toshiba JFet) but I like the Aleph 3 the way it is.
When I hooked up my F4's I noticed that they were very laid back compared to my diy Aleph 2's.
I am trying to find out if the Aleph 2 design sounds significantly different (than the Aleph 3) with respect to perceived laid back sound or if in my diy Aleph 2's it is due to parts used.
Perhaps someone who has heard both the factory Aleph 2 and factory Aleph 3 can help?
Aleph 2 is likely to sound more transparent and authoritive and dynamic, the Aleph 3 is likely to sound more lush but less authoritive and dynamic.
Best to start a new thread.
I have a diy Aleph J but prefer the factory Aleph 3
Aleph J is not really suitable at all for Maggies, Aleph 3 is a better match, that is why I said, when matched with suitable speakers, people prefer Aleph J over the original Aleph - in your case, Aleph J would be not appropriate at all.
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Input level for F4
This is my first post in diyaudio.com so please forgive me if I'm posting a wrong thread.
I've the opportunity to buy a F4 at a reasonable price, I don't think my source will have adequate voltage swing so I need some gain. I'm wondering if a Lundahl LL7906 trafo at the input of the F4 could be a feasible solution? Has anyone used a transformer this way?
Or should I rather go for a little line stage with Burton Audio discrete op-amps Supreme Sound Opamp V6 – Burson Audio?
I guess both solutions can be implemented for around $300,- Other suggestions in that price range?
Pelvez
This is my first post in diyaudio.com so please forgive me if I'm posting a wrong thread.
I've the opportunity to buy a F4 at a reasonable price, I don't think my source will have adequate voltage swing so I need some gain. I'm wondering if a Lundahl LL7906 trafo at the input of the F4 could be a feasible solution? Has anyone used a transformer this way?
Or should I rather go for a little line stage with Burton Audio discrete op-amps Supreme Sound Opamp V6 – Burson Audio?
I guess both solutions can be implemented for around $300,- Other suggestions in that price range?
Pelvez
I see that the Burson op amps have a maximum supply voltage of +-16.5 volts, so no matter how much gain you give the op amp you still cannot swing the +-20+ volts you need to drive an F4 to full power. Assuming +-15volts from the Burson you are looking at 10.6 volts out or about 14w into 8 ohms.
You could attempt to use a transformer in step up mode, but that needs to be carefully optimized in terms of the load on the secondary, the source impedance and you need to pick the right transformer with the ability to output 20+ volts rms with low distortion.
I believe there are some DIY choices in Solid state and tube for a preamp. The BA3 front end as a preamp is one choice. It’s not too expensive to build and when powered by +- 24volts or more is able to get you all the power you are paying for in a standard F4 build.
You could attempt to use a transformer in step up mode, but that needs to be carefully optimized in terms of the load on the secondary, the source impedance and you need to pick the right transformer with the ability to output 20+ volts rms with low distortion.
I believe there are some DIY choices in Solid state and tube for a preamp. The BA3 front end as a preamp is one choice. It’s not too expensive to build and when powered by +- 24volts or more is able to get you all the power you are paying for in a standard F4 build.
If you do decide to further pursue the transformer route, you should probably just start a new thread. I asked a similar question earlier for a special use case (bumping up voltage for a subwoofer channel) but it's just not something most people with F4s do.
When you make the thread, be sure to list the output impedance you'll be feeding the transformer, the input impedance it'll be driving (stock f4 is 47k), V in, and V out (+/- 20 for the f4).
The Lundahl looks interesting, but in the thread I found on the topic, the consensus was just to contact the manufacturer and ask if it would work. When I started going down this path it quickly became clear there were a lot of issues to check out and I got discouraged. Please do report back if you find a confirmed transformer based solution.
That´s why I was asking about an F4 with one output pair and not about M2.
2Vrsm are plenty for me too no gain needed from autotrasphormer.
Does the F4 really needs 3 pairs of output devices?
How would be bass with only 1 pair? damping factor too low?
Damping would be lower. Since you don’t have any feedback, the properties of the output stage fets are all that gives you damping. So I would guess that Zout would be roughly 3 times what it would be with 3 pairs of FETs. It would be interesting to re bias a single pair to a higher current and maybe decrease the source resistors to a lower but still safe value.
If you only need 2 v rms for full volume I can understand why you would want to keep the circuit as simple as possible. Your speakers must be high efficiency and like a magnifying glass for low level amplifier sound quality. You could also reduce the power supply voltages a bit given that 2v rms is only + or - 3 volts peak. That may allow you to increase bias current further while staying within a reliable level of power dissipation.
Aside from output impedance, when you parallel devices there is proportionally less nonlinearity for any given output level or in other words, less distortion.
If your speakers are tube friendly there may not be an issues associated with a higher Zout. Build it with one pair and then you could add more if needed.
If you only need 2 v rms for full volume I can understand why you would want to keep the circuit as simple as possible. Your speakers must be high efficiency and like a magnifying glass for low level amplifier sound quality. You could also reduce the power supply voltages a bit given that 2v rms is only + or - 3 volts peak. That may allow you to increase bias current further while staying within a reliable level of power dissipation.
Aside from output impedance, when you parallel devices there is proportionally less nonlinearity for any given output level or in other words, less distortion.
If your speakers are tube friendly there may not be an issues associated with a higher Zout. Build it with one pair and then you could add more if needed.
And that lack of distortion is the secret sauce, along with no VAS = the magic of the F4 = no sonic signature = it sounds like the source.
So, if you hang a single pair on the output, it may not be as clean. OTOH, it might be to your liking. However, I would first build it as Papa designed it. It's a no brainer designed by a serious brain.
So, if you hang a single pair on the output, it may not be as clean. OTOH, it might be to your liking. However, I would first build it as Papa designed it. It's a no brainer designed by a serious brain.
