That's easy - in your F5, change R5, R6, R7, R8 to 220ohm 3W. It will decrease the feedback a bit and increase the gain to better match a 'normal' amplifier.
I just did a transformer coupled SE tube preamp with 6SN7 and Sowter 8650. It didn´t turn out very well, so I will not pollute the thread with that one. High amplification, but distorted sound.
... But I took out an Aikido 6SN7 preamp I build some time ago. I sounds very good, and measures incredibly well.
I just bought a Rigol 1022 signalgenerator and own a 100 MHz analog Tektroniks scope. I hooked up the Aikido and did some measurements, and I couldn´t believe how good they were. Sinus: Linear from 1 Hz to 20 KHz, still OK @ 100 KHz. 2 division out of 6 down @ 200 KHz and half output @ 300 Khz.
Obvious that I at the moment am not able to do the dB calculation, isnt it
What about square waves then: Nice @ 5 Hz, very nice @ 10 Hz, very clean @ 30 Hz to 20 KHz, OK @ 50 Khz, ramping @ 100 Khz.
Is everything good then ? No, it doesnt drive longer cables very good. For different reasons I have 5 m signal cables between my preamp and my F5, and only the tweeters did play
... But I took out an Aikido 6SN7 preamp I build some time ago. I sounds very good, and measures incredibly well.
I just bought a Rigol 1022 signalgenerator and own a 100 MHz analog Tektroniks scope. I hooked up the Aikido and did some measurements, and I couldn´t believe how good they were. Sinus: Linear from 1 Hz to 20 KHz, still OK @ 100 KHz. 2 division out of 6 down @ 200 KHz and half output @ 300 Khz.
Obvious that I at the moment am not able to do the dB calculation, isnt it
What about square waves then: Nice @ 5 Hz, very nice @ 10 Hz, very clean @ 30 Hz to 20 KHz, OK @ 50 Khz, ramping @ 100 Khz.
Is everything good then ? No, it doesnt drive longer cables very good. For different reasons I have 5 m signal cables between my preamp and my F5, and only the tweeters did play
If you're running about 7mA thru the front gain stage and the o/p buffer pair, the gain will be around the 10 - 15dB area (you only need about 6dB with 2V signal) and the o/p impedance should be around the 600 ohm mark - still quite okay for driving long interconnects into the 100kR load of the F5 amp inputs.
Perhaps you might check that there's enough current going thru those 6SN7s? Or that the interconnect is a good one .....
Curiously, the DC B1 has an o/p Z of about 200R and drives long cables quite well.
Perhaps you might check that there's enough current going thru those 6SN7s? Or that the interconnect is a good one .....
Curiously, the DC B1 has an o/p Z of about 200R and drives long cables quite well.
Andrew,
the output impedance of the Akaido preamp should be 500 ohms, according to documentation, which I think is ok low.
The cables were 5 m QED cables, I have no specs on capasitance, but it showed up that the sound is fantastic with a pair of similar 1 m QED cables.
My system is not placed as it will be when I am finished ... if I ever will be
the output impedance of the Akaido preamp should be 500 ohms, according to documentation, which I think is ok low.
The cables were 5 m QED cables, I have no specs on capasitance, but it showed up that the sound is fantastic with a pair of similar 1 m QED cables.
My system is not placed as it will be when I am finished ... if I ever will be
jameshillj,
you could be correct about the interconnects, but my my Musical Fidelity´s preamp could easily drive them.
I took the transformercoupled preamp apart yesterday, and today I got PCBs from The Shop for a BA-3. which could be ready for testing tonight. I need to match the FETs and put them in.
I decided to try a couple of 180 ohms source resistors to keep the gain down.
you could be correct about the interconnects, but my my Musical Fidelity´s preamp could easily drive them.
I took the transformercoupled preamp apart yesterday, and today I got PCBs from The Shop for a BA-3. which could be ready for testing tonight. I need to match the FETs and put them in.
I decided to try a couple of 180 ohms source resistors to keep the gain down.
When I have decided which of the preamps I will go with, I will put in a switched relay attenuator from a small danish company called Dantimax.
He makes unbalanced and balanced attenuators with remote controls and optional LCD displays, to very reasonable prices.
It is however not that easy to find out what to put together for a working system.
He makes unbalanced and balanced attenuators with remote controls and optional LCD displays, to very reasonable prices.
It is however not that easy to find out what to put together for a working system.
There is a HUGE difference in the 2 amps indeed - the Aleph amps are much slower and have a somewhat 'fatter' sound (that active CCS) in comparison so, yes, the F5 will sound a lot 'thinner' and clinical.
BUT - the F5 is very dependent on the power supply components and if you use a single cheap transformer, single basic GB block bridge and cheap power supply caps, this is where much of the 'thin sound' comes from, plus the use of wirewound power source resistors, like Mills, some basic resistors (china kits), etc in the amplifier itself emphasises this 'sound'
However, some hifi systems find this extra 'brightness' useful to complement other components in the system so this should be regarded as a 'build characteristic' rather than a 'bad sound' and some people just like a bright sound anyway.
My first kit F5 came from "Jim's Audio' in china and with a cheap 'junk' power supply sounded just like the classic 'thin, hard fet amp' but mated up quite well to an old pair of Wharfdale speakers - later on, this was gradually upgraded with better components and is now a much smoother amplifier matched up to a pair of Harbeths .
BUT - the F5 is very dependent on the power supply components and if you use a single cheap transformer, single basic GB block bridge and cheap power supply caps, this is where much of the 'thin sound' comes from, plus the use of wirewound power source resistors, like Mills, some basic resistors (china kits), etc in the amplifier itself emphasises this 'sound'
However, some hifi systems find this extra 'brightness' useful to complement other components in the system so this should be regarded as a 'build characteristic' rather than a 'bad sound' and some people just like a bright sound anyway.
My first kit F5 came from "Jim's Audio' in china and with a cheap 'junk' power supply sounded just like the classic 'thin, hard fet amp' but mated up quite well to an old pair of Wharfdale speakers - later on, this was gradually upgraded with better components and is now a much smoother amplifier matched up to a pair of Harbeths .
You aren't missing anything. But an Aleph J with suitable JFET and MOSFET will be more accurate than the Aleph Series.
Speaker issue is often amplifier issue as well. Aleph amps (may exclude the multi output devices such as A2 or A4) cannot drive active load as good as F5.
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