Hi,
I would like to start a new project. Make Aleph amplifier as guitar power amp. I need about 70W / 8 Ohm, 140 / 4 Ohm.
I will need to raise output impedance to 4 Ohms. This will be done via mixed-mode feedback. I will also lower standing bias current a bit to lower dissipation.
Which version of Aleph would be most suitable?
Thank you.
I would like to start a new project. Make Aleph amplifier as guitar power amp. I need about 70W / 8 Ohm, 140 / 4 Ohm.
I will need to raise output impedance to 4 Ohms. This will be done via mixed-mode feedback. I will also lower standing bias current a bit to lower dissipation.
Which version of Aleph would be most suitable?
Thank you.
introducing mixed mode feedback demands some level of expertise
if you have that , you're able to calc current and voltage demands for intended RMS power
not disputing , just pointing on possible problems
if you have that , you're able to calc current and voltage demands for intended RMS power
not disputing , just pointing on possible problems
The project is propably not good idea, push-pull output stage would be better as it can deliver twice the standing current.
you probably know that for guitar amp , power isn't most prominent virtue
better speaker and better tone is worth chasing
instead of power , better to play with Aleph CCS current gain and possible pure SE mode
one channel of Aleph 4 ............. or - other direction - crippled F4 (BA 3 OS too) with slight changes for increased PSU voltage , driven with appropriate (tube ?) gain stage
better speaker and better tone is worth chasing
instead of power , better to play with Aleph CCS current gain and possible pure SE mode
one channel of Aleph 4 ............. or - other direction - crippled F4 (BA 3 OS too) with slight changes for increased PSU voltage , driven with appropriate (tube ?) gain stage
FWIW I copied and pasted this from an Aleph X 100W RMS construction page:
So a 140W amp is doable, nobody argues that, it will probably also sound very good, just not very practical.
So a 140W amp is doable, nobody argues that, it will probably also sound very good, just not very practical.
I already have Rocktron Velocity 120, which is all bjt class AB power amplifier for guitar. It makes 120W into 8 Ohms.
I know that Aleph will not be too practical, but I think it should sound HUGE with guitar. Heatsink is not problem, I would use temperature controlled fan, noise is not problem with loud guitar 🙂.
Interesting is output impedance. Some SS power amps raise output impedance with mixed-mode feedback to about 4 Ohms. BUT some highly regarded SS guitar amplifiers have very low output impedace - Matrix GT800FX and Rocktron Velocity. They propably emulate effect of higher output impedance with some internal EQ tweaking.
Now, do I need to raise output impedance or just use stock Aleph 3 and then possibly tweak?
I know that Aleph will not be too practical, but I think it should sound HUGE with guitar. Heatsink is not problem, I would use temperature controlled fan, noise is not problem with loud guitar 🙂.
Interesting is output impedance. Some SS power amps raise output impedance with mixed-mode feedback to about 4 Ohms. BUT some highly regarded SS guitar amplifiers have very low output impedace - Matrix GT800FX and Rocktron Velocity. They propably emulate effect of higher output impedance with some internal EQ tweaking.
Now, do I need to raise output impedance or just use stock Aleph 3 and then possibly tweak?
I was also thinking about tube preamp driving F4. Don´t know what would be sonically better. F4 (PP) without any feedback or Aleph (SE) with feedback. I am leaning towards SE.
F4 will have gain stage character
so , good guitar pre ........ and you're in game
besides that - source follower stage (F4) is easy and safe for Iq decreasing
so , good guitar pre ........ and you're in game
besides that - source follower stage (F4) is easy and safe for Iq decreasing
The Aleph is not a good choice because it must be Class A. I built something like the Aleph that was 50W/4ohm on a CPU heatsink. It runs hot and will probably catch on fire when the fan stops. The F5 Turbo can be setup to transition to Class AB, that will allow you to reduce bias current and use smaller heatsinks. You'll need 40V rails and that means a cascode input stage. You need to be aware that too much input voltage from a tube preamp will kill the input JFETs. Use zener diodes to clamp the input to a safe level.
F5 seems to be better suited. Can I implement current feedback into F5? Ground speaker through 0.1R 5W resistor and from this junction connect two resistors - each to one JFETs source.
That type feedback should work but you will need to experiment with the value. I suspect the resistance will need to be higher. 5W probably won't be enough. Leave room for two or three 10W resistors in parallel.
Hi,
FWIW unless its valve and your into valve output stage
distortion, Class A, as transistor/Fet has very little merit
for a guitar amplifier, unless its very classy acoustic.
rgds, sreten.
Mixed feedback can adjust output impedance, but its just EQ.
FWIW unless its valve and your into valve output stage
distortion, Class A, as transistor/Fet has very little merit
for a guitar amplifier, unless its very classy acoustic.
rgds, sreten.
Mixed feedback can adjust output impedance, but its just EQ.
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I don´t think so. I am into more high gain / metal territorry and with this type of distortion poweramp distortion is not so much desirable.
I think you can get pretty close with EQ to simulate higher output impedance, but I don´t think it is the same. Because when speaker is not so much controlled by the amp, it´s interaction with speaker cabinet will be different, but this effect could be neglible, I don´t know.
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