The only place where those whole systems might be ok are HiFi Shows or any other place where room acoustics is an optional....😀
I gave an opinion.
Yes, the logic. We are talking about the Mentor preamp kit that should be mated to its Mentor power amp. Were is the logic of a high gain preamp....with faulty expensive resistors (because someone already told him that the noise is likely due to that)....mated to a "complicated" 2 stage-2 tubes single ended amplifier where the input/driver is the 6SH7 pentode (connected as such)? I can only see the logic of squeezing out as much money as possible.
I just cannot imagine how bad it can be if one choses the 2A3. Pentode+ 2A3 is already integrated amp or nearly so....so yes, we are trying to re-design that preamplifier. 😀
Last edited:
@45
Dear Sir, I am open to suggestions to improve the design for the preamp, and the amp as well. I didn't want to provide any further info about the preamp was mainly because I got a feeling that the price could bring certain types of bias into thoughts/opinions, which may result inefficient communications.
Rather than focusing on the brand/price, I would be very happy to learn how to improve a design/circuit. If you know and would like to share, that will be great!
Thx.
Dear Sir, I am open to suggestions to improve the design for the preamp, and the amp as well. I didn't want to provide any further info about the preamp was mainly because I got a feeling that the price could bring certain types of bias into thoughts/opinions, which may result inefficient communications.
Rather than focusing on the brand/price, I would be very happy to learn how to improve a design/circuit. If you know and would like to share, that will be great!
Thx.
I found this and got distracted around the concept of transformers in the passive device, but these seem super expensive.....any thoughts on SQ and the chance of a small up in gain and implied dynamics?
Any experience here?
Shootout Test | Eleven Passive Preamps with Transformers
Any experience here?
Shootout Test | Eleven Passive Preamps with Transformers
whenever you say you want to improve any design, first you must be able to say what seems to be wrong or insufficient in the existing design to begin with....what are you trying to achieve?
if you have the answers to this question, then perhaps we can help....
if you have the answers to this question, then perhaps we can help....
If you are open to suggestions it is strange that you ignore comments and don't reply to simple questions. You focus on changing a randomly bought device (with apparently random specifications) which was not matched beforehand to the existing chain and ended up with detrimental properties and then you thought changing it is the solution. You don't provide the necessary information of the chain as well. This is exactly wat causes inefficient communications, bravo! See post #45 for criteria to select stuff.
If a situation does not work out, go outside for 15 minutes and take a deep breath of fresh air. Go back inside and re-evaluate where the fault was introduced. Eliminate the fault and test again. It is really that simple.
Last edited:
There are many reasons why an expensive, high end preamp such as the SP8 may not be a perfect end product, especially as time passes. Marketing and the mixing of SS and tube technologies could be one of them. And there are many more, eg. too much gain as the system evolves and more sensitive speakers that you really like the sound of come along.
You know you would have to spend an awful lot of money, with no guarantees, to buy a more suitable preamp with the SQ the ARC SPs have, so why not try to adapt it to be more useable with your present set-up yet retain or even improve the already excellent SQ in your system.
You don't always have to start from scratch, I think.
You know you would have to spend an awful lot of money, with no guarantees, to buy a more suitable preamp with the SQ the ARC SPs have, so why not try to adapt it to be more useable with your present set-up yet retain or even improve the already excellent SQ in your system.
You don't always have to start from scratch, I think.
The horror LMAO
The only horror I ever had was blowing opamps with the turn on transient of a tube stage. Replaced it and it's been fine since.
The only horror I ever had was blowing opamps with the turn on transient of a tube stage. Replaced it and it's been fine since.
Have you tried taking some signal from the plate of the second triode, and feeding it into the cathode of the first one?
That would reduce your problem of too much gain, and correct for any noise introduced within the loop, such as the white noise from a gainy tube.
The purchase price seems a bit high for an amp, which you need to modify to make quiet.
In a forum of diy audio nuts you would think that someone would already have suggested a little voltage feedback is exactly what this stage needs. Thats my opinion.
That would reduce your problem of too much gain, and correct for any noise introduced within the loop, such as the white noise from a gainy tube.
The purchase price seems a bit high for an amp, which you need to modify to make quiet.
In a forum of diy audio nuts you would think that someone would already have suggested a little voltage feedback is exactly what this stage needs. Thats my opinion.
Thanks for asking this! Well, I thought I made my point good enough, but probably not. So the the main idea is to remove the noise that is introduced around 6SN7 of the preamp.
I have sent it to one of ANK's official builder to check my build--the build itself should be correct. Of course, I checked it many many times as well. I also worked around 6SN7, I replaced almost all the components on the line stage, filament supply, and even one choke, but turned out to be they were not the source of noise. I also ordered a new main power transformer from Monolith, if that does not help, then there are only two filtering caps and two chokes that I haven't give a touch.
I tried to lower the gain of 6SN7 by paralleling a resistor and a cap next to the plate load. I found out that as long as I can lower the gain a bit, the noise is totally gone, however this way is not very good to lower the gain.
So far, I got two ideas:
1. like what @Rayma said
2. Use the way my friend suggested (attachment below, and it was listed in my first post as well)
I personally prefer to listen opinions based on these two ways. If there is a 3rd way, I would like to hear why it would be better.
Attachments
@kodabmx: it was just teasing. I am sure tube circuits can perform better with solid state regulators and other nice solid state circuitry. The fact that I use this oldfashioned term says something. It is not about topology, it is of course keeping an open view for a good final result. This includes matching gain and impedances (this is why standards are invented). Some don't grasp this and religiously keep trying while not seeing the obvious.
Last edited:
Are you sure that the noise goes away because you are lowering the gain or just because the cap mitigates a faulty 39K resistor as someone else suggested in the other thread? Have you tried to put a different 39K??
@45 Hello Sir, I am very positive about that. And yes, except those 470uF caps, I basically replaced everything on the line board related to 6SN7 and turned out to be a waste of time...
Far from that actually, including the filament supply, and some caps/tubes/chokes in the power supply are replaced as well. The only things that are connected to 6SN7 that have not been replaced are these two 220uF caps, two big chokes, and the main power transformer in power supply.
FYI, I didn't replace these resistors with the original brand (AN) but Takman metal flim resistors--but nothing changed so I switched back...
TBH, I am personally very happy with the sound so far, just the noise is very annoying. Reducing the gain solves the issue, but I would like to find a way that is unlike what I have done before which changed the tone a lot and actually reduces the gain of 6SN7 (only). I am not sure if it really matters, but the original design says no feedback... So I would also prefer to keep the design in this way if possible.
BTW, I am open to suggestions to modify the Mentor 300B, it is what I have to pair with the pre. I ordered some filament boards from tentlabs and hope that can improve the sound, but I know how the input section is designed is probably most important.
Far from that actually, including the filament supply, and some caps/tubes/chokes in the power supply are replaced as well. The only things that are connected to 6SN7 that have not been replaced are these two 220uF caps, two big chokes, and the main power transformer in power supply.
FYI, I didn't replace these resistors with the original brand (AN) but Takman metal flim resistors--but nothing changed so I switched back...
TBH, I am personally very happy with the sound so far, just the noise is very annoying. Reducing the gain solves the issue, but I would like to find a way that is unlike what I have done before which changed the tone a lot and actually reduces the gain of 6SN7 (only). I am not sure if it really matters, but the original design says no feedback... So I would also prefer to keep the design in this way if possible.
BTW, I am open to suggestions to modify the Mentor 300B, it is what I have to pair with the pre. I ordered some filament boards from tentlabs and hope that can improve the sound, but I know how the input section is designed is probably most important.
If you have replaced everything and you are confident then I suggest that you re-build the circuit. You could bypass the first stage with the 6SN7 completely and put the volume control on the grid of the ECC99. That's my first thought.
If you instead want to use the 6SN7 you could configure it like a cathode follower but you will need to put an input capacitor to remove the 39K from the plate and place it in series with the cathode resistor you already have. The grid resistor would be connected anyway between the cathode resistor and the 39K resistor for the correct bias. The cathode capacitor will be removed. The output of the cathode follower is taken from the cathode....
Respect to the ECC99 alone this solution would present easier load to the source as the input capacitance would be much lower.
Also if you decide to go for the ECC99 only you will need to check the voltage supply as it will draw less current and other voltage supplies in the circuit might increase if not regulated.
Respect to the ECC99 alone this solution would present easier load to the source as the input capacitance would be much lower.
Also if you decide to go for the ECC99 only you will need to check the voltage supply as it will draw less current and other voltage supplies in the circuit might increase if not regulated.
Last edited: