A friend have this beautiful preamp, Wyetech Opal with 6SN7 tubes and sounds really awesome, the circuit is so minimalist and simple that I came to think if there is something in the DIY community that could be done.
I would like to know if there is some kit for DIY with the same topology, it's a damn good sounding preamp, but it's damn expensive also...
I will post pictures of the interior.
Murillo
I would like to know if there is some kit for DIY with the same topology, it's a damn good sounding preamp, but it's damn expensive also...
I will post pictures of the interior.
Murillo
"The Opal's circuit is based on a grounded grid configuration which is isolated by a cathode follower stage before and after. All three stages are non-inverting, maintaining absolute phase. (The grounded grid configuation is known for its extremely wide bandwith). The grounded grid stage drives two cathode followers and provides two isolated outputs for each channel. All stages are DC coupled and only one capacitor is employed in the output stage for DC blocking. No feedback is employed in this dual mono construction with separate circuit boards for each channel. Four 6SN7 (dual triode) and one 6X5 dual triode are used in the Opal. There is an automatic power sequence and muting function which delays operation by about seventy seconds to bring the up voltage to 200 volts. After about ninety seconds the auto mute is disengaged, completing the turn-on sequence. Muting is accomplished with a four pole relay that shorts the preamplifier outputs. When disengaged, the muting circuit is not in the signal path. Frequency response (reference to a 3.5 V RMS output sine wave) is +/- 0dB flat from 20Hz to 100kHz, +0dB/-1dB from 6kHz to 375kHz, +0dB/-3dB from 2.6Hz to 750kHz. Input impedance is 50 kW. The master gain control (left and right channel) is variable from 9dB to 15dB (seven steps of 1dB each). Attenuation is achieved via a 24 position stepped voulme control (12 at 1.5dB/step). Output impedance is 425 W, rated output is 3.5 V RMS (maximum 20 V RMS). Slew rate is greater than 40 volts per microsecond. These are two preamp outputs, one tape output, one line level output. Four line (high) level inputs and a tape input are supplied. Power requirements are selectable at 115/230 volts. 50/60Hz, 50 watts.
The power supply is made up of three filtering stages with the final stage a non-magnetic RC filter network. Each channel board has its own large value polypropylene capacitor as a final shunt bypass cap. The unit eliminates all noise and ripple on the DC 200 volt line and maintains regulation of the votage to within 0.002 volts/second of drift. Theoretically, this power supply far outperforms a battery pack and may be the realistic reason for the preamp's quiet operation. All in all, this unit has been overbuilt with top quality parts and craftsmanship. The smallest details have been addressed to assure mechanical integrity. The Opal's electrical and mechanical structure is in line with the classic appearance, but the nitty gritty is how it handles music." (Wyetechlabs)
The power supply is made up of three filtering stages with the final stage a non-magnetic RC filter network. Each channel board has its own large value polypropylene capacitor as a final shunt bypass cap. The unit eliminates all noise and ripple on the DC 200 volt line and maintains regulation of the votage to within 0.002 volts/second of drift. Theoretically, this power supply far outperforms a battery pack and may be the realistic reason for the preamp's quiet operation. All in all, this unit has been overbuilt with top quality parts and craftsmanship. The smallest details have been addressed to assure mechanical integrity. The Opal's electrical and mechanical structure is in line with the classic appearance, but the nitty gritty is how it handles music." (Wyetechlabs)
A cathode follower followed by a grounded grid is what I call a short tail pair; also known as a cathode-coupled amplifier. It is true that this type of circuit has high bandwidth but this is irrelevant for audio, apart from its advantage in marketing.
There are DIY circuits using a similar arrangement. Many use feedback to the "grounded" grid, so it is actually a cathode-coupled circuit even though it is often called "grounded grid".
There are DIY circuits using a similar arrangement. Many use feedback to the "grounded" grid, so it is actually a cathode-coupled circuit even though it is often called "grounded grid".
I know this design, is very well build and respected, where can I find a decent assembled one? I do not have the skills to build one.
thx
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Sorry for the bad quality, I made with my iphone.
Next time I will use my nikon d600
Maybe he lives in a humid environment. It looks like rosin. Next time you re there, try to scratch it, it will flake and come off. Make sure there is no power!
It actually is generic turret board+turrets. Very easy to make. But, if you are looking for a pre-built kit, you are in the wrong place...
It actually is generic turret board+turrets. Very easy to make. But, if you are looking for a pre-built kit, you are in the wrong place...
We live near the sea, this is just a precaution.
As for the diyaudio is a wrong place to look for pre-built kit, you are right, I will ask this is Craiglist, maybe there are humans there.
As far as I know, Glassware audio sales only kits, not complete build preamp. If you are skilled enough to build from kit, then you are set
. There are some people on this forum who can build it for you, but you must search.What is the reasoning behind the increased bandwidth? The manufacturers website contradicts itself.
" We've retained the grounded grid configuration which we deem to be the best possible circuit topology for line level amplification. Having only one buffered output allowed us to reduce the tube count to three double octal based triodes. This circuit, like the Opal, maintains an exceptional bandwidth that extends well beyond 250,000Hz. Our primary design philosophy that less is better than more has been fully developed in the Jade preamp."
"He also was aware of the reason for single ended amplifiers generally being branded as having poor low frequency response. The designs that he investigated had two common design weaknesses. The first problem is that they were not using enough iron in their transformers. They are sacrificing the low frequencies in order to attain an extended frequency response of 50 kHz or beyond. We have chosen to ignore this golden rule of the technocrats and believe that a response that starts to fall off at 25 kHz is all that is required to get the best sound possible from single ended tube amplifiers."
" We've retained the grounded grid configuration which we deem to be the best possible circuit topology for line level amplification. Having only one buffered output allowed us to reduce the tube count to three double octal based triodes. This circuit, like the Opal, maintains an exceptional bandwidth that extends well beyond 250,000Hz. Our primary design philosophy that less is better than more has been fully developed in the Jade preamp."
"He also was aware of the reason for single ended amplifiers generally being branded as having poor low frequency response. The designs that he investigated had two common design weaknesses. The first problem is that they were not using enough iron in their transformers. They are sacrificing the low frequencies in order to attain an extended frequency response of 50 kHz or beyond. We have chosen to ignore this golden rule of the technocrats and believe that a response that starts to fall off at 25 kHz is all that is required to get the best sound possible from single ended tube amplifiers."
As far as I know, Glassware audio sales only kits, not complete build preamp. If you are skilled enough to build from kit, then you are set
Thx kacernator, I always believed that there are humans here also... You are one of them
Thx kacernator, I always believed that there are humans here also... You are one of them
Unfortunately I do not have time to make one for you. I suggest you to try building one yourself. Star cheaply - 9pin tubes, regulated B+ (Maida reg.), regulated heaters (LM338), ALPS pot, and no fancy resistors or caps. It is possible to build aikido preamp for about 250 Eur with excellent sound quality.
Later you can upgrade resistors, caps etc., if you think it is worthy (I do not think so).
it sounds as a clone from the grounded grid pre amp from Rosenblitz
Transcendent Sound Grounded Grid Preamp
Transcendent Sound Grounded Grid Preamp
A different animal, I had a GG and it sounds complete different. Maybe the topology is similar but not the sound.
Thank you very much for your help, I took a look at the site and asked them about the dual mono version, it looks killer! I will try to find someone who can build to me here, the power supply you advice is what? External? Ac or dc in the heaters?
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