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PostPosted: 02 Jan 2021, 15:45 
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Joined: 31 Oct 2010, 20:46
Posts: 77
Location: Calgary, Alberta.
Bruce, I just wanted to thank you for all of your help throughout the years of me (and everyone else) building your circuits and enjoying music, once again.
I have been a audio-junkie for many many years but last night, I brought another person to the tube-side. My girlfriend and I opened a fresh LP of Amy Winehouse, Back to Black Album (The LP is White BTW). She said that she heard instruments and sounds she has never heard before listening to the album on a record.
Thank you again Bruce and have a Merry New year!


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PostPosted: 23 Feb 2021, 14:11 
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Joined: 08 Feb 2021, 20:38
Posts: 8
Hi Members,

Ok, I'm way late discovering this fine Groovewatt RIAA phono preamp build. Looking to get back into tube construction. My background involves working with guitar tube amps and new to the world of stereo hifi tube builds that are designed for playback of vinyl. I do own a Thorens TD 145 MkII turntable and an Ortofon Super OM10 phono cartridge. Looking to build a non-complicated hifi tube preamp and tube poweramp to playback vinyl.

A few of my Ortofon Super OM10 phono cartridge specs are:

-Cartridge type: moving-magnet
-Stylus type: Bonded Elliptical
-Output voltage" > 4 mV @ at 1000 Hz, 5cm/sec.
-Compliance, dynamic (lateral): 25 µm/mN
-Internal impedance, DC resistance: 1 kOhm
-Recommended load resistance: 47 kOhm
-Recommended load capacitance: 200 - 500 pF

Source:
https://www.ortofon.com/om-super-series-p-756

Please forgive the newbie question but I do not see a volume-control on the Groovewatt RIAA phono preamp. How would I control the volume on my system using this Groovewatt RIAA phono preamp? Is this a stand-alone preamp or do I need another preamp after this phono preamp?

Thank you for your patience


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PostPosted: 23 Feb 2021, 16:04 
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Joined: 04 Jun 2008, 20:59
Posts: 4327
Location: Arizona, USA
Hi, the OM10 will be fine. I have an OM30 I occasionally use in my system. Even the lowly OM5 sounds nice through these preamps. Higher end cartridges sound exquisite. There is no volume control as the preamp is designed to feed into the AUX or LINE IN inputs on pretty much any amp. It has a fixed gain and relies on the amp to adjust the sound level. The issue that gives most folks building something like this is hum caused by the parts and wires layout. A poor layout or cruddy build will result in a non-usable phono preamp. I would suggest that you wander back though this thread (huge yes I know) and notice the things that have gone well as those that didn't for various builders. I consider the project as an above average but not expert level for skill. When done properly the preamp is quite excellent and rivals many costing big dollars. Since I can have anything I want......I use a pair of them in my system exclusively.

Good listening
Bruce

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PostPosted: 23 Feb 2021, 20:59 
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Joined: 08 Feb 2021, 20:38
Posts: 8
Hi Bruce,

Thank you for helping me better understand.

gofar99 wrote:
Hi, the OM10 will be fine. I have an OM30 I occasionally use in my system. Even the lowly OM5 sounds nice through these preamps. Higher end cartridges sound exquisite.

Good to know, thank you.

Quote:
There is no volume control as the preamp is designed to feed into the AUX or LINE IN inputs on pretty much any amp. It has a fixed gain and relies on the amp to adjust the sound level.

Question #1
Please help me to understand. Are you saying the Groovewatt RIAA phono preamp feeds into another (standard) preamp that has a volume ? In other words, is the Groovewatt RIAA phono preamp a stand-alone preamp or do I feed this preamp into another line level preamp (that has a volume control) and then into a poweramp?

My only experience with separates was when I used to own a Dynaco PAS3 preamp and it had a volume control. I then fed this Dynaco PAS3 preamp into "two" Dynaco ST-70 poweramps. The ST-70 poweramps did not have volume controls.


Quote:
The issue that gives most folks building something like this is hum caused by the parts and wires layout. A poor layout or cruddy build will result in a non-usable phono preamp. I would suggest that you wander back though this thread (huge yes I know) and notice the things that have gone well as those that didn't for various builders.

Question #2
Bruce, do you know of anyone who has created layout-drawings for the Groovewatt RIAA phono preamp? Forgive me for stating the obvious but as you already know, there is an 'order' to the construction process and I am not that experienced enough to build this phono preamp using only schematics. Thank you for understanding.


Quote:
I consider the project as an above average but not expert level for skill. When done properly the preamp is quite excellent and rivals many costing big dollars.

Thank you Bruce. Looking seriously into building this Groovewatt RIAA phono preamp.

Quote:
Since I can have anything I want......I use a pair of them in my system exclusively.

Question #3
Please clarify. Are you saying you take the left and right channels of your turntable and send each side (left and right) into two separate string of mono components? Example: left channel of the turntable into 'one' Groovewatt RIAA Phono Preamp into 'one' standard line-level preamp (with or without volume control) and then into 'one' poweramp (with or without volume control)? Then the same procedure with the right channel? Thus, in total, your system would have:

-One turntable
-Two Groovewatt RIAA phono preamps
-Two line-level preamps (with or without volume control)
-Two poweramps(with or without volume control)

Is this correct for a system that utilizes two Groovewatt RIAA Phono Preamps?

Closing:

Apologies for the redundancy but I just need to understand. Its been a long time since I owned separate components.

Thank you Bruce for your time and patience.


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PostPosted: 24 Feb 2021, 14:20 
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Joined: 04 Jun 2008, 20:59
Posts: 4327
Location: Arizona, USA
Hi, years ago many amplifiers and separate preamplifiers (that were designed to send signals to power amplifiers) had built in phono preamplifiers. Now most don't. The Dynacos you had were of that vintage. Since most no longer have the built in phono preamp it is necessary to provide that capability externally. The Groovewatt is such a device. It takes the very small signal from a cartridge and both amplifies and equalizes it so that the result is suitable for feeding into the AUX or LINE Inputs of a typical current device. That could be a home theater amplifier, a stand alone amplifier with volume and tone controls or a set of separate components like what you used before. BTW the PAS3 as I recall has a phono preamp built in. If you are still using it then the Groove watt would go into an AUX or LINE IN connection and not the existing phono input.

I don't know of anyone that has made PCBs for the preamp. You might ask on this site. Probably someone has.

The answer to #3 is that I have 6 turntables, 2 of which are connected at all times to my system. One preamp to each of the ones connected to the system. Thus two active turntables and two preamps. Yes I could switch the turntables between a single preamp, but I prefer not to do that. The Groovewatt is a stereo device.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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PostPosted: 24 Feb 2021, 17:47 
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Joined: 08 Feb 2021, 20:38
Posts: 8
gofar99 wrote:
Hi, years ago many amplifiers and separate preamplifiers (that were designed to send signals to power amplifiers) had built in phono preamplifiers. Now most don't. The Dynacos you had were of that vintage.

Interesting, thank you.

gofar99 wrote:
Since most no longer have the built in phono preamp it is necessary to provide that capability externally. The Groovewatt is such a device. It takes the very small signal from a cartridge and both amplifies and equalizes it so that the result is suitable for feeding into the AUX or LINE Inputs of a typical current device. That could be a home theater amplifier, a stand alone amplifier with volume and tone controls or a set of separate components like what you used before.

Still confused on this. My goal is to find project-plans (on this website) for a tube preamp and a low wattage tube poweramp (max 8 watts) for use in playing vinyl records on my Thorens turntable. In my previous post I gave the specs of my moving-magnet Ortofone Super OM 10 phono cartridge.
Question #1 please:
What components do I need to build besides the Groovewatt RIAA phono preamp and tube poweramp? Do I need to also build a separate tube line-level preamp? If so, then the signal path out of the turntable would go into the:
1) Groovewatt RIAA phono preamp
2) then into the input of the line level tube preamp
3) then into the input of the tube poweramp or if using your monoblock Push-Pull EL84 (6BQ5) valve amplifiers, I'd go left channel into one monoblock and right channel into another monoblock.

Is this correct? Would this be a complete tube stereo system for vinyl playback?

gofar99 wrote:
BTW the PAS3 as I recall has a phono preamp built in. If you are still using it then the Groove watt would go into an AUX or LINE IN connection and not the existing phono input.

Thank you, I did read that my Dynaco PAS3 preamp did -in fact- have a phono preamp built inside. I believe two tubes were for the phono preamp and two tubes for the line level preamp (all in one chassis). Unfortunately, I no longer own this Dynaco PAS3 preamp.

gofar99 wrote:
I don't know of anyone that has made PCBs for the preamp. You might ask on this site. Probably someone has.

Question #2 please:
My apologies, perhaps I was not clear. I meant to say, has anyone created Layout-drawings (not printed circuit boards - PCB's) of the Groovewatt RIAA phono preamp (besides the schematics and photos)? Layout-drawings are a lot easier for me to actually layout the parts and know where to install them. I can read schematics but it would be great if there were a parts listing and layout-drawings as well. Below are a couple of "styles" of layout-drawings for a guitar tube amp. Of course they can be simple or graphically stunning. Yes, I will continue to search this thread for layout-drawings but so far I have not located any. Thank you Bruce.

Image
Example: tube guitar amp layout-drawing

Image
Example: tube guitar amp layout-drawing

gofar99 wrote:
The answer to #3 is that I have 6 turntables, 2 of which are connected at all times to my system. One preamp to each of the ones connected to the system. Thus two active turntables and two preamps. Yes I could switch the turntables between a single preamp, but I prefer not to do that. The Groovewatt is a stereo device.

Question #3 please:
Ok, the Groovewatt is a stereo phono preamp. Do I also need a separate dedicated line-level stereo tube preamp as well?

Question #4 please:
I guess what I am asking is, can you please recommend all the diy component project-plans I would need to build a complete (separate units) stereo tube hifi system that is only intended to playback vinyl?

Thank you for designing this Groovewatt RIAA phono preamp Bruce. Appreciate your time.


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PostPosted: 25 Feb 2021, 00:50 
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Joined: 09 Oct 2012, 19:43
Posts: 376
Location: Vancouver Canada
Dam I just cringe every time I see a power switch in the neutral return loop instead of the line
side after the fuse. Ya I have heard lots of reasons why but dam. A device that, ""when switched
off"", leaves every component in it still connected to the live side of the line just looking for a
ground return is just the stupidest thing I have seen in all my years of being in this industry.

OK then. Thank you gentlemen, I feel much better now. Needed the rant.


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PostPosted: 25 Feb 2021, 17:04 
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Joined: 13 Jan 2018, 21:33
Posts: 395
Location: australia
In my case the output of my turntable (td160) enters a solid state phono stage (I hope to assemble a tube phono stage in future-Bruce’s Groovewatt looks great but a little concerned about of the skill level required to make a quiet stage...). The output of that plugs into my 300b amp with integrated preamp and driver (both 6sn7 triodes). I haven’t measured it but the level from the phono stage is sufficient to drive the 300b quite loud if need be.

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John


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PostPosted: 25 Feb 2021, 19:11 
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Joined: 08 Feb 2021, 20:38
Posts: 8
Woodo wrote:
In my case the output of my turntable (td160) enters a solid state phono stage (I hope to assemble a tube phono stage in future-Bruce’s Groovewatt looks great but a little concerned about of the skill level required to make a quiet stage...). The output of that plugs into my 300b amp with integrated preamp and driver (both 6sn7 triodes). I haven’t measured it but the level from the phono stage is sufficient to drive the 300b quite loud if need be.

Woodo, thank you for that ordered component chain hookup. Nice turntable! Is the amp you are referencing the BoyuuRange A50 MKIII 300B HiFi Intergrated Tube Amplifier Single-end Class A with Tube Cage?

https://www.amazon.com/BoyuuRange-MKIII-Intergrated-Amplifier-Single-end/dp/B0896YXRSM


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PostPosted: 26 Feb 2021, 01:16 
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Joined: 13 Jan 2018, 21:33
Posts: 395
Location: australia
I started off with an eBay pcb as follows https://www.ebay.com.au/itm/133096328873 and populated with provided components. Most of the components looked reasonable quality but who’s to know. I bought the Hammond chassis from and other hardware from mouser that serves our region, probably Hong Kong and the choke and transformers from edcor in the US. I was happy with the set up although the guitar tech I asked to look over it said biasing could be improved. Some time later after reading the thread on the 300b set (viewtopic.php?f=9&t=2699 ) the mono block circuit on p33 interested me so I modified the amp close to that circuit but re-using the transformers I already had on hand from my previous effort. It’s used about 1-2 hrs most days. Not sure how long the tubes will last but must have several hundred hours mileage so far.

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John


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