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Groovewatt - tube RIAA phono preamp
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Author:  victorzwk [ 26 Apr 2018, 09:56 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

metaldog99 wrote:
Thanks for the information.

I am still debating on whether to go PCB or point-to-point. Single board PCB runs are a bit pricey if I factor in several revisions required.

Did you source your PCB's online? The cheapest I've found is PCBway. I've also looked at Bay Area Circuits as an option.

Thanks again,


I have etched the PCBs at home. Using the clothes iron toner transfer method. Cheap and easy.

Best Regards

Author:  metaldog99 [ 07 May 2018, 17:21 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

gofar99 wrote:
Hi, just out of curiosity...I see you are in Arizona. Mind if I ask where?

Good listening

Late to this, been laid up for a little bit.

I live in Mesa, but often travel to Sierra Vista on business at the Fort.

Author:  metaldog99 [ 07 May 2018, 17:32 ]
Post subject:  GrooveWatt Power Supply schematic question

I am preparing to wire up (point-to-point with perf board) the GrooveWatt, as I am waiting on my last order from Mouser. I have a question on the power supply schematic - I want to clarify that my understanding is correct:

1. The inputs to the Left and Right LR8K4 are electrically connected together, both being fed in parallel from the 245 vdc filtered output.
2. The outputs of the Left and Right LR8K4 are also electrically connected together - providing bias up the heater circuit.

I get 1.), but I don't quite get 2.)

Is my interpretation correct?



Author:  metaldog99 [ 07 May 2018, 17:45 ]
Post subject:  Layout comments?

So, I have abandoned the PC board plan for now, as I don't want to complicate things with something new (for me).

I have attempted to duplicate and adapt the layout provided by Bruce in his audioXpress article, and have come up with the layout below.

Is there anything inherently wrong with this layout? I have tried to minimize the signal path wire lengths, and to keep power runs away from signal or cross them at right angles when unavoidable.

I thought of using copper tape for the grounding runs - I have 1/4" copper shielding tape which is 1.6mils thick, 3M 1181

All opinions and comments are welcome.


Author:  metaldog99 [ 08 May 2018, 01:33 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Fixed some errors, and slight modifications.

Author:  metaldog99 [ 08 May 2018, 13:32 ]
Post subject:  Questions on using Hana EL with Groovewatt

I am settling on the Hana EL cartridge to use with my soon to be built Groovewatt - I have some questions:

1. Based upon comments here and in other threads, the Softone PLT-1 appears to be a great bang-for-the-buck SUT to use for the Hana EL. Superior to the Lundahl, and better value than the Silk at current exchange rates. Agree?
2. Using this combo (Hana EL + PLT-1), what value(s) for the load resistors on the Groovewatt input should be used? I am not sure of the translation of resistor value to load, so I don't know exactly how to calculate the value to achieve a nominal 400 ohm load (Hana EL recommended load).
3. I'd like to mount the PLT-1's within the chassis. What shielding do you recommend? I have leftover pieces of mu-metal from my Forewatt build that would be able to encase the PLT-1's, as well as other metal boxes of various sizes to work with.

Thanks in advance for any and all comments and suggestions.


Author:  gofar99 [ 08 May 2018, 17:15 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Hi, I have fiddled with the input resistance of the preamps when I used Lundahls. IMO it was not productive. Generally (does not include losses etc) the impedance that the cartridge sees will be the input of the preamp divided by the square of the turns ratio. With 12 to one the ratio the 47K divided by 144 very nicely works out to about 325 ohms. I would not mess with the input to the preamp for that cartridge. The value is close enough. I no longer do and the cartridges are just fine. If you must then about 57K is the value needed. IMO the 1:24 ratio would not be suitable as the input would go up to about 240K and you would likely increase the sensitivity to noise and lose any benefits of the higher ratio. All my LOMC cartridges (DynaVector Karat 23RS-MR, Benz Micro, AT 33PTG, AT F-7) work well with the 1:12 ratio and 47K input. A lot of shielding will certainly help. IMO it is something you can not get too much of. The transformers are (naturally) very sensitive to nearby electric radiation such as from power transformers. I used Mu metal plus a steel enclosure in one build. OK. But better with them in a separate steel box that is over a foot or two away. You can also turn the box for lowest hum. SUTs are a great way to step up the signal but can be difficult to keep quiet. BTW, I am not sure the EL is better overall than the EH which I have. It sound quite nice.

Good listening

Author:  metaldog99 [ 08 May 2018, 18:25 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Thanks for the advice.

I thought that you used the EL in your setup, per your other posts. Am I confused?

It is simple enough to house the SUT in a separate box - especially if it is less likely to be susceptible to noise and such.

My thoughts, based upon reading here, is that the Hana EL->PLT-1->Groovewatt->Forewatt would be a very nice combination if the builds were decent.

Author:  gofar99 [ 08 May 2018, 20:18 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

Hi, Has to be someone else. I only have the EH Hana. The EL according to folks over on forums seems to sound about the same.

Good listening

Author:  metaldog99 [ 08 May 2018, 21:00 ]
Post subject:  Re: Groovewatt - tube RIAA phono preamp

I was referring to this post

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