From what I have read it is a good practise to not use just one brand of resistor in your project. The result could start to sound too much like that resistor.
A hint that a friend sent me about Alen-Bradley carbon resistors: bake them at 180 degrees for eight hours and then shallac them once they are cool. This should reduce their noise and help them hold their value. |
I have been using Allen Bradley 2watt 1k for the Cathode resistor. (R6 on the Joe Roberts 91a Schematic).
A friend lent me 2 watt AN tantalums. Wow the detail is addictive..really natural, warm and beautiful. The only problem in my particular system was along with the detail came too much emphasis in high frequencies. A certain crispness that seemed unnatural. Again, it may be related to my particular amp, etc. I am in contact with Michael at Percy for resistor suggestions. May try the TX2575 based on all the good reports in this thread. |
Salectric,
I put the A-B's back in after trying the tants. I dont understand it either but the high frequency emphasis was undeniable. That is why I mentioned in my post that it could be something peculiar in my system. For instance, I pulled the capacitor that is bypassing this resistor completely out of the circuit. I also took the grid cap off of the 6C6 driver tube and have 22 gauge silver wire directly in contact with the grid. Not sure if any of these things were interfering with the sound of the Tants, but I can't be sure. I am awaiting a response from Percy Audio as to another resistor recommendation. |
And perhaps I have been over compensating for the warm A-B's by doing things like removing the grid caps. I will check with the guy who lent me the Tants to see how old they are. I do know they were fully broken in since he had been using them in his home brew 2A3 amp. |
The AN Tants I borrowed are the previous version of the AN type; Audio Note is now making a newer version with non-magnetic copper end caps.
I am going to get the TX2575 and be mindful that if I hear too much hi end emphasis there may be something else in my amp/system to blame |
Prcinka, Cant find much info on how the Amtrans AMRG sound. Can you shed some light? |
The Vishays arrived and I installed them in the 6C6 cathode position. Will report back in a week after some burn in time |
The Vishays arrived and I installed them in the 6C6 cathode position. Will report back in a week after some burn in time |
After 60 hours the the Vishay TX2575 are starting to sound really nice. That crispness that the AN Tants had in the hi frequenies that was bothering me is not present in the Vishays. The high end seems very natural. So far there is richness, natural detail and some soundstage depth. I do notice paticularly how natural they sound. Very satisfying in that regard. They need to develope more front to back depth for me to be completely happy.
Before 60 hours, they sounded sterile and intruments didnt have their individual tonal characteristics. The soundstage lacked the depth and richness of both the AN Tants and A-Bs. I was not loving the sound at all. Sound stage was flat and uninteresting.
So far so good. More in a few days. |
Every time I have changed the 6C6 cathode resistor I have heard a sonic difference and it is not subtle. This is a single ended amp with a low parts count. When I pulled the bypass capacitor that made made a dramatic difference in sound as well as the gain of the amp. Response34, I will look into the possibility of replacing the 91k A-B's with 91k/12watt Mills resistors. This is the 6C6 plate resistor and audio signal is present here. For now I am happy with the overall sound of the amp.
After 100 hours the TX2757 are here to stay. They let the music pass thru with richness, clarity and depth. No hi end emphasis or etch. Each instrument has its own accurate color and detail but not at the expense of the overall musical message. Front to back depth is very pleasing and I am not missing the A-B's or the AN Tantalums. |
After a month with the TX2757 in the 6C6 cathode position, including bypassing them with Black Gate Caps I decided to pull these resistors. They did not provide the richness and room filling sound that the A-B's and the older AN Tantalum did. A few weeks ago I got two of the most recent production 1k An Tants from the Hi Fi Collective.
These new Tants are more closely akin to the A-B's than to the TX2575's. They are not as sonically accurate or pure as the TX's. But they do fill the room with rich satisfying music like the A-Bs but with more detail and without the extra noise or warmth or whatever it is with the A-B carbon comps. Still running the amp without the 6C6 bypass cap. |
Bigkidz,
That rotary switch is great idea and thus provides instant results. Nice! I will have to try the Shinkoh's when I begin to "voice" my newly built phono pre.
It's good to keep in mind that I/all of us have different ears and listening priorities. I am voicing my amp to work with my sources and speakers in my room without a preamp.
It must be very difficult for the professional builder to voice an amp or preamp with so many variables to confront. I have been voicing my amp slowly for about a year. |
Salectric,
I put the Tants on my cap burner for two weeks before installing into the amp circuit but even after that, their sound has been changing over the past four days. Last night they were starting to sound luxurious and rich but still maintaining detail and without that crispy upper mid/hi frequency etch of the older Tants.
More later. |
I have a direct comparison of PRP resistors to Shinkoh Tantalums. This past weekend I replaced 8 PRP resistors (4 per channel)with Shinkoh Tants. Now my Audio Note Home brew M3 phono circuit has 6 tants per channel. 2 of those are Audio Note tants. As soon as I turned on the pre and started playing music there was an immediate and dramatic improvement in the quality of the sound. So much smoother and beautiful sounding. The increase in musicality was compelling. Of coarse the Tants are not even close to being broken in and I am noticing a bit of emphasis on the leading edge of instruments that may or may not go away. Now the circuit has a nice mix of Allen-Bradley, Tants and 2 PRP. I have the option of adding even more A-Bs if I want to totally get rid of the PRPs.
In my opinion if you are going to use PRP use very sparingly or use them to get your project up and running and plan to replace. Until this weekend, I had no idea what true potential the AN Phono pre and Rega TT was capable. |
Bigkidz,
Thank you for the update on Shinko resistors. I see Shinkoh Tantalum Resistors offered at Hifi collective. Are they the same as your Shinko resistors -Regards Jet |
