Upgrade questions?

[Mucker]

Hi all,

I don't want to get too carried away with the final updates I do to my Crack, but I am curious if there are any further gains to be made or if I should just leave it as is. I have combed the forums for ideas and have narrowed my questions.

1. I am thinking of trying a 12HB7A tube and understand I need resistors of about 130 ohm in the R1 positions on SB. Would also changing the transistors to MJE5731A be necessary other than reducing the temperature of the transistors? I am using a Chatham 5998 with TS 6SN7TB currently and it sounds excellent with Beyerdynamic DT-1990 Pro (250 ohm).

2. At 50% volume on Alps 100K pot I start to hear hiss which increases with knob increase, but no hum even to 100% volume, just hiss. I rarely go past 60% volume. Would adding the Cree diodes and choke help anything here? I usually use the Crack with vinyl where the noise floor is obviously magnitudes higher.

3. I might be tempted to try a stepped attenuator. Had my eye on the one linked below.  Will it work OK?

https://www.ebay.com/itm/323114836363?hash=item4b3b25218b:g:SlMAAOSwH1damzY6

I tried a DACT type attenuator in a Little Dot MK3 and I thought it improved it.

Overall, I am very happy with the Crack + SB, but because the cost of these upgrades is relatively inexpensive, was wondering or not if it would be just a waste of money to proceed?

Or do I just put the money toward a "S POINT 3 POINT 0 POINT X" to drive my Denon AH-D5000, Grados, and HE6se?

Thanks for listening ...

Greg

[Paul Birkeland]

If you short the inputs to the amp, do you get the hiss when turning up the pot that high?  Are you doing this with a source connected? (Just pause the music so you don't hurt your ears) 

Hiss with nothing plugged into the RCA jacks is not something I would worry about. 

You may find that the S3X is preferable on your DT-1990s as well.  The S3X amp is a great little amp, but not as tweakable as the Crack and it doesn't have anywhere near the tube rolling options. 

If you already have a fancy Alps Blue pot, I would just keep using that. 

[Mucker]

Awe great feedback Paul and quick too!

I just tried it and with the source connected is when the increased hissing occurs between 50 and 100, no buzzing at all. With the RCA's pulled out, the hiss nearly all but disappears, but I get increasing buzzing from 60 to 100. Guessing the tubes?

That's really good news about the DT-1990 and S3X; I wasn't thinking about that at all, but more thinking I need something to push the other cans I mentioned before. I really love these DT-1990's (more than HD-800 and T1 that I am getting rid of)

That moves my purchasing decision up (now it will happen soon). I was thinking I wanted a Crackatwoa, but the Crack is awfully good and I'm not sure the gain would be worth the cost, especially since I want to drive those other phones optimally. Also, good report on the pot. I am very happy with the Alps and have them in a few other amps.

I believe, I will just stop where I'm at with Crack and proceed directly to S3X. Can't thank you enough for the feedback!

[Paul Birkeland]

You might be getting some noise from your source.  You can try shorting the input RCA jacks with clip leads or some short pieces of bare wire wrapped tightly around each jack, then see what the noise floor is like then.  You'll probably find that there's nothing left at that point.

[Mucker]

OK, thank you. I just shorted the RCA's and the amp is silent 0-100.

Additionally, I just hooked up my battery powered Onkyo DAP to the Crack and it is silent from 0 - 100, so I believe you are spot on about the source Paul.

I've been using a Technics SL-1200GR turntable (newest model with built in linear power supply) that feeds a Vista Audio Phono 1 preamp which feeds the Crack. The Vista has a 2 prong wall-wart with 15V AC out. It works well with my older SL-1200 Mk2 that has an internal transformer for power, however, I had to stop using the it with the Crack because of the noise (both hum and buzz). I tried many things to solve it considering grounding but all attempts have failed and I've given up on making it work. The Vista is a very nice, transparent, and expensive (to me) piece of gear. Thankfully it works great with my other tables and amps.

I now use a Parks Puffin phono preamp that feeds the Crack. It is much better as far as noise is concerned. It is a 12V DC powered unit. The original post of this thread concerning the noise was using this setup.

Another question, would moving to a Bottlehead phono preamp improve my noise issues, not only with the Crack? And how does it pair as far as noise is concerned with the S3X? I obviously want the lowest noise from turntable to phono preamp to headphone amp. Buying a Bottlehead preamp wasn't on my radar but if the noise issues are diminished greatly it may be something I'd seriously consider.

Thanks ....

[Paul Birkeland]

If you play a record on your turntable with your Crack set at those volume levels, how loud is it?

[Toobuzz]

Hi! Just curious, what are you using as a shroud for the 6SN7 adapter?

[Mucker]

If you play a record on your turntable with your Crack set at those volume levels, how loud is it?

I can't go past 60% on my dial or it gets uncomfortable. (250 ohm Beyers). I use a Audio Technica VM740ML MM cartridge with 4.0 mV output into the Puffin. It is set at 47Kohm and 40dB output.

[Mucker]

Hi! Just curious, what are you using as a shroud for the 6SN7 adapter?

Hi Toobuzz,

Don't laugh too hard. It's actually just a cut-to-fit end of a sink drain pipe from home depot that I had laying around. Prob $1 when I bought it. BUT, it works well to keep my ham fist out of there and it looks like it plays the part just fine so happy with it. It obviously just slides on and off easily for quick change of tubes. "Gravity Mount" as Bottlehead says. I used a small round file to carve out the plastic to go over the socket mounting bolt heads and stay flush with the amp plate. It kind of semi-locks in place and doesn't rotate when installed.

[Paul Birkeland]

I can't go past 60% on my dial or it gets uncomfortable. (250 ohm Beyers). I use a Audio Technica VM740ML MM cartridge with 4.0 mV output into the Puffin. It is set at 47Kohm and 40dB output.

Yeah, this is all sounding pretty normal and some hiss above where your listening level would be considered comfortable isn't really a problem that needs to be addressed. 

[Mucker]

Yeah, this is all sounding pretty normal and some hiss above where your listening level would be considered comfortable isn't really a problem that needs to be addressed.

OK Paul, thank you! Once I drop the needle, I am dominated by master tape noise. And everything does sound excellent with a nice black background (relative to vinyl that is). No hum or buzz @ my normal listening level which is about 50%. I just wanted to make sure I wasn't adding any fixable noise to playback. Appreciate your time.

Greg