Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Topic started by: ee on August 01, 2015, 09:31:12 AM
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please suggest what to do or look for. I am trying to figure out how my stereomour that I built a few months ago sounds so different from the one I just built for my son. The sound difference is related to the volume. I have to turn mine up to around 12 o'clock or more to match the volume that his has when volume turned to 9 o'clock. Mine is not stock and his is except coupling and parafeed caps. Those cap values are the same though. Same tubes. I have gold point vol (checks out at 100k resistance) and gold point selector switch. Where they differ a lot is the power supply. Mine are Solens for the first two PS caps and third cap to B+ is a motor run/oil cap. My cathode bypass cap is 100uf film (Obbligato PSU). Voltage and resistance checks are very similar within a couple % of each other for the two amps throughout. Mine sounds a bit more fluid and organic but the fact that I barely have to turn the volume up on his has me perplexed. Of course I never built mine stock, but his is stock.
Not sure if i need to get under the active load PC board and check anything. Or what to check specifically if I do. Like the leds or transistors, voltages/resist at 9 pin socket. Thanks
eric
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My experience is different caps can affect the volume. I have a pair of amps that have 2 different of caps. One is noticeably louder than the other.
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Yeah I've done several cap experiments in my amp in PS, cathode bypass, coupling and parafeed. I could easily outfit another 3 amps in all those locations. And the difference was not like this. Yes some seemed a bit louder. It's just that the gain is so much greater between the two. On my amp the vol can be all the way without distortion and his amp will drive to distortion. I have also always had some static noise upon start up that decreased and was then intermittent every minute or so but not as loud after power up. I have resoldered all spots. Except under the PC board at 9 pin. And as far as trouble shooting the static issue I've read here and elsewhere that it could be the LEDs or maybe transistors. So even though the volt/resist measures maybe they are just not functioning properly. Dunno. I am also not sure at what point the gain would be addressed.
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Goldpoint vs stock pot is where the volume difference is, comparing both with the dial at say 12 o'clock is totally meaningless as they will have different response curves.
e.g. i plotted the values of a Goldpoint vs the regular eBay stepped attenuators here http://bottlehead.com/smf/index.php?topic=5316.msg56640#msg56640 (http://bottlehead.com/smf/index.php?topic=5316.msg56640#msg56640) as you can see the volume level on each switch position is different, add to that the fact audio pots have a logarithmic scale so the half way position isn't necessarily half volume.
First thing you need to do is set both amps so the actual output level is the same, then listen to see if you notice any sonic differences between them.
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Got it and I'll check them both. Thanks!
Eric
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Same tubes.
I would try the same tube set with both amps if you haven't already.
Not sure if i need to get under the active load PC board and check anything. Or what to check specifically if I do.
The voltage checks in the back of the manual would provide the information you would need to make this decision properly. Your post seems to indicate that these are not an issue, so I wouldn't go poking around under the board.
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Mcandmar- I am so grateful for your reply and insight.
Yes the stock pot go up quicker in the resistance than the goldpoint. I went ahead and changed the vol pot to stock. I was looking for the sonic benefit based on what I heard from my sons stock build. Sonics are much better in my setup. I have Fostex FE206En in large cabinets (name/design Vulcan) and now they sound more like what I expected. They have better dynamics, are more emotional, they pressurize the room better, more front half hall sounding than mid-hall. Overall the GP kinda numbed down my system. I don't mean this as a knock to them. I think the GP is a nice looking, solid, good tactile attenuator and would work for someone's system. Ive done cap changes and tube changes all pretty much meant to get to what I am now hearing. This is the best change I have made to date. I have heard comments how vol pots sound before but nothing too much and totally didn't appreciate the influence of that location. Bottlehead designs a great stock product and I'm glad to have the support and experience of Bottlehead community also. I'll playing with it again once the soldering iron heats up of course. Thanks!
Eric
Just saw PB's post as I was typing.
Yes same tubes 12at7 and 2a3.
I went under already and re-wet connections since it was the only place I had not done. It was gonna bug me if I didn't and still have the static. It's back together and checked out correct again.
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I do want to say I loved the GP for their clarity and background quietness non-etchy sound. For example I could hear bow movement on strings better than the stock. It's the impact that is better in my setup with the stock. If, and I am, looking for a replacement do you think its the metal film resistor part of the attenuator that seemed to dull the system? Other option to try would be the PEC it seems. I could try the DACT but it's metal film too.
Thanks
Eric
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To some observers (not me, I have avoided so far participating in a shootout!) surface mount metal films are inferior to leaded metal film resistors. Or possibly surface mount solder or soldering is different. Anyhow, individual leaded resistors are often rated above the surface mount resistor of the same construction. So ... which kind of Goldpoint attenuator did you use?
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I was going to suggest the PEC...John
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Goldpoint Mini-V (MV-2-100K per the email order) SMD yes and standard build from them.
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I ordered the PEC pot today to give it a spin. Thanks
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The thing i really dont like about the current Goldpoints is they are a series attenuator, if you are at 50% volume you have a dozen resistors daisy chained together in the signal path. In contrast a proper ladder style attenuator will only have two, and i believe the Bottlehead attenuators work the same way.
The best bang for your buck for a true ladder style is the "valab" units available on ebay, there are a few vendors that sell them populated with Dale resistors. Or keep an eye out for a vintage Goldpoint attenuators on eBay, but you will have to fight me for them :)
Or, bypass the inbuilt volume pot completely and buy a submissive kit.
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Thanks for the heads up on the Valab. I'll check it out. Still trying to read up on +/- of it all. I believe I would like to roll the dice on the ladder style after I get the PEC and see how it sounds, l/r balance. I've seen a ladder style on hificollective by glasshouse that also looks interesting.
The Submissive is an option too I think. Thanks for reminding me of the that option :)
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Ahh, I'll tell on myself. I went ahead and orderd the Valab an hour ago. Hard not to give it a try with a great price.