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Take a look at my new Blue Circle SBH Headphone and preamp


Frihed89
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I have some pictures here:

http://www.flickr.com/photos/[email protected]/sets/72157603216939944/

I ordered at RMAF2007 after a short audition. I currently have an SP MPX3 SE Slam, a MAD HD1, a McAlister Preamp/headphone amp (PL 12, I think). I don't think my hearing is good enough to really distinguish the important differences between the three, and I am also not sure I can put what I hear into words, but I will review the SBH after I get it broken in and used to it both as a headphone amp and a preamp. I have excessive gain with both my MPX3 and PL 12 preamp sections. The SBH will have lo and hi gain operation. It can also be operated as both a preamp and headphone amp simultaneously and there are seperate master volume controls for each, but common L-R channel gain controls.

It's hard for me to imagine a headamp that doesn't have tubes, but this one sounds really, really good.

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Nice system. I heard some of the larger Quicksilver monoblocks and theyb were very nice.

All the Quicksilver amps have the same basic sonic signature - smooth, well balanced. As you go up the ladder, the bass and dynamics improve, the treble is more open and extended and the amps are more transparent, but if you play fairly simple music, it really is hard for me to tell a minifrom a V-4. Of course. the more power the better the speakers. But the minis drive my LS3/5As effortlessly for $998

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Gilbert Yeung designs his amps and preamps with both discrete and opamp output stages. The SBH employs an opamp output stage. I guess that's one reason it doesn't cost more.

I didn't think about the circuit when i bought it. I had to listen to it for 5 minutes before I decided to buy it. Each time I came back to listen I discovered something new. It was exactly like the experience I had with Singlepower at RMAF the previous year, but $1200 less expensive (not including tube cost).

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You mean my preamp or power amp? In my preamp, I have some RCA 6SN7GTs clear glass early post WWII vintage. I was given these tubes. I tried a bunch of high-end WWII vintage 6SN7s and, like Peter said, they made abolsutely no difference whatsoever.

The tube suit in my preamp are: 2x 27GB5, 2x 6SN7, and a 12BQ6.

The power amp uses: 4x 24JE6/24LQ6, a 6AX4, and 4 x 6EA7/6EM7. I have never rolled the tubes. It sounds great as is.

Both units arrived with a number of construction/fabrication mistakes, indicative of poor planning, less than ideal inventories of parts and sloppy workmanship. I had a very hard time getting things in reliable working order. Too bad. Both units are very nice sounding for the price, but I suspect the average buyer would not be willing to put up with this. Because I live in Denmark, I really had no choice, but to fix the mistakes here or scrap them. I'm glad I fixed them.

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Both units arrived with a number of construction/fabrication mistakes, indicative of poor planning, less than ideal inventories of parts and sloppy workmanship. I had a very hard time getting things in reliable working order. Too bad. Both units are very nice sounding for the price, but I suspect the average buyer would not be willing to put up with this. Because I live in Denmark, I really had no choice, but to fix the mistakes here or scrap them. I'm glad I fixed them.
I know how that is. Luckily they sound great once the issues are worked out. :)

Too bad you went with the 6SN7, if you went with the 6CG7/6GU7 I would have some recommendations for you as I've tried out most of the tubes out there. Also, the 6GU7 is a lower gain tube which would help you a bit.

Not many choices with the 27GB5/PL600. Mine are from the Matsushita factory and sound great... I think there were only 2 or 3 makes of this tube in any case.

My amp has 6BQ7A/6BZ7 instead of the 12BQ6, and I use General Electric JAN tubes there. Haven't really tried anything else, but I'm happy with the sound. :)

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I know how that is. Luckily they sound great once the issues are worked out. :)

Too bad you went with the 6SN7, if you went with the 6CG7/6GU7 I would have some recommendations for you as I've tried out most of the tubes out there. Also, the 6GU7 is a lower gain tube which would help you a bit.

Not many choices with the 27GB5/PL600. Mine are from the Matsushita factory and sound great... I think there were only 2 or 3 makes of this tube in any case.

My amp has 6BQ7A/6BZ7 instead of the 12BQ6, and I use General Electric JAN tubes there. Haven't really tried anything else, but I'm happy with the sound. :)

Peter didn't really give me a choice and I didn't know enough to ask for different tubes. I wanted a neutral preamp. I got one. The head amp section isn't bad (now that the hearing my right ear has been restored), either. However, I have the same issue as I do with my MPX-3 Slam SE preamp - either too much gain or a crummy volume pot makes it hard to go past 7-8 o'clock. The PP130 (like the PP150 with different outputs) has very high gain. Peter should knock that down some.

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Well, you could always ask him if it would be safe to roll in some 6GU7's [i recommend the RCA 6GU7]. I seem to remember having a conversation with him at some point where he said that you could throw basically any tube in that spot on his circuit. The headphone section isn't bad? What are your complaints? If you are sick of that crappy pot that is in there, I highly recommend a Singlepower stepped attenuator. Made a huge difference in my amp. :)

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Well, you could always ask him if it would be safe to roll in some 6GU7's [i recommend the RCA 6GU7]. I seem to remember having a conversation with him at some point where he said that you could throw basically any tube in that spot on his circuit. The headphone section isn't bad? What are your complaints? If you are sick of that crappy pot that is in there, I highly recommend a Singlepower stepped attenuator. Made a huge difference in my amp. :)

Peter told me that this circuit is "immune" to tube rolling in the sense that it doesn't affect the sonics. Also does the 6GU7 have the same base as the 6SN7?

I didn't buy the preamp for its headphone capability as I already had 2 good tube headphone amps (MAD and SP), but what it is not so nice about it, is that when I plug in the headphones it attenuates the preamp signal and crushes the life out of it.

I did put a somewhat more expensive pot in there (2 of them in fact) and it didn't really improve the situation, so I think the real problem is excess gain, but I am not 100% sure. I am hesitant to add a decent attenuator because of the additional cost.

Here's what I had to do so far (actually most of the work was done either by a metal smith or an ET):

1. Change and properly ground the Vol and balance pots to the case in the preamp.

2. Replace and reposition a huge capacitor that was almost in contact with the preamp case.

3. Weld brackets on the inside of the power supply case so it could be better secured by case bolts.

4. Replace, redrill all case bolts and add a few to the power supply case.

5. Replace the rubber isolation-insulation matting in the power supply case under the 3 transformers with the correct rubber insulating material.

6. Replace all the transformer bolts so they could be secured to the bottom of the power supply case.

7. Replace and re-wire 4 power tube sockets in the main amplifier case.

8. Re-wire some caps in the main amplifier case and reposition them so they would not short on the case or other components.

9. Replace some wiring and insulate it with teflon for the same reason.

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Peter told me that this circuit is "immune" to tube rolling in the sense that it doesn't affect the sonics.
Yeah, but he's wrong. :)
Also does the 6GU7 have the same base as the 6SN7?
Not sure, Earl would probably know.
I didn't buy the preamp for its headphone capability as I already had 2 good tube headphone amps (MAD and SP), but what it is not so nice about it, is that when I plug in the headphones it attenuates the preamp signal and crushes the life out of it.
Attenuates the preamp signal? You are trying to use it as a preamp and a headphone amp at the same time? Why?
I did put a somewhat more expensive pot in there (2 of them in fact) and it didn't really improve the situation, so I think the real problem is excess gain, but I am not 100% sure. I am hesitant to add a decent attenuator because of the additional cost.
It could be the value of the pot as well. Peter had a 25K pot in mine originally. When I moved to the 50K Singlepower stepped attenuator the noise went way down.
Here's what I had to do so far (actually most of the work was done either by a metal smith or an ET):

1. Change and properly ground the Vol and balance pots to the case in the preamp.

2. Replace and reposition a huge capacitor that was almost in contact with the preamp case.

3. Weld brackets on the inside of the power supply case so it could be better secured by case bolts.

4. Replace, redrill all case bolts and add a few to the power supply case.

5. Replace the rubber isolation-insulation matting in the power supply case under the 3 transformers with the correct rubber insulating material.

6. Replace all the transformer bolts so they could be secured to the bottom of the power supply case.

7. Replace and re-wire 4 power tube sockets in the main amplifier case.

8. Re-wire some caps in the main amplifier case and reposition them so they would not short on the case or other components.

9. Replace some wiring and insulate it with teflon for the same reason.

Sounds like you've done some good work there. :)

My amp was 'missing' some resistors to ground on the 6CG7, which we put in. Could have caused biasing issues according to KG. One of the tube sockets was a little flakey, so we resoldered all the pins. We replaced the two terrible 'stepped attenuators' that Peter had in there with the 4-gang singlepower switch. I think that is basically it, other than the new wooden faceplate of course. The amp sounded pretty good right off the bat, though you had to wiggle the tube in that flakey socket to get some distortion to go away in one of the channels. There was also some grain/noise at higher volumes. After making these changes it has been rock solid, no noise, and the sonics have improved a fair bit.

At some point I still want to open her up again and do some work on the power supply. Peter uses a mass of stacked diodes rather than a simple bridge rectifier for some reason, and we should replace that to prevent meltdown. I'd love to do a complete rebuild, but just haven't had the time.

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Philodox. Thanks very much for the help/replies/update. I want to try out the new SS head/pre by Blue Circle before I put any more time or moeny into the PL-12.

Why both pre and head amp listening at the same time? I have a hearing problem and I listen to the head amp. My wife has perfect hearing. She likes the speakers. We listen together a lot.

Wow, you're the first person who has told me that they also had wobbley tube and "internals" problems. Very interesting. What's the story with this guy anyway? I can't figure him out.

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Why both pre and head amp listening at the same time? I have a hearing problem and I listen to the head amp. My wife has perfect hearing. She likes the speakers. We listen together a lot.
Oh, I see. I'm not completely sure, but I think that by hooking up the headphones while playing music through the power amp/speakers would really mess with some things since they are both using the same circuit. Kind of like when you plug two headphones into the same amp and the impedance gets chopped in half.
Wow, you're the first person who has told me that they also had wobbley tube and "internals" problems. Very interesting. What's the story with this guy anyway? I can't figure him out.
If you'd like to see pics of the internals, send me a PM. Kevin Gilmore posted them up on here at some point, but I'm not sure what thread they are in. It should make you feel better about the shape of yours, as I'm betting mine was worse. :D
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I'm not completely sure, but I think that by hooking up the headphones while playing music through the power amp/speakers would really mess with some things since they are both using the same circuit. Kind of like when you plug two headphones into the same amp and the impedance gets chopped in half.

I thought it was only poorly designed/weak amps that suffered from this problem? ???

On a related note, I listened to a Rudistor RPX100 today with a balanced and unbalanced L3000, balanced and unbalanced HD650 as well as a Qualia and a Koss A250. Never once did I detect any deterioration when plugging in another headphone while another was already in place. The owner of the Rudistor told me that Rudi did mention that the amp would have no trouble at all driving multiple cans at the same time.

Off-topic: The Qualia still sounds bright as heck out of an RPX100. Whoever claimed that it sounds its best out of that amp must've been smoking something.

More off-topic: The Rudistor power supply could use some better power filtering, since there was a noticeable constant-level hiss when a headphone was plugged in and no music playing. The owner told me that his house had a particularly noisy power grid (confirmed using a voltmeter). Still, IMHO a good amp should be impervious to such issues.

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I thought it was only poorly designed/weak amps that suffered from this problem? ???

On a related note, I listened to a Rudistor RPX100 today with a balanced and unbalanced L3000, balanced and unbalanced HD650 as well as a Qualia and a Koss A250. Never once did I detect any deterioration when plugging in another headphone while another was already in place. The owner of the Rudistor told me that Rudi did mention that the amp would have no trouble at all driving multiple cans at the same time.

Off-topic: The Qualia still sounds bright as heck out of an RPX100. Whoever claimed that it sounds its best out of that amp must've been smoking something.

More off-topic: The Rudistor power supply could use some better power filtering, since there was a noticeable constant-level hiss when a headphone was plugged in and no music playing. The owner told me that his house had a particularly noisy power grid (confirmed using a voltmeter). Still, IMHO a good amp should be impervious to such issues.

Rudistor makes mediocre amps... :(

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I thought it was only poorly designed/weak amps that suffered from this problem?
Huh? If the preamp and headphone amp are seperate circuits, ok, but any amp is going to behave differently when you plug multiple things into it.

For multiple headphones, it really depends on what headphones you are talking about. If you plug in two K340s, the impedance gets halved and in some cases they might even be easier to drive this way in terms of voltage. If you plug in two Grados, you are talking 16ohms... pretty low for some amps. Two headphones of different impedance are going to make volume level matching pretty tough.

Now, he is driving a pair of speaker amps and a hard to drive headphone at the same time... I think it goes without saying that this will put a lot of strain on the amp. It is not surprising that the headphones sound off in this situation.

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