Bottlehead Forum
Bottlehead Kits => Mainline => Topic started by: Loquah on April 06, 2014, 02:03:47 PM
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I discovered yesterday that the 6C45P isn't a production tube any more - I had thought it was!?
During my discussion with the fellow audio enthusiast, he mentioned that there are some cryo treated gold-pin varieties out there that are getting harder to find so I'm wondering: is it worth tracking down a few sets of 6C45P to put on the shelf now or are there factories full of these things around the world?
Also, would "upgraded" versions of these tubes bring benefits to the Mainline or is it's design such that tubes don't have significant impact?
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Where did you hear that the 6C45Pi was out of production? I thought Sovtek (New Sensor) was still manufacturing new tubes?
I'm thinking of picking up a set of Electro-Harmonix and Sovtek's from here:
http://www.wooaudio.com/products/wa7fireflies.html
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A fellow enthusiast who owns the Woo WA7 and a set of their upgrade 6C45Pi-EHG cryo treated tubes. I think he's a reliable source...
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Hmm, too bad, I'll have to pick up a couple pairs to make sure I don't end up scrounging for some a couple years down the road.
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They are available as NOS Surplus Military tubes. I expect there are cases, or crates of them available.
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I hope so.
I don't plan to rush into modifying the circuit, but are there any other tubes that the Mainline would work with effectively with some minor alterations?
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New Sensor has made new 6C45's, but I don't believe they were particularly successful in their efforts.
For the time being, there aren't other triodes that will drop into the circuit, except perhaps with WE 437A.
The military surplus supply of 6C45's appears to be very significant. When they begin to dry up, the Chinese and Russians will put them back into production, and eventually get the bugs worked out.
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I ordered a pair of Electro Harmonix 6C45's. I'm planning to do a complete review of the Mainline. Will compare single ended vs. balanced operation, and I'll compare the Sovtek tubes vs. the EH tubes as well, all using HD800's. Now just to wait until my kit arrives... :D
The following site has some interesting things to say about the EH 6C45's, but they are doing the comparison in the WA7 fireflies:
http://www.audio360.org/amps-dacs_a0018_review_woo_audio_wa7_fireflies.php
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To properly make the 6C45PI, the grid wires need to be at least platinum plated wire, if not solid platinum.
In combination with this materials issue, the tube itself is very difficult to produce, and hence the EH's are out of production. One would hope that they are continuing research on other production methods to "get it right".
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I was able to pick up a well priced matched pair of Electro Harmonix gold pin 6C45Ps today and I'm wondering if they will should be expected to improve the Mainline's sound at all?
They're widely considered a better example of the 6C45P models, but knowing how tightly controlled the performance of the Mainline is, I'm wondering if they'll make much difference. It's really hard to A/B them so any differences I'm hearing might be pure bias.
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Would anybody happen to know how I could match tubes using the Mainline's circuits (I.e. try putting tubes one after another into the tube sockets and measure something when the amp is on)?? I'm hoping that there may be some way using a digital multimeter.
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Biasing instructions are in the manual.
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Biasing instructions are in the manual.
So does biasing essentially remove the need to have matched tubes?
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So does biasing essentially remove the need to have matched tubes?
The circuit design essentially removes the need to have matched tubes.
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Nice!
Am I correct then in thinking that if we change tubes we should redo the biasing?
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Yes and no.
If you go through biasing the amplifier to dial in the plate voltage, you will receive the maximum possible output power from the Mainline.
If you don't, you may not receive all the power that the amplifier has to offer.
Whether or not this matters depends upon many conditions, including the headphones being driven, how loudly you want to listen, etc.
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Yes and no.
If you go through biasing the amplifier to dial in the plate voltage, you will receive the maximum possible output power from the Mainline.
If you don't, you may not receive all the power that the amplifier has to offer.
Whether or not this matters depends upon many conditions, including the headphones being driven, how loudly you want to listen, etc.
In theory then could failing to bias for new tubes result in a tiny channel imbalance?
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No, more that if you had one channel perfectly biased, you'd see maximum output power. If the other channel wasn't properly biased, you'd see something less than that.
This would equate to different THD between channels at maximum power, with the asymmetrical clipping potentially reducing the gain a little bit in that channel. Again, this is only at maximum power.
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I understand. Thanks for the great explanation!
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In the event anyone is looking to pick up a couple spare pairs of 6c45pi tubes, this NIB 4 pack is the lowest price I've seen on ebay in a while ($15 per tube, including shipping). Several months ago, I managed to snag a couple of pairs from a US seller for only $10 per tube, but haven't seen anything this low since. Nixiestore also seems to be a pretty legit seller so I pulled the trigger on four more last night. Figured I'd share the link while a few lots are still available: http://www.ebay.com/itm/4-x-6S45P-E-6C45P-WE437-EC8020-NEW-TUBES-NIB-OTK-/390820796896?pt=Vintage_Electronics_R2&hash=item5afebc19e0
I've spent more hours than I'd care to admit hunting for a reasonable price on the electro-harmonix version. $100 through woo still feels excessive, although I gather that supply and demand suggest my feelings are in error heh.
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Thanks for the heads up Mike. I snagged a set for myself. Apparently they are Gold Grid wires. Paul indicated they needed to be platinum to be true 6C45pi tubes. I wonder what gold grids will sound like?
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Thanks for the heads up Mike. I snagged a set for myself. Apparently they are Gold Grid wires. Paul indicated they needed to be platinum to be true 6C45pi tubes. I wonder what gold grids will sound like?
Hmm, I wonder if they switched at some point. I wouldn't be concerned with any old production 6C45's.
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Hmm, they are starting to get more rare. I hope you guys have enough stock for your kits.
http://www.ehx.com/products/6c45pi-gold
My local retailer went to EHX to get a quote, but EHX would not sell them unless they are were part a bulk purchase of 50+ at $35-40ea Canadian after markup to retail, exchange and lets not forget tax. Apparently they buy that much about once every 6 months or so and would be willing to put my order in that way.
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Lots of them are $10-$12 (US) on ebay.