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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #6611  
Old 10-07-2021, 09:35 AM
rmlowz rmlowz is offline
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I was wondering if anyone has tried 6BG6 to 6L6 adapters with a Inspire amplifier?

Thanks
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  #6612  
Old 10-07-2021, 10:00 AM
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Originally Posted by Isaacc7 View Post
Hey Straitwire, how difficult would it be to rewire the input tube of the KT88 firebottle to 12v? Or better yet, to put in a switch to choose between 6v and 12v? Is it the kind of thing that a competent tech could do?

I've emailed Dennis about the possibility of buying a new amp with that capability but have not heard anything back. I assume he is too busy with new toys to worry about redesigning a boring part of an existing amp lol.


I don't remember what the KT88 uses for driver tubes, but if you're looking to switch from say a 6SL7 to a 12SL7, it's not really possible without changing or adding a new filament transformer. Tubes like a 12AX7 or 12AU7 can be used with a 6V filament transformer because of an extra connection in the internal filament wiring that can then be used to wire the tube socket in either series or parallel, allowing the use of either a 6V or 12V filament transformer. However, 12SL7s don't have this extra connection, so the corresponding flexibility is missing.

I can't exactly speak for Dennis, but his time is so limited trying to keep up with demand on existing orders and models, that I doubt he will be interested in messing with a one off like what you are proposing. Someone else might be able to do this 6V/12V switch for you, but it would require not only adding at least one (if not two) extra filament transformer(s), but also some additionally switching circuitry...
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  #6613  
Old 10-07-2021, 09:54 PM
Isaacc7 Isaacc7 is online now
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Originally Posted by Analog Addict View Post
I don't remember what the KT88 uses for driver tubes, but if you're looking to switch from say a 6SL7 to a 12SL7, it's not really possible without changing or adding a new filament transformer. Tubes like a 12AX7 or 12AU7 can be used with a 6V filament transformer because of an extra connection in the internal filament wiring that can then be used to wire the tube socket in either series or parallel, allowing the use of either a 6V or 12V filament transformer. However, 12SL7s don't have this extra connection, so the corresponding flexibility is missing.

I can't exactly speak for Dennis, but his time is so limited trying to keep up with demand on existing orders and models, that I doubt he will be interested in messing with a one off like what you are proposing. Someone else might be able to do this 6V/12V switch for you, but it would require not only adding at least one (if not two) extra filament transformer(s), but also some additionally switching circuitry...
I didn't really expect Dennis to want to do it but was hoping someone would talk about the complexity involved. So thank you!

The KT88 uses the 6bx7/6sn7/6sl7 so it sounds like it would need a new filament transformer. I assume that the filaments of both the input and output tubes are run off of a single tap on the power transformer. Would changing just the input tube mess up the heaters on the output tubes? I've asked a few local repair places but haven't heard back yet. Sounds like this may not really make much sense money-wise.
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  #6614  
Old 10-08-2021, 11:38 AM
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Quote:
Originally Posted by Isaacc7 View Post
I didn't really expect Dennis to want to do it but was hoping someone would talk about the complexity involved. So thank you!

The KT88 uses the 6bx7/6sn7/6sl7 so it sounds like it would need a new filament transformer. I assume that the filaments of both the input and output tubes are run off of a single tap on the power transformer. Would changing just the input tube mess up the heaters on the output tubes? I've asked a few local repair places but haven't heard back yet. Sounds like this may not really make much sense money-wise.
Well, it all depends on how it was wired. The only way it would work is to make sure the filament supplies for the drivers and outputs are completely separate, rather than connected as in many amps where all the tubes use the same filament voltage.

A rewire would be required, but that is pretty trivial. Then a new filament transformer or two would need to be installed, along with a switching set up. It could be done, but some of this also depends on how much room there is under the hood, and Dennis usually packs things in tight...
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  #6615  
Old 10-08-2021, 01:08 PM
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A simple/crude illustration of the rewiring...

Untitled by analog addict, on Flickr
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  #6616  
Old 10-08-2021, 04:32 PM
Isaacc7 Isaacc7 is online now
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I'm talking to a tech in the area. He essentially said exactly what you said. It can be done as long as there is enough space. He did say that it would be a pretty small transformer since it doesn't require much current. I'll send some pictures to him this weekend and see what he says.
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  #6617  
Old 10-09-2021, 12:16 PM
Bentan Bentan is offline
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I’ve had the Firebottle for a couple of months now and love the match with my Audionote ANEs. I’m trying to get a hold of Dennis now for 5 months to have a CJ5 (or is there a newer one?) preamp made or maybe the phono as well if that’s for sale but he hasn’t replied my emails. Anyone knows how else I can reach him? Thanks in advance.
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  #6618  
Old 10-09-2021, 12:29 PM
DRHamp DRHamp is offline
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@Bentan - you can watch EBay - He has the LP-2030 (newest pre/linestage) there every other week or so.

Last edited by DRHamp; 10-09-2021 at 01:09 PM.
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  #6619  
Old 10-09-2021, 01:08 PM
bearcity bearcity is offline
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Originally Posted by DRHamp View Post
@Betan - you can watch EBay - He has the LP-2030 (newest pre/linestage) there every other week or so.


+1

Dennis has told me the 2030 beats the CJ 5 hands down. Still trying to have our schedules allow a visit so I can pick up one and compare.
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  #6620  
Old 10-09-2021, 09:50 PM
Bombadil Bombadil is offline
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So Dennis is busy.

But I would be surprised if he is experiencing a slow down due to the unavailability of computer chips.
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