Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: moonbird on June 17, 2011, 07:43:39 pm
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Hello Tubenit -
I would like to explore how suitable a PP 6V6 (5Y3) PA would be as a platform for a CBS+V+VVR. I have one of these guys and it has been gathering dust - time to use it for something. Please see attached a photo of the chassis and front panel and a fairly hard to read schematic.
Got many questions --
1. As best I can tell from the schematic the PT supplies 340V to the plate - isn't that kinda low for the CBS??? Could I use a different recto tube or even go SS to get the voltage I need? I will try to get some measurements with 120V+ AC ASAP.
2. I am figuring to convert the two octal mic transformer sockets to novals using your sheet metal trick. However, I am unsure what to put where. Since there is a shortage of knob space on the front - my thought was to put the reverb and vibrato on the "back row" with small control knobs on the back. With all the funking old mic in and speaker out sockets on the back (plus adding a IEC) I figure the back panel is a major chop job that will require almost a completely new panel "patch" so I have lots of flexibility. To avoid crossing wires with the preamp - would you recommend maybe a separate reverb - vib "board" or even PTP area. I don't have a problem with point to point at all there -- but any layout suggestions you might have would be great!
3. I figure I will have the guitar input come in from the side of the chassis to make it a straight shot to the first noval socket on the front row. I would really like to do the double pentode input thing as well (would have to punch a hole for the 7-pin socket) -- what do you think would be the beat place? I have a small 6V toroidal that I could sneak in somewhere to help out with more filament juice.
Well .... that's a start -- feel free to offer anything you can think of as well. Thanks very much!!
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Can you post a schematic of the whole shootin box including the verb and trem concept? (That way we can decide faster what to tell you.)
The 5G9 (bias-vary) tremolo is real groovy for fixed bias 6V6s.
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You're talking about this amp?
http://www.el34world.com/Forum/index.php?topic=6368.0 (http://www.el34world.com/Forum/index.php?topic=6368.0)
Here is the schematic without the VVR. This was built inside a pretty big chassis. I think it's going to be a real challenge to fit it inside the Dukane IF you want vibrato, reverb and the VVR.
You could lose the 6Au6 and use a 12AX7 for the vibrato which will work great with 6V6's.
With respect, Tubenit
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Yes Tubenit -- that is the one.
Well - I also have a couple of the larger Dukane 1U460 (5881) chassis and trannies. Was going to use one for a BluesMeister. I could use the other for the CSR++. In your opinion is there enough difference between the BluesMeister and the CSR tone wise to justify building both (probably a dumb question).
The larger dukanes have an L=shapped layout - should I break up the turret board into two?
What could I build in the smaller Dukane from this forum? Would like to try one of the 6bm8-based amps. Which one would be different than the BM and CSR in tone and feel.
So are you recommending against the 6au6 vibrato?? I am a real vibrato-holick and I have MANY 6au6s :icon_biggrin:.
Thank you much!!
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What is a CSR?
I can't answer the turret board question because I'd need to see a photo of the inside of the chassis.
You can build a HoSo56 with 6V6's. Or build a Texas Raptor. Make a passive effects loop and insert a delay or reverb pedal. Pretty simple design.
No, I am not necessarily recommending the 6AU6 over the 12AX7. I had a Dano amp that had the 6AU6 and it was the sweetest vibrato I heard and I liked it better than my VibroChamp or Princeton Reverb (that I used to own).
with respect, Tubenit
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Sorry -- waddah putz :BangHead: I meant CBR (caro blues rocket). Is there enough difference in sound between the CBR and the BluesMeister to have both.
Just remembered I have a Bogen CHA-33 too. Maybe that would be a better candidate for one of these amps --
Will get some shots of the larger Dukane tomorrow and post - told the fam I want to spend the whole day working in my shop <grin>. thx kindly for the reply.
Looked at the Raptor - might give it a try. thx again.
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Is there enough difference in sound between the CBR and the BluesMeister to have both.
There is a pretty significant difference in their tone.
With respect, Tubenit
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I really like that piece of iron !
Kagliostro
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Well -
I have decided to stick with the Dukane 1A385 chassis for now and build Tubenit's 5879 Blues Amp as described here:
http://www.el34world.com/Forum/index.php?topic=9049.0 (http://www.el34world.com/Forum/index.php?topic=9049.0)
As I was researching the HoSo56 amp, I found a very interesting thread that presented some very cool alternatives that might be applied to the HoSo56 amps. That thread is here:
http://www.el34world.com/Forum/index.php?topic=6646.0 (http://www.el34world.com/Forum/index.php?topic=6646.0)
In particular, I am interested in the following switching:
- pentode direct to pi (ac15)
- pentode to gain/cf to pi (soho)
TubeNit -- what would be the best way to do this? Could a relay be used for the switch? How do you think it would sound with the 6V6s (from your experience - speculation welcome :icon_biggrin:)?
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I would not bother with the "sort of AC15" preamp. Very one dimensional and after you hear the HoSo56 preamp, I have a category that you might not ever use the AC15 preamp?
Look at DaGeezer's dual channel HoSo56 idea in the SCH file. He has really refined that amp and been tweaking it for a long time now. I have found every idea that I stole from Geezer has been excellent! Hope you'll check it out.
I think the 6V6's sound good with the HoSo56 typology.
With respect, Tubenit
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Ok -- I will - I trust your experience. So you are advocating taking the latest HoSo56 preamp and putting your 6v6 power section and reverb on it -- is that correct? thx again.
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I'd work with this latest version of Geezer's HoSo56 but would use 6V6's instead of EL84's.
http://www.el34world.com/Forum/index.php?board=12.0 (http://www.el34world.com/Forum/index.php?board=12.0)
With respect, Tubenit
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Tubenit - I think maybe you pasted the wrong link -- try it and see if that is what you intended (returns to the top of the forum seemingly). Thx much for your time.)
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http://www.el34world.com/Forum/index.php?topic=10999.0 (http://www.el34world.com/Forum/index.php?topic=10999.0)
Sorry about that. Try this one.
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Thats the one I thought was the latest. thx much.