Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ed_Chambley on February 13, 2012, 01:55:36 pm
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Hey guys, I am planning to build a new project. I am going to use a chassis and cage. I have a couple of questions. I have read on the forum here where lots of people use Deluxe OT. Why? Also since I am going to put a chassis on a wooden 4" finger jointed box with a wood bottom and the chassis will have a metal cover for the bottom. This is hammond stuff. Is there any problem with having the reverb unit that close to the amp? I plan to hardwire the reverb in the amp, but plug it into the reverb unit itself. It will be a head. I would like an OT with 4,8,16 taps. A suggestion here would be helpful. Also, where can I get a nice reverb unit less than 16" long with 3 springs so a dwelll can be added.
This will be my first "out of the box" build so any suggestions are welcome. I have attached a layout, but I have also read of people building them with EL-84's. Is there much difference?
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The DR OT is bigger and probably has more bottom end. You can get a short (I think 9") 3 spring tank from AES. Many head units have the reverb tank mounted very close to the chassis. Bandmaster Reverb, Showman Reverb, old Sunns. Look at this reverb tank...
(http://home.comcast.net/~seluckey/amps/sunn/sunn_02.jpg)
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The DR OT is bigger and probably has more bottom end. You can get a short (I think 9") 3 spring tank from AES. Many head units have the reverb tank mounted very close to the chassis. Bandmaster Reverb, Showman Reverb, old Sunns. Look at this reverb tank...
(http://home.comcast.net/~seluckey/amps/sunn/sunn_02.jpg)
Cool Sunn amp. What ohm input and output? AES has quite a few. Any suggestion as to who's is the best. Accutronics, Mod. Is the bias style tremelo superior to the bug? Also, would the Deluxe OT preform better with 2, 12's cabinet. I am sort of hooked on Weber Alnico Silver and Blue 12's. They are $$$$$, but I have never heard a better sounding combination.
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The bias vary tremolo is cool but not superior to the roach,just different.a 2-12 cabinet would be awesome with a Princeton Reverb.
The Blue and Silver sound great too.
Just one question: if you want to put the circuit in a head,why not just make it a full-sized head?It's not very big as it is and the full-sized reverb tank will fit as well.
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10 ohm input, 2,575 ohm output, medium decay, type 8, 3 spring
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The bias vary tremolo is cool but not superior to the roach,just different.a 2-12 cabinet would be awesome with a Princeton Reverb.
The Blue and Silver sound great too.
Just one question: if you want to put the circuit in a head,why not just make it a full-sized head?It's not very big as it is and the full-sized reverb tank will fit as well.
I am actually going to use a hammond chassis 17 x 10 x 3 so a regular size reverb will probably work anyway. I just want to build a head which a cage top and router a edge of the box so the chassis will recess into it a little. I have a local high end wood supplier and I want to make something different. It will be a living room amp to fit in with an organ and Leslie. Just something different which will look as it fits with the furnishings in the living room. This is also why I am going with a princeton to have some good tones at lower volumes.
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I am looking at 2 Hammond PT's. One is for a Deluxe and one is for a Princeton. I have attached the spec sheet for both here. The Deluxe has a bias tap and 3 amp on 6.3 vac as well as 3 amp on 5 vac. It seems like everything else is the same. I am leaning on using the Deluxe as I think if I also use the deluxe OT, it will give me the option of running 6L6's if I wanted to. What would be the drawbacks of this configuration? I am planning to use the Hoffman layout and I know I do not need a bias tap, but it is nice to have one.
Will it still be a Princeton aa1164 with 6V6 tubes or am I moving too close to a Deluxe?
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I think the two amps are pretty close already. Except the Deluxe has two channels, a little more power, bigger speaker, and more bottom end.
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I ordered a 2-spring Mod tank from Antique Electronics about a year ago to replace a non-working tank in a blackface DR. The Mod had an insane amount of dwell, although it was a "direct" replacement for the original.... I sent it back and went wth Accutronics. Also , are you sure that a long tank won't fit in your 17" box ?
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I ordered a 2-spring Mod tank from Antique Electronics about a year ago to replace a non-working tank in a blackface DR. The Mod had an insane amount of dwell, although it was a "direct" replacement for the original.... I sent it back and went wth Accutronics. Also , are you sure that a long tank won't fit in your 17" box ?
I am thinking a long tank may fit and I have a few of them to check first, but I dont have any 3 springers and I do want to use a dwell as I have never done this in a build so I would like the learning experience. I think I will go with Slucky's recommendation since he has yet to steer me wrong.
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I think the two amps are pretty close already. Except the Deluxe has two channels, a little more power, bigger speaker, and more bottom end.
So am I to understand either PT will work.
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Yes. The DR PT is larger and will likely give a stiffer B+ rail with slightly higher voltage.
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Yes. The DR PT is larger and will likely give a stiffer B+ rail with slightly higher voltage.
I have read where if you drop the B+, you get earlier break-up and a tradeoff of headroom. It can be done with dropping resistors as well. Is the drawback a more loose bottom end? How much voltage drop does it take to make a noticeable difference in output. I ask this because of the low power tweed twin. reading schematics, I came across this one. What is the purpose?
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The low power tweed Twin had 2 output tubes for forty-something watts. The high power Twin had 4 output tubes for eighty- something watts. There probably wasn't that much difference in the B+ between the two, ( the old schematic voltages can be misleading ).
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I have noticed Princeton AA1164 has a cap can 20/20/20/20 at 475v. Is this the best way to filter. Doug only has a 40/20/20/20. I like cans, but I am wondering if it would be best to use separate filter caps. I have seen many builds where they have 4, 22uf 500v. I am planning on using a Deluxe Reverb PT. Does it really matter?
Comments welcomed.
Also, does anyone know the vac on Doug's Deluxe Reverb PT 041316, his spec page does not list the vac.
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I vote for separate filter caps on a _new_ build, put close to the stage their supplying.
Have you read Merlins web site or his book on grounding/PSU caps? KOC's TUT series has a ton of info on PSU and grounding. Doug has great grounding info in his tube amp library.
If you use more capacitance, 40uf instead of 20uf, you'll get a little better B+ filtering and a little stiffer/tighter bass. It's up to you as what you like.
Brad :icon_biggrin:
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I vote for separate filter caps on a _new_ build, put close to the stage their supplying.
Have you read Merlins web site or his book on grounding/PSU caps? KOC's TUT series has a ton of info on PSU and grounding. Doug has great grounding info in his tube amp library.
If you use more capacitance, 40uf instead of 20uf, you'll get a little better B+ filtering and a little stiffer/tighter bass. It's up to you as what you like.
Brad :icon_biggrin:
Yes, I have read this info you speak of, that is the reason for my question. So you suggest 4 caps, the first being 40uf and the other 3 being 20uf. I am interested in stiffer bass. The only reason I like cap cans is they look cool standing up and this build is going to be a cage build head, but it is not necessary. Thanks for your input.
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Hi Ed
I did a BFPR clone a while back and I used an IRF820 source follower after the LFO which drives the 6V6 bias-wiggle better. I adapted the 5G9 LFO/CF pair circuit values. I also did away with the cap can and used separate filter caps - easier to get quiet. It also has a 12" speaker and BFDR spec OT, for a slightly 'bigger' sound.
Here is a schematic. I call it the "AA1165" :l2:
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So you suggest 4 caps, the first being 40uf and the other 3 being 20uf. I am interested in stiffer bass.
Yes, I would, but I've only built a few amps. The old amps were built using what was available then. I'd bet if Leo was building amps now he would be using the _new_ small size radial electrolytic caps and not use a dog (cap) house on the outside of the chassis or multi cap can. Small size, high temp, high ripple current, low ESR, long life, low price.
KOC and Merlin, among others have nothing against can caps as long as you use them as a single cap, ie, say using a 50uF/50uF as a single 100uF cap. That way you have a single cap B+/single cap ground point.
I'm working on a tweed tremolux 5G9 (new build) and I'm going with 110uF/choke/40uf, for plate and screen B+ supply. But I'm also going with a SS rec. so I don't have to worry about in-rush current killing the rec. tube.
Again I'm talking about a new scratch build/layout. If I were going to use one of Dougs boards, I'd use the Ill. caps he used to build the amp.
Brad :icon_biggrin:
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I was using Nichicon VZ radial series. I was just told about the Panasonic ED radial series.
Nichicon VZ 22uF@450v, 105 deg.C., 115mA ripple current, 1Khr. life time, $0.85 each @25.
Panasonic ED 22uF@450v, 105 deg.C., 680mA ripple current, 10Khr. life time, $1.10 each @25.
Almost 6x the ripple current raiting and 10x the life time raiting, only $0.25 more each when you buy 25 at a time. I'm gonna try them.
Brad :icon_biggrin:
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Hi Ed
I did a BFPR clone a while back and I used an IRF820 source follower after the LFO which drives the 6V6 bias-wiggle better. I adapted the 5G9 LFO/CF pair circuit values. I also did away with the cap can and used separate filter caps - easier to get quiet. It also has a 12" speaker and BFDR spec OT, for a slightly 'bigger' sound.
Here is a schematic. I call it the "AA1165" :l2:
Thanks for the info. The 1165 looks good.
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I was using Nichicon VZ radial series. I was just told about the Panasonic ED radial series.
Nichicon VZ 22uF@450v, 105 deg.C., 115mA ripple current, 1Khr. life time, $0.85 each @25.
Panasonic ED 22uF@450v, 105 deg.C., 680mA ripple current, 10Khr. life time, $1.10 each @25.
Almost 6x the ripple current raiting and 10x the life time raiting, only $0.25 more each when you buy 25 at a time. I'm gonna try them.
Brad :icon_biggrin:
Where did you sure the Panasonic? Thats only 26 bucks.
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Where did you sure the Panasonic? That's only 26 bucks.
Mouser, I bet digi-key has them too.
I put them up on turrets, that way I can tie all the ground wires for each circuits tube stage to the turret. Eyelets might not have enough room depending on how many ground returns you have.
Here's a couple of pics. The second pic has 1 cap vert. and 1 horizontal, soldered to the same turrets.
Brad :icon_biggrin:
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Hi Ed
I did a BFPR clone a while back and I used an IRF820 source follower after the LFO which drives the 6V6 bias-wiggle better. I adapted the 5G9 LFO/CF pair circuit values. I also did away with the cap can and used separate filter caps - easier to get quiet. It also has a 12" speaker and BFDR spec OT, for a slightly 'bigger' sound.
Here is a schematic. I call it the "AA1165" :l2:
I finally found the mosfet, it took a while. Might be a little over my head, but I will review it closely and see if it sinks in. Thanks.
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Last questions for now. I need a recommendation for a Deluxe Reverb PT, reverb Transformer and Choke. I imagine the ones Doug has would be fine, but I cannot find out the vac in the secondaries. The Hybour is 370-0-50-370, 6.3v 3amp, 5v 3 amp. The secondaries seem a little high, but what do I know. I have got my hands on a Mercury FBFD-MO, new for $45, so I think I am good here.
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Where did you sure the Panasonic? That's only 26 bucks.
Mouser, I bet digi-key has them too.
I put them up on turrets, that way I can tie all the ground wires for each circuits tube stage to the turret. Eyelets might not have enough room depending on how many ground returns you have.
Here's a couple of pics. The second pic has 1 cap vert. and 1 horizontal, soldered to the same turrets.
Brad :icon_biggrin:
Thanks for the photos. On the bottom photo from left to right, the 4th and 5th filter where one is vertical and one horizontal, how is it grounded?
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On the bottom photo from left to right, the 4th and 5th filter where one is vertical and one horizontal, how is it grounded?
I took a piece of solid copper 12g house wire and bent it to where it needed to go and stuck it in the end of a turret and soldered it in/tinned it as a ground buss. I'm not sure it was worth all the work as just running a piece of 18g wire from star node to star node. :dontknow:
Brad :icon_biggrin:
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The Hammond "Fender" Deluxe Reverb PT is 330-0-330 @ 120ma. I used one in a DR build , and the specs are actually right on.
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The Hammond "Fender" Deluxe Reverb PT is 330-0-330 @ 120ma. I used one in a DR build , and the specs are actually right on.
Thanks, that is Right On. What Choke and Reverb Transformer did you uses?
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I used the Hammond choke for smaller Fenders using 6v6 ( Antique Electronics ), and the Hammond reverb driver. BUT.. I chose the Allen Deluxe Reverb upgrade output transformer... probably the best DR I've heard. I also went with a Weber California 12.
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Hi Ed
I did a BFPR clone a while back and I used an IRF820 source follower after the LFO which drives the 6V6 bias-wiggle better. I adapted the 5G9 LFO/CF pair circuit values. I also did away with the cap can and used separate filter caps - easier to get quiet. It also has a 12" speaker and BFDR spec OT, for a slightly 'bigger' sound.
Here is a schematic. I call it the "AA1165" :l2:
I finally found the mosfet, it took a while. Might be a little over my head, but I will review it closely and see if it sinks in. Thanks.
Its not difficult. In a mosfet, the drain = the plate, the gate = the grid, and the source = the cathode. The IRF820 is a 500V mosfet, so you can sub it directly for a triode stage. Everything about the source follower circuit is the same is for a cathode follower circuit, except when using an IRF820 instead of a triode, you ought to put a 100-200R resistor in series with the gate and a 12V reverse-biased zener between the source and the gate (banded end pointing to the gate). In my circuit, the IRF820 is wired as a source follower (read 'cathode follower') and except for the extra resistor and zener diode) everything else is more or less as per the 5G9 circuit values for the LFO/CF stage . Be aware that when using an IRF820, the metal terminal on top of the package is directly connected to the drain, so it is at HT voltage.