Feel free to ask Myles

[myles_rose]

Hey Myles, about the Twin Reverb again. I emailed all the tube dealers on your site with your specs you mentioned to see if they can measure each of them.

 

In the meantime, I was looking up stuff about my amp and I saw something that said it has a fixed bias? What exactly does that mean and does that change the type of output tube you recommended? If my amp is "fixed bias" can you bias the tube to 32mA per tube like you said?

 

 

Your amp is a grid biased amp also called fixed bias as there is a constant voltage on the grid (pin 5) of about -52 volts. A cathode biased amp's bias self adjusts and changes.

 

Your "fixed" bias amp has an adjustable pot to change the fixed voltage output. Some amps such as Mesa Boogie amps do not have an adjustable bias pot so tubes within a narrower range are required. Actually though, the Mesa method is sort of cool as the bias cannot be set improperly and the amps require tubes that are very close to the tube design spec. Bias pots are nice when you are forced to use tubes that do not come close to the design spec of the tube which is not really a great idea as there is something basically wrong with those tubes.

 

Mesa does very good matching on their tubes as a side note.

 

 

[mhuxtable]

Dude you respond freaking fast.

 

Yeah I have gotten a couple of responses and they are interesting. Either "We dont measure all those specs" or "yeah we measure them but if youre that specific then its gonna cost you lots extra" (like Im a freak for getting that specific). Id rather pay extra to know Im getting your expertise in my amp. Thats why I trust you, youre not afraid to deal with the details.

 

So I think some NOS are going into the preamp and the GT 6L6s for the output cos I just cant afford NOS in the outputs. If I get a GT 6L6 at a #7 will that mean I get one with the 72mA you recommended?

[myles_rose]

Dude you respond freaking fast.

 

Yeah I have gotten a couple of responses and they are interesting. Either "We dont measure all those specs" or "yeah we measure them but if youre that specific then its gonna cost you lots extra" (like Im a freak for getting that specific). Id rather pay extra to know Im getting your expertise in my amp. Thats why I trust you, youre not afraid to deal with the details.

 

So I think some NOS are going into the preamp and the GT 6L6s for the output cos I just cant afford NOS in the outputs. If I get a GT 6L6 at a #7 will that mean I get one with the 72mA you recommended?

 

Don't go the GT route .... the new GT/Fender is something I no longer trust.

 

Go to either www.kcanostubes.com or www.dougstubes.com and get some good winged C real Svetlanas as tell either Mike at KCA or Doug at Doug's Tubes that you want a middle range spec tube and tell either one of the hello from me.

 

[mhuxtable]

Dude you respond freaking fast.

 

Yeah I have gotten a couple of responses and they are interesting. Either "We dont measure all those specs" or "yeah we measure them but if youre that specific then its gonna cost you lots extra" (like Im a freak for getting that specific). Id rather pay extra to know Im getting your expertise in my amp. Thats why I trust you, youre not afraid to deal with the details.

 

So I think some NOS are going into the preamp and the GT 6L6s for the output cos I just cant afford NOS in the outputs. If I get a GT 6L6 at a #7 will that mean I get one with the 72mA you recommended?

 

Don't go the GT route .... the new GT/Fender is something I no longer trust.

 

Go to either www.kcanostubes.com or www.dougstubes.com and get some good winged C real Svetlanas as tell either Mike at KCA or Doug at Doug's Tubes that you want a middle range spec tube and tell either one of the hello from me.

 

Those are actually the 2 people I've been emailing back and forth with. Doug said he cannot/willnot measure all the preamp tube specs you recommended, Mike can/will (although he seems to be annoyed I've asked that much).

 

I will ask Doug about those output tubes.

[myles_rose]

Dude you respond freaking fast.

 

Yeah I have gotten a couple of responses and they are interesting. Either "We dont measure all those specs" or "yeah we measure them but if youre that specific then its gonna cost you lots extra" (like Im a freak for getting that specific). Id rather pay extra to know Im getting your expertise in my amp. Thats why I trust you, youre not afraid to deal with the details.

 

So I think some NOS are going into the preamp and the GT 6L6s for the output cos I just cant afford NOS in the outputs. If I get a GT 6L6 at a #7 will that mean I get one with the 72mA you recommended?

 

Don't go the GT route .... the new GT/Fender is something I no longer trust.

 

Go to either www.kcanostubes.com or www.dougstubes.com and get some good winged C real Svetlanas as tell either Mike at KCA or Doug at Doug's Tubes that you want a middle range spec tube and tell either one of the hello from me.

 

Those are actually the 2 people I've been emailing back and forth with. Doug said he cannot/willnot measure all the preamp tube specs you recommended, Mike can/will (although he seems to be annoyed I've asked that much).

 

I will ask Doug about those output tubes.

 

I would let either of those two guys just do what they do as they do it well. The reason I collect a lot of data is to be able to go back to tube makers and help with their QA or get very specfic for certain clients during the blueprinting process.

 

 

[mhuxtable]

Yeah I know they are total experts, but I do appreciate the extra mile you go and I am a very details oriented person. If a few more steps make a difference it getting an amazing tone, why not do them you know?

 

Yeah I think I'm gonna get my output tubes from Doug and my preamp tubes from Mike even though he seemed a little off putting (he said in 20,000 orders he has never had anyone that specific about preamp tubes). Once I get back from the beach this weekend I am gonna put in my orders and once I get the tubes have my tech guy bias the outputs for me.

 

Myles you are awesome, thank you for all your help and your patience. I will let you know how everything sounds once it is all in.

[myles_rose]

Yeah I know they are total experts, but I do appreciate the extra mile you go and I am a very details oriented person. If a few more steps make a difference it getting an amazing tone, why not do them you know?

 

Yeah I think I'm gonna get my output tubes from Doug and my preamp tubes from Mike even though he seemed a little off putting (he said in 20,000 orders he has never had anyone that specific about preamp tubes). Once I get back from the beach this weekend I am gonna put in my orders and once I get the tubes have my tech guy bias the outputs for me.

 

Myles you are awesome, thank you for all your help and your patience. I will let you know how everything sounds once it is all in.

 

 

There are two main reasons Doug and Mike do not do what I do .... one is that the equipment needed is very costly and time consuming to operate .... the cost of a selected preamp tube would be close to $50 to spec and trace. The other reason is that you don't select tubes this way for the end user, you select it for fine tuning or to duplicate the tone in an amp that you loved but had a failure and want as close to an exact replacement as possible as the original tube would have been documented by me originally.

 

In essence ... you ask either of these two guys for a great BMW M3 as an example. The sell you one, a good stock one.

 

If you come to me I find a specific M3 after you and I go through 50 of them. I then set up the suspension, tires, engine, shift points etc. for specifically you and your style of driving, the given track, your weight etc.

[BCorbett]

Hey Myles,

 

I am working on a adding a Tweed channel as explained on page 152-153 of The Tube Amp Book, to a 1981 Deluxe Reverb. I noticed you are the technical cosultant for this book so I hope you can help me.

 

This era of "Blackface" has the pull boost on the reverb channel. My amp does not have point X in the diagram, the treble capacitor is closer to the tubes instead of the middle of the board. Of course I wanted to add reverb to both channels and it looks like in doing so I need to pull the treble cap back any way, but I have not figured out where to put the wire to get sound from point D on the AB763 Layout, to point Z. Can you explain how to make this all work or where I can find the info, pictures are helpful.

 

Thanks, Brendan

[myles_rose]

Hey Myles,

 

I am working on a adding a Tweed channel as explained on page 152-153 of The Tube Amp Book, to a 1981 Deluxe Reverb. I noticed you are the technical cosultant for this book so I hope you can help me.

 

This era of "Blackface" has the pull boost on the reverb channel. My amp does not have point X in the diagram, the treble capacitor is closer to the tubes instead of the middle of the board. Of course I wanted to add reverb to both channels and it looks like in doing so I need to pull the treble cap back any way, but I have not figured out where to put the wire to get sound from point D on the AB763 Layout, to point Z. Can you explain how to make this all work or where I can find the info, pictures are helpful.

 

Thanks, Brendan

 

Look on the first page of my GAB website and find Dave Hunter's book ... get that book. Much better than the Tube Amp Book.

 

 

[A String]

Hey Myles!

 

Ok, I finally got that Traynor YSR-1 Custom Reverb. I think it's a 1967?

 

Anyways... It has two channels. When I plug into the first channel, the sound is full and rich, but there is a problem with the volume. From 0-1, there is no sound. From 1-9, the sound is there, but doesn't change as you turn the dial (ie. it stays at the same volume of what I would expect to get at around 2 or 3 on the dial, all the way around). From 9-10, the volume jumps up, but is still fairly quiet.

 

On the second channel, it's volume works fine, but the channel sounds thin, tiny and weak, even when it's cranked up.

 

Any ideas?

[myles_rose]

Hey Myles!

 

Ok, I finally got that Traynor YSR-1 Custom Reverb. I think it's a 1967?

 

Anyways... It has two channels. When I plug into the first channel, the sound is full and rich, but there is a problem with the volume. From 0-1, there is no sound. From 1-9, the sound is there, but doesn't change as you turn the dial (ie. it stays at the same volume of what I would expect to get at around 2 or 3 on the dial, all the way around). From 9-10, the volume jumps up, but is still fairly quiet.

 

On the second channel, it's volume works fine, but the channel sounds thin, tiny and weak, even when it's cranked up.

 

Any ideas?

 

It sounds as if the pot is bad or has been replaced at some point and is of the wrong value and or taper.

 

 

[A String]

Ok, I'll see what I can do about that.

 

I notice the power tube says 6CA7. Is that the best one to use in this amp?

[myles_rose]

Ok, I'll see what I can do about that.

 

I notice the power tube says 6CA7. Is that the best one to use in this amp?

 

 

6CA7 is the USA designation for some EL34 types. You may use any EL34.

 

 

[BCorbett]

Hey Myles,

 

I went back and read Dave Hunter's book. It was his book that mentioned the tweed mod in Aspen's book.

 

It was helpful and I thought I had it all figured out but once both channels were hooked to the reverb and vibrato, all I got was a loud hum weather a guitar was plugged in or not and no sound from a guitar. Does this sound like a ground issue ? The ground for the potentiometers I soldered onto an existing spot because it would not stick any where else.

 

Brendan

[myles_rose]

Hey Myles,

 

I went back and read Dave Hunter's book. It was his book that mentioned the tweed mod in Aspen's book.

 

It was helpful and I thought I had it all figured out but once both channels were hooked to the reverb and vibrato, all I got was a loud hum weather a guitar was plugged in or not and no sound from a guitar. Does this sound like a ground issue ? The ground for the potentiometers I soldered onto an existing spot because it would not stick any where else.

 

Brendan

 

It could be a number of things. I would need to see the amp on a bench.

 

 

[RocketRick]

Myles,

 

Can one take some of the tubes out of say a Marshall JCM 800 100 watt amp and make it do 50 watts w/o messing things up?

 

Thanks

 

Rick

 

 

[myles_rose]

Myles,

 

Can one take some of the tubes out of say a Marshall JCM 800 100 watt amp and make it do 50 watts w/o messing things up?

 

Thanks

 

Rick

 

 

Yes, you can do this safely but I think it sounds pretty bad compared to an amp that has 50 watts worth of tubes fed by a 50 watt power transformer rather than 50 watts worth of tubes fed by a 100 watt power transformer.

 

Lots of info on this on my GAB website in the 50 watts vs 100 watts area.

 

But yes ... pull either the two inner or two outer tubes (not the two left or two right) and with a 16 ohm cab set the speaker selector to 8 ohms. With an 8 ohm cab set to 4 ohms.

 

 

[picker]

Hey Myles,

I saw this amp on ebay last night, and it made me curious.

As you can see in the listing, it uses 2-ECL86 & 1-EZ8 tubes. Are those tubes still available anywhere? I know a lot of previously common tubes are not being made anymore. If not, would there be a way to modify an amp like that to use more readily available tubes? Would that be prohibitively expensive?

[myles_rose]

Hey Myles,

I saw this amp on ebay last night, and it made me curious.

As you can see in the listing, it uses 2-ECL86 & 1-EZ8 tubes. Are those tubes still available anywhere? I know a lot of previously common tubes are not being made anymore. If not, would there be a way to modify an amp like that to use more readily available tubes? Would that be prohibitively expensive?

 

The ECL86 is half pentode and half triode. Marshall actually used them in one of their smaller amps as did a few more folks.

 

No problem-o finding them ... also used in some hifi stuff. Lots still out there at about $30, the same range as a good preamp tube but unlike new made preamp tubes these ECL86s will last decades.

 

The EZ8 that you mention is really a typo... it is an EZ81 and is the rectifier. Lots of NOS versions of these but new ones too. They look a lot like an EL84, same size bottle. Used in Vox AC-15s and the smaller Vox amps, the 18 watt Marshalls and in a lot of high end amps from top builders these days. About $15 or less.

 

The ECL86s can be found at www.tubesandmore.com (Antique Electric Supply) as one source but there are others. The EZ81 can be found there too but also at even more places.

 

These small Hammond amps were very cool. One version of a Hammond evolved into the Dr. Z Carmen Ghia which is one of the coolest blues and rock amps of all time. The first versions of the Ghia used the original Hammond chassis placed in a cool head enclosure.

 

I would not mod the amp .... they are very cool as they are and with a spare set of ECL86s as backup (which will probably never be needed) you would probably find your grandkids playing the amp someday on the tubes you plug in.

 

 

 

 

[WaterMan]

Hey Myles,

 

I have a 65 Amps London, Fargen Blackbird, and Victoria Regal II. These are all great amps for the obvious reasons, but I'm feeling incomplete without a clean sounding 6L6 Fender with ample headroom. Which 6L6 Fender would you recommend these days for this purpose and to complement my collection?

 

Thanks!

[myles_rose]

Hey Myles,

 

I have a 65 Amps London, Fargen Blackbird, and Victoria Regal II. These are all great amps for the obvious reasons, but I'm feeling incomplete without a clean sounding 6L6 Fender with ample headroom. Which 6L6 Fender would you recommend these days for this purpose and to complement my collection?

 

Thanks!

 

This is easy. If I had the lineup you had I'd contact David Hayes at http://www.hayesamplification.com/index.htm and have him build you a 50 watt or so (2x6L6) amp such as a Pro Reverb or Vibroverb or Super Reverb.

 

 

[WaterMan]

OK, will do. I haven't been to your website in a while and Hayes looks like a new addition. Just out of curiosity, any particular reason you recommend him over Fender (or other clones)? Was kinda of thinking I should have a Fender (for no particular reason other than I don't have one), but I'm always open.

 

Thanks Myles.

[myles_rose]

OK, will do. I haven't been to your website in a while and Hayes looks like a new addition. Just out of curiosity, any particular reason you recommend him over Fender (or other clones)? Was kinda of thinking I should have a Fender (for no particular reason other than I don't have one), but I'm always open.

 

Thanks Myles.

 

I first came across his work when one of my clients in a band called The Moxie Blues Band was using one of his BF 15" Vibroverb custom builds. Weber 15" speaker, Mercury Magnetics, proper caps, amazing workmanship just top notch. The best build quality I had seen in the Fender builder type folks. Over a year or two I came across other examples and all were right there with what I first saw. I then saw some of his restoration work and it was pretty spectacular as well.

 

David has a simple lifestyle and his expenses for life in general are low and he is a one man shop and that translates into very low prices for what you get. His customer service and assistance are also top notch because he cares and takes a lot of pride in what he does.

 

He also has some of his own designs based on Fender tolex era amps that do not stray too far from the original concepts and design foundations and those are great too.

 

I guess the bottom line for me is ... if I wanted a Fender tolex era amp he would be the guy I would call for my own amp.

 

 

[desertdweller]

Hi - I have a Silvertone 1431 (same as an Airline GDR-8502A on P 145 in Jack Darr's book) It has a variable capacitor between the screen grid of the 6AU6 preamp tube and the output transformer.

What is the function of this?

Thanks!

[myles_rose]

Hi - I have a Silvertone 1431 (same as an Airline GDR-8502A on P 145 in Jack Darr's book) It has a variable capacitor between the screen grid of the 6AU6 preamp tube and the output transformer.

What is the function of this?

Thanks!

 

I do not know ... I will have to look at a print and see how it is implemented.

 

 

[desertdweller]

http://www.ampix.org/albums/bargainbin/airline_wards_gdr-8502a.pdf

 

This is a link to a pdf of the schematic (if it helps)

thanks gain!

[myles_rose]

http://www.ampix.org/albums/bargainbin/airline_wards_gdr-8502a.pdf

 

This is a link to a pdf of the schematic (if it helps)

thanks gain!

 

Looks to be neg feedback. Which component on the print are you questioning?

 

 

[desertdweller]

The variable capacitor between the 6AU6 and the OT. I was wondering what it does?

http://www.ampix.org/albums/bargainbin/airline_wards_gdr-8502a.pdf

[myles_rose]

The variable capacitor between the 6AU6 and the OT. I was wondering what it does?

http://www.ampix.org/albums/bargainbin/airline_wards_gdr-8502a.pdf

 

Unless I am blind I do not see a variable cap.

 

What is the component code (as in C12 next ro R14 or whatever)

[desertdweller]

It is C6, you see it just below the output transformer