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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Finest Chokes, Power, and Output Transformers

88man

Member
2009-08-09 4:55 pm
Boston
Greetings! What are the finest power transformers, chokes, and SE output transformers money can buy? I’m looking for wide bandwidth, and low noise.

I’ve had all the parts for the Derek Walton 300B SE Amp for 10yrs. However, I never got around to ordering the trannies. Plitron is no longer available. What are the best brands

T1: Pri: 115VAC. Sec: 380VAC CT, 6.3VAC CT, 5.0VAC CT.
T2: Pri: 3.0k Ohm. Sec: 8, 4 Ohm
Choke 1: 20H, 400mA, Toroid
Choke 2: 10H, 50mA, Toroid

Questions:
1. I can’t find a 20H, 400mA choke. Will a Toroidy 20H, 200mA choke work instead?
2. I can’t find a 10H, 50mA choke. Will a Toroidy 10H, 250mA choke work instead?

Thanks!
 
I think the Walton 300B is not a design that you would use the very best/most expensive iron for. You can get insanely expensive transformers if you want.



As you are in the USA, you should consider getting in touch with Electra-Print.com High-Fidelity Audio Tranformers and Tube Amplifers

He makes nice iron.

But why would you need 400mA choke in a 300B design?

And why should the 6.3V and 5.0V be center tapped?

Edcor has your pwr trf, but not CT filament. EDCOR - XPWR033
 

88man

Member
2009-08-09 4:55 pm
Boston
Thank you Toriversen, aardvarkash10, and Nightpuma! Derek Walton’s version used a Plitron 20H, 400mA choke. Can I get by with a 20H, 200mA choke?...

I believe the power and filament transformers were Sowter.
Edcor XPWR033 looks great! Who makes a toroid version for low hum/noise?...
 
Thank you Toriversen, aardvarkash10, and Nightpuma! Derek Walton’s version used a Plitron 20H, 400mA choke. Can I get by with a 20H, 200mA choke?...

I believe the power and filament transformers were Sowter.
Edcor XPWR033 looks great! Who makes a toroid version for low hum/noise?...

The chokes don´t have to be a toroid design. You can get off the shelf chokes from Hammond or another manufacturer.

If you have the schematic for the amplifier and power supply, it will be easier to help you.
 

analog_sa

Member
Paid Member
2002-08-14 1:47 pm
Cascais
You can get off the shelf chokes from Hammond or another manufacturer.


This thread has an ambitious title but then it rappidly goes downhill into mass market mediocrity.

Chokes make a dramatic difference to perceived sound in my system. Layered design is vital and so is core material. Standard Lundahl chokes are the absolute minimum. Permalloy, amorhous or nano cores are all personal preferences and it's hard to take a decision without a first hand experience.
 

88man

Member
2009-08-09 4:55 pm
Boston
You say you want the best, then say you want to cut corners.

Plitron no longer makes audio transformers. I just want premium toroid iron regardless of price. I have had all the parts (less the transformers), but I’ve been away from DIY tubes for 12 years. Time to complete the project.

I don’t know who makes a 20H, 200mA choke. My question is what does the circuit warrant. I’ll post a photo of the schematic soon...
 
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88man

Member
2009-08-09 4:55 pm
Boston
Here’s the schematic and power supply for the 300B MkII.

I just don’t know where to find premium transformers. I’ll look into Tango and Lundahl as suggested. Again, I’m not looking to cut corners, it’s all about what’s available regardless of price!

Question: Since I can’t find premium Plitron transformers, can I “substitute” a Toroidy 18H, 250mA choke?
 

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scholl

Member
2012-12-30 5:07 pm
Here’s the schematic and power supply for the 300B MkII.

I just don’t know where to find premium transformers. I’ll look into Tango and Lundahl as suggested. Again, I’m not looking to cut corners, it’s all about what’s available regardless of price!

Question: Since I can’t find premium Plitron transformers, can I “substitute” a Toroidy 18H, 250mA choke?

Is Magnaquest still around?
 

Francois G

Member
Paid Member
2004-06-16 8:36 pm
Illinois
Here’s the schematic and power supply for the 300B MkII.

I just don’t know where to find premium transformers. I’ll look into Tango and Lundahl as suggested. Again, I’m not looking to cut corners, it’s all about what’s available regardless of price!

Question: Since I can’t find premium Plitron transformers, can I “substitute” a Toroidy 18H, 250mA choke?

Thank you for posting the schematic. Sorry about some of the responders sounding harsh. I can provide some information, hopefully helpful.

1. Menno van der Veen, the designer of the PAT 3035 SE transformer, still sells them from his Bureau in the Netherlands. See:
Single-Ended : VDV-3035-SE (PAT-3035-SE)

2. Electra-Print does very good work. The aforementioned amorphous core transformers (Lundahl, ISO/Tango, Tribute and others) will probably exceed the performance of the PAT3035, if money is no object. Silver coils?

3. A 250 ma choke will be close, and I would look for a 300ma, or separate the supply for each channel. Each 300B will be limited by the current it could safely pass (<100 ma, at your supply voltage), plus some for the front-end (allow 40 ma). So, 240 ma is likely to be the minimum I will want to use.

4. A previous post stated that the Walton 300B design might not justify the use of very best in transformers. I do not have an opinion, but it is something to contemplate. You have the “inexpensive parts” for the Walton design, but you real investment would be in the magnetics, so why not look around for a top design.

Best wishes with your return to tube amp building, and report your progress here.
 
Very nice you got some good help.

You can get the output transformers fra Menn VDV as Francois says, and the power transformer you have at Edcor or have one made.

You should calculate how much power the entire amp draws, and get the 20H choke you need. 400mA is overkill. The rectifier can not deliver more than 250mA anyway, so probably 200mA would be enough, but best you make the math.
The 10H for the 6sn7 tubes could also be lower than 150 mA.

Another thing is that it seems that the output tubes is AC heated. You will probably have some hum, so you should make room in the cabinet for future conversion to DC heating.
 

invaderzim

Member
2015-10-07 4:07 am
Monolith makes very fine iron, indeed. My 833C amps have 60lb outputs and high-voltage chokes from Monolith and sound very good indeed.

Attached are a couple shots sent from Monolith as they were building the OPTs, and a shot of one completed mono amp.
 

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I would wonder about Electra-print as well, as I've heard from three different people now that Jack is deceased.

This is the first I have heard of it, but Google finds this:

Jack Elliano Obituary - Las Vegas, NV | Las Vegas Review-Journal


400mA is overkill. The rectifier can not deliver more than 250mA

The first stage eats 3.5 mA. The second stage eats 5 mA. A 300B should not be run much harder than 100 mA. so 110 mA per channel should do fine. A TRUE 250 mA choke should be good. As would the bigger 3,000 ohm Toroidy OPT's. I am currently stuffing 30+ watts through the big 1.5 K ohm Toroidys and they sound pretty nice. There is some saturation in the low bass, but you aren't going to get 30 watts from a 300B.

The 10H for the 6sn7 tubes could also be lower than 150 mA.

Total draw is under 20 mA. a 50 to 100 mA choke would be fine.
 
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