Upcoming Bluesmaster build - some questions...

[ODwan]

Hi all,

I'm just getting my heads together for a 50w Bluesmaster build and have some questions I hope somebody in the know can answer me:
- is the Treble pot really log taper? Wouldn't a linear taper be more even in response? When I hack the Bluesmaster values in the Tonestack calculator I find the treble quite subdued in the 12 o'clock position. Well easy enough to try for myself but maybe someone has been down that road before...?
- what OT iron is recommended? Marshall or Fender - Style? Being Europebased, I can't get easily get my hands on MC, Heyboer or Classictone iron. MM is out of the question: way too expensive! General replacement iron or Hammonds are available though. I also have a great 50w Plexi OT made by german boutique winder Shinrock (out of production ) left.

Whatya think?

Grettings,

Timo

[Synchu]

Hi Timo,
You're looking at an exciting build.
-Treble pot is indeed 250kA, but 2-35 taper. I think CTS made or still makes 30% taper audio pots, but you can certainly test with linear.

- for transformers - I used in a couple of builds http://www.inmadout.com/ transformers - excellent quality and servicea and spot on specifications performance! In a Small Special build, I used these http://www.trm-audio.si/omr_transf.htm - again excellent quality and great sounding ones (they have Output transformers as well). The website is in Slovenian, so the first time I got there, I used Google translator just to find the e-mail

Looking forward to your progress,
Niki

[jestaudio]

The Inmadout Traffos are great for the money and I cannot knock the service in the least,

[ODwan]

Thanx so far,
I wonder if the Tube-Town.de branded iron are made by inmadout...
They look similar...
I think I'll go with Marshall style OT unless someone recommends Fender. I think a Marshall OT should match the Bluesmaster PI.

Another qestion: are there any gutshots of original Dumble Bluesmaster amps available? I didn't find any so far.

Greetings,
Timo

[Synchu]

I don't know who makes the transformers for tube-town :/

Now, Marshall style OT transformers from various manufacturers that I've seen are all over the place with the specs. It should be good to go generally, though. Do you know the specs of yours?

I haven't seen (or searched for) Bluesmaster photos :/ I am sure you're aware of it, but there's a great layout made by talbany, pinned right at Dumble files section.
Niki

[ODwan]

My 50w Shinrock has 3500 Ohms primary impedance and is a clone of a '68 Drake OT, AFAIK.
I'm mainly asking Marshall or Fender, because I couldn't find info on what the original used.
It isn't noted on Talbany's great layout, or have I missed something?

Timo

[marcos]

Hi Timo,
HAD recommended a linear 250K pot as Treble control, although he did use
both linear and 30% taper pots in his amps AFAIK. Since the linear
type is easier to get I would go that way.
Hope this is helpful

Marcos

[Synchu]

Hi Timo,
OT isn't noted. Searching through the discussions, I think it is not known from the available information.
In any case albeit 3500 is a bit low for 6L6GC (>4K being the "normal") it will obviously work for EL34 and shouldn't be too much trouble for 6L6, KT66 when biased properly, so I would go with it.
Niki

[ODwan]

Thanx for your input!
If anyone's interested: my experience with various primary impedances and tubes is this:
generally higher imp makes the poweramp more dynamic to a degree.
Different tube types have different optima, as far as max power output before clipping is concerned.
This is what I found (for one pp-pair):
EL34: max power around 3400 ohm, gets more dynamic up to around 7000 ohm, but max power is reduced somewatt
6L6: max power around 4400 ohms. I really liked the dynamics with a 5400 ohms OT. Max power was only slightly reduced. with a 3400 ohms OT I achieved 10% less output.
KT66: Max power at and above 7400 ohms. Best sound and dynamics at 8800 ohms ( JTM45 value). Sounds liveless and shitty below 5000 ohms
Didn't test other tubes that way.
Ymmv! That's just what I have found. My tests where done with a multiprimary OT of unknown origin. It had primary taps with 2800, 3400,4400, 5400, 6800 , 8800 and 10.000 ohms. Really cool plaything! Sadly I fried it eventually along with a PT and a pair of KT88s D'oh!!!

Anyway, as I wanna use 6L6s / 5881s I think I'll go with a SLO 4400 ohms OT I just got cheap!

Greetings,

Timo