Transformers for Komet Style Amp? JTM45 set useful? Technical differences?

[Mr. Lime]

Thinking about building (or getting preassembled) a Komet K60 I tried to contact Heyboer for the Transformers.
As they didn't responded I was looking for some alternative sources and would appreciate your opinions and experiences.

The specs of the Heyboer as far as I found are:
power: hts-8593 rh365pt ( 365-0-365n.l. @ 250-300ma; 5v@3a; 6.3v@5-6a)
output: hts-5526 1rh, 5.8k pri.
choke: hts-7750-1 10H/200ma

The K60 needs a 5V tap for the rectifier tube and has much higher plate voltages.
Since the typical Trainwreck trannies are 300-0-300V 300mA but without 5V tap for PT and 6k6 rated for 35W for OT, I was looking at the JTM45 transformers.
They are typically 345-0-345 200mA and 6k6 and I have found an interesting set from Rosamp with 345-0-345 350mA and an OT with options for 6k6 and 8k rated for 70W.

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Is the PT in your guys view alright?
It's a lying version but I guess the sheet metal for setting up should be available.

Unfortunatly I'm not aware of the technical differences of the transformers and what they are causing soundwise.
I read the vintage correct JTM45 OTs use EI 111 lams (guess that refers to a laminated-core, single-phase, low-frequency (50/60 Hz) transformer built using standard E-I shaped silicon steel laminations) while the Trainwrecks use EI 96 which might have an impact on core saturation.
Does core saturation even play a role in a Komet or are the OT specs fine for a Trainwreck/Komet style amp?

Also there is a choke in the K60, the JTM45 transformer set comes with a Radiospare chocke (guess that's 20H, 690Ohm) and I would suspect more sag and voltage drop compared to the Komet choke - this might compensate for the more stable OT?. What are your thoughts about this?

[wizardof_oz]

Funny, I also plan a Komet style amp (Concorde) and asked Heyboer for support. I didn’t get a reply either, for whatever reason, they don’t like to handle single customers (or they don’t need to…).

Since Rosamp is based in the UK, I recommend to get in touch with Michael from Modulus Amplification. He is in the UK also, but offers customization for his trannies. I’m sure he can make your set as requested.
I made some great experience with him as I used Modulus trannies in my DR504, Express and Snorkler builds.

Another option seems Inmadout (based in IT and UK), they obviously have a good reputation here at TAG. However, until now I received no reply yet to my recent request.

[M Fowler]

I will send you two guys info regarding Asteroid/k60 build. The Constellation is different and has tube recto.

Mark

[Mr. Lime]

Thanks for your replies!

Well in the meantime I got myself a Ceriatone Expression second hand and experimented a litte.
I replaced the parts to basically have a K60 but with the 6K6 OT and 300-0-300 PT.
The cool thing about the Ceriatoe OT is that it can be wired for 5k as well which would be between K60 and K50 but still the B+ is way too low.

Not sure if it pays off to replace the PT.

I'm currently planning an amp with a JTM45 chassis and layout but with a preamp based on the GP-1000 preamp but with the tonestack placed between the 3rd and 4th stage, similar to a Park Rockhead.
One stage can be switched away and with bass and treble at minimum and mids maxed, the topology is very close to a Concorde - but the EQ might be more useful.

I already got a tranny set from Piemme Elektra from Italy. A Radiospare style 6k6/8k OT with UL taps and a 345-50-0-345V PT 250mA, which should fit nicely in the chassis I'm going to buy.
GZ34 / diode rectifier switch will be included as it is wired so easy into the JTM layout.