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DIY Stompboxes => Building your own stompbox => Topic started by: Esppse on July 07, 2021, 09:28:25 PM

Title: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: Esppse on July 07, 2021, 09:28:25 PM
I understand stand there may be a voltage/wattage rating required to operate it, but is there anyway to use one of these to save the weight and space in a pedal? I'm doing a 1073 pedal, 24v power in.

https://www.hammfg.com/electronics/transformers/audio/148

Super compact heh.. much lighter.

This is the original:
http://www.audiomaintenance.com/acatalog/CA-18-VTB1148_extended_info.html

I may do the same or just remove the input transformer and replace it with solid state means.


Or am I stuck with a brick of iron?  :icon_smile:
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: PRR on July 07, 2021, 10:01:31 PM
So you are thinking that Neve was careless with costs? Weight? Space?

And there's a dozen transformer models there. Which one do you like? What is the DC current allowed? And flowed in a happy 1073?
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: Esppse on July 08, 2021, 01:11:37 AM
Looking for smallest possible for a specific build, just don't want it to melt or fail.

Building one of these kits.
http://jlmaudio.com/JLMMicro1290.htm
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: anotherjim on July 08, 2021, 05:01:04 AM
If you use the small traffy, it will be like having a strong rumble filter switched in. 200Hz bass response. The big core of the original lets it go much deeper.
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: Esppse on July 08, 2021, 10:50:45 AM
Hmm, when it comes down to mixing, I always HPF my guitars rather aggressively. 200hz is a bit high though. But I think it's OK to add low end to compensate perhaps?

Would those small transformers be able to handle the power output of the circuit though?
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: anotherjim on July 09, 2021, 04:30:34 AM
What's it doing? A balanced line driver not carrying phantom power then not much power. Most small transformers used for the job are 300mW and should tolerate or ignore (if centre tap not used) an accidental phantom power.
You might find proper alternatives from Jenson or Sowter that might have smaller forms, but will cost you.
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: PRR on July 09, 2021, 03:01:48 PM
The "1073" preamp he is planning runs a class A single-ended output stage at about(??) 100mA DC idle current. (Some say 122mA.)

He has not said which of those dozen transformers he is eyeing, but none are rated over 11mA DC.

The preamp is an antique design from days when Iron was cheaper than Silicon. Another 2N3055 would allow 1/4 of the iron but 2N2055s cost real money in 1970.
Title: Re: Can the Neve 1073 Carnhill VTB1148 output transformer be smaller?
Post by: Esppse on July 09, 2021, 04:09:08 PM
I wasn't actually sure which one of those transformers I was going to pick, I was thinking an output one, with as similar turns ratio as the Carnhill.

I see the Max DC Primary current rating now, I was looking at the output rating before, so it would definitely fail if used I'm assuming.

Can you clarify what it means to use another 2n3055 for a smaller transformer?