scoping a mono-block amp

[wanders]

I have a set of mono-block amps which are controlled by a separate, stereo preamp. How can I increase power to the amp without running the wave form through the pre?

 

[rayma]

If you need more voltage gain (but not from a preamp), you could use an input step-up transformer.
Connect it for either x2 (+6dB) or x3 (+ 9.5dB) voltage gain.
https://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-123-flpch.pdf

If the amps can be switched to balanced operation, they will have 6dB more gain in that configuration,
if you use a balanced source.

 

[wanders]

Don't think I would want to increase the a/c input power which feeds two transformers with output to three separate power supplies: a balanced 150/150 dc supply for the front end, a 6.3 vac tube heater, and a 550 vdc B+. I'd like to see the amp without seeing the pre.

I'm wondering if an iphone might be useful; mine has a waveform app.

 

[rayma]

Are you trying to improve the sound by not using a preamp? That's easy and will work well,
just use a 10k volume control in a box (instead of the preamp). Make sure that your source
can drive a 10k load, but most can. If you just want to buy one, they are usually called
a passive preamp.

 

[wanders]

Are you trying to improve the sound by not using a preamp? That's easy and will work well,
just use a 10k volume control in a box (instead of the preamp). Make sure that your source
can drive a 10k load, but most can. If you just want to buy one, they are usually called
a passive preamp.

that's the answer. thx.

 

[rayma]

that's the answer. thx.

Here's a very good quality, inexpensive volume control for building your own passive preamp.
DACT Type 21 Stepped Attenuator / Volume Control (Hi Fi Grade) * D shape Shaft * | eBay

 

[troystg]

Thank you for the link! I bought 2...

 

[rayma]

Thank you for the link! I bought 2...

You won't regret it. Make sure that you solder each pad on both sides of the board, because I don't think the pads have plated through holes. They are available in 10k-250k values, and in either flatted, or push-on, shaft styles.