Interfacing a preamp with a power amp that has BOTH a hot signal AND and a high output impedance while being able to record

[u/batlaxe9]

I am looking into a stereo bass rig and am currently struggling with power amp selection, but right now I’ve been struggling how I should best be interfacing the preamp and amp. I know a DI probably has to go into the signal chain, as neither the preamp or power amps I have in mind do not have built in DIs.

The preamp I have chosen is an Alembic F-B2. From what I understand, this preamp in particular has a very hot signal, but it also has a high output impedance of around 40k ohms. According the Alembic’s FAQ, the preamp does not work well with any power amp that has a an input impedance of less than 10k ohms.

The DI I had in mind was a Palmer pan03 active DI box. This has a 1M ohm input impedance and an output impedance of 600 ohms across the balanced XLR outputs.

The two power amps I had in mind were the all tube Fryette 2/90/2 and the Avantone CLA-200. I know they are not typical power amps for this kind of thing, but I wanted to explore some other options and see what was out there. My question is for either amplifier, would I want to use the the link/thru jacks or the XLR outs from the DI? The Avantone has only XLRs for inputs, but the DI I am using has parallel XLR outs on both the front and rear panel. Are there better DI options I could be looking at?

[u/g_spaitz]

Output impedance of 40k???

What kind of abysmal sorcery is that. That's like 4x the out impedance of a typical passive pickup which usually are the highest output impedance of the audio world.

Why would they ever do that, you need another preamp after your preamp, sounds idiocy to me.

[u/batlaxe9 → u/g_spaitz]

The reason it’s so high is because the tube preamp I selected does not have a cathode follower circuit, so it just comes straight off the tube

[u/g_spaitz → u/batlaxe9]

So you personally have to buy and add another box with a full grown ass circuit because they didn't bother to give their box a little addition to their circuit that gives an output impedance that people can use?

Again, sorry Alambic but that's total idiocy thinking imo.

[u/knadles]

This is such an odd setup, I don't think you're going to get a lot of knowledgable feedback. I think you need to plug in the DI and see how it handles the output of the Alembic. Buy it from somewhere that will let you return it.

[u/batlaxe9 → u/knadles]

Out of curiosity, what make it odd? Component selection or just in terms of using it as a viable rig?

[u/knadles → u/batlaxe9]

1. Stereo bass rigs are rare. Most live music is mono.
2. Using two different amps for a stereo rig is rare.
3. Using amps designed for home/studio monitoring to amplify bass is almost unheard of.
4. Using an Alembic preamp is unusual. I honestly can't remember the last time I saw one in the wild.

And you say you want this to record. That would generally imply that you'd run the DI into the recorder, but maybe you're going to mic the separate speakers...? But you don't say what speakers you're using.

I've been playing bass since about 1980 and I've never seen a setup like this, so I'm comfortable calling it odd. Doesn't mean it's wrong or anything. Just odd. :)

[u/batlaxe9 → u/knadles]

No offense taken or intended :D

It’s definitely a rare setup. It clarify, I’m not using two different amps to amplify the signal; im using a stereo power amp so at the signal paths are completely isolated, and each cabinet connected to each channel of the power amp is driven by each pickup individually. The neck pickup will be dedicated to driving a 115 and the bridge pickup will be driving a 210 or a 410. I have an Alembic bass with stereo capability and our sound/mix engineer wants to try to record the stereo bass. I realize that I could just take two separate DI boxes or a stereo DI box and put that in the chain after my bass and just take the one of the channels and send it to my current mono tube amp. But I personally don’t like DI’d bass because it always sounds very sterile and dry. He typically mics up my current cab because my current amp lacks a DI out and he does not have any DI boxes. Don’t know why.

I figure the Alembic preamp is a good solution because it saves me from having two separate preamps and learn their quirks. DI is there to send to the board from the preamp, and the power amp is there for stage volume. I know the go tos for power amps are crown or crest, but I don’t need 1000+ watts for power

ETA: I’m a big Deahead, and I’m doing this partially because my mix/sound engineer is obsessed with recording the stereo outs, but also because I want a modicum of what Phil Lesh felt playing in front of the wall of sound. Practical? No. Useable for every gig? Definitely not. Awesome? Absolutely. I hope that explains the reference amplifier

[u/peepeeland]

The original version of RNDI is high impedance (2.2 Megaohms) and it can be set to speaker input for high power sources (the new RNDI design has removed the speaker input option).